345 
Larva of Chaoborus Grystallinus (de Geer). 
From each of these patches descends a very robust nerve, which 
is in contact with one of the three thoracic ganglia. What can be 
their mission ? We suggest they are a further means of recording 
any outside commotion in the water which may arise from free 
swimming organisms or other causes. 
Having already an auditory organ in several segments regis- 
tering movements transmitted by a number of hairs, does it need 
this further apparatus for the same purpose ? 
Take the antennae of the male gnat. Why so many hairs ? 
We will refer to Mayer’s experiments with this creature, which 
has beautifully plumed antennae. He employed a series of tuning 
forks, and ascertained some of the hairs were' thrown into vigorous 
movement with a fork giving 512 vibrations to the second, whilst 
others remained nearly stationary. Other hairs vibrated to other 
notes extending through the middle and next higher octave of the 
piano. Moreover, those hairs are most affected which are at right 
angles to the direction from which the sound comes. We tried 
out the effect of a G tuning fork on ten larvae confined in a glass 
tank 4J in. by 5J in. and f in. wide. When left undisturbed for 
a period, the creatures arranged themselves in positions parallel 
with the long sides of the tank, with heads pointing towards the 
light. 
