ADAPTATION 367 



Summary 



In this chapter we contrast specialisation with the more 

 fundamental property of organisation. Animals are not only 

 adapted to deal with special stresses and crises of their environ- 

 ment, but they are also able to regulate themselves to a diver- 

 sity of environmental stresses and to avoid the evolutionary 

 ' blind alley ' of specialisation. It is important to realise that 

 we have as yet no a priori method of estimating the degree of 

 adaptation : we can only postulate that the species which 

 actually exist must be sufficiently adapted to survive. More 

 accurate estimates will be possible when the experimental 

 evaluation of single factors is more advanced and adequate 

 methods of measuring fluctuations in animal populations have 

 been devised. 



Meanwhile we can do little more than exercise great 

 caution in attributing survival value to details of structure or 

 habit, even when these appear to be not entirely useless. 

 Modifications leading to more efficient organisation are more 

 likely to be adaptive (in the strict sense), but these are usually 

 recognisable only when we compare the larger divisions of the 

 animal kingdom. 



