448 



Index. 



Onychoteuthidae, 325. 

 Oocysts, 226. 

 Oophylax, 21. 

 Opalina, 68. 

 Opalinsea, 68. 

 Operculum, 225, 285. 

 Opercularia, 68. 

 Ophelia, 221. 

 Ophiacantha, 133. 

 Ophiarachna, 133. 

 Ophiarthrum, 133. 

 Ophidiaster, 187. 

 Ophidromus, 221. 

 Ophioblenna, 133. 

 Ophiocephalus, 163. 

 Ophiocnemis, 133. 

 Ophiocoma, 131. 

 Ophiocominje, 133. 

 Ophiocrinus, 131. 

 Ophiocten, 133. 

 Ophioderma, 133. 

 Ophioderminse, 133. 

 Ophiolepinae, 133. 

 Ophiolepis, 131. 

 Opliiomastix, 131. 

 Ophiom\'xa, 131, 133. 

 Ophiomyxinae, 131. 

 Ophionereinse, 133. 

 Ophiopeza, 133. 

 Ophioscolex, 133. 

 Ophioscolecinse, 133. 

 Ophiostoma, i, 133. 

 Ophiothrix, 134. 

 Ophiura, 133. 

 Ophiuridse, 133. 



Ophiuroides, 127, 131. 



Ophrydidse, 70. 



Ophrydium, 70. 



Ophrj'ocercida;, 71. 



Ophryocerca, 71. 



Ophrj'odendron, 70. 



Ophryoglena, 68, 71. 



Ophr\-oscolecida, 71. 



Ophryoscolex, 71. 



Opilio, 364. 



Opilionidse, 375. 



Opistomum, 161. 



Opisthobranchiata, 280, 304. 



Orbicula, 53, 247. 



Orbis-radulae, 288. 



Orbitelas, 375. 



Orbitolites, 52. 



Orbitoides, 55. 



Orbulina, 54. 



Orbulinidse, 54. 

 Orchestia, 360. 

 Orcula, 153. 

 Order, 38. 

 Oreaster, 137. 

 Organ, 26. 

 Organ system, 10. 

 Organ-pipe coral, 120. 

 Oribates, 365. 

 Oribatidse, 373. 

 Origin of species, 40. 

 Ornithomyia, 419. 

 Orthocerina, 54. 

 Orthocerus, 315. 

 Orthoptera, 403. 

 Orthostomum, 1 6 1. 

 Oscula, 71. 

 Osculina, 73. 

 Osmic acid, 16, 17. 

 Ossification, 18. 

 Osteoblasts, 18. 

 Ostracoda, 348. 

 Ostrseidae, 268. 



Ostraea, 268. 



Otion, 345. 



Otocardia, 255. 



Otocysts, 36, 50, 236, 265, 299. 



Otoliths, 28, 158. 



Ova, 83. 



Ovalbumen, 6. 



Ovary, 34. 



Ovipositors, 396. 



Ovulum, 308. 



Owen, 324, 325. 



Ox bones, 17. 



Oxygen, 7. 



Oxygnatha, 388. 



Oxyrhynchus, 357. 



Oxystomata, 357. 



Oxytricha, 72. 



Oxytrichidse, 72. 



Oxyuris, 180, 185. 



Oxyuridse, 185. 



Oyster, 257, 259, 261, 267. 



Pachymatisma, 77. 

 Pacific Ocean, 45. 

 Pacinian corpuscles, 23. 

 Packard, 396. 

 Pagenstecher, 2, 300. 

 Pagina, 281. 

 Paguridse, 356. 

 Pagurus, 356. 



