40 Sterile and Hybrid Pheasants 



1. The cause of the sterility of the hybrids. 



In dealing with some sterile male hybrid pigeons in Part 9 of "Studies 

 in the Experimental Analysis of Sex," Q. J. M. S. Vol. LViii. 1912, it 

 was shown that the point at which the formation of the spermatozoa 

 became abnormal was at the synapsis preceding the first maturation 

 division. It was proved that the chromosomes in this division failed to 

 form the normal synaptic pairs but were distributed unequally on the 

 spindle, and it was also found that in the majority of cases the secondary 

 spermatocytes failed to divide again but went straight on to form sper- 

 matozoa of double the normal size, while in some cases deformed 

 spermatozoa with chromatic beads were produced. 



Two sterile male pheasant hybrids produced by crossing Reeve's ^ 

 with versicolor </ and Reeve's $ with Formosan (/* have been inves- 

 tigated. The birds were killed in June, when the former was rather 

 more than three years old and the latter two, and dissection showed 

 that the reproductive organs were anatomically normal. The vesiculae 

 seminales of the Reeve's by versicolor male were full of spermatozoa, 

 which moved actively when placed on a slide, though the presence of a 

 very large proportion of deformed spermatozoa was at once apparent. 

 In the other male the vesiculae were empty except for a certain amount 

 of cellular debris which appeared to have resulted from the breaking- 

 down of deformed spermatozoa. Smear preparations of the spermatozoa 

 from the first male, stained with iron-haematoxylin and eosin, brought 

 out a condition of affairs very similar to that which was described for 

 the hybrid pigeons in Part 9, except that in this case there was a much 

 greater preponderance of deformed spermatozoa. On comparing the 

 smear with similar preparations made from some normal male Phasi- 

 anus torquatus, it was apparent that the same irregularity in size of 

 the hybrid's spermatozoa occurs as in the case of the hybrid pigeons. 

 Figs. 1 and 2 on Plate I depict the normal (Fig. 1) and the hybrid 

 spermatozoa (Fig. 2), and it will be seen that many of the latter are 

 about double the normal size, while others are smaller than the normal. 

 In addition to these abnormall}^ sized spermatozoa, a few of the deformed 

 spermatozoa are drawn, but as a matter of fact in this hybrid these 

 deformed spermatozoa are greatly in excess of the rest. 



The examination of sections of the testes of the hybrids brought 

 out that, just as in the hybrid pigeons, the spermatogonia are perfectly 

 normal in appearance, but all the subsequent stages show degenerative 

 changes in the nuclei of a more pronounced kind than was found in 



