isseltoe, complex relations of, 3.

Mississippi, rate of deposition at mouth, 284.

Mocking-thrush of the Galapagos, 402.

Modification of species, how far applicable, 483.

Moles, blind, 137.

Mongrels:
fertility and sterility of, 267.
and hybrids compared, 272.

Monkeys, fossil, 303,

Monocanthus, 424.

Mons, Van, on the origin of fruit-trees, 29, 39.

Moquin-Tandon on sea-side plants, 132.

Morphology, 434.

Mozart, musical powers of, 209.

Mud, seeds in, 386.

Mules, striped, 165.

Muller, Dr. F., on Alpine Australian plants, 375.

Murchison, Sir R.:
on the formations of Russia, 289.
on azoic formations, 307.
on extinction, 317.

Mustela vison, 179.

Myanthus, 424.

Myrmecocystus, 238.

Myrmica, eyes of, 240.

Nails, rudimentary, 453.

Natural history:
future progress of, 484.
selection, 80.
system, 413.

Naturalisation:
of forms distinct from the indigenous species, 115.
in New Zealand, 201.

Nautilus, Silurian, 306.

Nectar of plants, 92.

Nectaries, how formed, 92.

Nelumbium luteum, 387.

Nests, variation in, 212.

Neuter insects, 236.

Newman, Mr., on humble-bees, 74.

New Zealand:
productions of, not perfect, 201.
naturalised products of, 337.
fossil birds of, 339.
glacial action in, 373,
crustaceans of, 376.
algae of, 376.
number of plants of, 389.
flora of, 399.

Nicotiana:
crossed varieties of, 271.
certain species very sterile, 257.

Noble, Mr., on fertility of Rhododendron, 251.

Nodules, phosphatic, in azoic rocks, 307,

Oak, varieties of, 50.

Onites apelles, 135.

Orchis, pollen of, 193,

Organs:
of extreme perfection, 186,
electric, of fishes, 192.
of little importance, 194.
homologous, 434.
rudiments of, 450.

Ornithorhynchus, 107, 416.

Ostrich:
not capable of flight, 134.
habit of laying eggs together, 218.
American, two species of, 349.

Otter, habits of, how acquired, 179.

Ouzel, water, 185.

Owen, Professor:
on birds not flying, 134.
on vegetative repetition, 149.
on variable length of arms in ourang-outang, 150.
on the swim-bladder of fishes, 191.
on electric organs, 192.
on fossil horse of La Plata, 319.
on relations of ruminants and pachyderms, 329.
on fossil birds of New Zealand,