. An introduction to zoology : for the use of high schools . Fig. 66.—Siren lacertina. (After Brehm,) 13. Of the caducibranchiate Urodeles two genera, AmpMumaand Menopoma, must be regarded as nearest to the foregoing, onaccount of the fact that in spite of the loss of the gills, one gill-slit on each side (that between the third and fourth gill-arches)persists, whereas in the other forms all trace of these disappearsin the course of development. Amphiuma (Fig. 67) is an eel-like form from swamps in the Southern States ; both pairs oflegs are present, carrying in one species two, in the other t
. An introduction to zoology : for the use of high schools . Fig. 66.—Siren lacertina. (After Brehm,) 13. Of the caducibranchiate Urodeles two genera, AmpMumaand Menopoma, must be regarded as nearest to the foregoing, onaccount of the fact that in spite of the loss of the gills, one gill-slit on each side (that between the third and fourth gill-arches)persists, whereas in the other forms all trace of these disappearsin the course of development. Amphiuma (Fig. 67) is an eel-like form from swamps in the Southern States ; both pairs oflegs are present, carrying in one species two, in the other three,toes. Menopoma comes further north, being abundant in theOhio Valley where it is known as the Hellbender {M. alleghani-7 % HIGH SCHOOL Fig. 67.—Amphiuma tridactyla. (After Brehm). ense). It attains a length of two feet and lias better developed limbs (with four and five toes) than the foregoing. A nearly allied form, destitute of the gill-slit, is the giant Salamanderof Japan, which grows more than five feet in length. 14. All the other Urodeles are aquatic only in their youngstaces, and afterwards leave the water for the land wherethey live either in moist or dry places. As a general rulethe tail is rounded in those which have most completelyabandoned the aquatic life, in the others it is somewhat com-pressed. When the new habit of life is adopted, the gills arediscarded and all traces of them disappear, the respii-ation beingentirely effected by the lungs. This change, which also involveschanges in the vascular system and in the skin, is spoken of asa metamorpliosiSj and it may occur when the creatures are stillvery small, or it may be postponed till they have attained theiradult size, and have even laid eggs. Su
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