CHAKLES DARWIN AND LAMARCK 391 



a state of nature, and from the undisputed fact that varieties do 

 frequently occur." 



It will be evident from the above sketch of the theory of 

 Natural Selection, which I have thought it desirable to give in 

 the actual words of its chief exponents, that adaptation is 

 explained as the logical consequence of certain facts which can 

 at any time be verified by direct observation. (1) All 

 organisms tend to increase in a high geometrical ratio ; (2) there 

 is, partly as a direct result of such increase, a keen struggle for 

 existence, to which all organisms are more or less exposed and in 

 which vast numbers perish without leaving offspring; (3) all 

 organisms tend to vary in many directions ; (4) variations, 

 whether favourable or otherwise, tend to be transmitted by 

 heredity from generation to generation; though, as we have 

 already seen, there is at the present time much dispute as to 

 whether variations of a certain kind ought not to be excluded 

 from this generalization. 



It follows inevitably from these premisses that in every genera- 

 tion there will be a more or less strongly pronounced tendency 

 towards the elimination of those individuals which are least well 

 adapted to their environment and a corresponding preservation 

 and encouragement of those which are best adapted, or, in 

 Herbert Spencer's celebrated phrase, a " survival of the fittest." 

 This process, continued from generation to generation for count- 

 less ages, has resulted in that marvellous perfection of adaptation 

 which we have seen to be such a striking feature of both plants 

 and animals. 



Charles Darwin himself, however, was not satisfied with natural 

 selection as the sole factor concerned in bringing about pro- 

 gressive evolution and adaptation. Although, in the historical 

 sketch which he added to the later editions of the " Origin of 

 Species," he remarks : 



"It is curious how largely my grandfather, Dr. Erasmus 

 Darwin, anticipated the views and erroneous grounds of opinion 

 of Lamarck in his ' Zoonomia,' ' 



and although he himself at first appears to have attached very 

 little importance to Lamarck's opinions, yet we find in the last 

 chapter of the sixth edition of the " Origin of Species " abundant 

 evidence that he was obliged to admit the efficacy of the chief 

 " Lamarckian " factor, the principle of use and disuse, in 



