CHAPTER IV. 

 The Spread of Evolution. 



'Variation of Animals and Plants.' 



1863-1866. 



[His book on animals and plants under domestication was 

 my father's chief employment in the year 1863. His diary 

 records the length of time spent over the composition of its 

 chapters, and shows the rate at which he arranged and wrote 

 out for printing the observations and deductions of several 

 years. 



The three chapters in vol. ii. on inheritance, which oc- 

 cupy 84 pages of print, were begun in January and finished 

 on April ist; the five on crossing, making 106 pages, were 

 written in eight weeks, while the two chapters on selection, 

 covering 57 pages, were begun on June i6th and finished on 

 July 20th. 



The work was more than once interrupted by ill health, 

 and in September, what proved to be the beginning of a six 

 month's illness, forced him to leave home for the water-cure 

 at Malvern. He returned in October and remained ill and 

 depressed, in spite of the hopeful opinion of one of the most 

 cheery and skilful physicians of the day. Thus he wrote to 

 Sir J. D. Hooker in November : — 



"Dr. Brinton has been here (recommended by Busk) ; he 

 does not believe my brain or heart are primarily affected, but 

 I have been so steadily going down hill, I cannot help doubt- 

 ing whether I can ever crawl a little uphill again. Unless I 

 can, enough to work a little, I hope my life may be very 



