species are mimickers, 85.

NATURAL selection, the principle stated, 41-43;
general acceptance of the theory of, 46;
tabular demonstration of, 302;
outline of theory of, 307;
its effects on man and animals different, 311;
hardly acts among civilized societies, 330;
what it can not do, 333;
cannot produce injurious or useless modifications, 334.

NECTARINEIDAE, 254.

NECYDALIDAE, mimic Hymenoptera, 96.

_Nemophas grayi_, a Longicorn mimicked by a Longicorn, 95.

NESTS of Birds, why different, 215;
of young birds, how built, 219;
construction of, described by Levaillant, 224;
imperfections in, 229;
influenced by changed conditions and persistent habits, 232;
classification of, according to function, 237.

NEW FORMS, how produced by variation and selection, 286.

NEW GUINEA, relation of the several Papuan islands to, 194.

NOCTURNAL animals, colours of, 51.

NOMADA, 98.

OBEREA, species resemble Tenthredinidae, 96.

_Odontocera odyneroides_, 96.

ODONTOCHEILA, 97.

_Odyncrus sinuatus_, 90.

_Onthophilus sulcatus_, like a seed, 58.

_Onychocerus scorpio_, resembles bark, 56.

ORANGE-TIP butterfly, protective colouring of, 59.

ORCHIS, structure of an, explained by natural selection, 271.

_Orgyia antiqua_ and _O. gonostigma_, autumnal colours of, 62.

ORIOLIDAE, 253.

_Ornithoptera priamus_, 145, 173;
_O. helena_, 173.

_Oxyrhopus petolarius_, _O. trigeminus_, _O. formosus_, 102.

OWEN, Professor, on more generalized structure of extinct
animals, 298.

_Pachyotris fabricii_, 96.

PACHYRHYNCHI, weevils mimicked by Longicorns, 95.

PALEOTHERIUM, 299.

PALOPLOTHERIUM, 299.

PAPILIO, black and red group imitated, 84.

_Papilio achates_, 147;
_P. adamantius_, 171;
_P. aenigma_, 87;
_P. agamemnon_, 141, 158, 170, 171;
_P. agestor_, 180;
_P. alphenor_, 148, 169;
_P. amanga_, 151;
_P. androcles_, 171;
_P. androgeus_, 88, 147, 180, 183;
_P. antiphates_, 141, 171;
_P. antiphus_, 87, 150, 170, 180, 183;
_P. aristaeus_, 171;
_P. arjuna_, 141;
_P. ascalaphus_, 171;
_P. autolycus_, 160;
_P. bathycles_, 141;
_P. blumei_, 171;
_P. brama_, 171;
_P. caunus_, 87, 179;
_P. codrus_, 160, 171;
_P. coeon_, 88, 146, 180, 182;
_P. deiphobus_, 140;
_P. deiphontes_, 171;
_P. delessertii_,