74 CHARLES DARWIN 



presentation of the evolutionary case : Darwin resisted 

 it, and he did wisely. 



We may, however, take it for granted, I doubt not, 

 that it was the appearance and success of Chambers's 

 invertebrate book which induced Darwin, in 1844 (the 

 year of its publication), to enlarge his short notes ' into 

 a sketch of the conclusions which then seemed to him 

 probable.' This sketch he showed to Dr. (now Sir 

 Joseph) Hooker, no doubt as a precaution to ensure his 

 own claim of priority against any future possible com- 

 petitor. And having thus eased his mind for the 

 moment, he continued to observe, to read, to devour 

 ' Transactions,' to collate instances, with indefatigable 

 persistence for fifteen years longer. If any man mentally 

 measures out fifteen years of his own life, and bethinks 

 him of how long a space it seems when thus deliberately 

 pictured, he will be able to realise a little more definitely 

 but only a little how profound was the patience, 

 the self-denial, the single-mindedness of Darwin's intense 

 search after the ultimate truths of natural science. 



What was the sketch that he thus committed to 

 paper in 1844, and submitted to the judgment of his 

 friend Hooker? It was the germ of the theory of 

 natural selection. According to that theory, organic 

 development is due to the survival of the fittest among 

 innumerable variations, good, bad, and indifferent, from 

 one or more parent stocks. Darwin's reading of Mal- 

 thus had suggested to him (apparently as early as the 

 date of publication of the ' Naturalist's Journal ') the 

 idea that every species of plant and animal must always 

 be producing a far greater number of seeds, eggs, germs, 

 or young offspring than could possibly be needed for 



