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

"I am almost convinced (quite contrary to opinion I started with) that species are not (it is like confessing a murder) immutable."

"It is not the strongest of the species that survives, nor the most intelligent, but the one most responsive to change."

"The difference in mind between man and the higher animals, great as it is, certainly is one of degree and not of kind."

"The greatest discovery of all is that the world is not as we thought it was."