306 J. E. WODSEDALEK. 



2. Nineteen chromosomes appear in the primary spermatocyte 

 division, of which eighteen are bivalent and the other is the 

 unpaired sex-chromosome. 



3. In the primary spermatocyte division the heart-shaped 

 sex-chromosome passes undivided to one pole in advance of the 

 other chromosomes. 



4. The primary spermatocyte division is evidently the reduc- 

 tion division, giving rise to two different types of secondary 

 spermatocytes, one with the sex-chromosome and the other 

 lacking it. 



5. The one type of secondary spermatocyte, which contains 

 the sex-chromosome, gives rise to two spermatids, each containing 

 the sex-chromosome and eighteen ordinary chromosomes. 



6. The other type of secondary spermatocyte, which lacks the 

 sex-chromosome, gives rise to two spermatids, each containing 

 only the eighteen ordinary chromosomes. 



7. The mature spermatozoa are of two types, equal in numbers. 

 The one type is larger and contains the sex-chromosome. The 

 smaller type is without the sex-chromosome. The larger type 

 is female producing, while the smaller is male producing. 



8. Thirty-eight chromosomes occur in the oogonia; two of 

 these are the sex-chromosomes. 



9. The reduced number of chromosomes in the female is, in 

 all probability, eighteen ordinary chromosomes and one sex- 

 chromosome which apparently occurs in all of the mature ova. 



10. The somatic cells of the male contain thirty-six ordinary 

 chromosomes and one sex-chromosome. 



1 1 . The somatic cells of the female contain thirty-six ordinary 

 chromosomes and two sex-chromosomes. 



12. The number of chromosomes in the somatic cells of the 

 two sexes is in exact accord with expectations. 



13. There is no relation between the time in the heat period 

 at which the cow is served and the sex of the offspring. 



14. Sex in cattle, for the present, remains a matter beyond the 

 control of the breeder. It is determined by the sex-chromosomes ; 

 it is a matter of inheritance. 



15. Sex-limited inheritance strengthens the belief in the chro- 

 mosome theory of sex-determination. 



