4.
Myrmecocystus, 239.
Myrmica, eyes of, 240.

N.

Nails, rudimentary, 454.
Natural history, future progress of, 485.
---- selection, 80.
---- system, 413.
Naturalisation of forms distinct from the indigenous species, 115.
---- in New Zealand, 201.
Nautilus, Silurian, 307.
Nectar of plants, 92.
Nectaries, how formed, 92.
Nelumbium luteum, 387.
Nests, variation in, 211.
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, 252.
Nodules, phosphatic, in azoic rocks, 308.

O.

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, and nascent, 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, Prof., 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, 339.
----, on succession of types, 339.
----, on affinities of the dugong, 414.
----, on homologous organs, 434.
----, on the metamorphosis of cephalopods and spiders, 442.

P.

Pacific Ocean, faunas of, 348.
Paley on no organ formed to give pain, 201.
Pallas on the fertility of the wild stocks of domestic animals, 254.
Paraguay, cattle destroyed by flies, 72.
Parasites, 217.
Partridge, dirt on feet, 363.
Parts greatly developed, variable, 150.
----, degrees of utility of, 201.
Parus major, 184.
Passiflora, 251.
Peaches in United States, 85.
Pear, grafts of, 262.
{499}
Pelargonium, flowers of, 145.
----, sterility of, 251.
Pelvis of women, 144