Part 9

Of all Nematodes the most dangerous to man is the small worm which is known as _Trichina spiralis_ (Fig. 18); a series of models are shown which give a good idea of the structure of the female and the smaller male. The young make their way through the walls of the stomach of their host, and encyst themselves among its muscles: a piece of a sternothyroid muscle is shown, taken from a man in whose body it was calculated there were forty millions of encysted _Trichinæ_.

Other Nematodes infesting man, such as _Filaria sanguinis hominis_, are too small for exhibition.

Plants are not free from the attacks of Nematodes, and examples are shown, accompanied by an illustrating figure, of the Ear-cockle gall of wheat; this gall is due to the injuries inflicted by a minute Thread-worm—_Tylenchus tritici_. Wheat is, of course, by no means the only cultivated plant that is attacked by these minute worms; the history of most has, however, still to be made out.

Holding a somewhat uncertain position in relation to the Round-worms are the parasitic _Acanthocephali_ (Thorn-headed Worms) and the free-swimming _Chætognatha_, or Bristle-jawed Worms; examples of both of these groups are shown, together with diagrams illustrative of their general structure.

ANNULATA or Chætopoda.—So-called because consisting of a series of rings, and being provided with chætæ or bristles; they are to be associated with the Arthropoda, under the one head “Appendiculata,” a better name than “Articulata,” since Cuvier did not include worms in his group. The creatures that are most familiarly called worms are to be found in Case III.; here are a few examples of the numerous kinds of worms that are found living freely in the sea, of earth and freshwater Worms, and of Leeches. All these worms are distinctly characterized by the fact that they consist of a number of definite rings (somites), whence they have been called _Annulata_. The marine Worm and the Earthworm differ from the Leech in that these rings are provided with chætæ or bristles, of which there are a number in each bundle in the marine, and a few only in the terrestrial or freshwater form: hence the marine Worms are called _Polychæta_ and the latter _Oligochæta_.

The former are divisible into two great groups. There are those that are free-swimming and are able to forage for themselves, such as the lovely Sea-mouse (_Aphrodite aculeata_), the large _Eunice gigantea_, the common _Nereis pelagica_, or the exquisitely coloured _Chloeia flava_. Others live a more retired life, dwelling in tubes, which they fashion for themselves; they lead either a solitary or a social life. Here we have examples of _Sabella_, _Sabellaria_, _Serpula_; a number of forms of worm-tubes, showing their great variety and beauty (see especially the delicate _Filograna_), are to be seen in the small Table-cases placed against the north wall of the Gallery. Attention should be especially directed to Mr. A. T. Watson’s beautiful preparations of _Terebella littoralis_. We give a figure (Fig. 19) after a drawing by that gentleman of the home of _Panthalis oerstedi_, the tube-forming habits of which have been carefully observed by him.

The _Oligochæta_ are represented by the common Earthworm, the influence of which in the formation of mould and in the general ploughing of the soil was carefully investigated by Mr. Darwin; and by the little _Tubifex rivulorum_ (Bloodworm), which owes both its red colour and its ability to dwell in mud, which is so poor in oxygen as to be unfit for respiration, to the same chemical compound as that which gives the red colour to our blood and carries the oxygen of respiration all over the body.

The _Hirudinea_, or Leeches, are often said to be distinguished from the _Chætopoda_ by the absence of bristles, but, as a fact, _Acanthobdella_ (Figs. 21 and 22) has very well marked bristles. They always have a sucker at the hinder end of the body by which they are attached to their prey; they are found in fresh water (_Piscicola_), on sea-fishes (as _Pontobdella_), or in moist places, as the Leech (_Hirudo_). The last-named has three jaws, armed with as many as ninety denticles. _Trochetia subviridis_ (Land-Leech) is a species which is found rarely and sporadically in England.

The Myzostomaria form a division of Polychæta all the members of which live parasitically on Crinoids, and otherwise present great differences in their habits. Some move about freely on the Crinoids they infest, others are more sluggish and rarely move, others produce galls or cysts on their host, and yet others are internal parasites, and live in the alimentary canal. It is of interest to note that there are corresponding degrees of difference between the young and old specimens of the different groups of species.

The general organisation of Myzostomaria is shown in the accompanying figure (Fig. 23) in which the dorsal wall of the body is supposed to be transparent so as to allow of the chief internal organs being seen.

The last group of Worms here represented is that of the _Gephyrea_; with the advance of our knowledge it is probable that they will be found to be more intimately allied to the _Annulata_ than is now generally supposed; it will be seen indeed that _Echiurus_ has bristles at its hinder end; _Sipunculus_ is the best known representative of the unarmed _Gephyrea_; _Bonellia_ is interesting both from the fact that it owes its green colour to a matter closely resembling the chlorophyll of green plants, and from the possession by the female of a proboscis, which is protruded from the hole in the rock occupied by the worm: the male is very much smaller than the female, and is not nearly so well developed. Owing to the mode of lighting the Gallery, the visitor may have to shift his position several times before gaining a good view of the whole length of the proboscis.

INDEX.

Acanthaster, 114

Acanthobdella, 124

Acanthocephali, 122

Acmæidæ, 9

Actinometra, 113

Adeonidæ, 66

Ætheriidæ, 39

Alcyonidium, 67

Amaroucium, 99

Amathia, 67, 68

Amphineura, 7–9

Ampullariidæ, 14

Ancylus, 27

Annulata, 122

Anodonta, 39

Antedon, 111–113

Aphrodite, 122

Aplacophora, 9

Aplysiidæ, 23

Apoda, 115

Appendiculariidæ, 105

“Apple-Snails”, 14

Architeuthis, 48

Argonauta, 46

Ascaris, 120

Ascidia, 83, 93

Ascidiacea, 90

Ascidiæ Compositæ, 96

Ascidiæ Salpiformes, 99

Ascidiæ Simplices, 90

Ascopodaria, 73

Astartidæ, 38

Asterias, 108, 114

Asterina, 111

Asteroidea, 112, 113

Astrophyton, 114

Atlantidæ, 22

Auger-shells, 21

Auriculidæ, 26

Aviculidæ, 33

Bartlettia, 39

Basket-fish, 114

Basommatophora, 26

Bêche-de-mer, 115

Bipalium, 118

Bird’s head Coralline, 58

Bladder-worm, 117

Blastoidea, 112

Bloodworm, 124

Boat-shells, 20

Boltenia, 91, 92

Bonellia, 126

Borer, 43

Botryllidæ, 96, 97

Botrylloides, 97

Botryllus, 97, 98

Bowerbankia, 67

Brachiopoda, 74–82

Brechites, 44

Bristle-jawed worms, 122

Brittle Stars, 114

Bubble-shells, 23

Buccinidæ, 18, 19

Bugula, 58, 59

Bullidæ, 23

Caberia, 62

Calamaries, 4

Calyptræidæ, 14

Cardiidæ, 40

Carditidæ, 38

Carinariidæ, 22

Carinella, 118

Carrier-shells, 17

Cassididæ, 18, 19

Catenicellidæ, 66

Cavolina, 23

Cellularina, 58

Cephalopoda, 45–50

Cerithiidæ, 17

Cestoda, 116

Cestode parasites, 116

Chætoderma, 9

Chætognatha, 122

Chætopoda, 116, 122

Chama, 41

Chelyosoma, 93

Chilostomata, 57

Chirodota, 115

Chiroteuthis, 47

Chitonidæ, 7, 8

Chloeia, 122

Clams, 41

Clavagellidæ, 44

Clavelina, 94, 95

Clavelinidæ, 94

Clione, 24

Coat-of-mail shells, 7

Cockle, 40

Colella, 97, 98

Comatulidæ, 111

Conchologists, 17

Conidæ, 21

Convoluta, 118

Coralliophilidæ, 20

Corbula, 42

Cowries, 14

Crania, 74, 80

Creeping Coralline, 60

Crepidula, 14

Crinoidea, 112

Crinoids, 109

Crisia, 69

Crisiidæ 69

Cristatella, 71, 72

Cryptochiton, 8

Cryptoplax, 8

Ctenostomata, 57, 66

Cucumaria, 115

Culeolus, 92

Cup-and-saucer Limpets, 14

Currant Squirter, 92

Cuspidariidæ, 45

Cuttlefish, 48

Cyclophoridæ, 13

Cyclostomata, 57, 68

Cynthiidæ, 91

Cypræidæ, 14

Cysticercus, 117

Cystidea, 112

Dentaliidæ, 28

Desert-snail, 6

Diadema, 114

Diazona, 94

Dipsas, 36

Discinidæ, 80

Distoma, 118

Distomidæ, 96

Doliidæ, 18

Doliolidæ, 100, 103

Doliolum, 90, 103

Dracunculus, 121

Dyscolia, 82

Ear-cockle gall, 122

Ear-shells, 12

Earthworms, 124

Echinoderma, 106–115

Echinoidea, 112, 114

Echinometra, 114

Echinozoa, 112

Echiurus, 126

Ectoprocta, 57

Elasipoda, 115

Electra, 62, 63

Elephant-tooth shell, 1

Entoprocta, 57, 73

Escharina, 64

Eulamellibranchia, 38

Eunice, 122

Euthyneura, 23

False Limpets, 9

Fan-Mussel, 34

Fan-Shells, 38

Fasciolariidæ, 18

Feather-star, 111

Filaria, 122

Filibranchia, 32

Filograna, 123

Fissurellidæ, 11

Flat-worms, 116

Flukes, 118, 119

Flustra, 54, 62

Flustrina, 62

Fountain-shell, 17

Fredericella, 71

Freshwater Limpets, 27

Freshwater Mussels, 38

Freshwater Oyster, 39

Freshwater Polyzoa, 70

Freshwater Snails, 7, 26

Freshwater Worms, 122

Gapers, 42

Gastropoda, 9–28

Gephyrea, 126

Giant Clam, 41

Glassy Nautilus, 22

“Glory-of-the-Sea” Cone, 21

Glottidia, 78

Goodsiria, 99

Gordius, 120, 121

Gorgon’s head, 114

Guinea-worm, 121

Gymnolæmata, 57

Gymnosomata, 24

Haliotidæ, 12

Hammer Oyster, 33

Harpidæ, 20

Harp-shells, 20

Helicidæ, 27, 28

Helmet-shells, 18

Hemiaster, 110, 114

Heteropoda, 22

Hippuritidæ, 41

Hirudinea, 124

Hirudo, 124

Holothuria, 107, 115

Holothurioidea, 112, 115

Ianthinidæ, 16

Idmonea, 69

Julinia, 98

Keyhole Limpets, 11

Kinetoskias, 59–61

Kuphus, 43

Lamellibranchia, 29–45

Land-Snails, 26

Larvacea, 104

Leeches, 124

Lepralia, 64

Leptoclinum, 98, 99

Lichenopora, 69

“Lightning-Snake”, 121

Lily-Encrinites, 110

Limidæ, 37

Limnæa truncatula, 118

Limnæidæ, 26

Limpet, 9

Limpet Snails, 26

Linckia, 113, 114

Lineus, 118

Lingula, 74, 75, 77–79

Lithodomus, 33

Littorinidæ, 14

Liver-fluke, 118

Loligo, 46

Lophopus, 71, 72

Lotoriidæ, 18

Loxosoma, 73

Lucinidæ, 38

Lunulites, 64

Mactridæ, 40

Magellania, 75, 77, 82

Magilus, 20

Malleus, 33

Margaritana, 39

Marine worms, 122

Melaniidæ, 17

Meleagrina, 33–35

Melons, 20

Membranipora, 63

Mermis, 120

Metacrinus, 113

Mineralogists, 17

Mitridæ, 18

Molgula, 91

Molgulidæ, 90

Mollusca, 1–53

Money-Cowry, 15

Moss Animals, 56

Mucronella, 65

Mülleria, 39, 40

Muricidæ, 20

Mussels, 33

Mussels (freshwater), 38

Myidæ, 42

Mytilidæ, 33

Myzostomaria, 125

Naked-gilled Molluscs, 24

Natica, 15

Nautilus, 45, 49

Nematoidea, 116, 120

Nemertinea, 116, 118, 120

Neomenia, 9

Nereis, 122

Neritidæ, 13

Non-parasitic Worms, 118

Nucleobranchiata, 22

Nuculidæ, 31

Nudibranchia, 23, 24

Octacnemidæ, 100

Octopus, 46, 47

Oikopleura, 104

Oligochæta, 122, 124

Olividæ, 20

Ophiacantha, 111

Ophiuroidea, 112, 114

Opisthobranchia, 23

Orange Cowry, 15

Oreaster, 114

Ormers, 12

Ostreidæ, 36

Ovulidæ, 15

Oyster, 36

Panthalis, 123

Paper-Nautilus, 46

Patella, 9

Pearl-Oyster, 33

Pearly Nautilus, 50

Pectinibranchia, 13

Pectinidæ, 38

Pedata, 115

Pedicellinidæ, 73

Pelmatozoa, 111

Pentacrinus, 111, 113

Periwinkle, 14

Perophora, 95, 96

Phallusia, 93

Pharyngodictyon, 98, 99

Pholas, 43

Phylactolæmata, 70

Piddocks, 43

Pinna, 33, 34

Piscicola, 124

Planaria, 118

Platyhelmia, 116

Pleurotomaria, 11

Pleurotomatidæ, 20

Plumatella, 71, 72

Polychæta, 122

Polyclinidæ, 96

Polyplacophora, 7

Polyzoa, 54–73

Pond-Mussel, 5

Pond-Snails, 27

Pontobdella, 124

Poromyidæ, 45

Poulp, 7

Proneomenia, 7

Protobranchia, 31

Pseudolamellibranchia, 33

Psolus, 115

Pterocera, 18

Pteropoda, 23

Pterotracheidæ, 22

Pulmonata, 25–28

Purpura, 20

Pyrosoma, 90, 99

Radiolitidæ, 41

Razor-shells, 42

Retepora, 65, 66

Rhodosoma, 93, 94

Rhopalæa, 96

Rhynchonella, 82

River-Snails, 13

Rock-shells, 20

Round Worms, 118

Sabella, 122

Sabellaria, 122

Saddle-Oysters, 32

Salpa, 90, 100–103

Salpidæ, 100

Scala, 17

Scallops, 38

Scaphopoda, 28

Schizoporella, 65

Scorpion-shells, 18

Screw-shells, 17

Scrobiculariidæ, 40

Scrupocellaria, 60, 62

Scutibranchia, 9

Sea-Butterflies, 23

Sea-Cucumbers, 106, 115

Sea-Hare, 23, 24

Sea-Lilies, 106

Sea-Mat, 54

Sea-Mouse, 122

Sea-Slugs, 106

Sea-Urchins, 106, 114

Sea-Woodlice, 7

Selenariidae, 64

Semele, 40

Sepia, 46–48

Sepiola, 46

Septibranchia, 45

Serpula, 122

Ship-worm, 43

Silk Coralline, 68

Siphonariidæ, 26

Sipunculus, 126

Slipper-Limpets, 14

Slit-Limpets, 11

Slugs, 28

Snails, 27

Solenidæ, 42

Solenomyidæ, 31

Spatangus, 109

Spirula, 49

Spondylidæ, 37

Squid, 46

Stalked Crinoids, 110, 112

Starfishes, 108

Stichopus, 107

Streptoneura, 9

Strombidæ, 17

Strongylus, 120

Styelopsis, 92

Stylommatophora, 27

Synapta, 107, 115

Tænia, 116, 117

Tapeworm, 116

Tectibranchia, 23

Tellina, 40

Terebella, 123

Terebratula, 74, 82

Terebratulina, 82

Terebridæ, 21

Teredo, 43, 44

Testacella, 28

Tethys, 24

Thaliacea, 100

Thecalia, 38

Thecidium, 81

Thecosomata, 23

Thorn-headed Worms, 122

Thorny Oysters, 37

Thread-worms, 118

Thysanozoon, 118

Tooth-shells, 28

Top-shells, 12

Trematoda, 116

Trepang, 115

Trichina, 121

Trichocephalus, 120

Tridacnidæ, 41

Trochetia, 125

Trochidæ, 12

Trumpet-shells, 18

Tubifex, 124

Tubulipora, 69, 70

Tunicata, 83–105

Tun-shells, 18

Turbellaria, 116, 118, 120

Turbinidæ, 12

Turritellidæ, 17

Tylenchus, 122

Umbraculidæ, 23, 24

Umbraculum, 24, 25

Umbrella-shells, 23

Unionidæ, 38, 39

Veneridæ, 40

Venus-shells, 30

Vermetidæ, 17

Vesicularia, 67

Violet Snails, 16

Viviparidæ, 20

“Volutes”, 20

Volutidæ, 20

Water-Clams, 37

Watering pot-shells, 44

Water Spondyli, 37

Weaver’s-shuttle, 15

Whelk, 18

Window-shells, 32

Wing-shells, 33

Winkles, 14

Worms, 116–126

Worm-shells, 17

Worm-tubes, 123

Xenophoridæ, 17

LONDON: PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, STAMFORD STREET AND CHARING CROSS.

Footnote 1:

A framed series of photographs, illustrating different kinds of radulæ, is placed on the east wall of the gallery.

Footnote 2:

From Woodward’s ‘Manual of the Mollusca,’ published by Lockwood & Son.

Footnote 3:

From ‘The Cambridge Natural History,’ Messrs. Macmillan & Co.

Footnote 4:

From the Greek: _pteron_, wing, and _pous_, foot.

Footnote 5:

From the Greek: _scaphe_, a small boat, and _pous_, a foot—the foot of some Scaphopods being somewhat pointed like the prow of a vessel.

Footnote 6:

The term Lamellibranchia is used instead of Pelecypoda in deference to the wish of Professor Lankester.—E. A. S.

Footnote 7:

From the ‘Encyclopædia Britannica.’ Messrs. A. & C. Black.

Footnote 8:

From ‘The Cambridge Natural History.’ Messrs. Macmillan & Co.

Footnote 9:

From the Greek: _kephale_, head, and _pous_, foot.

Footnote 10:

_Zoon_, animal; _oikos_, house.

Footnote 11:

_Lophos_, plume; _pherein_, to bear.

Footnote 12:

_Polus_, many; _zoon_, animal.

Footnote 13:

_Bryon_, moss.

Footnote 14:

_Ektos_, outside; _proktos_, vent.

Footnote 15:

_Cheilos_, lip; _stoma_, mouth.

Footnote 16:

_Gumnos_, naked; _laimos_, throat.

Footnote 17:

_Ktenos_, of a comb.

Footnote 18:

_Phulassein_, to guard; _laimos_, throat.

Footnote 19:

_Kuklos_, circle.

Footnote 20:

_Entos_, inside; _proktos_, vent.

Footnote 21:

_Vibraculum_, a bristle.

Footnote 22:

_Pyrosoma_—_pur_, fire; _soma_, body.

Footnote 23:

It should be mentioned that one high authority, Prof. W. K. Brooks, does not regard the life history of _Salpa_ as an example of alternation of generations, but considers the solitary _Salpa_ to be, not asexual, but a female which produces a chain of males; but it is impossible to enter into a difficult question of controversy here.

Footnote 24:

From the Greek _pelma_ = a stalk.

Footnote 25:

The Asteroidea or Ophiuroidea may be counted under the name Stelliformia.

TRANSCRIBER’S NOTES

1. Typos fixed; non-standard spelling and dialect retained. 2. Used numbers for footnotes, placing them all at the end of the last chapter. 3. Enclosed italics font in _underscores_. 4. Enclosed bold font in =equals=. 5. The caret (^) serves as a superscript indicator, applicable to individual characters (like 2^d) and even entire phrases (like 1^{st}).