218 A. W. GREENWOOD 



Plate 16. 

 Phascolarctus cinereus. 



Fig. 16. — Daughter secondary spermatocytes (dimorphic) with remnants 

 of spindle- fibres between the two cells. One cell nucleus contains a deeply 

 stained body — the X-chromosome. (Bouin.) 



Fig. 17. — Prophase of second meiotic division. Irregular threads. 

 X-chromosome compact. (Flemming.) 



Fig. 18. — ^ Anaphase of second meiotic division showing division of the 

 X-chromosome. (Bouin.) 



Fig. 19. — Anaphase of the second meiotic division showing division of 

 the Y-chromosome. (Bouin.) 



Fig. 20. — (Sertoli cell nucleus with associated rods and deutoplasm. 

 (Flemming.) 



Fig. 21. — Sertoli cell nucleus with accompanying pale plates. The 

 chromatin of the nucleus is represented semi-diagrammatically. (Flem- 

 ming.) 



S a r c o p h i 1 u s u r s i n u s . 



Fig. 22. — Female. Metaphase plate of follicle cell. 12-f XX chromo- 

 somes. (Flemming.) 



Fig. 23. — Spermatogonia! plate. 12-fXY chromosomes. (Bourn.) 



Fig. 24. — Splitting of chromosomes diu'ing spermatogonia! mitosis. 

 All chromosomes except two (a and b) have divided. (Bouin.) 



Fig. 25. — Metaphase (side-view) of first meiotic division showing separa- 

 tion of the X- and the Y-chromosomes. (Bouin.) 



Dasyurus maculatus. 



Fig. 26. — Spermatogonia! plate. 12 + XY chromosomes. (Bouin.) 

 Fig. 27. — Spermatogonia! plate. 12-hXY chromosomes. (Bouin.) 

 Fig. 28. — Metaphase (side-view) of first meiotic division showing the 



separation of tlie X- and the Y-chromosomes. (Flemmmg.) 



Literature, 



^ Bardeleben, K. von. — " Die Zwischen-Zellen des Saugetier-Hoden ", 



' Anat. Anz.', Band 13. 

 V Benda, C. — " Die Spermiogenese der Marsupialier ". ' Zoologische For- 

 schungsreisen in Australien ', Semon, Band 3. 

 Bronte-Gatenby, J. — " Cytoplasmic Inclusions of Germ Cells ", ' Quart, 

 Journ, Micr. Sci.', vol. Ixii. 

 ^/ Jordan, H. E. — "Spermatogenesis of the Opossum", 'Arcliiv f. Zellfor- 

 schung ', Band 7, 

 Montgomery, T, H. — " Tlie Human Cells of Sertoli ", ' Biological Bulletm ', 



xxi, 1911. 

 Moore, J. E. S., and Walker, C. E.— " The Meiotic Process in Mammalia ", 



' First Report on the Cj-tological Investigation of Cancer ', 1906. 

 Painter, T. S. — " Studies in Mammalian Spermatogenesis ", ' Journal of 

 Experimental Zoology ', vol. 35, no. 1. 



