168 Proceedings of the Royal Society of Edinburgh. [Sess. 
“ Pfluger’s egg tubes.” These columns are surrounded by dense strands of 
stroma cells. These stroma cells reach almost to the capsular epithelium, 
and in places are isolating it from the underlying tissue. The strands radiate 
out from the centre of the ovary. In the deeper layers of the cell nests 
there are solitary oocytes surrounded by stroma cells and follicle cells. The 
capsular layer consists of a single row of cubical cells, with deeply-staining 
nuclei arranged at right angles to the underlying cells. Just under this 
layer is a narrow zone of the primitive oogonial type, but the stroma cells 
have invaded this layer in places and cut off the cells into groups. The 
remaining portion of the cortical zone is made up of cell nests and columns. 
The larger aggregations are nearer the periphery, the masses becoming 
smaller as the centre is approached. In the groups near the surface are seen 
cells in mitosis. Some of the cells are in a state of karyolysis. Cells of 
the first oocyte stage are seen near the surface, and cells in synapsis and 
with thick spireme, but the majority of cells have the longitudinal fission 
of their filaments. These cells are surrounded by follicle cells. Fig. 17 
shows cells from the surface of kitten’s ovary ; the stroma cells are isolating 
the capsular epithelium. In the medullary zone are masses of small cells, 
separated into groups by the stroma cells ; these are the future follicle and 
interstitial cells, and may be called “ reserve cells ” on account of their 
function. They appear to be more numerous at this stage than at any other. 
A few oocytes with double filaments surrounded by follicle cells are seen in 
the deeper cortical layers. 
Four weeks after birth . — There is not a marked difference in the 
structure. The cortical zone is broader, the cell nests filling the whole 
cortex, and the stroma cells forming a band under the capsular epithelium. 
Numerous cells in the first oocyte stage are seen and mitotic figures are also 
present. Cells in the synaptic stage are very numerous, more especially 
those with thick filaments. Thick spireme stage cells are also seen in 
numbers. When the cell is cut in transverse section the nucleus appears as 
if studded with dots of chromatin, thereby causing some confusion in the 
differentiation between these cells and those in the somatic anaphase of the 
oogonia. Nuclei with double filaments are seen in the deeper layers. 
Four months after birth (fig. 18). — Groups of cells are seen in a narrow 
peripheral layer ; there are numerous follicles in different stages of develop- 
ment, and the stroma cells are increased in number. The capsular layer 
is clearly differentiated from the underlying cells by a band of stroma cells. 
Epithelial invaginations are taking place from the surface. The cells are 
mainly in the double filament stage. There is no evidence of mitosis being 
present. Numerous masses of reserve cells are seen in the deeper portions 
