942 THE AMERICAN NATURALIST. [Vou. XXXIII. 
as indicated by the line a—é in Fig. 1, the cut surfaces bend 
slowly inwards and towards each other, and in the course of 
twelve to twenty-four hours they have met and fused along 
their entire length. As a result, the semicircle of tentacles 
now forms a complete smaller circle. The 
cut edges of the velum also meet, leaving 
an opening in the center of the velum, as 
in the typical medusa. The general form 
of the new individual is like that of the 
typical form, except on one side the bell 
is at first less rounded. It can swim about, 
eat, and I have been able to keep them 
alive for several weeks. A glance will 
show, however, that a typical medusa like 
the one from which the piece was taken 
has not been formed, for only two radial 
canals are present that extend out from 
the stomach (Fig. 2). The latter does not 
lie at the top of the subumbrella space, 
but somewhat to one side (Fig. 3). From 
the stomach arises a new manubrium. 
If the old manubrium was cut in half when 
the medusa was divided, each half makes a 
complete manubrium ; but if, as is often the case, the cut passed 
to one side of the original manubrium, then one piece retained 
the old manubrium, and the other piece developed an entirely 
new one. 
Along the line where the cut edges fused 
together a scar is present that resembles 
somewhat a third radial canal, but the third 
canal did not develop, although in some 
cases a short diverticulum may extend from 
the stomach for a short distance along this 
line. If the tentacles be counted after the 
operation, and then again when the piece has healed, the num- 
ber will be found to be the same, and this holds true for several 
weeks. It is possible of course that a few new tentacles may 
develop, since they develop also in the normal individual as it 
Fic. 2. 
Fic. 3. 
