3 3 8 Problems of Organic Adaptation 



4. Individual Adaptations 



But while Darwinism as thus expanded is able to explain 

 the origin of racial or inherited adaptations, it does not, 

 as ordinarily understood, succeed in explaining the numerous 

 and equally remarkable individual adaptations of organisms 

 any more than Lamarckism does; indeed, some of these 

 individual adaptations have been held by several recent 

 writers to be absolutely fatal to both of these theories. For 

 example, it has been found that if the lens of the eye of a 

 newt is removed it will be regenerated perfectly within a 

 few weeks. Now it may be granted that such an injury as 

 this, involving as it does a very delicate surgical operation, 

 never took place in nature ; newts may have had their heads 

 bitten off from time immemorial, but they never had the 

 lens, removed from the eye except in an experiment directed 

 by human intelligence; and yet Darwinism in its original 

 form can explain this regeneration only by supposing that 

 the loss of the lens has taken place so frequently among the 

 ancestors of present-day newts that they have become per- 

 fectly adapted to this injury by the more frequent survival of 

 those which were inherently capable of regenerating the lens. 



Again, the eggs, embryos, or adults of many animals may 

 be cut or broken into fragments or otherwise injured in 

 such ways as could never have occurred in nature, and yet 

 these fragments will, in many cases, give rise to perfect 

 animals "as if the pattern of the whole existed in every 

 part." This power of regeneration cannot be the result of 

 past experience, since there is no constant correlation be- 

 tween its occurrence and the liability to injury. Other con- 

 tingent, individual adaptations that are most difficult to ex- 

 plain are found in the acclimatization of certain organisms 

 to extraordinarily high temperatures and in the toleration 



