TWO PAIRS OF FEMALE TWINS 



249 



TABLE 8— Continued 



* Eggs thus marked are the very first eggs in the life of the birds that produced them. 



^ These eggs were the first after a long rest that followed a long peroid of reproductive 

 overwork. It is also important to observe that they were fertilized by a generic hybrid 

 (Zenaidura-Zenaida) male, and that these genera belong to a different subfamily from the 

 female that produced these eggs. There is evidence that in this type of cross different 

 sperms exercise opposite influence on the sex development. 



It is of some interest to add that the male that developed from Q2 was killed when 

 quite healthy; two testes were found, but, contrarj^ to the rule for normal males, the 

 left testis was larger than the right, i.e., the size relations of the glands were those of a 

 female. (Riddle, Anat. Rec, vol. 14, 1918, pp. 283-334.) 



