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Proceedings of the Royal Society of Edinburgh. [Sess. 
chromosomes at the equator. In other cells the chromosomes form a diaster, 
but the majority of cells show the aster, where the chromosomes are dis- 
tributed as a crown in the centre of the cytoplasm. No accurate count of 
these chromosomes can be made, as the individual rods are difficult to 
differentiate. Other cells show the chromosomes scattered in irregular 
masses or rods over the centre of the cell, and the nuclear membrane re- 
forming round them. Numerous cells showing the latter formation are 
seen in these sections. Mitosis is not much in evidence among the cells of 
the capsular epithelium. (Fig. 11.) The chromatin spreads out in the 
form of filaments, a nucleolus appears and the cell takes on the form of the 
mother cell. 
Some of these cells have their chromosomes broken up and degenerated. 
These are the cells in karyolysis, but they are not numerous, and are of little 
importance. Some of the cells, with the chromatin rods round their nuclear 
membrane, appear to have a resting stage before further changes take place. 
Mitotic figures are seen among the stroma cells, but there is no direct evidence 
of mitosis among the follicle cells at this stage. As the cell becomes 
surrounded by the stroma tissue, it develops so that the cells nearer the 
medulla are at an advanced stage. The masses of small cells at the peri- 
phery may develop as oocytes, or may become follicle or interstitial cells, 
or may act as nutrient cells to the growing oocyte. (Fig. 12.) 
In the ovary, ten days after birth, there is not much change from the 
new-born. The layer of cell nests is smaller, the stroma cells are filling up 
the whole ovary, forming with the interstitial cells a dense mass of tissue. 
In the deeper parts cells in the thick spireme stage are seen. The inter- 
stitial cells in the central portions look like cords in outline, but no evidence 
is found of the so-called medullary cords further than that of the presence 
of some atrophied cells in the hilum. 
Ovary of three-months-old Pujppy . — In this specimen the changes from 
the previous stage are well marked. The capsular epithelium is entirely 
separated from the underlying cells by a band of stroma cells — the tunica 
albuginea. Invaginations into the deeper tissue are seen. The cell nests 
have disappeared, and in their place is seen groups of follicles arranged 
round the periphery of the ovary and coming close to the surface in places. 
(Fig. 13.) There is no distinction between cortex and medulla except that the 
blood-vessels are more numerous towards the centre. The whole centre is 
filled with masses of interstitial cells, divided up by stroma cells and blood- 
vessels. The cells surrounding the oocyte in the follicles consist of a coronet 
of cells with large oval nuclei, whose axes are perpendicular to the oocyte 
cell membrane, and in contact with it. These nuclei have a well-defined 
