prehend anything but quantity and direction where we perceive light and tonality, form and perspective? Is the luminous world for them and for many other insects nothing else than a special palpitation of disturbed space which they analyze, orienting themselves in it by the perception of the force and direction of the direct or reflected disturbances? Do the handsome colors of butterflies prove that they are sensitive to the colors of flowers; and can we make sight play a certain part in the curious mimetic adaptations of different animals? Selection may serve us better than we should do ourselves without our aiding it; and it is not always by tactics that an animal escapes its enemies.
Mimicry of form and color addresses itself to the sight of the enemy, and there doubtless also exists a mimicry of odor. This, however, only proves that the enemy hears and sees without there being any calculation on the side of the interested animal. There is nothing astonishing in the thought, for we frequently meet persons to whom particular colors are unknown, and who have, therefore, only an incomplete idea of light; and if we look for sensorial memory and aesthetics behind the senses, the divergencies will be found still stronger.
Hearing, according to an opinion that appears solidly established on facts, is well developed in animals quite distant from us. Instances in point are the spider of Grétry and other spiders which seemed to have real musical tastes; eatable crustaceans, which can not be fished for successfully except in the most rigorous silence; the crabs of Minasi, which stopped in the midst of most lively frolics when a bell called them to order; the prawns of Hensen, which leaped when the slightest sound reached them; the shrimp, which exhibited in the hairs of their tails what were taken to be organs of hearing.
Dahl has ascertained similar facts concerning spiders. Romanes remarks that these insects approach instruments having a pleasant sound, and cites an observation of Reclain, who, during a concert at Leipsic, saw a spider come down a chandelier while a solo was performed on the violin, and go back very quickly as soon as the orchestra set in. He, however, expresses doubts as to the meaning of these facts; and many authors, including Lubbock and Forel, have not been able to ascertain that insects hear.
Hearing means perception of noises and sounds; and it is this perception that we refuse absolutely to every being deprived of a sacculo-cochlear apparatus. If an animal hears because certain hairs of its body are set into vibration by certain disturbances of the air, then a barley beard, a piece of velvet, and a brush vibrating harmonically, hear likewise. If we should invest the most hopelessly deaf man with a stiff-jointed armor, like the armor of the men-at-arms of the middle ages, and should put his head into
