NATURAL SELECTION. 99 



exhaustively discussed, and is established by the weightiest 

 evidence. Having fully expressed my opinion of this book 

 in my Generelle Morphologie, and in the " History of 

 Creation," it will here be sufficient to recapitulate briefly 

 the gist of the Darwinian theory, on the right under- 

 standing of which everything depends. The whole is based 

 on the simple fundamental idea that the Struggle for 

 Existence in Nature modifies organisms, and produces 

 new species by the aid of the same means by which man 

 produces new domesticated varieties of animals and plants. 

 These means consist in the constant preference or selection 

 of the individuals most suitable for propagation, so that the 

 interaction of Heredity and Adaptation acts as a modifying 

 cause. 31 



The celebrated traveller Wallace had independently 

 formed the same conclusions. He had, however, by no 

 means determined the influence of Natural Selection in 

 forming species as clearly and thoroughly as had been done 

 by Darwin. But the writings of Wallace (especially those 

 on Mimicry, etc.) contain many admirable, original con- 

 tributions to the Theory of Selection. It is most unfor- 

 tunate that the imagination of this gifted naturalist has 

 since become diseased, and that he now only plays the part 

 of a spiritualist in the spiritualistic society of London. 



The effect produced by Darwin's book on " The Origin of 

 Species by Natural Selection " in the animal and vegetable 

 kingdom, was extraordinarily great, though not at first in 

 the special branch of science to which it most directly 

 applied. Several years passed before botanists and zoolo- 

 gists recovered from their surprise at the new views of 

 nature advanced by this great reconstructive work. The 



