OVARIAN FOLLICLES IN FERRETS AND FERRET-POLECAT HYBRIDS. 315 
wall of the follicle becomes thinner and thinner as the distension of the follicle 
proceeds, and ultimately it ruptures at the most projecting point. 
The time which intervenes between insemination and rupture of the follicles 
varies considerably ; the- shortest time in my series of animals was 30|- hours, and in 
one, an animal killed 93^ hours after insemination, rupture had not yet occurred 
(9 and 10, Table IX). 
When rupture takes place the ovum with its corona, the secondary liquor folliculi 
with the remnants of the dispersed cumulus epithelium, and the primary liquor 
folliculi with the greater part of the membrana interna, are evacuated, and they are 
carried, apparently at once, into the cranial part of the middle third of the oviduct. 
I have found four' extruded ova in the space between the ovarian capsule and the 
ovary, and one escaping through the opening from the interior of the capsule 
into the peritoneum (fig. 2, PI. I ; fig. 46, PI. VIII), but all the others, which were 
still unfertilised, or which were in the earliest stages after fertilisation, were in the 
cranial part of the middle third of the oviduct, where fertilisation usually occurs. 
None of the ova which were in the cavity of the ovarian capsule were fertilised, and 
I have never found spermatozoa beyond the cranial part of the middle third of 
the oviduct. 
Not uncommonly, as in the case of the ovum shown escaping into the peritoneal 
cavity (fig. 2, PI. I ; figs. 46, 47, PI. VIII), the extruded ovum and its corona 
become enveloped by portions of the liquor folliculi, which, judging from its reactions 
to stains, and from the fact that parts of the membrana interna are associated with 
it, is the primary liquor ; but quite as frequently the ovum and its corona are 
accompanied and surrounded by numerous cells, which are, apparently, those which 
were adjacent to it in the cumulus. In other cases the ovum and its corona lie quite 
free in the fluid in the oviduct. The differences appear to be due to the amount and 
the character of the dispersion of the cumulus cells which takes place after insemina- 
tion. In all cases some of the cumulus cells remain attached for a time to the corona 
cells by fine protoplasmic filaments. In many cases the membrana limitans interna 
is entirely displaced from the cumulus cells, but in others parts of the membrana 
interna remain attached to the cumulus cells, which are themselves connected with 
the corona cells. 
When rupture occurs and the cavity of the follicle is evacuated the walls of the 
follicle contract and fold (fig. 26, PI. IV ; figs. 27, 28, 30, PI. V), but, as a rule, a 
considerable part of the cavity of the follicle remains, and only occasionally is it 
almost entirely obliterated, as in the follicle shown in fig. 29, PI. V. The differences 
appear to be associated with the extent to which the membrana limitans interna 
is detached from the follicular epithelium by the secondary liquor folliculi. If the 
separation is complete, as in the specimen shown in fig. 24, PI. IV, all the contents 
are evacuated and the cavity almost entirely disappears ; but if part of the 
membrana interna retains its connection with the follicular epithelium until the time 
