6 DARWINISM AND HUMAN LIFE 



were punctuated by the completion of book after 

 book the " milestones of my life," as he called 

 them ; and it may be useful to note that Darwin 

 recognised three stages in his career as a biologist : 

 (1) the mere collector at Cambridge ; (2) the 

 collector and observer on the Beagle voyage (to 

 which he thought he owed " the first real training 

 and education " of his mind) ; and (3) the trained 

 naturalist after his eight years' work on barnacles. 



His books may be arranged in three groups : 



(a) The early zoological and geological studies, 

 e.g. " Zoology and Geology of the Beagle " (1840- 

 46), " Coral Keefs " (1842), " Monograph on the 

 Cirripedia" (1846-54). Although the book on 

 Earthworms was not published till 1881, it was 

 begun more than forty years before, and may be 

 included in the first series. 



(6) The series of evolutionary volumes : " The 

 Origin of Species" (1859); "Variation of Ani- 

 mals and Plants under Domestication " (1868) ; 

 " Descent of Man " (1871) ; " Expression of the 

 Emotions " (1872). 



(c) The botanical books largely influenced by 

 evolutionary ideas : " Fertilisation of Orchids " 

 (1862) ; " Movements and Habits of Climbing 

 Plants " (1875) ; " Insectivorous Plants " (1875) ; 

 " Cross and Self-fertilisation in Plants " (1876) ; 

 " The Different Forms of Flowers in Plants of the 

 same Species " (1877) ; " The Power of Movement 

 in Plants " (1880). 



THE NATURALIST'S PROBLEMS. It may be useful 

 to inquire into the aims and methods of naturalists 

 in general, if we are rightly to appreciate the 

 services rendered by the greatest of them all. The 

 problems appear at first sight to be numerous and 



