138 Embryonic Development of Ovary and Testis of Mammals 



cords is more intimate in the male than in the female, owing to the 

 fact that the connection is not, and probably never was, of functional 

 importance in the latter. 



One is struck with the fact that there is a complete, or almost com- 

 })lete, separation of the medullary cords of the ovary from the peri- 

 toneum at almost the same time that the seminiferous tubules of the 

 testis break away from it. This separation takes place essentially in 

 the same manner in both sexes. Coert, 98, considers the medullary cords 

 to represent a system of ducts which served in phylogenetically earlier 

 periods, to carry the female sex products to the Wolffian duct. Wal- 

 deyer, 70, considers them to represent vestigial seminiferous tubules 

 arising from the mesonephros. Paladino, 87, and Harz, 83, confound 

 them in part with the long rows of interstitial cells of the adult animal. 

 One might assume that there was one stage in the jjhylogenetic history 

 of the sex glands in which both medullary cords and seminiferous tubules 

 furnished sex products that were conducted to the rete efferentia through 

 the rete tubules. If one hold this view, he must grant that the forma- 

 tion of the cords of Pfl tiger or second generation of ovarian cords repre- 

 sents a return to the primitive condition in which the female sex pro- 

 ducts are again discharged into the body-cavity from the surface of the 

 sex gland. This view would hardly seem to be a reasonable one, hence 

 I, at least, would prefer to consider the cords of Pfliiger to be mere 

 interrupted continuations of the medullary cords. Winiwarter, 00, holds 

 a view very similar to the last, his well-known diagram practically ex- 

 pressing my own conception of the process. There is no exact corres- 

 pondence in number between the cords of Pfliiger and medullary cords, 

 the former being much more numerous that the latter. 



The medullary cords never assume the characteristics of seminiferous 

 tubules. 



The assumption that the separation of the medullary cords from the 

 peritoneum is not and never was phylogenetically of functional im- 

 portance, leads to many interesting questions pertaining to the influence 

 of heredity in the transmission of sexual characters. Is it possible that 

 developmental processes of functional importance to the testis alone must 

 be transmitted to the female or vice versa, simply because the germ 

 cells which have united to produce the embryo transmit tendencies to 

 the formation of both male and female, both of which assert their 

 power, though one be ever so feeble? In this connection it is of great 

 interest to note that Laulaine, 86, has found that the peritoneum of the 

 7 to 8 day chick testis thickens after the separation as though it were 

 about to develop along the line of the ovary. This is merely temporary, 



