It is less than faint, it is non-existent. The Grey Worm is nocturnal in its habits. By day it skulks in its lair and does not stir. It does not nibble either; at least, the Grey Worms which I unearthed upon the Wasp’s indications were nibbling nothing, for the very simple reason that they had nothing to nibble. They were completely motionless and therefore silent in a layer of earth devoid of roots. The sense of hearing must be rejected with that of smell. The question recurs, more abstruse than ever. How does the Ammophila go to work to recognize the spot beneath which the Grey Worm lies? The antennæ are, beyond a doubt, the organs that guide her. They do not, in this case, act as olfactory instruments, unless we admit that their dry and tough surface, which has none of the delicate structure required for the ordinary sense of smell, is nevertheless capable of perceiving scents that are non-existent to us. This would be equivalent to admitting that coarse tools tend to perfection of work. Nor do they act as instruments of hearing, for there is no sound to be discerned. What then is their function? I do not know and I despair of ever knowing. Inclined as we are—and it could not well be otherwise—to judge all things by our standard, the only one in any way known to us, we attribute to animals our own means of perception and do not dream that they might easily possess others of which it is impossible for us to have an exact idea because there is nothing like them in ourselves. Are we quite certain that they are not equipped, in very varying degrees, for the purpose of sensations as foreign to ourselves as the sensation of colours would be if we were blind? Has matter no secrets left for us? Are we so very sure that it is revealed to the living being only by light, sound, taste, smell and touch? Physics and chemistry, young though they be, already declare to us that the dark unknown contains an enormous harvest, in comparison with which our scientific sheaf is the merest penury. A new sense, perhaps that which dwells in the grotesquely exaggerated nose of the Rhinolophus, [50] perhaps that which dwells in the antennæ of the Ammophila, would open to our search a world which our physical structure no doubt condemns us to leave for ever unexplored. Cannot certain properties of matter, which have no perceptible action upon us, find a receptive echo in animals, which are differently equipped?