. Elementary biology, animal and human. Biology. FISMIIS 125 attained this condition by growth from side to side, instead of dorso-ventrally. 93. Some differences in the fins of fishes. — We have seen that the goldfish has one dorsal fin, the perch two, and that both fishes have a single anal fin. A glance at Figure 108 will show that the cod- fish has three dorsal fins and two anal fins. Dorsal and anal fins vary not only in number, but in extent. In some fishes they are very short, as in the mackerel (Fig. 95), while in the flounder (Fig. 93) these fins extend nearly the whole length of the
. Elementary biology, animal and human. Biology. FISMIIS 125 attained this condition by growth from side to side, instead of dorso-ventrally. 93. Some differences in the fins of fishes. — We have seen that the goldfish has one dorsal fin, the perch two, and that both fishes have a single anal fin. A glance at Figure 108 will show that the cod- fish has three dorsal fins and two anal fins. Dorsal and anal fins vary not only in number, but in extent. In some fishes they are very short, as in the mackerel (Fig. 95), while in the flounder (Fig. 93) these fins extend nearly the whole length of the dorsal and ventral surfaces. Most common fishes possess both pectoral and pelvic fins, but in the eels (Fig. 96) the pelvic fins are entirely wanting and the pec-. FiG. 96. — Eel. (Jordan and Evermann. Courtesy of Doubleday, Page & Co.) toral fins are very small. The paired fins vary in position as well. In the perch, for example (Fig. 90) the pelvic fins are immediately below the pectorals, while in the cod (Fig. 108) they are anterior to the pectoral fins, and in the salmon (Fig. 107) they are even farther back on the body than in the goldfish. 94. Adaptations for swimming. — Laboratory study. 1. Carefully watch for a time a goldfish when it is swimming around in a large battery jar or aquarium. a. Which of the three regions of the body is principally used in pushing the animal forward ? b. Describe the movements of this body region. 2. Which of the paired fins are used in swimming? De-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Peabody, James Edward, b. 1869; Hunt, Arthur Ellsworth, joint author. New York, The Macmillan company
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