370 THE VARIATION OF ANIMALS IN NATURE 



indeed, to suggest that the causes of divergence are the same 

 at all stages. But there may be a fallacy in this reasoning, for 

 it does not follow that, because the divergences are of the same 

 magnitude throughout, they are due to one and the same 

 cause. 



There is another ground for suspecting that, though the 

 stages in evolution are of more or less uniform magnitude and 

 the process seems to be unitary in this respect, it is not the 

 result of a single main cause. Many authors have expressed 

 doubt as to whether the process of group formation and the 

 origin of adaptation can be treated as part of the same process — 

 whether, in short, the main adaptive tendencies are the expan- 

 sion of minor useful divergences between races and species. 

 Not only are there strong reasons for this doubt, but the fact 

 that some divergence seems to precede adaptation suggests 

 that adaptations have been, as it were, grafted on an already 

 existing tendency. 



In discussing these general aspects of the evolutionary 

 process there is another point to bear in mind. We have so far 

 been using the term ' adaptation ' in a broad sense. But, as we 

 have shown (Chapter IX), the term is given to several pheno- 

 mena, of which we now single out two for special consideration. 

 In the previous chapter (p. 365) we suggested that it is not easy to 

 deal with the relations between organisation and specialisa- 

 tion — how far structures, etc., originally elaborated in relation 

 to a particular environment become incorporated into the 

 general organisation. But we may press the question further 

 and ask : is organisation, as we have defined it, the sum of 

 divers specialisations, or is it an activity or quality having 

 a separate origin ? We do not think that this question can be 

 answered except by ascertaining if there is any cause efficient 

 to accumulate and organise specialisations. At first sight such 

 a process appears unlikely. Specialisation seems to be of a 

 different order from organisation, the one involving local 

 modification, the other a co-ordinating activity. Yet we can 

 at least conceive (Chapter IX, p. 366) that Natural Selection 

 might act in such a way that survival value was determined 

 by better organisation, and that those individuals were selected 

 in which not only specialisation was most efficient, but also 

 divers specialisations collectively contributed to survival. 



The theory of Natural Selection (in its earlier and its modern 



