darwin's argument. 95 



question from an entirely new direction, and of having 

 worked out that independent theory in explanation of the 

 Doctrine of Descent which we properly call the Darwinian 

 Theory, or Darwinism. 



While Lamarck explained the variation of organisms 

 descended from common ancestral forms, as especially the 

 effect of habit and the use of the organs, but also by the 

 aid of the phenomena of Heredity, Darwin independently, 

 and on an entirely new basis, unfolded the actual causes 

 which mechanically accomplish the modification of the 

 various animal and vegetable forms by the aid of Adap- 

 tation and Heredity. Darwin deduced his " Theory of 

 Selection" from the following considerations. He com- 

 pared the origin of the various breeds of animals and plants 

 which man is able to produce artificially, — the conditions 

 of " Selection " in horticulture, and in the breeding of 

 domestic animals, — with the origin of wild species of 

 plants and animals in a natural state. He thus found 

 that causes similar to those which, in artificially breeding 

 domestic animals, and raising cultivated plants, we apply 

 to alter the forms, are also at work in Nature. He named 

 the most effective of all the co-operating causes the 

 Struggle for Existence. The gist of Darwin's theory, 

 properly so called, is this simple idea : that the Struggle 

 for Existence in Nature evolves new Species without design, 

 just as the Will of Man produces new Varieties in Culti- 

 vation with design. Just as the gardener and the farmer 

 breed for their own advantage, and according to their 

 own will, making judicious use of the productive effects 

 of Heredity and Adaptation, so does the Struggle for 

 Existence constantly modify the forms of vegetables and 



