All aquatic insects are evidently the descendants of terrestrial forms, and the numberless contrivances and temporary larval organs, particularly of dipterous larvæ, are evidently adaptations to the needs of the insect during its aquatic life, and which are cast aside when the creature passes to a different medium. The sudden or tachygenic appearance of temporary structures, such as hatching spines, various setæ, spines, respiratory organs, so characteristic of dipterous larvæ, and of the protective colors and markings of caterpillars, and which are discarded at pupation, or imagination, are evidently due to the action of stimuli from without, to the primary neolamarckian factors, the characters proper to each larval stadium, and to the pupal and imaginal stadia,—characters probably acquired during the lifetime of the individual,—becoming finally fixed by homochronous heredity.

LITERATURE ON POSTEMBRYONIC DEVELOPMENT AND METAMORPHOSES

Herold, Moritz Johann David. Entwicklungsgeschichte der Schmetterlinge anatomisch und physiologisch bearbeitet. (Cassel, u. Marburg, 1815. 33 Taf., 4º, pp. 1–118, i-xxxiv.)

Ratzeburg, F. T. C. Ueber Entwickelung des fusslosen Hymenopteren-larven, mit besonderer Rücksigt auf die Gattung Formica. (Nova Acta Natur. Curios., xvi, 1832, pp. 145–176.)

Agassiz, Louis. The classification of insects from embryological data. (Smithsonian Contr., ii, Washington, 1851, pp. 28, 1 Pl.)

Ganin, M. Beiträge zur Erkenntniss der Entwicklungsgeschichte bei den Insecten. (Zeitschr. f. wiss. Zool., xix, 1869, pp. 381–451, 4 Taf.)

—— Ueber die Embryonalhülle der Hymenopteren- und Lepidopteren-embryonen. (Mém. Acad. St. Petersbourg (7), xiv, 1869, pp. 18, 1 Pl.)

—— Materialien zur Kenntniss der post-embryonalen Entwicklungsgeschichte der Insecten. (Russian.) Warschau, 1876. (Abdruck aus den Arbeiten der V. Versammlung russischer Naturf. und Aerzte in Warschau, 1876. Abstract by Hoyer in Jahresber. der Anat. und Phys. von Hoffmann und Schwalbe, v, 1876, and in Zeitschr. f. wiss. Zool., xxviii, 1877, pp. 386–389.)

Weismann, A. Die nachembryonale Entwicklung der Musciden nach Beobachtungen an Musca vomitoria und Sarcophaga carnaria. (Zeitschr. f. wiss. Zool., xiv, 1864, pp. 101–263, Taf. 8–14.)

—— Die Metamorphose von Corethra plumicornis. (Zeitschr. f. wiss. Zool., xvi, 1866, pp. 1–83, 5 Taf.)