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THE

JOURNAL

OF

THE LIINEAN SOCIETY.

ZOOLOGY,

VOL, XXXII,

LONDON:

SOLD AT THE SOCIETY'S APARTMENTS, BURLINGTON HOUSE,

PICCADILLY, W.,

AND BY ,

LONGMANS, GREEN, AND CO., ^^^-r:^4-

WILLIAMS AND NOEGATE.

1911-1916.

Dates of Publication of the several Numbers included in tbis Volume.

No.

211,

pp.

1-58,

published July 20, 1911.

;;

212

59- 86,

V

October 23, 1911.

M

213,

87-120,

jj

September 24, 1912.

5>

214,

121-162,

))

December 17, 1912.

)?

21o,

163-194,

May 16, 1913.

J)

216,

195-232,

»

October 25, 1913.

»

217,

233 306,

>)

June 30, 1914.

M

218,

307-416,

))

September 21, 1914

)>

219,

417-456,

j>

July 27, 1915.

))

220,

457-512,

7>

September 30, 1915

)>

221

513-530,

Jf

July 25, 1916.

Index, Title-page, etc.

PRINTED BY TAYLOR AND FRANCIS,

BED LION COURT, FJjEET STREET.

LIST OF PAPEKS.

Page Bagn'All, Richard Siddoway, F.L.S.

On the Classification of the Order Symphyla 195

On a Collection of Thysanoptera from the West Indies, with Descriptions of New Genera and Species. (Plates 48 & 49, and 2 Text-figures.) ... 495

Baylis, Harry Arnold.

Some Observations on the Tentacles of Blennius gattorugine. (Commu- nicated by Prof. G. C. Bourne, F.R.S., Sec.L.S.) (Plates 22 & 23, and 1 Text-figure.) 295

Bourne, Gilbert Charles, M.A., D.Sc, F.R.S., F.L.S.

A Description of Five new Species of Edwardsia, Quatr., from New Guinea, with an Account of the Order of Succession of the Micro- mesentei'ies and Tentacles in the Edwardsidse. (Plate 51, and 2 Text- figures.) 513

See Baylis, H. A.

See Liddell, J. A.

See RoBSON, G. C.

Brown, James Meikle, B.Sc, F.L.S.

Observations on some new and little-known British Rhizopods. (Plate 9.) 77

IV

Page Oalman, William Thomas, D.Sc, F.L.S., F.Z.S.

On Apheocaris. nom. nov. (Aphareus, Paulson), a Genus of the (Jrustacean Family Sergestida?. (Plate 16.) 219

Chilton, Charles, M.A., LL.D, D.Sc, M.B., CM., F.L.S.

A new Aniphipodan Genus and Species \_Syndexamine carinatco] (Family Dexaminidje) from New Zealand. (Plates 26 & 27.) 331

Some Terrestrial Isopoda from New Zealand and Tasmania, with De- scription of a new Genus [IVotoniscus']. (Plates 36 & 37.) 417

/)eiJo, a Subantarctic Genus of Terrestrial Isoi^ods. (Plates 39 & 40.) ... 435

Collinge, Walter Edward, M.Sc, F.L.S., F.E.S.

On the Range of Variation of the Oral Appendages in some Terrestrial Isopods. (Plates 20 & 21.) 287

Description of a new Genus and Species of Terrestrial Isopoda from British Guiana \_Calycuoniscus]. (Plate 50.) 509

Davidson, James D., M.Sc, F.E.S.

On the Mouth -parts and Mechanism of Suction in Schizoneara laniyera. (Communicated by Dr. A. D. Imms, F.L.S.) (Plates 24 & 25, and 2 Text-figures.) 307

Foot, Miss Katharine, and Miss E. C. Strobell.

Results of Crossing E^ischisius variolarius and E uschistus servus, with reference to the Inheiitance of an exclusively Male Chai'acter. (Com- municated by Prof. E. B. Poulton, F.R.S., Pres.L.S.) (Plates 28-34, and 2 Text-figures.) 337

Results of Ci'ossing two Hemipterous Species, with reference to the Inheritance of two Exclusively Male Characters. (Communicated by Prof. E. B. Poulton, F.R.S., Pres.L.S.) (Plates 41-47.) 457

Friend, Rev. Hilderic, F.L.S., F.R.M.S.

Some Annelids of the Thames Valley. (With 3 Text-figures.) 95

Gilchrist, John Don Fisher, M.A., B.Sc, Ph.D., F.L.S.

A Free-swimming Nauplioid Stage in Pcdinurits. (With 1 Text-figure.) 225

Herdman, Prof. AVilliam Abbott, D.Sc, F.R.S., F.L.S.

A Comparison of the Summer Plankton on the West Coast of Scotland with that in the Irish Sea. (With 8 Text-figures.) 23

V

Page Herdman, Prof. William Abbott, D.Sc, &c. (cont.).

On the Occurrence of AonjiMdiniatn o-perculatum^ Clap. & Laclim., in vast Quantity at Port Erin (Isle of Man). (Plate 8.) 71

Spolia Runiana. I. Funicidina quadrangularis(Psi\\iis)iind the Hebridean Diazona violacea, Savigny. (Plates 13 &> 14, and 2 Text-figures.) 163

Spolia Runiana. II. Fanicidiiia quadrangidaris (Pallas) ; Diazona violacea, Sav. ; Forbesella tessellata (Forbes) ; variation in Ascidians ; and records of rare Invertebrata. (Plate 19.) 269

Hill, John Peter, D.Sc, F.L.S., see Wilsmore, Mrs. L. J.

Imms, Augustus Daniel, B.A., D.Sc, F.L.S., see Davidson, James D.

Jordan, Karl.

Observations on certain Names proposed in Dr. Verity's paper on the Rhopalocera Palsearctica in the Collection of Linnajus. (Communi- cated by the President.) 1 93

Liddell, J. a.

Nitocrameira bdellurce, nov. gen. et sp., a Copepod of the Family Cantho- camptidse, parasitic in the Egg-cases of Bdellura. (Communicated by Prof. G. C. Bourne, D.Sc, F.R.S., F.L.S.) (Plates 10 & 11, and 2 Text-figures.) 87

LoNGSTAFF, Mrs. James, F.L.S.

On a Collection of Non-Marine Mollusca from the Southern Sudan : with Description of New Species by Hugh B. Preston, F.Z.S. ; and Notes on Veronicella, by G. C. Robson, B.A. (Plates 17 & 18, and 2 Text-figures.) 233

Meek, Capt. Charles Francis Ullathorne, F.L.S.

The Spermatogenesis of Stenohothrus virididus ; with special Reference to the Heterotropic Chromosome as a Sex Determinant in Grass- hoppers. (Plates 1-3, and Text-figure.) 1

The Correlation of Somatic Characters and Chromatin Rod-lengths, being a Further Study of Chromosome Dimensions. (With 5 Text-figures.) 107

Poulton, Edward Bagnall, M.A., D.Sc, F.R.S., Pres.L.S.

W. A. Laml^orn's Breeding Experiments upon Acrcea encedon (Linn.), Trimen, in the Lagos District of West Africa, 1910- 1912 391

See Foot, K., and E. C. Strobell.

See Jordan, K.

See Yerity, R.

VI

Page Peeston, Hugh Berthon, F.Z.S., see Longstaff, Mrs.

Rgbson, Guy Coburn.

On a Collection of Land and Freshwater Gastropoda from Madagascai-, with Descriptions of new Genera and new Species. (Communicated by Prof. G. C. Bourne, F.R.S., Sec.L.S.) (Plate 35, and 6 Text-figures.) 375

See Longstaff, Mrs.

Shelford, Robert Walter Campbell, M.A., F.L.S.

The' British Museum Collection of Blattidre enclosed in Amber. (Plate 7.) 59

Smith, Geoffrey Watkin, M.A., F.L.S.

The Genws Lernceodiscu.s (F. Miiller, 1862). (Plate 38.) 429

Strobbll, Miss E. C, see Foot, Miss K.

Verity, Roger, M.D., F.It.E.S., F.Fr.E.S.

Revision of the Linnean Types of Palaenrctic Rhopalocera. (Communi- cated by the President.) 173

Wailes, George Herbert, F.L.S.

Freshwater Rhizopoda and Heliozoa from the States of New York, New Jei\sey, and Georgia, LT.S.A. ; with Supplemental Note on Seychelles Species. (Plate 12.) 121

Freshwater Rhizopoda from North and South America. (Plate 15.) 201

WiLSMOEE, Mrs. Leonora Jessie, M.Sc.

On some Hexactiniae from New South Wales. (Communicated by Prof. J. P. Hill, D.Sc, F.L.S.) (Plates 4-6, with a Text-figure.) ... 39

Vll

LIST OF THE PLATES.

Plate

1-3. Spermatogenesis in /S'ie?ioJoiA?'?{s.

4-6. New Hexactinise.

7. Blattidse in Amber.

8. AtnpMdinium operculaticm.

9. British Rliizopods,

10, 11. jYitrocrameira hdelhirce.

12. Rhizopoda and Heliozoa.

13, 14. Diazona.

15. Rhizopoda from North and South America.

16. Ajjhareocaris.

17. Map showing localities of Mollusca.

18. Mollusca from White Nile.

19. Spolia Runiana.

20. 21. Oral Appendages of Isopoda. 22, 23. Tentacles of Blennius.

24, 25. Schizoneitra lanigera.

26, 27. Syndexamine carinata, nov. gen. et sp.

28. Easchistus variolarhis, E. serrns and hybrids.

29-33. F., Hybrids from E. variolarius and E. serrns.

34. E. variolarius males and males from F^ $ x E. variolarius.

35. Gastropoda from Madagascar.

36. 37. Terrestrial Isopoda.

38. Lernwodiscus, F. Muell.

39, 40. The genus Deto, Guerin.

41. Intromittent Organs from Euschistus variolarius, E. servus and hybrids.

42-46. Intromittent Organs from F., hybrids from E. variolariu,s and E. serv^is.

47. Intromittent Organs from E. variolarius males and males from F^ 5 X E. variolarius S .

Trinidad Thysanoptera.

Isojood from Guiana : Calycuoniscus.

New Species of Edwardsia, Quatr.

vm

ERRATA.

Page 53, line 26, for Calli<Ttis read Calliactis. 69, line 2, for Pleriplaneta read Periplanela. 128, line 7, for Tellomy.va read Pelomyxa. 157, line 20, for tuherosa read tubulosa. 179, line 3, for 7'. read CitUosune. 273, line 4, read iV". romeri (Neugeboren), Brady. 380, line 2, for T. ligatiwi, Miiller, read T. ligata (O. 1'. i)f «//.). 380, line 4, for balteatxtm, Sozverby, read balteata, (Sowerby). 385, line 25, for evimia read eximius. Plates 4-6,/r7/' HEX ACTING, re.7cZ HEX ACTINIA. 26 & 27, rf«f/ nov. gen. et sp, 34, for X read x .

48 & 49, transpose the numbers ; in tlie plate originally nnnibered 49 (now 48), add 7 to the top right-hand figure above fig. 15, and the ocelli now numbered 14 should be corrected to 4.

July 20.

Price 85

THE JOURNAL

OF

THE LINNEAN SOCIETY.

Vol. XXXII.

ZOOLOGY.

No. 211.

CONTENTS.

Page I. The Spermatogenesis of Stenohothrus viridulus ; with Special Reference to the Heterotropic Chromosome as a Sex Determinant in Grasshoppers. By Capt. C. F. U. Meek, F.L.S. (Plates 1-3, find text-figure.) 1

11. A Comparison of the Smnmer Plankton on the West Coast of Scotland with that in the Irish Sea. By Prof. W. A. Hekdman, D.Sc, F.R.S., F.L.S. (8 text-figures.) 23

III. On some Hexactinife from New South Wales. By Leonoka J. WiLSMORE, M.Sc, Zoological Laboratory, University College, London. (Plates 4-6, with a text-figure.) (Communicated by Prof. J. P. Hill, D.Sc, F.L.S.) 39

LONDON :

SOLD AT THE SOCIETY'S APARTMENTS, BUKLINGTON HOUSE, PICCADILLY, ^N., AND BY

LONGMANS, GREEN, AND CO.,

AND

WILLIAMS AND NORGATE. 1911

.<^^

^^sonian insti/,^

ibii f

SEP 29

LINNEAN SOCIETY OF LONDON

LIST OF THE OFFICERS AND COUNCIL.

Elected 24th May. 1911.

PRESIDENT. Dr. Dukinfield H. Scott, M.A., F.R.S.

Sir Frank Crisp, J.P, Horace W. Monckton, F.G.S.

VICE-PRESIDENTS.

I Prof. E. B. PoultoQ, F.R.S. I Dr. A. B. liendle, F.R.S.

TREASURER. Horace W. Monckton, F.G.S.

SECRETARIES.

Prof. A. Dendy, D.Sc, F.R.S. | Dr. Otto Stapf, F.R.S.

GENERAL SECRETARY. Dr. B. Daydon Jackson.

COUNCIL.

Prof. V. H. Blackman, Sc.D.

Henry Bury, M.A.

Sir Frank Crisp, J.P.

Prof. Arthur Dendy, D.Sc, F.R.S.

Prof. J. Stanley Gardiner, M.A., F.R.S.

E. S. Goodrich, F.R.S.

Henry Groves, Esq.

Prof. W. A. Herdmac, F.R.S.

Arthur W. HiU, M.A.

Dr. B. Davdon Jackson.

Horace W. Monckton, F.G.S.

Prof. F. W. Oliver, F.R.S.

Prof. E. B. Poulton, F.R.S.

Dr. A. B. Rendle, F.R.S.

Dr. W. G. Ridewood.

Miss E. R. Saunders.

Dr. Dukinfield H. Scott, F.R.S.

Dr. Otto Stapf, F.R.S.

Miss Ethel N. Thomas, B.Sc.

Dr. A. Smith Woodward, F.R.S.

LIBRARIAN. A. W. Kappel.

CLERK.

S. Savaofe,

LIBRARY COMMITTEE.

Officers ex officio, with the following in addition :

E. G, Baker, Esq. L. A. Boodle, Esq. J. Britten, Esq. H. Bury, M.A. Prof. P. Groom, D.Sc.

G. E. Nicholls, B.Sc. R. I. Pocock, F.R.S. Hugh Scott, M.A. Miss A. L. Smith.

THE JOURNAL

OF

THE LINNEAN SOCIETY,

(ZOOLOGY.)

The Spermatogenesis of Stenohothrus inridulns ; witli Special Reference to the Heterotropic Chromosome as a tSex Determinant in Grasshoppers. By Capt. C. F. U. Meek, F.L.S.

(Plates 1-3.)

[Read 1st December, 1910.]

Inteoduction.

Since Van Beneden discovered in 1883 that the somatic number chromo- somes is halved in the mature germ-cells of both sexes, the attention of investigators has been turned to the phenomena of the maturation divisions and to the problems to which they give rise. The literature upon spermato- genesis and oogenesis has become very extensive^ and it is impossible to discuss here the numerous questions that have arisen during the last few years. I shall therefore touch only upon certain points of controversy, directly concerned with the morphology and function of the chromosomes.

Although the halving of the somatic number of chromosomes is no longer denied, considerable disagreement exists as to the manner in which reduction is effected. In the eumitotic type of maturation^ both mitoses are regarded as being equational; but the majority of cytologists uphold the doctrine of pseudomitosis, in which one maturation division is reductional. They have, however, not decided whether this division is the first or second ; and in this way the rival theories of Pre-reduction and Post-reduction have arisen.

The researches of vom Rath in 1892-5 upon the spermatogenesis of

LINN. JOURN. ZOOLOGY, VOL. XXXII. 1

2 CAPT. C. r. U. MEEK ON THE

Gryllotalpa led him to assert that the first maturation division is longitudinal, the second being transverse and reductional ; and McClung's paper upon Bippiscus in 1899 has corroborated this view. Further evidence in support of the theory Post-reduction has since been supplied by the work of Sutton upon Brachystola magna, and by the more recent investigations of Nadine Nowlin and Robertson upon Melanoplus bivittatus and Sijrhula admirabilis respectively. On the other hand, de Sinety, in a paper upon the Phasmidse, has declared that both maturation divisions in the Orthoptera are longitudinal and equational. In 1905 Montgomery, writing on Syrhula, and Farmer and Moore, writing on Periplaneta, upheld the theory of Pre- reduction ; and this view has since been adopted by Davis in a paper upon the Acrididge and Locustidee, and by Gerard in a paper upon Stenobothrus bigiittuhis. The studies of Sutton upon Bi^acliystola magna led to certain discoveries with regard to the chromosomes themselves : firstly, he found that they exhibited a remarkable degree of isolation, for each became enclosed in a distinct vesicle during the telophase of the secondary spermatogonial mitosis. These vesicles fused later at one polar extremity, with one exception to which I shall allude. Since the chromosomes remain in compartments during resolution into spiremes, he has concluded that their individuality is never lost, and that they are morphologicall}^ independent units : this phenomenon has been observed by Otte in Lucusta viridissima, but is apparently confined to a small number of organisms. The nucleus at this stage usually exhibits a long, continuous, and highly convoluted spireme, or even a complete reticulum, formed by the combined resolution of the chromatin filaments ; Grerard describes this condition in Stenobothrus biguttulus, in which he finds no trace of separate vesicles.

Sutton further discovered in Brachystola that the chromosomes of the spermatogonial complex invariably show certain size and shape relationships, and that, with one exception, they can be arranged in a graduated series of, pairs : this has since been corroborated in other types by the work of Baumgartner, Davis, Gerard, McClung, Montgomery, Nowlin, Robertson, the Schreiners, Stevens, and Wilson, He found moreover that these relationships persist in the later spermatocytes, and, since the number of chromatin bodies is halved at this stage, concluded that a conjugation of members of the spermatogonial pairs had occurred during the intervening period. This view is now held by the majority of cytologists ; and Otte says that he has actually witnessed a side to side conjugation of chromosomes in Locusta. Bonnevie, Sainmont, Wilson, and von Winiwarter carry the theory even further, for they believe that there is complete fusion of the associated chromosomes during this period of lateral juxtaposition ; on the other hand, the entire theory of conjugation is denied by Duesberg, Fick, Gerard, and Meves.

This theory has been eagerly seized by Meudelians to explain the

SPERMATOGENESIS OF STENOBOTHRUS VIRIDULUS. 3

segregation of character factors necessary to that mode of inheritance : the members of each spermatogonia! pair are assumed to be respectively paternal and maternal in derivation, so that the juxtaposition of their component chromomeres permits the exchange of character factors obtained from the two parents. This is merely an hypothesis, but there seems to be little doubt that the number and size and shape relationships of the chromosomes are constant for the species ; and it is probable that we shall eventually find morphological correlation between the complexes of allied members of a group.

Lastly, there is the problem of the heterochromosomes, investigated originally by Wilson, and divided by him into three classes idiochromo- somes, heterotropic chromosomes, and microchromosomes. The first-named consist of two elements, differing in size and staining deeply during the resting stages and growth period of the primary spermatocytes ; they later conjugate, and still later divide, the larger passing to one pole and the smaller to the other. The oogonia show a corresponding pair of chromo- somes, but in this case both are of the same si^e. Spermatozoa possessing the larger idiochromosome produce females, those possessing the smaller produce males. The heterotropic chromosome occurs in the spermatogonial cell as a single element, and behaves like the ordinary chromosomes in the second maturation mitosis, but passes entire to one daughter cell at the first. As in the case of the idiochromosome, it is represented in the oogonia by a pair. Spermatozoa containing the heterotropic chromosome produce females, and those without it males. Wilson has suggested that, in the male, it acts as a male determinant, and that it passes from one sex to the other alternatively, being recessive in the female : Hertwig, Paulmier, and Wassilieff regard it as a degenerating chromosome that will eventually become extinct a view strongly opposed by McClung.

In 1899 McClung drew attention for the first time to this peculiar chromosome in the male germ-cells of XipUdium ; and it has since been studied in a large number of organisms, particularly Orthoptera. He found that it undergoes no resolution into a spireme during the primary spermatocyte resting-stage, but persists as a compact and darkly staining body on the periphery of the nucleus : he erroneously stated that it divides longitudinally at both maturation divisions, but corrected this mistake in a later paper upon the Locustidai. This " accessory '' chromosome of McClung has been found by de Sinety in the Phasmidse, and by Sutton in Bracliystola : Baumgartner has studied it in Gryllxis ; and his results have been confirmed by Gutherz, working upon the same material. Otte has observed it in Locusta, Gevsivd in Stenohothrus biguttulus, '^owlin in Mela7ioplus bivittatus, and Robertson in Syrbula admirabilis : Davis has seen it in every member of the Acrididse and Locustidse that he has studied, and further, has phown that this " monosome " is represented in the oogonia by a pair of

X*

4 CAPT. C. F. U. MEEK ON THE

chromosomes. He found it in certain cases enclosed in a vesicle during, the resting-stage, but considers this condition artificial and unimportaiit.

Somewhat different results were obtained in 1905 by Montgomery working upon Syrhula acidicornis, for he declared that the heterotropic chromosome is represented in the spermatogonial cell by two chromosomes, and that it divides at both maturation divisions. Robertson's researches however upon the closely allied S. admirabilis afford no evidence of this paired condition, and support the view that this chromosome passes entire to one pole at the first maturation division, splitting longitudinally at the second : this seems to be the normal occurrence in the Orthoptera, for it has been observed by Baumgartner, Davis, Gerard, Gutherz, McClung, Nowlin, Otte, Robertson, de Sinety, Sutton, Wilson, and others.

The discovery in the male germ-cell of an odd chromosome, which passes entire to one pole at a subsequent mitosis, and the discovery that in allied- types the unequal members of one spermatogonial pair pass to opposite poles- have proved that dimorphism of spermatozoa exists in certain groups : and, since spermatozoa of the one kind produce males, and those of the other females, sex, in these organisms, must be determined at the moment when the spermatozoon enters the micropile, immediately prior to amphi- mixis. This has given rise to the hypothesis that dimorphism of spermatozoa occurs throughout the animal kingdom, and that sex is determined in this manner.

It is possible that the presence or absence of a particular chromosome is the factor controlling sex ; but it is equally possible that this chromosome contains only certain of the numerous characters peculiar to one sex, and that its passage to one pole is closely connected with the passage to that pole , of the ordinary chromosomes, after they have divided on the equatorial plate. The function of the chromosomes is not yet understood : although the majority of cytologists believe that the chromatin alone contains the bearers of the hereditary characters, some still affirm that the cytoplasm is the sole agent in this respect, and that the chromatin fulfils the subordinate role of a nutritive substance. The experiments of Boveri upon the fertilization of, enucleated Echinoderm ova appeared convincing, but unhappily the same experiments repeated by Delage and others gave diametrically opposite results. It seems of little importance whether the transmitted material is composed of actual character factors, or whether it represents a con- catenation of physical units, resulting in the phenomena implied in heredity ; but it is important to ascertain by what means these phenomena are. reproduced generation after generation.

The character factors may eventually be found to reside in both chromatin and cytoplasm, being distributed in the latter during the resting-stages for: purposes of nutrition, and being collected together in the chromatin filaments- only during the stages immediately preparatory to karyokinesis : this would

SPERMATOGENESIS OF STENOBOTHKUS VIRIDULUS. 0

explain the resolution of the chromosomes into spiremes or reticulum, and their later shortening and consequent closer association of granules the chromatin in this case serving merely as a conA^enient vehicle for the precise distribution of character factors, or their equivalents, between the two daughter cells.

Material and Methods.

My material was collected at Nannerch, in Flintshire, N. Wales, in the last week of August 1909. The grasshoppers were killed in chloroform within a few hours of capture, and were placed whole in the fixative after the wings and legs had been removed, and the integument of the back slit up to allow readier access to the fluid. I have obtained excellent results with Perenyi's chromo-nitric acid solution, the resting-stages and various phases of mitosis being very perfectly preserved : the majority of writers on insect spermatogenesis, however, appear to have used Flemmiug's strong chromo- aceto-osmic acid solution, Hermann's platino-aceto-osmic acid solution, or the fixatives of Bouin and Zenker.

The grasshoppers were transferred after two hours to a 50 % aqueous solution of alcohol, and an hour later were placed in a 70 % solution, in which they remained for twelve hours ; they were then stored in a solution of 80 % alcohol. This storage solution was changed twice during the first month, having become thick and discoloured with pigment.

When required for embedding, the testes were dissected out, and placed for twenty-four hours in a 90% solution of alcohol: after being passed through absolute alcohol and cleared in cedar-wood oil, they were embedded in paraflin, remaining for twenty minutes in the first bath and for fifteen in the second. I used paraffin with a melting-point of 52° C, since I found that paraffin with a higher melting-point had a tendency to overheat the cells. Sections were cut with an ordinary Cambridge rocking microtome to thick- nesses varying from 5 to 10 [m, and were invariably stained on the slide. The nuclear stains used were Heidenhain's iron hsematoxylin, iron brazilin, and safranin, the first-named being used alone or in conjunction with a plasma stain e. g., eosin, congo-red, or picro-carmine ; I also used the tricolor stain of Flemming, and the permanganate of potassium method of !FIenneguy.

In staining with the iron hsematoxylin, 1 used, as a mordant, an aqueous solution of iron alum, in which the slides remained for six hours ; they were then stained for twelve or fifteen. Davis left his slides in the mordant for only two hours, and in the stain for from four to six ; but 1 have found that the longer period gives better results as regards sharp definition, while the process of differentiation can be more perfectly controlled. In the cases where a second stain was used, the slides were left for ten minutes in the plasma stain before being transferred to the iron hiematoxylin : the iron

b CAPT. C. F. U. MEEK ON THE

alum has no effect upon the former, but this cannot be said the alcohol ; so great care must be taken not to wash out the whole of the plasma stain in the subsequent process of dehydration through successive strengths of alcohol. The iron hsematoxylin gives the best results in all cases where it is required to bring the chromosomes and nucleoli into evidence ; and this is particularly noticeable when camera-lucida drawings are needed. Davis obtained his best results with iron hsematoxylin in (conjunction with bordeaux- red, and has confined himself almost entirely to this combination.

When staining with safranin I used a 50 % solution in alcohol, leaving the slides in it for from twelve to twenty-four hours ; this gives an orange-grey tint to the protoplasm, the chromatin staining bright red. Henneguy's method is a modification of this, for the safranin used is made by Zwaardemaker's formula, being a mixture of equal volumes of alcoholic safranin and anilin water : the slides were placed for five minutes in a 50/0 aqueous solution of permanganate of potassium, which acts as a mordant, and then stained for six or twelve hours, after careful washing in running- water. The excess of colour was removed by a high strength of alcohol. Wilcox used this method when working upon Caloptenus femur-ruhrum, and obtained good results ; he however allowed the slides to remain in the stain only for a few minutes.

In the iron brazilin method, first described by Hickson *, no second stain is necessary, for the cytoplasm as well as the chromatin is affected : the slides were placed for two or three hours in a solution of iron alum in 70 7o alcohol, and were then stained for from sixteen to twenty-four hours. This stain is useful for studying late stages of unripe spermatozoa and their earlier spermatid transformations.

The tricolor stain of Flemming gives very delicate results, particularly in stages other than those of actual mitosis.' I stained in safranin for forty-eight hours, and washed the superfluous colour out with strong alcohol ; the slides were then taken down to water through successive strengths of alcohol, and were stained for several hours in an aqueous solution of gentian, after which they were washed in water and placed for ten minutes in a similar solution of orange Gr, which acts as a differentiating agent for the gentian. This combination gives a purple tint to the chromosomes and nucleoli, the spindle fibres, &c., appearing in various shades of grey and brown.

The Follicles of the Testis.

The testes are two ovoid paired organs lying dorsally to the alimentary canal in the middle of the abdomen, and so closely associated that they can

* Hickson, S. J., ''Staining with Brazilin," Quart. Journ. Micr. Sci. xliv. p. 469, 1901.

Sl^EEMAfOGENESlS OF STENOBOTHRUS VIJRIDULUS. 7

be dissected out as a single body : they consist a number tubular follicles, tapering at the ends, and opening posteriorly into a duct com- municating with the vas deferens.

By numbering the follicles in a section, and allotting the same numbers to corresponding follicles in successive sections of a complete series, it is possible to reconstruct the follicle in any particular case, and to recognize the true position of one section in the whole, in cases where the razor has cut transversely or at an angle to the plane of length.

Primary^ Sperm -

atoffonia .

''*^« Secondary ditto.

,2'''^' Growth period. Pr/mary Sperm- •v.^ arocytes.

^^''=''/^'&2"f(maturation' X, dtv/sions.

,^^ '^^Spermat/ds '^'^' Unripe Sperm - ' --^^ atozoa.

"1\zBunct7es of'r/pe '"'y Sperm arozoa .

^. De^enerar/ny "' Cet/s.

At the anterior end of each follicle is a single cluster of primary spermato- gonia with the apical cell, and several clusters of secondary spermatogonia, arranged without definite order. The resting- or growth-^S'tages of the primary spermatocytes occupy a considerable area, lying posteriorly to the spermatogonia ; and the heterotropic chromosome is here seen for the first time as a dark and compact body apposed to the nuclear membrane.

We next see the various phases of the primary and secondary spermatocyte mitoses, there being no resting-stage between these two divisions. Pro- ceeding still further towards the posterior end of the follicle, we meet with the transformation from spermatids to unripe spermatozoa ; the former are

8 CAPT. C. F. U. MEEK ON THE

ill scattered groups, and the latter in more closely associated Jbunches. Beyond these are dense masses of ripe spermatozoa, placed at considerable intervals in the lumen of the follicle : the extreme end is occupied by degenerating cells that will undergo no further development.

The posterior half of the follicle is occupied by unripe and ripe sperma- tozoa, and the greater part of the anterior half is closely packed with the primary spermatocyte growth-stages. The follicle is divided into tracts, in which these various stages are found, the partitions arising from the follicle wall : further subdivision is effected by septa, dividing the tracts into cysts. Cells in one cyst are not all at the same stage ; and the precocious cells of one section correspond with the laggards in the next. When the follicle has been cut at right angles to its length, the succession of stages can be followed with great accuracy until we come to the spermatids, when the identity of the follicle is lost, clusters of spermatozoa alone being distinguishable.

Spermatogonia.

The extreme anterior zone of the mature follicles is divisible into two parts, occupied respectively by the primary and secondary spermatogonia. The former are arranged in a single layer round a central cell the apical cell recognizable by its regularly ovoid nucleus, in which lies a group of large and deeply staining granules, the ordinary chromatin particles being distributed in irregular blotches. The nuclei of the primary spermatogonia are situate in the region of their cytoplasm furthest from the apical cell, and present a lobulate appearance, as can be seen in fig. 1, on Plate 1. The chromatin is disposed in minute particles upon the linin threads of an apparently complete reticulum ; and I have failed to find any massing of larger granules, as in the case of the apical cell. Each follicle contains one apical cell with its attendant primary spermatogonia.

At present little is known of the nature of this apical cell, which has been found and studied in many insect forms, but principally in the Lepidoptera ; its function is not yet understood, but it probably plays an important role by affording either nourishment or physical support to the cells destined to become spermatozoa. On the other hand, it has been suggested that it is a degenerate spermatogonial cell, or the mother cell of the primary spermato- gonia surrounding it, or that its function is connected with the formation of the zones into which the follicle portions are subdivided. Davis has found it in the members of the Acrididae and Locustidse that he has studied, and has shown that in Dissosteira Carolina, Arpliia tenebrosa, Cliortophaga viridifasciata, and Stenohothrus curtipenms it is completely surrounded by the single layer of primary spermatogonial cells, but only partly surrounded in Melanoplus femomtus and Hippiscus tuherculatus, being at one side in

SPEEMATOGENEBIS OF STENOBOTHRUS VIRIDULITS. 9

contact with the connective-tissue cells. Gerard further distinguished it in Stenohotlirus higuttulus' by its deeper cytoplasmic colouring ; but I have not found this in my material. The cluster of primary spermatogonia is surrounded by numerous connective-tissue cells, recognizable by their small size and deeply stained nuclei. The secondary spermatogonial groups are completely enclosed by cyst-walls, formed from connective-tissue cells, and lie posteriorly to the primary spermatogonia in irregularly disposed clusters, often so closely packed that the cells become distorted. Bach group has been formed by repeated division of a single cell, originally extruded from the primary spermatogonial figure, so that there is a continuous stream of cells passing towards the posterior end of the follicle. A secondary spermatogonial cyst is shown on Plate 1. fig. 2, from which it will be seen that these cells closely resemble the primary spermatogonia, but are easily distinguishable by the absence of the apical cell.

As in the case of the primary spermatogonia, the resting-stage nucleus shows a series of chromatin granules disposed along linin threads : I have been unable to discover whether we are dealing here with one continuous thread, much convoluted, or with a number of threads, irregularly placed ill such a manner that they combine to give this reticular appearance. Montgomery seems to have experienced the same doubt in the case of /Syrhula. Davis merely describes a network, in which chromatin granules are massed at the intersections of the linin threads.

There are two spermatogonial generations ; and this agrees with the results of Montgomery upon Syrhula acuticornis, Gerard upon Stenohothriis higuttulus, and Davis upon numerous members of the Acrididse and Locustidse. Sutton however has declared that there are eight in Bracliy- stola ; and Wilcox has been unable to determine the exact number in Caloptenus femur-mhrum. McClung suggests that the number varies with the species.

In the resting-stages the nucleus is not deeply stained. The prophase of ; division is characterized by the flowing together of granules on the linin ■■ threads ; and these chromatin particles become more and more closely associated until they form the ragged filaments, representing the forerunners of the compact bodies that later appear on the periphery of the karyokinetic spindle. As condensation proceeds, the chromatin exhibits greater affinity for the iron haematoxylin, so that distinct correlation exists between the intensity of staining and the degree of proximity of the associating particles. The formation of the spindle is preceded by the appearance of two small asters in the cytoplasm, close to the periphery of the nucleus. The chromatin filaments have by this time assumed the shapes and sizes characteristic of the qhromosomes ; and they now arrange themselves on the equatorial plate, preparatory to division, the metaphase complex showing seventeen chromosomes of varying shapes and sizes.

10

CAPT. C. F. U. MEEK ON THE

In everj complex that I have studied I have found the same number of chromosomes, and the same size and shape relationships. With the exception of the heterotropic chromosome, the members of the complex can be arranged in a graduated series of eight pairs, divisible into three groups, small, large, and medium : there are three small pairs, of which two are spherical and the third ovoid, three pairs of large rod-shaped chromosomes bent slightly at the middle, and two pairs of medium chromosomes, which usually appear as straight rods. The heterotropic chromosome is the fourth largest in the complex, and is a straight or very slightly bent rod, recognizable for the first time at this stage. By choosing metaphases where the chromosomes overlap only to a small extent, and by making camera-lucida drawings upon successive occasions and comparing results later, I have tried to minimize the possibility of error in counting the number of chromosomes present; this difficulty is not experienced in the metaphases of the spermatocytes, where only half the spermatogonial number is found, and where cells can be chosen in which no overlapping occurs. Plate 1. figs. 3 & 4 show polar views of the spermatogonial metaphase, the seventeen chromosomes being arranged on the equatorial plate.

Gerard has found seventeen chromosomes in the spermatogonial complex of Stenobothrus biguttulus, and Davis's results in the case of S. curtipennis agree with this. McClung in an early paper suggested that the number is dependent on the family, and is a constant, but this has not been found to be strictly true. I believe the number is constant for the genus, but not for a larger subdivision of the animal kingdom. Since the number has been found to vary in the Orthoptera, it is interesting to compare the results of writers upon this subject. Sutton has found twenty-three chromosomes in Brachystola magna, capable of being arranged in three small and eight large pairs, with an odd or heterotropic chromosome ranking among the latter. Davis has counted the same number in Arphia tenebrosa, Hippiscus tuberculatus, Chortophaga viridifasciata, and Melanoplus femoratus. In the Locustid, Steiroxys trilineata, he has found twenty-nine, and has shown that in all cases the ordinary chromosomes can be arranged in pairs forming a graduated series. McClung has observed thirty-three chromosomes in Xiphidium fasciatum ; and Nadine Nowlin has counted twenty-three in Melanoplus bivittatus. When working upon crickets, Baumgartner found twenty-nine in Gryllus assimilis and twenty-one in G. domesticus.

The chromosomes, after placing themselves on the spindle, divide longitudinally, and their halves pass to opposite poles ; the division of the heterotropic chromosome is longitudinal, but occurs often at a later stage, when the ordinary chromosomes have begun to move apart : an example of the secondary spermatogonial telophase in shown on Plate 1. fig. 5. On reaching the poles the chromosomes elongate and appear to lose their affinity for the iron hsematoxylin : as the nuclear membrane reforms, they

SPEfeMATOGENESIS OF STENOBOTHRUS VIRIDULUS.

11

become more and more ragged ; and this dissociation of chromatin continues until we see again the characteristic resting-stage with its chromatin granules disposed along linin threads, which combine either in reality or in appearance to produce a complete reticulum. The whole process is merely an inverse repetition of that preceding division. The heterotropic chromosome takes no part in this diffusion of chromatin, and remains throughout this stage as a darkly stained and homogeneous body apposed to the nuclear membrane, where its affinity for the stain and smooth outline render it extremely conspicuous.

Primary Spermatocytes.

After the last spermatogonial division, resulting in the formation of two daughter primary spermatocytes, the nucleus is much reduced in size. McClung has pointed out that at this stage reproduction is replaced by constructive metabolism, and that the chromosomes, after exhausting their metabolic resources, unite their common energies to build up a new cytoplasm. This suggestion probably furnishes the true explanation, but in any case possesses considerable pragmatic value, for some process of this nature undoubtedly occurs.

The cells undergoing this resting- or growth-stage occupy large areas in the follicle, and the gradual increase in size as we proceed more and more posteriorly is very noticeable. This growth-period is continued until the nucleus has attained its maximum size, when the cell enters the prophase of the next mitosis. Plate 1. figs. 6 & 7 show the difference between the primary spermatocyte immediately after the secondary spermatogonial division and immediately before the next mitosis. The nucleus shows a reticulum, composed of chromatin granules placed along linin threads, the individuality of the ordinary chromosomes being completely lost.

It will be remembered that at this stage Sutton found no loss of individuality of the chromosomes in Brachi/stola ; each chromosome under- went resolution into a spireme in a separate sac, in which it remained completely isolated, although the sacs fused at one end to form a common chamber. He consequently met with no reticulum, or appearance of a reticulum, and so put forward this phenomenon as a convincing proof of the individuality of the chromosomes. Robertson observed a similar condition in Syrhula, but did not always find the sacs, containing the ordinary chromosomes, clearly distinguishable. Both Sutton and Robertson describe a distinct vesicle, in which the heterotropic chromosome Hes, having no morphological connection with the vesicles of the other chromosomes. I have been unable to find the smallest trace of such vesicles, and am confirmed in this by the work of Gerard on Stenohotlirus higuttulus—a member of the same genus.

12 CAPT. C. F. U. MEEK ON THE

The prophase of division is characterized bj the closer association of chromatin granules on the linin threads the reticulum ; and this process continues until the latter is resolved into a number ol; ragged filaments, which shorten and thicken, and later assume a boomerang shape. By this time all trace of the component granules is lost ; and the ragged horseshoe bodies^ folding themselves into figures eight and rings, are gradually- transformed into the smooth and clearly defined chromosomes. The resolution of the reticulum into filaments is shown on Plate 1. fig. 8, and the subsequent shortening and thickening of the boomerangs in fig. 9 of the same Plate. The various shapes assumed by the chromatin filaments at a still later stage are shown on Plate 2. figs. 10-19^ the most prominent types being crosses, rings, and loops. The last-named may be doubled to form a complete figure of eight, or may form a single loop with free ends twisted or crossed over one another.

As soon as the centrosomes have taken up their position at the poles, the chromosomes appear on the equatorial plate, and the characteristic metaphase figure is once more represented. The heterotropic chromosome remains as a dark and smoothly outlined body close to the nuclear wall while the chromatin filaments are being transformed into chromosomes : it then takes its place among them on the mitotic spindle. The number of filaments evolved from the reticulum is eight, so that nine chromatin bodies compose the metaphase complex. In this manner the sixteen ordinary chromosomes of the spermatogonial cell have been halved, and this reduction must be effected before the breaking up of the spireme, for I