INDEX 



683 



Nerve-cord, lormationof, inPhascolosoma, 377 



Nerve-ring, foramtion of, in adult Antedon 

 rosacea, 554 ; in Oucmnaria planci, 542 



Nervous system, formation of, in Agelena, 

 226 ; In embryo (and larva) of Antedoji 

 rosacea, 547; in Astacus, 184; in adult 

 Asterinagibbosa, 477; mlmws. oi Doliolum, 

 637 ; in Donacia, 257, 258 ; in larva of 

 Echinus esaulentus, 516 ; in adult i?cAi?n«s 

 esculentus, 574 ; in Ascidiozooid of Pyro- 

 soma, 640 ; iu Cyathozooid of Pyrosoma, 

 634 ; in Salpa, 635 ; in Scolopendm, 282 ; 

 in larva of Synapta digitata, 536 ; in 

 blastozooid of Uroohorda, 638 



Neural folds in embryo of Amphioxus 

 lanceolatus, 591 ; in Tornaria larva of 

 Balanoglossus, 578 ; in embryo of Cynthia 

 partita, 619 



Neural groove, formation of, in Donacia, 258 



Neural plate, formation of, in embryo of 

 Amphioxus lanceolatus, 541 ; in Tornaria 

 larva of Balanoglosssus, 578 ; in embiyo 

 of Oynthia partita, 614 



Neural tube, formation of, in embryo of 

 Amphioxus lanceolatus, 593 ; in Tornaria 

 larva of Balanoglossus, 578 ; in embryo 

 of Cynthia partita, 619 ; in embryo of 

 Salpa, 636 



Neurenterie canal, formation of, in embryo 

 of Amphioxus lanceolatus, 592 ; in embryo 

 oi Cynthia partita, 619 



Neuroblasts ot Donacia, 258 ; of Nephelis, 161 



Neuropore, formation of, in embryo of 

 Oynthia partita, 619 ; in larva o{ Amphi- 

 oxus lanceolatus, 593 ; in larva of Dis- 

 iaplia, 632 



Nitschia, 506 ; cultures of, 131 



Notochord, formation of, supposed in Actino- 

 trocha larva, 381, 383; in xhnphioxus, 592; 

 in larva of Cynthia partita, 614; in New 

 England Tornaria, 579 



Nuclear sap, definition of, 3 



Nucleolus, definition of, 3 



Nucleus of unripe ovum, 3 



Nucula, 349 



Nymphs of Hemimetabola, 287, 288 



Oceania, 59 ; medusae of, 59 

 Ocelli of Dytiscus, 273, 274, 275 

 Octant of egg of Beriie, definition of, 91 

 Ocular plates of lichinus esculentus, 577 

 Odonata, 245, 272, 277, 286 ; embryonic 



development of, 266 

 Oesophagus, formation of, in Agelena, 235 ; 

 in Antedon rosacea, 550 ; in Astacus, 

 183 ; in larva of Asterias, 462 ; in larva 

 of Balanoglossus clavigerus, 573 ; in larva 

 of Ophiothrix fragilis, 487 ; in larva of 

 Synapta digitata, 532 ; in Terebraiulina 

 septentrionalis, 411 : 



Olfactory organ of Sagitta hipunctata, for- 

 mation of, 434 

 Oligochaeta, 128, 600 ; development of, 

 156-159 



Ommatidium, formation of, in oompoimd eye 

 of Astacus, 189 ; in compound eye of 

 Dytiscus, 276 ; in lateral eyes of Limubis, 

 237 



Onychophora, 169, 206, 285 ; development 

 of, 170-176 



Oocyte of first order, 9 ; definition of, 3 



Oocyte of second order, 9 



Oogenesis, definition of, 2 



Oogonium, definition of, 3 



Oostegites of Entoniscidae, 219 



Oozooid of Botryllidae, 642 ; of Salpa, 640 



Open larva of Patella, formation of, 307 



Operculum of Patella, formation of, 303 



Ophiopluteus larva, 498, 508, 509, 521, 

 529, 532, 533, 565, 654 ; compared with 

 Bipinnaria larva, 491, 492 ; compared with 

 Echinopluteus larva, 511; definition of, 490 



Ophiothrix fragilis, 484, 501, 503, 504, 507, 

 508, 514, 529; abnormal development of, 

 502 ; development of, 485-498 



Ophiura, larva of, 489 



Ophiura bremsinna, 484 ; development of, 

 501-503 



Ophiuroidea, 287, 461, 464, 456, 508, 

 514, 515, 522, 523, 530, 531, 534, 536, 

 538, 541, 542, 543, 560, 564, 565 ; de- 

 velopment of, 484-504 



Opisthobrauchiata, 280, 281, 291, 320, 324 



Optic ganglion, formation of ,m Astacus, 184 



Oral coelom, formation of, in Antedon 

 rosacea, 552 



Oral cone of Aurelia, 69 



Oral lobe of larva of Echinus esculentus, 609 



Oral ring of plates, formation of, in larva of 

 Antedon rosacea, 547 



Oral tentacles of Tubularia, development of, 56 



Organ-forming substances, 658, 659 ; in egg 

 of Oynthia, 631 ; in egg of Dentalinm, 

 330-332 ; in egg of Paludina, 309 



Organogeny, definition of, 27 



Orientation, methods of, 34 



Orthoptera, 201, 245, 272, 277, 278, 286, 288 



Oscarella, 43, 44, 51 ; metamorphosis of, 44 



Osmic acid (Osmium tetroxide), definition of, 

 32 ; use of, 32 



Ostium, formation of, in larva of Aurelia, 71 



Ostium of heart, development of, in Agelena, 

 229 



Ostracoda, 177, 185 ; ancestral origin of, 212 



Ostrea, brephic stage of, 22 



Ostrea virginiana, veliger larva of, 348 



Otocysts, formation of, in Dentalium, 329 ; 

 in Dreissensia, 342 ; in Loligo, 358 ; in 

 Paludina, 315 ; in Patella, 301 ; in 

 Synapta digitata, 539 



Ovary of Ascaris megoJocephala, 438 ; 

 development of, in Julus, 284 ; of 

 Molgula, 628 ; of Phyllodromia, 263 



Oviduct, formation of, in Ascaris megcdo- 

 cephala, 438 ; in Molgula, 628, 629 ; in 

 Phyllodromia, 263 ; in Sagitta bipunctata, 

 454 



Ovum (a) definition of, 2 



