220 THE POPULAR SCIENCE MONTHLY. 



produced by " waves " of light emanating from a distance, and is thus 

 brought into mediate contact with certain distant objects. A re- 

 finement of the organs of taste may also occur whereby bodies possess- 

 ing sapid qualities are capable of impressing organisms still at a dis- 

 tance. Just as vision, in fact, 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 in- 

 tervention of ethereal undulations ; while in smell we have to do with 

 a case of immediate contact, not with the distant body itself of course, 

 but with extremely minute particles which it gives off on all sides. 

 An "emission " theory serves to explain the diffusion of odors, though 

 it will not hold for the diffusion of light. From what I have said it 

 may be inferred that, as regards the delicacy of their respective physi- 

 cal causes, the sense of smell occupies an intermediate position between 

 taste and sight. 



It is regarded as a matter of certainty by naturalists that such 

 creatures as spiders, Crustacea, insects, and the higher mollusks, are 

 capable of being impressed in some way by odors, and that their 

 actions are to a certain extent regulated by such impressions. We 

 have, however, no definite knowledge concerning the parts of the sur- 

 face which in these, and perhaps in still lower organisms, are attuned 

 to receive such influences. Although a rudimentary sense of smell 

 seems unquestionably to be possessed by such aquatic forms of the 

 invertebrata as Crustacea and the higher mollusks, it is, perhaps, a 

 sense-endowment which generally exists in a more developed and 

 more varied form among air-breathing animals. In whatever forms 

 of life it may be met with, however, the sense of smell seems to be very 

 largely indeed related to the detection and capture of food ; so, that, 

 in these relations, it comes to the aid of the already-existing senses of 

 sight, touch, and taste, though it has the peculiarity of being scarcely 

 otherwise called into activity among the invertebrata. 



Although we have no positive knowledge concerning the situation 

 of the organs of smell among invertebrate animals, there is good reason 

 for believing that in Crustacea they are to be found at the base of the 

 antennules; that in cephalopods they are represented by two little 

 fossae in the neighborhood of the eyes ; and that in insects a power of 

 appreciating odors is possibly possessed either by the antennae them- 

 selves, or by a pair of fossae near their bases. Another cephalic organ 

 has also been referred to as possibly endowed with a power of being 

 impressed by odors. Thus Owen says : " The application, by the com- 

 mon house-fly, of the sheath of its proboscis to particles of solid or 

 liquid food, before it imbibes them, is an action closely analogous to 

 the scenting of food by the nose in higher animals ; and, as it is by the 

 odorous qualities, much more than by the form of the surface, that we 

 judge of the fitness of substances for food, it is more reasonable to 



