No. 396.] HYDROMEDUSA, GONIONEMUS VERTENS. 941 
medusa reappeared, and to examine the behavior of pieces 
taken from different parts of the body. It was not clear to me 
exactly what took place, or how the change was brought about ; 
and the results show that the problem is not a very simple one. 
Gonionemus has generally four radial canals diverging from 
a well-defined central stomach. From the latter hangs down a 
Fic. 1. 
short manubrium. The individuals vary in size. I have gen- 
erally used those of medium and large size (10 mm. to 20 mm, 
in diameter). The number of tentacles also increases as the 
medusa grows larger. In a very small individual there were 
twenty-four tentacles; in one a little larger, thirty-two tenta- 
cles; in a larger one, forty tentacles; and in quite a large 
specimen there were about sixty-four tentacles. 
When a medusa is cut in two in a vertical inter-radial plane, 
