806 



INDEX 



Nyctiphanes, 554 

 Nyctotherus, 94, 96, 97 

 Nymphon hispidum, 657 



O 



"BELIA, General structure, 129, 130, 

 131 : Microscopic structure, 132, 133 : 

 Medusas, 135, 136, 137 : Comparison 

 of polype with medusa, 137, 138, 139 : 

 Reproduction, 139 : Development, 

 140 : Systematic position, 143 



Occlusor muscle, 342 



Ocelli, 143, 172 



Octopoda, 663, 767*. 768, 769, 770,773, 

 780 



Octopus, 768, 770, 772, 773 



Octorchandra, 150 



Ocular plates, 388, 389 



Odonata, 618 



Odontophore, 702, 707, 708, 709 



(Esophagus See Digestive system 



Oikomonas, 73, 75 



Olfactory organs, 39* 



Olfactory pits, 172* 



Oligochgeta, 455*, 457, 460, 461, 462, 

 463, 464, 466, 467, 468, 469, 470, 

 471, 475, 476, 477 



Olynthus, 117 



Ommatidium, 523*, 524 



Oncidium, 727, 735 



Oniscus, 554, 569, 572 



Onychophora, 515,591*, 661 See Peri- 

 patus 



Ocecium, 334 



Ookinete, 89* 



Oosperm, 23* 



Oostegites, 570* 



Oostegopod, 519* 



Ootype, 239, 240 



Opalina, 95, 100 



Opalinopsis, 96 



Operculum, of Radiolaria, 62*, 64 : 

 Ciliata, 97, 98 : Gastropoda, 704*, 

 705, 720 



Ophioglypha, 411 



Ophiuroidea, 368, 402* : Distinctive 

 characters and classification, 402* : 

 General form and symmetry, 406, 

 407, 408 : System of plates, 409 : 

 Modifications of form, 410, 411, 

 412 : Cnelome, 416 : Ambulacra! 

 system, 417 : Blood-vascular sys- 

 tem, 417, 418 : Haemal system, 

 418 : Axial organ, 419 : Enteric 

 canal, 419 : Nervous system, 420 : 

 Reproductive organs, 420 : De- 

 velopment, 422, 423 : Ethology, 

 &c., 425, 426 



Ophrydium, 97, 99 



Ophryodendron, 102 



Ophryoglena, 96 



Opisthobranchia, 714*, 718, 724, 725, 



735 



Opisthogoneata, 599*, 602, 661 

 Opisthorchis sinensis, 280 

 Optic gland, 750 

 Optic nerve-fibres, 750 

 Optic vesicle, 779 

 Oral arms, 169* 

 Oral surface, 369* 

 Oral tentacles, 151, 413 

 Orchestia, 554, 569, 579 

 Order, 4* 

 Organ of Bojanus, 672* : of Owen, 



758* : of van der Hoeven, 758* : 



of Valenciennes, 759 

 Organic evolution See Evolution 

 Organism, 1* 

 Organ-pipe Coral, 193 

 Organs, 31* 

 Oriental region, 9* 

 Orobdella, 504 

 Orthoceras, 780 



Ortkonectidce, 227, 229, 230, 231 

 Orthoptera, 616*, 621, 624, 625, 637 

 Orthopteroidea, 616* 

 Oscarella, 118 

 Oscaria, 116 

 Oscillatoria, 74 

 Oscular sphincter, 112* 

 Osculum, 107* 



Osphradium, 673*, 674, 712, 774 

 Ossicles, 368* 

 Ostia, 107*, 110, 521 

 Ostium, 186* 

 Ostracoda, 550*. 558, 559, 578, 579, 



581, 582, 586, 587 

 Ostrea, 678, 680, 683, 688, 690, 691 

 Otocyst, 40*, 467, 673, 674, 689 

 Ovariole, 612*, 631 

 Ovary, 40* 

 Ovicella, 345* 

 Oviduct, 40*, 240 

 Oviparous, 40* 

 Ovipositor, 594 

 Ovum, 20*, 21, 31 

 Owen, organ of, 758* 

 Oxeote spicules, 109, 111* 

 Oxygen, oxidation, 36, 37 

 Oxyuris, 302 

 Oysters, 663, 678, 680 



JLACHYCHALINA, 121 



Psedogenesis, 42*, 223*, 632 

 Paqurus, 555, 574 

 Palfearctic region, 9* 

 Palcemon, 555, 573 

 Palcemonetes, 578 

 Palseodietyoptera, 637 

 Palaeontology, 6* 



