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J. R. (James Richard) Ainsworth Davis.

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BIOLOGY

UBRARY

G



.



The Natural History
of Animals




CO



DC

o
u



The



Natural History
of Animals



The Animal Life of the World in its various
Aspects and Relations



BY
J. R. AINSWORTH DAVIS, M.A.

TRINITY COLLEGE, CAMBRIDGE

PROFESSOR IN THE UNIVERSITY OF WALES, AND PROFESSOR OF ZOOLOGY AND
GEOLOGY IN UNIVERSITY COLLEGE, ABERYSTWYTH



HALF-VOL. IV



LONDON

THE GRESHAM PUBLISHING COMPANY

34 SOUTHAMPTON STREET, STRAND



1903



BIOLOGY

UBRAPY

G



CONTENTS



HALF-VOL. IV



THE FOOD OF ANIMALS (Continued}

CHAPTER XXIII. THE FOOD OF ANIMALS OMNIVOROUS
ANNELIDS, SIPHON -WORMS, LAMP -SHELLS, MOSS -PO-
LYPES, AND WHEEL-ANIMALCULES

Page

BRISTLE-WORMS (Chaetopoda) Lob-Worm, Tube- Worms (Serpula, Pomatoceros,

Spirorbis), Earth- Worms - - 257

SiPHON-WORMS (Gephyrea) Common Siphon-Worm - 259

LAMP-SHELLS (Brachiopoda) - - - 260

MOSS-POLYPES (Polyzoa) - - - 261

WHEEL- ANIMALCULES (Rotifera) Rose-coloured Rotifer, Crown Rotifer, Flower

Rotifer 261



CHAPTER XXIV. THE FOOD OF ANIMALS OMNIVOROUS
ECHINODERMS, SPONGES, AND ANIMALCULES ANIMALS
WHICH FEED LIKE GREEN PLANTS

HEDGEHOG -SKINNED ANIMALS OR ECHINODERMS (Echinodermata) : Sea-
Urchins (Echinoidea) ; Sea-Cucumbers or Holothurians (Holothuroidea) ;
Crinoids (Crinoidea) Feather-Stars and Sea- Lilies - - 264

SPONGES (Porifera) - 265

ANIMALCULES (Protozoa): Infusoria Ciliata (Slipper Animalcule, Bell Animalcule);
Flagellata (Euglena, Collar Animalcules, Monads) ; Rhizopoda Proteus Ani-
malcule or Amoeba, Foraminifera, Fungus-Animals (Mycetozoa) - 266

ANIMALS WHICH FEED LIKE GREEN PLANTS Animals, Green Plants, and
Colourless Plants (Fungi, &c.) compared as regards Food and Feeding : Leaf-
Green or Chlorophyll Animals which contain Chlorophyll Green Planarian
Worm (Convoluta) ; Green Freshwater Polype, Coral- Polypes; Freshwater
Sponge; Green Animalcules (Berry Animalcule, Vol vox) 270



vi CONTENTS

ANIMAL DEFENCES

CHAPTER XXV. ANIMAL DEFENCES INTRODUCTORY
BODILY CHARACTERISTICS PRODUCING INCONSPICU-
OUSNESS

Page

INTRODUCTORY Different Kinds of Defence against Predaceous Forms. I. PRE-
CAUTIONARY MEASURES: (i) BODILY CHARACTERISTICS resulting in (a)
Inconspicuousness, (b] Conspicuousness : (2) MODE OF LIFE (a) Feeding at
Favourable Times, and (b] Feeding in Favourable Places. II. RESISTANCE:
(A) PASSIVE DEFENCE by: (i) BODILY CHARACTERISTICS such as (a) Un-
palatableness and Indigestibility, (b] Armour: (2) SPECIAL HABITS, e.g. Death-
feigning: (3) FECUNDITY : (B} ACTIVE DEFENCE by means of (i) Ordinary
AGGRESSIVE WEAPONS, (2) Actively DEFENSIVE WEAPONS, (3) CO-OPERA-
TION: III. RETREAT - - 275

INCONSPICUOUSNESS : General Protective Resemblance ; Transparency ; Marine
Surface Animals; Snow Animals Snowy Owl; Desert Animals Camels,
Antelopes, Desert Foxes, Jerboas, Desert Larks, Desert Finches, Sand-Grouse,
Sand-Lizard, Thorn-tailed Lizards, Desert Monitor, Common Skink, Adder,
Horned Viper, Desert Insects; Reversed Shading; Flat Fishes - - - 277

Specialized General Resemblance Corals and Sea-Snails, Corals and Brittle-Stars,

Sponges and Sea-Slugs - - - - - - 285

Protective General Resemblance in Eggs and Young Plovers, Moths, Beetles - 285
Masking Land-Snails, Sea-Snails, Crabs, Sea-Urchins, Sea-Anemones - 287

Variable General Resemblance: Colour-Change in Snow- Animals Variable Hare,
American Hare, Stoat, Weasel, Ptarmigan; Colour-Change in Chameleons;
Colour-Change in Amphibians Common Frog; Colour-Change in Fishes
Plaice, Trout, Lumpsucker; Colour-change in Molluscs Sea-Slugs; Colour-
Change in Crustaceans ^Esop Prawn; Colour- Change in Insects Peppered
Moth, Small Tortoise-shell Butterfly 289

Constant Special Protective Resemblance Sloths, Pangolins; Coot, Moorhen,
Grebes, Young Plovers ; Australian Sea-Horses ; Sea-Slugs ; Stick-Caterpillars,
Leaf-Butterflies, Buff-tip Moth, Stick- and Leaf-Insects; Spiders - - - 294

Variable Special Protective Resemblance Leaf-Butterflies, Caterpillars of Early

Thorn Moth - - 3<*>

CHAPTER XXVI. ANIMAL DEFENCES BODILY CHARAC-
TERISTICS PRODUCING CONSPICUOUSNESS

CONSPICUOUSNESS: Genuine Warning and Spurious Warning (Mimicry) - - 301

Genuine Warning Skunk; Coral Snakes, Cobras, Puff- Adders, Rattlesnakes;
Spotted Salamander, Nicaraguan Frog, Siamese Toad, Horned Toad; Weever-
Fish, Globe-Fishes; Ascidians, Acorn-headed Worms; Sea-Slugs; Wasps,
Hornets, Bees, Black-veined Brown, Magpie Moth, Conspicuous Caterpillars,
Lady-bird ; Spiders ; Bristle-Worms ; Planarian Worms ; Sea- Anemones, Corals,
Jelly-Fishes - 3*

Spurious Warning (Mimicry) Cuckoos, Orioles; American Snakes; Mimicking
Butterflies, White Ermine Moth, Clear-wing Moths, Caterpillars of Lobster-
Moth, Puss-Moth, and Hawk-Moths, Drone-Fly, Mimicking Beetles, Mimicking
Grasshoppers and Crickets, Praying Mantis, Mimicking Plant-Bugs ; Mimick-
ing Spiders - 39



CONTENTS vii



CHAPTER XXVIL ANIMAL DEFENCES SPECIAL
PRECAUTIONARY HABITS

Page

FEEDING AT FAVOURABLE TIMES: Nocturnal Animals Night-Monkeys, Lemurs,
Bats, Elephant, Hoofed Mammals, Gnawing Mammals, Edentates, Marsupials,
Monotremes ; Owl-Parrot, Kiwi ; Geckos ; Amphibians ; Fishes ; Cockroaches,
Crickets, Moths, Fire-Flies; Marine Invertebrates - - 318

Diurnal Animals Herbivorous Mammals, Species exhibiting Warning Colours and

Protective Resemblance - - - - - 323

FEEDING IN SUITABLE PLACES : Species exhibiting Protective Resemblance, Wide

Outlook, Proximity to Retreats - - 3 2 4

Arboreal Animals Evolution of Climbing Forms - - - 325

Parachute Animals and Flying Animals Their Evolution - 327

CHAPTER XXVIIL ANIMAL DEFENCES-PASSIVE DEFENCE

UNPALATABLENESS AND INDIGESTIBILITY Associated with Warning Coloration 332

ARMOURED ANIMALS Armadilloes, Pangolins, Porcupines, Hedgehogs, Spiny
Ant-Eaters ; Feathers and Leg-Scales of Birds ; Armoured Reptiles ; Extinct
Armoured Amphibians, Ribs of Spanish Newt; Armoured Fishes; Shells of
Molluscs; Beetles, Weevils, Caddis- Worms ; Crabs, Rock- Lobster; Sea-Mouse,
Porcupine Worm, .Tube-dwelling Annelids; Skeletons of Moss-Polypes and
Lamp-Shells ; Plates and Spines of Sea-Urchins, Star-Fishes, &c. ; Armoured
Zoophytes Hydroids, Organ-Pipe Coral, Sea-Anemones; Sponge Spicules;
Armoured Animalcules Foraminifera, Radiolaria, &c. 333

ROLLING-UP HABIT Armadilloes, Pangolins, Porcupines, Hedgehogs; Mail-Shells;

Trilobites, Wood-Lice 341

DEATH-FEIGNING HABIT Dingo, Opossums, South American Fox; Tinamous,

Rails ; Lizards and Amphibians ; Spiders ; Beetles - - 342

FECUNDITY OF ILL-DEFENDED ANIMALS Rabbit, Flesh-Fly; Bats as Check to

increase of Oak Procession-Moth 345

CHAPTER XXIX. ANIMAL DEFENCES-ACTIVE DEFENCE

AGGRESSIVE WEAPONS IN DEFENCE - - - 348

ACTIVELY DEFENSIVE WEAPONS : Mammals Teeth of Apes and Monkeys, Use
of Missiles by Baboons, Tusks of Walrus, Elephants, Rhinoceros, Wild Horses,
Teeth of Hippopotamus and Swine, Antlers and Horns of Ruminants, Claws
of Kangaroo, Stink-Glands of Skunk ; Birds and Reptiles Legs of Ostrich and
Emeu, Rooks, Poisonous Lizards ; Poison-Spines of Fishes ; Poisoned Bite of
Cone-Shells, Stinging-Organs of Sea-Slugs, Shells of Tridacna; Stings and
Defensive Glands of Insects; Stink-Glands of Millipedes; Slime-Glands of
Peripatus; Bristles of Bristle- Worms ; Skin-Defences of Planarian Worms;
Poison-Spines of Sea-Urchins ; Stinging Organs of Zoophytes ; Irritant Rodlets
of Higher Animalcules ... - 348

CO-OPERATION AMONG SOCIAL ANIMALS Wild Horses, &c. - 362



viii CONTENTS

CHAPTER XXX. ANIMAL DEFENCES RETREAT

Page

MAMMALS (Mammalia) Monkeys and Baboons, Chamois, Antelopes, Rumination
as facilitating Retreat, Importance of Dwellings and Refuges with reference
to Retreat, Signalling Coloration - - 363

BIRDS (Aves) African Ostrich, Rails, Extinction of Dodo, Flight as a means of

Retreat, Woodpeckers, Diving Birds - 367

REPTILES (Reptilia) Brittle Tails of Lizards, Importance of Cylindrical Shape in

Snakes, &c. - - 370

AMPHIBIANS (Amphibia) Wrestler Frog 371

INVERTEBRATES Ink of Cuttle-Fishes, Detachable Foot-Region of some Land-
Snails, Springing Molluscs, Ants and Bombardier Beetles, Use of Suspensory
Threads (Spiders, Caterpillars, Slugs), Crustaceans, Sacrifice of Part of Body
in Annelids, Possible Origin of Segmentation - - 372

ANIMAL RESPIRATION THE BREATH OF LIFE

CHAPTER XXXI. ANIMAL RESPIRATION GENERAL PRIN-
CIPLESBREATHERS IN WATER AND BREATHERS IN AIR

GENERAL PRINCIPLES Nature of and Necessity for Breathing or Respiration,

Breathing by General Surface, Special Breathing Organs 376

BREATHERS IN WATER AND BREATHERS IN AIR Process essentially the same

in all cases, Relation between Plants and Animals as regards Breathing - - 378

CHAPTER XXXII. ANIMAL RESPIRATION VERTEBRATES
THAT BREATHE IN WATER

Nature and Development of Gill-Clefts, Their possible origin in remote ancestral

forms - - - - - - - - - - 381

FISHES (Pisces) AS BREATHERS IN WATER Nature of Gills, Lampreys and Hags
(Cyclostomata), Sharks and Rays (Elasmobranchii), Sea-Cats (Holocephali),
Ordinary Bony Fishes (Teleostei) 383

PRIMITIVE VERTEBRATES (Protochordata) Lancelet, Ascidians or Tunicates,

Acorn-headed Worms - - - 388

CHAPTER XXXIII. ANIMAL RESPIRATION NEMERTINES
MOLLUSCS WHICH BREATHE IN WATER

NEMERTINE WORMS (NEMERTEA) Some resemblance to Vertebrates - - - 391

MOLLUSCS (Mollusca) Mail-Shells, &c. (Protomollusca); Head-Footed Molluscs
(Cephalopoda) Cuttle-Fish, Pearly Nautilus; Snails and Slugs (Gastropoda)
Ormer, Keyhole Limpet, Whelk and Purple Shell, Common Limpet, John
Knox's Limpet, Sea-Hare, Sea-Lemon, &c. ; Bivalve Molluscs (Lamellibranchia)
Mussels, Cockles, Oysters, &c. - - 391

CHAPTER XXXIV. ANIMAL RESPIRATION JOINTED-LIMBED
ANIMALS WHICH BREATHE IN WATER

CRUSTACEANS (Crustacea) Common Lobster, Freshwater Crayfish, Common
Prawn, Hermit -Crabs, Crabs, Mantis -Shrimps, Sand -Hoppers, Skeleton-



CONTENTS ix

Page

Shrimps, Sea-Slaters, Water Wood-Louse, Mud-Shrimps, Apus, Water-Fleas,
Mussel-Shrimps, Barnacles - - 400

KING-CRABS (Xiphosura) 406

CHAPTER XXXV. ANIMAL RESPIRATION LOWER INVERTE-
BRATES WHICH BREATHE IN WATER

SEGMENTED WORMS (Annelida) Bristle- Worms (Choetopoda) Scale- Worms,

Lugworm, Head-Gills of Tube-Dwellers; Leeches (Discophora) - - - 408

SIPHON-WORMS (Gephyrea) AND WHEEL-ANIMALCULES (Rotifera) - - 410

MOSS-POLYPES (Polyzoa) AND LAMP-SHELLS (Brachiopoda) - - - 410

HEDGEHOG- SKINNED ANIMALS OR ECHINODERMS (Echinodermata) Influence
of the Skeleton on the Development of Breathing Organs, The Relation of the
Water-vascular System to Breathing - 41 1

ZOOPHYTES (Ccelenterata) Breathing by External and Internal Surfaces, Special

Arrangement in some Sea-Anemones 416

SPONGES (Porifera) AND ANIMALCULES (Protozoa) - - - - - 418

CHAPTER XXXVI. ANIMAL RESPIRATION BACKBONED
ANIMALS WHICH BREATHE IN AIR

Nature and Development of Lungs, Aquatic Ancestry of Land Vertebrates - - 420
THE ORIGIN OF LUNGS Swim-Bladder of Fishes Bichir, Lung-Fishes - - 421
AMPHIBIANS (Amphibia) Common Frog, Csecilians, Lungless Amphibians - - 422

REPTILES (Reptilia) Increase in Complexity, Mechanism of Breathing, Crocodiles,

Snakes, Snake-like Lizards, Chameleons 424

BIRDS (Aves) Structure of Lungs, Air-Sacs, Mechanism of Breathing - - - 426

MAMMALS (Mammalia) Structure of Lungs, Mechanism of Breathing, Cetaceans,

Young Pouched Mammals - - - 427

CHAPTER XXXVII. ANIMAL RESPIRATION -BACKBONELESS
ANIMALS WHICH BREATHE IN AIR

MOLLUSCS (Mollusca) Lung-Snails and other Gastropods which breathe in air,

Garden Snail, Black Slug, Pond-Snail, Trumpet-Snail - ... 433

ARTHROPODS (Arthropoda) Peripatus, Origin of Air-tubes - - - 434

CENTIPEDES AND MILLIPEDES (Myriapoda) Shield-bearing Centipede, Imperfect

Development of Blood-System 435

INSECTS (Insecta) Cockroach, Bees and Locusts; Aquatic Air-breathing Insects
Great Water-Beetle, Whirligig Beetles, Great Black Water-Beetle, Pond-
Skaters, Water-Boatmen, Water-Scorpions, Rat-tailed Maggot, Common Gnat 437

ARACHNIDS (Arachnida) Scorpions, Whip-Scorpions, Spiders, Mites - - - 442
CRUSTACEANS (Crustacea) Land-Crabs, Wood- Lice - - 443

LAND NEMERTINES (Nemertea), EARTH-WORMS AND LAND-LEECHES (Annelida),

AND LAND PLANARIANS (Turbellaria) - - - - - - - - 444



x CONTENTS

CHAPTER XXXVIII. ANIMAL RESPIRATION AMPHIBIOUS
VERTEBRATES

Page

FISHES (Pisces) Eel, Carp, Tench, Mud-Skippers, Bleak, Roach, Loach, Snake-
headed Fishes, Climbing Perch; Evolution of the Lungs of Backboned Animals,
Lung-Fishes 447

AMPHIBIANS (Amphibia) Hell-Bender, Giant Salamander, Olm, Siren Salamander;

Common Frog - ... 456

CHAPTER XXXIX. ANIMAL RESPIRATION AMPHIBIOUS
INVERTEBRATES

MOLLUSCS (Mollusca) Origin of Land-Snails and Slugs Periwinkles, Apple-
Snails, &c. - 459

INSECTS (Insecta) Net- Winged Insects (Neuroptera) Stone-Flies, Dragon-Flies,
May-flies, Alder-Flies, Caddis-Flies ; Two-Winged Insects (Diptera) Midges,
Sand-Midges - - 462

CRUSTACEANS (Crustacea) Shore- Crabs, Robber- Crab - 469



LIST OF ILLUSTRATIONS



HALF-VOL. IV



COLOURED PLATES
THE CORAL SNAKE (Elaps Corallinus).

A Study by A. Fairfax Muckley Frontispiece.

PROTECTIVE ANIMAL COLORATION.

A Study by A. Fairfax Muckley

HEAD-FOOTED MOLLUSCS (Cephalopoda) (after Merculiano and Jatta).

A Study by A. Fairfax Muckley



312



392



BLACK-AND-WHITE ILLUSTRATIONS



Page

Group of Serpulae 258

Dissection of Front End of an Earth-Worm 259
Dissection of Siphon-Worm (Sipunculus]

(after Keferstein) 260

Moss-Polypes (after Kraepelin and Boas) - 261
Crown Rotifer (Stephanoceros] - - - 262
Vertical Section of Simple Sponge - - 265
A Proteus Animalcule (Amoeba) surround-
ing a slender Alga (after Rhumbler) - 269
Berry Animalcule (Hczmatococcus pluvialis)

in resting and motile stages - - - 273
Pallas's Sand- Grouse (Syrrhaptes para-

doxits] (from Brehm) .... 280
Eggs of Ringed Plover (sEgialitis hiati-

cula} (from a photograph by R. A. L.

Van Someren) 286

Crouching Young of Peewit ( Vanellus cris-

talus) (from a photograph by R. A. L.

Van Someren) 286

A Beetle (Lithinus nigrocristatus) which

resembles Lichen 287

Upper Side of a Xenophorus Shell (from

Chun) 288

Ptarmigan (Lagopus mutus), in winter

plumage 290

Australian Sea- Horse (Phyllopteryx eques} 296
Caterpillars of Brimstone Moth (Rumia

cratagata) in protective attitudes (after

Poulton) 297

Hinder End of Caterpillar of Brimstone

Moth (after Poulton) .... 297



Page

Indian Leaf Butterfly (Kallima inachis] - 298

American Skunk {Mephitis siiffbcans) - 302

Rattle of Rattlesnake . - - . 304

Horned Toad ( Ceratophrys ornata] - - 305
A Friar -Bird (Philemon Timorlaoensis)

mimicked by an Oriole ( Oriolus decipiens} 310
Caterpillars of the Lobster Moth (Stan-

ropusfagi) - - - - . 314

Heads of Nocturnal Animals - - - 319
Diagram of varieties of Reptilian Armour,

as seen in section (after Boas) - - 333
Nile Crocodile. Two scutes, covered by

horny epidermal plates - 333
Carapace and Plastron of a Tortoise (after

Boulenger) 334

Method of Growth in Gastropod Shells - 335

Growth of Bivalve Shell as seen in section 335

A spiny Sea- Snail (Murex) - - - 336

Opercula of various Gastropods - - 336

Caddis- Worm Tubes of various kinds - 337

The Northern Stone-Crab (Lithodes maia] 338
A Sea-Urchin (Echinus lividus\ showing

protective covering of spines - - 340
Part of Sea-Urchin Test, showing knobs

for attachment of- spines - - - 340
A species of South American Fox (Cants

azarce] 343

THE FALLOW DEER ( Cervtis dama) 350

Horns of Gazelles 353

Poisonous Mexican Lizard (Heloderma

horridum} 355



XI 1



LIST OF ILLUSTRATIONS



Page

Poison Spines of Fishes (after Giinther) - 356
Sting of Bee (after Carlet) - - 358

Poison-Spine of a Sea-Urchin (Astheno-

soma urens) (after P. and F. Sarasin) - 361
Baboons retreating from Wild Dogs (from

Brehm) 364

THE CHAMOIS (Riipicapra Tragus) - 366
The Common Squirrel (Sciurus vulgaris) - 368
The Dodo (Didus ineptus] - - 369

Slug suspended by a Thread of hardened

Slime - - - 374

Front Part of Chick Embryo - - - 381
Californian Hag-Fish (Bdellosloma) - - 383
Diagram of Circulatory System in a Fish - 384
Diagram showing the Gill-Pouches of a

Lamprey (Petromyzon) - - - - 384
Circulatory and Breathing Organs of Hag

(Myxine glntinosa) (after J. Miiller) - 385
Horizontal Section through a Shark, show-
ing the Gill-Pouches) (after Gegenbaur) 386
The Sea-Cat (Chimara monstrosd) (after

Garman) 387

Horizontal Section through the Breathing

Organs of a Teleost (after Gegenbaur) - 388
Lancelet (Amphioxus lanceolatus) (after

Boveri) 389

Section through an Acorn-headed Worm

(Balanoglossus) (after Spengel) - - 390
Mail-Shell (Chiton] - ... 392

Dissection of a Cuttle-Fish (Sepia) to show

Gills (after Savigny) - ... 392
Ormer (Haliotis) dissected to show Gills - 394
Shells of various Sea-Snails (after Lang) - 394
Diagram of a Whelk (J5ucftnufft)(a.ftct Lang) 395
Gill-Cavities of John Knox's Limpet and

Common Limpet 396

Diagram of Sea- Hare (Aplysid) (after Lang) 396
Diagrammatic Cross Section of Hind-

gilled Snail 396

Sea- Lemon (Doris) (after Alder and Han-
cock) - .... 397
Freshwater Mussel (Anodonta) opened to

show Gills 398

Freshwater Mussel (Anodonta) imbedded

in mud 398

Gills of Lobster (Homarus vulgaris)- - 401
Gills of a Crab (after Gegenbaur) - - 404
Gills of Mantis-Shrimp and Sand-Hopper

(after Milne-Edwards and Sars) - - 404
Mud-Shrimp (Nebalia) (after Milne-Edwards) 405
A Mussel-Shrimp (Cypris), enlarged - 406
King-Crab (Limulus) (partly after Ray

Lankester) 406

Scale- Worm (PolynoS) (after Milne-Edwards) 408
Lugworm (Arenicola piscatoruni)^ showing

Gills 409

A Tube-Worm (Terebella), showing Gill-
plumes on Head 409



Page

Priapulus (after Ehlers) .... 4 IO
Mouth-Area of a Sea-Urchin (Echinus

esculentus) (from Kiikenthal)- - - 412
Cross Section through Arm of Star-Fish

(from Kiikenthal) - - - - 413

Heart-Urchin (Spatangus purpureus) 415
Dissection of Sea-Cucumber (after Ludwig,

simplified) 416

Diagrammatic Vertical Section of a Sea-
Anemone 417

Swim-Bladder of Bichir (Polypterus), dia-
grammatic - - - - - - 421

Sections through Lungs, showing Ingrowth
of Folds (after Boas) .... 424

Head of Crocodile to show Breathing

Arrangements (after Boas) - - - 425
Lungs of a Chameleon (after Wiedersheim) 425
Lungs and Air- Sacs of a Bird (after Heider) 426
Convoluted Windpipe of a Crane - - 427
Air- Passages of Lungs of Man - - - 428
Mouth, Nose, &c., of Man, in Section - 429
Lung of Land-Snail (Helix) (after Hatschek

and Cori) 433

Breathing Organs of Shield-bearing Centi-
pede (Scutigera) (after Haase) - - 436
Air-Tubes of Cockroach (Periplaneta ori-

entalis) (after Hatschek and Cori) - - 438
Dissection of Honey-Bee (Apis mellifica]

(after Leuckart) 439

The Drone-Fly (Eristalis tenax) and its

Larva, the Rat-tailed Maggot - - 441
Larva and Pupa of Common Gnat (Culex

pipiens), enlarged .... 442
Mygale (partly dissected) from below - 443
THE MUD-SKIPPER (Periophthalmus Koel-

reuleri) 448

Roach (Leuciscus rutilus) and Bleak

(Alburnus lucidus) - ... 449
Indian Snake-headed Fish (Ophiocephalus) 451
Climbing Perch (Anabas scandens) - - 452
Dissection of a Bitterling (Rhodeus amarus) 452
Roof of Gill-Cavity in a Species of Peri-
winkle (Littorina rudis) (after Pelseneer) 460
Apple-Snail (Ampullaria) (after Semper) - 461
A Stone - Fly (Pteronarcys} (after New-
port) - - - 464
Air-Tubes of Rectal Gills in Dragon-Fly

Nymph (after Oustalet) - - - 465
Nymph of Common May- Fly - - - 465
Hinder Part of Nymph of a May -Fly

(Cloeon dipterum) (after Zimmermann) - 465
Crustacean - like Nymph of a May -Fly

(Prosopistoma) (after Vayssiere) - - 466
Stages in Life-History of a Sand-Midge

(Simulia) (after Verdat) - . 468

Diagrammatic Cross Section through
Breathing Organs of Robber Crab
(Birgus latro) (after Semper) - - 469



CHAPTER XXIII

THE FOOD OF ANIMALS OMNIVOROUS ANNELIDS,
SIPHON-WORMS, LAMP-SHELLS, MOSS-POLYPES,
AND WHEEL-ANIMALCULES



SEGMENTED WORMS (ANNELIDA)

The ANNELIDS include Leeches (Discophora) and Bristle-
Worms (Chaetopoda). The former are carnivorous, and have
already been dealt with (pp. 147-149), and the same is true for
many rapacious marine worms belonging to the latter group, as,
for example, the Sea-Centipede (Nereis] (pp. 146, 147).

OMNIVOROUS BRISTLE- WORMS. These comprise marine, fresh-
water, and terrestrial forms. The marine species include a number
of worms which are entirely devoid of biting structures and burrow
in sand or mud, which they swallow in order to extract the nutri -
tive animal and vegetable matter present. The same habit has
already been described (p. 246) for the Acorn-headed Worm
(Balanoglossus), one of the lowest animals having any claim to
be considered a member of the Vertebrata. A good example
of marine worms which feed in this way is the Lob -Worm
(Arenicola) (see vol. i, p. 430), common on British shores be-
tween tide -marks where mud or mud- containing sand occurs.
This is a good-sized cylindrical form with broad front end, and
may attain a length of some 8 inches. It burrows in the sand
to a depth of about 2 feet, eating its way through, so to speak,
and from time to time comes to the surface for the purpose of
ejecting the sand which has passed through its body. This is
the origin of the little coils of mud or sand known as "worm-
castings " which are commonly seen upon the shore.

A considerable number of marine bristle-worms have given
up an active life and taken to live in tubes of various kinds,
these either consisting entirely of material exuded from the surface
of the body and hardened into horny or shelly substance, or of

VOL. II. 257 49



258



THE FOOD OF ANIMALS



foreign particles, such as sand-grains, glued together by a sticky
secretion. A typical example is afforded by the genus Serpula
(fig. 466), which makes and inhabits calcareous white tubes,
twisted masses of which are often found adhering to rocks,
oyster-shells, &c. It is clear that a tube-dweller like this has to
make special provision for breathing and feeding, and this is here

effected in an interesting manner. On
watching a living Serpula placed in a
vessel of sea-water the head end will
soon be seen to protrude. First of all
a sort of conical stopper (operculum),
which closes and protects the mouth of
the tube, is pushed out, and then follow
two brightly -coloured plume -like out-
growths from the head. These are
covered with cilia, which set up currents
in the surrounding water, as a result of
which breathing is provided for, while
at the same time a constant stream of
edible particles is directed into the mouth.
A common and, when expanded, very
attractive - looking worm (Pomatoceros
triqueter) that abounds on the British
coast, lives in a small wavy tube attached to a stone or other
firm body. One end of the tube tapers to a point, while the
aperture is overhung by a sharp projecting spine from which a
prominent ridge runs backwards. Equally common is a still
smaller tube-worm (Spirorbis], which inhabits a calcareous tube
coiled into a flat spiral, and adhering to brown sea-weeds or other
suitable objects. Other tube-dwellers will be considered when
animal habitations are described.

Great interest attaches to the widely -distributed group of
Earth- Worms, the habits of which, so far as British species are
concerned, were first studied in detail by Darwin, the results
being embodied in his classic work on the subject.

A number of species are native to Britain (a common sort
being Liimbricus herculeus), all of which live in much the same
way. Examination of one of them shows the complete absence
of jaws, and the food chiefly consists of earth which is constantly
swallowed for the sake of the organic matter it contains. An




Fig. 466. Group of Serpulae. Two indi-
viduals are projecting from their tubes



OMNIVOROUS ANNELIDS, &c.



2 59



BUCCAL POUCH



earthworm practically eats its way through the ground, and the
earth which has passed through its body is from time to time
deposited on the surface in the form of "castings", much as in
the case of the Lob- Worm (p. 257). By carefully weighing the
castings deposited on a known area Darwin came to the conclusion
that in many parts of England 10 tons
per acre of soil annually pass through the
bodies of these creatures. Earth-worms
also devour small pieces of vegetable or
animal matter which come in their way.
There are several points of interest in the
structure of the digestive organs (fig. 467).


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