INQUIRIES AND EXPERIMENTS. 51 



Hooker,. indicate the course he was following and the 

 various problems he was considering as they arose. 

 Thus we find that he had finished reading WoUaston's 

 "Insecta Maderensia" in 1855 (writing March 7th), 

 and had been struck with the very large proportion 

 of wingless beetles, and had interpreted the ob- 

 servation, viz. "that powers of flight would be 

 injurious to insects inhabiting a confined locality, 

 and expose them to be blown to the sea." It is of 

 great interest thus to witness the origin of a theory 

 which has since been universally accepted, and 

 has received confirmation from many parts of the 

 world. 



On April 11th of the same year he is experiment- 

 ing on the powers of resistance to immersion in salt 

 water possessed by seeds, and he writes an account of 

 it to Hooker. The object of these experiments was 

 to throw light on the means by which plants have 

 been transported to islands. 



In the same year began his correspondence with 

 Asa Gray, who soon became one of his warmest 

 friends. He had numerous questions to ask about 

 the geographical range of plants, and in 1857 he 

 wrote explaining in some detail the views at which 

 he had arrived as to the causes of evolution. 



My friend Rowland H. Wedgwood, a nephew of 

 Darwin, has given me the following interesting 

 letter to his father, which was written, he believes, 

 probably before 1855. By kind permission, it is here 

 published for the first time. The letter is of great 



