332 The Theory of Natural Selection 



much like his own ideas that Darwin was distressed. He 

 consulted his friends and it was arranged that both the- 

 ories should be presented before the Linnsean Society in 

 July 1858. 



Wallace's formulation of his theory forced Darwin to 

 take action to get his own book into shape. While Wallace 

 was continuing his explorations Darwin's book appeared. 



The Logic in Natural Selection 



Like Lamarck's theory published fifty years earlier, 

 Darwin's was an attempt to explain natural phenomena by 

 an appeal to natural laws. Darwin had been convinced of 

 the transformation of species by his own observations in the 

 field and by his later studies. He made it part of his task to 

 show that all the facts of nature could better be understood 

 under this conception than on the assumption of special crea- 

 tion. He spoke of transformation or of descent with modi- 

 fication rather than of evolution because the latter term 

 carried with it at the time too many philosophical connota- 

 tions. ** Evolution " was being rather loosely employed to 

 cover the whole of the historical process in the world of 

 nature, and had been previously used for a special theory of 

 embryonic development (see page 122). 



In formulating his theory, Darwin attempted at 

 each step to appeal to established facts and to common 

 sense. The plausibility of his argument is due to this 

 approach. 



1. Everybody can see for himself that the individuals 

 of any species vary. 



2. It is a common fact of observation that it is impos- 

 sible for all the eggs or all the seeds of any species to develop 

 to maturity. 



3. The struggle for existence is apparent on every 

 hand; there is conflict not only between the members of a 

 species, but also between one species and another for space, 

 for food, for air, and so on. The individual is in constant 



