DARWIN'S METHOD OF STUDY. 135 
of natural selection flashed on me. Of all the minor points, 
the last which I appreciated was the importance and cause 
of the principle of divergence.” 
During the leisure and retirement in which Darwin lived 
after his return, he occupied himself, as we see from this 
letter, first and specially with the study of organisms in 
their cultivated state ; that is, domestic animals and garden 
plants. This was undoubtedly the most likely way to 
arrive at the Theory of Selection. In this, as in all his 
labours, Darwin proceeded with extreme care and accuracy. 
With wonderful caution and self-denial, he published nothing 
on this subject during a period of twenty-one years, from 1837 
to 1858, not even a preliminary sketch of his theory, which 
he had written as early as 1844. He was always anxious to 
collect still more certain experimental proofs, in order to be 
able to establish his theory in a complete form, and on the 
broadest possible foundation of experience. While he was 
thus aiming at the greatest possible perfection, which might 
perhaps have led him never to publish his theory at all, he 
was fortunately disturbed by a countryman of his, who, 
independently of Darwin, had discovered the Theory of 
Selection, and in 1858 sent its outlines to Darwin himself, 
with the request to hand them to Lyell for publication in 
some English journal. This was Alfred Wallace, one of the 
boldest and most distinguished scientific travellers of modern 
times. For many years Wallace had wandered alone in the 
wilds of the Sunda Islands, in the dense primitive forests of 
the Indian Archipelago; and during this close and compre- 
hensive study of one of the richest and most interesting 
parts of the earth, with its great variety of animals and 
