"The love of experiment and the patient observation of nature are the two great qualifications for a naturalist."

"Man has risen to the very summit of the organic scale; and the fact of his having thus risen, instead of having been aboriginally placed there, is the best proof of his power of development."

"I have steadily endeavoured to keep my mind free so as to give up any hypothesis, however much beloved, as soon as facts are shown to be opposed to it."

"I am almost convinced that species are not (it is like confessing a murder) immutable."

"The greatest error of all is to stop at the first result."