EVOLUTION BY NATURAL SELECTION : DARWIN S CONCEPTION 



to work upon. Lyell had attacked geological problems by accumulating 

 all applicable data in the absence of a working theory, in the hope that 

 the sheer weight of facts might throw some light upon his problems. As 

 Darwin greatly admired the geological work of Lyell, he determined to 

 apply the same method to the species problem. Accordingly, he began in 

 July, 1837, his first notebook on variation in plants and animals, both 

 under domestication and in nature. No possible source of information was 

 overlooked: personal observations and experiments, published papers of 

 other biologists, conversations with breeders and gardeners, correspond- 

 ence with biologists at home and abroad, all are represented. As a result 

 of this, Darwin soon saw that man's success in producing useful varieties 

 of plants and animals depended upon selection of desired variations for 

 breeding stock. But he did not see how selection could be applicable to 

 nature. 



In October, 1838, Darwin happened to read for pleasure "Malthus on 

 Population," and it struck him at once that the struggle for existence 

 among plants and animals offered a basis for natural selection of those 

 variants which were best fitted to compete. But it was only in 1842, four 

 years later and after the collection of a great deal more data, that he wrote 

 out the first outline of his theory, a pencil draft of thirty-five pages. In 

 1844, this outline was enlarged to 230 pages. From the time of the com- 

 pletion of the Cirripede work in 1854, Darwin devoted all of his time to 

 the study and organization of his notes, and to further experiments on 

 transmutation of species. 



Early in 1856, Lyell advised Darwin to write out a full account of his 

 ideas on the origin of species, and he began this work on a much kuger 

 scale than that which finally appeared in the "Origin of Species." Then 

 early in the summer of 1858, when this work was perhaps half completed, 

 Alfred Russel Wallace, a young and little-known English naturalist then 

 working at Ternate in the Dutch East Indies, sent Darwin a short essay 

 "On the Tendency of Varieties to Depart Indefinitely from the Original 

 Type." Wallace asked Darwin, if he should think well of this essay, to 

 send it to Lyell for his criticism. Darwin thought very well of it, for he 

 recognized his own theory, and he felt that he ought to withhold his own 

 publication in favor of Wallace. However, Lyell and Hooker had for years 

 been familiar with Darwin's work on the transmutation of species, and, 

 Lyell had read Darwin's outline of 1842. These men therefore suggested 

 that Darwin write a short abstract of his theory, and that it be published 

 jointly with Wallace's paper in the Journal of the Proceedings of the Lin- 

 nean Society. These papers appeared in that journal in 1859, together with 

 portions of a letter which J3arwin had written to Asa Gray, the great 

 American botanist, in September, 1857, in which he set forth his views on 

 natural selection and the origin of species. 



Following this, Lyell and Hooker urged Darwin to prepare for early 

 publication a book on transmutation of species. Accordingly, he con- 

 densed the manuscript which he had begun in 1856 to about one third or 

 even one fourth its original size, and then completed the work on the 

 same reduced scale. The "Origin of Species," thus produced, was finally 



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