347 
Larva of Chaoborus Crystallinus (de Geer). 
was released and placed in a small hand tank. It appeared to be 
lifeless, and immediately floated to the surface. We examined it 
and found it had a huge blister between the thorax and head, the 
body was swollen, the anal segment twisted, and the head drawn 
down. Hundreds of stinging cells had been discharged into the 
head, and parts of the body, which appeared as if powdered with 
small glass beads. The body contents were semi-opaque, except- 
ing the dorsal side of two segments, which were normal : here no 
stinging cells had been deposited. 
At 7.30 the same day, with the exception of small portions of 
the digestive track and a few muscle ends, the organs had broken 
down and appeared like a semi-opaque mass ; a small rupture of the 
integument had taken place, through which oozed the body con- 
tents. Was this rapid decomposition normal or due to the injected 
poison ? The latter, we are of the opinion, was the cause. This 
helps us to understand how the Hydra digests apparently impossible 
meals. On another occasion we witnessed the complete absorption 
by a Hydra fusca of a fully grown larva measuring 12 to 13 mm. 
The coat of the Hydra had been so stretched to effectively cover the 
larva that the outline of the shape of the latter was clearly defined. 
Within a few hours of its meal the Hydra was found suspended 
from some pond- weed, tentacles retracted, its body globular in 
form, indicating that its prey had been readily digested and con- 
verted into a liquid mass. 
The dorsal vessel, or heart, runs almost the entire length of 
the larva, commencing at the eighth segment, whence it can be 
readily traced through to the head, but it is impossible to precisely 
locate its termination, as the muscles and other structures com- 
pletely obscure it (fig. 8). 
We have examined specimens not more than two or three days* 
old — the head then being partly filled with a granulated mass, the 
muscles not yet being formed — and have still been unable to definitely 
make out the end, although a slight pulsation just under the place 
occupied by the compound eye indicated the position, and suggested 
the nutrient fluid was emitted at that point. 
