178 WILLIAil WALLACE. 



foetida^ an eartliwonn, the ''so-called yolk nucleus^' first 

 appears as a granular mass in the form of a crescent in 

 intimate contact with the nucleus of the egg. " Tliis sub- 

 stance greatly increases as the egg grows." According to 

 this observer the destiny of the yolk nucleus, which she 

 regards as consisting of archoplasm, is to form the " polar 

 rings " at maturation. This is certainly not the fate of the 

 yolk nucleus in teleostean fishes. 



Bambeke (1898) gives an elaborate and beautifully illus- 

 trated account of the history of the " corps vitellin " in 

 Pholcus phalangoides. Here, again, as in the earth- 

 worms and in Zoarces, the body in question first appears as 

 a crescentic mass fitting over one side of the germinal vesicle, 

 and, as the egg grows, the corps vitellin becomes circular 

 and moves away towards the periphery, where it breaks up 

 into sepai'ate fragments, and finally into " granules safra- 

 ninophiles." The latter are then metamorphosed into 

 " elements graisseux," while about the same time the first 

 (proteid) yolk-spheres make their appearance. 



The above-recorded observations on Zoarces agree very 

 closely with Bambeke's description. I think there can be 

 little doubt as to a relation of some sort of the yolk nucleus 

 substance with the formation of oil in the egg cell. Whether 

 the oil is in any way related to the production uf proteid yolk 

 spheres is uncertain. The fact that in ovarian eggs of the 

 plaice, dab, and some other fishes there are no oil drups 

 (Cunningham, 1897), seems proof that oil is not a necessaiy 

 stage in the series of chemical changes leading to the pro- 

 duction of yolk spheres in the egg. Again, as demonstrated 

 by Cunningham (1897) and Fulton (1898), oil globules make 

 their appearance in ovarian eggs of fishes long before the yolk 

 spheres. What I have seen in Zoarces and Sygnathus 

 confirms this. The yolk spheres do not make their appear- 

 ance until the approach of the spawning period, and they are 

 deposited, at first peripherally, as fine granules in the proto- 

 plasm intervening between the oil globules. 



That the roundish body in the cytoplasm — that which is 



