THE ORGANS OF THE MIDDLE GERM-LAYEK. 



3T7 



surrounding connective tissue, carrying with it the blood-vessels, 

 grows into the egg-tubes of PFLUGER (e.sch) and the nests (ei.b), and 

 divides them all into spheroidal bodies, the individual follicles (/). 

 Each such structure contains a single ovum, that is enveloped on 

 all sides by a layer of follicular cells. The vascular connective tissue 

 that grows around it becomes the follicular membrane or theca 

 folliculi. 



The resolution into follicles continually advances from the me- 



Fig. 216. Part of a sagittal section of an ovary of a Child just born, after WALDEYEB. Highly 



k.e, Germinal epithelium ; e.sch, PFLUGER 's egg-tubes ; ue, primitive ova lying in the germinal 



epithelium ; e.sch', long PFLUGEK'S tubes, in process of being converted into follicles ; 



ei.b, egg-balls [nests], likewise in process of being resolved into follicles ; /, youngest follicle 



already isolated ; gg, blood-vessels. 

 In the tubes and egg-nests the primordial eggs are distinguishable from the smaller epithelial 



cells, the future follicular epithelium. 



dullary substance toward the germinal epithelium ; however, there 

 are preserved under it for a long time Pfliigerian tubes, which 

 remain in connection with it by means of narrow epithelial cords 

 (e.sch) and contain eggs in process of development. 



The formation of new Pfliigerian tubes and young ova is a 

 process which continues in the lower Vertebrates throughout life, 

 but in the higher appears to be limited to the period of embryonic 

 development, or to the first years of life. In the first case, there 

 being an unlimited capacity for the formation of new structures, 



