8 34 THE POPULAR SCIENCE MONTHLY. 



a vessel capable of vibrating and trembling, lie 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 instru- 

 ments. 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 dis- 

 cover 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 gratifi- 

 cation 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 ani- 

 mals, 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 at- 

 tribute 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 manoeu- 

 vres, 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 trem- 

 bling. 



The center of the web, the meeting point of all the radiating 

 threads, is a veritable center of information, and the point to 



