DEDUCTION. GENERAL INSTANCES. 163 



nature of the explanations. It will be recalled 

 that he reached three principles of expres- 

 sion; but only when he had completed his 

 observations. 



Darwin's botanical work was almost entirely 

 done under the influence of the theory of evolu- 

 tion. His special investigations in this field 

 were based on corollaries from the general 

 theory. Writing to Mr. Murray, his publisher, 

 concerning his book on the "Fertilization of 

 Orchids," he said, "It will perhaps serve to 

 illustrate how natural history may be worked 

 under the belief of the modification of species. " 1 

 Equipped with the belief that all adaptations 

 are useful to the species possessing them, 

 and that innumerable flowers, among them the 

 orchids, are adapted for cross-fertilization, he 

 studied orchids and the effects of cross- and 

 self-fertilization in the same spirit in which he 

 had studied coral islands. 



One of the most interesting of the many 

 investigations that arose out of his general 

 theories was that on climbing plants. As has 

 been said, he selected as subjects for special 

 research some of the principal difficulties that 

 presented themselves for explanation. He did 

 this because, if the theories were true, they 



1 Life and Letters, Vol. II., Letter to Murray. 



