352 DR FOULIS ON THE DEVELOPMENT OF THE OVA, ETC. 
of the ovary delicate bundles of vascular tissue proceed upwards in all directions 
among the corpuscles, which thus become included in groups in the meshes of 
the stroma. All round the ovary, under the germ epithelium, groups of 
corpuscles from the germ epithelium are being imbedded in the stroma by the 
growth of vascular connective tissue round them. The largest corpuscles are 
situated most deeply in the stroma, and are in an advanced stage of develop- 
ment, while those more superficially imbedded are in a less advanced stage of 
development; the youngest corpuscles are immediately under, and in connection 
with the germ epithelium. The most deeply imbedded corpuscles have already 
assumed the character of primordial ova, and among the others we can trace 
many in course of development into similar bodies. In each primordial ovum 
the nucleus becomes the germinal vesicle, and the protoplasm which surrounds 
it gradually forms the yelk of the mature ovum. 
THE OVARY OF THE KITTEN. 
I shall now describe the structure of the ovary and the development of the 
ova in a kitten of two or three weeks; and I may here remark, that I know 
of no animal better suited than the kitten to show the relation of the germ 
epithelium to the stroma of the ovary. A section of a young kitten’s ovary 
presents a form similar to that of the young calf’s ovary. 
In a thin vertical transverse section of a two weeks’ old kitten’s ovary we 
may distinguish 
1st, The germ epithelium. 
2d, The zone of egg clusters. 
3d, The fibrovascular stroma. 
The germ epithelium consists of distinct corpuscles arranged in a layer which 
passes round the ovary from one lateral border to the other, and becomes 
continuous with the peritoneal epithelium which covers the stalk or peduncle. 
The corpuscles of the germ epithelium (fig. 6, 2, h) consist of clearly 
defined nuclei, all of which have a thin investing film of protoplasm. In some — 
instances this protoplasm’ is very clearly made out, and is in considerable 
quantity, but in other cases it can scarcely be seen, even under very high 
powers of the microscope. As in the ovary of the foetal calf, there is a constant 
proliferation of the germ corpuscles by a process of fission. They are some- 
what granular, and vary considerably in size; some are oval, but the greater 
number are spherical. In the ovary of a kitten of four weeks the corpuscles of — 
the germ epithelium appear columnar in form and compressed laterally. In the 
round or spherical corpuscles (/, 7), which are generally larger than the others, 
the nucleus is extremely well marked, and frequently possesses a bright 
nucleolus. The spherical form of the larger corpuscles appears to be produced 


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