298 J. E. WODSEDALEK. 



heads measured. It shows a distinct bimodal curve with modes 

 at 12.50 mm., and 14.75 mm. The intermodal depression is 



. 50 IV. 75 



FIG. i. Diagram showing the variation in size among six hundred mature 

 spermatozoa of the bull. 



deep and wide and the two elements of the curve are approxi- 

 mately equal as regards number of individuals. The spermato- 

 zoa of the larger type undoubtedly possess the sex-chromosome, 

 while those of the smaller type are without it. Figures 39 and 

 40 show the comparative size of the two distinct types of mature 

 spermatozoa. They can be distinguished with ease under a 

 high-power microscope. 



The general scheme of the development of the spermatozoon 

 from the spermatid of the bull is similar to that in the pig and the 

 horse (Wodsedalek '13 and '14) and, therefore, will not be 

 described here. Bimodal curves were also shown by the writer 

 in connection with the spermatozoa of the pig and the horse, and 

 in a number of other species by Zeleny and Faust ('14 and '15) 

 and by Zeleny and Senay ('15). 



VI. OOGONIA. 



The best ovarian material studied in connection with the 

 number of chromosomes in the oogonia was obtained from some 

 of the small foetuses. The results obtained from this material 



