246 SENSES OF INSECTS. 



casting dust in our eyes : for though three of these 

 are nasal organs, bearing nostrils; the two others have 

 no relation to the question, the horn of the rhinoceros 

 and the crest of the cock being merely appendages, and 

 have no more analogy to the nose and nostrils, which 

 co-exist with them, than they have to the eyes or ears. 

 I have on a former occasion observed, that a gradual 

 change sometimes takes place in the functions of parti- 

 cular organs ; but still, generally speaking, this obser- 

 vation regards secondary functions the primary usually 

 remaining untouched. We may say, for instance, with 

 regard to the primary use of the legs of animals, that it 

 is locomotion ; while the secondary is either walking, 

 running, jumping, flying, or swimming, according to the 

 circumstances and nature of the animal. Thus the fore- 

 legs of the Mammalia, in birds become wings, and both 

 pair injish are changed tojfa. Observe, I do not say 

 always and invariably, but in most cases, that analogous 

 parts have analogous uses, at least as far as primary uses 

 are concerned. When, therefore, we cannot have demon- 

 strative evidence concerning the function of an organ 

 discoverable in any animal, we may often derive satis- 

 factory probable arguments from the analogies observa- 

 ble in their structure compared with that of other animals, 

 concerning the nature of whose organs we have no doubt. 

 In fact, the chief evidence we have with regard to the 

 office of the organs of sense in the animals immediately 

 below ourselves, is that of analogy; because we see 

 with our eyes, hear with our ears, &c., we conclude, 

 with reason, that they do the same. 



In inquiring therefore into what may be the most ge- 



