[314] See Von Hartmann, _loc. cit._ p. 158. INDEX. A. Abbot and Smith, descriptions of larvæ, 192, 216, 261, 263, 268, 452, 453. _Acherontia Atropos_, South African form of larva, 263, 324, 531; larva in Spain, 324; larva phytophagically variable, 531. _Acosmeryx anceus_, larva, 192. _Acræa_ and Maracujà butterflies as larvæ, pupæ, and imagines, 536. _Acronycta_, affinities of genus, 169. Adaptation, 281, 589; analogous, 376; physiological, 590; mutual, 647. Allen, J. A., variation in birds and mammals, 658. Alpine form of _P. Napi_, 40. Alpine hare, seasonal change of colour, 7, 660. Alternation of generations, 80, 699, 702. _Amblystoma._ _A. mavortium_ from _Siredon lichenoides_, 567; _A. tigrinum_ bred by Duméril, 567; distribution of species of genus, 569; habits of species, 573; a reversion form, 531, 592; sterility of, 593; oviposition by, 594, 623; definition of genus, 610; degeneration of, 612; causes of reversion of, 600, 608, 613, 620, 631; _A. punctatum_ and _A. fasciatum_, development of, 623; summer sleep of, 628; _A. mavortium_, metamorphosis of, 629. _Ambulyx gannascus_ and _A. liturata_, larvæ, 245. Amixia, the principle of, 46, 110. Ammonites, 275. _Ampelophaga rubiginosa_, larva, 192. Amphibia of Upper Engadine, 615. _Amphiuma_, characters of genus, 579. _Anceryx_, larva, 264; stages 3, 4, and 5, 266. _Aphaniptera_, characters of, 498. Aphides, organic reproduction of, 97. _Araschnia._ _A. levana_ and _A. prorsa_ seasonally dimorphic, 2; dimorphism of larvæ, 6; _A. levana_, first experiments with, 10; _A. var. porima_, artificial production of, 10, 17; _A. levana_, Dorfmeister’s experiments with, 11; explanation of seasonal dimorphism of, 19; northern, extension of, 20; _A. prorsa_ gradual origination of, 22; _A. levana_, reversion of, caused by high temperature, 37; the _levana_ form the most constant, 43, and sexually dimorphic, 43; summer and winter forms compared, 56; experiments with _A. levana_, 117; _A. levana_, variable in all three stages, 405; incongruence in genus, 449. Argent, W. J., phytophagic variability of larva of _Sphinx Ligustri_, 306. _Argynnis paphia_, dimorphism of, 250. _Artemia salina_ and _A. Milhausenii_, transformations of, 635. _Ascaris nigrovenosa_, propagation of, 90. Askenasy, on limits of variability, 114. Atavism and arrested growth, 587. _Aterica meleagris_, colour variations of, 8. Atoms, actions of, 710; sensibility of, 714. Axolotl, transformation into Amblystoma, 555; experiments with, 558; duration of transformation, 563; conditions of metamorphosis of, 564; distinguishing characters, 575. B.