The best naturalists, from Moses to Agassiz, have regarded the order of nature as the development of the divine idea, have prosecuted their researches on that view, and have regarded that as a sufficient and scientific explanation of the gradation of plants and animals, as they actually exist.
The idea of birth descent can not be logically connected with that of gradation; especially with a gradation upward.

Were the order of nature such as Lamarck describes, how could any man logically infer the birth descent of each of its classes from the next below?
Here is an ironmonger's sample card of wood screws, beginning with those one-quarter of an inch long, and proceeding by gradations of one-sixteenth of an inch to those of four inches.

Does the gradation show that the little ones begot the big ones?
It may be said the wood screws do not beget progeny.

Well, here is a hill containing twenty-three potatoes, weighing from half an ounce to half a pound, and quite regularly graded.

Did the small potatoes beget the big ones?
The inference of birth descent from gradation is utterly illogical, and of a piece with the incoherency which we have seen in the other parts of the theory.