Varieties, natural, 32.

struggle between, 59.

-, domestic, extinction of, 86.
-, transitional, rarity of, 134.
when crossed, fertile, 257.
when crossed, sterile, 256.
classification of, 371.
Verbascum, sterility of, 238.

varieties of, crossed, 258.
Verlot, M., on double stocks, 230.
Verneuil, M. de, on the succession of
species, 299.

Vibracula of the Polyzoa, 193.

Viola, small imperfect flowers of, 173.
tricolor, 57.

Virchow, on the structure of the
crystalline lens, 145.
Virginia, pigs of, 66.

Volcanic islands, denudation of, 268.
Vulture, naked skin on head, 158.

Wallace, Mr., on the walking-stick
insect, 182.

-, on laws of geographical distri
bution, 322.

on the Malay Archipelago, 351.
on mimetic animals, 377.
Walsh, Mr. B. D., on phytophagic
forms, 38.

on equable variability, 125.
Water, fresh, productions of, 343.
Water-hen, 143.

Waterhouse, Mr., on Australian mar-
supials, 90.

on greatly developed parts
being variable, 119.

on the cells of bees, 220.

on general affinities, 379.
Water-ouzel, 142.

Watson, Mr. H. C., on range of va
rieties of British plants, 37, 46.

on acclimatisation, 112.

on flora of Azores, 328.

Wollaston, Mr., on varieties of in-
sects, 38.

-, on fossil varieties of shells in
Madeira, 42.

on colours of insects on sea-
shore, 107.

on wingless beetles, 109.

on rarity of intermediate va-
rieties, 136.

on insular insects, 347.

on land-shells of Madeira, natu-
ralised, 357.

Wolves, varieties of, 71.

Woodcock with earth attached to leg,
328.

Woodpecker, habits of, 141.

green colour of, 158.

Woodward, Mr., on the duration of
specific forms, 276.

on Pyrgoma, 284.

on the continuous succession of