"I am not apt to follow blindly the lead of other men."

"If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down."

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

"Looking to the world at no very distant date, what an endless number of the lower races will have been eliminated by the higher civilized races throughout the world."

"A scientific man ought to have no wishes, no affections – a mere heart of stone."