THE METHOD OF ORGANIC EVOLUTION. 415 



to constitute a backward step in the study of evolution that I take this 

 opportunity of setting forth tlie 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 in-oblems. 



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 oponents, 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 understood in their rela- 

 tions to each other and to evolution. These facts are: Variation, rapid 

 multiplication, and the resulting struggle for existence and survival 

 of the httest. Variation is the fundamental fact, and its extent, its 

 diversity, and its importance are only now becoming fully recognized. 

 Observation shows that when large numbers of individuals of common 

 species are compared there is a considerable amount of variability in 

 size, form, color, in number of repeated parts, and other characters. 

 Further, that each sei)arate part which has been thus compared 

 varies, so that it may be safely asserted that there is no part or organ 

 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 

 sei>arate 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 difiierence of the extreme from the mean value of 

 any organ or part is usually from one-tenth to one-fourth, sometimes 

 as great as one-third, of the mean value, with usually a perfect grada- 

 tion of intervening values. 



The multiplication of individuals of all species is so great and so 

 rapid that only a small proportion of those born each year can possibly 

 survive; hence the struggle for existence, the result of which is that, 

 on the average, those individuals which are in any way ill fitted for the 

 conditions of existence die, while those better fitted live. The struggle 

 is of varied character and intensity — either with the forces of nature, as 

 cold, drought, storms, floods, snow, etc. ; with other creatures, in order 

 to escape being devoured, or to obtain food, whether for themselves or 

 for their offspring; or with their own race in the competition for mates 

 and for the means of existence; while as regards all these forms of 

 struggle mental and social qualities are often as important as mere 

 physical perfection, and sometimes much more important. The fact 

 already stated, of the large amount of variability in most species, has 

 been thought by some to show either that there can be no such severe 



