_Nirmus præstans_, *194. Non-calcarea, 91. Notes, 447, 448. Notochord, 259. _Notonecta_, 197, 199. Nucleus, 38. Nudibranchs, 252, *254. _Numenius longirostris_, 350. _Nyctea nyctea_, 353. _Nycticorax_, 348. Octopi, 255. Octopods, 256. _Odocoileus americanus_, 396. Odonata, 194. Oligochætæ, 136. _Olor_, 347. _Ommatostrephes californica_, *257. _Oncorhynchus tschawtscha_, 283. One-celled animals, multiplication of, 57. Ooze, foraminifera, 81; radiolaria, 81. _Opheosaurus ventralis_, 317. Ophiuroidea, 121, 122. Opossum, 389. Order, defined, 72. _Oreamnos montanus_, 397. Organ, defined, 14. Orthoptera, 192; sound-making of, 193. Orb-web of Epeiridæ, 236. _Ostrea virginiana_, 248. Ostriches, 341, *342. _Otocoris alpestris_, *358. _Ovis canadensis_, *383, 396. Owl, burrowing, 353; great gray, 353; great horned, 353; snowy, 353. Oyster, 248. Oyster-crab, 154. Oyster-drills, 255. Oysters, 246; "seed" of, 249; "spat" of, 249. _Pagurus samuelis_, *153. Paludicolæ, 348. Panther, 398. _Paramœcium_, *35; multiplication of, 60; structure and life of, 34. Parasitism, 415. Paroquet, Carolina, 353. Parrots, 353. _Passer domesticus_, dissection of, (facing) *327; life-history and habits of, 335; structure of, 327. Passeres, 357. Pearl-oyster, *249. _Pelecanus californicus_, 346. _Pelecanus erythrorhynchus_, 346. _Pelecanus fuscus_, 346. Pelecypoda, 246. Pelican, brown, 346; white, 346. _Pentacrinus_ sp., *126. _Pentacta frondosa_, *125. _Peripatus eiseni_, *226. _Perla_ sp., *182. Petrels, 345. _Petromyzon marinus_, *278. _Phalacrocorax_, 346. Pheasants, 350. _Phoca vitulina_, 397. Phœbe, black, nest and eggs of, *340. _Pholas_ sp., *250. _Phrynosoma_, 318. Phylloxera, grape, 198, 201. _Phylloxera vastatrix_, 198, 201. Phylum, defined, 73. _Physalia_ sp., *97. _Physeter macrocephalus_, 393. Physiology, defined, 3. Pici, 354. Pickerel-frog, 300. Pigeon, band-tailed, 351; passenger, 351. _Pinnotheres_, 154. Pipe-fish, 285. Pisces, 263. _Pituophis bellona_, *323. _Planaria_ sp., *138. Planarian, fresh-water, *138; marine, *138. Planarians, 137. Plant-lice, 197, 200. Planula, 96 Platyhelminthes, 137. _Plectrophenax nivalis_, *358. _Plethodon_, 297. Plover, field, 349. Pluteus, 119. _Podilymbus podiceps_, 343. Poison-fangs of rattlesnake, *324. _Pollicipes polymenus_, *153. Polymorphism, 96. _Polynœ brevisetosa_, *134. Polyps, 92, 97. _Pomoxis annularis_, 282. _Pomoxis separoides_, 282. Pond-snails, 252. Porcupine, 390. Porcupine-fish, 285. Porifera, 84. Porpoises, 393. _Porzana carolina_, 349. Prairie-chicken, 350. Prawns, 152. Preparations, preserving anatomical, 452. Primates, 398.