In the Life of Darwin by his ...

In the Life of Darwin by his son, there is related an incident of how the great naturalist once studied long as to just what a certain spore was. Finally he said, \

In the Life of Darwin by his son, there is related an incident of how the great naturalist once studied long as to just what a certain spore was. Finally he said, "It is this, for if it isn't, then what is it?" And all during his life he was never able to forget that he had been guilty of this unscientific attitude, for science is founded on certitude, not assumption.

Quotes from the same author

Friendship, like credit, is highest when it is not used.

Never explain - your friends do not need it and your enemies will not believe you anyway.

A little more persistence, a little more effort, and what seemed hopeless failure may turn to glorious success.

There is no failure except in no longer trying.

A failure is a man who has blundered but is not capable of cashing in on the experience.