with such a perfect olfactory mechanism situated in long, flexible whip-lashes, which we could move and tap with each step, the world for us would be transformed. Odour would become a sense of forms. Thus the orientation of ants can be explained without assuming the existence of an unknown sense. (It has recently been suggested, by the way, that bats owe the exquisite power they manifest of steering their flight among obstacles to the use of their squeaks, the echoes from which enable them to form “sound-pictures” of their environment. In the same way a blind man in the street tapping the pavement with his stick forms a more or less well-defined sound-picture of the walls, doorways, and alleys about him.)
In the immediately foregoing paragraphs we have been dealing with the ability of insects to smell the smells that we smell. But Fabre’s experiments have familiarised us also with the notion that there are insects which can smell smells we cannot smell.
We shall see in the following section that the same may also be true of some of the higher animals.
In fish olfaction is, unlike that of air-breathing animals, effected by odorous material in solution. Whether or not their olfactory sense is as acute it
