358 DR FOULIS ON THE DEVELOPMENT OF THE OVA, ETC. 
On tearing to pieces in a little water a fragment of this ovary and examining 
the debris under high powers of the microscope, many small portions of the 
germ epithelium will be found. When the deep surface of the epithelial layer is 
examined, the corpuscles are seen to be placed close together, and present in the 
membrane a tessellated appearance (fig. 10). The chief part of each corpuscle 
is the nucleus. Around each nucleus is a small quantity of protoplasm which 
acts as a cement substance holding the nuclei together. When the germ 
epithelial membrane is looked down upon from above, immediately on bringing 
the corpuscles into view a clear space is seen round the nucleus of each corpuscle 
(figs. 11 and 12, h,h). This space is occupied by clear protoplasm. The 
corpuscles in this early stage of development appear as little nucleated pieces 
of protoplasm; the nucleus is always the conspicuous part of each corpuscle, 
but the protoplasm round it may vary in quantity. In each piece of epithelial 
membrane examined, the corpuscles are of different sizes. Some of the nuclei 
are swollen up into large spherical bodies (fig. 12, 7), and around them is an 
increased quantity of clear protoplasm. In the larger nuclei a nucleolus is 
generally seen. The largest corpuscles are undoubtedly primordial ova. 
Between these and the smallest germ epithelial corpuscles every variety in size 
is met with. 
When seen in profile (figs. 13, 14, 15, h,h, h), the germ epithelial corpuscles 
are columnar, but many of them are assuming an oval and spherical form (figs. 13, 
14, 15, 7,7,2)._ In the spherical ones the nucleus is clearly defined, and shows dis- 
tinctly its well-marked membranous wall. Within the nucleus is a nucleolus, and — 
around it is a thin film of protoplasm. In some instances this film is so fine as 
scarcely to be made out. When a section of a 74 months’ foetal ovary is examined 
under high powers of the microscope, in many situations among the ordinary 
germ epithelial corpuscles all round the ovary, we find individuals standing forth 
prominently and conspicuous by their size and the size of their nuclei (figs. 14, 
15, m,m) similar to those bodies we described as conspicuous among the cor- 
puscles of the germ epithelium in the kitten’s ovary. Such have been termed 
primordial ova. On comparing these with the smaller round corpuscles, and these 
latter with the ordinary germ epithelial corpuscles, it is easy to see that they are 
germ epithelial corpuscles in a far advanced stage of development. In the pro- 
egress of growth the nucleus of the ordinary germ epithelial corpuscle first swells 
out and enlarges, becoming oval, then spherical, and around it is gradually pro- 
duced that protoplasm which assumes such dimensions in the primordial ova. In 
contact with these primordial ova we often see small fusiform corpuscles (n, n), 
and as in the case of the kitten’s ovary, some of them appear to have grown up 
among the germ epithelial corpuscles from the stratum of young connective tissue 
(j,j) on which the germ epithelium rests. - 
It is a fact of great interest, that as the germ epithelial corpuscle becomes a 
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