[234] Proc. Acad. Philadelph. xix. 1867, pp. 166-209. [235] Mém. Acad. Petersb. vol. xvi. [236] [Eng. ed. Seidlitz is an exception, since in his work on Parthenogenesis (Leipzig, 1872, p. 13) he states that “In the Axolotl, Pædogenesis, which is not in this case ... monogamous, but sexual, and indeed gynækogenetic, has already become so far constant that it has perhaps entirely superseded the orthogenetic reproduction.”] [237] Über den Einfluss der Isolirung auf die Artbildung. Leipzig, 1872, p. 33. [238] Duméril represents the teeth of the _vomer_ as separated from those of the _os palatinum_ by a gap. This is probably accidental, since Gegenbaur (Friedrich u. Gegenbaur, the skull of Axolotl, Würzburg, 1849) figures the rows of teeth as passing over from the one bone to the other without interruption. This was the case with the Axolotls which I have been able to examine on this point; but this small discrepancy is, however, quite immaterial to the question here under consideration. [239] See O. Hertwig “Über das Zahnsystem der Amphibien und seine Bedeutung für die Genese des Skelets der Mundhöhle.” Archiv. für microsc. Anat., vol. xi. Supplement, 1874. [240] [Eng. ed. These Amblystomas have since died and have been minutely described by Dr. Wiedersheim. See his memoir, “Zur Anatomie des _Amblystoma Weismanni_,” in Zeit. für wiss. Zool., vol. xxxii. p. 216.] [241] See Strauch, _loc. cit._ p. 10. [242] See Part I. of this volume. [243] [This is the principle of “Degeneration” recognized by Darwin (see “Origin of Species,” 6th ed. p. 389, and “Descent of Man,” vol. i. p. 206), and given fuller expression to by Dr. Anton Dohrn (see his work entitled “Der Ursprung der Wirbelthiere und das Princip des Functionswechsels.” Leipzig, 1875). A large number of cases have been brought together by Prof. E. R. Lankester, in his recent interesting work on “Degeneration, a Chapter in Darwinism.” Nature series, 1880. R.M.] [244] “Sulla Larva del _Triton Alpestris_.” Archivio per la Zoologia. Genova e Torino, 1861, vol. i. pp. 206-211. [245] See also Lubbock “On the Origin and Metamorphoses of Insects,” London, 1874. [246] See the first essay “On the Seasonal Dimorphism of Butterflies,” p. 82.