HIGH SCHOOL ZOOLOGY. 91 



larval form, but such is not the case. Another example of 

 arrested metamorphosis is the Mexican Axolotol. A few years 

 ago, this was only known to naturalists in its larval stage, but 

 it has been caused to undergo metamorphosis expex-imentally, 

 and has been found to do so naturally in some of the localities 

 in which it occurs. 



Several Urodeles belonging to this division occur in our re- 

 gion ; they belong chiefly to the genera Amblystoma, Plethodon 

 and Diemyctylus. The largest of these, Amblystoma jiunctatum, 

 the spotted Salamander, attains a length of six inches of which 

 two and one-half belong to the tau. The gills disappear when 

 the creature is two inches long, the colour is purplish black, 

 and each side of the back is ornamented with two rows of 

 bright yellow spots. Of the Plethodons, P. erythronotus, the 

 red-backed Salamander, is perhaps the commonest ; this species 

 attains about half the size of the foregoing, but loses its gills 

 much earlier than the former does. It lives in moss and under 

 decayed trees where the eggs also are laid. Some allied species 

 are more aquatic in their habits. The newt, eft, or crimson- 

 spotted triton, Diemyctylus niiniatus, is very common under 

 stones, generally near pools. Its dorsal sui-face is olive or red, 

 the ventral surface yellow or orange, but the sides are spotted 

 in both varieties with eye-like markings, red with a suiTOund- 

 ing black rim. 



15. Of the Old World forms allied to these, one of the most 

 striking is the European spotted Salamander (aS'. maculosa) (Fig. 

 68) which is black with golden yellow blotches. Certain cuta- 

 neous glands secrete a milky irritating fluid which appears to 

 be })oisonous to small animals. It was thought in ancient times 

 to be most deadly poison, and to have the virtue of extinguish- 

 ing fire when thrown into its midst. 



IG. While many Urodela undergo a metamorphosis chiefly 

 characterised by the loss of the gills, the frogs and toads lose 

 at that period not only the gills, but the tail, whence their 



