THE FACULTY OF HEARING. 



3/1 



produce sound excite also other sensations by affecting the organs 

 of feeling in the integument which happen to participate in the 

 communicated vibration. The perception of sound (or the 

 sensation induced by sonorous vibration) is for the most part of 

 two-fold quality, and it remains therefore to be determined 

 whether, and how far, the effects of sound observed in insects are 

 really due to a proper faculty of hearing, or arise from sensations 

 (buzzing, twanging, rustling noises, &c.) which are felt as much as 

 heard. We can scarcely doubt that a great part of the movements 

 of the insect must be referred to sensitiveness of tactile sensation 

 rather than of hearing where we consider that the hard integument 

 with all its closely packed cuticular hairs and spines are exposed 

 to every tremor of the surrounding air, and that reflex move- 

 ments of the most energetic kind are more often produced by a 

 light shake or rustle than by true sounds. On the other hand, 

 sounds and noises which do affect insects, are often too slight to 

 produce vibration of the integument, and a delicate organ of hearing- 

 seems in such cases an absolute necessity. 



But whatever variety of instrument be discovered, a complete 

 auditory function embracing all the variety of sound which we 

 perceive is not likely to be the experience of any other creature^ 

 and it is sufficient in claiming a hearing faculty for insects to 

 demonstrate the presence of an organ which is physically 

 conditioned to meet certain requirements. Even in taking note of 

 our own experience we are too much in the habit of considering 

 each sense as single and undivisible in its nature, and of thinking 

 each organ which subserves a special sense as indivisible in 

 structure and function. But while each sensory function 

 ministers only to a part of our sentient life, and is but a fraction 

 of our whole objective consciousness, it is in its own sphere of 

 action a self contained integral department comprising a group of 

 co-ordinate organs. The compound character of our senses is too 

 obvious in daily experience to require demonstration. For our 

 consciousness of all external things, is but the recognition of otir 



