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HIGH SCHOOL ZOOLOGY. 



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 Salamander 

 of Japan, which grows more than five feet in length. 



1 4. All the other Urodeles are aquatic only in their young 

 staces, and afterwards leave the water for the land where 

 they live either in moist or dry places. As a general rule 

 the tail is rounded in those which have most completely 

 abandoned the aquatic life, in the others it is somewhat com- 

 pressed. "When the new habit of life is adopted, the gills are 

 discarded and all traces of them disappear, the respii-ation being 

 entirely effected by the lungs. This change, which also involves 

 changes in the vascular system and in the skin, is spoken of as 

 a metamorpliosiSj and it may occur when the creatures are still 

 very small, or it may be postponed till they have attained their 

 adult size, and have even laid eggs. Such is the case e.g., in a 

 large Salamander fi'om Nebraska, Amhlnstoma mavortktm, 

 which attains the size of a Menobranch before it loses its gills. 

 It was thought at one time that our Necturus might be such a 



