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.