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taking place. The sex cells are therefore cells “ sui generis.” On a review 
of the literature, it is seen that while most observers are in agreement as to 
the origin of the sex cells from the genital ridge, the divergence of opinion 
lies in the origin of the cells of the stratum granulosum or follicle cells, 
the majority expressing the view that the ova and follicle cells have a 
common origin. Among these are Pfluger (19), Waldeyer (28), Balfour (1), 
Kolliker (12), Nagel (18), Btihler (5), Coert (7), von Velits (25), Whitridge 
Williams (30), v. Winiwarter (26), and Lane-Claypon (13), and their 
statements are based upon the proof of the persistence of small cells of the 
original epithelial type throughout all the stages of development of the 
cortical zone of the ovary, and the distribution of these smaller cells 
round the differentiated nuclei, both within the cell nests and separately. 
A minority of observers, including Foulis (9), Wendeler (31), Clark (6). 
Stevens (21), Griffiths and Williamson (11), take the view that the follicle 
cell is mesoblastic in its origin, on account of its spindle-shaped appearance, 
and also on the fact that many ova are seen to be lying in close contact 
with the stroma cells. It was not until the appearance of von Winiwarter’s 
(26) paper in 1900 that the whole subject of the development of the ovary 
was put upon a clearer basis for the understanding of the growth of the 
germinal epithelium and the nuclear changes which take place in the germ 
cells. The material chosen by v. Winiwarter for examination was the 
ovary of the rabbit just before and after birth, and he describes the ovary 
in its early stages as consisting of two layers — a primitive cortical layer, 
made up of rows of epithelial cells, and a medullary, containing vascular 
stroma. The superficial layer of cells he calls “l’assise epitheliale.” The 
growth of the stroma and epithelial cells is mutual, and nests or groups of 
cells are cut off by means of the stroma cells forming “ les noyaux germi- 
natifs.” These nests become smaller and eventually contain one germ cell 
or ovum, with its surrounding follicle cells. The first formation in the 
ovary is that of the medullary cords, then the germinal epithelium proper or 
cell nests, and lastly the epithelial invaginations from the surface, all of these 
structures being in continuity, and each corresponding to a definite period 
of development of the ovary. In a recent series of papers by v. Winiwarter 
and Sainmont (27), (which have come into my hands since finishing this 
work), there is a full account of the development of the ovary from the 
examination of kitten embryos and the young animal after birth, and the 
conclusions arrived at differ somewhat in detail as to the distribution of the 
chromatin elements in the sex cells, but agree as to the main development 
of the ovary as a whole. 
In Bryce’s (4) Embryology , published in 1908, an outline of the develop- 
