Another point of interest in these degraded insects is, that the process of degradation begins either late in the life of the embryo or during the changes from the larval to the adult, or winged state. An instance of the latter may be observed in the wingless female of the canker worm, so different from the winged male; this difference is created after the larval stage, for the caterpillars of both sexes are the same, so far as we know. So with numerous other examples among the moths. In the louse, the embryo, late in its life, resembles the embryos of other insects, even Corixa, a member of a not remotely allied family. But just before hatching the insect assumes its degraded louse physiognomy. The developmentist would say that this process of degradation points to causes acting upon the insect just before or immediately after birth, inducing the retrogression and retardation of development, and would consider it as an argument for the evolution of specific forms by causes acting on the animal while battling with its fellows in the struggle for existence, and perhaps consider that the metamorphoses of the animal within the egg are due to a reflex action of the modes of life of the ancestors of the animal on the embryos of its descendants. [Illustration: 125. The Turkey Louse.] FOOTNOTES: [Footnote 5: Ha! whare ye gaun, ye crowlin ferlie! Your impudence protects you sairly: I canna say but ye struift rarely, Owre gauze and lace; Tho' faith, I fear ye dine but sparely On sic a place. Ye ugly, creepin, blastic wormer, Detested, shunn'd by saunt and sinner, How dare ye set your fit upon her Sae fine a lady! Gae somewhere else and seek your dinner On some poor body. (To a Louse.--Burns.)] [Footnote 6: We notice while preparing this article that a journal of Parasitology has for some time been issued in Germany--that favored land of specialists. It is the "Zeitschrift fur Parasitenkunde," edited by Dr. E. Hallier and F A. Zurn. 8vo, Jena.] [Footnote 7: Figure 111 represents the parts of the mouth in a large specimen of _Pediculus_ vestimenti, entirely protruding, and seen from above, magnified one hundred and sixty times; aa, the summit of the head with four bristles on each side; _bb_, the chitinous band, and _c_, the hind part of the lower lip, such as they appear through the skin by strong transmitted light; _dd_, the foremost protruding part of the lower lip (the haustellum); _ee_, the hooks turned outwards; _f_, the inner tube of suction, slightly bent and twisted; the two pairs of jaws are perceived on the outside as thin lines; a few blood globules are seen in the interior of the tube.] CHAPTER X. THE DRAGON FLY.