88 EVOLUTION, SOCIAL AND OITGANIC 



direction of adaptation to environment, as a 

 result of animals exerting themselves in that 

 direction. 



This point is well stated by DeVries in the 

 following passage, — "This failure of a large 

 part of the productions of nature deserves to 

 be considered at some length. It may be el- 

 evated to a principle, and may be made use 

 of to explain many difficult points of the the- 

 ory of descent. If in order to secure one good 

 novelty nature must produce ten or twenty or 

 perhaps more bad ones at the same time, the 

 possibility of improvements coming by pure 

 chance must be granted at once. All hypo- 

 theses concerning the direct causes of adap- 

 tation at once become superfluous, and the 

 great principle enunciated by Darwin once 

 more reigns supreme." 



Another difficulty which DeVries claims to 

 have solved by his theory, is the supposed 

 contradiction between the physicist and the 

 biologist as to the time allowed by the former 

 and the time required by the latter, for the 

 evolution of animals. 



Lord Kelvin asserted the age of the earth to 

 be between twenty and forty million years. 

 George Darwin estimates the separation of 

 the moon from the earth as having taken place 

 some fifty-six million years ago. Gekie estim- 



