“The most ancient progenitors in the kingdom of the vertebrata,” observes the same great English naturalist in another place, “at which we are able to obtain an obscure glance, apparently consisted of a group of marine animals, resembling the larvæ of existing Ascidians. These animals probably gave rise to a group of fishes as lowly organized as the lancelet; and from these the Ganoids, and other fishes like the Lepidosiren, must have been developed. From such fish a very small advance would carry us on to the amphibians. We have seen that birds and reptiles were once intimately connected together; and the Monotremata now, in a slight degree, connect mammals with reptiles. But no one can at present say by what line of descent the three higher and related classes, namely, mammals, birds, and reptiles, were derived from either of the two lower vertebrate classes, namely, amphibians and fishes. In the class of mammals, the steps are not difficult to conceive which led from the ancient Monotremata to the ancient Marsupials; and from these to the early progenitors of the placental mammals. We may thus ascend to the Lemuridæ, and the interval is not wide from these to the Simiadæ. The Simiadæ then branched off into two great stems, the New World and Old World monkeys; and from the latter, at a remote period, Man, the wonder and glory of the universe, proceeded.”[137] Setting aside for the present this long pedigree of man, let us consider some of the isolated phases which have been established in the still incomplete condition of modern science. As far as semi-apes are concerned, whose near relation to men and apes has of late been strongly urged, I agree with those who, like Vogt, consider that their order, with its variety of forms, points to a complex origin, probably from marsupial animals, with which their organization presents many common features; hence it appears that some of their forms belong to the earliest Tertiary mammals with which we are well acquainted. “In conclusion,” he writes, “it appears, from these facts, that any very close connection between the semi-apes and apes, and hence with man, cannot be proved. With the exception of the opposing thumb, which is and was a widely diffused characteristic common to many species, the semi-apes have not a single anatomical feature in common with apes. Their jaw, the most permanent characteristic, places them in the insectivorous class; to enroll them among the ancestors of man is to set at nought all the principles of scientific research.”[138]