Nodules, phosphatic, in azoic rocks, 269.

Oak, varieties of, 51.
Onites apelles, 123.
Orchis, pollen of, 173.

Organs of extreme perfection, 167.
electric, of fishes, 172
of little importance, 174.
homologous, 377.
rudiments of, 391.

Ornithorhynchus, 100, 362.
Ostrich not capable of flight, 123.
habit of laying eggs together, 194.
American, two species of, 305.
Otter, habits of, how acquired, 161.
Ouzel, water, 166.

Owen, Prof., on birds not flying, 123.
on vegetative repetition, 135.

on variable length of arms in ourang-
outang, 136.

on the swim-bladder of fishes, 171.
on electric organs, 172.

on fossil horse of La Plata, 279.

on relations of ruminants and pachy-
derms, 288.

on fossil birds of New Zealand, 296.
on succession of types, 296.
on affinities of the dugong, 361.
on homologous organs, 378.

on the metamorphosis of cephalo-
pods and spiders, 384.

Pacific Ocean, faunas of, 304.

Paley on no organ formed to give pain,
179.

Pallas on the fertility of the wild stocks
of domestic animals, 224.

Paraguay, cattle destroyed by flies, 71.
Parasites, 194.

Partridge, dirt on feet, 316.

Parts greatly developed, variable, 136.
degrees of utility of, 179.

Parus major, 164.

Passiflora, 221.

Peaches in United States, 81.

Pear, grafts of, 231.

Pelargonium, flowers of, 132.

sterility of, 222.

Pelvis of women, 131.

Peloria, 132.

Period, glacial, 318.

Petrels, habits of, 165.

Phasianus, fertility of hybrids, 224.
Pheasant, young, wild, 192.

Philippi on tertiary species in Sicily, 273.
Pictet, Prof., on groups of species sudden.
ly appearing, 264, 267.

on rate of organic change, 274.

on continuous succession of genera,
277.

on close alliance of fossils in con-
secutive formations, 293.

on embryological succession, 295.
Pierce, Mr., on varieties of wolves, 87.
Pigeons with feathered feet and skin be-
tween toes, 18.

breeds described, and origin of, 25.
breeds of, how produced, 41, 44.
tumbler, not being able to get out of
egg, 83.

reverting to blue color, 144.

instinct of tumbling, 191.

carriers, killed by hawks, 315.
young of, 387.

Pistil, rudimentary, 392.

Plants, poisonous, not affecting certain
coloured animals, 18.

selection applied to, 36.

gradual improvement of, 40.

not improved in barbarous countries,
40.

destroyed by insects, 66.

in midst of rarge, have to struggle
with other plants, 75.

nectar of, 87.

fleshy, on sea-shores, 121.

fresh-water, distribution of, 336.

low in scale, widely distril uted, 353.
Plumage, laws of change in sexes of birds,

85.

Rattle-snake, 179.

Reason and instinct, 186.

Recapitulation, general, 398.

Reciprocity of crosses, 228.

Record, geological, imperfect, 245.
Rengger on flies destroying cattle, 70.
Reproduction, rate of, 63.

Resemblance to parents in mongre.s and
hybrids, 241.

Reversion, law of inheritance, 20.

in pigeons to blue colour, 144.
Rhododendron, sterility of, 222.
Richard, Prof., on Aspicarpa, 363.
Richardson, Sir J., on structure of squir-
rels, 162.

on fishes of the southern hemisphere,
327.

Robinia, grafts of, 231.

Rodents, blind, 125.

Rudimentary organs, 391.

Sphex, parasitic, 195.

362.

Sageret on grafts, 231.

Salmons, males fighting, and hooked jaws
of, 84.

Salt water, how far injurious to seeds, 312.
Saurophagus sulphuratus, 164.
Schiödte on blind insects, 126.
Schlegel on snakes, 131.

Sea-water, how far injurious to seeds, 312.
Sebright, Sir J., on crossed animals, 25,

on selection of pigeons, 34.

Sedgwick, Prof., on groups of species sud-
denly appearing, 264.

Seedlings destroyed by insects, 66
Seeds, nutriment in, 75.

winged, 133.

power of resisting salt water, 312.
in crops and intestines of birds, 315.
eaten by fish, 316, 337.

in mud, 337.

hooked, on islands, 341.

Selection of domestic products, 33.
principle not of recent origin, 36.
unconscious, 37.
natural, 77.

sexual, 83.

Spitz-dog crossed with fox, 236.
Sports in plants, 16.

Sprengle, C. C., on crossing, 92.

on ray-florets, 132.

of hybrids, 218.

laws of, 225.
causes of, 232.

from unfavourable conditions, 234.
of certain varieties, 237.

St. Helena, productions of, 339.

St. Hilaire, Aug., on classification, 364.
St. John, Mr., on habits of cats, 86.
Sting of bee, 180.

Stocks, aboriginal, of domestic animals, 23.
Strata, thickness of, in Britain, 249.
Stripes on horses, 147.

Structure, degrees of utility of, 179.
Struggle for existence, 60.

Succession, geological, 273.

Succession of types in same areas, 295.

Swallow, one species supplanting another,

74.

to, 95.

Sexes, relations of, 83.

Sexual characters variable, 141.

selection, 83.

Sheep, Merino, their selection, 35.

System, natural, 360.

Tail of giraffe, 174.

of aquatic animals, 175.
rudimentary, 394.

duced, 39.

mountain, varieties of, 73.

Shells, colours of, 121.

littoral, seldom embedded, 253.
Tresh-water, dispersal of, 335.
of Madeira, 341.

land, distribution of, 346.

Silene, fertility of crosses, 227.

Silliman, Prof., on blind rat, 125.

Skulls of young mammals, 176, 380.
Slave-making instinct, 195.

Smith, Col. Hamilton, on striped horses,
148.

Mr. Fred., on slave-making ants,
195.

Tausch on umbelliferous flowers, 132.
Teeth and hair correlated, 131.

embryonic, traces of, in birds, 391.
rudimentary, in embryonic calf, 391,
416.

Tegetmeier, Mr., on cells of bees, 202, 207.
Temminck on distribution aiding classifi-
cation, 365.

Thouin on grafts, 231.

Thrash, aquatic species of, 166.

mocking, of the Galapagos, 350.
young of, spotted, 382.

nest of, 215.

Thuret, M., on crossed fusi, 228.
Thwaites, Mr., on acclimatisation, 128.

analogous in distinct species, 144.

Varieties, natural, 46.

struggle between, 73.

domestic, extinction of, 104.
transitional, rarity of, 154.
when crossed, fertile, 236.

when crossed, sterile, 237.
classification of, 368.

Verbascum, sterility of, 222.
varieties of, crossed, 238.

pials, 108.

on greatly developed parts being
variable, 136.

on cells of bees, 200.

on general affinities, 373.

Water-ouzel, 166.

Watson, Mr. H. C., on range of varieties
of British plants, 58.

on acclimatisation, 128.
on flora of Azores, 316.

on Alpine plants, 320, 327.

on rarity of intermediate varieties,
158.

Weald, denudation of, 250.

Web of feet in water-birds, 166.

West Indian islands, mammals of, 344.
Westwood on species in large genera being
closely allied to others, 57.

on the tarsi of Engidæ, 142.

on the antennæ of hymenopterous
insects, 362.

Whales, fossil, 265.

Wheat, varieties of, 105.

White Mountains, flora of, 318.
Wings, reduction of size, 123.

of insects homologous with bran-
chiæ, 171.

rudimentary, in insects, 391.
Wolf crossed with dog, 191.

of Falkland Isles, 343.

Wollaston, Mr., on varieties of insects, 50.
on fossil varieties of land-shells in
Madeira, 53.

on colours of insects on sea-shore,
121.

on wingless beetles, 124.

on rarity of intermediate varieties,
158.

on insular insects, 339.

cies, 284.

Viola tricolor, 71.

Volcanic islands, denudation of, 249.
Vulture, naked skin on head, 176.

Wading-birds, 337.

on sub-breeds of sheep, 39.

on rudimentary horns in young cat-
tle, 394.

Zebra, stripes on, 147.