Perhaps no order of mammals presents us with so extraordinary a series of gradations as this [step by step, from humans to apes to monkeys to lemurs] - leading us insensibly from the crown and summit of the animal creation down to creatures, from which there is but a step, as it seems, to the lowest, smallest, and least intelligent of the placental Mammalia. It is as if nature herself had forseen the arrogance of man, and with Roman severity had provided that his intellect, by its very triumphs, should call into prominence the slaves, admonishing the conqueror that he is but dust.

It is the first duty of a hypothesis to be intelligible.

There is but one right, and the possibilities of wrong are infinite.

Whatever evil voices may rage, Science, secure among the powers that are eternal, will do her work and be blessed.

Of the few innocent pleasures left to men past middle life, the jamming of common sense down the throats of fools is perhaps the keenest.

The student of Nature wonders the more and is astonished the less, the more conversant he becomes with her operations; but of all the perennial miracles she offers to his inspection, perhaps the most worthy of admiration is the development of a plant or of an animal from its embryo.

It is wrong for a man to say that he is certain of the objective truth of any proposition unless he can produce evidence which logically justifies that certainty.