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- 



&508.75 9.00 9.25 9.509.7510.0010.2510.5010.7511.0011.2311.5011.7512.001125 



FIG. 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 



