638 



INDEX. 



Lateral line, 143 ; Tactile papillae, 

 153 ; Generative organs, 184 ; Semi- 

 nal elements, 191. 



Nemertes — Proboscis, 141 ; Visual organs, 

 154. 



Nemertina — Incomplete metamerism, 130 ; 

 Proboscis, 140, 141 ; Nervous system, 

 147; Tactile setae, 152 ; Cephalic pits, 

 153 ; Visual organs, 154; Alimentary 

 canal, 157. 



Neomenia — Nervous system, 152; Enteric 

 brancbiaa, 164. 



Neophauta — Visual organs, 155. 



Nepa — Eespiratory tube, 289. 



Nephelis — Vascular system, 167 ; Excre- 

 tory organs, 177 ; Generative pro- 

 ducts, 190. 



Nephropneusta — Shell, 323 ; Nervous 

 system, 349 ; Jaws, 360 ; Excretory 

 organs, 378. 



Nerita— Heart, 371. 



Neritacea — Branchiae, 338. 



Neritina — Heart, 371. 



Neuroptera — Thorax, 237; Gnathites, 242 ; 

 Enteric canal, 272 ; Ovary, 302 ; Male 

 organs, 304. 



Nodosaridae — Shells, 81. 



Notidani— Branchial arches, 469 ; Clefts, 

 492. 



Notommata — Excretory organs, 175. 



Nudibranchiata — Branchiae, 338; Tenta- 

 cles, 352 ; Intestine, 362 ; Vessels, 

 372. 



Numida — Sternum, 443. 



Oceanidae — Marginal vesicles, 110. 



Octactiniae — Tentacles, 100 ; Transverse 

 axes, 100 ; Tentacles, 102 ; Gastric 

 system, 117. 



Octopoda — Tentacles, 327 ; Internal 

 skeleton, 340 ; Muscles, 343 ; Oto- 

 cysts, 357 ; Pharynx, 362 ; Liver, 

 366 ; Oviduct, 386. 



Octopus — Mantle, 325 ; Copulatory or- 

 gans, 327 ; Eye, 355 ; Salivary 

 glands, 363 ; Circulatory centres, 

 368 ; Figure, 373. 



Odontornithes — Teeth, 551. 



(Erstedia — Nervous system, 147; Auditory 

 organ, 156. 



Oikopleura — " House," 393. 



Oletera — Ovaries, 296. 



Olynthus — Gastrula, 93 ; Pore canals, 

 112. 



Ommatoplea — Nervous system, 147. 



Onchidium — Lung, 339. 



Oniscus — Liver, 275 ; Generative organs, 

 294, 295. 



Onychoteuthis — Suckers, 327. 



Ophidiaster — Generative organs, 225. 



Ophioderma — Generative organs, 224. 



Ophidii — Scales, 418; Centra, 433; Pro- 

 cesses of vertebrae, 433 ; Caudal ver- 

 tebras, 434; Axis, 437; Eibs, 440; 



Squamosal, 458 ; Columella, 458 

 Covering-bones of skull, 459; Vo 

 mer, 459 ; Palato-quadrate, 459 

 Quadrate, 460; Pterygoids, 461; Pala 

 tines, 461 ; Maxilla, 462 ; Hyoid, 472 

 Fore-limb, 481 ; Toes, 489 ; Dermal 

 muscles, 493 ; Intercostal do., 496 

 Masticatory do., 497 ; Brain, 507 

 Optic bulb, 529 ; Ductus endolymph 

 atious, 534; Tympanic cavity, 537 

 Palate, 546 ; Nasal glands, 548 

 Organ of Jacobson, 54S ; Teeth, 550, 

 552 ; Labial glands, 553 ; Stomach, 

 557; Mid.gut, 561; Hind-gut, 562 

 Liver, 564 ; Mesentery, 565 ; Larynx, 

 570 ; Lungs, 573 ; Heart, 581 ; Caro 

 tids, 587 ; Epigastric veins, 595 

 Ovaries, 613 ; Testes, 614 ; Copula, 

 tory organs, 621. 



Ophiothrix— Figure, 202. 



Ophiura — Anus, 199 ; Generative organs, 

 225. 



Ophiurida — Larva, 195; Eays, 196; Anus, 

 199 ; Calcareous skeleton of larva, 

 202 ; Integument, 203 ; Alimentary 

 canal, 212 ; Stone-canal, 222 ; Gener- 

 ative organs, 224. 



Ophrydiae — Anal opening, 85. 



Opilionea — Visceral nerves, 259. 



Opilionida — Eyes, 265 ; Caeca, 270 ; He- 

 patic tbues, 275 ; Malpighian vessels, 

 276 ; Circulatory system, 284 ; Tra- 

 cheae, 291 ; Germinal glands, 297. 



Opisthobranchiata — Shell, 323 ; Tentacles, 

 326; Urticating cells, 329; Ehino- 

 phor, 352 ; Visual organs, 354 ; Jaws, 

 360 ; Salivary glands, 364 ; Heart, 

 371 ; Vessels, 373 ; Circulation in, 

 373 ; Excretory organs, 377 ; Uterus, 

 383. 



Orang — Centrale, 482. 



Orchesella — Ventral chord, 258. 



Oreaster — Arms, 195. 



Ornithorhynchus — Ethmoid, 465 ; Atrio- 

 ventricular valve, 584. 



Ornithoscelidar— Tarsus, 489. 



Orthagoriscus — Spinal chord, 511. 



Orthoceratites— Shell, 332. 



Orthoptera — Thorax, 237 ; Gnathites, 

 245 ; Dermal skeleton, 249 ; Ventral 

 chord, 258; Nervus recurrens, 259; 

 Auditory vesicle, 262 ; Tympanum, 

 262 ; Masticatory stomach, 272; In- 

 gluvies, 272; Mid-gut, 272; Hind- 

 gut, 273 ; Salivary glands, 274, 

 Ovary, 302; Testis, 304; Seminal 

 elements, 305. 



Orycteropus — Uterus, 616. 



Ostracion — Carapace, 424. 



Ostracoda — Appendages, 238 ; Gnathites, 

 239 ; Branchiae, 243 ; Dermal skele- 

 ton, 249 ; Seminal elements, 305. 



Ostrea — Muscles, 343 ; Genital canal, 381. 



Owls — External ear, 538. 



