enskjoeld, Prof., on absence of perpetual snow in N. Asia, 135
on recent milder climate in Spitzbergen, 182
on former Polar climates, 187
on geology of Spitzbergen, 188
North America, glacial phenomena in, 116
interglacial warm periods in, 121
condition of, in Tertiary period, 194
Northern genera of plants in S. temperate America, 521
hemisphere, absence of southern plants from, 527
flora, hardiness of, 528

O.
Ocean-currents as carriers of plants, 81
as affecting interglacial periods, 152
as determining climate, 153
effects of, in Tertiary times, 196
Ocean, Darwin on permanence of, 100
Oceanic and continental islands, 242
Oceanic islands a proof of the permanence of oceans, 100
Oceanic islands, 244
--the Azores, 247
general remarks on, 329
Octodontidae, 27
_Oenanthe fluviatilis_, 361
Oeninghen, Miocene flora of, 183
_Oenothera odorata_, on a railway bank, 514
Oliver, Professor, on peculiar Bermudan plants, 272
Operculata, scarcity of, in the Sandwich Islands, 317
_Ophrys apifera_, temporary appearance of, 514
Orchideae, species have restricted ranges, 505
Orchids, abundance of, in Bourbon and Mauritius, 446
why almost universal in the tropics, 446
Orders, distribution of, 30
Organic change dependent on change of conditions, 225, 228
Oriental Region, definition of, 44
mammals and birds of, 44
reptiles of, 45
insects of, 45
Origin of new species, 56, 60
of new genera, 61
of the Galapagos flora, 288
of the beetles of St. Helena, 298
of Australian element in the New Zealand flora, 498
Orkney, peculiar fishes of, 341
Orthonyx not a New Zealand genus, 483
Osprey, wide range of, 15
Ostriches, limitation of, 30
Otter-like mammal in New Zealand, 475
Overlapping and discontinuous areas, 28

P.
_Pachyglossa aureolimbata_, in Celebes, 463
Palaearctic Region, limits of, 39
characteristic features of, 41
Palaeozoic formations, depth of, round London, 218
Palm confined to Round Island, 444
Panax, fossil in Greenland, 186
Papilio, 17
Paraguay, no wild horses or cattle in, 226
Parnassius, Palaearctic, 42
_Parus ater_, 19
_P. borealis_, 19, 64
_P. britannicus_, 321
_P. camtschatkensis_, 19
_P. cinctus_, 20
_P. coeruleus_, 20
_P. cyaneus_, 20
_P. cristatus_, 20
_P. ledouci_, 20
_P. lugubris_, 20
_P. major_, 19
_