426 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 Downs.—On his return to England, after spending 
some time in London, he purchased a country-place at Downs, 
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 
