424 APPLIED BIOLOGY 



markets of the west-coast cities. No better proof could be 

 desired as to the value of the work of the government in 

 artificial propagation of fishes. And this is only one of many 

 fishes which has been widely distributed and made more 

 abundant as the result of science applied by the experts on 

 fish culture, employed as agents of the national and of 

 certain state governments. 



The three most valuable North American fishes have been 

 selected to illustrate this discussion of economic value ; but 

 there are many others worth tens of thousands of dollars 

 annually. The fact is that we have scarcely begun to learn 

 the real value of fishes as a source of meat food. There are 

 hundreds of rivers, lakes, and ponds which might be stocked 

 with fish of selected species and made to produce an abun- 

 dance of good food, while, at the same time, destroying 

 numerous larvae of the dreaded mosquitoes. It is certain 

 that the successful methods of artificial hatching and distri- 

 bution which have been discovered by experts in the govern- 

 ment service will ultimately make many useless bodies of 

 water profitable to their owners. 



The student who is interested in fishes should refer to 

 Jordan and Evermann's " American Food and Game Fishes." 



AMPHIBIANS 



349. The class Amphibia has been mentioned as contain- 

 ing the frogs and toads. It also includes the tailed forms 

 which are popularly called newts, salamanders, mud-puppies 

 (Necturus), water-dogs, and mud-eels. Some of these are 

 often mistaken for lizards ; but lizards (e.g., chameleons) are 

 reptiles with scaly skin, while the common amphibians have 

 smooth skin like that of the frog. Some of the tailed am- 

 phibians have gills in the adult state, and live in water. 

 Those without gills respire by means of the skin when in 

 water, and by lungs and moist skin when on land. 



