99 THE AMERICAN NATURALIST [VOL. XL VII 



Again a complex mechanism, consisting of teeth, of diges- 

 tive glands tearing proteins and carbohydrates to pieces, 

 so that he can build up his own proteins from any other 

 kind, useless amino acids being converted into sugar and 

 urea. 



The last and by far the most important of these great 

 mechanisms of adaptability is that which provides for 

 every contingency; for the unexpected. It seems that 

 nature, after elaborating these other mechanisms to meet 

 particular vicissitudes, has lumped all other vicissitudes 

 into one and made a means of meeting them all. One 

 can not but be pleased by the apparent ingenuity of this 

 solution. I refer to the nervous mechanism. It is obvious 

 how this mechanism, by substituting choice for blind in- 

 stinct, consciousness for unconsciousness, developing 

 memory, so that one can profit by experience, and intelli- 

 gent adaptation of means to ends, has provided finally for 

 all possible contingencies of the future. She has spoken 

 her last word. Adaptability, or superiority to environ- 

 ment, was the end so blindly sought ; memory, conscious- 

 ness, choice were the means, shall I say the means as 

 blindly adopted? 



To the physiologist, then, adaptability appears to be 

 the touchstone with which nature has tested each kind of 

 organism evolved; it has been the yard stick, with which 

 she has measured each animal type; it has been the 

 counterweight against which she has balanced each of her 

 productions. However well adapted to a specific environ- 

 ment a type might be, did it lack ever so little of its possi- 

 bilities in this direction, it was sooner or later relegated 

 to the scrap heap. Some forms, to be sure, persisted in 

 special environments, where they were protected from 

 competition, as in Australia; or where the environment 

 was fairly constant, as in the sea; or in special environ- 

 ments for which they were highly suited; but the whole 

 trend of evolution, with these exceptions, may be summed 

 up by the statement : the general course of evolution has 

 been always from the beginning to the end, in the direc- 



