TWO PAIRS OF FEMALE TWINS 239 



port of both of the above-mentioned views. A few cases of identi- 

 cal male twins from extremely small ova of the pigeon would com- 

 pletely establish the view as stated for twinning in pigeons. 

 Our present data undoubtedly establish the relations of yolk size 

 to sex and give much warrant for the prediction that if identical 

 male twins ever arise from the ova of doves and pigeons they will 

 arise from small ova. 



In conclusion, it may be emphasized that the correctness or 

 incorrectness of the tentative hypothesis concerning the causes 

 of twin-formation, as stated in the immediately preceding para- 

 graphs, is unimportant to the main purpose of the present paper. 

 The available data concerning the germs which gave rise to two 

 pairs of female twins demonstrate that each pair arose from a 

 single ovum and that each pair arose from an ovum of high 

 storage metabolism. 



TABLES 



