OBEDIENCE. 
INDEX. 
ORYCTES. 
451 
o. 
Obedience, value of, i. 162. 
Observation, powers of, possessed by 
birds, iL 109. 
Occupations, sometimes a cause of 
diminished stature, i. 115; effect 
of, upon the proportions of the body, 
i. 116. 
Ocelli, absence of, in female Mutil- 
lidse, i. 341. 
Ocelli of birds, formation and vari- 
ability of the, ii. 132. 
Ocelot, sexual differences in the 
colouring of the, ii. 287. 
Ocyphdps lophot.es, ii. 96. 
Odonata, i. 314. 
Odonestis potatoria , sexual difference 
of colour in, i. 398. 
Odour, correlation of, with colour of 
skin, i. 248 ; emitted by snakes in 
the breeding-season, ii, 30 ; of 
mammals, ii. 278. 
Oecanthus nivalis , difference of colour 
in the sexes of, i. 361. 
Oiclemia , ii. 226, 227. 
Olivier, on sounds produced by 
Pimelia striata , i. 385. 
Omaloplia hrunnea , stridulation of, i. 
381. 
Onitis furcifer , processes of anterior | 
femora of the male, and on the 
head and thorax of the female, i. 
372. 
Onthophagus, i. 370. 
Ontkophagus rangifer , sexual differ- 
ences of, i. 369; variation in the 
horns of the male, i. 370. 
Ophtdia, sexual differences of, ii. 29. 
Opossum, wide range of, in America, 
i. 219. 
Optic nerve, atrophy of the, caused 
by destruction of the eye, i. 116. 
Orang-Outan, ii. 323 ; Bischoff on 
the agreement of the brain of the, 
with that of man, i. 11 ; adult age 
of the, i. 13 ; ears of the, i. 21 ; ver- 
miform appendage of, i. 27 ; plat- 
forms built by the, i. 36 ; alarmed 
at the sight of a turtle, i. 43 ; 
using a stick as a lever, i. 51 ; 
using missiles, i. 52 ; using the 
leaves of the Pandanus as a night 
covering, i. 53 ; hands of the, i. 
139 ; absence of mastoid processes 
in the, i. 143 ; direction of the 
hair on the arms of the, i. 192 ; its 
aberrant characters, i. 197 ; sup- 
posed evolution of the, i. 230 ; 
voice of the, ii. 276 ; monogamous 
habits of the, ii. 361 ; male, beard 
of the, ii. 284. 
Oranges, treatment of, by monkeys, 
i. 139. 
Orange-tip butterfly, i. 388, 393, 
394. 
Orchestia Darwinii, dimorphism of 
males of, i. 332. 
Orchestia Tucuratinga , limbs of, i. 
330, 331, 337. 
Ordeal, i. 68. 
Oreas canna , colours of, ii. 288. 
Orcas Derbianus , colours of, ii. 288, 
299. 
Organs, prehensile, i. 256 ; utilised 
for new purposes, ii. 335. 
Organic scale, von Baer’s definition 
of progress in, i. 211. 
Orioles, nidification of, ii. 167. 
Oriolus , species of, breeding in im- 
mature plumage, ii. 214, 215. 
Oriolus melnnocephalm , coloration of 
the sexes in, ii. 178. 
Ornaments, prevalence of similar, i. 
233 ; fondness of savages for, ii. 
338 ; of male birds, ii. 50. 
Ornamental characters, equal trans- 
mission of, to both sexes, iu mam- 
mals, ii. 297 ; of monkeys, ii. 306. 
Ornithoptera crccsus, i. 310. 
Ornithorhynchus , i. 200 ; spur of the 
male, ii. 242 ; reptilian tendency 
of, i. 204. 
Orocetes erythrogastra , young of, ii. 
219. 
Orhony, Grotto of, i. 28. 
Orsodacna atra , difference of colour 
in the sexes of, i. 368. 
Orthoptera, i. 352 ; metamorphosis 
of, i. 292; stridulating, auditory 
apparatus of, i. 353 ; colours of, i. 
360 ; rudimentary stridulating or- 
gans in female, i. 359 ; stimula- 
tion of the, and Homoptera, dis- 
cussed, i. 360. 
Ortygornis gularis , pugnacity of the 
male, ii. 44. 
Oryctes , stridulation of, i. 381 ; sexual 
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