One can descend by imperceptible degree from the most perfect creature to the most shapeless matter, from the best-organised animal to the roughest mineral.

I am convinced, by repeated observation, that marbles, lime-stones, chalks, marls, clays, sand, and almost all terrestrial substances, wherever situated, are full of shells and other spoils of the ocean.

There is nothing good in love but the physical part.

Let us investigate more closely this property common to animal and plant, this power of producing its likeness, this chain of successive existences of individuals, which constitutes the real existence of the species.

To write well is to think well, to feel well, and to render well; it is to possess at once intellect, soul, and taste.

The discoveries that one can make with the microscope amount to very little, for one sees with the mind's eye and without the microscope the real existence of all these little beings.

He [man] abuses equally other animals and his own species, the rest of whom live in famine, languish in misery, and work only to satisfy the immoderate appetite and the still more insatiable vanity of this human being who, destroying others by want, destroys himself by excess.