AUDITORY APPARATUS OF THE MOSQUITO, 583 
the impacts sent to it through the intervening air. Thus, if the 
fibrill on the antennx of an insect should be tuned to the differ- 
ent notes of the sound emitted by the same insect, then when these 
sounds fell upon the antennal fibrils, the latter would enter into 
vibration with those notes of the sound to which they were sever- 
ally tuned ; and so it is evident that not only could a properly 
constructed antenna serve as a receptor of sound, but it would also 
have a function not possible in a membrane ; that is, it would have 
the power of analyzing a composite sound by the co-vibration of 
its various fibrilla to the elementary tones of the sound. 
The fact that the existence of such an antenna is not only sup- 
posable but even highly probable, taken in connection with an 
observation I have often made in looking over entomological col- 
lections ; viz: that fibrille on the antennz of noctural insects are 
highly developed, while on the antenne of diurnal insects they are 
either entirely absent or reduced to mere rudimentary filaments, 
caused me to entertain the hope that I should be able to confirm 
my surmises by actual experiments on the effects of sonorous vi- 
brations on the antennal fibrilla ; also, the well known experiments 
of Hensen,* and the inferences of Dr. Johnston from anatomical 
Studies of the antenne of the Culex, encouraged me to seek in 
aerial insects for phenomena similar to those Hensen had found in 
the decapod, the Mysis, and thus to discover in nature an appa- 
ratus whose functions are the counterpart of those of the apparatus 
with which I gave the experimental confirmation of Fourier’s the- 
Orem, and similar to the supposed functions of the rods of the 
organ of Corti. 
The beantiful structure of the plumose antenne of the male 
Culex is well known to all microscopists ; and these organs at once 
to me as suitable objects on which to begin my experi- 
ments. The antennæ of these insects are twelve-jointed and from 
each joint radiates a whorl of fibrils, and the latter gradually de- 
Crease in their lengths as we proceed from those of the second joint 
from the base of the antenna to those of the second joint from the 
tip. These fibrils are highly elastic and so slender that their 
ngtas are over three hundred times their diameters. They taper 
Slightly, so that their diameter at the base is to the diameter near 
3 to 2. 
a * Studios an +, ed k: s V ds. “Journal of Scientific Zöology” 
Siebold and Kölliker, Vol. xiii. 
