Monostomatidae,73Monostomum,71,73;life-history,72Monostyla,225,226Monotidae,50Monotus,36;British species,50;M. fuscus,45;habits,46Monozoa,91Montgomery, onStichostemma eilhardii,118Monura,225Morren, on Earthworms,347Moseley, on Land Planarians,7,35n.,37;onPelagonemertes,101,114Movements, in Rotifers, etc.,206,235Moxon, on Rotifers,198Mucro,522,525Mucronella,518,522,528,529,530,531Müller, F., on Triclads,37;on Polyzoa,493Müller, O. F., on Turbellaria,6;on Rotifers,197;on Oligochaeta,348,352Müller's larva,16,28,29Muscles, ofLeptoplana,12;of intestine in Polyclads,24;of Nemertinea,102,103;of Nematoda,128;of Gordiidae,165;of Chaetognatha,187;of Rotifers, etc.,206,233,237;ofNereis,247,249f.;of Polyzoa,469,470,472,499,500—see also Body-wallMusculo-glandular organ, in Triclads,39,40Myrianida,280,308;gemmiparity,279,280;markings,293Myrianites,302Mytilia,225,226Myxicola,338;tori uncinigeri,268;eyes,272;otocyst,273;tube,285;supposed mimicry,294Myzostoma, anatomy,342f.;M. cirriferum,343;M. glabrum,342Myzostomaria,241;structure and affinities,342f.Myzostomatidae,342Naidomorpha (= Naididae and Naids),348,352,375f.,377,378,400;chaetae,350,367;reproductive organs,361;asexual reproduction,281,377Nais,348,377;chaetae,350Nannodrilus,382f.Natatory chaetae, of Nereidae,277;of Syllidae,278,307Nathusius, on parasites,63,163Nauphanta,314,315Nebalia, Rotifers parasitic on,225Nectochaeta,291Nectonema agile,164,168,169,173Nemathelminthes,123f.,168Nematobothrium,4,55,71,73Nematoda,123;anatomy,124f.;embryology,135;classification,136;life-history of,159f.Nematogen,94;Secondary Nematogen,94Nematomorpha,123,164f.Nematoxys,139,142,161,163Nematozoa,137Nemertes, British species,110;deposition of ova and spermatozoa in,116Nemertinea, affinities,119;anatomy,102;body-wall,102;breeding,116;cephalic slits and cerebral organs,107,273;circulatory system,106,107;classification,109f.;colour,102;contractility,102;development,113;diagram,104;digestive system,103;excretory system,108,108;external characters,101;food,115;fresh-water forms,101,118;generative organs,109;geographical distribution,117;habitat,100;habits,114;land forms,101,117;locomotion,114,115;nervous system,105,106;parasitic forms,101,119;pelagic forms,101,114;proboscis,100,101f.,103,104,110,115;regeneration,115;sense organs,101,106,107;size,100Nemertodrilus,360Nemertoscolex,444Neodrilus,384Neorhynchidae,184Neorhynchus clavaeceps,178,181,184;N. agilis,184Nephelis,392f.,397,399,401,403,405Nephridium, of Archiannelida,243,244;ofNereis,253;ofArenicola,253,254;of Polychaeta,253;dimorphism of, in Polychaeta,269;thoracic, of Sabelliformia,306;of Terebellidae,327;of Chlorhaemidae,334;ofMyzostoma,344;of Oligochaeta,356f.,381f.,400;of Leeches,399;of Gephyrea—see Brown tubes;ofPhoronis,456Nephthydidae,258,317Nephthys,317;nephridium,254;prostomium,259,260;head,262;tentacles,262;peristomium,263;parapodium,264,265;cirrus,265;gill,268;jaws,270;habitat,286;as bait,297Nereidae,258,315;palps,260;colour,292Nereidiformia,258,303;vascular system,252;anal cirri,259;prostomium,259,260;tentacles,262;peristomial cirri,263;parapodium,264f.;cirri,265;chaetae,266;jaws,269;eyes,272;ciliated organ,273;regeneration in,283;food,296;fossil,301f.Nereilepas,317Nereis,246,299,301,316f.;anatomy,245f.,247f.;transverse section,247;parapodium,246,247,265,317;chaetae,246;head,246,248,316;alimentary canal,249f.,251;jaws,248,250,270,316;nervous system,254,255;eye,255;vascular system,247,251;dorsal ciliated organ,247,254,256;nephridium,253;reproduction,256;sexually mature,276,276f.;sexual dimorphism and Heteroneid phase,276f.;epitokous (= epigamous) and atokous phase,277n.;from fresh water,284;burrow,286;pigment,292;as bait,297;commensalism,298;as host,299;British species,316f.Nereites,302Nerine,299,322;habitat,286;N. vulgaris, head,322Nerve plexus of Nemertinea,103,105Nervous system, ofLeptoplana,13,14;of Polyclads,26,30;ofPlanaria lactea,39;reduced in parasitic Rhabdocoels,45;ofTemnocephala,54;of Polystomatidae,56;of Cestodes,75,86;of Nemertinea,105,106;of Nematoda,127;of Gordiidae,166;of Acanthocephala,177;of Chaetognatha,187;of Rotifera, etc.,215,234,237;of Archiannelida,243,244;of Polychaeta,254;visceral, of Polychaeta,255;of Oligochaeta,353,374;of Gephyrea,416,431,437,440,445;ofPhoronis,456;of Polyzoa,471Neumann, on parasites,164Neuropodium,246,247,264,266,268Newton, on zoo-geographical regions,372Nicolea,328;gill,329Nicomache,332;tail,332;tube,287;N. lumbricalis, colour,292;distribution,299Nitsche, on Polyzoa,475n.,478,500Nitzschia,56,73Norman, on Polyzoa,475Norodonia,492Notamia,518,526Noteus,225Notholca,225,226Notocotyle,73Notomastus,331;chaetae,268Notommata,217,224,226Notommatidae,200,205,207,215,223,224Notophyllum, colour,293Notopodium,246,247,264,265,268Notops,200,224Notopygos,259Nuchal cirri of Eunicidae,318;Nuchal organ—see Ciliated pitsOcnerodrilus,383Octobothrium,56,73Octochaetus,358,384Octocotylinae,73Octotrocha,221Odontosyllis, reproduction of,278;as host,297.Oecistes,205,206,221Oenonites,302Oesophageal glands,271,358Ogmogaster,73Oka, on Hirudinea,399f.;on Polyzoa,500Olfactory pits, in Polyclads,26;in Triclads,36Oligocelis,42Oligochaeta,241,347f.;external characters,348;body-wall,349;chaetae,350,351;branchiae,352;nervous system,353;sense-organs,354;coelom and vascular system,355;excretory organs,356;alimentary canal,358;reproductive organs,360;habitat,365;phosphorescence,368;distribution,369;classification,373;Rotifers parasitic on,227Oligocladus,19,22Oligognathus,297Ollulanus,142;O. tricuspis,144,161Omalostoma,49Onchnesoma,422,423,426,430,447Onchocotyle,73Oncholaimus,157Onchosphaera-larva of Cestodes,87,88Onuphin,290Onuphis,290,318,319;O. conchylega, tube,287Onychochaeta,388;chaeta,351Onyx,131Ootype, inPolystomum,59.Operculum, of Serpulidae,261,276,339;ofSpirorbis, as brood-pouch,261,276;of Cheilostomata,466,477,481,482,522,524Opesia,524Ophelia,299,332;eggs,275;coelomic corpuscles,252Opheliidae,258,331;gill,265;ciliated pits,272Ophiodromus,308;O. flexuosus, parasitic,297Ophryotrocha,310,320;pelagic,291;genital organs,274Opisthotrema,73Opistoma,50Orbigny, D', on Polyzoa,519,520Orifice, of zooecium,466,469,470,524;secondary,522,524Örley, on classification of Nematodes,137Orthonectidae,13,92,94f.Otocyst (and Otolith), of Turbellaria,26;of Nemertinea,106,110;
Monostomatidae,73
Monostomum,71,73;
life-history,72
Monostyla,225,226
Monotidae,50
Monotus,36;
British species,50;
M. fuscus,45;
habits,46
Monozoa,91
Montgomery, onStichostemma eilhardii,118
Monura,225
Morren, on Earthworms,347
Moseley, on Land Planarians,7,35n.,37;
onPelagonemertes,101,114
Movements, in Rotifers, etc.,206,235
Moxon, on Rotifers,198
Mucro,522,525
Mucronella,518,522,528,529,530,531
Müller, F., on Triclads,37;
on Polyzoa,493
Müller, O. F., on Turbellaria,6;
on Rotifers,197;
on Oligochaeta,348,352
Müller's larva,16,28,29
Muscles, ofLeptoplana,12;
of intestine in Polyclads,24;
of Nemertinea,102,103;
of Nematoda,128;
of Gordiidae,165;
of Chaetognatha,187;
of Rotifers, etc.,206,233,237;
ofNereis,247,249f.;
of Polyzoa,469,470,472,499,500—see also Body-wall
Musculo-glandular organ, in Triclads,39,40
Myrianida,280,308;
gemmiparity,279,280;
markings,293
Myrianites,302
Mytilia,225,226
Myxicola,338;
tori uncinigeri,268;
eyes,272;
otocyst,273;
tube,285;
supposed mimicry,294
Myzostoma, anatomy,342f.;
M. cirriferum,343;
M. glabrum,342
Myzostomaria,241;
structure and affinities,342f.
Myzostomatidae,342
Naidomorpha (= Naididae and Naids),348,352,375f.,377,378,400;
chaetae,350,367;
reproductive organs,361;
asexual reproduction,281,377
Nais,348,377;
chaetae,350
Nannodrilus,382f.
Natatory chaetae, of Nereidae,277;
of Syllidae,278,307
Nathusius, on parasites,63,163
Nauphanta,314,315
Nebalia, Rotifers parasitic on,225
Nectochaeta,291
Nectonema agile,164,168,169,173
Nemathelminthes,123f.,168
Nematobothrium,4,55,71,73
Nematoda,123;
anatomy,124f.;
embryology,135;
classification,136;
life-history of,159f.
Nematogen,94;
Secondary Nematogen,94
Nematomorpha,123,164f.
Nematoxys,139,142,161,163
Nematozoa,137
Nemertes, British species,110;
deposition of ova and spermatozoa in,116
Nemertinea, affinities,119;
anatomy,102;
body-wall,102;
breeding,116;
cephalic slits and cerebral organs,107,273;
circulatory system,106,107;
classification,109f.;
colour,102;
contractility,102;
development,113;
diagram,104;
digestive system,103;
excretory system,108,108;
external characters,101;
food,115;
fresh-water forms,101,118;
generative organs,109;
geographical distribution,117;
habitat,100;
habits,114;
land forms,101,117;
locomotion,114,115;
nervous system,105,106;
parasitic forms,101,119;
pelagic forms,101,114;
proboscis,100,101f.,103,104,110,115;
regeneration,115;
sense organs,101,106,107;
size,100
Nemertodrilus,360
Nemertoscolex,444
Neodrilus,384
Neorhynchidae,184
Neorhynchus clavaeceps,178,181,184;
N. agilis,184
Nephelis,392f.,397,399,401,403,405
Nephridium, of Archiannelida,243,244;
ofNereis,253;
ofArenicola,253,254;
of Polychaeta,253;
dimorphism of, in Polychaeta,269;
thoracic, of Sabelliformia,306;
of Terebellidae,327;
of Chlorhaemidae,334;
ofMyzostoma,344;
of Oligochaeta,356f.,381f.,400;
of Leeches,399;
of Gephyrea—see Brown tubes;
ofPhoronis,456
Nephthydidae,258,317
Nephthys,317;
nephridium,254;
prostomium,259,260;
head,262;
tentacles,262;
peristomium,263;
parapodium,264,265;
cirrus,265;
gill,268;
jaws,270;
habitat,286;
as bait,297
Nereidae,258,315;
palps,260;
colour,292
Nereidiformia,258,303;
vascular system,252;
anal cirri,259;
prostomium,259,260;
tentacles,262;
peristomial cirri,263;
parapodium,264f.;
cirri,265;
chaetae,266;
jaws,269;
eyes,272;
ciliated organ,273;
regeneration in,283;
food,296;
fossil,301f.
Nereilepas,317
Nereis,246,299,301,316f.;
anatomy,245f.,247f.;
transverse section,247;
parapodium,246,247,265,317;
chaetae,246;
head,246,248,316;
alimentary canal,249f.,251;
jaws,248,250,270,316;
nervous system,254,255;
eye,255;
vascular system,247,251;
dorsal ciliated organ,247,254,256;
nephridium,253;
reproduction,256;
sexually mature,276,276f.;
sexual dimorphism and Heteroneid phase,276f.;
epitokous (= epigamous) and atokous phase,277n.;
from fresh water,284;
burrow,286;
pigment,292;
as bait,297;
commensalism,298;
as host,299;
British species,316f.
Nereites,302
Nerine,299,322;
habitat,286;
N. vulgaris, head,322
Nerve plexus of Nemertinea,103,105
Nervous system, ofLeptoplana,13,14;
of Polyclads,26,30;
ofPlanaria lactea,39;
reduced in parasitic Rhabdocoels,45;
ofTemnocephala,54;
of Polystomatidae,56;
of Cestodes,75,86;
of Nemertinea,105,106;
of Nematoda,127;
of Gordiidae,166;
of Acanthocephala,177;
of Chaetognatha,187;
of Rotifera, etc.,215,234,237;
of Archiannelida,243,244;
of Polychaeta,254;
visceral, of Polychaeta,255;
of Oligochaeta,353,374;
of Gephyrea,416,431,437,440,445;
ofPhoronis,456;
of Polyzoa,471
Neumann, on parasites,164
Neuropodium,246,247,264,266,268
Newton, on zoo-geographical regions,372
Nicolea,328;
gill,329
Nicomache,332;
tail,332;
tube,287;
N. lumbricalis, colour,292;
distribution,299
Nitsche, on Polyzoa,475n.,478,500
Nitzschia,56,73
Norman, on Polyzoa,475
Norodonia,492
Notamia,518,526
Noteus,225
Notholca,225,226
Notocotyle,73
Notomastus,331;
chaetae,268
Notommata,217,224,226
Notommatidae,200,205,207,215,223,224
Notophyllum, colour,293
Notopodium,246,247,264,265,268
Notops,200,224
Notopygos,259
Nuchal cirri of Eunicidae,318;
Nuchal organ—see Ciliated pits
Ocnerodrilus,383
Octobothrium,56,73
Octochaetus,358,384
Octocotylinae,73
Octotrocha,221
Odontosyllis, reproduction of,278;
as host,297.
Oecistes,205,206,221
Oenonites,302
Oesophageal glands,271,358
Ogmogaster,73
Oka, on Hirudinea,399f.;
on Polyzoa,500
Olfactory pits, in Polyclads,26;
in Triclads,36
Oligocelis,42
Oligochaeta,241,347f.;
external characters,348;
body-wall,349;
chaetae,350,351;
branchiae,352;
nervous system,353;
sense-organs,354;
coelom and vascular system,355;
excretory organs,356;
alimentary canal,358;
reproductive organs,360;
habitat,365;
phosphorescence,368;
distribution,369;
classification,373;
Rotifers parasitic on,227
Oligocladus,19,22
Oligognathus,297
Ollulanus,142;
O. tricuspis,144,161
Omalostoma,49
Onchnesoma,422,423,426,430,447
Onchocotyle,73
Oncholaimus,157
Onchosphaera-larva of Cestodes,87,88
Onuphin,290
Onuphis,290,318,319;
O. conchylega, tube,287
Onychochaeta,388;
chaeta,351
Onyx,131
Ootype, inPolystomum,59.
Operculum, of Serpulidae,261,276,339;
ofSpirorbis, as brood-pouch,261,276;
of Cheilostomata,466,477,481,482,522,524
Opesia,524
Ophelia,299,332;
eggs,275;
coelomic corpuscles,252
Opheliidae,258,331;
gill,265;
ciliated pits,272
Ophiodromus,308;
O. flexuosus, parasitic,297
Ophryotrocha,310,320;
pelagic,291;
genital organs,274
Opisthotrema,73
Opistoma,50
Orbigny, D', on Polyzoa,519,520
Orifice, of zooecium,466,469,470,524;
secondary,522,524
Örley, on classification of Nematodes,137
Orthonectidae,13,92,94f.
Otocyst (and Otolith), of Turbellaria,26;
of Nemertinea,106,110;