"... the structure of every organic being is related, in the most essential yet often hidden manner, to that of all the other organic beings ..."

"None can reply - all seems eternal now. The wilderness has a mysterious tongue, which teaches awful doubt."

"In the future I see open fields for more important researches. Psychology will be securely based on the foundation already laid by Mr. Herbert Spencer, that of the necessary acquirement of each mental power and capacity by graduation."

"We cannot fathom the marvelous complexity of an organic being; but on the hypothesis here advanced this complexity is much increased. Each living creature must be looked at as a microcosm--a little universe, formed of a host of self-propagating organisms, inconceivably minute and as numerous as the stars in heaven."