NATURAL SCIENCE IN THE NINETEENTH CENTURY 395 



Darwin's principle of natural selection is stated in his own 

 words as follows : 



As many more individuals of each species are born than can pos- 

 sibly survive; and as, consequently, there is a frequently recurring 

 struggle for existence, it follows that any being, if it vary however 

 slightly in any manner profitable to itself, under the complex and 

 sometimes varying conditions of life, will have a better chance of 

 surviving, and thus be naturally selected. From the strong principle 

 of inheritance, any selected variety will tend to propagate its new 

 and modified form. 



THE DESCENT OF MAN. The last refuge of the defenders of 

 the old cosmogony was man himself, and not a few, among whom 

 was Alfred Russel Wallace, co-discoverer with Darwin of the 

 principle of natural selection, refused to align man and especially 

 man's mentality, with lower animals and their inferior mental 

 powers. Here at least, they affirmed, we see no evidence of evo- 

 lution. But as time has gone on, and studies have been extended 

 in craniology and in psychology it has become increasingly evi- 

 dent that there is little if any more difference in brain weight and 

 mental power between the highest apes and the lowest men, 

 than between these last and the highest men. Meantime, the 

 doctrine of parsimony, in default of any other than a super- 

 natural hypothesis, naturally awarded the field to the Darwinian 

 theory. 



DECLINE OF THE THEORY OF SPECIAL CREATION. Darwin's 

 theory of the method of origin of the various kinds (species) of 

 plants and animals by natural processes under natural law soon 

 became known as the theory of organic evolution, and before a 

 score of years had passed was almost universally accepted among 

 naturalists. 



It is the supreme merit of Darwin to have thus pointed out a 

 method by which a process of gradual development, or evolution, 

 already accepted for language, art, music, and (after 1830) for 

 the earth's crust, and many years before urged by Laplace for the 

 solar system, could be made no less applicable to, and accept- 

 able for, plants and animals, and especially for man. Until this 



