PEEFACE 



I:N" preparing this volume, which is practically an abbre- 

 viation of the Life and Letters (1887), my aim has been to 

 retain as far as possible the personal parts of those volumes. 

 To render this feasible, large numbers of the more purely 

 scientific letters are omitted, or represented by the citation 

 of a few sentences.* In certain periods of my father's life 

 the scientific and the personal elements run a parallel 

 course, rising and falling together in their degree of inter- 

 est. Thus the writing of the Origin of Species, and its 

 publication, appeal equally to the reader who follows my 

 father's career from interest in the man, and to the natural- 

 ist who desires to know something of this turning point in 

 the history of Biology. This part of the story has there- 

 fore been told with nearly the full amount of available 

 detail. 



In arranging my material I have followed a roughly 

 chronological sequence, but the character and variety of my 

 father's researches make a strictly chronological order an 

 impossibility. It was his habit to work more or less simul- 

 taneously at several subjects. Experimental work was often 

 carried on as a refreshment or variety, while books entail- 

 ing reasoning and the marshalling of large bodies of facts 

 were being written. Moreover many of his researches were 

 dropped only to be resumed after years had elapsed. Thus 



* I have not thought it necessary to indicate all the omissions in the ab- 

 breviated letters. 



(v) 



