586 AUDITORY APPARATUS OF THE MOSQUITO. 
it coincided with the ratio existing between the numbers of vibra- 
tions of the forks to which co-vibrated the fibrils of which these 
pine rods were models. 
The consideration of the relations which these slender, tapering, 
and pointed fibrils must have to the aerial pulses acting on them, 
led me to discoveries in the physiology of audition which I imagine 
are entirely new. If a sonorous wave falls upon one of these 
fibrils so that its wave-front is at right angles to the fibril, and 
hence the direction of the pulses in the wave are in the direction 
of the fibril’s length, the latter cannot be set in vibration; butif 
the vibrations in the wave are brought more and more to beat 
athwart the fibril it will vibrate with amplitudes increasing until it 
reaches its maximum swing of co-vibration, when the wave-front 
is parallel to its length and therefore the direction of the imp | 
on the wave are at right angles to the fibril. These curious su" 
mises I have confirmed by many experiments made in the following 
manner. A fork which causes a strong co-vibration in a certaim 
fibril is brought near the microscope, so that the axis of the Tes? 
nant box is perpendicular to the fibril and its opening is toward 
the microscope. The fibril, in these circumstances, enters on 
vigorous vibration on sounding the fork ; but, on moving the bes 
around the stáge of the microscope so that the axis of the = 
always points toward the fibril, the amplitudes of vibration of a 
fibril gradually diminish, and when the axis of the box come 
with the length of the fibril, and therefore the sonorous pulses telf 
on the fibril in the direction of its length, the fibril is absolute ¥ 
sition, 18 
brought quite close to the microscope. These observatio. 
revealed to me a new function of these organs; which 
moment, we assume that the antennæ are really the organ’ ile, 
receive aerial vibrations and transmit them to an auditory wa q 
of the perception of the direction sound more hig ; 
in any other class of animals. The following eSP% ise 
will show the force of this statement and at the same bare” n of d 
trate the manner in which these insects determine the oih : 
a sonorous centre. I placed under the microscope 4 ae eo to the 4 
and kept my attention fixed upon a fibril which co-vibrai® om 
sound of a tuning-fork, which an assistant placed in Y of the a 
positions around the microscope. I then rotated the stag®? l 
