318 
PROFESSOR ARTHUR ROBINSON ON 
protoplasm become collected into the form of granular filaments, and although the 
position of the filaments varies, they tend on the whole to lie parallel with the 
long axes of the cells (fig. 6, PI. I). The nuclei of the cubical or columnar cells 
are spherical or slightly oval, and whilst the cells form only a single layer, the 
nuclei lie close to the external limiting membrane. When the nuclei form two 
rows, those of the inner row lie close to the oolemma, and those of the outer row 
close to the external limiting membrane (fig. 7, PI. I; figs. 8, 10, 11, 12, PI. II). 
The chromatin of the nuclei, as in the previous stage, is still in the form of spheroids, 
and it is not possible, except occasionally, to distinguish nucleoli. The tendency 
for the chromatic substance of the nuclei to form spheroidal masses of varying size 
continues throughout the whole period of the growth, rupture, and closure of the 
follicles in the nuclei which are in the resting condition, and, at any given moment, 
they form the majority of the nuclei. After the nuclei have increased considerably 
in number and are arranged in several layers it is possible to find here and there, 
a nucleus which contains a definite nucleolus, but the appearance of a definite 
nucleolus in a follicle cell is uncommon, and in that respect the follicle nuclei 
differ markedly from the nuclei of the ova. The rarity of nucleoli in the nuclei 
of the follicle cells is as marked as the rarity of mitotic figures in any given section, 
and it is possible that the formation of a nucleolus is precedent to the commence- 
ment of mitotis, when the spheroidal masses of chromatin are transformed into 
short rods. 
As the follicles increase in size the chondriosomes in all the cells, including 
those which have become stellate or irregular in shape, assume the form of 
granular rods or filaments (fig. 6, PI. I; fig. 10. PI. II; figs. .54, 57, PI. IX; 
figs. 58, 59, 60, PI. X), which appear as granules when cut at right angles to their 
long axes, and this condition is maintained until the follicle cells begin to assume 
luteal characters, a condition which may occur before, but which more usually does 
not take place until after the rupture and closure of the follicle. As the luteal 
condition is assumed, nucleoli become more and more a feature of the nuclei of 
the follicle cells. 
During the whole period of the pre-inseminal growth of the follicle a layer of 
nuclei lies close to the externa] limiting membrane, and a similar layer lies close 
to the oolemma of the ovum (figs. 48, 49, PI. VIII ; fig. 40, PI. VII ; fig. 57, PI. IX; 
fig. 16, PI. Ill; fig. 53, PI. IX); but as the pre-inseminal maturity of the follicle 
is attained, the number of nuclei which lie close to the external limiting membrane 
is gradually reduced, for the majority of the nuclei migrate towards the interior 
of the cavity (fig. 58, 60, PI. X), though the external ends of the cells to which 
they belong still maintain their association with the external limiting membrane 
(figs. 58, 59, 60, PI. X), and as the pre-inseminal maturity of the follicle approaches, 
granules of osmic-blackening fat appear in the bodies of the cells (fig. 51, PI. VIII). 
The appearance of spherules of fat in the follicle cells during the pre-inseminal 
