INDEX 



541 



Morula, 38, 39 



Mosquitoes, 301, 302 



Moths, 302 



Motion, 75 (see locomotion); proto- 

 plasmic, 15 



Moulting, 279 



Mouth-parts (arthropods), 267, 273 



Mucous epithelium, 49 



Muscular system, 75; coelenterates, 182; 

 echinoderms, 216; annulates, 228; 

 mollusks, 247; arthropods, 280; verte- 

 brates, 345 



Muscular tissue, 58-60 



Mussel, 252, 254, 239, 258 



Mutation, 107, 488 



Mya, 239, 256 



Myctodera, 383 



Myotome, 313, 345 



Myriapoda, 296 



Mytilus, 258 



Nais, 238 



Natural history, 510 



Natural selection, 104 



Nauplius, 293 



Nautilus pearly 261; paper, 263 



Necator, 200 



Necturus, 380, 383 



Nemathelminthes, 199 



Nemertinea, 203 



Neornithes, 410 



Nephridia, 71, 72, 231, 344 



Nereis, 225, 236 



Nervous system, 76-83 (see sense or- 

 gans); ccelentrata, 182; echinoderms, 

 217; annulata, 231; mollusks, 251; 

 arthropods, 283; vertebrates, 347; 

 reptiles, 388; birds, 405; mammals, 

 446 



Nervous tissue, 60, 61 



Nettling cells, 181 



Neuron, 61 



Neuroptera, 298 



Newts, 383 



Nictitating membrane, 355; in birds, 



405 



Notochord, 311, 328 

 Nucleoplasm, 27 

 Nucleolus, 21 



Nucleus, 21 ; functions of, 26 

 Nutrition, 66; protozoa, 154; see di- 

 gestion, metabolism, etc. 

 Nutritive pole, 37 



Obelia, 185 



Ocelli, 285 



Occulina, 176 



Octopoda, 259 



Octopus, 262, 263 



Odonata, 298 



Odontophore, 244, 248 



(Esophagus, 334 



Oil glands, 326 



Olfactory nerves, 352 



Oligochasta, 237 



Ommatidium, 285 



Oniscus, 269 



Onychophora, 296 



Oocytes, 32, 33, 34 



Oogonia, 32, 33, 34 



Ophidia, 393 



Ophiuroidea, 220 



Optic nerve, 352, 355 



Orb-weavers, 307 



Organization, 19, 47, 65; of protozoa, 153 



Organs, 66 



Origin of tissues, 47 



Original home of animals, 135 



Orioles, 420 



Ornithodelphia, 449 



Ornithorhynchus, 449 



Orthoceratites, 262 



Orthoptera, 297 



Oscines, 429 



Osculum, 165 



Osmerus, 370 



Osseous tissue (bone), 56 



Ostrea, 259 



Ostrich, 411 



Otocyst, 8 1 (see also auditory organs). 



Otolith, 8 1 



Otter, 454 



Ovary, 74, 286, 344 



Oviduct, 252, 286, 344, 406 



Ovipositor, 272 



Oviparous, 345 



Ovum, 30 



Owls, 419, 420, 421 



