These changes are only made slowly and imperceptibly.

Nature's great workman is time.

He marches ever with an even pace and does nothing by leaps and bounds, but by degrees, gradations, and succession he does all things; and the changes which he works--at first imperceptible--become little by little perceptible, and show themselves eventually in results about which there can be no mistake.

Nevertheless, animals in a free, wild state are perhaps less subject than any other living beings, man not excepted, to alterations, changes, and variations of all kinds.
Being free to choose their own food and climate, they vary less than domestic animals vary."[134] The Buffonian factor of the direct influence of climate is not in general of so thoroughgoing a character as usually supposed by the commentators of Buffon.

He generally applies it to the superficial changes, such as the increase or decrease in the amount of hair, or similar modifications not usually regarded as specific characters.