Worms have played a more important part in the history of the world than humans would at first suppose.

I agree with Agassiz that dogs possess something very like conscience.

It is absurd to talk of one animal being higher than another...we consider those, where the intellectual faculties most developed as the highest. - A bee doubtless would [use] ... instincts as a criteria.

The more one thinks, the more one feels the hopeless immensity of man's ignorance.

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.

There is no fundamental difference between humans and the higher mammalsin their mental faculties

we are always slow in admitting any great change of which we do not see the intermediate steps