course of time become so perfectly
distinct, that when looked at in their extremest development they appear
to have little or nothing in common.

"The effect of the body upon the mind has been already sufficiently
recognized; not so that of the mind upon the body itself. The two, one
in the outset though they were, interact upon each other more and more
the more they present the appearance of having become widely sundered,
and it can be shown that each is continually modifying the other and
causing it to vary."[335]

And again, later:--

"I shall show that the habits by which we now recognize any creature
are due to the environment (_circonstances_) under which it has for a
long while existed, _and that these habits have had such an influence
upon the structure of each individual of the species as to have at
length_" (that is to say, through many successive slight variations,
each due to habit engendered by the wishes of the animal itself),
"modified this structure and adapted it to the habits contracted."[336]

These quotations must suffice, for the reader has already had Lamarck's
argument sufficiently put before him.

Variation, and consequently modification, are, according to Lamarck, the
outward and visible signs of the impressions made upon animals and
plants in the course of their long and varied history, each organ
chronicling a time during which such and such thoughts and actions
dominated the creature, and specific changes being the effect of certain
long-continued wishes upon the body, and of certain changed surroundings
upon the wishes. Plants and animals are living forms of faith, or faiths
of form, whichever the reader pleases.

Mr. Darwin, on the other hand, repeatedly avows ignorance, and profound
ignorance, concerning the causes of those variations which, or nothing,
must be the fountain-heads of species. Thus he writes of "the complex
and _little known_ laws of variation."[337] "There is also _some
probability_ in the view propounded by Andrew Knight, that variability
_may be partly_ connected with excess of food."[338] "Many laws regulate
variation, _some few of which_ can be _dimly seen_."[339] "The results
of the _unknown_, or _but dimly understood_, laws of variation are
infinitely complex and diversified."[340] "We are _profoundly ignorant_
of the cause of each slight variation or individual difference."[341]
"We are _far too ignorant_ to speculate on the relative importance of
the several