54 The Uniyerse and Life 



and multifarious diversity in the tendencies to change, 

 in the production of new forms, new types. Evolution 

 is indeed, as Boas^ suggested, "creative and fanciful, 

 exulting in diversity." Like the famous warrior of the 

 enthusiastic chronicler, life "leaps upon its steed and 

 rides furiously in all directions." The paths of di- 

 vergent evolution branch like a growing tree, with 

 changes of different kinds occurring at the end of 

 every twig. 



And now an unwelcome fact about these lines of de- 

 velopment but one that is verifiable — a fact that is 

 important for our picture of life. The directions in 

 which changes move include many blind alleys, many 

 paths in which continued progression is not possible. 

 After a move in such an impracticable direction, the 

 branch dies and disappears. A new lasting type is not 

 produced. To make mistakes is one of the character- 

 istic phenomena of biology. If we personify life, we 

 must say that it delights in experimentation; it is a 

 pertinacious and undiscouraged experimenter. And 

 many of the things that it tries are of the sort that 

 Darwin called in his own work "fool experiments" 

 with scarcely a chance of success. It will "try any- 

 thing once." In fact, it will repeat the same unsuc- 

 cessful experiment, the same tragic mistake, a hun- 

 dred times. Having produced an efficient creature 

 with wings and legs and muscles and nervous system 

 that work in beautiful coordination and with many 

 excellent sense organs to guide it — a creature that 



1 George Boas, The Adventures of Human Thought (New York, 

 1929), p. 391. 



