That fishes are wary and active, and possess senses of acute nature, are facts well known to all. The lowest fish, the little clear-bodied lancelet, possesses no brain whatever, and no organ of hearing is developed, while the eyes are at the best of very simple and rudimentary structure. In other fishes, again, the brain and nervous system not only acquire a typical development, but the senses also advance in perfection. The sense of sight is of perfect kind, the eyes of fishes being adapted for seeing in the dense medium in which they live; while the sense of smell is also developed, although, curiously enough, the nostrils, in all except two kinds of fishes--the hag-fishes and the curious Lepidosiren or mud-fish--are pocket-like in nature, and do not open backward, as in higher animals, into the mouth. The sense of taste is not exercised in a high degree by fishes, and it is interesting to observe that the sense of touch appears to reside especially in the sides of the body, on which surfaces a well-marked line--the “lateral line”--may be observed in most fishes. This lateral line is connected with a series of canals or sacs abundantly supplied with nerves. The function of these organs is believed to be that of exercising the sense of touch; and from the manner in which many fishes swim against objects, and bring the sides of their bodies in gentle contact with foreign objects, there would seem to exist strong reasons for supporting the above idea. That fishes “hear” is a well-known fact. No outer ear is developed, but an internal ear--the essential part of the organ of hearing--is found in all fishes except the little lancelet. While the intelligence or instinct of fishes is not, generally speaking, of a high order, there are not wanting instances to prove that these animals may exhibit traits of character sometimes wanting in higher groups of animals. Any one who has kept gold-fishes must have noted that in time they become more and more familiar with the hand that feeds them, and the experience of aquarium keepers goes to prove that some fishes may even show signs of recognizing friends. Like the human race, the class of fishes evinces many illustrations of individuals and groups which differ more or less widely from their more commonplace neighbors. To some of the more curious of these “odd fishes” we may next direct attention.