SEXUAL. 
INDEX. 
SLAVERY. 
463 
i. 279 ; gradation of, in birds, ii. 
135. 
Sexual and natural selection, con- 
trasted, i. 278. 
Sexual characters, effects of the loss 
of, i. 284; limitation of, i. 284. 
Sexual differences in man, i. 14. 
Sexual selection, explanation of, i. 
256, 260, 271 ; influence of, on the 
colouring of Lepidoptera, i. 403 ; 
action of, in mankind, ii. 368. 
Sexual similarity, i. 277. • 
Sharks, prehensile organs of male, 
ii. 1. 
Sharpe, R. B., on Tanysiptera sylvia, 
ii. 165 ; on Ceryle^ ii. 173 ; on the 
young male of Dacelo Gaudichaudi^ 
ii. 188. 
Shaw, Mr., on the pugnacity of the 
male salmon, ii. 3. 
Shaw, J., on the decorations of birds, 
ii. 71. 
Sheep, danger-signals of, i. 74; sex- 
ual differences in the horns of, i. 
283 ; horns of, i. 289, ii. 246, 259 ; . 
domestic, sexual differences of, late 
developed, i. 293 ; numerical pro- 
portion of the sexes in, i. 304 ; 
mode of fighting of, ii. 249 ; arched 
foreheads of some, ii. 284. 
Sheep, Merino, loss of horns in fe- 
males of, i. 284; horns of, i. 289. 
Shells, difference in form of, in male 
and female Gasteropoda, i. 324 ; 
beautiful colours and shapes of, i. 
326. 
Shield-drake, pairing with a com- 
mon duck, ii. 114; New Zealand, 
sexes and young of, ii. 206. 
Shooter, J., on the Kaffirs, ii. 347 ; 
on the marriage - customs of the 
Kaffirs, ii. 373. 
Shrew-mice, odour of, ii. 279. 
Shrike, Drongo, ii. 179. 
Shrikes, characters of young, ii. 
185. 
Shuckard, W. E., on sexual differ- 
ences in the wings of Hymenoptera, 
i. 435. 
Shyness of adorned male birds, ii. 
97. 
Siagonium, proportions of the sexes 
in, i. 314; dimorphism in males of, 
i. 374. 
Siam, proportion of male and female 
births in, i. 303. 
Siamese, general beardlessness of the, 
ii. 321 ; notions of beauty of the, 
ii. 345; hairy family of, ii. 378. 
Siebold, C. T. von, on the auditory 
apparatus of the stridulant ortho- 
ptera, i. 353. 
SiGrHT, inheritance of long and short, 
i. 118. 
Signal-cries of monkeys, i. 57. 
Silk-moth, difference of size of the 
male and female cocoons of the, i. 346; 
pairing of the, i. 401 ; male, fer- 
tilising two or three females, i. 406 ; 
proportion of the sexes in, i. 309, 
311; Ailanthus, Prof. Ganestrini, 
on the destruction of its larvae by 
wasps, i. 311. 
SiMiADAS, i. 195 ; their origin and 
divisions, i. 213. 
Similarity, sexual, i. 277. 
Singing of theCicadae and Fulgoridas, 
i. 351 ; of tree-frop, ii. 27 ; of 
birds, object of the, ii. 52. 
SiRENiA, nakedness of, i. 148. 
Sirex juvencus, i. 365. 
SiRiciDAC, difference of the sexes in, 
i. 365. 
Siskin, ii. 85 ; pairing with a canary, 
ii. 115. 
Sitana, throat-pouch of the males of, 
ii. 33, 36. 
Size, relative, of the sexes of insects, 
i. 345. 
Skin, movement of the, i. 19 ; naked- 
ness of, in man, i. 148 ; colour of 
the, i. 241. 
Skin and hair, correlation of colour 
of, i. 248. 
Skull, variation of, in man, i. 108 ; 
cubic contents of, no absolute test 
of intellect, i. 145; Neanderthal, 
capacity of the, i. 146 ; causes of 
modification of the, i. 147 ; differ- 
ence of, in form and capacity, in 
different races of men, i. 216 ; vari- 
ability of the shape of the, i. 226 ; 
differences of, in the sexes in man, 
ii. 317 ; artificial modifications of 
the shape of, ii. 340. 
Skunk, odour emitted by the, ii. 279. 
Slavery, prevalence of, i. 94 ; of 
women, ii. 366. 
