88 BULLETIN OF THE 



11 covered by a vitelline membrane which is not porous or enveloped in 

 adhesive material. It is thin, very transparent, and laminated, as has 

 been stated by Sars, and at one point is perforated by a single minute 

 opening, the micropyle." Ryder was unable to discover the lamination 

 until after the action of osmic acid, and was uncertain whether it was 

 a natural condition or the result of the action of the acid. " The cod's 

 egg," he says, "is without the zona radiata found enclosing the egg 

 proper of the shad, whitefish, and sculpin, and, inasmuch as it is unques- 

 tionably true that a micropyle perforates the zona in a number of these 

 cases, it does not appear that sufficient grounds exist for the declaration 

 that a micropyle perforates the zona radiata alone, in the face of the fact 

 that the vitelline membrane only is perforated in this one instance." I 

 have no doubt that the membrane in question possesses pore-canals, and 

 that it is therefore a true zona radiata. I can confirm EigenmanfiUs 

 observations in this particular, and believe that Eyder himself would 

 have come to the same conclusion had he observed the membrane under 

 the same favorable conditions. 



In an extensive paper on the eggs of bony fishes Owsjannikow ('85) 

 describes the egg membranes of a number of the more common fresh- 

 water forms. The most important part of his paper deals with the cap- 

 sular membrane in Perca and the equivalent structure in other fishes; 

 but the consideration of that part will best be deferred until I come to 

 review the other papers which deal with that subject. I may here add, 

 however, that he does not recognize the existence of a villous layer 

 outside the zona, but regards the structure which immediately envelops 

 the zona in Osmerus and other fishes as the equivalent of the capsular 

 membrane of the perch. His description of a thin transparent mem- 

 brane (membrana vitellina) inside the zona radiata in Salmo trutta is 

 materially affected by the subsequent statement that it is not found in 

 other cases (Lota, e. g.), and by the admission that it may have been 

 an artificial product. 



The pore-canals of the zona are often more deeply stained than the 

 substance of the matrix, and by treatment with certain reagents minute 

 points can be seen in the canals when highly magnified. In Lota vul- 

 garis the zona is very thin, and the pore-canals in patches do not pene- 

 trate to its inner surface. It is generally stratified, the strata being 

 laid down successively and all being perforated. The zona might, in his 

 opinion, better be called perforata than radiata. Concerning its devel- 

 opment in Gasterosteus the author says that the first trace of it is 

 seen to be a very thin membrane without any pores. These appear when 



