254 MICHAEL F. GUYER. 



8. Thus the evidence indicates that the male fowl is homo- 

 zygous, the female heterozygous for this particular element. 



9. The secondary spermatocytes when ready for division 

 display, as A rule, four and five chromosomes respectively. The 

 eight chromosomes which passed to the one secondary spermato- 

 cyte have paired to form four, and eight of the nine which 

 passed to the other secondaiy spermatocyte have paired similarly, 

 leaving the curved one unpaired. 



10. The second division is regarded as not a reduction division 

 since in the anaphase the daughter chromosomes often tend each 

 to become bipartite or to resolve completely into two, thus 

 revealing their dual nature. 



11. Occasionally the pairing in the secondary spermatocytes 

 is incomplete so that any number between four and nine may 

 appear for division. 



12. The odd element after lagging for some time at the equator 

 of the spindle in the secondary spermatocyte, divides. 



13. The spermatids which receive four chromosomes fre- 

 quently pass on to one or more additional divisions. These are 

 regarded as abnormal. Other evidences of degeneration in 

 various spermatids indicate that a considerable number do not 

 develop into normal spermatozoa. It seems probable that only 

 one class of spermatids, that with the odd element, become 

 spermatozoa. 



14. The frequency distribution of head-lengths of spermatozoa 

 in four different sets of measurements by two different observers 

 shows no evidence of more than one class of spermatozoa. 



15. The cytological evidence as presented in this paper har- 

 monizes with the evidence derived from experimental breeding 

 which shows the female to be heterozygous and the male homo- 

 zygous for sex and sex-linked characters. 



LITERATURE CITED. 



Boring, Alice M., and Pearl, Raymond. 



'14 The Odd Chromosome in the Spermatogenesis of the Domestic Chicken. 



Jour. Exp. Zool., Vol. 16, Jan. 

 Guyer, M. F. 



'oo Spermatogenesis of Normal and of Hybrid Pigeons. Thesis, University 



of Chicago. 



'oga The Spermatogenesis of the Domestic Guinea (Numida meleagris dom.). 

 Anat. Anz., XXIV Band, No. 20 und 21. 



