ORGANS OF HEARING. 191 
discovered the organ of hearing in the cockroach, 
(Blata Orientalis,) in the form of an opening 
coyered by a membrane, white, interiorly concave, 
and situated at the base of the antennz ; under it 
there is a projection from the brain, (the first nerve- 
knot or ganglion,) which appears to perform the 
office of an auditory nerve. The membrane 
was not round, but semicircular, and immediately 
bordering on the ring in which the antenne are 
fixed. Under it I found a white horny substance, 
similar to that which covers the inner crustaceous 
envelope of the head. The projections of the brain 
appeared to give off nerves to the antenne on each 
side ; but I could not determine whether it spread 
out over the membrane, which I am inclined to 
consider the organ of hearing, as I could not other- 
wise conceive of its functions. 
The antennee of butterflies terminate in a clubbed 
tip, in which there are not muscles for producing 
motion, as in the body of these organs, but half a 
liquid substance filling the cavity. In the Alder- 
man Butterfly, (Ammiralis Atalanta,) I found this 
substance intermixed with membranous matter, 
resembling in some degree the substance found in 
the auditory sacs of the frog, the calcareous portions 
being less than in the latter. I think it exceed- 
ingly probable that the clubs of the antenne are 
the seat of the sense of hearing.” * 
* See Field Naturalist’s Magazine, ii. p. 24. 
