434 BIOLOGY AND ITS MAKERS 



between certain extinct forms and recent animals in South 

 America. He noticed in the Galapagos Islands a fauna similar 

 in general characteristics to that of the mainland, five or six 

 hundred miles distant, and yet totally different as to species. 

 Moreover, certain species were found to be confined to par- 

 ticular islands. These observations awakened in his mind, 

 a mind naturally given to inquiring into the causes of things, 

 questions that led to the formulation of his theory. It was 

 not, however, until 1837 that he commenced his first note- 

 book for containing his observations upon the transmutations 

 of animals. He started as a firm believer in the fixity of 

 species, and spent several years collecting and considering 

 data before he changed his views. 



At Down. On his return to England, after spending 

 some time in London, he purchased a country-place at Down 

 and, as his inheritance made it possible, he devoted himself 

 entirely to his researches. 



But, as is well known, he found in his illness a great 

 obstacle to steady work. He had been a vigorous youth and 

 young man, fond of outdoor sports, as fishing, shooting, 

 and the like. After returning from his long voyage, he was 

 affected by a form of constant illness, involving a giddiness 

 in the head, and "for nearly forty years he never knew one 

 day of the health of an ordinary man, and thus his life was 

 one long struggle against the weariness and strain of sick- 

 ness." Gould in his Biographical Clinics attributes his ill- 

 ness to eye- strain. 



" Under such conditions absolute regularity of routine was 

 essential, and the day's work was carefully planned out. At 

 his best, he had three periods of work: from 8.00 to 9.30; 

 from 10.30 to 12.15; and from 4.30 to 6.00, each period being 

 under two hours' duration." 



The patient thoroughness of his experimental work and of 

 his observation is shown by the fact that he did not publish 



