D. W. Cutler 165 



Figures 11 — 27. Spermatogenesis of hybrids. 



Fig. 11. Spermatogonial division of dark coloured hybrids. 

 Figs. 12, 13. Spermatogonial divisions of light coloured hybrids. 

 Figs. 14, 14 fl. Spermatogonial equatorial plates of dark coloured hybrids showing in 

 Fig. 14 probably 20 chromosomes, and in Fig. 14a 19 or 20. 



Fig. 15. Spermatogonial equatorial plates of light coloured hybrids, showing pro- 

 bably 19 chromosomes on the left, and 20 on the right hand tigure. 

 Fig. 16. Spireme stage of dark coloured hybrids. 



Figs. 17, 18, 19. Stages in synapsis of dark coloured hybrids, showing the concen- 

 tration of the threads to one side of the nucleus. 



Fig. 20. Three large chromatin masses iu the primary spermatocytes of light coloured 

 hybrids. 



Figs. 21, 22, 23. Irregular number of chromatin masses in the primary spermato- 

 cytes of light coloured hybrids. 



Figs. 24 — 27. Irregular number of chromatin masses in the primary spermatocytes 

 of dark coloured hybrids. 



REFERENCES. 



Cutler, D. W. and Doncaster, L. " On the Sterility of the Tortoiso-.shell Tnni 

 Cat." Journ. of Genetics, Vol. v. 1915. 



Federley, H. " Das Vevhalten der Chruinusnnien bei der SpermatogeneMe von 

 Pygaera." Zeitschr. f. indtikt. AhstJimm., Vol. ix. 1913. 



CuYER, M. F. " Spermatogeneses of Normal and Hybrid Pigeons." Thesis, Univer.sity 

 of Chicago, 1900. 



"Sex of Hybrid Bird.s." Biol. Bull., Vol. xvi. 1909. 



"Studies on the Chromosomes of the Common Fowl as seen in Testes and 



in Embryos." Biol. Ball., Vol. xxxi. 1916. 



Harrison, J. W. H. and Doncaster, L. " On Hybrids between Moths of the 

 Geometrid sub-family Bistoninao, etc." Journ. of Oeneties, Vol. iir. 1914. 



S.Mi'i'H, G. " Studies in the Experimental Analy.sis of Sex, Part 9. Spei'matogene.sis 

 and the Formation of Giant Spermatozoa in Hylirid Pigeons." Quart. Jtiurn. 

 Micr. Sci., Vol. LViii. 1912. 



Smith, G. and Thomas, R. Haig. "Sterile and Hybrid Pheasants." Journ. of 

 Genetics, Vol. Iii. 1913-14. 



Thomas, R. Haig. "Experimental Pheasant-breeding." Proc. Zool. Soc.,Y()\, m, 



1912. 

 Wodsedalek, J. E. "Causes of Sterility in the Mule." Biol. Bull., Vol. xxx. 191G. 



