ertile breeds
from a common stock, in a comparatively few years; but still, as the
case stands at present, this "little rift within the lute" is not to be
disguised nor overlooked.

In the remainder of Mr. Darwin's argument our own private ingenuity has
not hitherto enabled us to pick holes of any great importance; and
judging by what we hear and read, other adventurers in the same field do
not seem to have been much more fortunate. It has been urged, for
instance, that in his chapters on the struggle for existence and on
natural selection, Mr. Darwin does not so much prove that natural
selection does occur, as that it must occur; but, in fact, no other sort
of demonstration is attainable. A race does not attract our attention in
Nature until it has, in all probability, existed for a considerable
time, and then it is too late to inquire into the conditions of its
origin. Again, it is said that there is no real analogy between the
selection which takes place under domestication, by human influence, and
any operation which can be effected by Nature, for man interferes
intelligently. Reduced to its elements, this argument implies that an
effect produced with trouble by an intelligent agent must, _a fortiori_,
be more troublesome, if not impossible, to an unintelligent agent. Even
putting aside the question whether Nature, acting as she does according
to definite and invariable laws, can be rightly called an unintelligent
agent, such a position as this is wholly untenable. Mix salt and sand,
and it shall puzzle the wisest of men, with his mere natural appliances,
to separate all the grains of sand from all the grains of salt; but a
shower of rain will effect the same object in ten minutes. And so, while
man may find it tax all his intelligence to separate any variety which
arises, and to breed selectively from it, the destructive agencies
incessantly at work in Nature, if they find one variety to be more
soluble in circumstances than the other, will inevitably, in the long
run, eliminate it.

A frequent and a just objection to the Lamarckian hypothesis of the
transmutation of species is based upon the absence of transitional forms
between many species. But against the Darwinian hypothesis this argument
has no force. Indeed, one of the most valuable and suggestive parts of
Mr. Darwin's work is that in which he proves, that the frequent absence
of transitions is a necessary consequence of his doctrine, and that the
stock wh