_Lumbricus_ sp., alimentary canal of, *131; cross-section of, *132; structure and life of, 127. Lung-fish, 285. _Lycena_, scales of wings of, *206. Lycosidæ, 235. _Lynx rufus_, 398. Macrocheira, 154. _Madrepora cervicornis_, *105. _Malaclemmys palustris_, 314. Malaria and mosquitoes, 205. Mallard, 347. Mammal, circulation of blood in, *376. Mammalia, 373. Mammals, 373; body form and structure of, 381; classification of, 389; development and life-history of, 388; habits, instinct and reason of, 388; making skins of, 470. Man, 398. Man-of-war, Portuguese, 98, *97. Marsupialia, 389. _Martesia xylophaga_, *251. Massasauga, 32. May-flies, 194. May-fly, nymph of, *197. Medusa, *101. Megalobatrachus, 298. _Megascops asio_, *352, 353. _Melanerpes erythrocephalus_, 355. _Melanerpes formicivorus_, 356. _Melanoplus_ sp., ear of, *187; structure and life-history of, 157. _Melanoplus vibittatus_, 157. _Melanoplus differentialis_, 157. _Melanoplus femur-rubrum_, 157, *158. _Melanoplus spretus_, 157. _Meleagrina margaritifera_, 250. _Merula migratoria propinqua_, *368. Metamorphosis, complete, 171, 188, 189; incomplete, 171, 189. Metazoa, defined, 43. Mice, 391. _Micropterus dolomien_, 282. _Micropterus salmoides_, 282. Migration of birds, 367. Mimicry, 430. Millipeds, 226. Mite, cheese, *230. Mites, 229. Modifications of structure and function, 29. Moles, 391. Mollusca, 239. Molluscs, 239; classification of, 246; development of, 246; form and structure of, 245. Molting, 361; of birds, 361. Monitor, 318. Monkey, *400. _Momomerium minutum_, *224. Monster, Gila, *317. Moose, *385, 396. Morphology, defined, 3. Mosquito, 202, *203. Mosquitoes, 201; and malaria, 205; and yellow fever, 205. Moth, forest tent-caterpillar, life-history of, *207. Moths, 205. Mourning dove, 351. Mouse, life-history and habits of, 379; structure of, 373. Mud-eel, 297. Mud-hen, 349. Mud-puppies, 297. Mud-turtle, 313. Multiplication of one-celled animals, 59; of many-celled animals, 61. Murres, *344. Muscles of toad, structure of, 41. _Mus decumanus_, 391. _Mus musculus_, structure of, 373. _Mus rattus_, 391. Musk-rat, 391. Mussel, fresh-water, life-history and habits of, 243; structure of, 239. _Mya arenaria_, 247. _Myotis subulatus_, 392. Myriapoda, 144, 226. _Mytilus californianus_, *248. _Myxine_, 279. Names, scientific, 68. _Narcobatis_, 281. _Natrix sipedon_, 320. Nautilus, 255; pearly, 258. _Nautilus pompilius_, 258. _Necturus_, 297, 298. Nemathelminthes, 140. _Neotoma pennsylvanica_, 391. Nereid, *134. _Nereis_ sp., *134. Nesting of birds, 366. Nest of oriole, *365. _Nettion carolinense_, 347. Night-hawk, 356. Night-heron, 348.