THE OVA AND OVARY IN MAN AND OTHER MAMMALIA. 199 



(«.) Nature of the Germ Epithelium. — In a foetus of 

 seven and a half months the germ epithelium consists of 

 columnar-shaped corpuscles placed side by side and arranged 

 as an investment to the whole ovary. 



The germ epithelial layer rests on a thin irregular stratum 

 of connective tissue which is part of the general stroma of 

 the ovary, and is formed by delicate processes of the same, 

 which at an earlier stage of development grew upwards from 

 the deeper parts of the ovary to surround and inclose in 

 meshes those large groups of corpuscles found immediately 

 under the germ epithelium in its entire extent. This young 

 connective tissue stratum is the forerunner of the tunica 

 albuginea. 



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. 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. 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 exa- 

 mined, the corpuscles are of different sizes. Some of the 

 nuclei are swollen up into large spherical bodies, 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, the germ epithelial corpuscles are 

 columnar, but many of them are assuming an oval and 

 spherical form. In the spherical ones the nucleus is clearly 

 defined, and shows distinctly 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 seven 

 and a half months' foetal ovary is examined under high 

 powers of the microscope, in many situations among the 



