'

i

.- -

■

■

M ■ i

i:

'1 X 'A

F

•

f •'• *

;

H^k ' ¥9

/:-.

'1

f'M

||

1 1

Ifj

V I 1

'

."

. §:;

jjBjM

t:

i

„

J3PR

- . .....

THE JOURNAL

OF THE

(Qucktt

Microscopical Club.

EDITED BY FRANK P. SMITH.

SECOND SERIES.

VOLUME IX.

1904-1906.

MARINE

L

W. H. 0 I.

.»»»'-»«..

*!77777!***%

pontoon : [Published for the Club]

WILLIAMS AND NORGATE,

14, Henrietta Street, Coyext Gardex, Loxdox, axd 7, Broad Street, Oxford.

PRINTED BY

HAZELL, WATSON AND V1NEY, LD.,

LONDON AND AYLESBURY.

111

CONTENTS.

PART No. 54, APRIL 1904. Papers.

PAGE

F. J. Cheshire, F.R.M.S. Abbe's Test of Aplanatism, and a Simple

Apertorneter derived therefrom (Illustrated) 1

F. P, Smith. The Spiders of the Sub-family Erigoninae (Plate 1) . 9 J. Rheixberg, F.R.M.S. An Overlooked Point concerning the Re- solving Power of the Microscope (Illustrated) .... 21

D. J. Scourfield, F.R.M.S. Synopsis of the Known Species of British Fresh-water Entomostraca. Part III. Ostracoda, Phyllo- poda, and Branchiura (Plate 2) ....... 29

C. F. Rousselet, F.R.M.S. On a New Fresh-water Tolyzoon from

Rhodesia, LophopodeUa thomasi, gen. et sp. nov. (Plate 3) . .45

G. Massee, F.L.S. President's Address. Some riant Diseases caused

by Fungi 57

V. Vavra, Ph.D. On the Phyllopods Limnadia lenticularia (L.) and LimnetU brachyura (O.F.M.). and their Occurrence in Bohemia (Plate 1) 63

Notes.

W. J. Wood, F.R.M.S. Note on Ebonising Laboratory Tables . . 67 Rev. H. A. Soames, M.A., F.R.M.S. Note on the Sertulariidae of

Kent and Sussex 69

Proceedings, etc.

Proceedings from October 16th, 1903, to February 19th, 1904, inclusive 71

Thirty-eighth Annual Report (for 1903) 75

Report of the Treasurer (for 1903) 80

PART No. 55, NOVEMBER 1904.

Papers.

T. B. Rosseter, F.R.M.S. The Genital Organs of Taenia sinuosa

(Plate 5) 81

W. Wesche, F.R.M.S. Some New Sense-organs in Diptera (Plates 6, 7) 91 C. D. SOAR, F.R.M.S. Two New British Water-mites (Illustrated) . 105 F. P. Smith. The Spiders of the Erigone Group . . . .109

iv CONTENTS.

Note. PAGe

T. G. Kingsford. Note on a New Method of constructing Small

Glass Tanks (Illustrated) 117

Proceedings, etc.

Proceedings from March 18th to June 17th, 1904, inclusive (Plate 8) . 121

Obituary Notices 127

List of Members i-xxv

PART No. 56, APRIL 1905. Papers.

D. J. Scourfield, F.R.M.S. Fresh-water Biological Stations . . 129 C. F. Rousselet, F.R.M.S. A Description of the Rousselet Com-

pressorium (Illustrated) 137

E. J. Spitta, F.R.A.S., F.R.M.S. President's Address. The Im-

provements in Modern Objectives for the Microscope popularly

explained (Plates 9 and 10) 141

J. Rmeinberg, F.R.M.S. On the Collected Tapers of Abbe, and

Microscope Theory in Germany 153

Notes.

A. A. C. Eliot Merlin, F.R.M.S. Supplementary Note on the Foot

of the House-fly (Illustrated) . 1G7

A. A. C. Eliot Merlin, F.R.M.S. Note on a Modification of the

Rousselet Live-box (Illustrated) 1G9

A. A. C. Eliot Merlin, F.R.M.S. Note on the Cut Suctorial Tubes of the Drone-fly's Proboscis as a Suggested Text-object for Medium Powers . . . . . . . . . .171

J. Rheinberg, F.R.M.S. Note on Experimental Proof that the Doubling of Lines in the Abbe Experiments is not due to the Diaphragms above the Objective (Illustrated) . . . .173

Proceedings, etc.

Proceedings from October 21st, 1904, to February 17th, 1905, inclusive 175

Obituary Notice 180

Thirty-ninth Annual Report (for 1901) 181

Report of the Treasurer (for 1904) 186

PART No. 57, NOVEMBER 1905. Papers.

A. Earland. The Foraminifera of the Shore-sand at Bognor, Sussex

(Plates 11—14) 187

W. W'ksche, F.R.M.S. The Genitalia of the Tsetse Fly, Glossina

jxilpalu (Plate 15) 233

F.P.SMITH. The Spiders of the Walcltenaerla Group . . . 239

P. P. Smith. Anglia hancockii, a Spider New to Science (Plate 1G) . 247

Notices of Books 251

CONTEXTS.

Proceedings, etc. page

Proceedings from March 17th to June lGth, 1905, inclusive . . 253 Obituary Notice 258

PART No. 58, APRIL 190G.

Papers.

J. Murray. On a New Bdelloid Rotifer Callidina vesieularis

(Plate 18) 259

E. J. Spitta, F.R.M.S., F.R.A.S. On Some Experiments relating to

the Compound Eyes of Insects 263

T. B. Rosseter, F.R.M.S. On Drepanidotaenia undulata (Krabbe)

(Plate 19) 269

T. B. Rosseter, F.R.M.S. On a New Tapeworm, Drepanidotaenia

mijitta (Plate 20) 275

E. J. Spitta, F.R.M.S., F.R.A.S. President's Address. The Relative

Merits of the Long- and Short-tube Microscopes .... 279 W. P. Dollman, F.R.M.S. A Simple Method of producing Stereo- photo-micrographs (Plate 21) 287

H. Taverner, F.R.M.S. A Simple Method of taking Stereo-photo- micrographs and mounting the Prints without cutting (Plates 22 — 24) 291

F. P. Smith. The Spiders of the Diploeephalus Group . . . 295 F. P. Smith. The Literature of the Sub-family Erigoninae. . . 321

Note. J. M. Coon. Note on a New Finder for the Microscope . . . 327

Notices op Books, etc 331

Proceedings, etc.

Proceedings from October 20th, 1905, to February 16th, 1906, inclusive 333

Obituary Notice (Plate 25) 349

Fortieth Annual Report (for 1905) 351

Report of the Treasurer (for 1905) 358

PART No. 59, NOVEMBER 1906.

Papers.

C. D. Soar, F.R.M.S. Notes and Observations on the Life-history of

Fresh-water Mites (Plates 26—30) 359

J. Rheinberg, F.R.M.S. On Stereoscopic Effect and a Suggested

Improvement in Binocular Microscopes (Illustrated) . . . 371

D. J. Scourfield, F.R.M.S. Mendelism and Microscopy . . . 395 A. E. Hilton. On the Study of the Mycetozoa 423

vi contents.

Notes. page

A. K. Smith. Xote on Stereo-photo-micrography (Plates 31— 33) . 429 C. F. Rousselet, F.B. M.S. Note on Tetramastix opoliemis (Zacharias)

(Plate 34) 431

Notices of Books 433

Proceedings, etc.

Proceedings from March lGth to June loth, 1906, inclusive . . 437

Index to Volume IX 445

List of Members i-xxviii

Vll

LIST OF ILLUSTRATIONS.

PLATES.

1. Cephalo-thoraces of Male Erigoninae.

2. Belisarius viguieri and Cyclops nanus.

3. Lophopodella tho/nasi, n. sp.

4. Limnadia lentieularis.

5. Genital organs of Taenia sinuusa.

6. Sense-organs of Insects.

7. Olfactory Organs of Diptera.

8. The " Eye " of Various Photographic Plates.

9. Abbe's Test-plate photographed with a ^th astigmatic objective (1st

position).

10. Abbe's Test-plate photographed with a ^th astigmatic objective (2nd

position).

11. Foraminifera from Bognor, Sussex. 1°

13. ,, (Cornvsjriru).

14. „ from Bognor, Sussex.

15. Genitalia of Glossina palpalis. 1G. Anglia hancockii, n. sp.

17. Portrait of the late John Green Waller, F.S.A.

18. Callidina vesicular is, n. sp.

19. Drepanidotacnia undulata.

20. „ sagitta, n. sp.

21. Polyzoon (Idmonea radians').

22. Water-mite (Ecpolns jmpilosa, Soar).

23. Foraminifera (Orbiilina unircrsa).

24. „ from Timor Sea.

25. Portrait of the late John Jewell Vezey, F.R.M.S.

26. British Water-mites.

27. „

28. ,, i,

Id. ,, ,,

30. ,, ,, (Atax crassipes).

31 . Group of Insect Eggs (Stereo-photo-micrograph).

32. Diatom, Navicula lyra ,, ,,

33. Polycystina. „ „

34. Tetramastix opolioisis (Zacharias).

Portrait of the late Edward Dadswell, F.R.M.S., preceding Plate 5. A loose plate was issued in connection with F. J. Cheshire's paper, page 1

Vlll LIST OF ILLUSTRATIONS.

FIGURES IN THE TEXT.

Page 1. Diagram of aplanatic system. ,, 4. Abbe's test for aplanatism. „ 5. Cheshire's apertometer. ,. L'l\ Diagram of test-plate. „ 23. Light-intensity diagrams. 2 I

25.

96. Antennae of Diptera.

106. Pseudofeltria scovrjieldi, n. sp.

107. Mideopsis erassipes, n. sp.

118. Small glass tank.

119. ,, ,, „ (another form). 138. The Rousselet Compressorium. 142. Diagrams of spherical aberration.

1 13. Diagram illustrating the sine law. 1 \ R

***»• 11 11 11

146. Diagrams of un-corrected and over-corrected lenses.

117. ,, achromatic lenses.

148. Diagram of photographic objective.

150. „ apochromatic lens.

167. Filaments from foot of house-fly.

160. Modified Rousselet Live-box.

173. Diagram illustrating doubling of lines in Abbe experiment.

174

■*■ • 3' 5? >J 11 11 11 11

223. Discoi'hina parisiensis, plastogamic,

234. Diagram of genitalia as usually found in Diptera.

2".i2. Stops used for producing stereo-photo-micrographs.

328. The Coon Finder.

360. Eggs of water-mites.

366. Nymph of Eulais.

376. Diagrams of stereoscopic vision, etc.

429. Stops used in stereo-photo-micrography.

430. Double image produced by suitable stop.

441. Diagrams showing effect of iris upon image. 449

THE JOURNAL

OF THE

■«♦»■

4b*

^ntkttt Muxanta^xtul ChtL

/^

V"

ABBE'S TEST OF APLANATISM, AND A SIMPLE APERTOMETER DERIVED THEREFROM.

By Frederic J. Cheshire, F.R.M.S.

(Bead Ju?ie 19th, 1903.)

The Abbe-Helmholtz sine-law expresses, as is well known, the necessary and sufficient condition for the production, by the different zones of a wide-angle optical system, of equal -sized images of an indefinitely small object on the axis of the system, and in a plane at right angles to that axis.

Fig. 1. — Diagram of Aplanatic System.

Let P and Q be a pair of conjugate and aplanatic foci, on the axis of a wide-angle optical system, then the sine-law states that the sine of the angle a, which any ray makes with the axis in passing from the point P, must bear a constant ratio to the sine of the angle /?, which the corresponding conjugate ray makes with the axis, when passing through the point Q. If the points p and Q be immersed in media with refractive indices

Journ. Q. M. C, Series II. — No. 54. 1

2 F. J. CHESHIRE ON ABBE'S TEST OF APLANATISM,

fx and /xi, respectively, and if m equal the magnification produced by the system, the sine-law fully stated takes the form —

sina = M tH = k (a constant) * .... (1) sin /3 /jl

In general, a ray, passing from the point p to the point Q, and undergoing a total deviation equal to the sum of the angles a and /?, would suffer, in any practical optical system, many refractions, which, however, it is not necessary for our purpose to consider. All that we are concerned with is the total devia- tion, and this may be looked upon as though produced by a single refraction only, at the point c, obtained by producing the incident ray and its conjugate ray until they meet as shown. To the point c the name chief point has been given by Professor S. P. Thompson.

In a similar way, let Ci be the point of intersection of a second pair of rays, making angles a\ and/?!, respectively, with the axis. Then from simple geometry we have —

sin a c q sin (3 c p' and —

sin ai Ci Q

sin fii Ci P ' and, since the ratio of the sines is constant, —

c Q _ Ci Q, /2\

C P Ci P

and so for any pair of rays. It follows from the constancy of this ratio and the fixed distance p Q, that the chief points must lie upon a curve, which is the locus of a triangle constructed on a given base and with a constant ratio between the lengths of its other two sides. This locus is a circle, f with its centre on the axis P Q, and cutting it, say, at v. Let p v = a, and v Q = b ; then r, the radius of this circle, is obtained from —

r = ^; (3)

o — a and, if a be less than b, the centre o of this circle is at a point on the axis such that we have for d the distance p o :

d^^~ W

o — a

We have thus arrived at the following important result : — In

* See HeatWs Geometrical Optics, 1887, p. 255.

\ Briggs and Bryan, Co-ordinate Geometry, 3rd edition, Part I., p. 186.

AND A SIMPLE APERTOMETER DERIVED THEREFROM. 3

any wide-angle optical system, ichich satisfies the sine-condition for a pair of conjugate foci, the equivalent refracting surface for these foci is a part of a sphere. *

In the case of the microscope objective, with which we are principally concerned, the image is always formed in air, hence pi = 1 in equation 1, and for a pair of conjugate rays meeting in the vertex v, —

b _ sin a _ p.

a sin/2 M ' \ /

Putting l for a + b, the distance p q, and u/p for b/a, we can write equation 3 in the form —

r- ^LM . . (6)

and equation 4 as —

d = J~?- ■ • <7>

An example will show the use and application of the last two equations. A dry lens, of a focal length of 15*8 mm., gave in a plane 205 mm. above the plane of the object, on the stage of the microscope, a magnification of 11*5. Substituting these values in equation 6, and remembering that /x = 1 in this case, we have, for the value of the radius of the equivalent refracting spherical surface —

205 x 11-5 1Q r = (11-5)* -1 = lbmm- And obviously, so long as a<&, this surface must be convex on its upper surface. By substituting in equation 7, we get for the distance d of the centre of curvature o below the aplanatic focus p, —

d = (ii-5)»-i = 1'6mm-;

and again, so long as a<^b, o is below p. Thus, in a very simple and practical way, it is possible to determine for any aplanatic system, from the distance between the aplanatic foci

* This proposition is well known for the particular case in which one of the aplanatic foci is at infinity, as for a telescope object-glass ; but, so far as I can discover, the general proof given above, simple though it is, and important as it appears to be, does not occur in any English book on the subject. Dr. von Rohr, of Jena, has, however, since the reading of the paper, drawn my attention to an article by Mittenzwei in the Jahrbuch fiir Photographie, 1888, pp. 317-20, which clearly anticipates my proposition.

4 F. J. CHESHIRE ON ABBE'S TEST OF APLANATISM,

and the magnification, the radius of curvature of the equivalent refracting surface and the point at which the latter cuts the axis. Abbe's Test of Aplanatism. — In the year 1879,* Abbe, wishing to ascertain to what extent objectives, made before the formulation of the sine-law, satisfied that law, invented the test diagram shown by Fig. 2. The problem was to find the nature of the curves, which, drawn upon a flat surface placed normal to the axis of a microscope and at a given distance below the lower focus of the objective to be tested, should project into the upper focal plane of the objective as a rectangular network of equi-thick

Fig. 2.

ABBES TEST FOR APLANATISM (a = 12'5 mm.)

and equi-distant parallel straight lines, in the event of the sine- law being fulfilled. These curves, by a method to be subsequently described, can be shown to be hyperbolas. To use the diagram, it should be placed upon the stage of the microscope, and the object to be tested focussed upon the middle point of the bottom line. The body of the microscope^ carrying the objective with it, should then be racked back through 12 5 mm. Upon removing the eye-piece and looking down the tube, one-half of the back of the objective will be found to be occupied by an image of the diagram, in the form of the net-work referred to, if the objective is a good one.

* See Gesammelte Alhandlungen von Ernst Able, p. 226,

AND A SIMPLE APERTOMETER DERIVED THEREFROM. 5

It occurred to the author of this paper that Abbe's test might be modified to project into the upper focal plane of an aplanatic objective to be tested for numerical aperture — not for aplanatism — -

Fig. 3.

4*

CHESHIRE'S APERTOMETER. (a = 25 mm.)

a series of equi-thick equi-distant concentric circles, each of which should correspond to a definite and predetermined N.A. The result is shown by Fig. 3.

Theory of the New Apertometer. — Returning to Fig. 1, let us

6 F. J. CHESHIRE ON ABBE'S TEST OF APLANATISM,

consider the ray pcq intersecting the second (back) principal

focal plane of the objective, at a distance h from the axis ; and

let the distance of this plane from the point q = i^. Then, q

being in air, we have from equation 5, —

n usin a /ox

sin /? = C (8)

m v '

Since the angle /?, in a microscope system, never exceeds a few degrees, its tangent may be taken as equal to its sine ; hence —

■k/8-ri (9)

Ll

and the magnification at Q is equal to the distance Ll5 divided by the back focal length of the objective system ; or —

« - y (10)

Combining equations 9 and 10 we obtain —

sm/3 = — -; m/

and substituting in equation 8 —

~7- = fx sin a = N.A (11)

a well-known result which tells us that for objectives of a given focal length their N.A.'s vary directly as the effective diameters in the upper focal planes. Imagine now the point p in air (fx = 1), and the ray cp produced backwards until it intersects, at a distance r from the axis, a plane normal to the axis, and at a distance A from the aplanatic focus p ; and further, let us suppose that rays can only enter the system through a very small stop at p. Then to find the radius r of a circle which, placed normal to the axis and at a distance A from the aplanatic point p, shall project so as to completely fill the effective opening in the upper focal plane of an objective with a given N.A., we have only to remember that the N.A. = sin a, and that r/A = tan a, to obtain the desired equation, —

R= A 'tan (sin -1 n.a.) (12)

A circle drawn with such a radius, and placed at the distance A) will fill any objective with the given N.A., no matter what its focal length may be.

Agreeing, then, upon some convenient value for A? it is a very simple matter to calculate the various values of r for a series of circles which shall correspond, in the way described, to N.A.'s

AND A SIMPLE APERTOMETER DERIVED THEREFROM. 7

of 0*1, 0*2, 0*3, and so on. These circles would, as is obvious from a consideration of equation 11, project into the upper focal plane of any objective as a number of equi- distant, concentric circles, but they would not, in general, be of equal thickness. To secure this object, it is necessary to calculate, for each circle on the diagram, a thickness which corresponds to an equal increment of the N.A. Thus, instead of calculating the radius of a circle to project as equivalent to a N.A. of 0*5, say, it is better to calculate for 049 and 0*51, draw the two circles, and blacken the space between them. The difference between the N.A. represented by the circle of the inner edge of any line and that represented by the circle of the outer edge is thus in every case equal to 0*02 N.A. The following table has been calculated in this way for a value of A = 1> anc^ f°r N.A.'s commencing at 0*1 and proceeding by steps of 0"1 to 0'9.

R.

N.A.

2nd „

3rd „

4th „

5th „

8th „

9th „

roo9

\0-ll

/0-19 \_0-22

ro-30

\0-33

/0-42 \0-45

/0-56 \0-59

/0-73 \0-77

/0-96 \1-01

ri-29

\l-38

ri-95

\2-19

0-09 011

0-19 0-21

0-29 0-31

039 0-41

0-49 0-51

0-59 0-61

0-69 0-71

0-79 0-81

0-89 0-91

To use this table for the calculation of the radii of the N.A. circles for any other value of A , it is only necessary to remember that R must be read in the unit selected for A, and must be multiplied by it. Thus if A be taken as 2 inches, each number under r must be multiplied by 2, to obtain the desired radii in inches, Similarly, if A be taken in centimetres, R must be

8 F. J. CHESHIRE ON ABBE's TEST OF APLANATISM.

read as centimetres. Should the apertometer, when made, be too large to be accommodated on the stage of the microscope, with its centre in the axis of the instrument, it should be cut down on one side until it is possible to do so.

In using this apertometer it is necessary to observe the image in the upper focal plane of the objective, either directly, or after it has been magnified in some way. Whatever method is adopted it is important that a small stop should be used, placed virtually at the point p, to sharply define the apex of the cone of light taken up by the objective. One of the following methods may be employed : —

1. The unassisted eye may be used, in which case the image of the eye-pupil formed by the objective serves to define the point p. Care should be taken to keep the eye fixed during the taking of a reading.

2. The observation may be made through a 2 — 3 mm. hole in a plate on the top of the draw-tube, replacing the ordinary eye- piece.

3. The bottom of the draw- tube may be fitted with a low- power lens, with a small stop near its upper focal plane — this lens forming with an eye-piece a low-power telescope.

4. By using a low-power eye-piece — the lower the better — fitted with a 2 — 3 mm. stop in the usual place, to form in the eye- ring an image of the image in the upper focal plane of the objective. The eye-ring may then be examined with a hand- magnifier.

The 2nd and 4th methods will generally be found the most convenient — the first for testing low-power objectives, and the second for testing high-power ones.

[The diagrams on the loose plate accompanying this paper are intended to be cut out and used on the microscope in the way described. The apertometer disc should be placed upon the microscope stage, with its centre in the axis of the instrument, upon which the objective to be tested should be focussed. Then, upon racking back the body through 25 mm., and removing the eye-piece, the N.A. of the objective will be found projected in its upper focal plane.]

Jovrn. Quekett Microscopical Club, Ser. 2, Vol. IX., No. 54, April 1904.

Iautd with Journal Q.M.C., April 1904.

ABBES TEST FOR APtANATISM (a = 12'5 mm. )

CHESHIRE'S APERTOMETER. I a = 25 mm. )

THE SPIDERS OF THE SUB-FAMILY ERIGONINAE.

By Frank P. Smith. {Read October lQth, 1903.)

Plate 1.

A retrospective glance at the published work of the Quekett Club will be sufficient to convince one that, whereas certain classes of animals and plants have received no small amount of attention, several groups of equally interesting organisms have been for some reason or other almost completely neglected.

Notwithstanding the fact that many members of this Club are at present engaged upon special research work in other directions, I think it may be useful to bring forward a few notes upon one of these neglected groups, namely the Araneae or Spiders. It is quite possible that one or two members may be in quest of a subject upon which to bestow a portion of their leisure, and even if this be not so I think I may claim as an extenuation that there are at least many spider-slides in the possession of the Club and in private collections which might be rendered more interesting by a few remarks upon the structure and habits of the creatures from which they were prepared.

Before further discussing the study of Araneae I ought, perhaps, to justify the position I am taking up that this branch of science is one which actually falls within the province of a society devoted to microscopical investigation. It is obviously a matter of great difficulty to draw a hard and fast line between what might be termed a microscopical and a non-microscopical study, for in every branch of research work the microscope not only plays a most momentous part, but must be regarded as a sine qua non by the serious investigator. It appears, however, only reasonable to suggest

10 F. P. SMITH ON THE SPIDERS OF THE SUB-FAMILY ERIGONINAE.

that a group, the greater part of whose representatives absolutely defy identification by the unaided eye, must be regarded as microscopic, and, basing our observations upon this assumption, let us consider the suitability of the various creatures included in the order Araneae as candidates for microscopical investigation.

In Great Britain we have nearly 550 known species of spiders, varying in body length from 1 mm. to 20 mm., and of these certainly not more than 20 per cent, can be satisfactorily identified without microscopical aid. Moreover, several genera of large spiders, Aranea for example, are not by any means satisfactory as at present limited, and a complete revision of these groups is an urgent necessity. It is fairly certain that any sub-division will have to be founded upon somewhat obscure characters, and a vast field of work is here open to any enterprising student of minute nature who can boast of moderate efficiency in the manipulation of the microscope and dissecting-knife. It must be distinctly understood that I have not the slightest intention of advocating attention to the Spiders simply as a means of adding slides to our cabinets, and although I shall indicate methods by which certain portions of these creatures may be prepared as permanent objects, such preparations should be regarded only as means to an end — as marginal notes, so to speak, to the main work of the studious arachnologist.

For an explanation of the neglect of this order by students of nature, we have, to my mind, not far to seek. We are constantly being brought into contact with the expression, "a happy medium " ; but there are two sides to every question, and we undoubtedly have in many cases an " unhappy medium" in the form of an object which, hovering on the boundary between two conditions, fails to find favour either upon one side or the other. Our neglected spiders must, I fear, be placed in this category. Some of them which are too large to mount upon an ordinary slide still require, as already stated, microscopical examination for their indentifica- tion, and even those forms whose small size permits of their

F. P. SMITH ON THE SPIDERS OF THE SUB-FAMILY ERIGONINAE. 11

being flattened out in balsam, at once become unrecognisable when so treated. Specimens, also, cannot be preserved by desiccation, as in the case of the lepidoptera and coleoptera, and cannot, consequently, be placed in neat series in cabinets. We might briefly summarise the so-called difficulties and draw- backs to the study of spiders as follows. The Araneae are creatures whose non-resistant integument renders " setting " upon pins or cardboard an impossibility ; whose size in many cases precludes the possibility of mounting them in cells after the manner usually adopted by microscopists, thus necessitating their preservation in bottles or tubes ; and yet whose minute and obscure specific and generic differences render the removal of specimens from their tubes, for purposes of microscopical examination, almost inevitable.

These drawbacks, however, are more than counter-balanced by facts, which, although at first liable to be overlooked, will appeal strongly to the embryo araneologist after a few weeks of serious work. There is no need for expensive and cumber- some appliances, no time spent (or wasted !) in setting legs at a regulation angle, no soaking or boiling in liquor potassae or corrosive acids, the whole matter being almost as simple as dealing with pond life, a class of object which has always deservedly found favour with microscopists. The advantage, too, of being able to turn a specimen under examination in different directions should never be under-estimated, the absence of such a facility being undoubtedly one of the most serious drawbacks to the orthodox mounted object.

Of course, I do not mean to assert that the theoretical portion of the subject is free from difficulties. Quite the reverse. But the obstacles which exist should be by no means insurmountable by such workers as our Club possesses ; and by giving some amount of attention to these strange little creatures, we may hope to avoid any accusation of partiality based upon the fact that, whereas we have systematically studied the minute inhabitants of the deepest oceans and the fossil organisms of the sedimentary rocks from the most re- mote regions of the globe, many of the denizens of our own

12 F. P. SMITH ON THE SPIDERS OF THE SUB-FAMILY ERIGONINAE.

gardens, fields, and forests have been consigned to oblivion, for no other reason than that they occupy a position somewhere between the microscopical and non-microscopical spheres of research. The Dublin Microscopical Club has been responsible for some valuable araneological work ; why should not we be likewise ?

Before examining our spider we must catch it, and a few brief remarks upon the collection of specimens may therefore be of use. The requisite apparatus is of a most unassuming type, and all the necessary articles could no doubt be found amongst the paraphernalia of the average microscopist. An umbrella, the older the better, a newspaper, a pair of forceps, a few dry tubes of various sizes, a bottle of methylated spirit, and a note-book ; these for all ordinary purposes conclude our list. I might have included a strong net for " sweeping " low herbage, but personally I deprecate this somewhat wholesale and promiscuous method of collecting ; for not only are the captures exposed to considerable risk of damage by reason of the struggling mass of insects which accumulates at the bottom of the net, but any notes as to habitat or snare are entirely precluded.

The umbrella is held in an inverted position under trees, which are beaten or shaken to dislodge some, at any rate, of their tenants. A few species cling to the foliage with such pertinacity that nothing short of close search will enable the collector to obtain them. The newspaper is spread upon the ground whilst tufts of grass or low herbage are being violently shaken or torn to pieces above it. This method is, as a rule, especially productive, yielding a rich harvest of the more minute forms, chiefly of the family Linyphiidae. The dry tubes are used for obtaining species capable of rapid gradatorial progression, the specimens being hustled by means of one hand into the tube held by the other, and the opening then promptly closed. The minute species of Erigoninae, with which I wish to deal in the present paper, are most easily captured by means of a wetted finger, being thence transferred to the spirit-bottle. Further information on collecting may be obtained ] from the Rev. 0. P.

F. P. SMITH ON THE SPIDERS OF THE SUB-FAMILY ERIGONINAE. 13

Cambridge's Spiders of Dorset, or from my own papers in the Essex Naturalist, December 1902 and Nature Study, March 1904.

The most useful method, generally, of examining a spider is the following. A pomade-pot lid is nearly filled with methylated spirit, and the specimen under observation placed in it. The depth of the spirit should be sufficient to entirely submerge the object, which is then examined by reflected light. For ordinary araneological work no objectives will, as a rule, be required higher than a quarter-inch, the two-inch and one-inch being perhaps the most generally useful. It occasionally behoves the arachnologist, desirous of discerning the exact form of some obscure appendage, to distort various structures by means of potash and pressure; but this method must be treated as the exception, and not the rule. The legs and palpi of the smaller spiders are usually sufficiently transparent to be mounted in Deane's medium, after a few weeks in glycerine, without any alkaline treatment and, thus prepared, are very suitable for examination with dark-ground illumination. The form of the caput, as seen either in profile, from above, or from the front, is of great importance for purposes of identification and com- parison, but for this purpose the required portion will have to be cut from the body and mounted in a cell of alcohol. In the few preparations of this kind which I have made, a loose mass of cotton wool was placed in the cell — this keeping the object in position against the cover-glass, and also preventing its moving from the centre. Several cements have been recommended for sealing spirit-mounts (e.g. see Journal of the Quekett Micro- scopical Club, Ser. II., Vol. VI., p. 149) ; and although the student of minute spiders may seldom desire to prepare permanent slides of his specimens, it is as well to be acquainted with the technical details of the process in case necessity should arise.

For the storage of specimens I think the following method is unrivalled for simplicity, neatness, compactness, and economy. A wide-mouthed bottle of about four ounces capacity is taken, a number of tubes two inches in length and about three-eighths of an inch in diameter being ranged round the inside, and kept

14 F. P. SMITH ON THE SPIDERS OF THE SUB- FAMILY ERIGONINAE.

against the glass by a central plug of cotton wool. The bottle is nearly filled with methylated spirit, so as to completely sub- merge the tubes, each of which is separately plugged with wool. The labels, written either with pencil or Indian ink, are dropped in the tubes with the spiders. To give some idea of how much space should be allowed, I might say that the sub-family Erigoninae, with which we are at present chiefly concerned, contains about 120 species, all of which could be satisfactorily stored in tubes of the above-mentioned size.

The spiders included in the family Linyphiidae, to which the Erigoninae belong, are all of a small or moderately small size, amongst them being the most minute representatives of the Araneae. The eyes are normally eight in number, arranged in two transverse rows ; but one or more pairs may be atrophied, and even the whole of these organs may be absent. The form of the caput in the male varies to a surprising extent in different species, but, with a few exceptions, that of the female is quite normal. The legs are more or less furnished with spines, but in many cases these are very small, and often there is only one upon the tibia of each leg, the other joints being quite devoid of them. In addition to these spines and the ordinary hairs, the legs are sparsely furnished with minute organs, which I propose to denominate sensory setae. These peculiar structures are described and figured by F. Dahl,* who believes them to be organs of hearing. W. Wagner,t however, gives it as his opinion that they are more probably connected with some other sense, and suggests that by their aid the spider may be enabled to prog- nosticate atmospheric disturbances. Personally, I am inclined to ascribe to them acoustic properties, but I do not feel justified in expressing any strong opinion upon the matter until further opportunities for investigation shall have cleared up some of the difficulties with which at present the subject is beset. For the benefit, however, of any one who may be anxious to aid in the unra veiling of one of the many mysteries of spider structure,

* Arch. mikr. anat., xxiv., pp. 1-10. Translation in Ann. Mag. Nat. Hist., Ser. V., vol. xiv., pp. 329-37.

t Bull. Soc. Imj). Nat., Moscow, 1888, pp. 119-31.

F. P. SMITH ON THE SPIDERS OF THE SUB-FAMILY ERIGOXINAE. 15

I may, perhaps, be permitted to make a few remarks upon the minute organs in question, especially as their arrangement has been recently used as an important character in the separation of some of the genera of Linyphiidae.

Viewed with a two- thirds inch objective they appear as small globular bodies, from the centre of each of which usually springs a long slender bristle. The fact that these bristles are usually much longer and more nearly at right angles with the leg than are the ordinary hairs and spines, will help to distinguish them. An increased amplification will show that the basal part of the structure — which I propose to term the pocillum — is goblet- shaped, and that it is to the bottom of this organ that the bristle or seta is fixed. That these organs play some important part in the economy of the spider I think there can be no doubt. If, for example, we take a leg from a spirit-preserved specimen of the very common Pachygnatha degeerii, or the larger P. clerckii, treat it with boiling glycerine, mount it in Deane's medium, and examine it with, say, a quarter-inch objective, we shall find, as a rule, that the contents of the leg will have greatly contracted, and that the only points at which an attachment with the integument is maintained are at the bases of these sensory setae. There is, in fact, every indication of there being an important nerve connected with each of these organs, and it is, therefore, only reasonable to suppose that they are capable of transmitting impressions of some kind to the brain ; but as to the exact nature of the sensations which they are instrumental in produc- ing, there exists at present, as already stated, very considerable doubt. That spiders possess the power of distinguishing aerial vibrations — at any rate, to some extent — there can, I think, be little doubt ; but that they have anything like an accurate sense of hearing is by no means certain, although one would be naturally led to this conclusion by the knowledge that many species are capable of producing sounds by means of stridulating organs. The fact that a spider will often exhibit no signs of motion when a tuning-fork is vibrating near it, must not be taken as conclusive that the creature cannot hear. Obviously, it would be to the creature's advantage, even if it heard an

16 F. P. SMITH ON THE SPIDERS OF THE SUB-FAMILY ERIGONINAE.

approaching buzz, to remain motionless until the supposed victim absolutely touched the snare, Some species of Aranea which are much persecuted by fossorial wasps have been seen to drop suddenly from their snares upon the approach of their tormentors; and, by mechanically imitating the buzzing of one of these insects, I have been able to produce, although by no means invariably, a similar result.

The falces of the Linyphiidae are devoid of any basal pro- tuberance, a very constant structure in some of the spider families ; but their outer surface is furnished with a number of more or less parallel ridges, which are actuated by a point upon the palpus, no doubt for the purpose of stridulation. In some species these ridges are almost obsolete and broken up into a number of short pieces ; but in most cases they are quite distinct under careful illumination and accurate focussing. In some species — for example, those of the Walckenaera group — the ridges are widely separated and few in number, whereas in the genus Erigone they are excessively fine and close together. The clypeus — i.e. the space between the anterior row of eyes and the front edge of the caput — is hardly ever narrower than the distance between lines tangential to the fore edges of the anterior central eyes and the hinder edges of the posterior centrals.

The family Linyphiidae, as defined by the foregoing characters, may be synomymically expressed as follows : Linyphiidae (ad partem), Black wall, 1861. Theridiides (ad partem), 0. P. Cambridge, 1878-81. Argiopidae (ad partem), E. Simon, 1895, etc. To be more concise, Blackwall's Linyphiidae consists of those species which are common to both Mr. Cambridge's Theridiides and Mr. Simon's Argiopidae, whilst my Linyphiidae is equivalent to Blackwall's, less the genus Pachygnatha.

The numerous species constituting the family Linyphiidae fall into two divisions, whose systematic separation, however, owing to the presence of many intermediate forms, is a matter of great difficulty. Having before us a vast and heterogeneous assemblage of creatures which have apparently developed along two divergent main lines from a common stock, it is, of course, only natural

F. P. SMITH ON THE SPIDERS OF THE SUB-FAMILY ERIGONINAE. 17

to suggest using such characters for a preliminary broad division as will separate these hypothetical lines of development. The difficulty becomes at once apparent when one considers that there are still in existence very many of the more primitive types, and the exact point at which the dividing line should be drawn becomes more or less a matter of speculation. As a natural consequence, the two sub-families thus formed, which I propose to term Linyphiinae and Erigoninae, might reasonably be re- garded as somewhat conventional and ill-defined; but when one comprehends the vagueness of the boundaries which separate, for example, the Drassidae from the Clubionidae, the Sparassidae from the Philodromidae, or even the Agelenidae from the Pisauridae, it becomes at once evident that it is often absolutely necessary to employ minute and obscure structural details, and even a concensus of characteristics, in order to reduce certain motley assemblages of spiders into groups possessed at any rate of something like homogeneity.

Perhaps I might be permitted to draw for a moment upon my imagination, and to sketch a purely hypothetical spider which might reasonably be supposed to have enjoyed the distinction of having been the ancestral type of the numerous species of Linyphiidae.

The thorax would be normal, the eyes arranged somewhat as in Pachygnatha. The falces would be fairly powerful, each being provided with a rudimentary stridulating organ. The legs would be similar to those of Pachygnatha, but upon the tibia of each one would appear a tiny spine. From such a creature let us examine the process of evolution in the case of the Linyphiinae. From the very first a tendency to develop additional spines upon the legs becomes apparent, and continues with few exceptions throughout the whole series. The palpal organs of the male become vastly more complex as we advance, and the external branch of the tarsus assumes a variety of forms, such as would lead one to suppose that it fulfils some important function in connection with the reproductive mechanism. The genital aperture of the female in the higher forms usually possesses a clavus, which often attains a high state of development. The

Journ. Q. M. 0., Series II. — No. 54. 2

18 F. P. SMITH ON THE SPIDERS OF THE SUB-FAMILY ERIGONINAE.

tibia of the male palpus is, however, with very few exceptions, devoid of any projection or apophysis, and the caput in that sex is almost invariably normal, resembling that of the female. The metatarsi exhibit a gradual elongation compared with the tibiae, and the whole spider shows a decided tendency to increase in size. Contrasting now the Erigoninae, we find no sign of increase in the number of spines, the single minute example upon each tibia being constant throughout the series. As in the case of the Linyphiinae, the palpal organs become more prominent and complex, but the external branch of the tarsus is never very conspicuous. The genital aperture of the female is almost invariably devoid of a clavus. The tibia of the male palpus is, with hardly an exception, provided with an apophysis, which, in the more specialised form, is often of surprising dimensions, and, the caput in this sex is nearly always more or less modified either by the elevation of a portion of its upper surface, or by the presence of post-ocular depressions. The metatarsi are normal, seldom exhibiting any tendency towards undue elon- gation.

The species constituting the sub-family Erigoninae may be arranged in three groups, which, although by no means sharply defined, will perhaps be of some assistance to the student.

The Neriene group contains a number of genera with the sternum at least as broad as long, and the elevation of the male caput, when present, so placed as to have practically no effect upon the position of the eyes. The spiders themselves are about the medium size of the Erigoninae. The genus Stylothorax [Gongy Helium, Simon (in part)], contains some of the least specialised species of this group. In S. fuscus a slight gibbosity appears behind the eyes, which becomes more pronounced in several allied species — S. apicatus, for example, being furnished with a small conical projection, surmounted by a tuft of hairs. In Erigone and Neriene [Gonatium, Simon (in part)], there are no distinct cephalic eminences, but the whole caput is more or L ss raised. Allied to Neriene are the genera Dicyphus and Hypoinma, with large oval protuberances behind the eyes.

The Diplocephalus group contains a large number of minute

F, P. SMITH ON THE SPIDERS OF THE SUB-FAMILY ERIGONINAE. 19

spiders, including the smallest known representatives of the order. It seems to be an offshoot from some of the more specialised forms of the Neriene group, and is characterised by the sternum being at least as broad as long, and by the elevation of the male caput, which is usually present, affecting to a greater or less extent the position of the eyes. Many of the species included in this group are of most grotesque form, and the variations in structure of the male caput and palpi are of great interest. The identification of the females, as in the Neriene group, is often a matter of great difficulty, and the surest and most reliable characteristic is, as a rule, the armature of the genital aperture. In some species of this group the abdominal integument becomes coriaceous, especially in the genus Lophocarenum.

The Walckenaera group contains a moderate number of spiders, which are, as a rule, rather large compared with the average size of the Erigoninae. The sternum is usually considerably longer than broad, the cephalo-thorax somewhat elongate, and the tibia of the male palpus furnished with prominent apophyses. The palpal tibia of the female is longer than the patella, and usually somewhat enlarged towards its extremity, and the tarsus of the palpus is, in this sex, more acuminate than in the majority of the Erigoninae. The form of the male caput varies to a remarkable degree. In the genus Cornicularia there is simply a small process, varying in form with the species, projecting from the centre of the ocular area. In Walckenaera the caput may be quite normal, or it may be remarkably modified. In W. acuminata we have, perhaps, the acme of eccentricity. The caput of the male is elevated in the form of a long slender curved prominence, which carries the entire ocular group. Four eyes are placed near the middle of this prominence, which is there somewhat dilated to accommodate them, the remaining four being at the apex, which is also somewhat expanded, and is ornamented with a number of minute hairs.

Detailed generic or specific descriptions of these minute arachnids would be quite out of place in this purely intro- ductory communication, but I append drawings of a few

20 F. P. SMITH ON THE SPIDERS OF THE SUB-FAMILY ERIGONINAE.

species from the London district which will give some idea of what the collector may expect to find. Throughout nature we know that habit and structure are more or less interdependent, and it is consequently only reasonable to suppose that there are many points in the life-histories of these curious creatures which, when patiently worked out, will furnish us with an almost end- less series of pleasant surprises. Although there are many little difficulties to be overcome in the study of the microscopic spiders, both in the matter of identification and also in the observance of habits, I think it is only fair to admit that there are few subjects more replete with possibilities which could be placed at the disposal of the student of microscopical nature.

Explanation of Plate 1.

Cephalo-thoraces of male Erigoninae, legs and palpi truncated.

Entelecara acuminata (Wid.), profile. Dicyphus comuttis (Bl.), profile. Comicularia cuspidata (Bl.), profile. Diplocephalas fuscipes (BL), profile. Pocadicnemis pumilus (BL), profile. Wideria antica (Wid.), profile. Walckenaera acuminata (BL), profile.

„ ,, (BL), viewed from the front.

Magnifications approximately 45 diameters.

Fig.

1.

55

2.

5»

3.

5)

4.

)5

5.

J»

6.

)J

7.

8.

Journ. Quekett Microscopical Club, Ser. 2, Vol. IX., No. 54, April 1904.

21

AN OVERLOOKED POINT OONCERNING THE RE- SOLVING POWER OF THE MICROSCOPE.

By Julius Rheinberg, F.R.M.S.

{Read December 18th, 1903.)

The experiment I have the honour of showing you this evening is a modification of one shown to me by Dr. G. Johnstone Stoney, F.R.S., who, about nine years ago, made a most interesting discovery, which, whilst fitting in perfectly with theory, seems to have entirely escaped notice hitherto. It is this : —

If we have a number of equidistant lines or points, it is well known what the Numerical Aperture of the objective must be in order to resolve them, and it has been tacitly assumed that, whether the number of lines be two, three, four, or a large number, so long as the distance between the individual lines is the same, the same Numerical Aperture is needful for the purpose of distinguishing the lines from one another.

It has been left for Dr. Johnstone Stoney to demonstrate that when there are only two lines, they can be resolved with an N.A. sensibly less than that required to resolve a large number of lines the same distance apart.

The arrangement of the experiment on the table this evening, showing this, is as follows.

The object under the microscope is the 15,000 to the inch band on one of those beautifully ruled test plates by Grayson, of Mel- bourne. In this band, two adjacent lines happen to be somewhat longer than the other ten, as seen in Fig. 1. An 8 mm. apo- chromatic objective by Zeiss and a x 27 compensating eyepiece is used. Just above the objective I have an arrangement like the jaws of a spectroscope slit, which, actuated by the projecting wooden tongs, can be opened and closed symmetrically from the centre of the objective. The N.A. of the objective can thus be gradually

22

J. RHEINBERG ON AN OVERLOOKED POINT CONCERNING

increased or decreased in the direction at right angles to the lines. Immediately in front of the lamp flame there is a screen, with a slot in it of such width that, when the plane of the screen is focnssed by the condenser on to the object in the usual manner, the slot just covers the width of the band of lines under observation. A disc with a very narrow slot in its centre is placed in the stop carrier of the condenser.

If now, whilst attention is fixed on that portion of the band where the whole of the twelve lines lie next to one another, the N.A. of the objective is gradually cut down to that point where

&$/

the band of twelve lines is just no longer visible (the lines being blurred into one another), and we then glance down at the position of the two projecting lines, we shall see that these still distinctly appear as separate lines — somewhat thickened and without sharp edges, but yet clearly resolved.

And what to many may seem remarkable is that, if we remove the eyepiece of the microscope and look down the tube, we see the direct or dioptric beam shining brightly over the centre of the objective, whereas apparently there are no flanking spectra on each side. In looking down the tube in this way, it is necessary to keep the eye perfectly central and without any shift. A simple way to do this is to hold a metal disc with a pinhole at its centre over the tube. The dummy eyepiece on the table is fitted with a metal disc like this.

.Now for the explanation of the phenomenon. You all know that the condition for resolution of lines is that the angle of the objective must be sufficiently wide to grasp, besides the direct or dioptric beam of light, at least one of the beams diffracted by

THE RESOLVING POWER OF THE MICROSCOPE.

23

them. That is one of the most important generalisations of Abbe, made over thirty years ago.

As it may not be quite clear to all as to what is meant by dioptric and diffracted beams of light, I would like, without entering into details, to point out that it simply relates to distribution of the light which has got through the object. If the object is a single narrow slot, and a parallel beam of light passes through it, it appears on the other side as a broad beam of varying intensity. The light intensity of the central part of this broad beam might be represented by the curve xy (Fig. 2).

<%2

I Slot

Suppose we have two slots, each as wide as the first one, and a space between them of the same width, then the distribution of the light which has passed through is different. The hump of the intensity curve we had before gets broken up into three humps, a, b, and c (Fig. 3), by the so-called, " interference " of light waves. The central hump b is known as the direct or dioptric beam, and the humps a and c, on either side of it, are called the first maxima. A better name for the central hump than either of the two above is that which Lord Kayleigh has applied to it, viz. the zero maximum.

What happens if we have three slots instead of two, and pass

24

J. RHETNBERG ON AN OVERLOOKED POINT CONCERNING

parallel light through them? The humps a, b, and c ol the intensity curve will remain, but they will be steeper, and there will be a tiny negligible hump between them.

And for every extra slot we add, we get extra tiny little humps (secondary maxima) between the large humps or chief maxima a, b, and c. These remain in the same position whatever the number of slots, but they get steeper and steeper. After six or seven slots their sides are almost perpendicular (Fig. 5).*

Jflany Slqts

Reverting to Abbe's generalisation, he showed that the condition necessary for resolution of the slots or lines was fulfilled when, and only when, the objective had a sufficiently wide angle to grasp two of these large humps or chief maxima. They bear what is known as a phase relationship to one another ; in other words, the ether particles which are swinging to and fro whenever light is passing, happen to be just swinging in unison at the centre of

* Simple detailed explanations as to the formation and changes in the appearance of these maxima are given in my article, " The Common Basis of the Theories of Microscopic Vision treated without the aid of .Mathematical Formulae," in the Zeitschrift fur wis sen sell aftliche Mikroskopie, vol. xix. Reprints obtainable from Williams & Norgate, 14, Henrietta Street, London, W.C.

THE RESOLVING POWER OF THE MICROSCOPE.

25

each of the humps and on corresponding portions of the same. However, into this we need not enter here, the point principally to be noted being that at least two of the light maxima must be grasped by the objective, if the lines are to be seen separately.

And now see how neatly this explains the newly observed fact. Fig. 6 shows the intensity curve (a) when we have the light passing through a number of lines, and (b) when we have it passing through two lines only ; these curves are placed just below one another in the diagram. The shaded part represents the metal jaws above the objective, cutting down its N.A.

You will observe that when the lateral humps of the curve are quite cut off, there still remains a part of the lateral humps of the curve b. This it is which suffices to account for the fact that the two lines can still be seen resolved. If the reason is asked why we could not see the parts of the lateral maxima when we looked down the tube, it is simply because the light of the dioptric beam or zero maximum was so intense that it drowned the other. For we were looking at the zero maximum of twelve lines, and at but a small part of the lateral maxima of two lines. If precautions are taken so that the zero maximum observed also proceeds from two lines only, the portions of the lateral maxima can be readily seen.

The above explanations and the figures refer to the case when

26 J. RHEINBERG ON AN OVERLOOKED POINT CONCERNING

the resolution of the two clear lines is compared with the resolution of a band of clear lines. The explanation of the resolution of two dark lines as compared with a band of dark lines — as in the case of the Grayson ruling experiment — is analogous. The reason for treating the former case rather than the latter is that it is simpler to explain, and it illustrates the principle just as well.

It is a matter worthy of particular note that the new fact concerning resolution was not first discovered and then explained. In this case Dr. Johnstone Stoney first reasoned the matter out many years ago and then made the experiment, testing the result when Grayson's rulings became available. It is a striking example of the way in which the Abbe diffraction theory may be turned to account.

A further point is this : — According to theory, the distance apart of the lines in the image must vary inversely as the dis- tance apart of the maxima in the intensity Curve. But when we cover up the greater portion of the lateral maxima in the curve b, the distance between what remains (x, Fig. 6) is less than the distance between their brightest portions had they been uncovered (y, Fig. 6). Therefore we ought to expect the lines to appear farther apart in the first case than in the last. And this may, under favourable conditions, be shown experimentally

There are certain interesting problems which it seems to me the newly observed fact may materially assist to clear up. Not the least of these is the question as to how far one part of an object influences the formation of the image of another part. This is a question on which differences of opinion still exist amongst those who have occupied themselves with the problems of microscopic optics, and one which is of great importance because it assists in determining to what degree of approximation the image of an object may be made to faithfully depict the structure of the object.

It may be in place to mention that the only difference between my arrangement of the experiments and those of Dr. Johnstone Stoney is that he arranged for showing them with oblique light, using two maxima only, whilst I have preferred to make them with axial light, using three maxima.

#

THE RESOLVING POWER OF THE MICROSCOPE. 27

Dr. Johnstone Stoney's experiment shows in the most conclusive manner that, under the conditions in which the experiment is made, — viz. with a narrow beam or cone of light — the one part of the object markedly influences the image of another part. The next question therefore is, can the effect be eliminated if we use a wide cone and critical illumination 1 We have to test the point experimentally to see whether under the altered conditions the resolution of the two lines will outlast that of the twelve-line band, or whether they will disappear together. I have not yet been able to satisfy myself as to the result. Some preliminary trials clearly showed the effect to be mucli less marked when using a wide cone of light, but it was still to be perceived. Evidence on this point from microscopists accustomed to work with critical illumination would be valuable.

In conclusion I would say that it is the usefulness of the results to which a careful study of the newly demonstrated fact may lead that must be my apology for having detained you so long in discussing and explaining an intrinsically trivial matter ; it will be borne in mind, however, that it is only by close attention to little things like this that the complicated questions connected with microscopic vision can be brought a step forward.

I am sure it will interest you if I quote a few words received from Dr. Johnstone Stoney this morning. I had sent him the MS. of my paper to make sure that my statements regarding himself were correct, and he says : —

" I have suggested two corrections as to dates. It was in the end of 1893 or in 1894 that I discovered the new resolution of light into undulations of flat wavelets, and one of the first results I got out by it was that a pair of lines, or a pair of dots, should be resolved by an objective of less aperture than that required for the resolution of a ruling of lines or a row of dots equally spaced, and that, when so resolved, the spacing of the pair of lines should appear to be greater than that of the ruling. This I got out by the theorem in reversal represented graphically by your Fig. 6.

" So far as I know, until my application of this principle of reversal, aided by the new method of resolving light, to such

28 J. RHEINBERG ON THE RESOLVING POWER OF THE MICROSCOPE.

problems, there did not exist any proof which would satisfy a physicist of the agency of diffracted light in producing images, upon which (as a matter of fact, but not as an understood thing) Abbe came by experiment.

" I find my first publication of the new method of resolving light was in December 1895, and shortly afterwards I had a conversation with Lord Rayleigh about it, and explained to him why a pair of lines or dots should be resolved by an aperture insufficient to resolve a ruling equally spaced. In his earlier papers he, like other writers on optics, had regarded them as requiring the same aperture.

" This conversation led Lord Rayleigh to look into the matter under the more familiar hypothesis that light consists of rays, and he published the result in his 1896 paper, which I under- stand has been recently reprinted by the It. M.S. The result comes out with ease by my method of treatment, and I told Lord Rayleigh that it ought also to come out by the older methods of treatment, if it were possible to take the phases sufficiently into account. This Lord Rayleigh succeeded in doing, which I regard as a great achievement."

Journ. Quekett Microscopical Club, Ser. 2, Vol. IX., No. 54, April 1904.

29

SYNOPSIS OF THE KNOWN SPECIES OF BRITISH FRESH-WATER ENTOMOSTRACA.

Part III. Ostracoda, Phyllopoda, and Branchiura.

By D. J. Scourfield, F.R.M.S.

{Read December 18th, 1903.)

Plate 2. In this concluding part of the Synopsis of British Fresh-water Entomostraca, it is principally the Order Ostracoda that will occupy our attention ; but for the sake of completeness, the two poorly represented groups, Phyllopoda and Branchiura, must not be omitted, although it will be impossible to deal with them very satisfactorily, owing to the scanty records.*

Notwithstanding the fact that the Ostracoda possess very little attraction for the majority of collectors of Entomostraca, it is probably true that this group has received more attention in this country than either the Cladocera or the Copepoda, with the result that we possess two monographs, by Brady (56) f and by Brady and Norman (57), which between them contain figures and descriptions of nearly all our known species. It will only be necessary, therefore, in a few instances, to give references to foreign papers for information as to our native Ostracods, and but a comparatively small number of synonyms need be intro- duced.

With regard to the distribution of the Ostracoda in the British Isles, the same plan as before will be followed — i.e. the records for each species will be summarised in a table, so that its occur- rence in different parts of the country can be seen at a glance. In the case of very rare forms, more definite information will also be given, under the name of each species, as to where they have been collected.

* The species new to Britain, discovered since the publication of Parts I. and II., and several important new records of rare species of Cladocera and Copepoda, will be found in an appendix.

t The numbers in brackets refer to the lists of literature at the end of this and the two previous Parts.

J\ *

■' c

*vV

i

30 D. J. SCOURFIELD, SYNOPSIS OF THE KNOWN SPECIES OF

OSTRACODA.

Cyprididae.

Cypria Zenker. C. exsculpta (Fischer).

Cypris striolata Brady (56). Not a very common species, although widely distributed.

C. ophthalmica (Jurine).

Cypris compressa Baird (1), Brady (56). A very common species. The " lacustris" form probably occurs in this country, although it has not been separately recorded.

Cyclocypris Brady & Norman. C. globosa (Sars).

Cypris cinerea Brady (56). Not yet seen in the south and east of England or in Wales.

C. serena (Koch).

Cypris laevis Brady (56). Occurs frequently in all parts of the country.

C. laevis (0. F. Miiller).

Cypris minuta Baird (1) ; Cypris ovum Brady (56). Also common throughout the British Isles.

Scottia Brady & Norman. S. browniana (Jones).

Only found on the shores of Loch Fadd in the Island of Bute.

Cypris O. F. Miiller. C. fuscata (Jurine).

C.fusca Baird (1), Brady (56). A very common species in ponds and small pieces of water, but not in lakes.

C. incongruens Ramdohr. C. aurantia Baird (1). Somewhat rare, although widely distributed. It is said by Brady & Norman (57) to be most common in slightly brackish water, but it is by no means characteristic of such situations.

C. pubera 0. F. Miiller.

C. cuneata Baird (1) ; C . punctillata Brady (56). A rare species. The only record I have of it from the south and east of England is a shallow pond at Esher, Surrey.

BRITISH FRESH- WATER ENTOMOSTRACA. 31

C. virens (Jurine).

C. tristriata Baird (1). Very common everywhere in small pieces of water.

C. elliptica Baird.

This has only been recorded by Baird (1), and by Brady &• Norman (57) ; three localities in all.

C. affinis Fischer.

C. tessellata (in part) Brady (56) ; G. reticulata Brady & Norman (57). Apparently a rather rare species.

C. obliqua Brady.

A comparatively common form, not only in ponds, etc., but also in lakes. Curiously enough, it is rarely alluded to by foreign authors, although it is known to occur on the Continent.

C. ornata 0. F. Miiller.

There is but one published record for this species — namely, pond at Shotton Hall, co. Durham.

C. clavata Baird.

Not certainly seen in this country since Baird's record from "Copenhagen Fields, July 1836." It has, however, been found on the Continent.

C. trigonella Brady.

The only record is that referred to by Brady in his 1868 mono- graph (56).

C. bispinosa Lucas.

This may possibly be a brackish- water form, as it has only been found near the sea. The single British locality is " a pool in a small island at Yalentia, Ireland," but it has also been found in Guernsey.

Cyprinotus Brady. C. prasinus (Fischer).

Cypris strigata Baird (1) ; Cypris salina Brady (56). Only found in situations where the water can be at least occasionally brackish.

Stenocypris Sars. S. fasciata (O. F. Miiller).

Herpetocypris fasciata Brady & Norman (57). I have recently found specimens of this fine species near

32 D. J. SCOURFIELD, SYNOPSIS OF THE KNOWN SPECIES OF

Catfield, Norfolk. Although figured and described by Brady & Norman (57) it has not been previously recorded as British.

S. chevreuxii Sars [Sars (67)].

Professor G. S. Brady informs me that he took this species many years ago in a pond at Lyndhurst, in the New Forest, but that it has hitherto remained unrecorded as British.

Herpetocypris Brady & Norman. H. reptans (Baird).

Candona reptans and C. similis (young) Baird (1) ; Cyp'is reptans Brady (56). A very common species in most parts of the country.

H. strigata (0. F. Miiller).

Not very frequently met with, and not yet recorded from Ireland and Wales.

H. tumefacta (Brady & Robertson).

Cypris tumefacta Brady & Robertson (58). Somewhat commoner than the foregoing perhaps, but still rather rare.

Ilyodromus Sars. I. olivaceus (Brady k Norman).

Erpetocypris olivaceus Brady & Norman (57) 1889. Only recorded from Duddingston, Kinghorn, Black, and Forfar Lochs in Scotland, and from the River Lathkill in Derbyshire.

I. robertsoni (Brady & Norman).

Eo'petocypris robertsoni Brady & Norman (57) 1889. Mr. T. Scott (20) has found this in several localities in Scot- land, and Mr. D. Robertson also collected it near Peebles and in Skye, but it has not been seen in other parts of the British Isles.

Prionocypris Brady & Norman. P. serrata (Norman).

Cypris serrata Brady (56) ; Erpetocypris serrata Brady & Norman (57) 1889. Apparently a rather rare species, and confined to England so far as our present records go. In addition to the localities noted by Brady & Norman, I have collected it from the East London Waterworks reservoirs at Walthamstow, and from Purneet, both in Essex.

BRITISH FRESH- WATER ENTOMOSTRACA. 33

Cypridopsis* Brady.

C. vidua (0. F. Miiller).

Cypris vidua and C. sella Baird (]).

Pionocypris vidua Brady & Norman (57) 1896, Scott (20), Scourfield (29). One of the commonest of the British Ostracoda.

C. obesa Brady & Robertson.

Pionocypris obesa Brady & Norman (57) 1896. Not yet recorded from Wales or Scotland, but this may be simply due to the fact that it is not usually regarded as anything more than a variety of C. vidua.

Cypridopsella* Kaufmann.

C. aculeata (Costa).

Cypridopsis aculeata Brady (oQ), Brady & Norman (57). Not found as a rule far away from slightly brackish water.

C. villosa (Jurine).

Cypris westwoodii and ? C. elongata Baird (1). Cypridopsis villosa Brady (oQ), Brady & Norman (57).

^Yidely distributed, but not a very common species.

C. newtoni (Brady & Robertson).

Cypridopsis newtoni Brady & Robertson (58), Brady <k. Norman (57), Scott (20). One of the rarer British species.

C. variegata (Brady & Norman).

Cypridopsis variegata Brady & Norman (57). Also a rather rare species, though widely distributed. Since the " Entomostraca of Epping Forest" (29) was issued, I have found specimens of this species in Higham Park Lake.

* Notwithstanding the opinion expressed by Brady & Norman in the Appendix to Part II. of their monograph (57), there seems no sufficient reason for removing C. vidua and its nearest allies from the genus Cypridopsis as it was originally described by Brady in 1868, and these authors themselves give C. vidua as the type species of this genus in the first part of their work. It follows, therefore, that the name Pionocypris must be dropped so far as our British species are concerned, although it will still hold for certain Australian forms. As, however, the C. aculeata — C. villosa group seems to form a distinct genus, the name Cypridopsella, proposed by Kaufmann, and now ad >pted by Sars and other authors, has been followed here.

Journ. Q. M 0., Series II.— No. 54. 3

34 D. J. SCOURFIELD, SYNOPSIS OF THE KNOWN SPECIES OF

Potamocypris Brady. P. fulva (Brady).

Bairdia ftdva. Brad}' (56) A fair number of records altogether from Scotland, Ireland, South Wales, and north of England, but only one from south and east of England — viz. Kew Gardens — and none from North Wales.

Notodromas Lilljeborg. N. monacha (0. F. Miiller). Cypris monacha Baird (1). Found in all parts of the country, with the possible exception of the extreme north of Scotland.

Cyprois Zenker. C. marginata (Straus).

? Cypris gibbosa Baird (1). Cyprois fiava Brady & Norman (57), 1889. To the single published British locality — Duddingston Loch, near Edinburgh — can now be added R. Thurne at Potter Heigham, Norfolk, where I took specimens in 1898.

Ilyocypris Brady k Norman. I. gibba (Ramdohr).

Cypris gibba (in part) Brady (56). The records for this are not quite satisfactory, as many of them include /. biplicata. I. biplicata (Koch).

Cypris gibba (in part) Brady (56). /. bradii Brady & Norman (57), 1896. This seems to be a commoner form than /. gibba.

Candona Baird. C. Candida (O. F. Miiller), as defined by Vavra (68). C. lucens (in part) Baird (1). An abundant and widely distributed species. The British records comprise two or three distinct forms possibly of specific rank. C. neglecta Sars [Miiller (66)].

C. Candida (in part) Brady (56). Hartvvig, who has given much attention to this genu>, says (62, p. 92) that one of Professor Brady's figures (56, PI. 37, le) certainly refers to this species, and not to C. Candida. Brady k, Norman also refer to a form " very closely approaching C. neglecta " (57, p. 99).

BRITISH FRESH-WATER EXTOMOSTRACA. 35

C. angulata G. W. Miiller [Muller (66)].

C. Candida (in part) Brady (56), PI. 25, figs. 8 and 9.

The angulation of the shell behind, and the net-like markings, separate this species from G. caiulida. The specimens figured by Brady came from Gravesend, but I know of no other definite records. C. elongata Brady & Norman.

Only recorded from Lough Neagh, Ireland. C. lactea Baird.

C. lactea and C. detecta Brady (56).

Not an uncommon form in this country, though seldom men- tioned by Continental writers.

C. eompressa (Koch).

C. pubescens Brady & Norman (57), 1889. C. pubescens (Koch).

C. abbreviata Brady MS. (Scourfield, 26). Hartwig seems to think (62, pp. 104 — 108) that the two fore- going species, as recorded by Brady <fc Norman (57), should be united under C. eompressa. He further states, however, that the true C. pubescens Koch also occurs in England, as he has had from Canon Norman specimens which had been collected in Norfolk (I.e. p. 126). C. stagnalis Sars.

C. ambigua Scott (20, 46). Apparently a rare species. Only recorded from Lochgelly Loch and Loch Fitty, Fifeshire (46).

C. zenckeri Sars.

Only recorded from a pond at Ferry Hill, co. Durham (57).

C. rostrata Brady & Norman.

Not a very common species. C. marchica Hartwig [Muller (66) = G. rostrata~\.

Specimens of this species (which very closely resembles C. rostrata) from Lanarkshire were sent by Canon Norman to Herr Hartwig, who has recorded the fact in (62) p. 99.

C. fabaeformis (Fischer).

C. diaphana Brady & Robertson (58). According to Hartwig (62, pp. 112 — 114) the C. fabaeformis of Brady k Norman's monograph (57) is not really Fischer's C. fabaeformis, but a distinct species, which he calls G. bradyi.

36 D. J. SCOURFIELD, SYNOPSIS OF THE KNOWN SPECIES OF

C. protzi Hartwig [Miiller (6G)].

C. kingsleii (in part) Brady & Robertson (58), PI. 9, figs. II and 12. Prof. Brady tells me that the specimens he sent to Herr Kaufmann, as recorded in (65), p. 392, were probably from a quarry at Hairmyres, near East Kilbride.

C. hyalina Brady & Robertson.

The fairly numerous records for this species are almost entirely confined to the " Broads" district and Scotland.

C. acuminata (Fischer).

In the paper already quoted several times (62), p. 119, Hartwig does not consider Brady k Norman's C. acuminata to be actually that species, but suggests that it may be C. caudata Kaufmann.

C. euplectella Robertson.

Found in a number of localities in the south and middle of Scotland [see 20, 46, 57). This year (1903) I have also obtained it from the Norfolk Broads district, near Catfield.

Candonopsis Vavra.

C. kingsleii (Brady k Robertson).

Candona kingsleii Brady k Robertson (58), Brady k Norman (57), Scott (20, 46).

In some parts of the country this seems to be quite a common species, and it is also widely distributed.

Darwinulidae. Darwinula Brady k Robertson.

D. stevensoni Brady k Robertson.

Polycheles stevensoni Brady & Robertson (58).

Darwinella stevensoni Brady k Robertson (59). Many recorded localities in the East Anglian Fen and Broads districts ; also found in the west of England, South Wales, south and middle of Scotland, and Ireland.

Cytheridae. Metacypris Brady k Robertson. M. cordata Brady k Robertson.

Only taken in the Fens and Broads of East Anglia, the Ellesmere district, Shropshire, and in Mayo and Galway, Ireland.

BRITISH FRESH- WATER ENT0M0STRACA. 37

Limnicythere Brady.

L. inopinata (Baird).

Cythere inopinata Baird (1).

A fairly common species, but not yet recorded from Ireland.

L. compressa Brady & Norman.

Whitefield Loch, Wigtownshire, and Loch Aber, Kirkcud- brightshire, are the only recorded localities for this species.

L. sanctipatricii Brady & Robertson. A rather rare species.

L. monstrifica (Norman).

Only recorded from the " Fen " and " Broads " districts, and a canal at Fleckney, Leicestershire.

Cytheridea Bosquet. C. torosa (Jones).

Bather a brackish-water than a fresh-water species, but found occasionally in water not perceptibly brackish. The variety " teres " is said to be common in the Fen district, and has also been recorded from Shropshire, South Wales, Lancashire, and Firth of Clyde.

C. lacustris (Sars).

Several records from different parts of Scotland, but only three from other parts of the British Isles — namely, B. Nene and R. Thames, England, and Lough Neagh, Ireland.

As already noted, a few of the Ostracoda mentioned above are to be found more frequently in brackish than in fresh water — e.g. Cyp'inotus prasinus, C ypridopsella acideata, Cytheridea torosa, and perhaps Cypris bispinosa. Other more decidedly brackish-water forms, all belonging to the Cytheridae are : Cythere pellucida Baird. ,, porcellanea Brady. ,, gibbosa Brady & Robertson. ,, fuscata Brady. Loxoconcha viridis (0. F. Miiller). Cytherura gibba (0. F. Miiller). And there are several further species which, although usually marine, may be found at times in brackish water.

38 D. J. SCOURFIELD, SYNOPSIS OF THE KNOWN SPECIES OF

DISTRIBUTION OF BRITISH FRESH- WATER

OSTRACODA.

Species.

■,?

55 55 55

55 I)

55

Cyprididae. Cypria exsculpta

„ qphthalmica . Cyclocypris globosa . „ serena .

,, laevis

Scottia brownkvna Cypris fuscata . ,, incongruens . pubera . virens elliptica . affinis obi i qua . ornata . <■ la rata . trigonella bispinosa Cyprinotus prasinus . Stenocypris fasciata . ,, chevreuxii H> rpetocypris reptans ,, strigata

„ tumefacta

llyodromus olivaceus „ robertsoni

Prionocypris serrata. Cypridopsis vidua

,, obesa .

Cypridopsella acuhata rlllosa yteictoni variegata Potamocypris fulva . Notodromas monaclia Cyprois inarginata llyocyjyris gibba

„ biplicata

Candona Candida neglecta angulata

55 55 55

55 55

England.

South and East.

X

X

X

X

X

X

North

5 A

0 m

-

a a

% a m

:

X X X x

x

X ...

X

X

X

X

X

X

X

X

X

X

X

X

SCOTLASP.

X

X

X

BRITISH FRESH-WATER ENTOMOSTRACA.

39

1 England.

72

3

93

X X X

Scotland.

South and

East.

North

0

gg

Tr.

a

1~

O

to

— a a

—

z

-

r.

— a

—

._

Species.

1=

S3 0

-5

•ja

—

K a

•A

,0

43

Eh

-t3 ■n

-

1

3

CD

3

Cyprididae — continued. Candona elonqata ....

„ lactea .

,, compressa .

,, pubescens .

X X X

?

9

•

X X X

X

• • •

X X X

...

X X

X X

X X

X X

„ stagnalis „ zenckeH

X

X

X X

X X

,, rostrata ., marchica .

?

X

X

...

X X

X

X X X X

X

X X X

X X X X

X

X X

X

X X X

X

• a •

„ fabaeformis

,, protzi .

,, hyalina

,, acuminata .

X

X

X

X X X X

X

X X

X

X X X

X

X

X X

X

X X X X

X

X X

X

X X

X

X

X X X

• • c

x

V

„ euphctella . Candonopsis kingsleii

Darwinulidae. Daru:inula stecensoni

X

f • •

X

Cytheridae. Metacvnris cordata .

X

X

Limnicythere inopinata

,, compressa . ,, sanctipatricii „ monstrifica . Cytheridea torosa

■

X X X

X X X

X X

X

X X

X

X X X X X

...

X

X X

X X

X X

X X

X

X

X X

X

• • *

X

X

7? )) ""* v/"

., lacustris .

X

X

PHYLLOPODA.

Apus Schaeffer. A. caneriformis Schaeffer [Baird (1)].

It is doubtful whether this ought to be included in any modern list of British Entomostraca, as it has not been found apparently for more than half a century. The localities given by Baird (1) are Bexby (Bexley ?) Common ; Devonshire ; and Bristol.

Chiroeephalus Prevost. C. diaphanus Prevost [Baird (1)].

This beautiful species, I am glad to say, is still to be found

40 D. J. SCOURFIELD, SYNOPSIS OF THE KNOWN SPECIES OF

occasionally in this country, although very rare. In addition to the records given by Baird (1), it has been taken at Tillrnire, near York, by a brother of Professor Brady in 1862 ; at Seaford, Sussex, by Mr. H. Maxwell Lefroy, in 1899; and near Brocken- hurst, in the New Forest, in March, 1900, and October, 1901, by Mr. G. T. Harris. I am indebted to Canon Norman for the two first-mentioned records.

BRANCHIURA. Argulus 0. F. M tiller. A. foliaceus (L.) [Baird (1), Clark (60), Wilson (69)].

The records of the occurrence of this well-known fish parasite are not very satisfactory, but there is every reason to suppose that it occurs in all parts of the country. It certainly occurs in Ireland and Scotland as well as in England (see 1, 15, 21a, 48).

A. coregoni Thorell [Wilson (69)].

Canon Norman possesses specimens of this species which were taken by Mr. Dodds on the Barbel, in Leicestershire. It has not previously been placed on record as British.

APPENDIX.

The three following species have been added to the known British fauna since the publication of the previous parts of this Synopsis.*

CLADOCEBA.

Daphnidae.

Scapholeberis Schoedler. S. aurita (Fischer).

Mr. R. Gurney has recently found this fine species in Norfolk, and has published a short account of its habit of using the sur- face-film of water for support, etc., in the Annals and Magazine of Natural History (61). It has been obtained from the following localities : Pond, at Herringfleet ; Ditch, at S. Walsham ; and ( latfield Fen.

This species is described and figured by Lilljeborg in the ( 'ladocera Sueciae.

In a recent paper (63) Mr. W. F. de V. Kane has recorded Bosmina dollfusi Moniez from three Irish lakes. If this were a good species it would be an addition to our fauna, but I consider it merely as a form of Ji. obtu.sirostris,

british fresh-water extomostraca. 41

Lyncodaphnidae. Ophryoxus Sars. O. gracilis Sars.

During a short visit to Fort Augustus last August, in connection with the " Lake Survey " organised by Sir John Murray, K.C.B., I had the good fortune to obtain this species in Loch ISTess, and also in a backwater of the Caledonian Canal, at Coiltry Lock. In the former the species was living in great abundance in the shallow and sheltered bay at Inchnacardoch, near Fort Augustus, and a single specimen was also found on the protected side of the little breakwater belonging to the Monastery at Fort Augustus. I hear from Mr. J. Murray that none were to be taken after September, and that the species has not yet (March) reappeared. At Coiltry only a few specimens were seen. In all cases parthenogenetic females only were observed.

This species appears to be a characteristic northern form, at least in Europe. It has only hitherto been recorded from Norway, Sweden, Finland, the Kola Peninsula, Greenland, Minnesota, and Wisconsin. Its occurrence therefore in Scotland is particularly interesting.

Lilljeborg describes and figures it in his usual admirable manner in the Cladocera Sueciae.

COPEPODA.

Cyclopidae. Cyclops 0. F. Miiller.

C. robustus Sars [Lilljeborg (40)].

Professor G. S. Brady tells me that he has had specimens of this species from Ennerdale Lake. They were actually taken many years ago, but it is only quite recently that he has definitely made them out to be C. robustus. The species has probably been often included in records of C. vernalis, to which it is very closely allied.

The following additional records of rare or otherwise interesting- species have been made since the issue of the two previous parts.

CLADOCERA.

Diaphanosoma brachyurum (Lievin). A peculiar variety of what appears to be this species, with a strongly projecting fore- head, has been recorded by Mr. Kane from Lough Mask (63,

42 D. J. SCOURFIELD, SYNOPSIS OF THE KNOWN SPECIES OF

footnote, p. 214), and I have found the same form in Loch Tarff, near Fort Augustus.

Holopedium gibberum Zaddach. This species has now been recorded from a second Irish locality — Lough Mask — by Mr. Kane (03).

Daphnia atkinsoni Baird. Ponds at Happisburgh, Honing, and Br u instead, Norfolk (R. Gurney).

Simocephalas serrulatus (Koch). Swamp near Grantown-on- Spey (Dr. and Miss B. Sprague). This is the first time the species has been recorded from Scotland.

Bosmina lonyirostris var. cornuta. Mr. J. Murray obtained this last year at Crieff, in Perthshire, i.e. in the " Highland " region.

Bosmina mixta Lilljeborg. Mr. Kane reports the occurrence of this species from two additional Irish localities — L. Oughter and L. Conn (63).

Ilyocryptus agilis Kurz. This has been found in Scotland by Mr. J. Murray, but the exact locality cannot be given until last year's collections of the " Lake Survey " have been re-examined.

Ilyocryptvs acutifrons Sars. This rare species has been found by Mr. B. Gurney in Wroxham and Sutton Broads, Norfolk.

Macrothrix laticornis (Jurine). Pond at Thorpe, and Waxham Cut, Norfolk (R. Gurney). It has not previously been recorded from the Broads district.

Macrothrix hirsuticornis Norman & Brady. Some very fine examples (one as much as y1^" long) of this species have been found by Mr. W. A. Cunnington at Cambridge.

Alona eleyans Kurz. To the single record given in Part I. may now be added, Pond at Brumstead, Norfolk, where it was faken in company with D. atkinsoni, by Mr. R. Gurney.

Leydigia quadrangular is (Leydig). Mr. R. Gurney finds this species fairly well distributed in the Broads district, though when Part I. was issued I knew of no records for it in that locality.

Alonella exigua (Lilljeborg), This species, as distinct from A. excisa, has been obtained by Mr. R. Gurney, in Sutton, and Wroxham Broads and Catfield Fen, Norfolk, and he has also collected it in North Uist.

Pleuroxus aduncus (Jurine). Although not included in Part I. in the list of Cladocera of the Norfolk Broads, owing to the absence of definite records, Mr. R. Gurney finds this species to be the commonest of the genus in that area.

BRITISH FRESH-WATER ENTOMOSTRACA. 43

Anchistropus emarginatus Sars. A single specimen of this most interesting species has been seen by Mr. R. Gurney from Sutton Broad, Norfolk.

COPEPODA.

Diaptomus laciniatns Lilljeborg. When Part II. was issued I knew of no records of this species from the extreme north of Scotland, but Mr. James Murray informs me that last year he found it in the majority of the lochs of Sutherland. It is not, therefore, such a rare species as was supposed, though restricted in its distribution.

Cyclops bicuspidatus var. lubbochii Brady. This form has been found in the " Muckfleet," Norfolk, by Mr. R. Gurney, who believes that its appearance is directly dependent upon a rise in the salinity of the water, only the typical form being generally found there.

Literature Referred To.

56. Brady, G. S. " Monograph of Recent British Ostracoda."

Trans. Linnean Soc, vol. xxvi., 1868, p. 353.

57. Brady, G. S., & Norman, A. M. " Monograph of the Marine

and Fresh-water Ostracoda of the North Atlantic and of North-Western Europe." Scientific Trans. Royal Dublin Soc, ser. 2, vol. iv., 1889, p. 63, and vol. v., 1896, p. 621.

58. Brady, G. S., & Robertson, D. " Ostracoda and Foraminifeia

of Tidal Rivers." Ann. and Mag. Xat. Hist., ser. 4, vol. vi., 1870, p. 1.

59. Brady, G. S., & Robertson, D. "On the Distribution of

British Ostracoda." Ann. and Mag. Xat. Hist., ser. 4, vol. ix., 1872, p. 48.

60. Clark, F. N. " Argulus foliaceus : a Contribution to the

Life-History." Proc. South London Entomological and Xat. Hist. Soc, 1902 (published 1903), pp. 12—21.

61. Gurney, R. "Notes on Scaplioleberis aurita (S. Fischer)

a Cladoceran new to Britain." Ann. and Mag. Xat. Hist., ser. 7, vol. xii., 1903, p. 630.

62. Hartwig, W. " Die Arten der Ostracoden-Unterfamilie Cando-

ninae der Provinz Brandenburg." Sitzungs-Bericht der Ges.naturforschendeFreunde zu Berlin, 1901, pp. 87 — 129.

63. Kane, W. F. de V. " A Contribution to the Knowledge

of Irish Fresh-water Entomostraca — Cladocera." Irish Xatiirolist, vol. xii., 1903, p. 210.

44 D. J. SCOURFIELD, BRITISH FRESH-WATER ENTOMOSTRACA.

64. Kaufmaxn, A. " Die schweizerischen Cytheriden unci ihre

nachsten Verwandten." Revue Suisse de Zoologie, tome iv., 189G, pp. 313—384.

65. Kaufmann, A. " Cypriden und Darwinuliden der Schweiz."

Revue Suisse de Zoologie, tome viii., 1900, pp. 209 — 423. 6Q>. Muller, G. W. " Deutschlands Siisswasser-Ostracoden.''

Zoologica, Heft 30, 1900. 07. Sars, G. O. " On a new Fresh-water Ostracod — Stenocypris

chevreuxii." Archiv. f. Math, og Naturvidenskab, Chris-

tiania, vol. xviii., No. 7, 189G. 68. Vavra, W. " Monographie der Ostracoden Bohmens."'

Archiv der y aturwiss. Landesdurchforschung von Bohmen,

vol. viii., No. 3, Prag, 1891. 09. Wilson, C. B. "North American parasitic Copepods of the

Family Argulidae, with a Bibliography of the Group and

a Systematic Review of all known Species." Proc. U.S.

Nat. Museum, vol. xxv., pp. 635 — 742, Washington, 1902.

Explanation of Plate 2.

[In accordance with the desire expressed in Part II., some details of Cyclops nanus Sars and Belisarius viguieri Maupas have been illustrated on the accompanying plate. So far as

B. viguieri is concerned it is hoped that they will be sufficient to enable the species to be readily identified. With regard to

C. nanus, it may be mentioned that it is closely related to C. languidus in that it has both branches of the first pair of feet and the inner branch of the second pair two-jointed. The first antennae are, however, as in C. languidoides, only eleven-jointed. It is a very small species, being only about -^ in. in length.]

Fig. 1. Belisarius viguieri, ? , ventral view x 200. a = sper-

matophore. ,, 2. ,, ,, second antenna x 400.

„ 3. „ „ ?, fifth foot x 650.

,,4. ,, ,, $ , side view of furca x 300.

,, 5. ,, ,, £ , furca, ventral view x 225.

,, 6. Cyclops nanus, ? , fifth foot x 400. ,, 7. „ ,, ? , receptaculum seminis x 200.

., 8. „ „ $ , last joint of inner ramus of fourth

pair of feet x 450. „ 9. „ „ ?, furca x 175.

Tuwra. Quekctt Microscopical Club, Ser. 2, Vol. IX., No. 54, April 1904.

45

ON A NEW FRESH-WATER POLYZOON FROM

RHODESIA, LOPHOPODELLA THOMAS I,

gen. et sp. nov.

By Charles F. Rousselet, F.R.M.S. {Bead January 15M, 1901.)

Plate 3.

Up to quite recent times not a single species of fresh-water Polyzoa was known from the continent of Africa. To Dr. Stuhlmann is due the credit of having been the first to discover representatives of this class in Egypt, and later in German East Africa (24), between the years 1890 and 1892. These were Fredericella and Pluinatella, and also some statoblasts of Hyatt's Pectinatella carter i, a species previously known only from India. Then in 1893 and 1897, Dr. M. Meissner (23) found sessile statoblasts of Plumatella on some shells of fresh-water molluscs,, preserved in the Berlin Museum, which had come from East and West Africa, and this completes the whole known records, of fresh-water Polyzoa in Africa to the present time.

In October last, one of our members, Mr. R. H. Thomas, of Salisbury, Rhodesia, sent me a little bottle containing a gelatinous mass which, he said, was a fresh-water Polyzoon collected early in 1900, and preserved in alcohol. The polypides were all decayed, but in a piece of the gelatinous zoarium the hollow tracts which they had occupied can well be seen (Fig. 1), and in these branching tracts, which preserve the shape of the entocyst, I found a number of peculiar statoblasts in all stages of growth. An examination of these enabled me to inform Mr. Thomas at once that a Polyzoon having such statoblasts was not known in England, but I could not at the time say if any such form had been described in any other part of the world. Since then I have looked up all the recent literature on the subject, and have also made enquiries of specialists, and am now in a position to say that this is undoubtedly a new species, for which a new genus must be created, and moreover, it is the first

46 C. F. ROUSSELET ON A NEW FRESH-WATER POLYZOON

representative of fresh-water Polyzoa recorded from any part of Africa south of the Equator.

Before describing the characters of this new species, it may be instructive to hark back a little and see what has been done before, and what is the present state of our knowledge about these animals.

The fresh-water Polyzoa (or Bryozoa) form a very distinctive group containing only about 20 to 50 species, according to whether a number of these forms are considered good species, or merel}7 varieties, or synonyms. Professor G. J. Allman, who in 1856 published his fine work, " A Monograph of the Fresh- water Polyzoa," seems to have almost exhausted the subject as far as Great Britain is concerned, for, with the exception of the description of two very doubtful new Plumatellas by Parfitt (8) in 1866, and one remarkable new species, Kent's Victorella jxwida * (9), from the Victoria Docks in 1870, no work at all, or work of any importance, on this group seems to have been done or published in England. The marine Polyzoa, on the other hand, have come in for much more attention at the hands of zoologists.

During the last decades the principal descriptive work on fresh- water Polyzoa has been done in America by J. Leidy (2, 11, 12) and A. Hyatt (7), in Germany by Professor K. Kraepelin (17), and Dr. M. Meissner (22, 23, 24, 25), in France by J. Jullien (15), in Bohemia by Kafka (18), and in Japan by Oka (20). From India, Japan, South America, Australia, and Indo-China a few new species have been described, so that the total number of undisputed species does not at present exceed 20, leaving out all the more or less doubtful names wrhich have been alternately accepted and rejected by different investigators.

I will make no attempt to give even a short description of the known species of fresh-water Polyzoa, which can readily be found in the works mentioned in the bibliography at the end of this paper ; but a bare list of the recognised species, and of those named since Allman's monograph was published, may prove useful for reference.

* This was first found by Mr. W. Saville Kent at one of the earliest Quekett excursions, on September 12th, 1868. See Mr. Kent's first note in Science Gosaij) for 1868, p. 255. Later it has also been found in the Regent's and Surrey Canals, always parasitic on Cordylophora laevstris.

from rhodesia, lophopodella thomasi. 47

List of the Known Fresh-water Polyzoa.

British Species.

Lophophore horse-shoe shaped.

Cristatdla mucedo. Cuvier. Statoblasts circular, with hooked

spines. Lophopus crystallinus. Pallas. Statoblasts elliptical, pointed at

both ends, without spines. Plumatella repens. Linnaeus. Statoblasts oval, without spines. fruticosa. Allman \

5?

,, coralloides ,,

,, emarginata ,,

„ elegans „

,, dumortieri „

,, jugalis „

„ allmani. Hancock

All these are considered to be synonyms or varieties of PI. repens by continental writers.

Alcionella fungosa. Pallas

,, benedeni. Allrnan

„ flabdlum. Van Beneden

Plumatella lineata. Parfitt \ Two very doubtful

,, limnias. ,, j species.

,, (Hyalinella) punctata. Han- ) With soft gelatinous cock i creeping tubes.

Lophophoi'e circular.

Fredericella sultana. Blumenthal. Statoblasts kidney -shaped,

without annulus.

Paladicella ehrenberqi. Van Beneden ) c,, ,, ,

* \ Statoblasts absent.

Victorella , pavida. Kent »

Foreign Species. Lophophore horse-shoe shaped.

Cristatella idae. Leidy (America) \ All three considered to „ ophidioidea. Hyatt „ r be synonyms of

,, lacustris. Potts „ ) C. mucedo.

Lophopus jheringi. Aleissner (Brazil).

,, {Hyalinella) lendenfeldi. Kidley (Australia).

Lophopodella thomasi. Rousselet (Rhodesia, S. Africa).

,, (Pectinatella) carter i. Hyatt (India, East Africa).

48

C. F. ROUSSELET ON A NEW FRESH-WATER POLYZOON

55 55 55 55

55 55 55

55

55

55

55 55

55 55

All these are considered

to be synonyms or varieties of PI. repens.

Plumatella stricta. Allman (Belgium) y diffusa. Leidy (America) nitida. ,,

arethnsa. Hyatt aplini. Mac Gillivray

(Australia) hn-ifuga. Vaucher, Jullien hyalina. Kafka (Bohemia) pohjmorpha. Kraepelin

(Germany, etc.) [n'niceps. Kraepelin (Ger- many, etc.) / philippinensis. Kraepelin (Philippine Islands) {Hyalinella) resicidaris. Leidy, Jullien (America) vitrea. Hyatt, Jullien

(America) lophopoida Kafka (Bohemia) PectinateUa magnified. Leidy (America, Germany). gelatinosa. Oka (Japan).

55

55

These are con- sidered synonyms of Hancock's PI. punctata.

55

Lophophore circular.

Fredericella regina. Leidy (America) ^ These are considered ,, walkottii. Hyatt „ [■ synonyms of

,, pidcherrima. ,, ,, J F. sultana.

Paludicella midleri. Kraepelin (Germany).

,, (Pottsiella) erecta. Potts. Kraepelin (America). Urnatella gracilis. Leidy (America) Jlislopia lacustris. Carter (Central

India) Xorodonia cambodgiensis. Jullien (Indo-China) ,, sinensis. Jullien (Indo-China)

These four species are unlike the other fresh- water Polyzoa, and their affinities lie with the marine species.

As will be seen, the very variable genus Plumatella, having a horny, chitinous, tubular, branching ectocyst has the greatest number of species, but the claim to specific rank of nearly every one of these has been denied by one or the other eminent student of this group, who holds that they are synonyms, or at most

FROM RHODESIA, LOPHOPODELLA THOMASI, 49

only varieties of Plumatella repens. It has been stated, with much appearance of truth, that though the extreme forms differ markedly from the type, yet in every case a number of inter- mediate varieties have been found connecting them with Plumatella repens. Monsieur J. Jullien (15), in 1885, was the first to reduce all European Plumatellas to the one species PI. repens', but he strangely accepted all the American species. Professor Kraepelin (17), unable to find a way out. of this maze, deposed all the Plumatellas from their specific rank, and created out of them two new types, PI. polyforma and PI. pr'mceps, to which he subordinated the principal varieties. These types are mainly distinguished by their statoblasts, whether broad oval or elongated oval in shape. Some more recent investigators have accepted, whilst others have rejected, this arrangement. For the creeping Plumatellas, with soft, gelatinous tubes, M. Jullien has proposed the new name Hyalinella. Mr. Ridley's Australian Lophopus leyidenfeldi (19) seems to me to belong to this genus. M. Jullien (15) has also renamed the well-known Lophopus crystallinus into L. trembleyi, which is quite inadmissible according to the rules laid down by the International Congress of Zoology.

As regards their geographical distribution, most of the species have been found in England, America, Germany, France, Bohemia, Hungary, and Russia — that is, wherever they have been really looked for. Isolated species are known from India, Australia, Japan, South America, Egypt, East and West Africa, and now from Rhodesia, but it seems clear that it only requires a systematic search to find them in most countries where there are lakes, pools, canals, or slow-flowing streams.

Coming now more particularly to the species which forms the subject of this paper, I had only the statoblast to guide me in my search for its nearest allies. It is well known, however, that these resting or winter buds, produced only by the phylactolae- matous* fresh-water Polyzoa, are very characteristic of the different species, and are mostly quite sufficient by themselves to establish the identity of the animals to which they belong.

The statoblast consists of a central capsule surrounded by a dark brown ring of air cells, called the annulus, which enables the structure to float on the surface of the water. In Cristatella

* Which means possessed of a fleshy tongue, or epistome guarding the entrance to the mouth.

Journ. Q. M. C, Series II. — No. 54. 4

50 C. F. ROUSSELET ON A NEW FRESH-WATER POLYZOON

m n.cedo the shape of the statoblasts is circular, surrounded by a number of long hooked spines. Pectinatella magnified has very similar rounded statoblasts furnished with stouter hooked spines, and fewer in number (Fig. 9). In Plmnatella the shape is a more or less elongated oval, without spines ; in Fredericella they are kidney-shaped, and without annulus ; and in Lophopns crystal! in as the statoblasts are elliptical, and pointed at both ends (Fig. 8.)

The statoblast of the new species Lophop)odella thomasi, from Rhodesia (Fig. 3), has some considerable affinity with that of Lophopns crystallinus, being elliptical in shape, and also slightly curved in the direction of its longer axis, but instead of being pointed at the ends, it is truncated, and the points are replaced normally by five spines on each side, but their number may be reduced to three or four, and sometimes increased to six. These spines consist of short flattened rods of chitin, which appear to be outgrowths of the lateral edges of the annulus. Some of these spines I have seen to be bifurcate. All round their lateral edges these rods are beset with a number of minute, closely set, and curled-up hooks (Fig. 4) which appear of little functional use. Their structure is clearly seen in immature statoblasts, where the hooklets are still thin and not so much curled (Fig. 5). Collectively the hooklets give a beaded appearance to the spines, and it was only by examining an immature statoblast with as yet very thin annulus that I became aware of their structure. I have counted twenty and twenty-two hooklets round the edge of one of the spines. T have also seen one of the spines split horizontally into two, the hooklets adhering to both halves, showing that when the young bursts open the statoblast, it splits horizontally through the edge of the capsule and annulus, leaving one half of the complete annulus adherent to each half of the central capsule.

The central capsule has a thick, dark reddish brown chitinous covering membrane of lenticular form, convex on one side and flattened on the other; it is very nearly, but not quite circular, having a longer diameter of 385 /jl, and shorter diameter of 343 /x, and consists of two halves, similar to two watch-glasses, of different convexity, closely apposed round their edges. I found several of these naked capsules in the tubes of the polypides without annulus. The annulus forms a broad and thick cellular ring, not infrequently a little irregular or

FROM RHODESIA, LOPHOPODELLA THOMASI. 51

asynietric in shape, and is made up of two horizontal strata, each consisting of a single layer of hollow prismatic cells arranged like the two layers of cells of a honeycomb. The polygonal air cells are largest at the periphery, and become gradually smaller towards the centre. In mature statoblasts the cells cover the central capsule completely on the upper or convex side, whilst they leave a small bare central space on the concave side. The size of the statoblast of Lophopodella thoinasi is 857 //, long by 642 fx broad ; the spines attain a length of 75 /x, but of course the exact shape and size of the whole statoblast are subject to some variation.

The only Polyzoon having statoblasts approaching the characters above described is the one found in 1859 by Mr. H. J. Carter (4) in Bombay, and figured by him in Ann. Mag. Xat. Hist., 1859, ser. 3, vol. iii., p. 341. The statoblast (Fig. 6) is a broad oval in shape, with fourteen short spines at each end, and each of these is provided with six curled hooklets round its edge (Fig. 6). Mr. Carter considered his animal to be a Lophopus, though probably different from the European L. crystallinus, but he gave it no name. Later, in 1866, Hyatt (7) joined this animal to Leidy's genus Pectinatella, and called it P. carteri, for insufficient reasons, it seems to me, as I shall show presently. The statoblasts of this same species have in later years (1890) been found by Dr. Stuhlmann in Ugogo, not far from the Victoria Nyanza, in German East Africa, as reported in a paper by Dr. Meissner (24), showing that the species must have a wide distribution.

Reverting to my description of Lophopodella thomasi, Mr. Thomas, its discoverer, informs me in a second letter that the only colony he found was attached to the upper surface of a rotten stick, floating in a pool of still water, being an overflow of a small Khodesian stream. He remarks that the colony was exposed to the full sunshine, and not in a dark and shady place, where he had expected to find Polyzoa. The zoarium (or coenoecium of Allman) — that is, the whole colony stock — consisted of an oval patch of stiff gelatinous hyaline substance (Figs. 1 and 2), about 2| in. long by 1^ in. broad, and about g in. thick, with branching tubular channels radiating from the centre, which were tenanted by numerous polypides. The polypides protruded all round the edge and on the surface of the gelatinous ectocyst, leaving, however, a central oval space quite free of them. They

52 C. F. ROUSSELET ON A NEW FRESH-WATER POLYZOON

are quite decayed in the preserved zoarium, but Mr. Thomas says that they had a horse-shoe shaped lophophore and an epistome, and the internal arrangement conformed, no doubt, to that obtaining in Lophopus, Cristatella, and Plumatella, in all of which there is practically no difference in this respect.

At first I felt uncertain whether to place this new species in the genus Lophopus or Pectinatella, but after a careful study of all the ascertained characters I have come to the conclusion that it must be placed in a new genus, to which I have given the name Lophopodella, with Lophopus as its nearest ally.

It cannot belong to Pectincttella, as P. magnified, the type of this genus, first discovered by Professor Leidy in America, and since found also in Germany, near Hamburg and Berlin, forms very large agglomerated rounded masses, with a gelatinous ectocyst often several inches thick, on the surface of which the animals form closely-set irregular rosette-shaped colonies, with horizontal tubes. The mass may attain the size of a man's head on submerged timber, but has never yet been found on green water-plants. The statoblasts of this species (Fig. 9) are altogether different, being circular, resembling those of Cristatella mucedo, with a ring of twelve to twenty long hooked spines, projecting from the outer edge of the annulus.

The statoblasts of Lophopodella thomasi have, in general shape and character, a much greater resemblance to those of Lophopus crystal! inns ; but as one of the generic characters of Lophojms is, " statoblasts without spines,'*' it is not possible to include this new species in this genus.

I have mentioned above that the Polyzoon which Mr. Carter discovered near Bombay in 1859, and which was named Pecti- natella carteri by Hyatt (7), has a statoblast (Fig. 6) resembling that of the new species, with fourteen short hooked spines at each end. The following is an extract of Mr. Carter's (4) remarks on his animal (loc. cit., p. 341) : " The Lophopus is essentially L. crystallinus, but with a different form of statoblast, so that it is probably a new species ; but this I leave to others who are acquainted with the fresh- water Polyzoa better than myself to determine, merely observing that, should it be considered a new species, the form of the statoblast will afford the chief distin- guishing character. I have not, however, been able to trace the gelatinous envelope, which Professor Allman calls the ectocyst,.

FROM RHODESIA, LOPHOPODELLA THOMASI. 53

beyond the base of the coenoecium, or polypidom, of this Lophopus, where it looks to me like the deciduous tunic of the first or original group, although I have had the opportunity of examining the coenoecium on bodies (the shells of Paludina benyalensis) from which it has never been removed. The group, no doubt, can move from place to place if necessary, but its habit is to remain fixed."

From this short and incomplete description, and considering the shape and character of its statoblast, it is clear that this animal does not belong to, and has no affinity with, the genus Pectinatella, and I have no hesitation to remove it to the new genus.*

In order to give a clear idea of the appearance of the stato- blasts of these various species, I give a figure of those of Lophopodella thomasi and Lophopus crystallinus, drawn for me by Mr. F. R. Dixon-Nuttall, and reproduce the drawings of Kraepelin and Carter for those of Pectinatella magnified and Lophopodella carteri respectively. I may mention here that Allman's figure of the statoblast of Lophopus crystallinus is not quite correct, as the polygonal cells of the annulus are very much smaller than there represented.

I have not in this paper touched upon the anatomy nor the development of the Polyzoa from buds, eggs, and statoblasts. These details can readily be studied in the works mentioned in the bibliography (1, 7, 10, 17, 207\

A few words on the preparation and preservation of Polyzoa may be acceptable. By adopting the following method, little difficulty will be found in killing these animals fully extended. A clean and healthy colony is placed in a watch-glass full of water, and when fully expanded one drop of 1 per cent, solution of cocaine or eucaine ((3) is mixed with the water. After five to six minutes another drop is added, and so on until five or six drops have been added. In twenty to thirty minutes from the

* Since writing: the above I have seen in the British Natural History Museum a slide of this statoblast made by Mr. Carter, from which I observe that its affinity to that of L. thomasi is fully confirmed. The spines are thin, with few hooklets, and vary in number from seven to fourteen on each side ; the latter, shown in Mr. Carter's figure, is probably the greatest number which he observed. • Would it not be possible for some micro- scopist living in Bombay or Bengal to rediscover this animal and send over some well-preserved specimen ?

54 C. F. ROUSSELET ON A NEW FRESH-WATER POLYZOON

beginning, the animals will be narcotised and insensible to needle pricks, and are then to be killed and fixed with a solution of 2 per cent, formaldehyde, 1 part of the commercial solution in 15 parts of water (the solution usually sold being mostly much nearer 30 per cent, than the nominal strength of 40 per cent), to which a veiy little osmic acid solution has been added. After five minutes the Polyzoa are removed and washed in 1 per cent, formaldehyde, and finally preserved in the same fluid.

Bibliography of the More Important Faunistic Papers on Fresh- water Polyzoa since 1856.

1. 1850. Allman, Geo. Jas. u A Monograph of Fresh-water

Polyzoa." London. Ray Society. 11 pi.

2. 1858. Leidy, J. "On Cristatella idae." Proc. Ac. Nat. S'c.

Philadelphia, pp. 188 — 190.

3. 1858. Carter, H. J. " Description of a lacustrine Bryozoon

allied to Flustra (Hislopia)" Ann. Mag. Nat. Hist., ser. 3, vol. i., pp. 169 — 171, 1 pi.

4. 1859. Carter, H. J. "On the identity in structure and

composition of the so-called seed-like body of Spongilla with the winter egg of the Bryozoa." Ann. Mag. Nat. Hist., ser. 3, vol. iii., pp. 332 — 343, 1 pi.

5. 1860. Aplin, 0. D'O. " Fresh-water Polyzoa in Australia."

Ann. Mag. Nat. Hist., ser. 3, vol. vi., pp. 454, 455.

6. 1860. MacGillivray, P. H. " Description of a New Species

of Plumatella." Trans. Boy. Soc. Victoria, vol. v., pp. 203, 204.

7. 1865 — 6. Hyatt, A. " Observations on Polyzoa, Suborder

Phylactolaemata." Proc. Essex Inst., vols. iv. and v. 9 pi.

8. 1866. Parfitt, E. " On two New Species of Fresh water

Polyzoa." Amu Mag. Nat. Hist., ser. 3, vol. xviii., pp. 171 — 173.

9. 1870. Kent, W. S. "On a New Polyzoon Victorella pavida

from the Victoria Docks." Quart. Journ. Micr. Sc, new ser., vol. x., pp. 34 — 39, 1 pi.

FROM RHODESIA, LOPHOPODELLA THOMAS I. 55

10. 1878. Allman, Geo. Jas. " Recent Progress in our Know-

ledge of the Structure and Development of the Phylactolaematous Polyzoa." Joum. Linn. Soc, vol. xiv., pp. 489 — 505.

11. 1879. Leidy, J. " On Cr is tatella idae." Proc Acad. Nat.

Sc Philadelphia, pp. 203, 204.

12. 1883. Leidy, J. " UrnateUa gracilis. A Fresh- water

Polyzoon." Joum. Acad. Nat. Sc. Philadelphia, vol. ix., pp. 5 — 16, 1 pi.

13. 1884. Potts, Edw. " On a supposed New Species of Crista-

tella." Proc. Acad. Nat. Sc. Philadelphia, pp. 193 —199, 1 pi.

14. 1884. Potts, Edw. " On Paludicella erecta." Proc. Acad.

Nat. Sc. Philadelphia, pp. 213, 214.

15. 1885. Jullien, Jules. " Monographic des Bryozoaires d'eau

douce, avec 250 gravures dans le texte." Bull. Soc. Zool. de France, t. x., pp. 91 — 207.

16. 1885. Bousfield, E. C. "The Victorella pavida of Saville

Kent." Ann. Mag. Nat. Hist., ser. 5, vol. xvi., pp. 401—407, 1 pi.

17. 1887. Kraepelin, K. " Die Deutschen Siisswasser Bryozoen.

Eine Monographic, Hamburg." Th. I. 168 pp., mit 7 Tafeln. 1892, Th. II., 67 pp., 5 Taf.

18. 1887. KAFKa, J. "Die Siisswasser Bryozoen Bohmens, mit

91 Abbildungen im Texte." Archiv. Natw. Landesfm*. Bohmen, Bd. VI., No. 2.

19. 1887. Ridley, S. O. " On the Characters of the Genus

Lophojms, with description of a New Species from Australia." Joum. Linn. Soc, vol. xx., pp. 61 — 64r 1 pi.

20. 1890. Oka, A. "Observations on Fresh-water Polyzoa

(Pectinatella gelatinosa)." Joum. Coll. Sc. Imperial University, Tokio, vol. iv., pp. 89 — 150, 4 pi.

21. 1893. Davenport, C. B. " On UrnateUa gracilis." BidL

Mus. Comp.Zool, Harvard Coll.,\o\. xxiv., pp. 1 — 44, 6 pi.

5G C. F. ROUSSELET ON A NEW FRESH-WATER POLYZOON.

i'_'. 1893. Meissner, M. " Eine anscheinend neue Siisswasser Bryozoe (Lophopus jheringi n. sp.)" S. B. Ges. Nat. Fr. Berlin, No. 10, pp. 260—263, 2 fig.

23. 1893. Meissner, M. " Beitrag zur Kenntniss der geographi-

schen Verbreitung der Bryozoengattung Plumatella in Africa." Zool, Anz., No. 430, pp. 385, 386.

24. 1895. Meissner, M. " Die Moosthiere Ost-Afrikas,

Deutsch-Ost-Afrika," Bd. iv., pp. 1 — 7, 1 pi.

25. 1897. Meissner, M. " Weiterer Beitrag zur Kenntniss

der geographischen Verbreitung der Siisswasser Bryozoengattung Plumatella." Zool. Anz., No. 531.

26. 1896. Harmer, S. F. "Fresh-water Polyzoa." The Cambridge

Natural History, vol. ii., pp. 492 — 514.

Explanation of Plate 3.

Fig. 1. Lophopodella thomasl, gelatinous zoarium, with the branch- ing tubes shown at one end only, natural size.

,, 2. Lophopodella thomasi. The branching tubes in zoarium magnified about 5 diam.

,, 3. Lophopodella thomasi. Statoblast, x 50.

„ 4. „ ,, ,, the hooked spines, x 200.

„ 5. ,, „ the hooked spines of an immature

statoblast, x 200.

;, 6. Lophopodella carteri. Statoblast, x about 44. Copy of Mr. H. J. Carter's figure.

„ 7. Lopho])odella carteri. Statoblast, the hooked spines, x 200. Copy of Mr. H. J. Carter's figure.

„ 8. Lophop>us crystalliiias. Statoblast, x 50.

,, 9. Pectinatella magnijica. Statoblast, x 36. Copy of K. Kraepelin's figure.

Figs. 1 to 5 and 8 have been drawn from nature by Mr. F. P. Dixon-Nuttall, to whom I am greatly indebted for the same ; Figs. 6, 7, and 9, are copies from Carter and Kraepelin respectively.

Jouvn. Quekett Microscopical Chib, Ser. 2, Vol. IX., Ao. 54, April 1904.

57

THE PRESIDENT'S ADDRESS.

SOME PLANT DISEASES CAUSED BY FUNGI.

[Resume.)

By George Massee, F.L.S.

(Delivered February 19t/t, 1904.)

Until quite recently, no logical explanation was forthcoming as to why certain fungi are parasitic on other plants. That such parasitism is the outcome of a definite law is obvious from the fact that, although the spores of parasitic fungi will germinate on the surface of any kind of plant, provided it is damp, the germ -tubes only enter the tissues and infect particular species of plants.

As a rule, a given obligate parasite is confined to one, or at most a few closely allied species, and in not a few instances a parasitic fungus is confined in its attacks to a single variety of a species.

The reason for this apparent selection of hosts on the part of parasitic fungi is now attributed to what Pfeffer, a German botanist, called chemotaxis. By chemotaxis is meant the influence exerted over the direction of growth of the germ- tubes of fungi by various substances, which may be of the nature of acids, alkalies, sugars, and various other substances present in the cell-sap of different plants. Towards certain of these substances the germ-tubes of some kinds of fungi are attracted, and pass through the stomata, or even pierce the cell-walls and enter into the tissues of plants. Such substances are said to be positively chemotactic. On the other hand, the germ-tubes of some kinds of fungi are repelled, or prevented from entering the tissues of certain plants, owing to the presence

58 the president's address.

in the cell-sap of a substance which to that particular fungus is negatively chemotactic. Thus it comes to pass, that those fungi whose germ-tubes are attracted by substances present in the cell-sap of a given plant, can enter its tissues and become parasitic upon it ; whereas, on the other hand, those fungi whose germ-tubes are repelled by a substance present in the cell-sap cannot enter the living tissues.

It has been shown that certain bacteria are influenced by chemotactic substances in the same manner as fungi.

It is well known that very different substances are normally present in the cell-sap of different parts of a plant. This probably accounts for the fact that certain fungus parasites are restricted to different portions of the structure. For instance, some fungi are parasitic in the anthers only, others are confined to the foliage, wood, or roots respectively.

In the distribution of fungus spores, wind must be perhaps accorded the first place, although it has been proved in the instances of several serious epidemics that insects are the main agents in carrying spores from one plant to another, and in some fungi special arrangements are present for aiding this object. The most general contrivance of this kind is where the spores of the fungus are imbedded in some sweet substance eaten by insects. In this case the spores pass uninjured through the body of the insect, and are thus distributed.

With these few remarks bearing on the general subject of parasitism, we must now pass in rapid review a few of the most frequent diseases of plants caused by fungi.

Peach Leaf-curl. (Exoascus deformans.)

This parasite attacks the young shoots and foliage, and is recognised by the distorted and curled leaves, which are at first pale green and afterwards tinged red, and covered with

THE PRESIDENT'S ADDRESS. 59

a very delicate bloom, caused by the fruit of the fungus appearing on the surface. The young shoots also become more or less swollen. As the mycelium of the fungus is perennial in the shoots, and advances with each year's growth, from whence it passes into the young leaves, the most certain cure is to prune all diseased shoots and burn the same at once. Even with this precaution, infection may occur the following season from spores that have passed the winter in crevices of the bark, etc. ; hence it is advisable to spray, just when the leaf-buds are expanding, with dilute Bordeaux, mixture.

The leaves of apple-trees and plum-trees are often curled inwards, variously distorted, and reddish in colour, due to a disease which might at first be mistaken for leaf-curl. On unfolding a leaf, however, the true cause of the mischief is seen to be due to plant-lice, or aphides, which will be found in various stages of development. In this case, spraying with one of the many insecticides on the market will be necessary,. and this should be done on the first symptoms of the disease,, as when the leaves are compactly curled the solution does not reach the aphides. •

Mildew7.

This name covers diseases produced by various species of Ert/siphe and allied forms, all of which are characterised by the formation of a white cobweb-like felt on the surface of the foliage of various plants, as hops, peas, vegetable-marrows, etc. When the disease is abundant the leaves present the- appearance of having been whitewashed.

In the majority of kinds of parasitic fungi the mycelium or vegetative portion of the fungus grows in the tissues of the- host-plant, the fruiting portion only bursting through to the surface for the purpose of securing the dispersion of the spores..

60 THE PRESIDENT'S ADDRESS.

In the mildews, however, the whole of the mycelium lies on the surface of the part attacked, and is held in position by numerous suckers or haustoria, which pierce the epidermal cells of the leaf, where they play the double part of anchoring the fungus to the leaf and absorbing food from its cells.

The superficial nature of the mycelium enables the disease to be readily combated if preventive measures are commenced on the early appearance of the mildew. The remedy consists in dusting the plants with powdered sulphur, mixed with about one-quarter of its quantity of powdered quicklime. The dredging should be done in the early morning when the foliage is wet with dew.

Strawberries often suffer severely from one of the mildews {Sphaerotheca castaynei). The leaves are first attacked, and at a later stage the fungus passes on to the fruit, which becomes covered with a white bloom. Such diseased fruit is sometimes dipped in water to remove the fungus and present a saleable appearance, but the watery, insipid taste is sufficient to reveal the deception practised.

Such plants should be treated with powdered sulphur at intervals of eight days until the fruit begins to set. In places where the disease has existed the plants should be covered with a thin layer of straw or other litter, and set fire to. By this means all the old infected leaves, also fragments of diseased leaves lying on the ground, are burned, and the plants afterwards develop vigorous and healthy foliage.

Another mildew, called Sphaerotheca pamiosa, proves very destructive to roses, the leaves and young shoots becoming covered with a white mould. Powdered sulphur, again, is a remedy if applied at intervals after the earliest appearance of the disease. Diseased leaves that have fallen should be collected and burned, otherwise the fungus will mature its fruit on such during the winter, and a fresh infection will follow the suc- ceeding year. Diseased shoots should also be removed.

the president's address. 61

Brown Rot of Fruit. (Sclerot in ia fruct igena. )

This is undoubtedly one of the worst of fungus diseases with which the fruit-grower has to contend, and unfortunately it is always present in more or less quantity wherever fruit is grown. It attacks apple, pear, plum, cherry, and, in fact, all orchard fruits, and is also common on many wild plants belonging to the order Rosaceae.

The young leav7es are first attacked, the fungus appearing on the surface in the form of small, minute, velvety olive- brown patches, which gradually increase in size and grow into each other, until eventually the greater portion of the leaf becomes covered. The spores are carried by rain, wind, insects, etc., from one leaf to another, and at a later stage also on to the young fruit.

On the latter the first evidence of disease is the presence of small brown spots on the surface of the fruit. These spots gradually increase in size, and at a later stage become studded with small whitish downy warts, which constitute the conidial or summer form of fruit, at one time called Monilia fructigeita, before it was discovered to be only one stage in the life-cycle of the higher form of fungus called Sclerotinia fructigena.

On the apple the white conidial tufts are arranged in con- centric circles, being, in fact, miniature fairy-rings, due to gradual extension of the fungus on every side from the point of infection. On other fruits the tufts are irregularly scattered, and not arranged in circles.

Diseased apples do not rot, but shrivel, and remain in a dry, mummified condition throughout the winter, either hanging on the tree or lying on the ground. The following spring, just when the young leaves are expanding, these mummified apples produce another crop of conidia, which are dispersed by various agents, and infection of the young leaves results.

62 the president's address.

Those apples that become buried in the ground, or covered over with herbage, etc., produce at the end of two years, from the same mycelium that previously yielded conidia, a second kind of fruit of a much higher organisation than the conidial form, and the result of a sexual act. This second form resembles in appearance a widely open wine-glass, supported on a long •slender stem, and belongs to the group of fungi called the Pezizeae. The spores of this form of fruit give origin to the conidial condition occurring on the foliage.

As to practical methods of preventing an epidemic caused by this fungus, the trees should be sprayed with a dilute solution of Bordeaux mixture, commencing at the unfolding of the leaves, and repeating at intervals until the fruit is half-grown. Of course, all diseased fruit should be collected and burned.

Journ. Qw/cett Microscopical Club, Ser. 2, Vol. IX., No. 54, April 1904.

63

ON THE PHYLLOPODS LIM MADIA LENTICULARIS (L.)

AND LIMNETIS BRACHYURA (O.F.M.), AND

THEIR OCCURRENCE IN BOHEMIA.

By V. Vavra, Ph.D.

Communicated by D. J. Seourfield, F.R.M.S.

{Read March IStJi, 1904.)

Plate 4.

Limnadia lenticularis (L.)

1761. Monoculus lenticularis, Linne, Faun. Suec, 2nd ed., p. 499 1804. Daphnia gigas, Hermann, Mem. Apt., p. 134, pi. v., f. 4-5. 1820. Limnadia hermanni, Brongniart, Mem. Mus., vi., p. 84,

pi. xiii. 1836. ,, ,, Guerin, Mag. Zool., vii., 1836.

1840. „ „ M. Edwards, Hist. Nat. Crust, iii.,

p. 362. 1849. „ „ Baird, P.Z.S. Lond., p. 86, pi. xi.,

f. 1. 1853. ,, gigas, Grube, Arch., p. 157.

1865. „ hermanni, Grube, Arch., p. 270, pi. viii., f. 9-11.

1866. „ „ Lereboullet, Ann. Sc. Nat., v., p. 383,

pi. xii. 1871. ,, gigas, Lilljeborg, Ofv.K. Vet. Akad. Forh.,~No. 7,

p. 823, pi. xvii.-xviii., A-B. 1875. „ lenticularis, Sahlberg, Om. Finlandsh. k. Phyllo-

poder. Not. F. Fl. Fenn. forh.

N.S., 11, p. 310.

1877. „ „ Lilljeborg, Syn. Fhyll. Suec, p. 17.

1878. „ „ Spangenberg, Zeitschrift iv. Zool.,

xxx., Suppl., p. 474. 1886. „ „ Simon, Ann. Soc. Ent. de France,

p. 436. 1903. „ gigas, Merkel, Mitth, Bad. Zool, Y., No. 16, p. 3.

C4 V. VAVRA OX THE PHYLLOPODS LIMNADIA LENTICULARIS (l.)

As may be seen from the foregoing list of synonyms, this species was described as Monoculu-s lenticularis by Linne. His specimens came from Finland, and it was only because the species had not been found again in that country up to 1871 that Lilljeborg had doubts as to the propriety of retaining the name given to it by Linne. In 1875, however, Sahlberg found it again in Finland, and in 1877 Lilljeborg placed the identity of M. lenticularis (L.) with J), gig as Herm. and L. hermanni Brong. beyond all doubt.

Some examples of this interesting Phyllopod were received by me in June 1899 from my friend Professor F. Klapalek, and immediately afterwards I visited the "spot, near Wittingau, in the south of Bohemia, where they had been found. They occurred in a quite shallow pond harbouring a rich aquatic vegetation, and I was able to collect numerous specimens and thus have the opportunity of watching the living animals. They swim upon their backs exactly in the manner of Branchipus, a fact about which some doubt has been expressed in recent times. When at rest the animals lie upon their sides. The bivalved shell is about 15 mm. long, 10 mm. high, and, seen from above, very narrow, only being about 4 mm. broad. It is highly polished and transparent, with seven or eight concentric lines marking stages in its growth (Figs. «, c).

The body of the animal does not fill the whole of the shell. The rounded head is bent downwards, and is furnished with a pair of large eyes, together with an eye-spot. The swimming antennae are pretty long and powerful, the shorter dorsal branch being usually ten-jointed, and the longer ventral branch eight to twelve-jointed, both being armed with long swimming bristles. On the back of the animal there is a so-called organ of attachment (Haftorgan). There are twenty-three to twenty-four body- segments, and the same number of pairs of feet, of which the first ten are equal in length, while the remaining pairs become gradually shorter. With the exception of the last, the feet carry two branchial appendages.

The ninth, tenth, and eleventh pairs of feet are provided with long thread-like processes (cirri), with which the eggs are held in position on the back (see F'ig. c). The powerful post-abdomen or tail (Fig. d) is toothed on the dorsal edge, and furnished with two plumose bristles. At the end of the tail are two large movable claws, having little spines along their hinder edges.

AND LIMSETIS BRACHYURA (o.F.M.). G5>

Almost all the individuals seen carried eggs in the brood- cavity. These eggs are of a most remarkable form (Figs, e and /). Each egg is globular, with a diameter of 0-13 mm., and its surface is covered with oblique and pretty deep furrows. In addition to this it is clasped by two semicircular girdles, having a breadth of 0*8 mm., and standing at light angles to one another.

The male of Limnadia lenticularis is unknown, and propagation takes place parthenogenetically.

In the same pond with Limnadia lenticularis the following animals were found :

Littoral. Pelac4ic.

Planorbis albus. Volvox ylobator (in great num-

„ nitidus. bers).

( '//clops fuscus. A nabaena flosaq uae.

,, serridatus. Daphnia longispina.

Polyphemus pediculus. ,, penaata.

Sida crystallina. Diaptomus gracilis.

Diaphanosoma brachyurum. Corethra plumicornis (larvae).

Scapholeberis mucronata. Eurycercus lamellatus. ( 'hydorus sphaericus. Ciirvipes rufus

,, conglobatus The Hydrachnidae were determined

Xeiiniaiiia sjnnipes I by Dr. K. Thon.

P rioaocercus uncinatus J Rhipidodendron splendidu ni .

In similar small ponds near Wittingau Apus prod act us is also found, sometimes in great quantities in the spring, for these ponds are dried up during the greater part of the year.

Everywhere Limnadia lenticularis appears to be a very rare form. Linne obtained it from Finland; after 114 years it was found there again, near Helsingfors, by Sahlberg. It has also been recorded from Sweden, Norway, and Denmark ; from C4ermany (Berlin, Breslau, Mainz, Trier, Landshut, Worms, Xeustadt in Mecklenburg, Strasburg, and last year near Walldorf in Baden) ; and from France (near Fontainebleau).

Jourx. Q. M. C, Series II.— No. 54. 5

1875.

>j

1877.

1886.

••

1890.

n

1895.

??

11

66 V. VAVEA ON IIMNAD1A AND LIMNETIS.

Limnetis braehyura (O.F.M.)

1785. Lynmi8 brachyurus, 0. F. Muller, Z??i£. Pern., p. 69, pi. viii.

1847. Limnetis braehyura, Loven, Kgl. Akad. llancll. for 1845,

p. 430.

1848. Hedessa sieboldi, Lievin, Schrift. Ges. Danzig., p. 4. 1853. Limnetis braehyura, Grube, Arch. Nat., p. 156.

P. E. Muller, Nat. Tid., p. 569.

Hellich, Yesmir, t. iv., p. 158.

Lilljeborg, Nova. Act. Ups., iii., p. 18.

Simon, Crust. Phyll., p. 457. ,, Sars, Overs. Nory. Crust., p. 29.

„ Wierzejski, Sprav. Kom. Fyz., t. xxxi., p. 178.

The family of the Limnadiidae contains a second genus Limnetis. The species L. braehyura (O.F.M.) is comparatively small, being only 3 mm. long. The shell is almost globular, smooth and shining, and in outward appearance exactly like the shell of a Cyclas. The head is large ; the first pair of antennae small and two- jointed. According to the investigations of Lillje- borg, there is only one pair of maxillae, as in the Cladocera, while in all the other Phyllopods there are two pairs. This species was found by B. Hellich in material collected in a little pond near Melnik by Professor A. Fritsch, and was described by him in the Bohemian periodical Yesmir, in 1875. Specimens are preserved in the collection of the Prague Museum.

Up to the present time this species has been found in Den- mark, Germany (Danzig), Russia (Archangel, Dorpat, Charkow), Finland, Bohemia, and Galicia (Orakow).

EXPLANATIOX OF PLATE 4.

Fig. a. Limnadia lenticularis ? , lateral view, nat. size. 11 0- ii ii dorsal ,, ,, ,,

, , c. ,, ,, lateral ,, x o.

„ d. „ „ post-abdomen, x 14.

11 eand/ „ ., egg, x 90.

' a. Quekett Microscopical Club, Scr. 2, Vol. IX., No. 54, April 1004.

67

NOTE ON EBONISING LABORATORY TABLES.

By W. J. Wood, F.R.M.S.

{Read October lWt, 1003.)

In the latter part of 1902 and the early part of this year, I fitted out two vessels for the International Sea Fisheries Investigation. The two steamships Huxley and Goldseeker are trawlers specially fitted up for biological and hydrographical research, the Huxley under the management of the Marine Biological Association, with Mr. Garstang as naturalist-in-charge, and the Goldseeker under the Scottish Fishery Board, Professor D'Arcy W. Thompson conducting the scientific work. While fitting out the Goldseeker, Professor Thompson sent me directions for ebonising the labora- tory tables on this ship. The method was so successful that 1 have since ebonised my own microscope work-table at home, and I understand that Mr. Garstang has had the laboratory tables at the Huxley's headquarters, Lowestoft, treated in the same manner. I thought that perhaps this method of treating tables for micro and chemical work would be useful to some of our members, and have pleasure therefore in sending the recipe for publication. My own table-top is of plain teak, and the labora- tory tables of the Goldseeker are yellow pine. Any kind of wood seems to take the stain.

(a) 250 grams of aniline chloride in one litre of water. This solution is applied to the wood every day for two or three days. It must be thoroughly dry before each application.

(b) 125 grams of copper sulphate dissolved in 80 grams of boiling water, and 125 grams of potassic chlorate dissolved by boiling with about 250 grams of water. These solutions are

G8 \\. J. WOOD ON EBONISING LABORATORY TABLES.

mixed together while quite hot, then allowed to cool. Then filter, and dilute the filtrate to one litre. This solution is applied to the wood the same as a, the wood being allowed to dry thoroughly after each application.

(c) At the end of this operation all crystals covering the surface of the wood are to be washed off with clean water.

(d) Once more dry the wood thoroughly and then paint over with cottonseed or raw linseed oil. Leave the oil for one day and then rub dry.

This preparation takes about six days, allowing two days for a, two for b, one for c, and one for d. I found it advisable to rub the table thoroughly with a dry absorbent duster for two or three days in succession, as the oil is not thoroughly removed with one rubbing.

I understand that the tables in the laboratory of the Danish investigation vessel Thor are treated in this manner. The result is a beautiful black surface which will withstand the usual reagents used in biological work.

Joura. <s<"/,<tt Mia-oscopical Club, Ser. 2, Vol. /A'.. No. 54, April U'04.

69

NOTE ON THE SERTULARIIDAE OF KENT AND

SUSSEX.

By Rev. H. A. Soames, M.A., F.RM.S.

{Read January loth, 1904.)

The Sertulariidae, a family of calyptoblastic hydroids, whose representatives are exclusively marine, includes about twenty-five species which occur upon our coasts. For those who live away from the sea-shore the study of the living animal is attended with considerable difficulty ; but the empty receptacles are washed up by every storm, and may be obtained from the refuse of the trawl, and these, occurring as they do in such vast pro- fusion and possessed of so many points of interest, certainly seem worthy of far more attention than they usually receive.

The specimens should be placed, as soon as collected, in methylated spirit, and in this condition will retain their charac- teristics, free from dust and risk of breakage, for an indefinite period. As may be gathered from the following notes, many of the Sertulariidae are commonly met with attached to Algae, Polyzoa, and even to other species of hydroids. The smaller species, especially at an early stage of growth, are easily over- looked, and may often be more readily detected if the object to which they are attached be placed in a jar of water.

The method I personally adopt for the mounting of these hydroids is as follows. The specimen is dried for a few minutes, placed in an excavated cell, covered with a large drop of Canada balsam in chloroform, and thin glass added in the usual way. The slide is then placed under an air-pump, in order to remove the bubbles from the calcycles, the air being exhausted and readmitted several times should it be found necessary. An alternative method, which obviates the necessity of using an air-pump, is as follows. The polypidom is transferred from the spirit to oil of cloves, thence to turpentine, and thence to balsam. The specimen should remain for at least one day in each fluid, and should be transferred with care and rapidity so as to prevent the air from entering the calcycles.

The following is a list of the species I have found in Kent and Sussex : —

70 H. A. SOAMES ON THE SERTULARI1DAE OF KENT AXD SUSSEX

Sertularella polyzonias, Linn.

Common on Flustra, etc. Deal, Sandgate, Bexhill, Dover, Folkestone, St. Leonards. Sertularella rugosa, Linn.

Very common on Flusira. Deal, Sandgate, Bexhill, Folkestone, St. Leonards.

There are four other species of Sertularella which I have not yet found, although S. gayi certainly occurs. Diphasia attenuata, Hincks.

Common on zoophytes, and sometimes on seaweed. It is the only species out of seven that I have at present found. Deal, Sandgate, Dover, Folkestone. Sertularia pumila, Linn.

Very common, especially upon seaweed, whose fronds it often thickly covers. I have not found it upon zoophytes. Sandgate, Bexhill, Heme Bay, Whitstable, St. Leonards, Folkestone.

Sertularia gracilis, Hassall.

Not uncommon on zoophytes and seaweeds, but small and not easily seen. Sandgate, Dover, Westgate, Whitstable, Worthing. Sertularia operculata, Linn.

Found upon zoophytes and seaweeds, often in masses of considerable size. Deal, Sandgate, Bexhill, Dover, Folkestone, St. Leonards, Margate. Sertularia abietina, Linn.

A deep-water form, but large quantities are often cast ashore. Deal, Sandgate, Dover, Folkestone, St. Leonards. Sertularia argentea, Ellis t Solander.

Common. Sandgate, Bexhill, Dover, Whitstable, Folkestone, St. Leonards. Sertularia cupressina, Linn.

Not common. Whitstable, St. Leonards, Sandgate.

S.JUicula and S.fusca I have not at present found. Hydrallmania falcata, Linn.

Very common and characteristic. Deal, Sandgate, Bexhill, Dover, Westgate, Margate, Whitstable, Folkestone, Bognor.

Two species of Thuiaria occur in Britain, but I have not yet found either of them.

If any fellow-members have slides of hydroids which require identification, I shall be happy to assist them to the best of my ability.

J,,.-,-,,. Quekett Microscopical Club, Ser. 2, Vol. IX., No. 54, April 1904.

PROCEEDINGS

OF THE

QUEKETT MICROSCOPICAL CLUB.

At the meeting of the Club held on October 16th, 1903, Geo. Massee, Esq., F.L.S., President, in the Chair, the minutes of the meeting held on June 19th were read and confirmed, and the additions to the Library and Cabinet announced.

Professor Alexander S. Skorikow was balloted for and duly- elected.

The death of Mr. Washington Teasdale, F.R.A.S., F.R.M.S., etc., at the age of seventy-three, was announced by Mr. Freeman, who furnished an obituary notice. Mr. Teasdale was a member of twenty-five years' standing, but, residing at Leeds, he was not of late years a frequent visitor to the Club meetings. In addition to his microscopical studies, he was a devotee to the camera, having taken up photography when that art was in its infancy. He had spent several years in India, and could relate many interesting experiences of Oriental life and customs. To those who were privileged to know him in private life he was a kind and sympathetic friend, ever willing to place his great knowledge at the disposal of the inexperienced. While attending a meeting of the British Association at Southport he had a severe stroke of paralysis, and on September 19th— a week later — a second attack brought to a close his eventful life.

Mr. Freeman also exhibited some exceedingly delicate and skilful microscopic rulings, the work of the late Mr. Teasdale.

Mr. Scourfield, on behalf of Mr. W. J. Wood, read a note on a method of ebonising wood for laboratory tables.

Mr. Frank P. Smith gave an address upon " The Spiders of the Sub-family Erigoninae," illustrated with blackboard sketches and specimens under microscopes.

The President said that the way in which the subject had been

72

dealt with by Mr. Smith left no doubt that there was much more behind it, and this he hoped the Club might be able to draw upon at a future occasion.

At the meeting of the Club held on November 20th. 1903, J. G. Waller, Esq., F.S.A., Vice-President, in the Chair, the minutes of the meeting held on October 16th were read and confirmed, and the additions to the Library announced.

Messrs. G. W. Kirkaldy, William T. Waller, John L. Escudier, and Dr. Arthur B. Griffiths were balloted for and duly elected.

Mr. Karop announced that he had still a number of glass slips for distribution, and had brought them to the meeting so that members could take what they required.

Mr. Langton exhibited and described a portable microscope of his own design and manufacture.

Mr. Karop thought that Mr. Langton deserved great com- mendation for the ingenuity displayed in the construction of this instrument, and regretted that he had laboured under the great disadvantage of being without a lathe.

Mr. Wesche read a note " On the Mouth Organs of Dipterous Flies." The subject was illustrated by diagrams of the mouth parts of various insects, the homologies of which were very clearly pointed out.

Mr. Gleason gave an address on " Amateur Bacteriology," illustrated by lantern-slides. Many forms of bacteria were shown and explained, and also several ingenious pieces of apparatus constructed from the most homely utensils.

At the meeting of the Club held on December 18th, 1903, A. D. Michael, Esq., F.L.S., Vice-President, in the Chair, the minutes of the meeting held on November 20th were read and confirmed, and the additions to the Library announced.

Messrs. F. F. Beckett and F. J. Oxley were balloted for and duly elected.

Mr. Rheinberg exhibited and described a large number of beautiful and curious diffraction plates and gratings.

Mr. Scourfield gave a resume of the third part of his "Synopsis of the British Fresh- water Entomostraca," dealing with the Ostracoda, the Branchiura, and the Phyllopoda. The structure of a typical Ostracod was described and illustrated by means of a diagram.

Mr. Rheinberg read a paper " On an Overlooked Point con- cerning the Resolving Power of the Microscope," illustrated by diagrams and a Grayson ruling exhibited under special apparatus. The paper was followed by a discussion, in which Messrs. Hilton, Rheinberg, Neville, and Stokes took part.

Owing to the lateness of the hour it was decided to hold over a note by the Rev. H. A. Soames "On the Sertulariidae of Kent and Sussex " ; but the President drew attention to the exhibition of slides in illustration of this paper under microscopes provided by the kindness of Mr. C. L. Curties.

At the meeting of the Club held on January 15th, 1904, George Massee, Esq., F.L.S., President, in the Chair, the minutes of the meeting held on December 18th, 1903, were read and con- firmed, and the additions to the Library and Cabinet announced.

Messrs. John H. Pledge, Walter Hunter, John Hopkinson, L. Bulcher, William Cox, and Dr. Thomas B. Sprague were balloted for and duly elected.

The Secretary reminded the members that the Annual Meeting would beheld upon February 19th, and invited nominations to fill the vacancies upon the Committee caused by the retirement by rotation of four members and the resignation of Mr. G. T. Harris. The list of gentlemen nominated as officers for the ensuing year was also read. As an auditor on behalf of the members, Mr. Hicks was proposed and duly elected.

Mr. C. F. Rousselet read a paper " On a New Fresh-water Polyzoon from Rhodesia," illustrated by drawings and specimens.

The President remarked upon the extreme value of a paper of this kind, especially as the known species of Polyzoa were so few and the literature of such a scattered nature.

Mr. Holder exhibited a number of excellent lantern-slides of Foraminifera of his own preparation, the more interesting details being pointed out by Mr. Earland.

74

The Rev. H. A. Soames' note " On the Sertulariidae of Kent and Sussex," held over from the previous meeting, was taken .iv read.

At the Annual Meeting of the Club held on February 19th, 19U4-, George Massee, Esq., F.L.S., President, in the Chair, the minutes of the meeting held on January 15th, were read and confirmed, and the additions to the Library and Cabinet announced

Messrs. J. Burton, L. W. Allardice, C. Graham, A. C. Butter- worth, D. Finlayson, J. W. Page, and R. Gurney were balloted for and duly elected.

The Officers and Council for the ensuing year were balloted for and the result announced.

The 38th Annual Report was read by the Secretary, and the Statement of Accounts by the Treasurer.

The President delivered his Annual Address upon the subject of "Plant Diseases caused by Fungi," the chair being meanwhile occupied by Mr. A. D. Michael.

A hearty vote of thanks was accorded the President, who then introduced his successor, Dr. Edmund J. Spitta. In a short address, Dr. Spitta expressed his intention of doing all within his power for the welfare of the Club, and the meeting terminated with the usual conversazione.

< 0

THIRTY-EIGHTH ANNUAL REPORT.

Your Committee is again able to report favourably upon the Club's progress during the past year.

During the twelve months ending December 31st, 1903, thirty- three new members were elected. This may be considered a very satisfactory total, as it represents the average number elected during the last ten years, which include the two remark- ably prosperous years, 1901 and 1902, during which the large number of ninety-nine new members were elected. Twenty-six members have been lost owing to resignation or removal, and four have died. Three of these were old members of the Club, Mr. J. W. May having joined so far back as May 1871, and Mr. W. Stuart Smith in August 1872 ; while the third, and perhaps the best known, Mr. Washington Teasdale, had been a member since August 1878. The total number on the books of the Club on December 31st was 379, as compared with 370 in the previous year.

The attendance, both on " gossip " nights, and at the ordinary meetings, has been quite up to the average of previous years, and the Club is probably favoured with larger gatherings than any other society of its kind in London. The number and quality of the exhibits also show no signs of falling off.

The chief communications read at the meetings of the year are as follows : —

Jan. The Male Organs of Scatophaga

lutaria and S. stercoraria . Mr. Wesche.

Some points in the Structure

and Life-history of Diatoms. Mr. Rowley.

Synopsis of the Known Species of British Fresh-water Ento- mostraca. — Part T. Cladocera Mr. Scourfield.

On the Larva of an Hydrachnid found in the Stomach of a Trout ..... Mr. Soar. Feb. President's Address on Fermen- tation and Putrefaction . Mr. Massee.

••

J5

76

March Pocket Magnifiers . April Further Observations on Male Rotifer- ....

5'

May June

>>

Oct.

Nov. Dec.

D

Remarks on the Emission of Musical Notes by Eristalis

i (' 1 1 ff.i , • • • •

On a method of taking Internal Casts of Foraminifera .

Two new Commensal Bdelloida.

Two new species of Philodina.

On Abbe's test of Aplanatism and a simple Apertometer derived therefrom

Synopsis of the Known Species of British Fresh-water Ento- mostraca. — Part II. Cope- poda .....

Spiders of the Sub-family Eri- goninae ....

Amateur Bacteriology

Synopsis of the Known Species of British Fresh-water Ento- mostraca. — Part III. Os- tracoda, Branchiura, and Phyllopoda ....

On an Overlooked Point con- cerning the Resolving Power of the Microscope

Mr. Karop.

Messrs. Marks and YVesche.

Mr. W. II. Harris.

Mr. Quilter. Signor Pio-\ Mr. Bryce.

Signor Piovanelli.

Mr. Cheshire.

Mr. Scourfield.

Mr. F. P. Smith. Mr. Gleason.

Mr. Scourfield.

Mr. Rheinberg.

The Committee begs to thank the members who have com- municated their investigations to the Club.

The following books, periodicals, and transactions of learned societies have been added to the Library during the past year : -

Cross & Cole's Modern Microscopy. 3rd edition. Dr. Braithwaite's British Moss Flora. Part 22. Missouri Botanical Garden Report, 1903. Smithsonian Annual Reports. American Jlotaaical Gazette.

77

Proceedings of Academy of X at aval Science of Philadelphia.

Journal of Applied Microscopy.

Journal of the Royal Microscopical Society.

Proceedings of the Royal Society.

Journal and Proceedings of the Royal Society of New South. Wales.

JSTewstead's British Coccidae, Vol. 2. Ray Society.

Michael's British I'yroglyphidae, Vol. 2. Ray Society.

Quarterly Journal of Microscopical Science.

Annals and Magazine of Natural History.

British Museum Handbook of Instructions for Collectors.

Proceedings of the Geologists' Association.

Sundry other Proceedings and Transactions, and various pamphlets.

The Committee have much pleasure in announcing that the Honorary Librarian has completed a new Catalogue of the works in the Club's Library in three sections — Authors, Titles, and Journals of Scientific Societies. The Catalogue has been printed, and is now on sale at the price of Is. The publication of this Catalogue will undoubtedly greatly enhance the value of their Library to the members, and the Committee do not doubt that members will cordially appreciate the completion of their Librarian's task, the labour of which has been greatly increased by the inadequate accommodation at his disposal.

The Journal has been issued with the usual regularity, and the October number marks the completion of the eighth volume of the Second Series. The Committee regret to announce that Mr. Scourfield finds himself unable to continue the office of Editor, owing to pressure of other work, and in accepting his resignation the Committee desire to place upon record their cordial appre- ciation of his services, and of the uniformly high standard maintained by the Journal during his four years of office.

It is, however, most desirable that the members should realise that the present high standard of the Journal is attended by a correspondingly high expenditure, and even under the existing conditions, could only be maintained so long as the membership remained at its present figure. A reference to the Balance Sheet will show that the Club's income is practically absorbed by two items, rent and the expenses of the Journal. In view of

78

a probable increase in the Club's rental, it may be necessary to diminish the expenditure upon the Journal, unless the income of the Club can be correspondingly increased. The Committee therefore trust that all the members will take an active interest in a matter so vital to the welfare of the Club, and endeavour to increase the membership by bringing the Club under the notice of their acquaintances. The advantages offered to the amateur microscopist in return for a very moderate subscription are so obvious that a large influx of new members would undoubtedly result from such advertisement, and this would render it possible to meet the increased expenditure without diminishing the present high standard of the Journal.

The Honorary Curator reports an increased demand for the loan of slides from the Club's cabinets. During the past year over 2,000 slides have been borrowed, and the number would doubtless have been still larger but for the cramped conditions under which the Curator is unfortunately compelled to work. One hundred and twenty-four slides have been presented, and seventy-six purchased out of proceeds realised by the sales of Catalogues. With the object of further extending the usefulness of the Cabinets, five series of slides on Botanical Histology have been prepared. A key to each series, explaining the chief points of interest, and illustrated by diagrams, has been written by Mr. R. Paulson. The best thanks of the Club are due to this gentleman for the careful and instructive way in which these notes have been compiled.

The number of members who have attended the Excursions during the past year is higher than in any previous year since 1893. In 1893 the total number of attendances was 124 ; in the past year the total number was 117, or an average number of 13 for each of the nine excursions. The excursion to the Royal Botanical Gardens was, as usual, the best supported ; in spite of the weather no less than 32 members attended. A new locality, viz. "Wallington, Surrey, was visited in the excursion of July 11th, which was attended by 9 members, who spent an enjoyable afternoon collecting in the private grounds of Mr. Christy and Mr. Maitland. The thanks of the Club are due to these gentlemen for the privilege thus afforded. The excursions were well patronised by the new members, to whom the experience thus obtainable should be specially valuable.

79

The finances of the Club are in a sound condition, and there is very little in the Balance Sheet requiring comment. The amounts received from subscriptions and from the sales of Catalogues show a slight increase, which is nearly balanced by a slight decrease in the receipts from advertisements. The balance in hand— viz. £190 9s. 3d. — shows an increase of <£22 4s. 5d. on the balance at the end of last year, but as the greater part of this increase may be considered as already earmarked for the cost of printing the Catalogue of Books, the balance may be regarded as nearly the same as last year.

The Committee desires to express its thanks to the officers for their individual and collective services, on which the efficiency of the Club so largely depends. In this connection they desire especially to draw the attention of all members to the loss which the Club is sustaining in the retirement of their Honorary Secretary, Mr. G. C. Karop, who, after more than twenty years of devoted service to the Club, is now resigning his office.

*/*

■:■.

80

j c

oq "m

T C'

3: X

rc

t

•pi 0

w

x O

.

. CM

CM X

to o

in t>

STi-

rH

- r1

CD «

e<0

-

/. _

pH —

1— H

■ O

5»

C3

=* 2

t^ cc

— 1^

-u

Ci re

E 03

O

•»o

—

PQ

su

1

02 S3

N

o

s3"

2

-1-3

-t-3 r— ■

<

:

•

"

•

-i-i

/.

• >-H

"d O

CM

O

CM

.—J D

_ 1 —

£2 ox

o

rt

#

r-> .

—1

—

z o

X

z

x CO x

M

0 0

.

>> '■

03

;

C

0 0

•

x O O

=rt 0

O O 1— 1

1 c8

XX

r " r_"

-

—>

—

c —

o s^

r^

CO

1— (

re

:3 X

*•*

H

o

o

Ph

O

— '

O '

•-a

c

DC

03

02 05

g 3

5

• 1— 1

ea • -^

ri S3

-'. - e t3

- 03

• S -1-3

03

02 "Tj

03 •!— 1

g X

- — 1 —

^ M

1— i

'"C

• l-H

S3 03

(—1

c3

PQ

a

+3

5 0

03 O

X

:

•

•

S 0 p 2

3-

=

5 | j

~ 0

Ph <j

03 O s\ FY**

— H 1— 1

r— 1

;

;

1^

t>s

- -

p p

£ £

-

3

X 03

Eh

G>

#

.

.

<- S3

w

rrt O

cm cm

1-1 CO

OS 0

^

X

:

:

:

s >

r-

* -0

O rH

— '

03 .£

—

*§

/ f

o oo

r- cc

O M

1 — 1

>

k>

rH

G S3

15

•Ji

H

~

^^

^

•

0

:

OG

H

- O

<1

MS

i— I

CD X X

—

CM Ci

!— 1

0

C32

hH

tf2

'o

Of

0 X

eg

• 1— 1

O

Sh -U

0J

0

Ci of

03

• 1— 1 -I-3

• pi

1 03

S— 1 -I-3 03

C >

0) M 03

a >

S3 r3

CO

i— i

o

OS

i— I X

c

0

<1

+3 . 1

03 03

1

C3

I

1 1

X

-t-J

r- 1

>— *

^1

> ^

O H

X

<

X

Ci 1— 1

&H -

X

<!

X

CM

> "-H 03 fl

• «

03

0 g

-t-3 03

• r-H

« "E

^ S3

a)

CO

&

Hoi CM

03 O

03 CM

03 O

Pi 03

CM

^ s

S3 'S-

~*. ci

^3 03 Pi

C CO

* ^

o

O O

n

s >

.5 'TJ

>— ' l«=H

=

r

0j

o

CO

E 03

o ..

— —

1?

+3 in

rt 0

x 0

X " (M

tJH

'i-s

^ P^

a5

^.1

^»

co

o

— C

«4-t ««-( O O

- /.

iH 03

»—

7 "^

X DO

r- 'Z

so ES

5»

-

r

— >

a 03 X X

0

X Ph

0)

■?

H

»

" *■

^ *~

+3

Jourx. O.M.C

Ser. 2, Vol. 9, PI. 1

Frank P. Smith, del. ad nat.

Cephalo-thoraces of Male Erigoninae.

Jourx. O.M.C

Ser. 2, Vol. 9, PI. 2.

D. J. SCOURFIELD. del.

Belisarius viguieri. Cyclops nanus.

Journ. O.M.C.

Ser. 2, Vol. 9, PI. 3

JW '■ ■■•

e«

1

5

. - f

'?£ k

vr

,/

/-

I

V.

-

1

-

- -

9

""

>^

)

M _ «* Jar

-? •-' ' 54;/

F. R. Dixon-Nuttall, del ad nat.

LOPHOPODELLA THO.MASI. GEN. & SP. NOV.

Jourx. O.M.C.

Ser. 2, Vol. 9, PI. 4

c^>

me*

\%

CD

00

V. Vavra, Je/.

LlMXADIA LEXTICULARIS.

SI

THE GENITAL ORGANS OF TAENIA SINUOSA

By T. B. Bosseter, F.R.M.S.

(Read March 18th, 1904.)

Plate 5.

Taenia sinuosa, Zeder (Diijardin).

1782. Taenia collar i-nigro, Block.

1782. „ infundibidiformis, Goeze.

1786. „ collaris, Batsch.

1790. „ torqttata, Ginelin.

1800. Alyselminthus sinuosus, Zeder.

1800. Taenia breviarticulata, Goeze.

1803. Halysis sinuosa, Zeder.

1803. Halysis torquata (Gmelin, 1790). Zeder, vide Bud, 1810.

18-45. Taenia sinuosa, Diijardin.

1858. Hymenolepis sinuosa, Weinland.

1869. Taenia sinuosa, Krabbe.

1893. Drepanidolaenia sinuosa, Railliet

1903. Taenia sinuosa, Bosseter.

From the time that Block (1782) found this worm parasitic in the intestine of Anas boschas fera, until Krabbe (1866) took it from Anas boschas dom., much uncertainty seems to have existed as to the true character and identity of this avian helminth. Krabbe, following Dujardin's determination of Zeder 's Taenia sinuosa, adopted the same, and this basis is likewise adopted by the author of this memoir.

Dujardin's description is as follows : —

" Long de 50 a 160 mm. (a 330 mm., Bud), capillaire en avant, large de 2*25 mm. en arriere ; tete presque globuleuse avec un prolongement conique tubuleux, plus on moins saillant qui contient la trompe ; trompe retractile, aussi longue que la tete, mince,

•Journ. Q. M. 0., Series II. — No. 55. 6

•< S

82 T. B. ROSSETER OX THE GENITAL ORGANS OF TAENIA SINUOSA.

renflee a l'extremite, et armee de dix crochets tres-longs (de 0*04:0 a 0042 mm.), tres saillants, presque droits; cou tres-long ; les articles males trapezoi'daux ; derniers articles (androgynes ou femelles) plus ou moins arrondis ; orifices genitaux unilateraux ; appareil male forme d'un testicule blanc ou jaun&tre opaque, situe transversaleinent au milieu de chaque article, avec une tige cornee mince, contenue dans un tube herisse de poils et dirige transversalement vers l'orifice genital : a cote de cet orifice se trouve un sac interieur globuleux, tout herisse cle poils ou de petites epines, et paraissant comme un point noir sur le cote de chaque article (d'oii resulte une ligne de points noirs tres reguliere). Je l'ai trouve assez communement a Rennes dans l'oie et le canard " (Duj. Hist, ties Helm., p. 573, No. 35, T. sinueux).

The specimens upon which I have been working were taken from the intestine of a duck (Anas boschas dom.) fed artificially by me on cysticercoids (Cystkercus sinuosa) taken from the Beverley dairy-farm pond in the parish of St. Stephen's, near Canterbury. The result of feeding was not so successful from the point of view of growth as was anticipated ; nevertheless, the object in view — namely, the production of the mature worm from the cysticercoids for the study of the organs of generation — was obtained. This sets at rest in connection with this avian tape- worm the views expressed at different times by O. von Haman, Von Linstow, Mrazek, and myself, that the cysticercoids found in Copepods by the former, and by myself in Ostracods, were the cystic scolices of Krabbe's T. sinuosa. and of which Stiles, in his work on The Tape-worms of Poultry, said, " For the want of experimental infection is problematical and not positive."

Although this platyhelminth has been known for the past century and a quarter, and studied by various eminent helmintho- logists, yet, hitherto, the organs of generation have been very inaccurately described and imperfectly portrayed.

Bespecting the external form of this tape-worm, I am in accordance with Krabbe in accepting Dujardin's determination of Zeder's T. sinuosa ; but the description of the internal anatomy will be taken from notes and observations made from my own

T. B. ROSSETER ON THE GENITAL ORGANS OF TAENIA SINUOSA. S3

prepared and mounted specimens. Dujardin gives the length of this tape-worm as from 50 mm. to 160 mm. The Zeder- Rudolphi specimen -was 330 mm. My longest specimen produced by infection was 18 mm. Thus it will he seen that it has no pretensions to the length of the Zeder-Rudolphi or even the Dujardin specimen; but it is a perfect worm, minus the uterine sac with the uterine eggs.

Male Organs.

The male genital pore (Fig. 1, d) — I use it in the singular — is unilateral, and is situated on the anterior lateral border of the segment. It is cup-shaped ; its orifice has a diameter of '026 mm., and the diaphanous cup has a depth of about '065 mm., and is easily overlooked. The male organs are situated well up in the anterior portion of the segment, being overlapped somewhat considerably by the posterior transverse border of the preceding segment. They consist of a cirrus, with its sheath, a vesicula seminalis, a vas-deferens, a monoecious testis, and paired prostate glands. In a mature specimen the proglottis is 325 mm. long, and in width 1 "747 mm. anteriorly, and 1*976 mm. posteriorly.

The testis (Fig. 1, a) is a subglobular organ, having an approximate diameter of *162 mm. In those young segments which are approaching maturity it appears to be situated in the centre, or nearly so, of the anterior portion of the pro- glottis ; but as the segment develops, and with it the generative organs, the testis gradually moves backwards towards the anterior distal lateral border, on its dorsal side immediately over the distal end of the receptaculum seminis. The growth of the spermatozoa within the spermatic sac is analogous to — in fact, is a counterpart of — the development of the spermatozoa of T. coronula, with this exception, that the bundles of spermatozoa do not form coils or strands, but are passed on individually through the vasa-efrerentia to the vesicula seminalis. The head of the spermatozoon is a spatulate cell containing a cellule or nucleus of plastic substance easily stained by either haemalum or haematoxylin, whilst the

84 T. B, ROSSETER OX THE GEXITAL ORGAXS OF TAENIA SIKUOSA.

cell itself, being structureless, remains in a perfectly hyaline condition. Ordinarily this spatulate head of the spermatozoon wraps itself round until if forms a blunt-pointed spathe (Fig. 2, b), and this no doubt is its normal condition when it meets and penetrates the ovum in the fructifying canal.

On leaving the testis the vasa-efferentia curves sharply but gracefully upwards, and becomes a sinuous vas-deferens (Fig. 1, 6), running distally and proximally in the segment, and ultimately becomes a sac within the vesicula seminalis. In young specimens this sac is very pronounced, and may be beautifully demonstrated by the aid of haemalum.

The vesicula seminalis (Fig. 1, c) is situated in the dorso -anterior portion of the proglottis. Its distal end is rounded, whilst its proximal end elongates itself to form the cirrus-sheath. It is an elongated pyriform sac, "35 mm. in length and "065 in breadth.

The cirrus-sheath is, normally, '13 mm. in length, but during the act of coition it exserts itself to *212 mm. Its mean width is '016 mm. Externally it is hispid, but internally it is smooth. The cirrus (Fig 1, e) is a long, hollow, smooth, diaphanous, flexible tube, and, when exserted for the purpose of coition, has a length of "23 mm., and is 2 /x wide.

Below the male genital pore, somewhat anterior of the plane of the cirrus-pouch, is what, under a low power, appears to be a dark punctate spot or point. This is not seen in the early or young proglottides, but makes its appearance as the male organ approaches maturity, and continues to increase in size until the male organ has attained its perfection. Seen under a ^-inch objective it is a globular spinous sac (Fig. l,f), with a round, smooth, diaphanous collar, somewhat similar to a collared monad. It is hollow, and the endoderm is smooth,, although punctate. These punctuations are at the bases of the spines. In some proglottides it appears as if the cirrus with the proximal end of its sheath passes through its centre. Such, however, is not the case, for it lies dorsal of that organ, and is easily dissociated, by teasing, from the cellular tissue in which it is embedded.

One cannot refer with any certainty farther back than Dujardin respecting the knowledge of the existence of this spinous body

T. B. ROSSETER ON THE GENITAL ORGANS OF TAENIA SINUOSA. 85

in the structure of this particular platyhelniinth, and we have only one other instance of it occurring in the Cestoidae — viz. in Krabbe's Taenia frag His, which he took from Anas crecca. No mention is made of this dark point by Rudolphi, in his synopsis, and Zeder's drawings of the generative organs do not contain it (Fig. 4). From the days of Dujardin and Stiles no explanation has been given as to what part this spinous body plays in the structural economy of this particular helminth. The hispid (spinous ?) cirrus-sheath is of common occurrence, and armed suckers occur in Davaniae cchinobothridae and Echinocotylus rosseteri, each having their uses — the former to assist in the act of coition, and the latter to anchor the scolex in the mucous membrane of the intestine ; but this globular spinous sac performs no such function. How, then, are we to explain its presence, and what inferences are we to draw as to its utility in the structural economy of tape-worms ? In my opinion we must look backwards for a solution of the problem.

The more one studies and considers the class Cestoidae from a taxonomist's point of view, the more one is brought face to face with the question, " Have the Cestoidae advanced or retro- graded in the law of evolution ? ': I cannot think, as some eminent histologists have thought and at the present day do think, "that nature, having once made a step forward by the -creation of cell tissue, reverts under circumstances inimical to its environment to the original form." If we advocate and concede this theory in the lower forms of life, we must admit the same causation in the other orders of nature, for one law governs the whole, and the law of adaptability, in no matter what form, or under what circumstances, is but an empty theory. For instance, Trichodina pediculus, considered essentially an ectoparasite on the tentacles of the fresh-water polypes Hydra fusca and H. viridis, and sometimes on the branchial appendages of the larvae of Triton cristatus, loses none of its ectoparasitic characteristics on becoming an endoparasite on the urinary organs of the adult Triton cristatus, having migrated there through the gill slits during the act of absorption of

86 T. B. ROSSETER ON THE GENITAL ORGANS OF TAENIA SINUOSA.

the branchiae (see Rosseter on " Trichodiria as an Endoparasite,"' Journ, R. M.S., Ser. 2, Vol. VI., 1886, p. 929). The fact of these platyhelminths being endowed with organs of generation which, although hermaphroditic, are comparable favourably with the bisexuality of the higher orders of nature, and are yet anenterons, does not necessarily imply that they previously were enter iticr but having by disusage, caused possibly by their surrounding- environments, lost the organs of nutrition, from this cause had thus retrograded in the scale of life. Far from it : I main- tain that these platyhelminths never possessed an enteron. No matter what stage of segmentation in the strobila you examine, no trace of such a tract can be found existing, or as having existed, in their cellular tissue. I have looked in vain in prepared and stained sections, and have never been able to resolve Pagen- stecher's narrow space within the muscular layers {Taenia critica) which he would represent as the body cavity ; neither can the " anlage " of the digestive apparatus (?) be traced in the embryo or hexacanth stage. Nor is the saccular cavity of the cyst (Cysticercus) to be looked upon as an enterocoele ; it is merely the blastomeric cavity of the forming strobila. Thus we are forced to consider this cavity as a blastocoele ; consequently, it has never arrived at, much less passed through, in the law of development, the gastrula stage. Looking at it from this point of view I arrive at the conclusion that a close affinity exists between the Cestoidae {Taenia si?iuosa) and the Porifera- Spongidae. One can trace this affinity backwards through Twrbellaria convoluta, which, like the Cestoidae, ingests its sus- tenance through the endodermal parenchyma ; likewise in the Discophora, in which is foreshadowed by the agamogenetic multi- plication of the colonies by fission, into eight-lobed discoidal medusoids {Medusa bifida), the future strobila of the Taenidae ; and finally in the lowest groups of the Metazoa, the Porifera,. the cellular tissue of the one is structurally the counterpart of the other. That which I wish chiefly to draw attention to, however, is the spiculiferous character of the Porifera and its relationship, or affinity, in this respect, with the Cestoidae,. more particularly as regards Taenia sinuosa.

T. B. ROSSETER ON THE GENITAL ORGANS OF TAENIA SLXL'OSA. ST

The skeleton of the calcareous sponges consists, as is well known, of an aggregation of separate spiculae which are deve- loped exclusively in the ectoderm, and is not, according to Huxley, supported by any framework of animal matter. This statement is equally applicable to the Taenidae, for these spiculae of T. sinuosa, although appearing, when viewed by a 1-in. objective, en masse, yet when they are examined with a \-in. objective and separated by pressure from the globular mass, are seen to be totally distinct from each other. The globulous mass of spiculae is formed between the ectodermal structure or cortical layer and the middle layer. It is easily detached, and then does not carry adhering to it any of the surrounding cellular tissue, thus showing that it is not supported by the same. Thus I look upon this globulous dark point of Dujardin — seeing that it plays no known part in the structural economy of the creature — as a spiculiferous relic, pointing out to us that the Cestoidae are closely allied to the Porifera. This may in some measure explain the views of Yon Siebold as to the calcareous corpuscles which are present in such abundance in the proglottides of some species of Taenia more than in others, being skeletal, and not, as Claparede thought, " the result of an excretion." This affinity is more emphasised and strengthened when we consider and contrast the origin and formation of the spermatozoa and ova in the Porifera and Cestoidae, for the calcareous sponges, like the Cestoidae, are hermaphroditic, and their reproductive elements are spermatozoa and ova ; and whilst it is assumed, for the want of positive evidence, that the former in the calcareous sponges originate in metamorphosed cells in the endoderm, it is a demonstrable fact that such is their origin and development from the endoderm of the middle layer of the proglottis in the Cestoidae, whilst the ciliated embryo of Bothriocepltalus latus, minus its six embryonic hooks, is but the counterpart of that of Ascetta mirahilis. Thus I am inclined to the opinion that the Cestoidae have not undergone retrogression, but that they have always been, in conformity with their environment, as we now find them,

" anenterous."

s8 t. b, rosseter on the genital organs of taenia 8inu0sa.

Female Organs.

Of the 115 to 120 species of avian tape- worms figured and de- scribed by Krabbe in his Bidrag til Kundskab om Fuglenes Baenddorme, 18G9, there are only four in which he foreshadows the female genital organs — viz. T. microcantha, T. capito, T. villosa, and T. shmosa — and even then in a very imperfect manner. If we refer, in the case of T. sinuosa, to his sketch of these organs, Tab. 7, fig. 153 (Fig. 5), we find merely the outline of certain bodies, but nothing to indicate their individuality or functions. I take them to represent the receptaculum seminis, paired ovaries, and the shell and yelk glands. An undulating filiform streak is seen passing dorsally of the vesicula seminalis, but there is nothing to lead us to infer that it has any connection with or plays any part structurally in the genital apparatus ; yet, on close examination, we find that the contra is the case, and that it does play a most important part and is an essential portion of the female genital organs. In fairness to Krabbe it must be admitted that these organs, however obscurely sketched and unexplained by him, are to some extent accurately placed in the outline of the sketched segment.

In this species the female genital pore (Fig. 1, h) is quite distinct from that of the male. It is situated in the same plane, dorsally, but not on the lateral border. Its position is in the median line, 0'1G3 mm. from the lateral border. Thus it is some distance down the segment, and it is instructive to note the manner in which the whip-like cirrus, when exserted from the male pore for the purpose of coition, glides from the lateral border down the segment to the female genital pore. The vulva has a diameter of "026 mm. The vagina is diaphanous and smooth both externally and internally. The vaginal canal (Fig. 1, i) — which the thin undulating line drawn by Krabbe across the vesicula seminalis in his sketch of the genital organs evidentally is meant to represent, although not described by him as such — runs obliquely, not undulatingly, dorsally over the vesicula seminalis far up under the lappet of the preceding segment, and is thus very much obscured and •difficult to trace. It is then suddenly diverted, and returns

T. B. ROSSETER ON THE GENITAL ORGANS OF TAENIA SINUOSA. 89

•ventrally under the distal end of the vesicula seminalis and joins the receptaculum. seminis.

The receptaculum seminis (Fig. 1, j) is a triangular sac with rounded corners at its base. The vaginal canal enters it at its apex. It has a length of "227 mm., and its base is "097 mm., its basal angle being thus more contracted than the lateral angles. It is situated in the anterior distal portion of the proglottis, ventral to and immediately under the moniliform testis, and under such circumstances it is somewhat difficult to discriminate between them. Its efferent canal leaves it on the ventral side, runs backwards, then sharply curves round and passes on to join the ovarian ducts.

The ovaries (Fig. 1, V-l") are two orbicular lobed glands, situated proximally and distally in the ventral posterior portion of the segment, and have a mean diameter individually of '211 mm. Their ducts coalesce with the duct of the receptaculum seminis, and thus form the fructifying canal, which descends into the yelk gland.

The yelk gland (Fig. 1, m) is situated anterior to, and the shell gland (Fig. 1, ri) posterior to, the ovaries, in the median line of the proglottis. The former is globular, and the latter, being pyriform, runs distally, and is partially obscured by the posterior portion of the distal ovary.

I have not had the opportunity to study the uterus with its uterine ova, in consequence, as so often happens in experimentally bred platyhelminths, of the segments not having arrived at the •uterine stage of development.

Explanation of Plate 5.

Fig. 1. Male and female genital organs in situ, x 155 : a, testis ; b, vas-deferens ; c, vesicula seminalis ; d, male genital pore ; e', cirrus extruded ; e', cirrus- pouch ; f, spiculiferous globule ; g'-g', prostate glands with their ducts ; h, female genital pore with vagina ; i, vaginal canal (Krabbe's thin undulating streak) ; j, receptaculum seminis ; k, efferent duct of recepta- culum seminis or fructifying canal, making a junction

90 T. B. ROSSETER ON THE GENITAL ORGANS OF TAENIA SINUOSd.

with oviducts 1 and 2 ; I', proximal, l', distal ovaries ;

m, yelk gland ; n, pyriforin shell gland ; o, uterine

canal. Fig. 2. a and b, spermatozoa.

„ 3. Transverse section through spiculiferous globule, x 350. „ 4. Two segments enlarged ; aa, bb, the vermiform sacs ;

cc, cirri ; d, posterior corners of segments. (After

Zeder, 1800, Tab. 3, tig. 10.) „ 5. Segment with genital organs and extruded cirrus ; the

thin undulating line a (the vaginal canal, Rosseter) is

seen crossing obliquely the vesicula seminalis (after

Krabbe, Tab. 7, fig. 153); x 35. „ 6. Cirrus, x 210, Dujardin, Hist, des Helminthes, 1845,

Plate 9, fig. d.

Journ. Qv.ckctt Microscopical Club, Ser. 2, Vol. IX., No. 55. November 1904.

91

SOME NEW SENSE-ORGANS IN DIPTERA.

By W. Wesche, P.R.M.S.

{Read April loth, 1904.)

Plates 6 and 7.

Investigations into the sensations of creatures so far removed from the mammalia as insects are hampered by the possibility that these animals may possess (in the words of Lord Avebury) " senses and perceptions of which at present we have do conception." *

It is true that in man we have something in the extreme cultivation of particular senses which may help us to imagine other perceptions in insects. For example, the man who is only a little musical has no conception of the joy, pleasure, or rapture (words or combinations of words cannot express the feeling) that can be experienced on hearing a fine orchestra perform, in an ideal manner, the masterpieces of Beethoven or Wagner. The trained eye sees colour and beauties in nature which the untrained eye cannot discern, and the masterpieces of painting probably afford pleasure to those who have a highly cultivated colour sense as much as the great tone poems afford to these who have a highly cultivated musical understanding. There is an anecdote of the great painter Turner which well illus- trates this. A critic remarked that he could not see in a landscape the blues and greens, the scarlets and yellows, that Turner had sketched upon a canvas. " But don't you wish you could ? " was the answer of the artist. In matters in which cultivation plays no part, also, we have analogies. The call or cry of the bat, being a most acute sound, is beyond the capacity of the normal human ear, which can only appreciate a little more than 35,000 vibrations in a second of time ; but there are persons who can hear this shrill sound without effort, and it is only by reason of the existence of such abnormal persons that the majority of human beings know the bat has a voice.

Through the anatomical and experimental investigations of many entomologists, it seems clear that we can localise the seat>

* Senses of Animals, -p. 193.

92 W. WESCHE ON SOME NEW SENSE-ORGANS IN DIPTERA.

of touch, or feeling, and vision with exactness, as all imaginal insects can feel through the hairs and bristles embedded in their chftinous coverings, and nearly all can see by means of their eyes, simple or compound ; while there is little doubt but that most, if not all, can smell. What is the exact seat of the organ of scent, however, is not determined, as while the antennae have been proved in some species to be the chief centre of excitation of the olfactory nerves, the palpi, and even parts of the body, may support organs sensitive to smell.

Professor Packard has found sense-pits on the palpi of Perla * which he thinks may be organs of taste, though he quotes Platen, Will, and Forel as having proved that in the Wasps and Ants the palpi have no gustatory function. Little is known as to these organs of taste, but it is evident that they exist in those insects which feed in the imaginal state, and must be situated in the mouth, or in its immediate neighbourhood. In Diptera they are said to be seated in the labella (paraglossae), and as far as my observations go this seems probable, except in those genera such as Chironomus, Psychoda, and Oestrus, in which many species do not feed in the imaginal state, but whose mouth-parts, except in the Oestridae, seem quite adapted for use.

Lord Avebury t quotes Kraepelin as finding certain peculiar club-shaped hairs at the end of the proboscis of the humble-bee (Bombns), which he considers to be taste hairs ; F. Will as thinking certain pits on the maxillae of a wasp {Vespa vulgaris) to have the same use — these he calls taste cups ; and Leydig, Meinert, Lowne, Kraepelin and others as considering as taste hairs two rows of minute pits, with a central papilla, situated on the proboscis of the hive bee (Apis melifica).

I have examined these structures with modern objectives, and I remain very sceptical as to the uses of one of the parts. The humble-bees of which I have preparations in my cabinet only show Kraepelin's club-shaped hairs in one species ; but the mere fact that they are not present in all the species of a genus militates against regarding them as characteristic sense-organs. Further, all these insects, including the possessor of Kraepelin's " club-shaped hairs," have the taste hairs on the labium exactly similar to, and obviously homologous with, those of the hive bee,

* Textbook of Entomology, 1898, p. 272. f Senses of A id in als, p. 28, 29.

W. WESCHE OX SOME NEW SENSE-ORGANS IN DIPTERA. 93

which, as I said before, Leydig. Meinert, Lowne and Kraepelin consider to be taste hairs.

As to Will's "taste cups" on the maxillae of wasps, I consider them as modified taste hairs. This is obvious in the maxillae of the hornet, where are found structures similar to Will's, and others, more modified, showing the gradations between this and a structure which is considered by Kraepelin as a " taste organ " in the Muscidae (PI. 6, Figs. 4, 5). On the ligulae and paraglossae of Vespa vulgaris and V. crabro I have found chitinous discs, one on each part.

In the worker of V. vulgaris there is a peculiar structure- consisting of a series of papillae connected at their bases, and having hollow hairs or pegs inserted at their apices (PI. G, Pig. 1). These are on the basal sides of the discs, which are on the extremities of the ligulae and paraglossae. In the queen - wasp and the hornet the same structure is found, but on the anterior side of the discs (PI. 6, Fig. 3). These are most characteristic structures, and if they could be found in several families and orders they might be considered as typical taste organs. I think I can fulfil these conditions if the papillae are separated.

I have found a single, somewhat similar structure on the maxillary palpus of A. melifica (PI. 6, Fig. 6), on the paraglossae of Blatia oriental-is, cockroach (PI. 6, Fig. 9), and on the labium of Panorpa communis, scorpion-fly (PI. 6, Fig. 10); these have been combined with similar structures smaller in size (Figs. 7, 8). If PI. 6 be examined, gradations will be found from the papilla and hair on the disc in Vespa, to the very short papilla and hair situated in rows between the pseudotracheae in Musca. Kraepelin * distinguishes four kinds of hairs on the proboscis of Musca.

1. Ordinary hairs, which are not hollow and are not in con- nection with a nerve.

2. Hairs of touch, connected with a nerve.

3. Glandular hairs, whose existence has been called in question.

4. Taste organs, which lie in a row between the trachea-like channels, and correspond to the similar organs in the bee.

* "Zur Anat. unci Phys. des Paissels von Musca," Zeit. fur Wiss. ZvoL, 1883.

94 W. WESCHB ON SOME NEW SENSE-ORGANS IN DIPTERA.

I therefore conclude that all these structures in Blatta, Ajris, Vespa, Paaorpa, and Musca are " taste hairs" and homologous, and that Will's "taste cups " are misnamed, being only modifications of the characteristic hair.

One can now say that the sense of taste in insects is conveyed l>y a blunt, hollow, rather characteristic peg or hair, which may be (1) scarcely showing, as in Will's organ; (2) longer, as in the structures on the maxillae of V. crabro and the labium of some Dipteia ; (3) nearly double the length of the socket, as on the discs of the labium of V. vulgaris and V. crabro. This hair is loosely fixed in the socket and rather long when on the labium of the Hymenoptera, but shorter when on other parts, and in Diptera. The socket may be quite long, as in the labium of Vespa, shorter but still evident, as in the Muscidae, or only perceptible, or even sunk to the level of the epidermis, as on the maxilla of Vespa. This is but an amplification of Lord Avebury's able generalisation when he concludes, " that the organs of taste in insects are certain modified hairs, situated either in the mouth itself, or on the organs immediately surrounding it." *

There is a conflict of opinion on the subject of hearing, for though some tympanic organs in stridulating insects, such as locusts or crickets, have been thought to be auditory organs, Forel,f whose opinion has much weight, denies that these tympanic organs are necessarily ears, and thinks that all insects, possess no special organ of hearing, but that sounds are perceived by their tactile organs, just as deaf mutes can detect at a dis- tance the rumbling of a carriage. If this opinion is correct, all insects would hear, as all can feel, and it has been demonstrated that some insects, if not the majority, are, as far as can be ascertained by experiment, quite deaf.

What we know about the Culicidae (Gnats) agrees with M. Forel's idea. The hairs on the antennae of the males vibrate •sympathetically if a tuning fork, giving a note near to that of the " pipe " of the female, is sounded near them. On the other hand, a number of experienced entomologists, have separately come to the conclusion that auditory organs exist in the antennae of many species, and the deep pits or cavities in the antennae

* Senses of Annuals, p. 31.

f Recueil Zoologique Suisse, 1887.

W. WESCHE ON SOME NEW SENSE-ORGANS IN DIPTEKA. 95

of the Muscidae are thought to be such. This part, then, may be a tactile, an auditory, or an olfactory organ in different species, and it is probable that in many instances all three senses are located, perhaps not exclusively, but in part, in the antennae. Professor Packard* says that, "the ears of the locusts are situated one on each side, on the basal joint of the abdomen just behind the first abdominal spiracle. In Meconema a European grasshopper, the auditory organs are on the fore- tibiae." I shall show that I have found in several Empidae, an organ in the same situation, the use of which I shall discuss later.

Without in any way calling in question Packard's conclusion as to Meconema, I would observe that in one case, where a structure on the fore-leg was thought to be an auditory organ, this explanation was quite wrong. The combed process, fringing a concavity of the fore- tibia of very many Hymenoptera, is the instance alluded to. Mr. Frank Cheshire found that it was used to clean the antennae, and it seems absolutely clear that this is its proper function.

Lieut.-Col. Yerbury, to whom I am indebted for several specimens of the insect, has drawn my attention to the very marked powers of smell of Gastrojihilus equi, L., one of the Oestridae, or bot-flies. He tells me that his method of cap- turing the insect was, on a sunny day, to take up a position on the windward side of a cart-horse ; generalh^ after a short time a bot-fly would come up on his leeward side ; often both Col. Yerbury and the horse would hear the fly before they saw it, and invariably the fly came up the wind, and was seen first on the opposite side of the horse. This shows a very highly developed sense of smell, equal to that of many of the mammalia, or even greater if we compare the surfaces exposed. I therefore made preparations of this insect, and examined every part of the external anatomy with a view of finding special olfactory organs. I used an excellent i-in. objective, which, working at an unusual distance, affords great assistance to an entomologist.

The result was negative for all parts except the antennae.

I then examined these, comparing them with those on flies

of about the same size. They were very distinctly larger than

those of Helophilus penduhis, L., Thelaira nigripes, F., and

* Texthooli of Entomology, pp. 288, 289,

96

W. WESCHE OX SOME NEW SEXSE-ORGAXS IN DIPTERA.

CalUphora erythrocephala, Mg., and about the same size as- Echinomyia /era, L. I have made an exact comparative measurement, by drawing these antennae with squares in the eye-piece of the microscope, and the result will be seen on Fig. 1, below. Further, I found on the third joint of the antennae of G. equi a larger number of sense-pits than on any of the flies mentioned, and of a different structure. When I say sense-pits I do not mean the minute perforations, 17,000 of which are said to be on the antennae of the blow-fly, but a much larger and more evident structure. This, which I have illustrated on Plate 7, Figs. 4, 6, 7, is, owing to the diffraction produced by

Fig. 1. — Antennae of Diptera.

1. Helqphilus pcndulus, L.

2. Gastrophilus equi, F.

3. Echinomyia f era, L.

4. Thelaira nigripes, P.

5. CalUphora erythrocephala, Mg. G. Stratiomys chameleon, L.

the different layers, very difficult to make out ; without a powerful sub-stage condenser, and strong illumination, the details are invisible, and even with them the short rods or pegs on the membrane do not show, but take the appearance show in Fig. 6. Owing to one of the larger pits being on a fractured edge, I was able to see these short rods and indicate them in my diagram. The structure then consists (a) of a large number of hairs which are on the outer surface ; (b) under these are

W. WESCHE ON SOME NEW SENSE-ORGANS IN DIPTERA. 97

pits, a few larger than the others, the larger being gl^ to y-^- of an inch at their widest part, their shape being oval, but more irregular than that shown in the diagram; (c) these pits are covered with a delicate transparent membrane and appear to be enclosed in a thicker or darker ring than the surrounding chitin. This darkness, however, is possibly an optical illusion produced by the angle at which the object is seen ; (d) on the larger pits are from six to ten short styles or pegs.

On PL 7, Fig. 7, I have drawn a diagram of the structure as I imagine it to be when seen in section. This has analogies with Kraepelin's diagram of the organs of smell on Melonatha as given in Packard,* except that in the latter there is only one style on the membrane, whereas in G. equi we find many. The pits when seen from the opposite or inner side showed the appearance drawn in Plate 7, Fig. 6, and some of the holes for the insertion of tae styles were distinctly rectangular.

At the base of the arista I discovered a sense-organ (PL 7, Fig. 5), somewhat different in detail, which may not be of the same function as those on the third joint. This had five styles on the membrane, and was y-Vo of an inch in diameter ; it was surrounded by a chitinous ring, but had no fine hairs round it. I looked for similar structures on the Muscidae, but failed to see any.

On the third and fourth joints of the antennae of Stratiomys chameleon, L., I found an analogous structure, with a layer of rather more chitinised rods covering the pits, which were disposed as shown in the diagram (Fig. 1, No. 6). The larger pits are y-Vo °f an incn ni diameter, and contain a varying number of styles. Why S. chameleon has this remarkable structure on the antennae is not obvious. I am told it spends a rather sluggish existence in the neighbourhood of the water, where its larval state was passed. The mouth-parts are suctorial, with the maxillae in a very atrophied condition. If the organs described are olfactory, and we cannot be sure that they are such, probably the high development of this sense enables the fly more readily to find its mate. As these flies are not particularly abundant, such a character would be of value. Apart from the special case of S. chameleon, the whole family of the Strat'omydae has very marked antennae, with numerous and

* Textbook of Entomology, p. 275.

Journ. Q. M. 0., Series II. — No. 55. 7

\)S W. WE3CHE ON SOME NEW SENSE-ORGANS IN DIPTERA.

very visible sense-pits, but not exactly similar in structure to those on S. chameleon. Mr. E. E. Austen has described some on Pachygaster meromeloena, Duf.,* and I have found similar sense- pits in Chloromyia formosa, Scop., Pachygaster leachii, Curt., Microshrysa polita, L., and M. Jiavicornis, Mg.

To sum up the matter, we find in G. equi an insect with a highly developed sense of smell, large antennae, with sense- organs larger than those in S. chameleon and other flies, some of these latter-being known to possess a keen olfactory sense. On the other hand, we have a somewhat similar structure in S. chameleon, of which we have no record that it has a sense of smell, but of which I show that it would be of advantage to possess such a sense ; we now see that the balance is in favour of the affirmative proposition. If we add to this the large amount of evidence recorded by Lord Avebury in Senses of Animals, and Professor Packard in the Textbook of E ' utomology, we get something which is not far from reasonable proof that the antennae carry olfactory organs. The palpi have been regarded as tactile organs, and there is little doubt but that they, in common with the antennae, share this sense. Being •so intimately connected with the mouth, they have been thought to be the seat of the sense of taste. This has been disproved in the case of ants and wasps. These insects, after being deprived of their palpi, still rejected meal mixed with quinine and morphia, though readily feeding on unadulterated meal. I have already shown that in the wasps the taste hairs are on the labium and maxillae, and it is an interesting confirmation of Forel's experiment that I can find none of these organs on the labial or maxillary palpi. As Lord Avebury has continually emphasised in his Senses of Animals, what applies to one genus will not always apply to another, and I have, as already stated, found taste hairs on the labial palpi of A. melifica.

On the second joints of the palpi of Bibio hortulanus, L., are sense-organs of a very marked type, pits surrounded by ciliated rings of chitin, and on the membrane, stretched across the pits, wrhat appear to be styles or pegs. These I regard as olfactory organs for the following reasons : —

1. The structure is similar to, or has analogies with, that which we find on G. equi.

* Entomological Magazine, 1901. p. 24.".

W. WESCHE ON SOME NEW SENSE-ORGANS IN DIPTERA. 99

2. Similar organs are to be found in a large number of the Nemocera, Simulium reptans, Rhyphus fenestndis, and many- others. These insects have not highly developed sense-pits on the antennae.

3. Pipimculns zonatus, Z., which has small and characterless third joints of the antennae, has a well-marked sense-organ on the tip of each palpus.

4. Ocidromia glabricula, Fin., has large sense-organs on the palpi, thjq- of an inch in diameter. The antennae are pilose, having no sense-organs or pits larger than rroV o °^ an incn in diameter ; the third joint is only -ji^ of an inch in width and g-|T of an inch in length.

Weighing these facts, I think that where the antennae are not particularly sensitive, the palpi have this structure to com- pensate. We thus see that the palpi, like the antennae, can bear organs of three senses — touch, taste, and smell ; but I do net think that any one palpus has more than two of these senses developed at the same time.

I now come to certain sense-organs which I have found on the legs of many species, but of whose function T can form no idea.

These consist of a membrane enclosed by a chitinous ring ; on the membrane are a number of smaller rings, each support- ing a delicate, sharply pointed hair. The enclosing ring of the specimen figured in PL 6, Figs. 15, 19, is ^-^ of an inch in diameter. For the sake of convenient reference I shall call this " Structure A." It is situated on the inner side of the trochanter of the middle leg of Aphrosilus raptor, Hal., and on the same place in Poecilohothrus nobilitatus, L., is a homologous organ. These are exceedingly delicate structures, placed in well- protected spots, and probably capable of recording very slight impressions.

On the opposite side of the trochanter is a cluster of pits without setae, and having below it a semicircular thickening of the chitin (PL 6, Fig. 18). This I will call "Structure B."

I have also found Structure A in two places at the base of the second joint of the antenna of A. ruelijica, on workers and drones, Tiy by —^ of an inch in size ; on the same place on the queen, but not arranged in ovals ; and also in front

100 W. WESCHE OX SOME NEW SEXSE-ORGAXS IN DIPTERA.

of the fore-coxae of Ocidromia glabricula, Fin. and on the trochanters of the