QUADRUPLETS IN NINE-BANDED ARMADILLO. iS/ 



single chorion with four amnia would receive a rational expla- 

 nation. 



We are, of course, aware that other possible interpretations 

 might be given, such as has been offered from time to time 

 to account for human identical twins. Our studies of the 

 ovarian tissues of Dasypns have excluded the most plausible of 

 these, viz., that the ovum may have more than one germinal 

 vesicle. Further investigation will have to settle the next most 

 plausible explanation offered, that the polar bodies may become 

 functional. None of the other suggestions found in the litera- 

 ture seems as credible as the view to which we incline, and in 

 support of our contention we have facts derived from an examina- 

 tion of two sets of ovaries from gravid females. In one set 

 there is but a single corpus luteum, and, while in the other there 

 are two corpora lutea, one has practically disappeared, and evi- 

 dently had been formed during a previous pregnancy. 



After all, the development of the fcetal membranes is a matter 

 of secondary interest, as compared with the more fundamental 

 problem of the identity of the embryos of a set, and its corollary 

 that of sex determination. The bearing of this work on the 

 latter problem is obvious, and we hope that a study of the early 

 developmental stages will lend a solution to this problem, and 

 also furnish a satisfactory explanation of the puzzling question 

 of "identical twins" ; and thus raise this explanation from the 



plane of conjecture to the dignity of observed fact. 



AUSTIN, TEXAS, 

 April 30, 1909. 



