GENERAL IIISTOLOOY. 



Y9 



glaud-cells are usually scattered among ordinary epithelial cells, 

 so the sexual cells, almost without exception, lie embedded in 

 epithelium; it may be in the epithelium of the skin (fig. 32), of the 





Fig. 33.— (ierininal epithelium of a iiR-ilusa. e/i, ectoderm; eii, entoilenii ; o, cKg; 



c, epithelium. 



gut, of the body cavity, or of parts cut ofE from this (fig. 33). 

 This connexion of the sexual cells with the epithelium has a 

 deeper meaning in the fact that many organisms, and particularly 

 organisms of low structure, consist exclusively of epithelia and 



Fig. a3.— Section througll the ovary of a new-born child. (After Waldeyer.) i/f, 

 germinal epithelium; j-ie, primitive eg^ in the germinal e]jithelium; />, egg-pouch; 

 (/. egg-nest e(jTjstricted off from the pouchlike growth {p); /, single egg with fol- 

 licle; x\ blood-vessel. 



therefore must necessarily develop their se.xual products in 

 ej^ithelium. In other words, sexual and epithelial cells are the 

 oldest elements of the animal body, and hence very early came 

 into relation with one another. 



Sexual epithelium (or, as it is often called, germinal epithe- 

 lium) like glandular epithelium has a tendency to grow into tlie 

 subepithelial tissues in the form of isolated or branching tubes 



