Say 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 kugelf6érmige Buckel (EKktoderm) mit den langlichen, cylinder- 
pyramidalen oder polygonal-pyramidalen Zellen; der zweite 6b legt 
in der Mitte und besteht aus kubisch-polygonalen Zellen, und der 
dritte Buckel c, aus polygonalen Zellen bestehend, legt 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 stirker, bald schwiicher 
ausgeprigte 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 
