Sars, development of _Leptodora hyalina_, 94. _Saturnia._ _S. Yamamai_, variable in first stage only, 406; _S. carpini_, development of larva of local forms, 419. _Satyrinæ_, hibernation of larvæ, 73. Saussure, De, on _Siredon Mexicanus_, 565, 602; physical character of Mexican Lake, 603. Saw-flies, protective habits of larvæ, 290. Schmankewitsch, transformation of _Artemia_, 635. Schmidt, Oscar, on convergence of character, 396, 459; on variability, 654. Schreibers, sexual _Triton_ larvæ, 591; arrested tadpoles, 607. Schulze, F. E., parasitism in _Medusæ_, 699. Science, function of, 640. Scudder, S. H., embryonic larvæ of butterflies, 166. Seasonal dimorphism, origin and significance, 1; seasonal change of colour in animals, 7; and climatic variation, 45; seasonal adaptation in caterpillars, 305. Seidlitz, reproduction of Axolotl, 571; white var. of hare, 662. _Selenia tetralunaria_, _S. illunaria_, _S. lunaria_, and _S. illustraria_, seasonal dimorphism, 4. Semper, C., origin of alternation of generations, 84; transformation of _Amblystoma mavortium_, 629. Semper, G., young Sphinx-larvæ, 166; figures of caterpillars referred to, 522. Senses, physiology of, 711. Sepp, figure of caterpillar referred to, 262. _Sesiidæ_, affinities of, 370. Sexual dimorphism, of butterflies, 32, 250; of caterpillars, 308, 527, 534; secondary sexual characters, 62; sexual selection, 69, 102. Siebold, Von, on _Pulmonifera_, 590. _Siredon._ _S. Mexicanus_, habits, 565; _S. lichenoides_, transformation, 567, 630; phyletic advance of genus, 584; retention of genus, 610; _S. tigrinus_ from L. St. Isabel, 626. Slater, J. W., food of gaily coloured caterpillars, 294. _Smerinthus_, larvæ of, 232; _S. Tiliæ_, 233; 4th stage, 235; _S. Populi_, 236; and stage, 237; 3rd and 4th stages, 238; 5th stage, 239; _S. ocellatus_, 240; dimorphism of larva, 241; _S. Tiliæ_, variable in two stages, 405; North American species of, 453; _S. tatarinovii_, and _S. planus_, larvæ, 244. Species, causes of transformation of, 116; nature of, 671. Specific characters, 91; may originate through direct action, 100. Specific constitution, 112. Spencer, Herbert, theory of descent, 645; variability, 654; law of growth, 655. Spermatozoa, of _Amblystoma_, 593; of _Lissotriton punctatus_, 595. Speyer, Dr., seasonal dimorphism of moths, 4; of _P. phlæas_ in Germany, 50. _Sphingidæ_, oviposition, 164; congruence and incongruence in genera, 450. _Sphinx_-markings, ontogeny and morphology, 177. Larvæ of genus, 259; _S. Convolvuli_, 650. Origination of markings, 273; law of development, 274; forms of markings, 309; _S. Ligustri_, constant in three stages, 405.