86 G. CARL HUBER 



The epiblastic cylinder is closed at its distal end, the trophoblastic 

 at its proximal, and the open ends of the two cylinders are in close apposi- 

 tion, but not indistinguishably fused, for the character of each por- 

 tion of the ectoderm, after treatment with carmine, is still quite dis- 

 tinctive; the protoplasm of the trophoblast being tinged much more 

 faintly than that of the epiblast. 



Selenka, on the other hand, who has recognized in his 'Ekto- 

 dermblase' with 'Markamnionhohle' a distinctive structure, 

 believes this to blend completely with the Triiger. Since his 

 account with reference to this point has influenced later workers, 

 I may be permitted to quote him in the original. Referring to 

 the 'Ektodermblase' with 'Markamnionhohle,' he states: 



Dieser Ektodermkeim, welcher von dem vorriickenden Tragerzap- 

 fen anfanglich sehr wohl abgegrenzt ist, indem beiderlei Gebilde sich 

 in Folge der convexen Kriimmung ihrer einander zugekehrten Flachen 

 sozusagen nur in einem Punkte beriihren, fliesst endlich mit dem 

 Trager vollstandig zusammen, und zwar bei der Waldmaus bevor, 

 bei der Ratte und Hausmaus aber nachdem die Markamnionhohle 

 enstanden war. 



That the proamniotic cavity of the egg-cylinder of the albino 

 rat has its anlage in two distinct cavities, the one developing in 

 the ectodermal node in the antimesometrial portion of the egg- 

 cylinder, which is the first to develop; the other in the meso- 

 metrial portion in the extraembryonic ectoderm, was recognized 

 by Selenka (fig. 30, plate 14, E, Markamnionhohle, E', falsche 

 Amnionhohle) , Duval (fig. 100,) Robinson, and Widakowich 

 (fig. 3). Corresponding stages of egg-cylinder development as 

 presented by me in figures 26 and 27, for the albino rat, are 

 shown by Sobotta ('02), for the mouse in his figures 12 to 14 and 

 text figures a to f. On comparison of my figures with Sobotta's, 

 it becomes evident that the egg-cylinder of the rat is much longer 

 and more slender than that of the mouse. According to the 

 account of Sobotta, the egg-cylinder of the mouse, soon after its 

 anlage, shows by reason of a distinct transverse furrow a division 

 into two parts, an antimesometrial portion of globular form, 

 surrounded by a visceral layer of entoderm, corresponding to 

 what I have designated as the ectodermal node; and a meso- 

 metrial portion which early, shows the anlage of a proamniotic 



