14 The Lije Story of the Fish 



porpoises are not, for they possess mammary glands for 

 the suckling of their young. They therefore belong to the 

 same class of vertebrates as humans. They are mammals 

 gone to sea. 



Fish are low in the vertebrate scale, but, to our way of 

 thinking at least, they are high in the scale of animal life 

 as a whole. Perhaps if they did not belong to this great 



Figure 3. A RADIOLARIAN PROTOZOAN 



vertebrate group which we honor with our presence, we 

 would not place them above the more complicated of the 

 insects or crustaceans, but no matter to what group we our- 

 selves belonged — and here again we find ourselves speaking 

 in terms of evolution, whether we believe in it or not — ^we 

 would place them far above such creatures as the jellyfish, 

 and still further above the Protozoay the one-celled animals. 

 For in this last group, one single cell performs all the 

 life functions: nourishment, movement, control, breathing, 

 excretion, reproduction. A fish is to that simple, earnest unit 

 what a great modern shoe factory, with its power-plant, its 

 administrative offices, its purchasing department, its machine- 

 tools, its sales forces, is to the old-fashioned cobbler who 

 tanned his own leather, spun his own thread, and made his 



