THE FnOG 343 



purplish spots on the sides. Botli Spelerpes and Dcsmognathus 

 live in and about running brooks, under stones and fallen logs. 

 Their eggs are attached to the under surface of submerged stones. 

 The adults are easy to keep in confinement in a moist fernery. 

 They may be obtahicd out of doors all the year round, excepting 

 during the time of deep snow. 



Metamorphosis. — As we have seen, all Amphibia have gills 

 while young, but some lose theni before maturity while others 

 retain them permanentlj'. Those species which retain the 

 gills pass their whole life in water ; the others may live on the 

 land. The loss of gills is associated with the assumption 

 of a land life. In the Amblystoma we have species which are 

 curiously intermediate between the two classes in that they 

 may retain their gills, tail-fins, and other structm-es adapted 

 to aquatic life,' even to the time of reproduction ; or they may 

 lose their gills and tail-fins. The first result follows if they are 

 prevented from coming on land ; the second, if they are 

 forced to leave the water. The capacity of the Mexican 

 Axolotl for either becoming an adult or remaining a larva was 

 first shown b}' some experiments of the German naturalist 

 Weismann and a pupil of his. It will he seen that, when forced 

 to live in the water, Axolotl retains permanently a larval con- 

 dition ; and one would never know that in this larval condition 

 the animal is not adult were it not for the accident of its some- 

 times becoming adult. It is quite possible that all of the 

 Urodela which retain their gills throughout life may formerly 

 have had a gill-less adult stage which is now lost. 



Early Development of Urodela. — The eggs of Urodela are 

 deposited in a gelatinous mass in water, and are attached to 

 submerged plants, or to other objects in the water, either singly 



^ Compare Fig. 321. 



