Page:Popular Science Monthly Volume 39.djvu/854

834 a vessel capable of vibrating and trembling, he would come to a stand at the first shock like the crabs of Minasi, or would leap like the prawns of Hensen. It is not the sound that will affect him, for he is deaf, but the trepidation, which, disagreeable to a mollusk, would be intolerable to a crustacean enveloped in rigid pieces, adjusted and in contact. Nothing is more like the noise of a fly's buzzing than the sound of a tuning-fork or of soft instruments. The same flight of a fly and its energetic efforts to free itself when captured, also produce a disturbance of the air like that of the tuning-fork; what is a humming sound to us is to the spider a beating of wings.

Romanes has cited, as apposite to this subject, an interesting observation by Boys, which is very instructive, and admits of an easier interpretation than the author seems to have believed. Boys remarked that, on lightly touching with a tuning-fork a point of a spider's web, the insect turned at once to the side of the instrument, and tried the rays of its web with its fore legs to discover what was vibrating; then, coming closer and closer, reached the instrument and tried to seize it as it would have done with a fly. We know that spiders do not enjoy a very delicate sight, and that their sense of smell is not remarkable; they are accorded, on the other hand, a very fine hearing, which serves, according to the authors, the satisfaction of their musical tastes and the gratification of their carnivorous appetites. I believe, however, that they are absolutely deaf and nearly blind, but are remarkably well endowed with what we might call a sense of trembling a sense which suffices for the needs of the immense majority of animals, and which is complicated somewhat late among the higher animals with sonorous perceptions. Sound is, in fact, like color, of recent acquisition in the animal series; it is a thing of sensorial operations that require a remarkable degree of perfection.

We have an organ, the cochlea, which permits us to appreciate fast rhythms, under the form of sensations to which we can attribute a place in a whole of continued sensorial affections of the same character, and group them in series. The spider perceives a trembling, feels the thread that vibrates most, runs along it, stops an instant at the branchings, and arrives at the point where the force, the form of tremor characteristic of this or that prey, suggest to her the instinctive and sometimes intelligent manœuvres, as we saw in the case of the tuning-fork, which will bring that prey into her possession. The same automatism studied by Fabre is observed in the spider; and the point of departure of that series of adapted acts is always the perception of a trembling.

The center of the web, the meeting point of all the radiating threads, is a veritable center of information, and the point to