Then follows an attempt to reconstruct, from the atavistic characters, a picture of our primitive ancestor who was undoubtedly an arboreal animal. The occurrence of rudiments of parts in one sex which only come to full development in the other is next discussed. This state of things Darwin regards as derived from an original hermaphroditism. In regard to the mammary glands of the male he does not accept the theory that they are vestigial, but considers them rather as not fully developed.英文原著 · 《Darwin and Modern Science》
South creep under dim arboreal archways hung with banners of waving英文原著 · 《Little Rivers》
He wondered if this creature was representative of some strange race or if, what seemed more likely, but an atavism. Either supposition would have seemed preposterous enough did he not have before him the evidence of the creature's existence. There he was, however, a tailed man with distinctly arboreal hands and feet. His trappings, gold encrusted and jewel studded, could have been wrought only by skilled artisans; but whether they were the work of this individual or of others like him, or of an entirely different race, Tarzan could not, of course, determine.英文原著 · 《Tarzan the Terrible》
Pan-at-lee, descended from a long line of hunters, assumed that Tarzan would move up wind and in this direction she sought his tracks, which she soon found well marked, since he had made no effort to conceal them. She moved rapidly until she reached the point at which Tarzan had taken to the trees. Of course she knew what had happened; since her own people were semi-arboreal; but she could not track him through the trees, having no such well-developed sense of scent as he.英文原著 · 《Tarzan the Terrible》
Moreover, these active creatures have the same functions as Coleoptera, and thus render their existence unnecessary. The large proportion of climbing forms of carnivorous beetles is an interesting fact, because it affords another instance of the arboreal character which animal forms tend to assume in equinoctial America, a circumstance which points to the slow adaptation of the fauna to a forest-clad country throughout an immense lapse of geological time.英文原著 · 《The Naturalist on the River Amazons》