As to the sterility of hybrids, that can no longer be insisted upon as absolutely true, nor be practically used as a test between species and varieties, unless we allow that hares and rabbits are of one species.  That it subserves a purpose in keeping species apart, and was so designed, we do not doubt.  But the critics fail to perceive that this sterility proves nothing against the derivative origin of the actual species; for it may as well have been intended to keep separate those forms which have reached a certain amount of divergence as those which were always thus distinct.

The argument for the permanence of species, drawn from the identity with those now living of cats, birds, and other animals, preserved in Egyptian catacombs, was good enough as used by Cuvier against St. Hilaire, that is, against the supposition that time brings about a gradual alteration of whole species; but it goes for little against Darwin, unless it be proved that species never vary, or that the perpetuation of a variety necessitates the extinction of the parent breed.  For Darwin clearly maintains—­what the facts warrant—­that the mass of a species remains fixed so long as it exists at all, though it may set off a variety now and then.  The variety may finally supersede the parent form, but it may coexist with it; yet it does not in the least hinder the unvaried stock from continuing true to the breed, unless it crosses with it.  The common law of inheritance may be expected to keep both the original and the variety mainly true as long as they last, and none the less so because they have given rise to occasional varieties.  The tailless Manx cats, like the fox in the fable, have not induced the normal breeds to dispense with their tails, nor have the Dorkings (apparently known to Pliny) affected the permanence of the common sort of fowl.

As to the objection, that the lower forms of life ought, on Darwin’s theory, to have been long ago improved out of existence, replaced by higher forms, the objectors forget what a vacuum that would leave below, and what a vast field there is to which a simple organization is best adapted, and where an advance would be no improvement, but the contrary.  To accumulate the greatest amount of being upon a given space, and to provide as much enjoyment of life as can be under the conditions, seems to be aimed at, and this is effected by diversification.

Finally, we advise nobody to accept Darwin’s, or any other derivative theory, as true.  The time has not come for that, and perhaps never will.  We also advise against a similar credulity on the other side, in a blind faith that species—­that the manifold sorts and forms of existing animals and vegetables—­“have no secondary cause.”  The contrary is already not unlikely, and we suppose will hereafter become more and more probable.  But we are confident, that, if a derivative hypothesis ever is established, it will be so on a solid theistic ground.