THE OVA AND OVARY IN MAN AND OTHER MAMMALIA. 193 



The germ epithelium consists of distinct copuscles ar- 

 ranged 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 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 somewhat 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 cor- 

 puscles, 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 cor- 

 puscles appears to be produced by the swelling out of the 

 nucleus. In the two weeks' old kitten the corpuscles of the 

 ovarian germ epithelium are several deep, and the layer 

 itself is of irregular thickness. 



As we examine the layer of germ epithelium as it passes 

 round the ovary, we are at once struck by the fact that the 

 corpuscles present a great variation in size and degree of 

 development. Here and there we see large spherical nuclei, 

 having round them a thin investing layer of protoplasm, 

 while in other situations certain individual corpuscles stand 

 forth prominently among their neighbours, and are conspicuous 

 by their size and the size of their nuclei. In these latter the 

 protoplasm surrounding the nuclei is in the form of a thick 

 layer. Between these largest corpuscles and the ordinary 

 small ones every variety of size and form is to be met with. 

 The largest corpuscles, which present so much protoplasm 

 round the nucleus, are evidently individuals which have 

 reached an advanced stage of development. These have 

 been termed primordial ova, and there can be no doubt that 

 a great number of the larger or spherical germ epithelial 

 corpuscles are developing into similar bodies. 



The ordinary size germ epithelial corpuscles measure about 

 -g-^Voth of an inch, while the primordial ova measure about 

 7-oVoth of an inch, but these measurements vary. 



On carefully examining the primordial ova, in many 

 instances two or more small fusiform corpuscles are seen in 

 close contact with their yelk or protoplasm. 



VOL. XVI. NEW SER. N 



