Extinction has only separated groups: it has by no means made them; for if every form which has ever lived on this earth were suddenly to reappear, though it would be quite impossible to give definitions by which each group could be distinguished from other groups, as all would blend together by steps as fine as those between the finest existing varieties, nevertheless a natural classification, or at least a natural arrangement, would be possible.

Among the scenes which are deeply impressed on my mind, none exceed in sublimity the primeval [tropical] forests, ... temples filled with the varied productions of the God of Nature. No one can stand in these solitudes unmoved, and not feel that there is more in man than the mere breath of his body.

... probably all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed.

Disbelief crept over me at a very slow rate, but at last it was complete.

Every new body of discovery is mathematical in form, because there is no other guidance we can have.

It has been a bitter mortification for me to digest the conclusion that the "race is for the strong" and that I shall probably do little more but be content to admire the strides others made in science.

Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends.