. Elements of comparative zoology. Zoology. AMPHIBIANS. 337 In the larvae respiration takes place by gills, recalling those of fishes; and in a few forms these are retained during life. Besides gills, all, in the adult condition, develop lungs,* which grow out from the pharynx, and always re- tain their connection with it by means of a windpipe (tra- chea) .opening upon its floor (compare p. 310). The gills are fewer in number than in any fish, and only three or four gill-slits are formed. Between these slits are devel- oped external gills (fig. 138). Later the slits are closed. FIG. 138.—Larv
. Elements of comparative zoology. Zoology. AMPHIBIANS. 337 In the larvae respiration takes place by gills, recalling those of fishes; and in a few forms these are retained during life. Besides gills, all, in the adult condition, develop lungs,* which grow out from the pharynx, and always re- tain their connection with it by means of a windpipe (tra- chea) .opening upon its floor (compare p. 310). The gills are fewer in number than in any fish, and only three or four gill-slits are formed. Between these slits are devel- oped external gills (fig. 138). Later the slits are closed. FIG. 138.—Larval stage of a salamander with external gills. From Hertwig. in those salamanders which lose the gills, by the growing together of the slits. In the frogs the process is preceded by the formation of an opercular fold (compare fishe>) in. 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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