No. 396.] HYDROMEDUSA, GONIONEMUS VERTENS. 943 
grows larger. ` Occasionally one or two new tentacles are found 
-in the region where the parts have united, but as a rule I have 
not noticed any increase in the number. 
If a medusa be cut into four parts, each containing one of the 
radial canals, then each piece gives rise to a small medusa-like 
individual. The cut edges come together and fuse ; the tenta- 
cles form a circle, and a velum is also formed with an opening 
in the middle (Figs. 4 and 5). The new manubrium arises 
from one side of the bell (Fig. 4), and not from the top of the 
subumbrella space. Its point of origin is determined by the 
position in the new individual of the portion of the original 
stomach. During the process of fusion of the cut edges the 
proximal end of the radial canal is carried in some cases far 
over to one side of the new bell. 
In such a case the manubrium 
appears to arise just inside of 
the line of tentacles. In other 
cases the proximal end of the 
radial canal is not carried so 
far, and in such cases the manu- 
brium hangs down from higher 
up in the subumbrella space. While the form of the one- 
fourth medusa has in general the typical bell-shape, yet 
such individuals have only one radial canal and an eccentric 
manubrium. It may be thought that the process up to this 
time is only one of healing, and that later the missing parts 
would regenerate. In the hope of seeing if this were true, 
I kept alive some of these medusz for several weeks, and 
although they seemed to be in excellent condition, yet they did 
not show the least sign of regenerating the organs that make a 
complete medusa. 
These experiments suffice to show that while the healing 
power of the one-half and one-fourth fragments is very great, 
yet the regenerative power is not well developed, for neither do 
the old parts change over into new ones having the typical 
arrangement (except in so far as the medusa-form is produced), 
nor do the missing parts regenerate (except the regeneration 
of a new manubrium) where the edges have healed together. 
Fic. 4. FIG. 5. 
