62 THE USE AND NATUllE 



As already pointed out, there are obvious reasons why 

 the principal specialized Tactile Organs that may present 

 themselves in lower animals, should be found in the 

 neighbourhood of the mouth ; and, for similar reasons, if 

 for no other, the anterior extremity of the body, or the 

 upper surface near this anterior extremity, is the most 

 advantageous site for Visual Organs. To an active animal, 

 eyes would not only be more useful at the anterior 

 extremity of the body than elsewhere, in relation to its 

 food-taking movements, but also in reference to all 

 other uses to which such organs may be applied during 

 active locomotions from place to place. And to this 

 situation of the eyes only two or three exceptions are met 

 with among animals endowed with powers of locomotion : 

 whilst the few cases of deviation are mostly explicable by 

 reference to some peculiarity in the habits and modes of 

 life of the organisms in question. 



Smell. — In vision, as above stated, we have to do with 

 a refinement of the sense of touch, whereby the animal, 

 becoming sensible of impressions produced by ' waves ' of 

 light emanating from a distance, is brought into mediate 

 contact with certain distant objects. But a sort of refine- 

 ment of the organs of taste also occurs, whereby bodies 

 possessing sapid and other qualities are also capable of 

 impressing organisms still at a distance. Just as vision 

 is, in its most elementary phases, a sort of anticipatory 

 touch, so is smell a kind of anticipatory taste. Yet the 

 two cases are not altogether similar. In vision, the 

 contact — if it may be so termed — with the distant 

 body is mediate, through the intervention of ethereal 

 undulations ; whilst in smell we have to do with a case 

 of immediate contact, not, of course, with the distant 

 body itself, but with extremely minute particles which 

 it gives off. An ' emission ' theory serves to explain 



