68 ROBERT SOHARFF. 



the interior of the egg. Eimer 1 is quite positive in his statements 

 of having seen prolongations from the follicular cells project 

 into the pores of the zona. This, however, was only observed 

 in the eggs of the ringed snake. Brock 2 again makes mention 

 of similar processes in the ovum of the barbel and that of 

 Ser/anus hepatus. Finally, the theory of the egg being 

 nourished by means of prolongations from the follicular cells 

 finds a strong supporter in Lindgren. 3 He shows, moreover, 

 that in the egg of the rabbit even follicular cells occasionally 

 travel through the pores of the zona. Some were observed 

 inside it, and others half way out. I myself have not been 

 able to trace any processes from the follicular cells into the 

 ovum, but it seems to me quite probable that such prolonga- 

 tions do exist. At any rate I believe that the ovum receives 

 its raw material as it were through the radial pores from the 

 follicle. It is then assimilated and transformed by the nucleus 

 and the egg nourished in this manner. 



Before I proceed to a description of the follicular layer, I 

 must mention another membrane which has been described by 

 some authors, while its existence has been denied by others, 

 I am referring to an extremely delicate membrane covering 

 the yolk internally to the zona radiata. I have seen such a 

 membrane in some cases in the young gurnard's egg (fig. 13, 

 m. i.), that is to say, only in sections of hardened specimens, 

 and not in the adult egg. It has been first described by Ransom, 

 who calls it the inner yolk-sac," in distinction to the outer 

 yolk-sac (zona radiata). He also isolated it inGasterosteus. 

 Oellacher did the same in the trout, after treatment with 

 chloride of gold. Allen Thomson, as well as Kolliker, Eimer. 

 Lereboullet, and Aubert, describe an inner delicate membrane. 

 Although Ovsiannikov saw this layer in Perca fluviatilis, 

 he found no trace of it in Lota vulgaris, and comes to the 

 conclusion that it is an artificial product. 



1 Eimer, loc. cit. 



2 Brock, loc. cit. 



3 Lindgren, loc. cit. 



