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 whence two or more species have sprung, need in no respect be intermediate between these species.  If any two species have arisen from a common stock in the same way as the carrier and the pouter, say, have arisen from the rock-pigeon, then the common stock of these two species need be no more intermediate between the two than the rock-pigeon is between the carrier and pouter.  Clearly appreciate the force of this analogy, and all the arguments against the origin of species by selection, based on the absence of transitional forms, fall to the ground.  And Mr. Darwin’s position might, we think, have been even stronger than it is if he had not embarrassed himself with the aphorism, “Natura non facit saltum,” which turns up so often in his pages.  We believe, as we have said above, that Nature does make jumps now and then, and a recognition of the fact is of no small importance in disposing of many minor objections to the doctrine of transmutation.

But we must pause.  The discussion of Mr. Darwin’s arguments in detail would lead us far beyond the limits within which we proposed, at starting, to confine this article.  Our object has been attained if we have given an intelligible, however brief, account of the established facts connected with species, and of the relation of the explanation of those facts offered by Mr. Darwin to the theoretical views held by his predecessors and his contemporaries, and, above all, to the requirements of scientific logic.  We have ventured to point out that it does not, as