. Elements of biology, with special reference to their rôle in the lives of animals. Biology; Zoology. ii8 ELEMENTS OF BIOLOGY AMPHIBIA limbs either functional or rudimentary (except in the class Cyclos- tomata), and reproduce solely sexually. The ccelom is separated into two or three compartments. There are seven classes: Class L CYCLOSTOMATA (Fig. 66). Lamprey Eels and Hagfishes. Do not have paired limbs. The mouth is at the extreme anterior end and has no jaws. The em- bryos of these forms in many respects resemble the adult Cephalochordata, Amphi- oxus. Found in both fresh and salt water.
. Elements of biology, with special reference to their rôle in the lives of animals. Biology; Zoology. ii8 ELEMENTS OF BIOLOGY AMPHIBIA limbs either functional or rudimentary (except in the class Cyclos- tomata), and reproduce solely sexually. The ccelom is separated into two or three compartments. There are seven classes: Class L CYCLOSTOMATA (Fig. 66). Lamprey Eels and Hagfishes. Do not have paired limbs. The mouth is at the extreme anterior end and has no jaws. The em- bryos of these forms in many respects resemble the adult Cephalochordata, Amphi- oxus. Found in both fresh and salt water. Lampreys are used for food in some coun- tries. Class IL ELASMOBRANCHII (Fig. 67). Sharks and Rays. The internal skeleton is en- tirely of cartilage and the in- tegument is covered with SCALES consisting of a bony basal plate bearing an enam- eled spine. The gill openings are not covered. Class in. PISCES (Fig. 68). The true Fishes. The skele- ton always contains more or. FIG. 69. FROG Fig. 69.—A common frog, Rana pipiens. As in all modern Amphibia, the integu- ment is free from scales. Compare this feature with the well-developed scales of fishes (Fig. 68) and with Reptilia (Fig. 70). Note also the absence of claws; compare with the reptile (Fig. 70). less bone. The gills are cov- ered by a bony shield. Scales are not always present; when present they consist of smooth plates without the enamel that char- acterizes the scales of the Elasmobranchii. Practically all the forms that are commonly known as fishes belong in this class, although. 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 Buchanan, James William, 1888-. New York, London, Harper & brothers
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