Ix THE DEBT OF SCIENCE TO DARWIN 457 
sented by this latter group of islands brought out so clearly 
and strongly the insuperable difficulties of the then accepted 
theory of the independent origin of species, as to keep this 
great problem ever present to his mind, and, at a later period, 
led him to devote himself to the patient and laborious in- 
quiries which were the foundation of his immortal work. He 
again and again remarks on the singular facts’ presented 
by these islands. Why, he asks, were the aboriginal in- 
habitants of the Galapagos created on American types of 
organisation, though the two countries differ totally in geolo- 
gical character and physical conditions? Why are so many 
of the species peculiar to the separate islands? He “is 
astonished at the amount of creative force, if such an expres- 
sion may be used, displayed in these small, barren, and rocky 
islands ; and still more so at its diverse, yet analogous action 
on points so near each other.” 
The variations which occur in species, as well as the modi- 
fications of the same organ in allied species, subjects which 
had been much neglected by ordinary naturalists, were con- 
stantly noted and commented on. He remarks on the 
occasional blindness of the burrowing tucutucu of the Pampas 
as supporting the view of Lamarck on the gradually acquired 
blindness of the aspalax; on the hard point of the tail of 
trigonocephalus, which constantly vibrates and produces a 
rattling noise by striking against grass and brushwood, as a 
character varying towards the complete rattle of the rattle- 
snake; on the small size of the wild horses in the Falkland 
islands, as progressing towards a small breed like the Shetland 
ponies of the North; and on the strange fact of the cattle 
having increased in size, and having partly separated into two 
differently coloured breeds. While collecting the remains of 
the great extinct mammals of the Pampas, he was much im- 
pressed by the fact that, however huge in size or strange in 
form, they were all allied to living South American . animals, 
as are those of the cave-deposits of Australia to the marsupials 
of that country; and he thereon remarks: “This wonderful 
relationship in the same continent between the dead and the 
living will, I do not doubt, hereafter throw more light on the 
appearance of organic beings on our earth, and their disap- 
pearance from it, than any other class of facts.” 
