CHARLES DARWIN 113 



invalid. Possibly the ill health itself had a certain ad- 

 vantage, for it compelled Darwin to spend a large part 



from an engraving. 

 FIG. 24. Thomas Henry Huxley. 



of each day resting, and no doubt turning over in his 

 mind the various problems connected with his work. 

 Most of us are so active, rushing to and fro, that we 

 have not sufficient time for thought. In continuation 

 of the work on the theory of evolution appeared in 1868 

 The Variation of Animals and Plants under Domestica- 

 tion, and in 1871 The Descent of Man. The former gave 

 an abundance of data concerning the phenomena of 

 variation, and the effects of selection by man ; the latter 



