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Proceedings of the Royal Society of Edinburgh. [Sess. 
the membrane, and these are the cells which have given rise to the state- 
ment that the follicle and stroma cell have a common origin. In some 
sections the nucleus is viewed from the side and has a fusiform appearance. 
Much stress has been laid by v. Winiwarter on karyolysis following the 
metaphase of mitosis. On observation of my specimens these nuclei do not 
call for comment, as they appear to me to represent a nucleus which has 
become degenerated during the process of mitosis. In the last paper on the 
kitten’s ovary, v. Winiwarter does not appear to give to them the same 
degree of importance as in his previous publication. 
It is seen on examination of the various stages of the pig embryo that 
the growth of the ovary corresponds with that of other mammalian types, 
but that it resembles the human foetus more closely in its advanced stage of 
development before birth, primitive follicles being well marked in an 
embryo of 14 cm., corresponding to a rabbit of the third or fourth week 
after birth. The capsular epithelium is differentiated at a very early stage, 
and although mitosis occurs among its cells, it does not seem probable that 
these cells take much part in the formation of future oocytes of a permanent 
type. Mitotic figures are also seen in the epithelial invaginations, but I have 
found no evidence of the formation of differentiated nuclei from these cells. 
In the early formation of the follicle only a few cells arrange themselves 
round the oocyte ; these increase in number, and the follicle takes on its 
typical appearance later. (Fig. 3.) 
In the ovary of the pig the stages of development of the poles seem to 
vary, that pole nearest the abdominal end of the oviduct appearing in some 
sections to be somewhat further advanced than the opposite pole. 
C. Ovary of Puppy — new-born. 
The transitional stages in the germ cells are better seen in this ovary 
than in any other I have examined, therefore the description will be given 
in greater detail. The puppy’s ovary is rounded in outline, being much 
thicker than that of the pig or human embryo, which is elongated ; it is 
enclosed in a tough sac of peritoneum. The differentiation between cortex 
and medulla is not marked, as the stroma cells are so dense in this and in 
older stages. In the hilum are seen remains of the Wolffian body and gland- 
like spaces — the rete tubules. Numerous blood-vessels are seen, with a well- 
defined endothelial lining. The cortical zone is composed of nests of cells 
arranged in rows and columns ; the convex borders of these columns are 
pressed into the medullary stroma. These nests are irregular in outline and 
branch in all directions, and are of various shapes and sizes. The smaller 
nests appear to be nearer the medullary zone. The capsular epithelium 
