The Dog smells the truffle by sniffing the earth, quite close to the tuber; he finds his master at great distances by consulting the scent of his footprints. But is he able to discover the truffle hundreds of yards away, miles away? Can he join his master in the complete absence of a trail? Certainly not. For all his fineness of scent, the Dog is incapable of such a feat, which is performed, however by the Moth, who is put off neither by distance nor by the lack of any traces out of doors of the female hatched on my table. It is a recognized fact that smell, ordinary smell, the smell that affects our nostrils, consists of molecules emanating from the scented body. The odorous matter dissolves and is diffused throughout the air by communicating to the air its aroma, even as sugar dissolves and is diffused in water by communicating to the water its sweetness. Smell and taste touch each other at some points; in both cases there is a contact between the material particles that give the impression and the sensitive papillæ that receive it. Nothing can be simpler or clearer than that the dragon arum elaborates an intensely strong essence with which the air is impregnated and infected all around. Thus the Dermestes and Saprini, those passionate lovers of carrion smells, are informed by molecular diffusion. In the same way, the putrid Toad gives out and disseminates the stinking atoms that are the Necrophorus’ delight. But what is materially emitted by the female Bombyx or Great Peacock? Nothing, according to our sense of smell. And this nothing is supposed, when the males congregate, to saturate an immense circle, several miles in radius, with its molecules! What the horrible stench of the dragon arum is unable to do the absence of odour is believed to accomplish! However divisible matter may be, the mind refuses to accept such conclusions. It would be tantamount to reddening a lake with an atom of carmine, to filling immensity with nothing. Another argument. When my study is saturated beforehand with pungent odours which ought to overcome and destroy the most delicate effluvia, the male Moths arrive without the least sign of embarrassment. A loud noise kills the faint note and prevents it from being heard; a bright light eclipses a feeble gleam. These are waves of the same nature. But the roar of thunder cannot cause the least jet of light to pale; nor can the dazzling glory of the sun stifle the least sound. Being of different natures, light and sound do not influence each other.