INTRODUCTION xiii 



and bird: and we see how we may explain 

 the evolution of their swiftness in like man- 

 ner. The man in the street is thus a Dar- 

 winian without knowing it, and the world- 

 success of Darwin's theory is thus more 

 readily understood; the age had found its 

 man, the hour its voice. 



But what of outdoor nature? "The field 

 in summer, the study in winter' 1 is a good 

 rule, yet not a sufficient one; the evolution- 

 ist's studies should as far as possible include 

 both elements of observation and interpre- 

 tation day by day. Hence Darwin's is per- 

 haps the most exemplary of scientific lives, 

 incessantly rising from sight to insight, yet 

 this as constantly freshening sight anew. 

 From boyish truancies, through youthful 

 travels and maturing researches his observa- 

 tions and his speculations went on enriching 

 one another; and thus their interpretation 

 and theory have been an " open sesame' 1 to 

 new fields, new volumes of personal discovery, 

 new impulses to fresh workers. Naturalist 

 and thinker, teacher and pupil, will thus 

 long be inspired by the example of Darwin 

 as rambler, traveller and observer, yet also 

 as dreamer and interpreter. The study of 

 biology is thus by no means merely abstract, 

 nor mainly in the library; it ever arises from 

 and returns to living nature, and goes on 



