No. 2.] THE MEDULLARY GROOVE. 2>77 



KastschenkOji in a iDreliminary paper mentions a " cleavage 

 cavity" in Torpedo eggs which at an early stage is imperfectly 

 covered and shows the food yolk through the very thin covering. 

 He could not find an external opening in his sections, but 

 inclines to the belief that such an opening exists. It is barely 

 possible that this '' cleavage cavity " of Kastschenko is the same 

 structure as the crescentic involution which I have noted above. 



Lake Forest University, 

 January, 1893. 



1 Aiiat. Anz., 1888, Bd. iii, S. 445. 



