SEX IN ANIMALS 541 
are those which contain the accessory chromosome or chromosomes. 
The larger class, therefore, includes the female-producing spermatozoa, 
the smaller class the male-producing spermatozoa. If this difference in 
size should be correlated with a slight difference in activity, it is con- 
8,508.75 9.00 9,25 9,50 9.75 10,00 10.25 10.50 10.75 11,00 11.25 11,50 11.75 12.00 12.25 
Fic. 214.—Frequency polygon of head lengths of spermatozoa in the horse.’ 
(Data from Wodsedalek.) 
ceivable that chance would favor fertilization with the more active 
spermatozoa, and would produce a consequent disturbance in the 
sex-ratio. 
Moreover, the gametes of the heterozygous sex, since they are made 
Digitized by Microsoft® 
