AUDITORY APPARATUS OF THE MOSQUITO. 579 
would not present surface enough for this kind of receptor of vi- 
brations ; and secondly, all non-aquatic vertebrates have an inner 
ear formed so as to bring the aerial vibrations, which strike the 
tympanic membrane, to bear with the greatest effect on the audi- 
tory nerve filaments, and the minuteness of insects precludes this 
condition. Finally, the hard test, characteristic of the articulates, 
sets aside the idea that they receive the aerial vibrations through 
the covering of their bodies, like fishes, whose bodies are gener- 
ally not only larger and far more yielding, but are also immersed 
in water which transmits vibrations with 4} times the velocity 
of the same pulses in air and with a yet greater increase in 
intensity. For these reasons, I imagine that those articulates 
which are sensitive to sound, and also emit characteristic sounds, 
will prove to possess receptors of vibrations external to the gen- 
eral surface of their bodies, and that the proportions and situ- 
ation of these organs will comport with the physical conditions 
ary for them to receive and transmit vibrations to the inte- 
nor ganglia. 
Naturalists, in their surmises as to the positions and forms of 
the organ of hearing in insects, have rarely kept in view the 
important consideration of those physical relations which the 
organ must .bear to the aerial vibrations producing sound, and 
which we have already pointed out. The mere descriptive anato- 
mist of former years could be satisfied with his artistic faculty for 
the Perception of form, but the student of these days can only 
make progress by constantly studying the close relations which 
necessarily exist between the minute structure of the organs of 
ely, grea 
z want of appreciation of these relations, together with the fact 
: that many naturalists are more desirous to describe many new 
3 forms an to ascertain the function of one well known form, 
which may exist in all animals of a class, has tended to keep 
Dieciate this perhaps more than the naturalists themselves, who 
^re imbued with that enthusiasm which always comes with the 
ea Study of any one department of nature; for the perusal 
those long and laboriously precise descriptions of forms of 
organs, without the slightest attempt, or even suggestion, as to 
