346 
Transactions of the Society. 
The tuning fork was set in motion and placed against the 
narrow end of the tank, the sound travelling through the water 
approaching the larvae from the rear, and caused an immediate 
response, the larvae turning in a very leisurely and apparently 
interested manner, the tails now pointing towards the light. 
This experiment was repeated on other occasions with more or 
less satisfactory results, and we were convinced that sound arising 
from a tuning fork and striking the hairs at right angles affects 
these creatures. If, however, the vibrating prongs of the fork are 
placed against the glass tank, producing a rattling noise, very little 
if any notice is taken of it. 
It is obviously of considerable advantage to the larva that 
these organs of sense, which we prefer to call auditory organs, 
should, be distributed over various parts of the body, in contact 
with different types of hairs, which would not only enable it to 
discriminate between the various disturbances set up in the water, 
but also to locate the direction from which they are coming. 
These very delicate hairs covering the body, registering every 
movement of passing organisms — from the bob, bob, bob of the 
water flea to the delicate gliding motion and final jump of 
Diaptomus castor — would first indicate the best location, which 
would probably be followed by the customary flick, the attacker 
afterwards remaining motionless until the eye registered the exact 
position before striking. 
In some instances neither eyes nor hairs avail. At one o’clock 
on a certain day we placed a freshly caught larva in a small 
aquarium. On inspection at 2.30 it had apparently disappeared. 
After a little searching we discovered it reclining in the tentacles 
of a green Hydra. The body was still held by one tentacle. It 
