For it by no means follows that if some examples of new species have recently been suddenly produced from individuals of antecedent species, we ought to be able to put our fingers on such cases; as Mr.
Murphy well observes[230] in a passage before quoted, "If a species were to come suddenly into being in the wild state, as the Ancon sheep did under domestication, how could we ascertain the fact?
If the first of a newly-born species were found, the fact of its discovery would tell nothing about its origin.

Naturalists would register it as a very rare species, having been only once met with, but they would have no means of knowing whether it were the first or the last of its race." But are there any grounds for thinking that in the genesis of species an _internal_ force or tendency interferes, co-operates with and controls the action of external conditions?
It is here contended that there are such grounds, and that though inheritance, reversion, atavism, Natural Selection, &c., play a part not unimportant, yet that such an internal power is a great, perhaps the main, determining agent.
It will, however, be replied that such an entity is no _vera causa_; that if the conception is accepted, it is no real explanation; and that it is merely a roundabout way of saying that the facts are as they are, while the cause remains unknown.

To this it may be rejoined that for all who believe in the existence of the abstraction "force" at all, other than will, {228} this conception of an internal force must be accepted and located somewhere--cannot be eliminated altogether; and that therefore it may as reasonably be accepted in this mode as in any other.
It was urged at the end of the third chapter that it is congruous to credit mineral species with an internal power or force.

By such a power it may be conceived that crystals not only assume their external symmetry, but even repair it when injured.

Ultimate chemical elements must also be conceived as possessing an innate tendency to form certain unions, and to cohere in stable aggregations.