368 AMPHIBIA xm. 9 



question 'Are the amphibians more efficient than the fishes?', the 

 work that they do in maintaining life is so different that a comparison 

 of 'efficiency' is fallacious. One method of assessing living efficiency 

 might be to judge each animal organization by the extent to which it 

 maintains its constancy — by its power of homeostasis. Data about the 

 fluctuations of the internal environment are so scanty among lower 

 vertebrates that we cannot proceed very far on these lines. It is 

 probable that the blood of fishes shows greater fluctuations, for 

 instance in osmotic pressure or lactic acid content, than does that of 

 amphibians, such fluctuations being perhaps even an advantage in 

 allowing life in waters of differing salinity. In fact, to say that the 

 whole mechanism of homeostasis becomes more complicated in land 

 animals is only to say over again that they are 'higher' because they 

 have more special work to do to maintain themselves in a difficult 

 environment. Almost every part of the body shows signs of this greater 

 complexity; the central nervous system becomes larger, the autonomic 

 nervous system develops more elaborate control of the viscera. The 

 endocrine glands become more numerous and differentiated, the 

 muscular system shows more distinct parts, enabling the animal to 

 act in new ways. 



However difficult such comparisons may be it is hardly possible 

 to deny them some validity. Amphibian organization differs from 

 that of fishes and may be said to be 'higher' in the sense that it is more 

 elaborate and allows life in conditions that the fish organization 

 cannot tolerate. 



