Footnote 32: With the exception of a few lungless salamanders. Most salamanders get much of their supply of oxygen through their moist skins.
The Body.--One of our common fresh-water fish is the bream, or golden shiner. The body of the bream runs insensibly into the head, the neck being absent. The long, narrow body with its smooth surface fits the fish admirably for its life in the water. Certain cells in the skin secrete mucus or slime, another adaptation. The position of the scales, overlapping in a backward direction, is yet another adaptation which aids in passing through the water. Its color, olive above and bright silver and gold below, is protective. Can you see how?
[Illustration: The bream. _A_, dorsal fin; _B_, caudal fin; _C_, anal fin; _D_, pelvic fin; _E_, pectoral fin.]
The Appendages and their Uses.--The appendages of the fish consist of paired and unpaired fins. The paired fins are four in number, and are believed to correspond in position and structure with the paired limbs of a man. Note the illustration above and locate the paired _pectoral_ and _pelvic_ fins. (These are so called because they are attached to the bones forming the pectoral and pelvic girdles. See page 268.) Find, by comparison with the Figure, the _dorsal_, _anal_, and _caudal_ fins. How many unpaired fins are there?
The flattened, muscular body of the fish, tapering toward the caudal fin, is moved from side to side with an undulating motion which results in the forward movement of the fish. This movement is almost identical with that of an oar in sculling a boat. Turning movements are brought about by use of the lateral fins in much the same way as a boat is turned. We notice the dorsal and other single fins are evidently useful in balancing and steering.
The Senses.--The position of the eyes at the side of the head is an evident advantage to the fish. Why? The eye is globular in shape. Such an eye has been found to be very nearsighted. Thus it is unlikely that a fish is able to perceive objects at any great distance from it. The eyes are unprotected by eyelids, but the tough outer covering and their position afford some protection.
Feeding experiments with fishes show that a fish becomes aware of the presence of food by smelling it as well as by seeing it. The nostrils of a fish can be proved to end in little pits, one under each nostril hole. Thus they differ from our own, which are connected with the mouth cavity. In the catfish, for example, the _barbels_, or horns, receive sensations of smell and taste. They do not perceive odors as we do for a fish perceives only substances that are dissolved in the water in which it lives. The senses of taste and touch appear to be less developed than the other senses.