Publisher's Synopsis
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1882 edition. Excerpt: ... genus Sphinx. In some specimens of Smerinthus Tilice the spots coalesce so as to form an irregular coloured edge to the oblique stripes. In 5." Populi they occur in many individuals, but remain always in the spot stage; whilst S. Ocellatus is but seldom, and 5." Quercus appears never to be spotted. The spots both of vS." Tilice and Populi certainly do not show themselves exclusively in the fifth (last) stage, but also in the fourth, and sometimes in Populi even as early as the third stage, from which we might be disposed to conclude that the new character did not first appear in the last stage. But the majority of the spotted individuals first acquire their spots in the fifth stage, and only a minority in the fourth; so that their occasional earlier appearance must be ascribed to the backward transference of a character acquired in the fifth stage. Moreover, the fourth and fifth stages of the caterpillars are closely analogous both in size, mode of life, and marking, and are therefore analogous with reference to the environment, so that it is to be expected that new characters, when depending on adaptation, would be rapidly transferred from the fifth stage to the fourth.3 We should "If the reddish-brown spots on the larva of 5. Populi have the protective function assigned to them by Mr. Peter Cameron (Trans. Ent. Soc. 1880, p. 69), it can be readily understood that they would be of service to the insect in the fourth stage, and the backward transference of this character might thus be accelerated by natural selection, in accordance with the above principles. (See, also, note," p. 241.) R.M. thus have a case of the acceleration by natural selection, of processes determined by innate causes. Why changes should predominate in the last...
