L891.] Uterine Villiform Papilla of Pteroplatsea micrura. 361 



ehich are to be considered either as providing nourishment for the 

 jwing embryo after the nutritive yolk of the egg has been absorbed, 

 )r as maintaining and increasing the nutritive material of the yolk. 



Of Spinax niger he says (loc. cit., p. 236) : " The foetus in the 

 iterus is distinguished by possessing no trace of an egg-shell, and by 

 inner membrane of the uterus being beset by very long (six to 

 sight lines long) filiform villi." 



More particularly of the genus Torpedo he writes (loc. cit., p. 230) : 

 The eggs possess no trace of shell membrane ; they are only sur- 

 Dunded by an albuminous uterine fluid, as already Bedi, Stenonis, 

 jrenzini, and in more recent times J. Davy, observed. Cavoliiii 

 tates that the yolk sticks to the walls of the uterus, and that 

 lis is effected by an innumerable crowd of red uterine glands 

 ring on the yolk. By this are clearly meant the papilliform villi on 

 le uterus of Torpedo oculata ; but the yolk-sac in no way adheres to 

 le uterus, as the observations of J. Davy show, observations with 

 ?hich what I myself have seen in the gravid uterus sent by Dr. Peters 

 icords. The yolk-sac of the Torpedos is perfectly smooth. I can 

 the extraordinary difference observed by T. Davy in the 

 icture of the mucous membrane of the uterus, which in Torpedo 

 is furnished with villi, in Torpedo marmorata with parallel 

 >ngitudinal folds." Johannes Miiller also quotes Davy's observations 

 the increase in weight, from the undifferentiated egg-stage to the 

 jmpleted festal stage, in Torpedo, notwithstanding the disappear- 

 ice of the external yolk and the absence of any vascular maternal 

 jnnexion. 



Of the Spinacoid Shark Scymnus lichia he observes (loc. cit., 

 237) : " In the fresh uterus, the foetus and yolk-sac are sur- 

 Dunded by a white-of-egg-like fluid. Also in this Shai-k no trace of 

 egg-shell membrane is met with. The foetus with its enormous 

 3lk-sac is immediately surrounded by the uterus. The whole oval 

 ilk-sac is, in the younger and middle stages of development, 4 inches 

 and 2 inches thick. The inner membrane of the uterus is 

 rnished with cylindrical villi six lines in length." 

 John Davy (' Phil. Trans.,' 1834, pp. 531540), in the research 

 the embryology of Torpedo, referred to by Johannes Miiller, 

 escribes the mucosa of the gravid uterus of this Batoid, and 

 icially dwells upon the absence of any vascular connexion between 



embryo and the mother. 

 He states that, in several series of observations, while the average 

 reight of undifferentiated eggs was 182 grains, and the average 

 sight of eggs in which the embryo had appeared was 177 grains, the 

 rerage weight of " ripe foetuses " was 479 grains ; and he asks how, 

 the absence of any sort of structural connexion between the foetus 

 id the mother, this remarkable increase of weight is to be explained. 



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