of Polychaeta,273Otomesostoma,46,49Otoplana,50Oudemans, on Nemertinea,108Ovary (and Oviduct), ofLeptoplana,11,14,16;of Polyclads,27;ofPlanaria,38,39;of Rhabdocoelida,47;ofTemnocephala,54;of Polystomatidae,57;ofDiplozoon,60;ofGyrodactylus,61;ofDistomum macrostomum,65;ofCalliobothrium,75;ofArchigetes,76;ofSchistocephalus,86;ofRhopalura,95;of Myzostoma,343—see also Reproductive organsOvicell, in Cheilostomata,466,466,468,481,482,484,522f.,525;in Cyclostomata,479,480,521,525Oviduct—see OvaryOwenia,325Ox, parasites of,79,83,125,139,140,143Oxysoma,139,142Oxyuris,129,131,135,139,141,160;O. ambigua,141;O. curvula,141,163;O. diesingi,141,142;O. vermicularis,141,163;O. blattae,O. blatticola,O. hydrophili,O. megatyphlon,O. spirotheca,142Paddle worm,313Paedogenesis,151Pagenstecher, on Nemertinea,99Palaemonetes, host ofNectonema,174Palaeonemertea,109,112;characters,111;development,113Palaeozoic, Serpulidae,301;Eunicidae,302;Polyzoa,520Paleae, ofSabellaria,267Palmicellaria,527,528Palolo viridis, as food,297Palps, ofNereis,248,255;nerves to,254;of Polychaeta,260f.;development of, in Sabelliformia,275;of Hermelliformia,306;of Syllidae,307Paludicella,492,494,501,502,505,518Paludicola,30,42Panthalis,313Paragnaths,248,250,316Parapodium, ofNereis,246,247;of Polychaeta,264f.;of Heteronereid,276,277;muscles of,247;glands of,249,314;ofMyzostoma,342Paraseison,212,225,226Parasitic, Turbellaria,51;Polyclads,22;Triclads,32;Rhabdocoela,45,51;Nemertinea,101,119;Rotifers,204,227;Polychaeta,297;Leeches,406Parasitism, effect on the parasite,161,177;effects on the host,162Parenchyma, inLeptoplana,11,12;of Müller's larva,29;in Triclads,41;in Acoela,42;in Cestodes,85,86Parovaria, ofPhagocata,38n.Parthenogenesis, amongst Rotifers,200Pectinaria,330;body,259;tube,285,287;P. auricoma, tube,288;P. belgica,330Pectinatella,496,497,505,512,518;statoblast,502Pedalion,200,201,206,211,216,223,224,225,228,230Pedalionidae,223Pedetes,224Pedicellina,487,488,490,506,507,518;larva,510,513;budding,514;on Polychaeta,299Pelagic, Nemertinea,101,114;Chaetognatha,189; Rotifera,226;Polychaeta,291,294,314;larvae of Polychaeta,300, of Polyzoa,520Pelagobia,314Pelagonemertes,101,114Pelodera,129,131,133Pelodrilus,369,377Pelodytes,134Penis, ofLeptoplana,14,15;of Polyclads,27;ofPlanaria,38,39;of Rhabdocoelida,47;ofTemnocephala,54;ofCalliobothrium,75;ofSchistocephalus(cirrus-sac),86Pennant, on Hirudinea,406n.Pereyaslawzewa, on Acoela,44n.Pergens, on Polyzoa,500Perichaeta,351,357,358,372,381,381f.,388,394,403Perichaetidae,357,362,380Perienteric, blood-sinus,252Perionyx,381Perissogaster,383Peristome,481,482,522,524Peristomial (tentacular) cirri, ofNereis,248;of Polychaeta,263;nerves to,254Peristomium, ofNereis,248;of Polychaeta,263;of Sabellidae,336Perrier, on Oligochaeta,367,385Petalostoma,422,426,430,447Petromyzon, host ofGordius,173Petta, intestine of,271Phagocata,31,32Phalacrophorus,314Phanerocephala,258,303Pharynx,4;ofLeptoplana,8,9,12,14;of Polyclads,17,24;ofDiscocelis,23;development of, in Polyclads,29,30;of Triclads,31,37,39;ofTemnocephala,53,54;of Polystomatidae,56;of Digenea,62,64;ofNereis,249,250,251;of Polychaeta,269Phascolion,423,425,428Phascolosoma,416,420,423,425,428,447;as host ofLoxosoma,489Philippi, on Hirudinea,406Philodina,208,222,227Philodinidae,222Phoronis,450f.,451,452,453,455;habits,451;anatomy,453f.,457;development,458,458;species,460;affinities,461,512Phosphorescence (and light-producing organs), in Rotifers,226;in Polychaeta,272,295,296;in Oligochaeta,368;in Polyzoa,478Photodrilus,368,383Photogen (light-producing organ), ofPolyophthalmus,272;ofTomopteris,296,315Phreodrilus,369,379Phreoryctes,367,377Phreoryctidae,376Phylactella,528,530Phylactolaemata,476,493f.,518;lophophore,476,495;occurrence,493;movements,494,496f.;reproduction,501,506,507;larva,511,512;distribution,493,504;affinities,512Phyllacanthinae,91Phyllobothrinae,91Phyllobothrium,76n.,91Phyllocotyle,73Phyllodoce,313,314;head,262,263:eggs,275,314n.;colours,291,292;parapodium,264;chaeta,267Phyllodocidae,258,313;parapodial cirri,266;as food,297;eggs,314;colours,292,293Phyllodocites,302Phyllonella,73Phymosoma,413,420,421,423f.,425,426Physaloptera,163Pig, parasites of,68,79,139,147,184Pigments, of Polychaeta,291f.;of Gephyrea,435Pike, Trematode of,62;Cestode of,81,84Pilidium larva,113,113,229,230Pionosyllis,308Piscicola,393,406Pista,328;gill of,329Pits, ciliated, of Polychaeta,272,273Placostegus, colour,292;from deep sea,300Placunella,73Plagiochaeta,358,381,384Plagiostoma,46;British species,50Plagiostomatidae,50Planaria,30,31f.,39;British species,42Planarians,3,7;Dinophilus, compared with,242,243Planariidae,42Planctoplana,19Plankton, Rotifers in,225Planocera,18,19,20Planoceridae,19,23Planorbis, host ofGordius,173Plants, parasites on,154,155,157,160Plasmodium, nature of, in Orthonectids,94Plate, on Rotifers,198,225n.Platyaspis,73Platycotyle,73Platyhelminthes,3f.;Nemertinea classed with,119Plectanocotyle,73Plectus,160Pleionogaster,381Plerocercoid larva,84Plessis, du, onTetrastemma lacustre,101n.,118Pleurocotyle,73Pleurotrocha,224,226Ploesoma,212,225Ploima,202,203,212,213,216,220,223,226,227Plumatella,493,494,499,503-505,518,519;protrusion of polypides,499;statoblasts,499,502,503;larva,512Podal membrane, of Spionidae,322Podaxonia,461Polyarthra,201,224,226Polybostrichus,280Polycelis,30,31,40,42Polychaeta,241,245f.;classification,257,258,303f,;head,248,259f.;parapodium,246,264f.;chaetae,246,266f.;coelomic fluid,252;nervous system,254;sense-organs,255,272;ciliated pits,272;alimentary canal, with pharynx,249,250,251,269,270,271;oesophageal glands,271f.;nephridium,253,254,269,274;genital duct,254,269;genital cells,256,273f.;hermaphrodite,273;regeneration,278,282;habits,285;carnivorous,304;distribution,299;from fresh water,284;from deep sea,300;pelagic,291,314;boring,287;tubes,287;pigments,291;colours,291f.;warning colours,294;protective devices and mimicry,293;phosphorescent,295;food of,296,299;as bait,296,297;as food for man,297;commensalism,297f.;parasitic,297f.;as hosts,299;extinct,301,302;larva,274,276,300;
of Polychaeta,273
Otomesostoma,46,49
Otoplana,50
Oudemans, on Nemertinea,108
Ovary (and Oviduct), ofLeptoplana,11,14,16;
of Polyclads,27;
ofPlanaria,38,39;
of Rhabdocoelida,47;
ofTemnocephala,54;
of Polystomatidae,57;
ofDiplozoon,60;
ofGyrodactylus,61;
ofDistomum macrostomum,65;
ofCalliobothrium,75;
ofArchigetes,76;
ofSchistocephalus,86;
ofRhopalura,95;
of Myzostoma,343—see also Reproductive organs
Ovicell, in Cheilostomata,466,466,468,481,482,484,522f.,525;
in Cyclostomata,479,480,521,525
Oviduct—see Ovary
Owenia,325
Ox, parasites of,79,83,125,139,140,143
Oxysoma,139,142
Oxyuris,129,131,135,139,141,160;
O. ambigua,141;
O. curvula,141,163;
O. diesingi,141,142;
O. vermicularis,141,163;
O. blattae,O. blatticola,O. hydrophili,O. megatyphlon,O. spirotheca,142
Paddle worm,313
Paedogenesis,151
Pagenstecher, on Nemertinea,99
Palaemonetes, host ofNectonema,174
Palaeonemertea,109,112;
characters,111;
development,113
Palaeozoic, Serpulidae,301;
Eunicidae,302;
Polyzoa,520
Paleae, ofSabellaria,267
Palmicellaria,527,528
Palolo viridis, as food,297
Palps, ofNereis,248,255;
nerves to,254;
of Polychaeta,260f.;
development of, in Sabelliformia,275;
of Hermelliformia,306;
of Syllidae,307
Paludicella,492,494,501,502,505,518
Paludicola,30,42
Panthalis,313
Paragnaths,248,250,316
Parapodium, ofNereis,246,247;
of Polychaeta,264f.;
of Heteronereid,276,277;
muscles of,247;
glands of,249,314;
ofMyzostoma,342
Paraseison,212,225,226
Parasitic, Turbellaria,51;
Polyclads,22;
Triclads,32;
Rhabdocoela,45,51;
Nemertinea,101,119;
Rotifers,204,227;
Polychaeta,297;
Leeches,406
Parasitism, effect on the parasite,161,177;
effects on the host,162
Parenchyma, inLeptoplana,11,12;
of Müller's larva,29;
in Triclads,41;
in Acoela,42;
in Cestodes,85,86
Parovaria, ofPhagocata,38n.
Parthenogenesis, amongst Rotifers,200
Pectinaria,330;
body,259;
tube,285,287;
P. auricoma, tube,288;
P. belgica,330
Pectinatella,496,497,505,512,518;
statoblast,502
Pedalion,200,201,206,211,216,223,224,225,228,230
Pedalionidae,223
Pedetes,224
Pedicellina,487,488,490,506,507,518;
larva,510,513;
budding,514;
on Polychaeta,299
Pelagic, Nemertinea,101,114;
Chaetognatha,189; Rotifera,226;
Polychaeta,291,294,314;
larvae of Polychaeta,300, of Polyzoa,520
Pelagobia,314
Pelagonemertes,101,114
Pelodera,129,131,133
Pelodrilus,369,377
Pelodytes,134
Penis, ofLeptoplana,14,15;
of Polyclads,27;
ofPlanaria,38,39;
of Rhabdocoelida,47;
ofTemnocephala,54;
ofCalliobothrium,75;
ofSchistocephalus(cirrus-sac),86
Pennant, on Hirudinea,406n.
Pereyaslawzewa, on Acoela,44n.
Pergens, on Polyzoa,500
Perichaeta,351,357,358,372,381,381f.,388,394,403
Perichaetidae,357,362,380
Perienteric, blood-sinus,252
Perionyx,381
Perissogaster,383
Peristome,481,482,522,524
Peristomial (tentacular) cirri, ofNereis,248;
of Polychaeta,263;
nerves to,254
Peristomium, ofNereis,248;
of Polychaeta,263;
of Sabellidae,336
Perrier, on Oligochaeta,367,385
Petalostoma,422,426,430,447
Petromyzon, host ofGordius,173
Petta, intestine of,271
Phagocata,31,32
Phalacrophorus,314
Phanerocephala,258,303
Pharynx,4;
ofLeptoplana,8,9,12,14;
of Polyclads,17,24;
ofDiscocelis,23;
development of, in Polyclads,29,30;
of Triclads,31,37,39;
ofTemnocephala,53,54;
of Polystomatidae,56;
of Digenea,62,64;
ofNereis,249,250,251;
of Polychaeta,269
Phascolion,423,425,428
Phascolosoma,416,420,423,425,428,447;
as host ofLoxosoma,489
Philippi, on Hirudinea,406
Philodina,208,222,227
Philodinidae,222
Phoronis,450f.,451,452,453,455;
habits,451;
anatomy,453f.,457;
development,458,458;
species,460;
affinities,461,512
Phosphorescence (and light-producing organs), in Rotifers,226;
in Polychaeta,272,295,296;
in Oligochaeta,368;
in Polyzoa,478
Photodrilus,368,383
Photogen (light-producing organ), ofPolyophthalmus,272;
ofTomopteris,296,315
Phreodrilus,369,379
Phreoryctes,367,377
Phreoryctidae,376
Phylactella,528,530
Phylactolaemata,476,493f.,518;
lophophore,476,495;
occurrence,493;
movements,494,496f.;
reproduction,501,506,507;
larva,511,512;
distribution,493,504;
affinities,512
Phyllacanthinae,91
Phyllobothrinae,91
Phyllobothrium,76n.,91
Phyllocotyle,73
Phyllodoce,313,314;
head,262,263:
eggs,275,314n.;
colours,291,292;
parapodium,264;
chaeta,267
Phyllodocidae,258,313;
parapodial cirri,266;
as food,297;
eggs,314;
colours,292,293
Phyllodocites,302
Phyllonella,73
Phymosoma,413,420,421,423f.,425,426
Physaloptera,163
Pig, parasites of,68,79,139,147,184
Pigments, of Polychaeta,291f.;
of Gephyrea,435
Pike, Trematode of,62;
Cestode of,81,84
Pilidium larva,113,113,229,230
Pionosyllis,308
Piscicola,393,406
Pista,328;
gill of,329
Pits, ciliated, of Polychaeta,272,273
Placostegus, colour,292;
from deep sea,300
Placunella,73
Plagiochaeta,358,381,384
Plagiostoma,46;
British species,50
Plagiostomatidae,50
Planaria,30,31f.,39;
British species,42
Planarians,3,7;
Dinophilus, compared with,242,243
Planariidae,42
Planctoplana,19
Plankton, Rotifers in,225
Planocera,18,19,20
Planoceridae,19,23
Planorbis, host ofGordius,173
Plants, parasites on,154,155,157,160
Plasmodium, nature of, in Orthonectids,94
Plate, on Rotifers,198,225n.
Platyaspis,73
Platycotyle,73
Platyhelminthes,3f.;
Nemertinea classed with,119
Plectanocotyle,73
Plectus,160
Pleionogaster,381
Plerocercoid larva,84
Plessis, du, onTetrastemma lacustre,101n.,118
Pleurocotyle,73
Pleurotrocha,224,226
Ploesoma,212,225
Ploima,202,203,212,213,216,220,223,226,227
Plumatella,493,494,499,503-505,518,519;
protrusion of polypides,499;
statoblasts,499,502,503;
larva,512
Podal membrane, of Spionidae,322
Podaxonia,461
Polyarthra,201,224,226
Polybostrichus,280
Polycelis,30,31,40,42
Polychaeta,241,245f.;
classification,257,258,303f,;
head,248,259f.;
parapodium,246,264f.;
chaetae,246,266f.;
coelomic fluid,252;
nervous system,254;
sense-organs,255,272;
ciliated pits,272;
alimentary canal, with pharynx,249,250,251,269,270,271;
oesophageal glands,271f.;
nephridium,253,254,269,274;
genital duct,254,269;
genital cells,256,273f.;
hermaphrodite,273;
regeneration,278,282;
habits,285;
carnivorous,304;
distribution,299;
from fresh water,284;
from deep sea,300;
pelagic,291,314;
boring,287;
tubes,287;
pigments,291;
colours,291f.;
warning colours,294;
protective devices and mimicry,293;
phosphorescent,295;
food of,296,299;
as bait,296,297;
as food for man,297;
commensalism,297f.;
parasitic,297f.;
as hosts,299;
extinct,301,302;
larva,274,276,300;