onnected 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. It never could be inferred from the facts stated, even did
nature correspond to Lamarck's description.

But nature does not correspond to Lamarck's description. That
description corresponded moderately, perhaps, to the science of his day,
which was based chiefly upon external resemblances; but no scientific
naturalist of the present day would accept it as a correct statement of
the facts revealed by modern science.

In the first place there is no such imperceptible blending and shading
off of species as the description would imply, obliterating all
distinctions of species, and rendering it impossible even for a
naturalist to distinguish one species from another. Since the time of
Lamarck, structure and physiology have been more studied than mere
external appearances; so that from a tooth or bone Cuvier or Agassiz
could reconstruct an animal, and indicate its internal organization, as
well as its form and habits. But even in Lamarck's days, and even to the
most uneducated, there was no such imperceptible shading and blending as
the theory requires. It is well to look here at its requirements, for
they are not fully presented by its friends. Mr. Darwin gives us a
diagram exhibiting the variation of an original species into a score or
so of varieties, ending in distinct species. But this is very far,
indeed, below the necessities of the case. The horse hair worm lays
8,000,000 of eggs; and the primeval germ, whatever it was, could hardly
be less fertile, since fertility increases with simplicity of structure.
But, taking 8,000,000 to begin with, here were as many varieties; since
no two of