72 ROBERT SCHARFF. 



membrane of endothelium, while there is no trace as yet of a 

 granulosa. 



In a young egg (fig. 6), as I mentioned before, a few large 

 flat cells cover its whole surface. As the ovum increases in 

 size they become more numerous and much smaller, until in 

 the ripe eggs they have the appearance as seen in figures .6, 

 14, 15,/. 



I have already spoken of the peculiar modification of the 

 follicular layer in Blennius pholis, and need not refer to 

 it again. 



With regard to the origin of the egg-membranes, it was 

 stated that they appear after the follicle. The first membrane 

 is the zona radiata (figs. 8, 13, 14, 15, z). When it is fully 

 developed the inner " zonoid " layer is formed in those eggs in 

 which it is found. In Blennius pholis no zonoid layer 

 ever appears. In the gurnard an inner layer was seen in 

 sections of middle-sized eggs, but in later stages no such layer 

 could be discovered. I have had occasion to refer to this layer 

 in a previous paragraph. I myself have no doubt that the 

 egg-membranes originate from the yolk. Ovsiannikov 1 , 

 however, holds that the zona is derived from the follicle; and 

 Cunningham, 2 although he has not had an opportunity of in- 

 vestigating the subject more closely, comes to a similar con- 

 clusion. 



According to Eimer an outer layer chorion, of which I 

 saw nothing in the ova which I examined, originates from the 

 follicular cells. He, as well as most other authors who have 

 dealt with this subject, agree in the vitelline origin of the zona 

 radiata and the zonoid layer. In the ripe egg the zonoid layer 

 has disappeared completely. 



Before concluding this short note on the intra-ovarian egg 

 of osseous fishes, I must refer to a few points which have not 

 been dealt with. An opening appears in the zona radiata 

 before the extrusion of the ovum from the ovary. This " micro- 

 pyle," as it has been called by its discoverer " Doyere," may 



1 Ovsiannikov, loc. cit. 



2 Cunningham, loc. cit. 



