10 ESSAYS OF A BIOLOGIST 



fact of Progress in some form or another. If we 

 accept the doctrine of evolution, we are bound to 

 believe that man has arisen from mammals, terrestrial 

 from aquatic forms, vertebrates from invertebrates, 

 multicellular from unicellular, and in general the 

 larger and the more complex from the smaller and 

 simpler. To the average man it will appear indisput- 

 able that a man is higher than a worm or a polyp, an 

 insect higher than a protozoan, even if he cannot 

 exactly define in what resides this highness or lowness 

 of organic types. 



It is, curiously enough, among the professional 

 biologists that objectors to the notion of biological 

 progress and to its corollary, the distinction of higher 

 and lower forms of life, have chiefly been found. 

 I say curiously enough, and yet to a dispassionate 

 observer it is perhaps not so curious, but only one 

 further instance of that common human failing, the 

 inability to see woods because of the trees that com- 

 pose them. 



That is as it may be. Our best course will be to 

 start by examining some of the chief objections to 

 the idea of biological progress, in order to see if they 

 involve errors of thought which we may then avoid. 



The most widespread of all the objections raised, 

 may, I think, be fairly put as follows : ' The funda- 

 mental attribute of living beings is adaptation to 

 environment. A man is not better adapted to his 

 environment than the flea which lives upon him as 



