[190] “Alia vero semen adhuc imperfectum et immaturatum recludunt, incrementum et perfectionem, sive maturitatem, soris acquisiturum; ut plurima genera piscium, ranæ, item mollia, crustata, testacea, et cochleæ: quorum ova primum exposita sunt, veluti origines duntaxat, inceptiones et vitelli; qui postea albumina sibi ipsis circum circa induunt; tandemque alimentum sibi attrahentes, concoquentes et apponentes, in perfectum semen atque ovum evadunt. Talia sunt insectorum semina (vermes ab Aristotele dicta) quæ initio imperfecte edita sibi victum quærunt indeque nutriuntur et augentur, de eruca in aureliam; de ovo imperfecto in perfectum ovum et semen.”--_De generatione_, Exc. II., p. 183 (1666). Viallanes justifies this view by applying it to the histolysis and regeneration of the tissues in Diptera. But these remarkable changes are surely secondary, adaptive, and peculiar, like the footless maggot itself, whose conversion into a swift-flying imago renders necessary so complete a reconstruction. [191] The reader is recommended to refer to Fritz Müller’s Facts and Arguments for Darwin, especially chap. xi.; to Balfour’s Embryology, Vol. II., chap. xiii., sect. ii.; and to Lubbock’s Origin and Metamorphoses of Insects. _The Genealogy of Insects._ To construct from embryological and other data a chart of the descent of Insects, and of the different orders within the class, is an attempt too hazardous for a student’s text-book.[192] A review of the facts of Arthropod development led Balfour[193] to conclude that the whole of the Arthropoda cannot be united in a common phylum. The Tracheata are probably “descended from a terrestrial Annelidan type related to _Peripatus_.... The Crustacea, on the other hand, are clearly descended from a Phyllopod-like ancestor, which can be in no way related to _Peripatus_.” The resemblances between the Arthropoda appear therefore to be traceable to no nearer common ancestors than some unknown Annelid, probably marine, and furnished with a chitinous cuticle, an œsophageal nervous ring, and perhaps with jointed appendages. Zoological convenience must give place to the results of embryological and historical research, and we shall probably have to reassign the classes hitherto grouped under the easily defined sub-kingdom of Arthropoda. [192] Those who care to see a bold experiment of this kind may refer to Haeckel’s Schöpfungsgeschichte. [193] Comp. Embryology, Vol. I., p. 451. Sir John Lubbock has explained, in his very interesting treatise on the Origin and Metamorphoses of Insects, the reasons which lead him to conclude “that Insects generally are descended from ancestors resembling the existing genus _Campodea_ [sub-order Collembola], and that these again have arisen from others belonging to a type represented more or less closely by the existing genus _Lindia_” [a non-ciliated Rotifer].