THE VOICE OF THE DESERT 



140 



have only comparatively recently been coming to recog- 

 nize. Formerly it liad often been rather casually taken for 

 granted that all living things were equally and almost 

 limitlessly plastic. They could vary in all directions. En- 

 vironment, using natural selection as a method, was the 

 only thing which determined what the final result would 

 be. But certainly it is all neither so simple nor so one- 

 sided a process as that. On the contrary, it now looks as 

 though an individual species was often capable of develop- 

 ing in one direction and not in the other. Perhaps even 

 the possibility of growing tubers was inherent in some and 

 the possibility of developing succulence was inherent in 

 others long before they were called upon to do either. 



This is only another of the many ways in which evolu- 

 tion, though it most certainly did take place, has come to 

 seem in some respects more and more, rather than less 

 and less, puzzhng as detailed information has accumu- 

 lated. It is also another of the many illustrations of the 

 fact that nature, working in her still mysterious ways, has 

 worked better than she would have worked if man had 

 been able to impose upon her the uniformity and efficiency 

 which he seems to be coming more and more to desire. 



This world would be a far less interesting as well as a 

 far less varied place, if every problem which faces either 

 plants or men was always solved in the same way. Thoreau 

 remarked that he would like to have as many different 

 kinds of men as possible. Fewer and fewer seem to agree 

 with him. But it certainly looks as though nature wanted 

 as many different kinds of living things as she could pro- 

 duce. And she pursues her love of variety even down to 

 the smallest detail. If one beetle has twelve spots, she is 

 pretty certain to make another with fifteen — and she is 



