EVOLUTION BY CHOICE 461 



tevant and others, the direct effects of external agencies like 

 the effects of selection are confined to modifying types rather 

 than originating them. 



Those of my readers who have played with a kaleidoscope 

 will remember that as the cylinder is moved slowly forward 

 or back gradual changes in the design take place, and any 

 favorite arrangement may be recovered by simply moving 

 the cylinder back to the place where that arrangement ap- 

 peared, — all this being possible so long as the cylinder does 

 not move beyond a certain point; for if it gets ever so little 

 beyond that point there is a sudden rearrangement of the 

 elements thereby forming an entirely new design, which may 

 in turn be modified as before by restricted changes of position. 

 The gradual modification of the design within definite limits 

 is like the modification of a type as effected by fluctuating 

 variations or acquired characters; the sudden change is like 

 a mutation upsetting the previous equilibrium and estab- 

 lishing a new equilibrium which is not at all disturbed by 

 vacillating modifications. 



170. Evolution by choice. To make the foregoing anal- 

 ogy complete we should have to imagine a kaleidoscope with 

 the power of self-movement; for whatever may be the factors 

 which bring about mutations, the process is somehow influ- 

 enced from within. A living thing is active as well as passive. 

 The idea is thus suggested that organic evolution may have 

 as its controlling factor some power of choice, essentially like 

 our own, residing in all hving organisms — a will as truly free, 

 although apparently very different because exercised under 

 very different conchtions. This is a hard sajdng, but perhaps 

 we shall find it to contain important truth. 



Doubtless to many readers the idea of plants willing or 

 choosing in any way whatever will appear quite absurd. 

 "How is it possible," they will urge, "to conceive of voluntary 

 action in vegetable life?" Let us try to consider the matter 

 without prejudice. Surely, as we watch plants they seem to 

 act spontaneously, to improve opportunities, and, some of 

 them at least, appear to have gained experience. All ob- 

 servers would agree that a climbing shoot or a root-tip acts 

 almost as if it were intelhgent. If the reader will admit that 



