vi INTRODUCTION. 
of most insects, and it is acute in some fishes, as, for example, the 
shark, which is the most active, if not the most intelligent, of 
fishes. The olfactory membrane of the shark, if spread out, would 
cover some twelve square feet. : 
As insects breathe in a very different manner from the larger 
animals, namely, by a number of spiracles along each side of the 
body, it becomes a question of some difficulty where their organs 
of smell are situated. We cannot easily conceive of smell being 
produced except by a current of air, in which odoriferous particles 
are diffused, passing through a moistened channel; and yet an 
opinion has been adopted by Cuvier, Duméril, Lehmann, and 
others that the spiracles, or breathing-holes, of insects are their 
organs of smell, and chiefly by reason that the inspiration of air 
seems to be an indispensable condition of smelling. If it should 
be argued that this organ must be near the mouth to serve as a 
guide as to the quality of food, Lehmann answers (‘ De usu An- 
tennarum,’ p. 31) that this is not so requisite in insects, because 
they are usually so much smaller than their food, and frequently 
even reside in what they eat, and many therefore smell as advan- 
tageously with the tail as with the head. De Blainville decides 
more positively than the facts seem to authorize that the antennze 
are the organs of smell (‘ De Organisation des Animaux’). The 
modification, he remarks, of the skin which invests them is, in 
general, olfactory only in a small degree, this power appearing to 
be more vivid in the thickest portion of the organ, where it is 
more soft and tender, as in the carrion beetles (Necrophaga), which 
possess so delicate a sense of smelling. From spiders being des- 
titute of antennze he thinks it very difficult to conceive where the 
seat of their organ of smell is placed, if, indeed, they possess one, 
which he is disposed to doubt. Crabs and lobsters, on the other 
hand, whose scent is very delicate, are furnished with two pairs of 
antenne. The varied effects of different odours on bees were ex- 
perimentally ascertained by Huber in numerous instances (Huber 
on Bees), amongst which he says :—“ We sprinkled some powdered 
musk on a drop of honey, into which some bees thrust their 
