. Elements of comparative zoology. Zoology. 316 SYSTEMATIC ZOOLOGY. that of other vertebrates, since movable jaws are lacking. Inside of the mouth are horny teeth (few in the hagfishes, many in the lampreys), but these are chiefly used for holding, not for biting or crushing. The tongue is very large. There is but a single nostril on top of the head. The gills are placed not in simple slits, but in large pouches on the sides of the neck (hence the name, Marsipobranchs, often given the group), and these pouches may either open separately to the exterior or by means of a tube which leads to a si
. Elements of comparative zoology. Zoology. 316 SYSTEMATIC ZOOLOGY. that of other vertebrates, since movable jaws are lacking. Inside of the mouth are horny teeth (few in the hagfishes, many in the lampreys), but these are chiefly used for holding, not for biting or crushing. The tongue is very large. There is but a single nostril on top of the head. The gills are placed not in simple slits, but in large pouches on the sides of the neck (hence the name, Marsipobranchs, often given the group), and these pouches may either open separately to the exterior or by means of a tube which leads to a single opening. The number of gill- pouches ranges between six and fourteen on either side. The Cyclostomes are subdivided into two groups, accord-. Fig. 119.—Lamprey (Petromyzon marinus). After Goode. ingly as the nostril communicates with the throat or not. As examples of the first, the hagfishes may be cited. These are all marine, and are capable of secreting a large amount of mucus from their bodies, so that a few hagfish in a pail will convert the water into a jelly-like mass. These fishes are parasites, and work their way into vari- ous fishes, like the cod, and when once inside they eat up all the flesh and viscera, leaving nothing except the skin and bones. The second group is represented by the lampreys. Some of these are marine, others live in fresh water, while many of the marine forms ascend streams in spring to lay their. 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 Kingsley, J. S. (John Sterling), 1854-1929. New York, H. Holt and Company
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