. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. XXII. FISHES The ordinary stickleback is a hardy fish easily kept in aquaria in the schoolroom. It (or any other small fish, as the brook minnow or goldfish) may be used in the following exercise.^ The Body.—The body of the fish runs insensibly into the head, the neck being absent. Notice the long, narrow body. How is it adapted for the method of hfe? Certain cells in the skin secrete mucus or slime. How might the slimy surface of the body be useful to the fish ? If the fish is in an aquari
. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. XXII. FISHES The ordinary stickleback is a hardy fish easily kept in aquaria in the schoolroom. It (or any other small fish, as the brook minnow or goldfish) may be used in the following exercise.^ The Body.—The body of the fish runs insensibly into the head, the neck being absent. Notice the long, narrow body. How is it adapted for the method of hfe? Certain cells in the skin secrete mucus or slime. How might the slimy surface of the body be useful to the fish ? If the fish is in an aquarium with surroundings like that of its natural habitat, decide whether the color of the fish is protective. 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 be- lieved to be homologous with the paired limbs of a man. Compare the fish with the diagram in the book 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 275.) Find, by comparison with th6 diagram, the dorsal, anal, and caudal fins. How many unpaired fins?. The fins of a fish; A, dorsal; B, caudal; C, anal; D, pelvic; E, pectoral. The stickleback, as the name indicates, has the front dorsal fin so modi- fied as to form a number of sharp spines. (There are five in the common brook stickleback of New York state.) A careful study of a fi.^h in the school aquarium will help to an understanding of the uses of the diflFer- ent fins. Decide what part in the locomotion of the is taken by the caudal fin. Do the other fins function in forward movement? Which fins are used in turning? In backing? Are any used in balancing? Do any parts of the body play a part in locomotion ? 1 See Hunter and Valentine, Manual, page 167. 271. Please note that these images are extracted from scanned page images that may have been digitally enhanc
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