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 710) 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 (712); 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 Honoré (’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. 
