626 J. T. PATTERSON 



Since it was known that the mammalian ovary occasionally 

 possesses such follicles, it was natural to suppose that this fact 

 might furnish a clew to the problem of polyembryony. In fact, 

 Rosner ('01) not only made this claim, but he also attempted to 

 prove his point by a study of the ovaries of the South American 

 variety of the very animal with which this paper deals, namely, 

 the nine-banded armadillo. Rosner studied a single pair of 

 ovaries from a pregnant female sent him by von Jhering. He 

 found fifty-two polyovular follicles, as follows: one with seven 

 ova, one with five, two with four, seven with three, and eleven 

 with two. Rosner believes that the condition of multiple em- 

 bryos in the armadillo was to be explained by assuming that 

 four young, adjacent follicles fused together, and that the four 

 ova thus brought within a single cavity were later ovulated and 

 fertilized, and held together in such a way as to produce event- 

 ually the quadruplex foetal structure characteristic of the arma- 

 dillo pregnancy. 



Aside from the fact that only two out of the fifty-two poly- 

 ovular follicles observed by Rosner possessed the requisite number 

 of ova to account for the four embryos of each armadillo litter, 

 it has since been abundantly proved (Cuenot '03, and Newman 

 and Patterson '10) that the pair of ovaries studied by Rosner was 

 quite exceptional. Further, sufficient literature has accumu- 

 lated to show that the phenomenon of polyovular follicles occurs 

 in several widely separated species of mammals, and consequently 

 can have nothing to do with polyembryonic development. 



Schron ('63) seems to have been one of the first to record the 

 occurrence of polyovular follicles. He observed them in the 

 ovaries of the cat. Since then they have been reported in various 

 Eutheria, as follows: in the human by Nagel ('88), Schott- 

 lander ('93), Stoeckel ('98), Rabl ('99), and Arnold ('12); in dogs 

 by Waldeyer (70), Wagener (79), Bouins ('00) and Smyth ('08); 

 in cats by Rabl ('99) ; in bats by Van Beneden ('80) ; in rabbits 

 by Wagener (79) and Honore ('00) ; in the armadillo by Rosner 

 ('01). In addition to these records on the Eutheria, O'Donoghue 

 ('12) has very recently added the Marsupial, Dasyurus viver- 

 rinus. 



