DEVELOPMENT OF THE OVARIES AND OVA. 199 



that this stroma is only the support of a peculiar epithelial 

 formation, which is developed from the very first as an inde- 

 pendent embryonal structure, quite distinct from the stroma, 

 and which in fact holds the same relations to it as the products 

 of the two epithelial laminae of the embryo do generally to 

 their supporting and vascular connective tissue. 



Pathological evidence, and in particular the development of nume- 

 rous dermoid cysts in the ovaries, have long led observers to seek for 

 cells belonging to the corneal lamina (hornblatte) in the substance of 

 these organs. According to the well-known observations of His (52), 

 however, it has not hitherto been possible to obtain any certain proof 

 of this, from a consideration of the history of their development. 

 Nevertheless, I desire to call attention to a work of Bambeke (6) that 

 has very recently come under my notice, in which this observer states 

 he has found in Pelobates fuscus that the most external germinal 

 layer, from which the greatest part of the epidermoid structures are 

 developed, on both sides of Ecker's yolk plug (Dotterpfropf), at the 

 anal fissure of Rusconi and Remak, curls round in the interior of the 

 ovum, and there forms a portion of the third germinal layer, whilst 

 the remaining cells assume quite the characters of this incurved part. 

 From this third germinal lamina both the internal genital organs and 

 the Wolffian bodies are developed in the Batrachia ; this observation 

 may perhaps furnish a correct clue to the point in question. The 

 reader is referred also to the similar statements made in the pro- 

 visional communications of Gotte (47a). 



The early appearance of the ova is particularly worthy of 

 notice ; in all classes of animals they seem to be simply more 

 highly developed epithelial cells of the ovary, that have under- 

 gone some peculiar modification, so that the follicular epi- 

 thelium and the egg cells stand in a direct genetic relation to 

 each other. 



I take this opportunity of referring to the " polar cells " of El. 

 Mecznikow (74). He found that in the Cecidomyidse the earliest rudi- 

 ment of the ovary, which was composed of a mass of cells, presented 

 peculiarly formed cells, to which he applied the term "polar cells." 

 These constitute the youngest ova. 



If we may now regard it as certain that no new formation 



OF THE 



'UNIVERSITY 1 



