88 G. CARL HUBER 



striction is in the region of the original furrow which demarks 

 the antimesometrial and the mesometrial portions of the egg- 

 cylinder, the region of the primary amniotic fold; the second 

 where the mesometrial cavity ends; and the third where the 

 original blastodermic cavity reaches its mesometrial end. The 

 three folds recognized by Melissinos, are characterized by the 

 specificity of the ectoderm. Since his statement concerning this 

 point is somewhat involved, I find it necessary to use his own 

 words; they read as follows, referring to these folds he states: 



Der eine derselben a liegt antimesometral und ist der bekannte 

 erste kugelformige Buckel (Ektoderm) mit den langlichen, cylinder- 

 pyramidalen oder polygonal-pyramidalen Zellen; der zweite b liegt 

 in der Mitte und besteht aus kubisch-polygonalen Zellen, und der 

 dritte Buckel c, aus polygonalen Zellen bestehend, liegt mesometral 

 und ist von dem mittleren durch Einschniirung, von der Basis des 

 Ectoplacentarconus aber durch die bekannte Urfurche des Eicylinders 

 getrennt, in der sich das viscerale Dotterblatt zum parietalen Dotter- 

 blatt umbiegt . 



So far as I am able to determine, the account of Melissinos 

 agrees with that given by Sobotta, as concerns the folds of the 

 egg-cylinder of the mouse. Selenka's account need not receive 

 special consideration. 



In well-fixed egg-cylinders of the albino rat no such folds are 

 recognized. At the line of junction of the primary embryonic 

 ectoderm and the extraembryonic ectoderm, a slight infolding 

 of the layers, variable in degree, is recognized. Other foldings 

 of the wall of the egg-cylinder I have regarded as accidental and 

 not of special significance. Therefore, I am wholly in accord 

 with Widakowich, who has also discussed this question with 

 reference to the albino rat and has described the low fold in the 

 region of the junction of the primary embryonic ectoderm and 

 extraembryonic ectoderm. Referring to that fold, he states: 

 "Dass war die einzige konstante, bald starker, bald schwacher 

 ausgepragte Einschniirung der Proamnionhohle." 



Sobotta deserves credit for having described fully the differ- 

 entiation and cytomorphosis of the cells of the visceral entoderm 

 of the egg-cylinder, and since his observations on this point apply 

 in the main to the albino rat, they may at this time be given 



