_Leander_, 59, 179; Isopod parasitic on, 221; used for food, 245 Legs of Lobster, 8, 12 _Lepas_, 42; habitat, 155; nauplius, 148 _Lepeophthirus_, 225 _Leptodora_, 169 Leptostraca, 45 _Lernæa_, 226 Leucosiidæ, 109 _Ligia_, structure and habits, 200 _Limnoria_, 254 _Linuparus_, 269 _Lithodes_, 62, 94 Lithodidæ, 61 Liver of Lobster, 17 Lobsters: deep-sea, 121; fishery, 238 Lovén, S., on relict Crustacea, 181 Luminosity of deep-sea Crustacea, 125; of plankton Crustacea, 150 Lynceidæ, 165 Mackerel feeding on plankton, 250 _Macropodia_, masking habits, 97 _Maia_, masking habits, 96 Malacostraca, 43; fossil, 261 Mammoth Cave, Crayfish of, 185 Mandible of Lobster, 8, 14 Masked Crab, 99 Masking of Crabs, 96, 215 Maxilla of Lobster, 8; of _Argulus_, 41 Maxillipeds of Lobster, 8, 11 Maxillula of Lobster, 8 Medusæ, Amphipods on, 212 Megalopa of Shore Crab, 70 _Meganyctiphanes_, 56, 151 _Melia_, 215 _Mesidotea_, 181 Mesoplankton, 143 Messmates, 208 Metamorphosis of Lobster, 28; of Land Crabs, 191 Metanauplius of _Penæus_, 75 Mimicry, 204 _Mimonectes_, 145 Mitsukuri, K., on cultivation of Barnacles, 250 Mole Crabs, 102 Monstrillidæ, 230 Moulting of Lobster, 15; of Woodlice, 206 Mountain Shrimps, 181; structure and fossil allies, 264 Mouth-frame of Crabs, 62 Müller, Fritz: on larval stages of _Penæus_, 73; on habits of _Aratus_, 189 Müller, O. F., on Nauplius, 82 _Munida_, larva of, 71 _Munidopsis_: eyes, 123; eggs, 130 Murray River Lobster, 243 Mussels and Pea Crab, 217 Myodocopa, 39 Mysidacea, 46; development, 79; luminosity, 127; eyes, 153; and Hermit Crabs, 215; fossil, 263 _Mysis_, 47; in lakes, 181, 182 Natantia, 58; used for food, 243 Nauplius of _Penæus_, 73; of Crayfish, 79; of Opossum Shrimp, 79; of Branchiopoda, 80; of _Cyclops_, 82; of Ostracoda, 82; of Barnacles, 83; of _Lepas_, 148; of _Leptodora_, 170; of _Sacculina_, 233; eye, 40 _Nebalia_, 44; fossil allies, 261 Nebaliacea, 44 Necton, 138 Nematocarcinidæ, 128 _Nephrops_, 33; larva, 71; distribution, 132; fishery, 240 Nephropsidea, 33, 60 _Nephropsis_, 121 _Neptunus_, 156; used for food, 249 Neritic plankton, 141 Nervous system of Lobster, 20 _Niphargus_, 184 Northern Crayfishes, 176 Norway Lobster, 33; larva, 71; fishery, 240 Norwegian Prawn, 246 Notostraca, 36; habits, 162 Oceanic plankton, 141 Octopus preying on Crustacea, 89 _Ocypode_, 188; habits, 104; carnivorous, 195 Olfactory filaments of Lobster, 25 _Oniscus_, 51; Structure and habits, 201 Operculata, 43 Opossum Shrimps, 46; development of, 79 _Orchestia_, 107 Orientation, organs of, 24