gle for existence by having long studied
the habits of animals.

Before visiting the Galapagos I had collected many animals whilst
travelling from north to south on both sides of America, and everywhere,
under conditions of life as different as it is possible to conceive,
American forms were met with--species replacing species of the same
peculiar genera. Thus it was when the Cordilleras were ascended, or the
thick tropical forests penetrated, or the fresh waters of America searched.
Subsequently I visited other countries, which in all the conditions of life
were incomparably more like to parts of South America, than the different
parts of that continent were to each other; yet in these countries, as in
Australia or Southern Africa, the traveller cannot fail to be struck with
the entire difference of their productions. Again the reflection was forced
on me that community of descent from the early inhabitants or colonists of
South America would alone explain the wide prevalence of American types of
structure throughout that immense area.

To exhume with one's own hands the bones of extinct and {11} gigantic
quadrupeds brings the whole question of the succession of species vividly
before one's mind; and I had found in South America great pieces of
tesselated armour exactly like, but on a magnificent scale, that covering
the pigmy armadillo; I had found great teeth like those of the living
sloth, and bones like those of the cavy. An analogous succession of allied
forms had been previously observed in Australia. Here then we see the
prevalence, as if by descent, in time as in space, of the same types in the
same areas; and in neither case does the similarity of the conditions by
any means seem sufficient to account for the similarity of the forms of
life. It is notorious that the fossil remains of closely consecutive
formations are closely allied in structure, and we can at once understand
the fact if they are likewise closely allied by descent. The succession of
the many distinct species of the same genus throughout the long series of
geological formations seems to have been unbroken or continuous. New
species come in gradually one by one. Ancient and extinct forms of life
often show combined or intermediate characters, like the words of a dead
language with respect to its several offshoots or living tongues. All these
and other such facts seemed to me to point to descent with modification as
the method of production of ne