GENERAL HISTOLOGY. 



95 



the epithelium has a still wider basis in the fact that many 

 organisms, and particularly organisms of low structure, con- 

 sist exclusively of epithelia and therefore must necessarily 

 develop their sexual products in epithelium. In other 

 words, sexual and epithelial cells are the oldest elements of 



FIG. 31. Section through the ovary of a new-born child. (After Waldeyer ) ge, germinal 

 epithelium ; pe, primitive egg in the germinal epithelium ; /, egg-pouch ; g, group of 

 eggs constricted off from the pouchlike growth (/>;;/, single egg with follicle ; v, blood- 

 vessel. 



the animal body, and hence very early came into relation 

 with one another. 



Sexual epithelium, or, as it is often also called, germinal 

 epithelium, like the glandular epithelium has the tendency 

 to grow down into the subepithelial tissues in the form of 

 isolated or branching pouches (Figs. 31, /, 32), and thus 

 in many groups of animals the sexual organs bear the 

 character of branched glands ; for this reason therefore one 

 may speak as often of sexual glands as of sexual organs 

 (Fig. 32). The male and female cells, the specific ele- 

 ments of the germinal epithelia and of the sexual glands, 

 differ, as has already been mentioned, in the fact that the 

 eggs are generally the largest, the spermatozoa the small- 

 est, cells of the animal body. 



