ADJUSTMENT, DIRECT AND INDIRECT 



means of internal changes must result in that 

 kind of organic variation known as direct adap- 

 tation. We need not be surprised, therefore, 

 by the parallel variations of whole genera of 

 American trees or Malayan butterflies — nor 

 need we ascribe them, with certain recent writers, 

 to " occult energies " of the metaphysical sort, 

 or to a kind of pantheistic " intelligence " in- 

 herent in nature, or to any other agency unre- 

 cognizable by science ; since the necessity for 

 such parallel variations, wherever .whole groups 

 of organisms are exposed to like environing 

 agencies, is a corollary from the fundamental 

 principles of vital dynamics. 



We are now in a position to amend quite 

 materially the view thus far taken of the causes 

 of organic evolution. Hitherto we have con- 

 cerned ourselves too exclusively with the selec- 

 tion of variations, omitting to inquire into the 

 character and mode of origin of the variations 

 selected. But the latter point is no less im- 

 portant than the former. If variations might 

 occur equally in all directions from the aver- 

 age standard, by reason of circumstances so in- 

 definitely compounded as to make them seem 

 fortuitous, then the natural selection of such 

 variations might well be pronounced incapable 

 — save in very rare instances — of working en- 

 tirely analogous results in organisms so geneti- 

 cally distinct as monodelphians and didelphians, 



83 



