348 STUDIES, SCIENTIFIC AND SOCIAL chap. 



which seems likely to have much influence among certain 

 classes of naturalists ; and it is because I believe such 

 views to be wholly erroneous and to constitute a backward 

 step in the study of evolution that I take this opportunity 

 of setting forth the reasons for my adverse opinion in 

 a manner likely to attract the attention not only of 

 naturalists but of all thinkers who are interested in these 

 problems. 



What the Darvjmian Theory really Is. 



Before proceeding to this special discussion it may be 

 well to illustrate briefly the essential difference between 

 the theories of Darwin and those of his predecessors and 

 opponents, by a few examples of those cases of adaptation 

 which are insoluble by all other theories, but of which 

 natural selection gives an intelligible explanation. 



The Darwinian theory is based on certain facts of nature 

 which, though long known to naturalists, were not under- 

 stood in their relations to each other and to evolution. 

 These facts are : variation, rapid multiplication, and the 

 resulting struggle for existence, and survival of the fittest. 

 Variation is the fundamental fact, and its extent, its 

 diversity, and its importance are only now becoming fully 

 recognised. Observation shows that when large numbers 

 of individuals of common species are compared there is a 

 considerable amount of variability in size, form, colour, in 

 number of repeated parts and other characters. Further, 

 that each separate part or organ which has been thus 

 compared varies, so that it may be safely asserted that 

 there is no part or organ of animals or plants that is not 

 subject to continual variation. Again, all these variations 

 are of considerable amount — not minute, or infinitesimal, 

 or even small, as they are constantly asserted to be. And, 

 lastly, the parts and organs of each individual vary greatly 

 among themselves, so that each separate character, though 

 sometimes varying in correlation with other characters, 

 yet possesses a considerable amount of independent varia- 

 bility. The amount of the observed variation is so great 

 that in fifty or a hundred adult individuals of the same 

 sex, collected at the same time and place, the difference 



