64 BULLETIN OF THE 



fine punctation. It as the appearance, therefore, as though these cells 

 secreted the porous layers ; however, concerning this, as well as concern- 

 ing the corresponding parts of the eggs of other animals, only careful 

 studies made on eggs of all ages can give an answer, wherefore I abstain 

 for the present from any opinion." 



According to Kowalevsky, Owsjanmikow und Wagner ('70 a , p. 172), 

 the outer membrane in Acipenser is thick, shagreen-like, and possesses 

 numerous very fine canals. When the ripe eggs fall from the oviduct, 

 this membrane sticks to objects ; with a certain amount of skill it may 

 be rather easily detached from the egg. The inner membrane is much 

 finer [has finer canals'!], transparent, and very firm. 



Salensky ('81, pp. 234-236) applies the name chorion to the outer of 

 the two layers composing the "thick capsule" which envelopes the ripe 

 egg of Acipenser; the inner he calls vitelline membrane. At first the 

 two are so intimately joined to each other that it is difficult to separate 

 them ; but after the egg has been deposited for some time, the chorion 

 is easily detached from the vitelline membrane, and may be removed 

 from the whole egg. From the study of sections of stained eggs the 

 author determined that the stickiness and the roughness of the surface 

 were due, not to the chorion, but to two special cell layers which in- 

 vest it. 



" As to the origin of these two membranes, there is no doubt that they 

 are derived from the two layers of cells which constitute the epithelial 

 wall of the ovarian follicle." 



"The chorion," he adds, "is probably a product of the secretion of 

 the membrana granulosa of the follicle ; when the latter ruptures, the 

 epithelial cells remain adherent to the chorion and are expelled with 

 the egg, and are again met with slightly modified at the surface of the 

 deposited egg." 



" The examination of microscopic sections of the egg shows that this 

 envelope, which, as has been said, is divided into two after deposit, — 

 into chorion and vitelline membrane, — presents three distinct layers. 

 The external and the internal have about the same thickness; the mid- 

 dle one is thinner. In separating the chorion from the vitelline mem- 

 brane one may convince himself of the fact that the chorion is composed 

 of two layers, the vitelline membrane of only one." 



From Mayzel's abstract (Salensky, 79, p. 220) I learn further, that 

 the outer layer is stained deeply by hematoxylin, the two remaining 

 layers not at all, and also that all three layers are radially and finely 

 striate. In the figure of the membranes given by Salensky ('78 b , 



