150 BULLETIN OF THE 



with which Hoffmann ('81) does not agree. It certainly does not make 

 its appearance till after the zona is well developed ; if it were derived 

 from the yolk, its substance would first have to traverse the zona radiata. 

 How the nourishment for the egg could pass into the latter through the 

 pore-canals, and the formative substance of the villous layer at the same 

 time pass out through them, is scarcely conceivable. Moreover, at the 

 distal end of each of the villi lies the nucleus of a granulosa cell, there 

 being as many villi as there are cells, a fact which proves beyond a 

 doubt the intimate relation of the two structures. 



The membrane just external to the zona in Clupea vernalis may be 

 considered homologous to that in Gasterosteus, Fundulus, and many 

 Cyprinoids, even though it does not in Clupea bear appendages as it 

 does in Gasterosteus. From the development of the appendages in 

 Fundulus and Gasterosteus it is evident that this membrane has no 

 connection with the granulosa cells. In these cases each of the appen- 

 dages does not correspond to a single cell as in the perch, nor to any 

 definite number of cells. If Reichert is correct in saying that the 

 homogeneous membrane found in young eggs is a different structure 

 from the zona radiata, the membrane under consideration may perhaps 

 be looked upon as the primitive membrane described by him. It is 

 certain that it appears before the zona, and I am inclined to think that 

 it is derived from the yolk. 



Cambridge, December, 1888. 



