The above remarks are best illustrated by a quotation from Darwin, which, in my opinion, should always be given in any general account of the relations of ants and Aphides. “I removed,” says Darwin, “all the ants from a group of about a dozen Aphides on a dock plant, and prevented their attendance during several hours. After this interval I felt sure that the Aphides would want to excrete. I watched them for some time through a lens, but not one excreted. I then tickled and stroked them with a hair in the same manner, as well as I could, as the ants do with their antennæ; but not one excreted. Afterwards I allowed an ant to visit them, and it immediately seemed, by its eager way of running about, to be well aware what a rich flock it had discovered; it then began to play with its antennæ on the abdomen first of one Aphis and then of another; and each, as soon as it felt the antennæ, lifted up its abdomen and excreted a limpid drop of sweet juice, which was eagerly devoured by the ant. Even the quite young Aphides behaved in this manner, showing that the action was instinctive, and not the result of experience. It is certain, from the observations of Huber, that the Aphides show no dislike to the ants: if the latter be not present, they are at last compelled to eject their excretion. But, as the excretion is extremely viscid it is no doubt a convenience to the Aphides to have it removed; therefore, probably, they do not excrete solely for the good of the ants.”[45] If the reverse of this were the case, if the Aphides did excrete for the sole benefit of the ants, then, in Darwin’s own opinion, the case for natural selection would be broken down, and with this there would be some better ground of reason for those who would see in relations of this sort a set-off, as it were, against the never-ending bloodshed and rapine, accompanied with suffering in varied—often in an intense—degree, which is the very stuff out of which Nature has woven her mantle. But there can be no essential difference where the principle at work is precisely the same. So long as a creature does benefit itself, the way in which it does it, and the incidental effects of its doing so, are of no consequence; it is the motive power that the philosopher has to consider, and there is little comfort—if comfort be needed—in knowing that an animal, to do itself good, is doing good to some other, when one also knows that, governed by the same incentive, it would as cheerfully prey upon that other’s eye. As Hamlet says, in such a case “the readiness is all.”