OVARIAN FOLLICLES IN FERRETS AND FERRET-POLECAT HYBRIDS. 309 
where they form the vitellogenous crescent of Van der Stricht (40), in which a 
centrosome is not uncommonly visible (fig. 4, PI. I). I propose to deal with the 
structure of the ova in another communication, and therefore content myself with the 
remark that so far as the ova of the primitive follicles are concerned they correspond, 
generally, with the primitive ova of the cat, as described by Van der Stricht (39a). 
The cells of the capsule are flattened plates, and they are not distinguishable 
from the cells of the stroma amidst which they lie, except by their position, their 
arrangement, and by the fact that they stain less vigorously. 
As the follicles grow the follicle cells increase in number, and they gradually 
attain first a cubical and then a columnar form, whilst their nuclei become fairly 
spherical. At this period, when the follicle cells are seen in surface view, or in 
sections at right angles to their long axes, the cell bodies are polygonal, and neither 
in surface views nor in sections, which are either longitudinal or transverse, is there 
any definite indication of the presence of limiting membranes round the cell bodies ; 
indeed, in many cases the cell bodies appear to be fused to a greater or less extent 
into a nucleated synctium. 
It is difficult to say whether the increase of the number of the follicle cells, in the 
.early stages, is due to mitotic or to amitotic division, and, as a matter of fact, although 
I have examined many thousands of primitive follicles, I have never seen any clear 
indications of mitotic division of the young follicle cells, although mitotic divisions 
were numerous in larger follicles of the same ovary. Neither, on the other hand, 
have I been able to convince myself that the increase is due to amitosis, though such 
indications as are present are more in favour of amitosis than of mitosis. 
The primitive follicles, as already stated, lie occasionally in the tunica albuginea, 
but the majority are in the spindle strands which intervene between the columns and 
nests of interstitial cells, and neither the older nor the younger follicles are always 
the more superficially placed, for not uncommonly a follicle, in which the follicular 
cells have attained a columnar form, lies quite close to the tunica albuginea, 
whilst follicles which are still quite primitive are situated much more deeply. In 
some places and at certain times the primitive follicles are so numerous that they 
form definite nests, and this is most commonly the case in the neighbourhood of the 
hilum. In such nests two adjacent ova may be separated by only a single layer 
of follicle cells (fig. 4, PL I), but as a rule each ovum has its own capsule of 
flattened, cells. 
When the follicles have attained a size of ‘0009 mm. 3 the nuclei of the follicular 
epithelium begin to arrange themselves in two layers — an internal, adjacent to the 
oolemma of the ovum, and an external, next the external limiting membrane ; and 
whenever the cell territories, associated with each nucleus, can be distinguished, at 
this stage, they extend from the oolemma to the external limiting membrane. At 
this period the majority of the follicles are distinctly ovoid in form, and the multi- 
plication of the nuclei is most rapid at the poles of the follicles (figs. 9, 10, 11, 
