INSECT HEARING. 381 



1. Experiments demonstrate that an insect can receive im- 

 pressions of sonorous vibration, by which they appear to distinguish 

 the strength, pitch, and quality of certain sounds. But it does not 

 follow that these impressions are comparable with the sensations 

 which human beings feel and characterise as hearing. 



2. In order that the same stimuli shall produce the same effects, 

 the agency of the same, or at least a closely similar instrument 

 (brain and sensory apparatus) is needed. But since nothing 

 corresponding with the nerve apparatus of the mammalian ear is 

 found in the insect, we are forced to conclude that the impressions 

 of sound received by the insect differ in kind from those which we 

 experience, and probably of a kind of which we have not the same 

 means of judging, nor in fact the same sense. 



3. The antennae, which are believed by most entomologists to 

 be instruments of hearing, are more suited by their construction 

 for the reception of sound than any other part of the insect. But 

 they can only be considered conductors of sound, as the faculty of 

 hearing remains after they have been cut off, and sound is 

 still transmitted to the internal organ through the hard case of head 

 and body. 



4. It may be questioned whether the instrumentality of a 

 special organ is needed for communication of the sensation of 

 sound. Insects and articulata generally differ in so many respects 

 from other animals, that neither offers any standard by which to 

 judge the other. Bearing in mind that numerous nerve filaments 

 are distributed in the cuticular hairs and spines and especially the 

 antennae, which are hairs on a very large scale, it might well be 

 (and experiments on beheaded insects render it very probable) that 

 they have no extra organ of hearing, but that the cuticular 

 appendages when thrown into vibrations corresponding with the 

 different sounds, occasion a sympathetic excitement of the nerves 

 resembling, perhaps, the sense of touch produced by intermittent 

 pressure. 



5. Before looking for an organ of hearing in any animal, we 

 should first ascertain whether it can be of any use to its possessor, 



