architecture, and that of the ant, with its mixed societies. Before inquiring whether it might not be possible to explain even such amazing instincts by habit and inherited tendency, it is important at the outset to remove an objection that might be supposed unanswerable. Those individuals that have these instincts in the hive or in the ant-hill are neuters—that is to say, they are neither male nor female, and must consequently die without posterity. How explain the way in which a habit acquired by a neuter can be transmitted, can grow into an instinct, in the neuters of following generations, which will not descend from that first one? Yet the difficulty is not so great as it seems, and Darwin points it out very well. Indeed, it is not the instincts of the neuters which concern him, but it is the special organic modifications that these present, in connection with their social duties—with some, labor, and with others, fighting; but the reasoning he employs can be applied as well to instincts, behind which there always appears, as we see by a little reflection, that latent modification of the cerebral organ through which the transmission has taken place.
Darwin begins with a reminder that the principle of natural selection is true as well for communities as for individuals. The strength of a single male in a wild herd, the extraordinary fecundity of a single female, will be the elements of prosperity. The herd will succeed better than the rest. The qualities of the individual from which it draws its advantage will have a chance of being transmitted at first to all the herd, and this, more and more favored in the struggle against the outer world, will absorb the rest. The modification, at first individual, will become general. It would be the same if the member of the herd benefited in the beginning had been a neuter. We are still speaking of external forms. Let us suppose that a certain number of neuters may have brought from birth a favorable organic modification into a community of insects, and that by this the community has prospered; the males and females who have produced these neuters will then have, by them, the greatest possible chances of posterity. It may happen thenceforward that they transmit to their descendants what they had themselves—that is to say, the property of procreating neuters having the same favorable organic modification—and we thus fall back into the common process of natural selection. Such is Darwin's explanation; he is well aware, when he gives it, complex as it is, that it is the touchstone of his theory, the side whence attack will come; therefore, how he strengthens his arguments! He is no longer satisfied with explaining, he demonstrates; he is supposed to have exhausted his reasons, and this is the very moment he chooses for an appeal to experiment, and to the proof of that kind of paradox that might be called "hereditary tendency in sterility." There are oxen with horns a little longer than those of the bulls and heifers that produced them. "Well," says Darwin, "pair together, by attentive selection, the fertile descendants of the bulls and heifers that produced the oxen with longer
