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diff --git a/42978-0.txt b/42978-0.txt index df65b4a..447aa4c 100644 --- a/42978-0.txt +++ b/42978-0.txt @@ -1,36 +1,4 @@ -The Project Gutenberg EBook of The Sea Shore, by William S. Furneaux - -This eBook is for the use of anyone anywhere at no cost and with -almost no restrictions whatsoever. You may copy it, give it away or -re-use it under the terms of the Project Gutenberg License included -with this eBook or online at www.gutenberg.org - - -Title: The Sea Shore - -Author: William S. 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You may copy it, give it away or -re-use it under the terms of the Project Gutenberg License included -with this eBook or online at www.gutenberg.org - - -Title: The Sea Shore - -Author: William S. Furneaux - -Illustrator: Robert Lillie - -Release Date: June 18, 2013 [EBook #42978] - -Language: English - -Character set encoding: ISO-8859-1 - -*** START OF THIS PROJECT GUTENBERG EBOOK THE SEA SHORE *** - - - - -Produced by KD Weeks, Chris Curnow and the Online -Distributed Proofreading Team at http://www.pgdp.net (This -file was produced from images generously made available -by The Internet Archive) - - - - - -Transcriber's Note - -Due to limitations of this format, some typographical features are not -possible. Italic and bold text is represented in this text as _italic_ -and =bold=. The 'oe' ligature is rendered with 'oe' as separate -characters. Finally, the few superscripted characters are given in-line, -e.g. 'Ltd' or A1. - -The colored plates and other illustrations cannot be given here. The -approximate positions of each, including any caption text, is shown -as [Illustration: caption]. Those which are shown in the middle of -paragraphs are positioned at the nearest paragraph break. - -Please consult the detailed note at the end of this text for any -corrections made, and for any other observations about the text. - - - - - THE SEA SHORE - - - - - +--------------------------------------------------------------+ - | THE OUT-DOOR WORLD SERIES. | - | | - | THE OUT-DOOR WORLD; or, the Young Collector's Handbook. | - | By W. S. FURNEAUX. With 18 Plates (16 of which are | - | Coloured), and 549 Illustrations in the Text. Crown | - | 8vo, 6s. 6d. net. | - | | - | FIELD AND WOODLAND PLANTS. | - | By W. S. FURNEAUX. With 8 Plates in Colour, and numerous | - | other Illustrations by PATTEN WILSON, and from | - | Photographs. Crown 8vo, 6s. 6d. net. | - | | - | BRITISH BUTTERFLIES AND MOTHS. | - | By W. S. FURNEAUX. With 12 Coloured Plates and 241 | - | Illustrations in the Text. Crown 8vo, 6s. 6d. net. | - | | - | LIFE IN PONDS AND STREAMS. | - | By W. S. FURNEAUX. With 8 Coloured Plates and 331 | - | Illustrations in the Text. Crown 8vo, 6s. 6d. net. | - | | - | THE SEA SHORE. By W. S. FURNEAUX. | - | With 8 Coloured Plates and over 300 Illustrations in the | - | Text. Crown 8vo, 6s. 6d. net. | - | | - | BRITISH BIRDS. By W. H. HUDSON. | - | With a Chapter on Structure and Classification by FRANK E. | - | BEDDARD, F.R.S. With 16 Plates (8 of which are Coloured), | - | and 103 Illustrations in the Text. Crown 8vo, 6s. 6d. net. | - | | - | LONGMANS, GREEN & CO., 39 Paternoster Row, London, E.C.4 | - | New York, Toronto, Bombay, Calcutta and Madras. | - +--------------------------------------------------------------+ - - - [Illustration: Plate I, A ROCK-POOL] - - - - - THE SEA SHORE - - BY - - W. S. FURNEAUX - - AUTHOR OF - - 'THE OUTDOOR WORLD' 'BRITISH BUTTERFLIES AND MOTHS' - 'LIFE IN PONDS AND STREAMS' ETC. - - [Illustration] - - _WITH EIGHT PLATES IN COLOUR_ - _AND OVER THREE HUNDRED ILLUSTRATIONS IN THE TEXT_ - - _NEW IMPRESSION_ - - LONGMANS, GREEN AND CO. - 39 PATERNOSTER ROW, LONDON, E.C.4 - NEW YORK, TORONTO - BOMBAY, CALCUTTA AND MADRAS - - 1922 - - All rights reserved - - - - - +------------------------------------------------+ - | BIBLIOGRAPHICAL NOTE. | - | | - | _First published in September, 1903._ | - | | - | _Re-issue at Cheaper Price, July, 1911._ | - | | - | _New Impression, November, 1922._ | - | | - | | - | _Made in Great Britain_ | - | | - +------------------------------------------------+ - - - - - PREFACE - - -To sea-side naturalists it must be a matter of great surprise that of -the inhabitants of our coast towns and villages, and of the -pleasure-seekers that swarm on various parts of the coast during the -holiday season, so few take a real interest in the natural history of -the shore. The tide flows and ebbs and the restless waves incessantly -roll on the beach without arousing a thought as to the nature and cause -of their movements. The beach itself teems with peculiar forms of life -that are scarcely noticed except when they disturb the peace of the -resting visitor. The charming vegetation of the tranquil rock-pool -receives but a passing glance, and the little world of busy creatures -that people it are scarcely observed; while the wonderful forms of life -that inhabit the sheltered nooks of the rugged rocks between the -tide-marks are almost entirely unknown except to the comparatively few -students of Nature. So general is this apparent lack of interest in the -things of the shore that he who delights in the study of littoral life -and scenes but seldom meets with a kindred spirit while following his -pursuits, even though the crowded beach of a popular resort be situated -in the immediate neighbourhood of his hunting ground. The sea-side -cottager is too accustomed to the shore to suppose that he has anything -to learn concerning it, and this familiarity leads, if not to contempt, -most certainly to a disinclination to observe closely; and the visitor -from town often considers himself to be too much in need of his -hard-earned rest to undertake anything that may seem to require energy -of either mind or body. - -Let both, however, cast aside any predisposition to look upon the -naturalist's employment as arduous and toilsome, and make up their minds -to look enquiringly into the living world around them, and they will -soon find that they are led onward from the study of one object to -another, the employment becoming more and more fascinating as they -proceed. - -Our aim in writing the following pages is to encourage the observation -of the nature and life of the sea shore; to give such assistance to the -beginner as will show him where the most interesting objects are to be -found, and how he should set to work to obtain them. Practical hints are -also furnished to enable the reader to successfully establish and -maintain a salt-water aquarium for the observation of marine life at -home, and to preserve various marine objects for the purpose of forming -a study-collection of the common objects of the shore. - -To have given a detailed description of all such objects would have been -impossible in a work of this size, but a large number have been -described and figured, and the broad principles of the classification of -marine animals and plants have been given such prominence that, it is -hoped, even the younger readers will find but little difficulty in -determining the approximate positions, in the scale of life, of the -various living things that come within their reach. - -Of the many illustrations, which must necessarily greatly assist the -reader in understanding the structure of the selected types and in the -identification of the different species, a large number have been -prepared especially for this work. - - - - - CONTENTS - - - CHAPTER PAGE - - I. THE GENERAL CHARACTERISTICS OF THE SEA SHORE 1 - - II. THE SEA-SIDE NATURALIST 21 - - III. SEA ANGLING 34 - - IV. THE MARINE AQUARIUM 51 - - V. THE PRESERVATION OF MARINE OBJECTS 71 - - VI. EXAMINATION OF MARINE OBJECTS--DISSECTION 91 - - VII. THE PROTOZOA OF THE SEA SHORE 102 - - VIII. BRITISH SPONGES 115 - - IX. THE COELENTERATES--JELLY-FISHES, ANEMONES, AND - THEIR ALLIES 127 - - X. STARFISHES, SEA URCHINS, ETC. 157 - - XI. MARINE WORMS 172 - - XII. MARINE MOLLUSCS 190 - - XIII. MARINE ARTHROPODS 256 - - XIV. MARINE VERTEBRATES 306 - - XV. SEA WEEDS 343 - - XVI. THE FLOWERING PLANTS OF THE SEA-SIDE 391 - - INDEX 425 - - - - - - LIST OF COLOURED PLATES - - _Drawn by_ MR. ROBERT LILLIE _and reproduced by_ - MESSRS. ANDRÉ & SLEIGH, LTD., _Bushey_. - - - - PLATE I--_A ROCK-POOL_ _Frontispiece_ - - PLATE II--_SEA ANEMONES_ _To face p. 142_ - - 1, 2, 3. _Actinia mesembryanthemum._ - 4. _Caryophyllia Smithii._ - 5. _Tealia crassicornis._ - 6. _Sagartia bellis._ - 7. _Balanophyllia regia._ - 8. _Actinoloba dianthus._ - - PLATE III--_SEA ANEMONES_ _To face p. 150_ - - 1. _Sagartia troglodytes._ - 2. " _venusta._ - 3. _Actinia glauca._ - 4. " _chiococca._ - 5. _Bunodes Ballii._ - 6. " _gemmacea._ - 7. _Anthea cereus._ - 8. _Sagartia rosea._ - - PLATE IV--_ECHINODERMS_ _To face p. 168_ - - 1. _Asterias rubens._ - 2. _Goniaster equestris._ - 3. _Ophiothrix fragilis._ - 4. _Echinocardium cordatum._ - 5. _Echinus miliaris._ - 6. " _esculentus._ - - PLATE V--_MOLLUSCS_ _To face p. 222_ - - 1. _Solen ensis._ - 2. _Trivia europæa._ - 3. _Trochus umbilicatus._ - 4. " _magnus._ - 5. _Littorina littorea._ - 6. " _rudis._ - 7. _Haminea_ (_Bulla_) _hydatis_. - 8. _Tellina._ - 9. _Capulus_ (_Pileopsis_) _hungaricus_. - 10. _Chrysodomus_ (_Fusus_) _antiquus_. - 11. _Buccinum undatum._ - 12, 13. _Scalaria communis._ - 14. _Pecten opercularis._ - 15. " _varius._ - 16. " _maximus._ - - PLATE VI--_CRUSTACEA._ _To face p. 290_ - - 1. _Gonoplax angulata._ - 2. _Xantho florida._ - 3. _Portunus puber._ - 4. _Polybius Henslowii._ - 5. _Porcellana platycheles._ - - PLATE VII--_SEAWEEDS_ _To face p. 354_ - - 1. _Fucus nodosus._ - 2. _Nitophyllum laceratum._ - 3. _Codium tomentosum._ - 4. _Padina pavonia._ - 5. _Porphyra laciniata_ (_vulgaris_). - - PLATE VIII--_SEAWEEDS_ _To face p. 384_ - - 1. _Chorda filum._ - 2. _Fucus vesiculosus._ - 3. " _canaliculatus._ - 4. _Delesseria (_Maugeria_) sanguinea_. - 5. _Rhodymenia palmata._ - 6. _Chondrus crispus._ - 7. _Ulva lactuca._ - - - - - OTHER ILLUSTRATIONS - - FIG. PAGE - - 1. CHALK CLIFF 3 - - 2. WHITECLIFF (CHALK), DORSET 4 - - 3. PENLEE POINT, CORNWALL 5 - - 4. BALANUS SHELLS 6 - - 5. A CLUSTER OF MUSSELS 7 - - 6. BREAKERS 8 - - 7. ILLUSTRATING THE TIDE-PRODUCING INFLUENCE OF THE MOON 10 - - 8. ILLUSTRATING THE TIDES 11 - - 9. SPRING TIDES AT FULL MOON 12 - - 10. SPRING TIDES AT NEW MOON 12 - - 11. NEAP TIDES 13 - - 12. CHART SHOWING THE RELATIVE TIMES OF HIGH TIDE ON DIFFERENT - PARTS OF THE BRITISH COAST 16 - - 13. THE VASCULUM 22 - - 14. WIRE RING FOR NET 24 - - 15. NET FRAME WITH CURVED POINT 24 - - 16. RHOMBOIDAL FRAME FOR NET 24 - - 17. RHOMBOIDAL NET 25 - - 18. SEMICIRCULAR NET 25 - - 19. THE DREDGE 25 - - 20. THE CRAB-POT 26 - - 21. AN OLD BIRD-CAGE USED AS A CRAB-POT 27 - - 22. A YOUNG NATURALIST AT WORK 32 - - 23. A GOOD HUNTING-GROUND ON THE CORNISH COAST 33 - - 24. ROUND BEND HOOK WITH FLATTENED END 37 - - 25. LIMERICK HOOK, EYED 37 - - 26. METHOD OF ATTACHING SNOOD TO FLATTENED HOOK 38 - - 27. METHOD OF ATTACHING SNOOD TO EYED HOOK 38 - - 28. THE LUGWORM 39 - - 29. THE RAGWORM 40 - - 30. DIGGING FOR BAIT 41 - - 31. METHOD OF OPENING A MUSSEL 42 - - 32. FISHING FROM THE ROCKS 46 - - 33. THE PATERNOSTER 48 - - 34. SECTION OF AN AQUARIUM CONSTRUCTED WITH A MIXTURE OF - CEMENT AND SAND 54 - - 35. CEMENT AQUARIUM WITH A GLASS PLATE IN FRONT 55 - - 36. AQUARIUM OF WOOD WITH GLASS FRONT 56 - - 37. HEXAGONAL AQUARIUM CONSTRUCTED OF ANGLE ZINC, WITH - GLASS SIDES 57 - - 38. METHOD OF AERATING THE WATER OF AN AQUARIUM 65 - - 39. AQUARIUM FITTED WITH APPARATUS FOR PERIODIC - OUTFLOW 67 - - 40. JARS FOR PRESERVING ANATOMICAL AND BIOLOGICAL SPECIMENS 76 - - 41. SHOWING THE DIFFERENT STAGES IN THE MAKING OF A SMALL - SPECIMEN TUBE 77 - - 42. SMALL SPECIMEN TUBE MOUNTED ON A CARD 78 - - 43. SMALL CRAB MOUNTED ON A CARD 82 - - 44. SPRING FOR HOLDING TOGETHER SMALL BIVALVE SHELLS 84 - - 45. THE TRIPLET MAGNIFIER 92 - - 46. A SMALL DISSECTING TROUGH 93 - - 47. CELL FOR SMALL LIVING OBJECTS 95 - - 48. SHEET OF CORK ON THIN SHEET LEAD 99 - - 49. WEIGHTED CORK FOR DISSECTING TROUGH 99 - - 50. THE AMOEBA, HIGHLY MAGNIFIED 102 - - 51. " " SHOWING CHANGES OF FORM 103 - - 52. " " FEEDING 103 - - 53. " " DIVIDING 104 - - 54. A GROUP OF FORAMINIFERS, MAGNIFIED 105 - - 55. A SPIRAL FORAMINIFER SHELL 106 - - 56. A FORAMINIFER OUT OF ITS SHELL 106 - - 57. THE SAME FORAMINIFER (FIG. 56) AS SEEN WHEN ALIVE 107 - - 58. SECTION OF THE SHELL OF A COMPOUND FORAMINIFER 107 - - 59. SECTION OF A NUMMULITE SHELL 108 - - 60. _Globigerina bulloides_, AS SEEN WHEN ALIVE, MAGNIFIED 108 - - 61. SECTION OF A PIECE OF NUMMULITIC LIMESTONE 109 - - 62. A GROUP OF RADIOLARIAN SHELLS, MAGNIFIED 111 - - 63. THREE INFUSORIANS, MAGNIFIED 113 - - 64. A PHOSPHORESCENT MARINE INFUSORIAN (_Noctiluca_), - MAGNIFIED 114 - - 65. SECTION OF A SIMPLE SPONGE 116 - - 66. DIAGRAMMATIC SECTION OF A PORTION OF A COMPLEX SPONGE 117 - - 67. HORNY NETWORK OF A SPONGE, MAGNIFIED 118 - - 68. _Grantia compressa_ 120 - - 69. SPICULES OF _Grantia_, MAGNIFIED 120 - - 70. _Sycon ciliatum_ 121 - - 71. _Leucosolenia botryoides_, WITH PORTION MAGNIFIED 121 - - 72. _Chalina oculata_ 122 - - 73. _Halichondria panicea_ 123 - - 74. SPICULES OF _Halichondria_, MAGNIFIED 124 - - 75. AN OYSTER SHELL, BORED BY _Cliona_ 124 - - 76. SPICULES OF _Cliona_ 125 - - 77. THREAD CELLS OF A COELENTERATE, MAGNIFIED 127 - - 78. THE SQUIRREL'S-TAIL SEA FIR (_Sertularia argentea_), - WITH A PORTION ENLARGED 128 - - 79. _Sertularia filicula_ 129 - - 80. " _cupressina_ 130 - - 81. THE HERRING-BONE POLYPE (_Halecium halecinum_) 131 - - 82. _Tubularia indivisa_ 132 - - 83. THE BOTTLE BRUSH (_Thuiaria thuja_) 132 - - 84. _Antennularia antennia_ 133 - - 85. _Aurelia aurita_ 135 - - 86. THE EARLY STAGES OF _Aurelia_ 136 - - 87. _Rhizostoma_ 136 - - 88. _Chrysaora_ 136 - - 89. _Cydippe pileus_ 137 - - 90. SECTION OF AN ANEMONE 139 - - 91. STINGING CELLS OF ANEMONE, HIGHLY MAGNIFIED 140 - - 92. DIAGRAMMATIC TRANSVERSE SECTION OF AN ANEMONE 140 - - 93. LARVA OF ANEMONE 140 - - 94. THE TRUMPET ANEMONE (_Aiptasia Couchii_), CORNWALL; - DEEP WATER 144 - - 95. _Peachia hastata,_ S. DEVON 145 - - 96. _Sagartia pallida,_ DEVON AND CORNWALL 146 - - 97. _Sagartia nivea,_ DEVON AND CORNWALL 147 - - 98. _Corynactus viridis,_ DEVON AND CORNWALL 148 - - 99. _Bunodes thallia,_ WEST COAST 150 - - 100. _Bunodes gemmacea,_ WITH TENTACLES RETRACTED 151 - - 101. _Caryophyllia cyathus_ 152 - - 102. _Sagartia parasitica_ 153 - - 103. THE CLOAK ANEMONE (_Adamsia palliata_) ON A WHELK - SHELL, WITH HERMIT CRAB 154 - - 104. LARVA OF THE BRITTLE STARFISH 158 - - 105. LARVA OF THE FEATHER STAR 160 - - 106. THE ROSY FEATHER STAR 160 - - 107. THE COMMON BRITTLE STAR 162 - - 108. SECTION OF THE SPINE OF A SEA URCHIN 165 - - 109. SEA URCHIN WITH SPINES REMOVED ON ONE SIDE 166 - - 110. APEX OF SHELL OF SEA URCHIN 166 - - 111. SHELL OF SEA URCHIN WITH TEETH PROTRUDING 167 - - 112. INTERIOR OF SHELL OF SEA URCHIN 167 - - 113. MASTICATORY APPARATUS OF SEA URCHIN 167 - - 114. SEA URCHIN DISSECTED, SHOWING THE DIGESTIVE TUBE 168 - - 115. THE SEA CUCUMBER 170 - - 116. A TURBELLARIAN, MAGNIFIED 175 - - 117. _Arenicola piscatorum_ 178 - - 118. THE SEA MOUSE 179 - - 119. TUBE-BUILDING WORMS: _Terebella, Serpula, Sabella_ 182 - - 120. _Terebella_ REMOVED FROM ITS TUBE 183 - - 121. A TUBE OF _Serpula_ ATTACHED TO A SHELL 185 - - 122. _Serpula_ REMOVED FROM ITS TUBE 186 - - 123. THE SEA MAT (_Flustra_) 187 - - 124. _Flustra_ IN ITS CELL, MAGNIFIED 188 - - 125. SEA SQUIRT 189 - - 126. LARVÆ OF MOLLUSCS 191 - - 127. SHELL OF THE PRICKLY COCKLE (_Cardium aculeatum_) - SHOWING UMBO AND HINGE; ALSO THE INTERIOR - SHOWING THE TEETH 192 - - 128. INTERIOR OF BIVALVE SHELL, SHOWING MUSCULAR SCARS - AND PALLIAL LINE 193 - - 129. DIAGRAM OF THE ANATOMY OF A LAMELLIBRANCH 194 - - 130. _Mytilus edulis_, WITH BYSSUS 195 - - 131. A BIVALVE SHELL (_Tapes virgineana_) 196 - - 132. _Pholas dactylus_ 199 - - 133. " " INTERIOR OF VALVE; AND _Pholadidea_ - WITH ANIMAL 201 - - 134. THE SHIP WORM 202 - - 135. 1. _Teredo navalis._ 2. _Teredo norvegica_ 202 - - 136. _Gastrochæna modiolina_ 203 - - 137. 1. _Thracia phaseolina._ 2. _Thracia pubescens_, - SHOWING PALLIALLINE 204 - - 138. 1. _Mya truncata._ 2. INTERIOR OF SHELL. - 3. _Mya arenaria._4. _Corbula nucleus_ 205 - - 139. _Solen siliqua_ 206 - - 140. 1. _Solen ensis._ 2. _Cerati-solen legumen._ - 3. _Solecurtus candidus_ 207 - - 141. _Tellinidæ_ 208 - - 142. 1. _Lutraria elliptica._ 2. PART OF THE HINGE OF - _Lutraria_, SHOWING THE CARTILAGE PIT. 3. _Macra - stultorum._ 4. INTERIOR OF SAME SHOWING PALLIAL - LINE 210 - - 143. _Veneridæ_ 211 - - 144. _Cyprinidæ_ 213 - - 145. _Galeomma Turtoni_ 214 - - 146. 1. _Cardium pygmæum._ 2. _Cardium fasciatum._ - 3. _Cardium rusticum_ 215 - - 147. _Cardium aculeatum_ 215 - - 148. _Pectunculus glycimeris_, WITH PORTION OF VALVE - SHOWING TEETH, AND _Arca tetragona_ 216 - - 149. _Mytilus edulis_ 217 - - 150. 1. _Modiola modiolus._ 2. _Modiola tulipa._ - 3. _Crenella discors_ 218 - - 151. _Dreissena polymorpha_ 219 - - 152. _Avicula_, AND _Pinna pectinata_ 220 - - 153. 1. _Anomia ephippium._ 2. _Pecten tigris._ - 3. _Pecten_, ANIMAL IN SHELL 222 - - 154. _Terebratulina._ THE UPPER FIGURE REPRESENTS THE - INTERIOR OF THE DORSAL VALVE 224 - - 155. UNDER SIDE OF THE SHELL OF _Natica catena_, SHOWING - THE UMBILICUS; AND OUTLINE OF THE SHELL, SHOWING THE - RIGHT-HANDED SPIRAL 225 - - 156. SECTION OF THE SHELL OF THE WHELK, SHOWING THE - COLUMELLA 226 - - 157. DIAGRAM OF THE ANATOMY OF THE WHELK, THE SHELL BEING - REMOVED 228 - - 158. A PORTION OF THE LINGUAL RIBBON OF THE WHELK, - MAGNIFIED; AND A SINGLE ROW OF TEETH ON A MUCH - LARGER SCALE 229 - - 159. EGG CASES OF THE WHELK 230 - - 160. PTEROPODS 231 - - 161. NUDIBRANCHS 234 - - 162. " 235 - - 163. SHELLS OF TECTIBRANCHS 236 - - 164. CHITON SHELLS 238 - - 165. SHELLS OF _Dentalium_ 238 - - 166. _Patellidæ_ 239 - - 167. _Calyptræa sinensis_ 241 - - 168. _Fissurellidæ_ 241 - - 169. _Haliotis_ 242 - - 170. _Ianthina fragilis_ 242 - - 171. _Trochus zizyphinus_. 2. UNDER SIDE OF SHELL. - 3. _Trochus magnus._ 4. _Adeorbis subcarinatus_ 244 - - 172. _Rissoa labiosa_ AND _Lacuna pallidula_ 244 - - 173. SECTION OF SHELL OF _Turritella_ 245 - - 174. _Turritella communis_ AND _Cæcum trachea_ 245 - - 175. _Cerithium reticulatum_ AND _Aporrhais pes-pelicani_ 245 - - 176. _Aporrhais pes-pelicani_, SHOWING BOTH SHELL AND ANIMAL 246 - - 177. 1. _Odostomia plicata._ 2. _Eulima polita._ - 3. _Aclis supranitida_ 246 - - 178. _Cypræa_ (_Trivia_) _europæa_ 247 - - 179. 1. _Ovulum patulum_. 2. _Erato lævis_ 248 - - 180. _Mangelia septangularis_ AND _Mangelia turricula_ 248 - - 181. 1. _Purpura lapillus._ 2. EGG CASES OF _Purpura_. - 3. _Nassa reticulata_ 249 - - 182. _Murex erinaceus_ 249 - - 183. OCTOPUS 251 - - 184. _Loligo vulgaris_ AND ITS PEN 252 - - 185. _Sepiola atlantica_ 252 - - 186. _Sepia officinalis_ AND ITS 'BONE' 253 - - 187. EGGS OF _Sepia_ 254 - - 188. THE NERVE-CHAIN OF AN ARTHROPOD (LOBSTER) 257 - - 189. SECTION THROUGH THE COMPOUND EYE OF AN ARTHROPOD 260 - - 190. FOUR STAGES IN THE DEVELOPMENT OF THE COMMON SHORE - CRAB 261 - - 191. THE BARNACLE 261 - - 192. FOUR STAGES IN THE DEVELOPMENT OF THE ACORN BARNACLE 262 - - 193. A CLUSTER OF ACORN SHELLS 263 - - 194. SHELL OF ACORN BARNACLE (_Balanus_) 263 - - 195. THE ACORN BARNACLE (_Balanus porcatus_) WITH APPENDAGES - PROTRUDED 264 - - 196. A GROUP OF MARINE COPEPODS, MAGNIFIED 265 - - 197. A GROUP OF OSTRACODE SHELLS 265 - - 198. _Evadne_ 266 - - 199. MARINE ISOPODS 267 - - 200. MARINE AMPHIPODS 268 - - 201. THE MANTIS SHRIMP (_Squilla Mantis_) 270 - - 202. THE OPOSSUM SHRIMP (_Mysis chamæleon_) 271 - - 203. PARTS OF LOBSTER'S SHELL, SEPARATED, AND VIEWED FROM - ABOVE 272 - - 204. A SEGMENT OF THE ABDOMEN OF A LOBSTER 272 - - 205. APPENDAGES OF A LOBSTER 273 - - 206. LONGITUDINAL SECTION OF THE LOBSTER 274 - - 207. THE SPINY LOBSTER (_Palinurus vulgaris_) 275 - - 208. THE NORWAY LOBSTER (_Nephrops norvegicus_) 276 - - 209. 1. THE MUD-BORER (_Gebia stellata_). 2. THE - MUD-BORROWER (_Callianassa subterranea_) 277 - - 210. THE COMMON SHRIMP (_Crangon vulgaris_) 278 - - 211. THE PRAWN (_Palæmon serratus_) 279 - - 212. _Dromia vulgaris_ 282 - - 213. THE HERMIT CRAB IN A WHELK SHELL 282 - - 214. THE LONG-ARMED CRAB (_Corystes Cassivelaunus_) 287 - - 215. SPIDER CRABS AT HOME 288 - - 216. THE THORNBACK CRAB (_Maia Squinado_) 290 - - 217. THE PEA CRAB (_Pinnotheres pisum_) 290 - - 218. THE COMMON SHORE CRAB (_Carcinus mænas_) 291 - - 219. THE SHORE SPIDER 294 - - 220. THE LEG OF AN INSECT 295 - - 221. TRACHEA OF AN INSECT, MAGNIFIED 296 - - 222. SEA-SHORE INSECTS 298 - - 223. MARINE BEETLES OF THE GENUS _Bembidium_ 302 - - 224. MARINE BEETLES 303 - - 225. TRANSVERSE SECTION THROUGH THE BONY FRAMEWORK OF A - TYPICAL VERTEBRATE ANIMAL 306 - - 226. THE SEA LAMPREY 309 - - 227. THE PILCHARD 310 - - 228. THE SKELETON OF A FISH (PERCH) 315 - - 229. THE INTERNAL ORGANS OF THE HERRING 316 - - 230. THE EGG-CASE OF THE DOGFISH 319 - - 231. THE SMOOTH HOUND 320 - - 232. THE COMMON EEL 323 - - 233. THE LESSER SAND EEL 326 - - 234. THE THREE-BEARDED ROCKLING 327 - - 235. THE SNAKE PIPE-FISH 328 - - 236. THE RAINBOW WRASS (_Labrus julis_) 330 - - 237. THE CORNISH SUCKER 330 - - 238. THE FIFTEEN-SPINED STICKLEBACK AND NEST 331 - - 239. THE SMOOTH BLENNY 333 - - 240. THE BUTTERFISH 334 - - 241. THE BLACK GOBY 335 - - 242. THE FATHER LASHER 335 - - 243. THE LESSER WEAVER 337 - - 244. THE COMMON PORPOISE 341 - - 245. _Callithamnion roseum_ 359 - - 246. _Callithamnion tetricum_ 359 - - 247. _Griffithsia corallina_ 361 - - 248. _Halurus equisetifolius_ 361 - - 249. _Pilota plumosa_ 361 - - 250. _Ceramium diaphanum_ 363 - - 251. _Plocamium_ 366 - - 252. _Delesseria alata_ 368 - - 253. _Delesseria hypoglossum_ 368 - - 254. _Laurencia pinnatifida_ 371 - - 255. _Laurencia obtusa_ 371 - - 256. _Polysiphonia fastigiata_ 373 - - 257. _Polysiphonia parasitica_ 374 - - 258. _Polysiphonia Brodiæi_ 374 - - 259. _Polysiphonia nigrescens_ 374 - - 260. _Ectocarpus granulosus_ 378 - - 261. _Ectocarpus siliculosus_ 378 - - 262. _Ectocarpus Mertensii_ 378 - - 263. _Sphacelaria cirrhosa_ 379 - - 264. _Sphacelaria plumosa_ 379 - - 265. _Sphacelaria radicans_ 380 - - 266. _Cladostephus spongiosus_ 380 - - 267. _Chordaria flagelliformis_ 380 - - 268. _Laminaria bulbosa_ 384 - - 269. _Laminaria saccharina_ 384 - - 270. _Alaria esculenta_ 385 - - 271. _Sporochnus pedunculatus_ 385 - - 272. _Desmarestia ligulata_ 386 - - 273. _Himanthalia lorea_ 387 - - 274. _Cystoseira ericoides_ 388 - - 275. TRANSVERSE SECTION OF THE STEM OF A MONOCOTYLEDON 391 - - 276. LEAF OF A MONOCOTYLEDON 392 - - 277. EXPANDED SPIKELET OF THE OAT 393 - - 278. THE SEA LYME GRASS 395 - - 279. _Knappia agrostidea_ 397 - - 280. THE DOG'S-TOOTH GRASS 397 - - 281. THE REED CANARY GRASS 397 - - 282. MALE AND FEMALE FLOWERS OF _CAREX_, MAGNIFIED 399 - - 283. THE SEA SEDGE 400 - - 284. THE CURVED SEDGE 400 - - 285. THE GREAT SEA RUSH 400 - - 286. THE BROAD-LEAVED GRASS WRACK 401 - - 287. THE SEA-SIDE ARROW GRASS 401 - - 288. THE COMMON ASPARAGUS 401 - - 289. THE SEA SPURGE 403 - - 290. THE PURPLE SPURGE 404 - - 291. THE SEA BUCKTHORN 404 - - 292. _Chenopodium botryoides_ 405 - - 293. THE FROSTED SEA ORACHE 406 - - 294. THE PRICKLY SALT WORT 406 - - 295. THE CREEPING GLASS WORT 407 - - 296. THE SEA-SIDE PLANTAIN 408 - - 297. THE SEA LAVENDER 408 - - 298. THE DWARF CENTAURY 410 - - 299. THE SEA SAMPHIRE 412 - - 300. THE SEA-SIDE EVERLASTING PEA 413 - - 301. THE SEA STORK'S-BILL 414 - - 302. THE SEA CAMPION 416 - - 303. THE SEA PEARL WORT 417 - - 304. THE SHRUBBY MIGNONETTE 417 - - 305. THE WILD CABBAGE 418 - - 306. THE ISLE OF MAN CABBAGE 418 - - 307. THE GREAT SEA STOCK 419 - - 308. THE HOARY SHRUBBY STOCK 419 - - 309. THE SCURVY GRASS 419 - - 310. THE SEA RADISH 419 - - 311. THE SEA ROCKET 420 - - 312. THE SEA KALE 421 - - 313. THE HORNED POPPY 422 - - - - - THE SEA SHORE - - - - - CHAPTER I - - _THE GENERAL CHARACTERISTICS OF THE SEA SHORE_ - - -What are the attractions which so often entice us to the sea shore, -which give such charm to a ramble along the cliffs or the beach, and -which will so frequently constrain the most active wanderer to rest and -admire the scene before him? The chief of these attractions is -undoubtedly the incessant motion of the water and the constant change of -scene presented to his view. As we ramble along a beaten track at the -edge of the cliff, new and varied features of the coast are constantly -opening up before us. Each little headland passed reveals a sheltered -picturesque cove or a gentle bay with its line of yellow sands backed by -the cliffs and washed by the foaming waves; while now and again our path -slopes down to a peaceful valley with its cluster of pretty cottages, -and the rippling stream winding its way towards the sea. On the one hand -is the blue sea, full of life and motion as far as the eye can reach, -and on the other the cultivated fields or the wild and rugged downs. - -The variety of these scenes is further increased by the frequent changes -in the character of the cliffs themselves. Where they are composed of -soft material we find the coast-line washed into gentle curves, and the -beach formed of a continuous stretch of fine sand; but where harder -rocks exist the scenery is wild and varied, and the beach usually strewn -with irregular masses of all sizes. - -Then, when we approach the water's edge, we find a delight in watching -the approaching waves as they roll over the sandy or pebbly beach, or -embrace an outlying rock, gently raising its olive covering of dangling -weeds. - -Such attractions will allure the ordinary lover of Nature--the mere -seeker after the picturesque--but to the true naturalist there are many -others. The latter loves to read in the cliffs their past history, to -observe to what extent the general scenery of the coast is due to the -nature of the rocks, and to learn the action of the waves from the -character of the cliffs and beach, and from the changes which are known -to have taken place in the contour of the land in past years. He also -delights to study those plants and flowers which are peculiar to the -coast, and to observe how the influences of the sea have produced -interesting modifications in certain of our flowering plants, as may be -seen by comparing them with the same species from inland districts. The -sea birds, too, differing so much as they do from our other feathered -friends in structure and habit, provide a new field for study; while the -remarkably varied character of the forms of life met with on the beach -and in the shallow waters fringing the land is in itself sufficient to -supply the most active naturalist with material for prolonged and -constant work. - -Let us first observe some of the general features of the coast itself, -and see how far we can account for the great diversity of character -presented to us, and for the continual changes and incessant motions -that add such a charm to the sea-side ramble. - -Here we stand on the top of a cliff composed of a soft calcareous -rock--on the exposed edge of a bed of chalk that extends far inland. All -the country round is gently undulating, and devoid of any of the -features that make up a wild and romantic scene. The coast-line, too, is -wrought into a series of gentle bays, separated by inconspicuous -promontories where the rock, being slightly harder, has better withstood -the eroding action of the sea; or where a current, washing the -neighbouring shore, has been by some force deflected seaward. The cliff, -though not high, rises almost perpendicularly from the beach, and -presents to the sea a face which is but little broken, and which in -itself shows no strong evidence of the action of raging, tempestuous -seas; its chief diversity being its gradual rise and fall with each -successive undulation of the land. The same soft and gentle nature -characterises the beach below. Beyond a few small blocks of -freshly-loosened chalk, with here and there a liberated nodule of flint, -we find nothing but a continuous, fine, siliceous sand, the surface of -which is but seldom broken by the protrusion of masses from below. Such -cliffs and beaches do not in themselves suggest any violent action on -the part of the sea, and yet it is here that the ocean is enabled to -make its destructive efforts with the greatest effect. The soft rock is -gradually but surely reduced, partly by the mechanical action of the -waves and partly by the chemical action of the sea-water. The rock -being almost uniformly soft, it is uniformly worn away, thus presenting -a comparatively unbroken face. Its material is gradually dissolved in -the sea; and the calcareous matter being thus removed, we have a beach -composed of the remains of the flints which have been pulverised by the -action of the waves. Thus slowly but surely the sea gains upon the land. -Thus it is that many a famous landmark, once hundreds of yards from the -coast, now stands so near the edge of the cliff as to be threatened by -every storm; or some ancient castle, once miles from the shore, lies -entirely buried by the encroaching sea. - - [Illustration: FIG. 1.--CHALK CLIFF] - -The coast we have described is most certainly not the one with the -fullest attractions for the naturalist, for the cliffs lack those nooks -that provide so much shelter for bird and beast, and the rugged coves -and rock pools in which we find such a wonderful variety of marine life -are nowhere to be seen. But, although it represents a _typical_ shore -for a chalky district, yet we may find others of a very different nature -even where the same rock exists. Thus, at Flamborough in Yorkshire, and -St. Alban's Head in Dorset, we find the hardened, exposed edge of the -chalk formation terminating in bold and majestic promontories, while -the inner edge surrounding the Weald gives rise to the famous cliffs of -Dover and the dizzy heights of Beachy Head. The hard chalk of the Isle -of Wight, too, which has so well withstood the repeated attacks of the -Atlantic waves, presents a bold barrier to the sea on the south and east -coasts, and terminates in the west with the majestic stacks of the -Needles. - - [Illustration: FIG. 2.--WHITECLIFF (CHALK), DORSET] - -Where this harder chalk exists the coast is rugged and irregular. Sea -birds find a home in the sheltered ledges and in the protected nooks of -its serrated edge; and the countless wave-resisting blocks of weathered -chalk that have been hurled from the heights above, together with the -many remnants of former cliffs that have at last succumbed to the -attacks of the boisterous sea, all form abundant shelter for a variety -of marine plants and animals. - - [Illustration: FIG. 3.--PENLEE POINT, CORNWALL] - -But it is in the west and south-west of our island that we find both -the most furious waves and the rocks that are best able to resist their -attacks. Here we are exposed to the full force of the frontal attacks of -the Atlantic, and it is here that the dashing breakers seek out the -weaker portions of the upturned and contorted strata, eating out deep -inlets, and often loosening enormous blocks of the hardest material, -hurling them on the rugged beach, where they are eventually to be -reduced to small fragments by the continual clashing and grinding action -of the smaller masses as they are thrown up by the angry sea. Here it is -that we find the most rugged and precipitous cliffs, bordering a more or -less wild and desolate country, now broken by a deep and narrow chasm -where the resonant roar of the sea ascends to the dizzy heights above, -and anon stretching seaward into a rocky headland, whose former -greatness is marked by a continuation of fantastic outliers and smaller -wave-worn masses of the harder strata. Here, too, we find that the -unyielding rocks give a permanent attachment to the red and olive weeds -which clothe them, and which provide a home for so many inhabitants of -our shallow waters. It is here, also, that we see those picturesque rock -pools of all sizes, formed by the removal of the softer material of the -rocks, and converted into so many miniature seas by the receding of the -tide. - - [Illustration: FIG. 4.--BALANUS SHELLS] - -A more lovely sight than the typical rock pool of the West coast one can -hardly imagine. Around lies the rugged but sea-worn rock, partly hidden -by dense patches of the conical shells of the _Balanus_, with here and -there a snug cluster of young mussels held together by their -intertwining silken byssi. The surface is further relieved by the -clinging limpet, the beautifully banded shells of the variable -dog-periwinkle, the pretty top shells, and a variety of other common but -interesting molluscs. Clusters of the common bladdery weeds are also -suspended from the dry rock, and hang gracefully into the still water -below, where the mantled cowry may be seen slowly gliding over the olive -fronds. Submerged in the peaceful pool are beautiful tufts of white and -pink corallines, among which a number of small and slender starfishes -may climb unnoticed by the casual observer; while the scene is -brightened by the numerous patches of slender green and red algæ, the -thread-like fronds of which are occasionally disturbed as the lively -little blenny darts among them to evade the intruder's glance. Dotted -here and there are the beautiful anemones--the variously-hued animal -flowers of the sea, with expanded tentacles gently and gracefully -swaying, ready to grasp and paralyse any small living being that may -wander within their reach. Here, under a projecting ledge of the rock, -partly hidden by pale green threads, are the glaring eyes of the -voracious bullhead, eager to pounce on almost any moving object; while -above it the five-fingered starfish slowly climbs among the dangling -weeds by means of its innumerable suckers. In yonder shady corner, where -the overhanging rock cuts off all direct rays of the sun from the deeper -water of the pool, are the pink and yellow incrustations of little -sponges, some of the latter colour resembling a group of miniature -inverted volcanic cones, while on the sandy floor of the pool itself may -be seen the transparent phantom-like prawn, with its rapidly moving -spinnerets and gently-waving antennæ, suddenly darting backward when -disturbed by the incautious approach of the observer; and the spotted -sand-crab, entirely buried with the exception of its upper surface, and -so closely imitating its surroundings as to be quite invisible except on -the closest inspection. Finally, the scene is greatly enlivened by the -active movements of the hermit-crab, that appropriates to its own use -the shell which once covered the body of a mollusc, and by the erratic -excursions of its cousin crabs as they climb over the weedy banks of the -pool in search of food. - - [Illustration: FIG. 5.--A CLUSTER OF MUSSELS] - -Thus we may find much to admire and study on the sea shore at all times, -but there are attractions of quite another nature that call for notice -on a stormy day, especially on the wilder and more desolate western -coasts. At such times we delight to watch the distant waves as they -approach the shore, to see how they become gradually converted into the -foaming breakers that dash against the standing rocks and wash the -rattling pebbles high on the beach. The powerful effects of the sea in -wearing away the cliffs are now apparent, and we can well understand -that even the most obdurate of rocks must sooner or later break away -beneath its mighty waves. - - [Illustration: FIG. 6.--BREAKERS] - -The extreme mobility of the sea is displayed not only by the storm -waves, and by the soft ripples of the calm day, but is seen in the -gentle currents that almost imperceptibly wash our shores, and more -manifestly in the perpetual motions of the tides. - -This last-named phenomenon is one of extreme interest to the sea-side -rambler, and also one of such great importance to the naturalist that we -cannot do better than spend a few moments in trying to understand how -the swaying of the waters of the ocean is brought about, and to see what -determines the period and intensity of its pulsations, as well as some -of the variations in the daily motions which are to be observed on our -own shores. - -In doing this we shall, of course, not enter fully into the technical -theories of the tides, for which the reader should refer to -authoritative works on the subject, but merely endeavour to briefly -explain the observed oscillations of the sea and the general laws which -govern them. - -The most casual observer must have noticed the close connection between -the movements of the ocean and the position of the moon, while those who -have given closer attention to the subject will have seen that the -relative heights of the tides vary regularly with the relative positions -of the sun, moon, and earth. - -In the first place, then, we notice that the time of high tide in any -given place is always the same at the same period of the cycle of the -moon; that is, it is always the same at the time of new moon, full moon, -&c. Hence it becomes evident that the moon is the prime mover in the -formation of tides. Now, it is a fact that the sun, though about -ninety-three millions of miles from the earth, has a much greater -attractive influence on the earth and its oceans than the moon has, -although the distance of the latter is only about a quarter of a million -miles: but this is due to the vastly superior mass of the sun, which is -about twenty-six million times the mass of the moon. How is it, then, -that we find the tides apparently regulated by the moon rather than by -the sun? - -The reason is that the tide-producing influence is due not to the actual -attractive force exerted on the earth as a whole, but to the difference -between the attraction for one side of the globe and that for the -opposite side. Now, it will be seen that the diameter of the -earth--about eight thousand miles--is an appreciable fraction of the -moon's distance, and thus the attractive influence of the moon for the -side of the earth nearest to it will be appreciably greater than that -for the opposite side; while in the case of the sun, the earth's -diameter is such a small fraction of the distance from the sun that the -_difference_ in the attractive force for the two opposite sides of the -earth is comparatively small. - -Omitting, then, for the present the minor tide-producing influence of -the sun, let us see how the incessant rising and falling of the water of -the ocean are brought about; and, to simplify our explanation, we will -imagine the earth to be a globe entirely covered with water of uniform -depth. - -The moon attracts the water on the side nearest to it with a greater -force than that exerted on the earth itself; hence the water is caused -to bulge out slightly on that side. Again, since the attractive force of -the moon for the earth as a whole is greater than that for the water on -the opposite side, the earth is pulled away, as it were, from the water -on that side, causing it to bulge out there also. Hence high tides are -produced on two opposite sides of the earth at the same time, while the -level of the water is correspondingly reduced at two other parts at -right angles with these sides. - -This being the case, how are we to account for the observed changes in -the level of the sea that occur every day on our shores? - -Let us first see the exact nature of these changes:--At a certain time -we find the water high on the beach; and, soon after reaching its -highest limit, a gradual descent takes place, generally extending over a -period of a little more than six hours. This is then followed by another -rise, occupying about the same time, and the oscillations are repeated -indefinitely with remarkable regularity as to time. - - [Illustration: FIG. 7.--ILLUSTRATING THE TIDE-PRODUCING INFLUENCE OF - THE MOON] - -Now, from what has been previously said with regard to the tidal -influence of the moon, we see that the tide must necessarily be high -under the moon, as well as on the side of the earth directly opposite -this body, and that the high tides must follow the moon in its regular -motion. But we must not forget that the earth itself is continually -turning on its axis, making a complete rotation in about twenty-four -hours; while the moon, which revolves round the earth in about -twenty-eight days, describes only a small portion of its orbit in the -same time; thus, while the tidal wave slowly follows the moon as it -travels in its orbit, the earth slips round, as it were, under the tidal -wave, causing four changes of tide in approximately the period of one -rotation. Suppose, for example, the earth to be performing its daily -rotation in the direction indicated by the arrow (fig. 8), and the tide -high at the place marked A1, just under the moon, then, in about six -hours, this place will have been carried round to A2, where the tide is -low; and, after similar intervals, to A3 and A4 successively, where -the tide is high and low respectively. Hence the daily changes are to a -great extent determined by the rotation of the earth. - -But we have already observed that each change of tide occupies a little -more than six hours, the average time being nearly six hours and a -quarter, and so we find that the high and low tides occur nearly an hour -later every day. This is due to the fact that, owing to the revolution -of the moon round the earth in the same direction as that of the -rotation of the earth itself, the day as measured by the moon is nearly -an hour longer than the average solar day as given by the clock. - - [Illustration: FIG. 8.--ILLUSTRATING THE TIDES] - -There is yet another point worth noting with regard to the relation -between the moon and the tidal movements of the water, which is that the -high tides are never exactly under the moon, but always occur some time -after the moon has passed the meridian. This is due to the inertia of -the ocean, and to the resistance offered by the land to its movements. - -Now, in addition to these diurnal changes of the tide, there are others, -extending over longer periods, and which must be more or less familiar -to everyone who has spent some time on the coast. On a certain day, for -instance, we observe that the high tide flows very far up the beach, and -that this is followed, a few hours later, by an unusually low ebb, -exposing rocks or sand-banks that are not frequently visible. Careful -observations of the motions of the water for some days after will show -that this great difference between the levels of high and low-water -gradually decreases until, about a week later, it is considerably -reduced, the high tide not flowing so far inland and the low-water mark -not extending so far seaward. Then, from this time, the difference -increases again, till, after about two weeks from the commencement of -our observations, we find it at the maximum again. - - [Illustration: FIG. 9.--SPRING TIDES AT FULL MOON] - -Here again we find that the changes exactly coincide with changes in the -position of the moon with regard to the sun and the earth. Thus, the -_spring tides_--those which rise very high and fall very low--always -occur when the moon is full or new; while the less vigorous _neap tides_ -occur when the moon is in her quarters and presents only one-half of her -illuminated disc to the earth. And, as the moon passes through a -complete cycle of changes from _new_ to _first-quarter_, _full_, -_last-quarter_, and then to _new_ again in about twenty-nine days, so -the tides run through four changes from spring to neap, spring, neap, -and then to spring again in the same period. - - [Illustration: FIG. 10.--SPRING TIDES AT NEW MOON] - -The reason for this is not far to seek, for we have already seen that -both sun and moon exert a tide-producing influence on the earth, though -that of the moon is considerably greater than that of the sun; hence, if -the sun, earth, and moon are in a straight line, as they are when the -moon is full, at which time she and the sun are on opposite sides of the -earth, and also when new, at which time she is between the earth and -sun, the sun's tide is added to the moon's tide, thus producing the -well-marked spring tides; while, when the moon is in her quarters, -occupying a position at right angles from the sun as viewed from the -earth, the two bodies tend to produce high tides on different parts of -the earth at the same time, and thus we have the moon's greater tides -reduced by the amount of the lesser tides of the sun, with the result -that the difference between high and low tides is much lessened. - - [Illustration: FIG. 11.--NEAP TIDES] - -Again, the difference between high and low water marks is not always -exactly the same for the same kind of tide--the spring tide for a -certain period, for example, not having the same limits as the same tide -of another time. This is due to the fact that the moon revolves round -the sun in an elliptical orbit, while the earth, at the same time, -revolves round the sun in a similar path, so that the distances of both -moon and sun from the earth vary at different times. And, since the -tide-producing influences of both these bodies must increase as their -distance from the earth diminishes, it follows that there must be -occasional appreciable variations in the vigour of the tidal movements -of the ocean. - -As the earth rotates on its axis, while at the same time the tidal wave -must necessarily keep its position under the moon, this wave appears to -sweep round the earth with considerable velocity. The differences in the -level of the ocean thus produced would hardly be appreciable if the -earth were entirely covered with water; but, owing to the very irregular -distribution of the land, the movements of the tidal wave become -exceedingly complex; and, when it breaks an entrance into a gradually -narrowing channel, the water is compressed laterally, and -correspondingly increased in height. It is thus that we find a much -greater difference between the levels of high and low tides in -continental seas than are to be observed on the shores of oceanic -islands. - -We have occupied so much of our time and space in explanation of the -movements of the tides not only because we think it desirable that all -who delight in sea-side rambles should understand something of the -varied motions which help to give such a charm to the sea, but also -because, as we shall observe later, these motions are a matter of great -importance to those who are interested in the observation and study of -marine life. And, seeing that we are writing more particularly for the -young naturalists of our own island, we must devote a little space to -the study of the movements of the tidal wave round Great Britain, in -order that we may understand the great diversity in the time of high -tide on any one day on different parts of the coast, and see how the -time of high tide for one part may be calculated from that of any other -locality. - -Were it not for the inertia of the ocean and the resistance offered by -the irregular continents, high tide would always exist exactly under the -moon, and we should have high water at any place just at the time when -the moon is in the south and crossing the meridian of that place. But -while the inertia of the water tends to make all tides late, the -irregular distribution of the land breaks up the tidal wave into so many -wave-crests and greatly retards their progress. - -Thus, the tidal wave entering the Atlantic round the Cape of Good Hope -mingles with another wave that flows round Cape Horn, and the combined -wave travels northward at the rate of several hundred miles an hour. On -reaching the British Isles it is broken up, one wave-crest travelling up -the English Channel, while another flows round Scotland and then -southwards into the North Sea. - -The former branch, taking the shorter course, determines the time of -high tide along the Channel coast. Passing the Land's End, it reaches -Plymouth in about an hour, Torquay in about an hour and a half, the Isle -of Portland in two hours and a half, Brighton in about seven hours, and -London in about nine hours and a half. The other branch, taking a much -longer course, makes its arrival in the southern part of the North Sea -about twelve hours later, thus mingling at that point with the Channel -wave of the _next_ tide. It takes about twenty hours to travel from the -south-west coast of Ireland, round Scotland, and then to the mouth of -the Thames. Where the two waves meet, the height of the tides is -considerably increased; and it will be understood that, at certain -points, where the rising of one tide coincides with the falling of -another, the two may partially or entirely neutralise each other. -Further, the flow and the ebb of the tide are subject to numerous -variations and complications in places where two distinct tidal -wave-crests arrive at different times. Thus, the ebbing of the tide may -be retarded by the approach of a second crest a few hours after the -first, so that the ebb and the flow do not occupy equal times. At -Eastbourne, for example, the water flows for about five hours, and ebbs -for about seven and a half. Or, the approach of the second wave may even -arrest the ebbing waters, and produce a second high tide during the -course of six hours, as is the case at some places along the Hampshire -and Dorset coasts. - -Those who visit various places on our own coasts will probably be -interested in tracing the course of the tidal crests by the aid of the -accompanying map of the British Isles, on which the time of high tide at -several ports for the same time of day is marked. It will be seen from -this that the main tidal wave from the Atlantic approaches our islands -from the south-west, and divides into lesser waves, one of which passes -up the Channel, and another round Scotland and into the North Sea, as -previously mentioned, while minor wave-crests flow northward into the -Irish Sea and the Bristol Channel. The chart thus supplies the data by -means of which we can calculate the approximate time of high tide for -any one port from that of another. - - [Illustration: FIG. 12.--CHART SHOWING THE RELATIVE TIMES OF HIGH TIDE - ON DIFFERENT PARTS OF THE BRITISH COAST - _George Philip & Son. Ltd._ _The London Geographical Institute._] - -Although the time of high water varies so greatly on the same day over -such a small area of country, yet that time for any one place is always -approximately the same during the same relative positions of the sun, -earth, and moon; that is, for the same 'age' of the moon; so that it is -possible to determine the time of high water at any port from the moon's -age. - -The time of high tide is generally given for the current year in the -local calendars of our principal seaports, and many guide-books supply a -table from which the time may be calculated from the age of the moon. - -At every port the observed high water follows the meridional passage of -the moon by a fixed interval of time, which, as we have seen, varies -considerably in places within a small area of the globe. This interval -is known as _the establishment of the port_, and provides a means by -which the time of high water may be calculated. - -Before closing this short chapter on the general characteristics of the -sea shore we ought to make a few observations on the nature of the water -of the sea. Almost everyone is acquainted with the saltness while many -bathers have noticed the superior buoyancy of salt water as compared -with the fresh water of our rivers and lakes. The dissolved salts -contained in sea water give it a greater density than that of pure -water; and, since all floating bodies displace their own weight of the -liquid in which they float, it is clear that they will not sink so far -in the denser water of the sea as they would in fresh water. - -If we evaporate a known weight of sea water to dryness and weigh the -solid residue of sea salt that remains, we find that this residue forms -about three and a half per cent. of the original weight. Then, supposing -that the evaporation has been conducted very slowly, the residue is -crystalline in structure, and a careful examination with the aid of a -lens will reveal crystals of various shapes, but by far the larger -number of them cubical in form. These cubical crystals consist of common -salt (sodium chloride), which constitutes about three-fourths of the -entire residue, while the remainder of the three and a half per cent. -consists principally of various salts of magnesium, calcium, and sodium. - -Sea salt may be obtained ready prepared in any quantity, as it is -manufactured for the convenience of those who desire a sea bath at home; -and it will be seen from what has been said that the artificial -sea-water may be prepared, to correspond almost exactly with that of the -sea, by the addition of three and a half pounds of sea salt to about -ninety-six and a half pounds of water. - -This is often a matter of no little importance to the sea-side -naturalist, who may require to keep marine animals alive for some time -at considerable distance from the sea shore, while their growth and -habits are observed. Hence we shall refer to this subject again when -dealing with the management of the salt-water aquarium. - -The attractions of the sea coast are undoubtedly greater by day than at -night, especially in the summer season, when the excessive heat of the -land is tempered by the cool sea breezes, and when life, both on the -cliffs and among the rocks, is at its maximum. But the sea is grand at -night, when its gentle ripples flicker in the silvery light of the full -moon. No phenomenon of the sea, however, is more interesting than the -beautiful phosphorescence to be observed on a dark summer's night. At -times the breaking ripples flash with a soft bluish light, and the water -in the wake of a boat is illuminated by what appears to be liquid fire. -The advancing ripples, as they embrace a standing rock, surround it with -a ring of flame; while streaks and flashes alternately appear and -disappear in the open water where there is apparently no disturbance of -any kind. - -These effects are all produced by the agency of certain marine animals, -some of which display a phosphorescent light over the whole surface of -their bodies, while in others the light-giving power is restricted to -certain organs or to certain well-defined areas of the body; and in some -cases it even appears as if the creatures concerned have the power of -ejecting from their bodies a phosphorescent fluid. - -It was once supposed that the phosphorescence of the sea was produced by -only a few of the lower forms of life, but it is well known now that -quite a large number of animals, belonging to widely different classes, -play a part in this phenomenon. Many of these are minute creatures, -hardly to be seen without the aid of some magnifying power, while others -are of considerable size. - -Among the peculiar features of the phosphorescence of the sea are the -suddenness with which it sometimes appears and disappears, and its very -irregular variations both at different seasons and at different hours of -the same night. On certain nights the sea is apparently full of living -fire when, almost suddenly the light vanishes and hardly a trace of -phosphorescence remains; while, on other occasions, the phenomenon is -observed only on certain patches of water, the areas of which are so -well defined that one passes suddenly from or into a luminous sea. - -The actual nature of the light and the manner in which it is produced -are but ill understood, but the variations and fitfulness of its -appearances can be to a certain extent conjectured from our knowledge -of some of the animals that produce it. - -In our own seas the luminosity is undoubtedly caused principally by the -presence of myriads of minute floating or free-swimming organisms that -inhabit the surface waters. Of these each one has its own season, in -which it appears in vast numbers. Some appear to live entirely at or -near the surface, but others apparently remain near the surface only -during the night, or only while certain conditions favourable to their -mode of life prevail. And further, it is possible that these minute -creatures, produced as they generally are in vast numbers at about the -same time, and being more or less local, are greatly influenced by -changes of temperature, changes in the nature of the wind, and the -periodic changes in the tides; and it is probable that we are to look to -these circumstances for the explanations of the sudden changes so -frequently observed. - -In warmer seas the phenomenon of phosphorescence is much more striking -than in our own, the brilliancy of the light being much stronger, and -also produced by a greater variety of living beings, some of which are -of great size, and embrace species belonging to the vertebrates and the -higher invertebrate animals. - -Those interested in the investigation of this subject should make it a -rule to collect the forms of life that inhabit the water at a time when -the sea is unusually luminous. A sample of the water may be taken away -for the purpose of examination, and this should be viewed in a good -light, both with and without a magnifying lens. It is probable, too, -that a very productive haul may be obtained by drawing a fine muslin net -very slowly through the water. After some time the net should be emptied -and gently washed in a small quantity of sea water to remove the smaller -forms of life contained, and the water then examined at leisure. - -Of course it must not be assumed that all the species so obtained are -concerned in any way with the phosphorescence of the sea, but any one -form turning up in abundance when collected under the conditions named -will probably have some connection with the phenomenon. - -One may well ask 'What is the use of this light-emitting power to the -animals who possess it?' but this question is not easily answered. The -light produced by the glow-worm and other luminous insects is evidently -a signal by means of which they call their mates, and this may be the -case with many of the marine luminous animals, but it is evidently not -so with those which live in such immense numbers that they are simply -crowded together; nor can it be so with the many luminous creatures -that are hermaphrodite. It is a fact, however, that numbers of deep-sea -species possess the power of emitting light to a striking extent; and -the use of this power is in such cases obvious, for since the rays of -the sun do not penetrate to great depths in the ocean, these luminous -species are enabled to illuminate their own surroundings while in search -of food, and, in many cases at least, to quench their lights suddenly at -such times as they themselves are in danger. - - - - - CHAPTER II - - _THE SEA-SIDE NATURALIST_ - - - OUTDOOR WORK - -Assuming that the reader is one who desires to become intimately -acquainted with the wonderful and varied forms of life to be met with on -the sea shore, or, hoping that he may be lured into the interesting and -profitable pastimes of the sea-side naturalist, we shall now devote a -chapter to the consideration of the appliances required for the -collection and examination of marine life, and to general instructions -as to the methods by which we may best search out the principal and most -interesting objects of the shore. - -First, then, we shall describe the equipment of an enthusiastic and -all-round admirer of Nature--he who is interested in plant forms from -the flowering species down to the 'meanest weed that grows,' and is -always ready to learn something of any member of the animal world that -may happen to come within his reach. And this, not because we hope, or -even desire, that every reader may develop into an all-round naturalist, -but so that each may be able to select from the various appliances named -just those which would be useful for the collection and observation of -the objects which are to form his pet study. - -The most generally useful of all these appliances is undoubtedly some -kind of case of the 'hold-all' type, a case into which specimens in -general may be placed for transmission from the hunting-ground in order -that they may be studied at leisure, and we know of nothing more -satisfactory than the botanist's 'vasculum.' This is an oblong box of -japanned tin, fitted with a hinged front, and having both handle and -strap, so that it can be either carried in the hand or slung over the -shoulder. Of course almost any kind of non-collapsible box or basket -will answer the purpose, but we know of no utensils so convenient as the -one we have named. It is perfectly satisfactory for the temporary -storage of the wild flowers gathered on the cliffs, as it will keep them -moist and fresh for some considerable time; and for the reception of sea -weeds of all kinds it is all that could be desired, for it will -preserve them in splendid condition, and is so constructed that there is -no possibility of the inconvenience arising from the dripping of salt -water on the lower garments. Then, as regards marine animal-life in -general--starfishes, urchins, anemones, molluscs, crustaceans, fishes, -&c.--these may be conveyed away in it with a liberal packing of moist -weeds not only without injury, but in such a satisfactory condition that -nearly all may be turned out alive at the end of a day's work; and this -must be looked upon as a very important matter to him who aims at -becoming a naturalist rather than a mere collector, for while the latter -is content with a museum of empty shells and dried specimens, the former -will endeavour to keep many of the creatures alive for a time in some -kind of artificial rock pool in order that he may have the opportunity -of studying their development and their habits at times when he has not -the chance of visiting the sea shore for the purpose. - - [Illustration: FIG. 13.--THE VASCULUM] - -But although the vasculum is so generally useful for the temporary -storage and the transmission of the objects collected, yet it is not in -itself sufficient for all purposes. There are many marine animals so -small--but none the less interesting because they are small--that they -would probably be lost in a case containing a mass of sea weeds with -various larger creatures. These should be placed in small well-corked -bottles, and temporarily preserved in a little sea-water, or, -preferably, a tuft of one of the delicate weeds so common in our rock -pools. Others, again, though they may be larger, are of so fragile a -nature that they should be isolated from the general stock on that -account alone. Instead of bottles or tubes, small tin boxes may be used, -and these have the advantage of being unbreakable, though, of course, -they will not hold water. This, however, is of no consequence, as most -marine animals may be kept alive for some time in moist sea-weed quite -as well as in water. - -When small animals are required for structural examination only, they -may be put into methylated spirit as they are taken, and when stored in -this way a much larger number may be put into the same receptacle; hence -the collector will often find it convenient to have a small supply of -this liquid while at his work. - -A strong pocket-knife is essential for sea-side work. It serves to -remove those molluscs that adhere firmly to the rocks by suction, and -also others that fix themselves by means of a byssus of silken fibres, -as is the case with mussels. It will also be employed in the removal of -acorn barnacles, anemones, and small tufts of algæ, and may be useful in -cutting through the stouter weeds. Small sponges and other low forms of -life often form incrustations on the solid rock, and may be peeled off -with the aid of a knife. In the case of the last-named, however, as well -as with the anemones and other fixed animals, it is often far more -satisfactory to remove a small portion of the rock itself with the -animal attached, and for this purpose a small hammer will be of great -service. - -A strong net of some kind is necessary in searching the rock pools, and -as suitable nets are, we believe, not to be obtained of the dealers in -naturalists' appliances, it devolves on one to manufacture a net -according to his requirements. - -The simplest form of net may be made by bending a piece of stout -galvanised iron wire into the form here shown (fig. 14), and firmly -wedging the two straight ends in a short piece of strong metal tube -which will also serve as a ferrule for the attachment of a tough handle. -Such a circular frame although satisfactory for a net to be used in -fresh-water ponds and streams, is not nearly so suitable for the -irregular rocky pools to be met with on the sea coast, for it will not -enable one to search the numerous corners and crevices into which many -marine creatures will retire on being disturbed, but it may be greatly -improved by bending the side opposite the ferrule into a moderately -sharp angle and then turning the angle slightly upward, as shown in fig. -15. - - [Illustration: FIG. 14.--WIRE RING FOR NET] - - [Illustration: FIG. 15.--NET FRAME WITH CURVED POINT] - -Another very convenient net frame may be made by bending the wire into a -rhomboidal form (fig. 16), the ferrule being attached by means of two -short, straight ends at one of the angles. The opposite angle will serve -the purpose of searching into the crannies of the rocks, while the -straight sides will prove very useful in removing the objects that lie -on the sandy bottoms so commonly seen in rock pools. The semicircular -net shown in fig. 18 will also prove useful for working on sands or for -scraping the flatter surfaces of weed-covered rocks. - - [Illustration: FIG. 16.--RHOMBOIDAL FRAME FOR NET] - -The material of the net should be some kind of strong gauze, or a -loosely-woven canvas. Leno answers very well, but is somewhat easily -torn, and will have to be frequently renewed. This, however, may be -avoided to a great extent if, instead of sewing the gauze directly round -the wire, a strip of strong calico be first attached to the frame, and -the gauze then sewn to the calico; for it will be understood that any -fragile material placed round the wire will soon be worn through by -friction against the rugged surfaces of the rocks and stones. The net -itself should not be very deep, and should have no corners; and as to -the length of the handle, that will be determined by the fancy of the -collector, or by the character of the ponds to be searched, but a tough -walking-stick with a crook handle will generally answer all purposes, -the crook being itself frequently useful for removing the larger weeds -and other obstructions. - - [Illustration: FIG. 17.--RHOMBOIDAL NET] - - [Illustration: FIG. 18.--SEMICIRCULAR NET] - - [Illustration: FIG. 19.--THE DREDGE] - -Although the net, as above described, will answer the requirements of -nearly all young collectors, yet there may be some, who, not satisfied -with the exploration of the rocks and pools exposed when the tide is -out, desire to know something of the creatures that live entirely beyond -low-water mark, where the water is generally too deep for work with a -hand net. To such we recommend a small dredge that may be lowered from a -boat and then drawn along the bottom. A good form of dredge is shown in -fig. 19, and a little skill and ingenuity will enable anyone to -construct one with the help of our illustration; but, seeing that the -best work is to be done on rough bottoms, it is absolutely necessary -that both frame and net should be made of the stoutest materials that -can be conveniently employed. - - [Illustration: FIG. 20.--THE CRAB-POT] - -Those who have ever accompanied a fisherman while taking a pull round to -examine the contents of his crab or lobster pots will probably have -noticed what strange creatures, in addition to the edible crabs and -lobsters, sometimes find their way into the trap. These creatures are -often of great interest to a young naturalist, and it will repay him to -take an occasional trip with a fisherman in order to obtain them; or, -still better, to have a crab-pot of his own. The writer has obtained -many good specimens by means of an inexpensive trap, on the same -principle as the ordinary crab-pot, made from an old metal bird-cage of -rather small size. The bottom was removed, and a very shallow bag of -thick canvas fixed in its place; and some of the wires were cut, and -bent inwards so as to allow the easy entrance of moderately large -crustaceans and other creatures, while at the same time they served as a -barrier to their escape. Such a trap, baited with pieces of fish, and -let down to a rocky bottom, will enable the young naturalist to secure -specimens that are seldom seen between the tide-marks; and the animals -thus obtained will include not only those larger ones for which the -opening was made, but also a variety of smaller creatures that may enter -between the wires of the cage. Some of the latter may, of course, escape -by the same way as the trap is being hauled up for examination, but this -is not so likely to occur if the canvas bottom is of a material so -loosely woven that water can pass through it very freely. It will, of -course, occur to the reader that the insertion of a stone or other -weight will assist in sinking the trap; also that the ordinary door of -the cage forms a ready means by which the captives may be removed. - - [Illustration: FIG. 21.--AN OLD BIRD-CAGE USED AS A CRAB-POT] - -One thing more: make it a rule never to go out collecting natural -objects of any kind without a note-book and pencil. This, to the -beginner who is anxious to get to his work, with the idea only too -prevalent with the amateur that the success of his labours is to be -measured only by the number of specimens obtained, may seem quite an -unnecessary part of the equipment. But it must be remembered that there -is much to _observe_ as well as much to collect on a well-selected -coast; and that without the aid of the book and pencil a great many of -the observations made will be forgotten, and thus much interest that -would otherwise be attached to the objects permanently preserved will be -lacking. - -The above appliances include the only necessary equipment of the -sea-side naturalist, with the exception of a few required for occasional -use in connection with the species of a somewhat restricted habitat, and -the outfit of the sea angler. The former will be dealt with in the -chapters where the species concerned are described, while the subject of -sea angling is of such general interest that we propose to devote a -short chapter exclusively to it. - -It may seem hardly necessary to discourse on the nature of the attire -most suitable for sea-side work, since the majority will readily form -their own opinions on this matter, but perhaps a few words of advice to -the inexperienced may not be altogether out of place. First, then, make -it a rule to wear no clothing of any value. The work will lead the -enthusiast over slippery weeds, on treacherous boulders, over rocks -covered with sharp acorn shells, and among slimy and muddy stones, and -many a slip may occur in the course of a day's work. Large pockets -specially but simply made by sewing square pieces of lining on the -inside of an old jacket are a great convenience; a cap rather than a -brimmed hat should be worn unless the latter be considered essential for -protection from a burning summer's sun; and a pair of old shoes, -preferably with rubber soles, are just the thing for both rough and -slippery rocks, as well as for wading through shallow waters. Other -details we can safely leave to the fancy of the reader himself. - -Now comes the most important question 'Where shall we go?' Fortunately -we are favoured with a great extent of coast-line considering the area -of our country, but the character of the coast is so diversified, both -with regard to its scenery and its life, that the naturalist will do -well to carefully select his locality according to the objects he -desires to study. The east coast of England is not generally noted -either for variety or abundance of marine life, and the same is true -both of the south-east and a large portion of the south coast. In some -places the beach is formed of an unbroken stretch of sand on which one -may walk for miles without seeing any sign of life, with the exception -of an occasional empty shell and a few fragments of dried sea-weed -washed in by the breakers during a recent storm; while at the same time -the cliffs, if such exist at all, are not very generous in their -production of the fauna and flora that are characteristic of the shore. -But even on the coasts referred to there are, here and there, isolated -spots where the uplands jut into the sea, giving rise to bold -promontories, at the foot of which are the fallen masses of rock that -afford protection to a moderate variety of truly marine life, while the -rough bottoms beyond yield numerous interesting forms that may be -secured by means of the dredge or suitable traps. Such spots are to be -found where the chalk hills abut on the sea, as at Flamborough and -Beachy Head, but it is in the neighbourhood of Weymouth that the English -coast really begins to be of great interest to the naturalist. From here -to the Land's End almost every part of the shore will yield a great -variety of life in abundance, and the same is true of the rocky coasts -of the west, and also of the more rugged shores of the Isle of Wight. -As an ideal hunting-ground one cannot do better than to select one of -the small fishing towns or villages on the rocky coasts of Devon and -Cornwall. With such a spot as his headquarters the most enthusiastic -sea-side naturalist will find ample employment. The exposed rocks and -rock pools yield abundance of life; and if these be searched when the -tide is out, there will remain plenty of sea angling and other -employments to occupy him at other times. - -We will now describe the actual work of the sea-side naturalist, giving -the necessary instructions for the observation and collection of the -various living things he will meet with. - -First, then, with regard to work on the cliffs, a very few words will -suffice; for, seeing that the objects of interest to be met with here -will consist principally of the various flowers that are peculiar to or -characteristic of the sea shore, and certain insects and other creatures -more or less partial to a life on the cliffs, we may regard these as -coming within the range of the general work of the botanist, -entomologist, &c.; and since instructions for the collection and -preservation of such objects have already been given in former works of -this series, we may pass them over at once in order to deal with those -objects which are essentially marine. - -It has already been hinted that the right time for collecting on the -shore is when the tide is at its lowest; and in order that the best work -may be done the collector should consult the local tide-tables, or -calculate, if necessary, the time of high tide from the establishment of -the port; and, of course, the period of spring tides should be selected -if possible. The time during which work should continue must be -regulated according to the enthusiasm of the collector or the time at -his disposal, but, as a rule, it is advisable to be on the scene of -action about three hours before the time of low tide, with a -determination to work continuously until the lowest ebb of the water. - -On reaching the beach it is always advisable to start by examining the -line of miscellaneous material at high-water mark, along which may be -found quite a variety of objects, more or less interesting, which have -been washed in by the breakers, especially just after a storm, together -with numerous scavengers of the shore that perform a most useful work in -devouring the decomposing organic matter that would otherwise tend to -pollute the air. - -Here we may find many useful and interesting objects of both the animal -and vegetable worlds. Among the former are the empty shells of both -univalve and bivalve molluscs, some of which are more or less worn by -the action of the waves, while others are in splendid condition for -examination and study. Here, too, are various species of sea firs and -the skeletons of sponges; the shell of the cuttle-fish, and occasionally -a cluster of the eggs of this creature--the sea-grapes of the fishermen; -also the egg-cases of the skate and the dog-fish--usually empty, but -sometimes enclosing the young animal still alive; and, lastly, we -frequently meet with portions of the skeletons of fishes in a perfect -state of preservation, the animal matter having been cleared away by the -combined action of the scavengers previously referred to. Then, as -regards the vegetable world, we often find beautiful specimens of -sea-weeds along the high-water mark, some of which are rarely met with -in the rock pools, since they are species that have been detached from -beyond the line of low water, and washed up by the breakers. - -On turning over the debris thus thrown on the beach we intrude on the -privacy of numerous living creatures which immediately scamper away to -find a new hiding-place. These consist principally of sand-hoppers, but -occasionally we find members of the insect world engaged in the same -useful work in addition to the numerous flies that perform their office -of scavengers in the bright sunshine on the top of the matter that -supplies them with food. - -It will be interesting to capture a few of these scavengers, and to -compare them with others of the same order obtained from different -localities. Thus, the flies may be compared with the more familiar house -fly, and the sand-hoppers of high-water mark with similar crustaceans to -be afterwards obtained lower on the beach. - -Attention should now be given to the rocks left exposed by the -retreating tide, and it is here that the real work begins. Examine each -rock pool as soon as possible after it is no longer disturbed by the -waves. Remove any tufts of corallines or other weeds required for study -or preservation, and simply place them, pro tem., in the vasculum or -other receptacle provided for the purpose. These will form a useful -protective packing for other objects that are to be carried away, so -that it will be advisable to secure a moderate amount rather early, even -though they may not be required for any other purpose. Live molluscs, -crabs, small fishes, &c., may all be put in the receptacle with this -weed, and all will probably be still alive after the collecting and the -homeward journey have been completed. Probe the corners of the pool -with the point of the net, and also sweep the net upward among the weeds -to remove any creatures that seek shelter among the fronds. Tufts of -corallines and other weeds should be searched for the small and delicate -starfishes that live among them, and any stones that may cover the -bottom of the pool should be lifted. Anemones may be removed from the -rocks by means of a rather blunt knife; but, if possible, it will be -better to chip off a small piece of the rock with the anemone attached -to it, and wrap it lightly round with a tuft of soft weed previous to -placing it in the collecting case. - -A number of rock pools should be searched in this manner, but those -chosen should vary as much as possible in general character. All very -small and delicate objects should be isolated from the general stock, -and placed, with the usual packing material, either in tin boxes or -small wide-mouthed bottles; and if any animals taken are not required -alive, but only for preservation, they should be preferably killed at -once and then stored in a separate case. Some creatures are easily -killed by simply dropping them into a bottle of fresh water, but others -should be covered with methylated spirit. It should be mentioned, -however, that the natural appearance of some of the crustaceans is quite -destroyed by strong spirit, which soon makes them look as if they had -been boiled. Some species are changed in this way much more readily than -others; and, until sufficient experience has been gained to enable the -young collector to distinguish between them, it will be advisable to -kill and temporarily preserve crustaceans in spirit that has been -considerably diluted with water--about two parts of water to one of -spirit, for example. Further, there are certain fragile starfishes that -have a way of breaking themselves into pieces when dropped into spirit, -or even when suddenly disturbed in almost any other manner. These must -always be handled gently, and if it is required to kill them for -preservation, the best way will be to put them in a little salt water, -and then gradually add fresh water until the desired result is obtained. - -Perhaps the most productive of all sea-shore work is the turning over of -the stones of various sizes near the low-tide mark, and the examination -of the chinks and sheltered hollows of the rocks that are left uncovered -for but a short period. This work should be carried on as near the -water's edge as possible, closely following the receding tide; and the -collector must now be prepared with a number of small bottles or tins -for the isolation of small and delicate specimens. He must also be on -the alert for numerous examples of protective resemblance, in which the -animals concerned so closely resemble their surroundings in colour and -general character of surface that they are detected only by careful -observation, while the difficulty of identification is still further -increased in instances where the creatures remain perfectly still even -when disturbed. - - [Illustration: FIG. 22.--A YOUNG NATURALIST AT WORK] - -Under the stones all manner of animals--fishes, crustaceans, worms, -molluscs, starfishes, anemones, &c.--will be hiding until covered by the -next tide. Some of these will be found on the ground beneath the stones, -and others attached to the under surfaces of the stones themselves; -therefore both should be carefully examined, attention being given at -first to the more active species that hurry away with all speed towards -a new shelter as soon as they find themselves exposed to the light; the -less active creatures may then be secured at leisure. - -The tide will not allow the collector a great deal of time in which to -turn over the most productive stones--those close to the low-water mark, -so there is but little opportunity of observing the movements and other -interesting habits of many of the animals found; hence it is advisable -to secure a good variety of living specimens, especially of the less -familiar species, in order that they may be placed in some kind of -aquarium, temporary or otherwise, for observation at home. - - [Illustration: FIG. 23.--A GOOD HUNTING-GROUND ON THE CORNISH COAST] - -One thing more remains to be done while the tide is well out, and that -is to examine the weed-covered rocks near the water's edge. Lift the -dangling weeds and carefully search the rocks for those low forms of -animal life that form incrustations on the surface, as well as for new -species of anemones, sea firs, &c. Lastly, look well into the dark and -narrow chinks of the rocks, for here several species of lowly animals -that are hardly met with elsewhere may be found, and also certain -crustaceans that delight to squeeze their bodies into the remotest -corner of a sheltered niche. - - - - - CHAPTER III - - _SEA ANGLING_ - - -We do not propose dealing with this subject from the point of view of -the angler, but rather that of the naturalist. The former is actuated -principally, if not entirely, by the mere love of sport; or, it may be, -to a great extent by the desire to obtain a supply of fish for food; and -he generally estimates the success of his expeditions not by the number -of _species_ captured, but by the total weight of his catch, no regard -being paid, as a rule, to the inedible specimens. The naturalist, -however, does not desire weight, or sweetness of flesh. He works the -greatest possible variety of habitats, with the object of determining -the number of species inhabiting the locality and of learning as much as -possible of their general form, habits, and adaptations of structure to -habits. His success is measured by the number and variety of species -caught, and he pays but little attention to superiority of size or -weight, or to the estimated market value of his haul. The element of -sport may enter more or less largely into the pleasure of his -occupation, but the main end in view is to learn as much as possible of -all the species obtainable. - -Further, our remarks will not include the subject of the different kinds -of fishing usually resorted to by sea anglers, but will be confined -almost exclusively to the simple means of catching the common species -that frequent the immediate neighbourhood of the shore. - -If the reader will follow the general instructions given in Chapter II. -on the outdoor work of the marine naturalist, he will undoubtedly make -the acquaintance of a considerable variety of interesting species which -may be captured in the rock pools, found under stones at low tide, or -obtained by means of a small dredge; but his knowledge of our littoral -fishes may be appreciably extended by the occasional employment of rod -and line from rocks and piers, or from a small boat in close proximity -to the shore. - -The appliances required are of a very simple nature, and not at all -costly. The long, heavy rod and strong tackle of the sea angler and -professional fisherman are not at all essential to our purpose, for our -work will be confined almost exclusively to shallow water, and the fish -to be caught will be chiefly of small size. True it is that one may -occasionally find his light tackle snapped and carried away by the -unexpected run of a large fish, for cod and other large species often -approach close to the shore, and bite at baits intended for the smaller -fish that make their home among the partly submerged rocks of the coast; -but such surprises will not frequently occur, and the young naturalist -may learn all he wants to know of the fishes of our shallow waters with -the aid of a light rod of about nine or ten feet and one or two light -lines of no great length. - -It must not be understood, however, that we assume the reader's -disinclination to know anything of the inhabitants of deep water, but -rather that we consider the whole subject of deep-sea fishing quite -beyond the scope of this work. It is a fact that quite a large number of -species, the forms and habits of which are extremely interesting, live -exclusively on deep bottoms. These should undoubtedly be studied by all -who are interested in the various phases of marine life; but unless the -reader is prepared to practise sea fishing in all its branches--to put -his trust in the restless sea, supplied with all the necessary heavy -gear, and to risk those internal qualms that arise from the incessant -swaying of the boat on open waters, he should make arrangements with the -professional deep-sea fisher--preferably a trawler--for the supply of -those disreputable species that invariably form part of the haul, while -the better-known food fishes can always be obtained from dealers for -purposes of study. - -On one occasion we had a rather unique and very successful interview -with a friendly trawler. She was sailing slowly towards her station in a -south-western fishing port, while two of her crew were clearing her -nets, and throwing all refuse into the sea. We rowed behind her in order -to see the nature of the rejected portion of the haul, and finding that -it included specimens of interesting fishes of ill repute, dead but -perfectly fresh, we followed her track, and collected a few for future -examination. Presently our movements were watched from aboard, and we -were invited to pull up to larboard, where a short explanation as to our -wants led to the acquisition of quite a variety of deep-sea life, -including several species of fishes not often seen on land, crabs, -shelled and shell-less molluscs, worms, star-fishes, and various lowly -organised beings, many alive and in good condition, together with -several good food fishes thrown in by way of sympathy. There is no doubt -that a naturalist can obtain much more deep-sea life with the aid of a -friendly trawler than by any amount of 'fishing' with ordinary tackle -from a boat; and this without the necessity of going to sea at all, if -he will only take the opportunity of examining the nets as the boats are -stranded on their return. - -But now to return to our angling:--We have to provide a light rod, about -ten feet long, with a winch, and a line of twisted silk or other thin -but strong material; also a light hand line, and a supply of gut, leads, -shot, and hooks, together with one or two small floats, and a few bait -boxes. - -We do not, as a rule, recommend the amateur angler to use both rod and -hand line at the same time, for the attempt to do this leads to the -neglect of both. In the end it is not likely to lead to any gain, so -many fish being lost through the inability to strike at the moment a -bite is given, and so much time having to be devoted to the baiting of -hooks rather than to the direct management of the lines. In most cases -the rod is much more convenient than the hand line. The young collector -will meet with the greatest variety of species in rocky and weedy -places, where abundant shelter exists for those fishes that prefer to -keep well under cover, and any attempt with a hand line in such spots -will certainly lead to frequent loss of hooks, and often of lead, line, -and temper. Such a line must be reserved for fishing on sandy bottoms, -while the ten-foot rod recommended will enable the angler to do good -work in the rockiest parts without much danger of fouling; and, in fact, -to fish anywhere along the coast. - -The arrangement of hooks and lead must necessarily depend on the -character of the place to be worked, but in all cases we strongly -recommend no such multiplicity of hooks as is made use of by fishermen -and others who fish for food. In their case the use of so many hooks -often pays them well; but, as we have previously hinted, the naturalist -does not desire quantity of fish so much as variety of species. Further, -there is no necessity to make his work heavy and arduous. His desire is -not to spend an undue proportion of his time in baiting hooks, but to -have his line so under control that he is ready to strike at any moment, -and to be able to alter the conditions of his work as often as his ideas -or the conditions change. - -In rugged and weedy places the hooks must be kept free from rocks and -weeds. This may be done by letting down the rod line with a lead at the -bottom, and one or two hooks fastened to gut at such a level as to keep -quite clear of weeds. A much better arrangement, and one which we -ourselves almost invariably employ, consists of a light lead, as a rule -not exceeding an ounce in weight, fastened at the end of the line, and -below it a few feet of gut terminating in a single hook. With such -tackle it is of course necessary to determine previously the depth of -the water, in order to adjust the line to such a length that the hook -keeps clear of rocks and weeds, and a float may be used if desired. - - [Illustration: FIG. 24.--ROUND BEND HOOK WITH FLATTENED END] - -We do not recommend a float for the general work of the marine -collector, for it is a decided advantage to be prepared to bring the -bait to any level from bottom to surface, especially when the water is -so clear that the fish may be seen swimming, in which case one is often -impressed with the desire to capture a specimen in order to establish -its identity, and for such work as this a float is superfluous. If, -however, a float is used, it should be a sliding one, so that it may be -adapted to the rising and falling of the tide. - - [Illustration: FIG. 25.--LIMERICK HOOK, EYED] - -Of hooks there is a great variety to choose from, differing in the form -both of the curve and of the end of the shank. As to the curve, those -with a decided twist are best adapted to our purpose, chiefly on account -of the fact that sea fishes generally have larger mouths than -fresh-water species of the same size, and are consequently better held -with a twisted hook. The shanks of sea hooks are either flattened or -eyed, and each is as good as the other providing the snood is firmly -attached; but some amateurs find a greater difficulty in attaching the -snood to the former than to the latter. - -Gut snoods are recommended for our purpose, and fig. 26 shows one method -by which they may be fastened to a flattened shank, while fig. 27 -illustrates the figure-of-eight knot by means of which the eyed shank -may be firmly secured. The gut should be soaked for some hours in cold -water previous to tying, and it may be kept soft for some considerable -time by giving it a few hours' immersion in a solution of -glycerine--about one part of glycerine to four or five parts of water. - - [Illustration: FIG. 26.--METHOD OF ATTACHING SNOOD TO FLATTENED HOOK] - -Small hooks will be most suitable for our purpose; and if the reader -finds any difficulty in attaching the snood firmly, he may purchase -suitable hooks ready mounted on gut, though, of course, these are more -expensive than the flattened or eyed hooks generally used for -sea-fishing. Such small and fragile hooks may be occasionally snapped -off by the run of a vigorous fish of moderate size, therefore it is -advisable to have a supply of larger hooks, ready fixed on strong -snoods, to be used when it is found that the shore is frequented by -larger fishes than those generally caught close to land. - - [Illustration: FIG. 27.--METHOD OF ATTACHING SNOOD TO EYED HOOK] - -When fishing with a rod and line from rocks, or from piers, the -foundations of which are covered with large weeds, the bait will -frequently be carried by currents among the weeds and snapped off when -endeavours are made to release the hook. This will especially be the -case when the hook is a few feet below the lead, as we have already -suggested it should be. To reduce the frequency of such mishaps, it will -be a good plan to weight the gut below the lead by means of a few split -shot. In fact, in sheltered places, where the water is not disturbed, -these shot may take the place of the lead, but little weight being -necessary for rod fishing in such localities. - -The amateur sea angler is often in great doubt as to the best bait to -use; and, believing that a certain kind of bait is absolutely necessary -for his work in some particular spot, is often at a loss to obtain it. -This bait difficulty is evidently a prevailing one among amateur sea -fishers, if one may judge from the frequent questions asked as to the -best or proper bait to use, and from the very common 'Can you oblige me -with a little bait?' - -This latter question, we believe, is frequently the outcome of -carelessness or laziness on the part of the asker. He has not the -forethought, born of enthusiasm, that would lead him to procure a -suitable bait, at a convenient time, previous to starting off on his -angling expedition, but rather depends on the possibility of being able -to beg or otherwise secure sufficient for his purpose at the time; yet -there are so many good baits that are easily secured at the proper time -and place that the enthusiastic angler need never be at a loss. Some of -these may be collected by himself at low tide, others may be obtained -from local fishermen, or from the tradesmen of the town or village. - - [Illustration: FIG. 28.--THE LUGWORM] - -Some anglers seldom collect their own bait, either purchasing it or -employing some one to collect it for them; but we are of opinion that -the pleasure of a day's fishing begins here, and especially so when the -angler is of the naturalist type, for he will frequently learn more of -the nature and habits of living creatures during one hour's -bait-collecting than during three or four hours' angling. It is true -that the work in question is often a bit laborious, particularly on a -warm day, and that it may be frequently described as dirty and odorous; -but what is that to one who is interested in his employment, and who -derives pleasure in doing his own work? - -Fishermen often use lugworms for bait, and although these constitute one -of the best baits for their own fishing, they are not so suitable for -the purposes of the amateur angler, fishing with small hooks close to -shore. They may be dug out of the sand when the tide is out, and are -most abundant where the sand is mixed with mud. A spade should be used, -and this should be thrust deep into the sand, selecting those spots -where the holes or burrows of the worms most abound. Lugworms should be -used whole; and being of large size, are suitable for baiting large -hooks only. They may be kept alive in wet sand or sea-weed, preferably -the latter for convenience, and stored till required in a wooden box. - -Ragworms also afford good bait, and are particularly adapted for shore -angling with small hooks. Almost all the fishes that frequent our shores -take them readily, but they are not to be found in all localities. They -are to be taken, though not usually in large numbers, on rocky shores -where numerous stones lie among the somewhat muddy deposits of the more -sheltered nooks, where they may be seen on turning over the stones. The -best situation for ragworms, however, is the more or less odoriferous -mud so frequently deposited in the estuaries of rivers and in landlocked -harbours. Here they maybe dug out in enormous numbers with a spade, -attention being directed to those spots where their burrows are most -numerous. They are best stored with a little of the mud in a shallow -wooden box provided with a sliding, perforated lid. - - [Illustration: FIG. 29.--THE RAGWORM] - -Failing a supply of the marine worms just mentioned, the common -earthworm may be used as a substitute, but it is decidedly less -attractive to the fishes; and the same may be said of gentles--the larvæ -or grubs of flies. The latter may be bred in large numbers by simply -placing a piece of liver in the soil with only a small portion exposed. -If this is done in the summer time, hundreds of eggs will soon be -deposited on it, and in about a week or so it will be found to be a -living mass of fat white grubs, perhaps more useful to the fresh-water -angler than to his marine counterpart. - -Among the so-called shell fish of the class _mollusca_, mussels, -limpets, cockles, and whelks are all largely used for bait. The last of -these are too large for our purpose, but form a splendid bait for -deep-sea fishing, while the other three, and especially the mussels, are -well suited for shore work. Mussels, in fact, provide one of the best -possible baits for almost all kinds of shore fishing, the only drawback -being the excessive softness of their bodies, which enables them to be -easily torn from the hook. When small hooks are used, mussels of a small -size may be used whole, or the larger ones may be divided into portions -of suitable size; and in any case it will be found a good plan to tie -the bait to the hook with a short piece of cotton thread. - - [Illustration: FIG. 30.--DIGGING FOR BAIT] - -Mussels are not easily opened without injury, and consequently some -anglers give them a short immersion in hot water, to kill the animal and -thus cause the shell to gape. As far as our own experience goes, the -value of the bait is not deteriorated by this treatment, though some are -of opinion that it is not so attractive after scalding. Mussels are -opened, when alive, much in the same way as oysters, but the valves of -the shell fit together so closely that it seems at first almost -impossible to insert a knife between them. This, however, can be done -with ease if one valve is first made to slide a little way over the -other by pressing it with the thumb. This being accomplished, the two -valves should not be separated by the mere force of the knife, for this -would tear the animal within, and render it more or less unfit for its -purpose; but first direct the edge of the knife towards the _adductor -muscle_, by means of which the animal pulls its valves so firmly -together, and then cut through this close to the inner surface of the -upper valve. This valve can then be lifted without injury to the soft -parts, and the whole animal removed from the other valve by cutting -through the same muscle close to it. - - [Illustration: FIG. 31.--METHOD OF OPENING A MUSSEL] - -Between the two lobes of the _mantle_--the soft covering on both sides -of the animal that previously lined the shell--will be seen a brown, -fleshy, tongue-like body. This is the 'foot' of the mussel. The point of -the hook should first be run through this, and then from side to side -through the mantle, and finally through the adductor muscle previously -described. If this is carefully done, there will be little fear of the -bait becoming detached unless it is subjected to rough usage, and still -less if it is tied round the shank of the hook by means of a short piece -of cotton thread. - -It is probably superfluous to mention to the reader the fact that -mussels are to be found on almost every rocky coast, where they may be -seen attached to the rocks by means of a bunch of silky fibres called -the _byssus_; and that, failing this, they are to be obtained from -almost every fisherman and fish-dealer; if, however, these molluscs are -not to be obtained, cockles may be used as a substitute, though it will -probably be found that they are appreciably inferior, except when -fishing for dabs and plaice on sandy shores, in which case they are -highly satisfactory. Cockles abound on most sandy coasts, where they -live a little below the surface; and are usually obtained by means of an -ordinary garden rake. Sometimes we meet with them in large numbers in -the estuaries of rivers, where they lie buried in the banks of mixed -sand and mud that are left exposed at low tide. - -Limpets are extensively used for bait in some places, especially by -amateur anglers; and often with good results. They should always be -removed from the rocks without injury, and this is no easy matter to -those who do not know how to deal with them. If taken completely by -surprise, one sharp, but light tap on the side of the conical shell will -successfully detach them from their hold; or they may be raised by means -of the blade of a strong pocket-knife that has been thrust beneath the -cone. - -For our work small limpets will prove far more satisfactory than large -ones, and these may be used whole; but if the limpets are too large for -the hooks employed, the soft, upper part of the body only need be used. - -It is not an easy matter to remove fresh limpets from their shells -without destroying this soft portion of the animal, but if placed for a -minute or so in hot water they come out quite easily, and are apparently -none the less attractive as bait. Some fishermen on the Cornish coast -always collect the largest limpets for bait, remove them from their -shells by means of hot water, and arrange them on the rocks to become -partly dry. When required for bait, the soft parts only are used, but -these, having been more or less hardened by the drying process, hold -much better on the hook than when fresh. - -And now, after mentioning the fact that land snails are occasionally -used, though, we believe, with no very considerable success, for sea -fishing, we will note a few baits derived from the higher head-footed -molluscs--the squid, cuttle-fish, &c. There are several species of these -peculiar molluscs, but the common squid and the common cuttle of our -seas, and especially the former, is highly prized as bait. It may be -obtained from fishermen, who frequently haul it in their nets; but if -supplied alive and fresh from the sea it must be handled very -cautiously, otherwise it may discharge the contents of its ink-bag over -one with the most unpleasant results. It is certainly best used while -fresh, though some suspend it until dry, and then store it for future -use, in which case it will require soaking in water when required. The -thin tentacles or arms are very convenient for baiting small hooks, -though other parts of the body, cut into narrow strips, will serve the -purpose of the angler equally well. - -Of the crustaceans, shrimps and prawns, and various species of crabs are -used as bait. Shrimps and prawns are used whole for catching flat-fish, -but small pieces are better when fishing for smelt and other small -species of fish that swim close to shore. Little pieces of the flesh of -the crab are also well adapted for baiting hooks of small size, and will -prove very attractive to almost all kinds of fish. Small crabs, however, -may be used whole, but are of little use except when soft--that is, just -after the shedding of their shells, and before the new skin has had time -to harden. Such crabs may be found under stones and in other -hiding-places at low tide, for at such times they keep well secluded -from their numerous enemies by whom they are greedily devoured while in -this helpless and unprotected condition. - -The hermit-crab, which selects the empty shell of a whelk or winkle for -its home, is probably well known to our readers. The protection afforded -by such a home is absolutely necessary to its existence, since its -abdomen has no other covering than a soft, membranous skin. This soft -abdomen is frequently used as a bait with great success, as well as the -flesh of the larger claws. - -If the shell from which the hermit-crab is taken be broken, a worm, -something of the nature of the common ragworm, will almost always be -found, and this also is very serviceable as bait. - -In addition to all the baits previously named there are several other -good ones, many of which are to be obtained almost everywhere. Among -these may be mentioned strips cut from the mackerel, herring, or -pilchard, preferably with a portion of the silvery skin attached; also -thin strips of tripe. Sand-eels, which may be dug out of the sand near -the water's edge, are very useful, and may be cut into pieces for -baiting small hooks. Further, a large number of artificial baits are -employed in various kinds of sea fishing, but as these are not -essential for the work we have in hand we do not propose describing them -in detail. - -Now let us suppose that we are about to try our luck at sea angling, on -some rocky coast, such as that of Devon and Cornwall, our object being -to determine, as far as possible, what species of fishes frequent the -immediate neighbourhood of the shore. And this is not all; for, when -fishing with rod and line on such a coast, it frequently happens that we -land some species of crab that has been attracted to our bait. The -ordinary angler would regard such crab as an intruder, and, we are sorry -to say, would often consider it his duty to crush the unfortunate -crustacean beneath his foot. But it is far different with the -naturalist. He favourably regards all creatures from which something may -be learnt, and is as anxious, as a rule, to gather information -concerning the habitats of one class as of another. In fact, we may go -still further, and combine crab fishing with ordinary angling, both in -one and the same expedition, by letting a small crab-pot down into deep -water among the rocks, and allowing it to remain while the angling is -proceeding. - -We select a spot where there are several feet of water close to a -perpendicular rock, varied and broken by numerous holes and crevices, in -which various species of fishes and crustaceans habitually hide. - -Such a situation is an ideal one for a young naturalist, for not only -does he obtain the greatest variety of species here, but the takings -will surely include some of those remarkably interesting rock-dwelling -fishes that differ from our ordinary food fishes in so many points of -structure, all of which, however, display some interesting adaptation to -the habits and habitats of the species concerned. - -Our apparatus consists of nothing more than rod and line, one or two -small leads, a supply of hooks on gut snoods, a box of bait, and a -waterproof bag in which to pack the specimens we desire to preserve. - -We first determine the depth of the water by means of a lead on the -_end_ of the line, and then tie the hook on the end with a small lead a -few feet above it, and fish in such a manner that the hook is just on -the bottom, or, if the bottom is covered with weeds, the hook should be -kept just clear of fouling them. - -The peculiar rock fishes so common on such a coast as this on which we -are engaged need special treatment at the hands of the angler. They hide -in their holes, watching for the unwary creatures on which they feed, -and, pouncing upon them suddenly, rush back to their snug little nooks -in which they can secure themselves firmly by means of the sharp, hard -spines with which their bodies are furnished. When these fishes seize -the bait offered them--and they are not at all fastidious in the choice -of their viands--they should be hooked and pulled up with one vigorous -sweep of the rod, or they will dart into their homes, from which it is -almost impossible to dislodge them. - - [Illustration: FIG. 32.--FISHING FROM THE ROCKS] - -In addition to these, there will be various other species that require -gentler treatment, and may be hooked and landed much in the same manner -as fresh-water fishes, since they are free swimmers, usually keeping -well clear of the rocks and weeds. - -If the day is calm, and the water clear, the sea angler will often be -able to watch various fishes as they swim, and to bring the bait gently -within their reach; and here we find the advantage of the rod as -compared with the hand line. Sometimes quite a shoal of small fishes may -be seen sporting near the surface, and, as a rule, there will be no -difficulty in obtaining one for identification and study. These are -generally best secured by means of small hooks, with but very little -bait, and will often bite freely at the tiniest fragment of worm on an -almost naked hook. - -After the water has been searched at all depths, it will be well to -allow the bait to rest quite on the bottom, even at the risk of losing a -hook or two in the weeds and rocks. This may enable one to take some -fresh species of fish or to secure a crustacean or other creature that -is not often found between the tide-marks. Care should be always taken, -however, to keep the hook well clear of the weeds that grow on the sides -of the rock, and sway to and fro with every movement of the restless -waters. - -Angling from piers may be pursued much in the same manner as described -above in those places where the bottom is rocky, but since the chances -of hooking large fish are greater here than close to shore, it is -necessary to be provided with stronger tackle and larger hooks. If, -however, the bottom is sandy, the rod tackle may be modified by placing -the lead at the bottom, and arranging two or three hooks above it, about -one or two feet apart, the lowest one being near the lead. With such an -arrangement the line may be cast some distance out, but for angling -close to the pier itself there is, perhaps, nothing better than the -single-hook arrangement suggested above, for with this one may fish on -the bottom and at all depths without any alteration in the tackle being -necessary. - -If, however, the rod line is to be cast as suggested above, or if a hand -line is to be similarly used, the following hints may be useful as -regards the arrangement of hooks and lead. - -The line itself may be of twisted silk or hemp, terminated with about a -yard of strong gut. The lead, preferably of a conical or pear-shaped -form, should be placed at the extreme end, and its weight regulated -according to the necessities of the occasion. A few ounces of lead are -quite sufficient where there are no strong currents, but it is well to -be supplied with larger sizes, to be substituted if circumstances -require it. Two hooks will be ample. One of these should be only a few -inches from the lead, and the other about eighteen or twenty inches -higher. The whole arrangement, known as a Paternoster, is represented in -fig. 33, in which the method of fixing the lead and the hook links is -also illustrated. - - [Illustration: FIG. 33.--THE PATERNOSTER] - -It will be seen that a swivel has been introduced in connection with the -bottom hook, the object being to show the manner in which this useful -piece of tackle is fitted. It must not be supposed, however, that -swivels are always necessary. It is often useful to insert a swivel on -the line itself, above the Paternoster, when it is of twisted material, -in order to prevent it from kinking; but its use is more frequently -serviceable on the hook links, especially when fishing where the -currents are strong. When the bait used is one that presents two flat -surfaces to the water, as would be the case with a strip of mackerel, a -strong current will set it spinning round and round, thus causing the -hook link to kink if it has not been fitted with a swivel, and the same -effect is often produced by the spinning of a fish on the hook. - -The employment of a suitable ground bait will often make a wonderful -difference in the angler's haul. It frequently attracts large numbers, -keeping them near at hand for some considerable time, and apparently -sharpens their appetite. It may be often observed, too, that a fish will -bite freely at the angler's bait when in the neighbourhood of the ground -bait, while the former is viewed with suspicion in the absence of the -latter. - -When fishing on the bottom only, the ground bait should be weighted if -it is of such a nature that it does not sink readily or if it is liable -to be carried away by currents; but it will often be found more -convenient to secure it on the end of a string, tied up in a muslin bag -if necessary, so that it may be adjusted to any desired depth. - -Among the attractive viands suitable for this purpose we may mention -mussels, crushed crabs, pounded liver, the guts of any oily fish, and -the offal of almost any animal. - -Along the east coast, and in some of the sandy bays of Devon and -Cornwall, fishing from the beach is practised, but we can hardly -recommend this as of much value to the amateur whose object is to obtain -as great a variety as possible of fishes for study. Some good food -fishes are often caught by this means, but the methods employed are -often very primitive, and would lack all interest to those who love good -sport. - -On the east coast a long line, fitted with many hooks, is slung out as -far as possible by means of a pole, and the home end either held in the -hand of the fisher or fastened to the top of a flexible stick driven -into the sand. The latter plan becomes necessary when more than one line -is owned by the same individual, and he is made aware of the bite of a -large fish--and a large fish only, since the hooks are placed beyond a -heavy lead--by the bending of the stick. - -The naturalist, however, is as much interested in the small fish as the -large ones, and, even for beach fishing, a rod and line, fitted with one -or two hooks only, and a lead no heavier than is absolutely essential, -will be preferable. A little practice will of course be necessary in -order that one may become expert in the casting of the rod line, but -with large rings on the rod, and a reel without a check, or a check that -can be thrown off when desired, the necessary proficiency in casting -ought to be acquired without much difficulty. - -In some of the sandy bays of the south-west, long lines with a heavy -lead at both ends and baited hooks at short intervals throughout the -whole length, are placed on the sand at low tide close to the water's -edge, and left unwatched until the next tide is out. As far as our -observations go this primitive mode of fishing is usually anything but -successful, the receding of the tide generally revealing a long row of -clean hooks, with, perhaps, one or two dead or half-dead fish; and it is -probable that most of the bait is devoured by crabs and other -crustaceans before the water becomes sufficiently deep to allow the -desired fishes to reach it. - -There is one other method of fishing on which we may make a few remarks, -although it hardly comes under the heading of shore fishing. We refer to -a method of catching surface fishes from a moving boat, which method is -known as whiffing. The line is weighted with a lead which must be -regulated according to the speed of the boat. If the boat is an ordinary -rowing-boat, kept going at only a moderate speed, a few ounces of lead -will be sufficient, but a whiffing line trailing behind a sailing boat -travelling in a good breeze will require a pound or two of lead to keep -the bait only a little below the surface. - -Beyond the lead we have three or four yards of gimp or strong gut, at -the end of which is a single hook fitted with a spinner, or baited with -some attractive natural or artificial bait. Whatever be the bait used, -there will certainly be more or less spinning caused by the resistance -offered by the water, hence it will be necessary to have a swivel beyond -the lead. - -When whiffing near the shore, care must be taken to avoid outlying rocks -that approach the surface of the water, or a sudden snapping of the line -will give you an unwelcome warning of their existence. Further, we -should note that the fishes which are to be caught when whiffing do not -always swim at the same depth, thus it will be advisable to fish at -different distances from the surface by varying either the weight of the -lead or the speed of the boat. - - - - - CHAPTER IV - - _THE MARINE AQUARIUM_ - - -We have already advised our readers to take home their specimens alive -for the purpose of studying their growth and habits. Now, although there -may be some difficulties in the way of keeping marine animals and plants -alive for any considerable time, yet we are inclined to emphasise the -importance of this matter, knowing that the pleasure and instruction -that may be obtained from even a moderately successful attempt to carry -this out will far more than compensate for the amount of trouble -entailed. There are very many marine objects that are exceedingly pretty -and also very instructive, even when studied apart from the life with -which they were associated in the sea. Thus, a well-preserved sea-weed -may retain much of its original beauty of form and colour, the shells of -numerous molluscs and crustaceans exhibit a most interesting variety of -features well worthy of study, and a number of the soft-bodied animals -may be preserved in such a manner as to closely resemble their living -forms. This being the case, we can hardly say anything to discourage -those who gather sea-side objects merely for the purpose of making a -collection of pretty and interesting things to be observed and admired. -Such objects must necessarily afford much pleasure and instruction, and -the time spent in the collection and preparation will certainly cause -the collector to stray to the haunts of the living things, where he is -certain to acquire, though it may be to a great extent unconsciously, a -certain amount of knowledge concerning their habits and mode of life. -Moreover, sea-side collecting is one of the most healthy and -invigorating of all out-door occupations, and for this reason alone -should be encouraged. - -Yet it must be observed that he whose sea-side occupation is merely that -of a collector, and whose work at home is simply the mounting and -arranging of the objects obtained, can hardly be considered a -naturalist. Natural history is a living study, and its devotee is one -who delights in observing the growth and development of living things, -watching their habits, and noting their wonderful adaptation to their -environments; and it is to encourage such observation that we so -strongly recommend the young collector to keep his creatures alive as -far as it is possible to do so. - -The first thing to settle, then, is the nature of the vessel or vessels -that are to serve the purpose of aquaria for the work of the young -naturalist. - -As long as the outdoor work is in progress temporary aquaria will be -very useful as a means by which the objects collected may be sorted and -stored until a final selection is made for the permanent tank. These -temporary aquaria may consist of jars or earthenware pans of any kind, -each containing a few small tufts of weed, preferably attached to pieces -of rock, and a layer of sand or gravel from the beach. - -As such temporary aquaria will, as a rule, be within a convenient -distance from the sea-side where the collecting is being done, there -will be, we presume, no great difficulty in the way of obtaining the -frequent changes of water necessary to keep the animals and plants in a -healthy condition, so that we need do no more now than urge the -importance of avoiding overcrowding, and of renewing the water -frequently for the purpose of supplying the air required for the -respiration of the inmates. - -When it is desired to isolate small species in such a manner that their -movements may be conveniently observed, glass jars answer well; but -whatever be the form or size of the vessels used, care must be taken to -avoid excess of both light and heat. They should be kept in a cool -place, quite out of the way of direct sunshine, and the glass vessels -used should be provided with a movable casing of brown paper to exclude -all light except that which penetrates from above. - -Even temporary aquaria, used merely for the purpose suggested above, -should be carefully watched, for a single day's neglect will sometimes -result in the loss of several valuable captives. A dead animal should be -removed as soon as it is discovered to avoid the unpleasant results -arising from the putrefaction of its body. The appearance of a scum or -film on the surface of the water should always be regarded with -suspicion. Such a scum should be removed with the aid of absorbent -paper, since it tends to prevent the absorption of oxygen from the air; -and, should the water be tainted in the slightest degree, it should be -changed at once, or, if this is not practicable, air should be driven -into it for some time by means of a syringe with a very fine nozzle. -Such precautions, however, are not so urgently needed when the aquarium -contains crustaceans only, for the majority of these creatures suffer -less than others in the tainted sea water, some even being apparently -quite as comfortable in this as in a supply fresh from the sea. -Sea-weeds exhibiting the slightest tendency to decay must be removed at -once; and, as regards the feeding of the animals, one must be careful to -introduce only as much food as is required for immediate use, so that -there be no excess of dead organic matter left to putrefy. Some of the -marine animals obtained from our shores feed entirely on the minute and -invisible organisms that are always present in the sea water, and others -subsist principally on certain of the weeds. Many, however, of a more -predaceous disposition, capture and devour living prey, while some, and -more especially the crustaceans, are partial to carrion. If, therefore, -the observer desires to study the ways in which the various creatures -secure and devour their food, he should introduce into his aquaria live -marine worms and other small animals, and also small pieces of fish or -flesh. - -We will now pass on to the more serious undertaking of the construction -and management of a permanent salt-water aquarium. - -The first point to decide is, perhaps, the size of the proposed vessel, -and this will in many cases be determined partly by a consideration of -the space at one's disposal, and of the apartment it is intended to -occupy. If it is to be placed in a drawing-room or other ordinary -apartment of a dwelling-house, preference should be given to a window -facing the north in order to avoid the direct rays of the sun, but -perhaps no situation is more suitable than a cool conservatory in the -shady part of a garden; and in either case a strong table or other -support should be provided, of a form and size adapted to those of the -aquarium to be constructed. - -Various materials may be used in the construction of such an indoor -aquarium, and we shall deal with two or three different types, so that -the reader may make his selection according to his fancy, or to his -mechanical ability, if he intends that it shall be of his own -construction. - -We will begin with an aquarium constructed entirely of a mixture of -cement and fine sand, this being the most inexpensive and certainly the -easiest to make; and although it may not be regarded as the most -ornamental--but opinions will differ on this point--yet it has the -decided advantage of being the nearest approach to the natural rock -pool. Though somewhat heavy and cumbersome, even when empty, the amount -of material used in its construction may be varied according to the -taste and convenience of the maker. Further, this form of aquarium is -one that will readily admit of structural alterations at any future -period. It may be deepened at any time; lateral additions or extensions -may be made, or a portion may at any time be shut off for the purpose of -isolating certain of the animals procured. - - [Illustration: FIG. 34.--SECTION OF AN AQUARIUM CONSTRUCTED WITH A - MIXTURE OF CEMENT AND SAND] - -The first thing to do is to prepare a flat, strong slab of hard wood or -stone, the exact shape and size of the desired artificial pool, and then -cover this, if of wood, with a mixture of fine sand and cement, mixed to -a convenient consistency with water, to the depth of about one inch. The -banks or walls of the pool must then be built up on all sides, and this -is best done by the gradual addition of soft pellets of cement, applied -in such a manner as to produce an irregular surface. Unless the walls of -the aquarium be very thick and massive the cement will soon show a -tendency to fall from its place as the height increases, but this may be -avoided by doing the work in instalments, allowing each portion to set -before further additions are made to the structure. - -Since some marine animals like to occupy snug and shady niches in deep -water while others prefer full exposure to the light in shallows, -arrangements should be made for all by varying the depth of the bed, and -providing several little tunnels and caverns. This may be accomplished -either by working the cement itself into suitable form, or by means of -piled stones obtained from the sea beach; and if the latter plan is -adopted, the stones should not be obtained until the aquarium is quite -ready for its living contents; for then a selection of stones and rock -fragments with weeds, anemones, sponges, and other fixed forms of life -attached to them, may be made. The natural appearance of a rock pool is -thus more nearly approached, and in a shorter time than if the sedentary -life were required to develop on an artificial ground. - -Objection may be raised to the form of aquarium just described on the -ground that no life within it is visible except when viewed from above. -But is not this also the case with a rock pool on the sea shore? And has -any admirer of nature ever been heard to complain of the beauties of -such a pool because he was unable to look at them through the sides? -Further, it may be urged that the inmates of our aquarium will be living -under more natural conditions than those of the more popular glass-sided -aquaria, _because_ they receive light from above only. - - [Illustration: FIG. 35.--CEMENT AQUARIUM WITH A GLASS PLATE IN FRONT] - -However, should the reader require a glass front to his cement tank, the -matter is easily accomplished. Three sides are built up as before -described. A sheet of thick glass--plate glass by preference--is then -cut to the size and shape of the remaining space, and this is fixed by -means of cement pressed well against its edges, both inside and outside. - -Water should not be put into the tank until it is quite dry; and, if one -side is made of glass, not until the cement surrounding the edge of the -glass has been liberally painted with marine glue, hot pitch, or some -other suitable waterproof material. - -If any pipes are required in connection with the water supply of the -aquarium, according to either of the suggestions in a later portion of -this chapter, such pipes may be fixed in their proper places as the -cement sides are being built up. - -The next type of aquarium we have to describe is of low cost as far as -the materials are concerned, and one that may be made by any one who has -had a little experience in woodwork; and although the tank itself is of -a simple rectangular form, yet it may be made to look very pretty with a -suitable adjustment of rocks and weeds. - -It consists of a rectangular box, the bottom, ends, and back of which -are of hard wood, firmly dovetailed together, and the front of plate -glass let into grooves in the bottom and ends. All the joints and -grooves are caulked with marine glue, but no paint should be used in the -interior. - -This form of tank may be vastly improved by the substitution of slabs of -slate for the wood, though, of course, this change entails a much -greater expenditure of both time and cash; but supposing the work to be -well done, the result is everything that could be desired as far as -strength and durability are concerned. - - [Illustration: FIG. 36.--AQUARIUM OF WOOD WITH GLASS FRONT] - -In either of the rectangular tanks just described glass may be used for -two sides instead of one only; and since this is not a matter of very -great importance, the choice may well be left to the fancy of the one -who constructs it. - -Some prefer an aquarium with glass on all sides, and where this is the -case the framework may be made of angle zinc with all the joints -strongly soldered. Such an aquarium may be made in the form of any -regular polygon, for it is no more difficult to construct one of six or -eight sides than of four. It is more difficult, however, to make such an -aquarium perfectly watertight, for the glass, instead of being in -grooves, has to be securely fastened to the metal frame by means of a -cement on one side only, and this cement has to serve the double purpose -of holding the glass and keeping in the water. - -Various mixtures have been suggested for this purpose, and among them -the following are perfectly satisfactory:-- - - 1. Litharge 2 parts - Fine sand 2 " - Plaster of Paris 2 " - Powdered resin 1 part - -Mix into a very thick paste with boiled linseed oil and a little driers. - - 2. Red lead 3 parts - Fine sand 3 " - Powdered resin 1 part - -Mix with boiled linseed oil as above. - -Both these cements should be applied very liberally, and the aquarium -then allowed to remain quite undisturbed for at least two weeks before -any water is introduced. - - [Illustration: FIG. 37.--HEXAGONAL AQUARIUM CONSTRUCTED OF ANGLE ZINC, - WITH GLASS SIDES] - -When ready for the water, the bottom of the aquarium should be covered -with a moderately thick layer of fine sand from the sea shore, and -stones then piled in such a manner as to form little tunnels and caves -to serve as hiding-places for those creatures that prefer to be under -cover. As to the selection of stones, we have already suggested that -some may have weeds rooted to them, and that pieces of rock with -anemones, sponges, and other forms of life attached may be chipped off. -Further, on many of our rocky coasts we may find, near low-water mark, a -number of stones covered with a layer of vegetable growth, amongst which -many small animals live, often more or less concealed by their -protective colouring. Some of these stones placed on the bed of the -salt-water aquarium would add greatly to the natural appearance, as well -as give greater variety to the living objects. Shells bearing the -calcareous, snakelike tubes of the common serpula (p. 121), preferably -with the living animals enclosed, will also enhance the general -appearance and interest of the aquarium. - -In making preparations previous to the introduction of animal life, due -regard should be paid to the peculiar requirements of the creatures it -is intended to obtain. We have already referred to the advisability of -arranging the bed of the tank in such a manner that the water may vary -considerably in depth, so that both deep and shallow water may be found -by the animals as required, and to the provision of dark holes for -crustaceans and other creatures that shun the light. Very fine sand -should be provided for shrimps, prawns, and other animals that like to -lie on it; and this sand must be deep in places if it is intended to -introduce any of the burrowing molluscs and marine worms. - -The water used may be taken from the sea or be artificially prepared. -The former is certainly to be preferred whenever it can be conveniently -obtained, and at the present time few will find much difficulty in -securing a supply, for not only are we favoured with the means of -obtaining any desired quantity by rail at a cheap rate from almost any -seaport, but there are companies in various ports who undertake the -supply of sea water to any part of the kingdom. If the water is to be -conveyed from the coast without the aid of the regular dealers in this -commodity, great care must be taken to see that the barrel or other -receptacle used for the purpose is perfectly clean. Nothing is more -convenient than an ordinary beer or wine barrel, but it should be -previously cleansed by filling it several times with water--not -necessarily sea water--and allowing each refill to remain in it some -time before emptying. This must be repeated as long as the water shows -the slightest colouration after standing for some time in the barrel. - -Should any difficulty arise in the way of getting the salt water direct -from the sea, it may be made artificially by dissolving 'sea salt' in -the proper proportion of fresh water, or even by purchasing the -different salts contained in the sea separately, and then adding them to -fresh water in proportionate quantities. - -The composition of sea water is as follows:-- - - Water 96·47 per cent. - Sodium chloride 2·70 " - Magnesium chloride ·36 " - Magnesium sulphate (Epsom salts) ·23 " - Calcium sulphate ·14 " - Potassium chloride ·07 " - Traces of other substances ·03 " - 100·00 - -and it will be seen from this table that artificial sea water may be -made by adding about three and a half pounds of sea salt, obtained from -the sea by the simple process of evaporation, to every ninety-six and a -half pounds of fresh water used. In making it there may be some -difficulty in determining the weight of the large volume of water -required to fill an aquarium of moderate dimensions, but this will -probably disappear if it be remembered that one gallon of water weighs -just ten pounds, and, therefore, one pint weighs twenty ounces. - -If the sea salt cannot be readily obtained, the following mixture may be -made, the different salts being purchased separately:-- - - Water 96-1/2 lbs. - Sodium chloride (common salt) 43-1/4 ozs. - Magnesium chloride 5-3/4 " - Epsom salts 3-3/4 " - Powdered gypsum (calcium sulphate) 2-1/4 " - -Although in this mixture the substances contained in the sea in very -small quantities have been entirely omitted, yet it will answer its -purpose apparently as well as the artificial sea water prepared from the -true sea salt, and may therefore be used whenever neither sea salt nor -the natural sea water is procurable. - -Assuming, now, that the aquarium has been filled with sea water, it -remains to introduce the animal and vegetable life for which it is -intended; and here it will be necessary to say something with regard to -the amount of life that may be safely installed, and the main conditions -that determine the proportion in which the animal and vegetable life -should be present in order to insure the greatest success. - -Concerning the first of these we must caution the reader against the -common error of overcrowding the aquarium with animals. It must be -remembered that almost all marine animals obtain the oxygen gas required -for purposes of respiration from the air dissolved in the water. Now, -atmospheric air is only very slightly soluble in water, and hence we can -never have an abundant supply in the water of an aquarium at any one -time. If a number of animals be placed in any ordinary indoor aquarium, -they very soon use up the dissolved oxygen; and, if no means have been -taken to replace the loss, the animals die, and their dead bodies soon -begin to putrefy and saturate the water with the poisonous products of -decomposition. - -It is probably well known to the reader that a large proportion of the -oxygen absorbed by the respiratory organs of animals is converted by -combination of carbon into carbonic acid gas within their bodies, and -that this gas is given back into the water where it dissolves, thus -taking the place of the oxygen used in its formation. - -If, then, an aquarium of any kind is to be a success, some means must be -taken to keep the water constantly supplied with fresh oxygen quite as -rapidly as it is consumed, and this can be done satisfactorily by the -introduction of a proportionate quantity of suitable living weeds, -providing there is not too much animal life present. - -The majority of living plants require carbonic acid gas as a food, and, -under the influence of light, decompose this gas, liberating the oxygen -it contained. This is true of many of our common sea-weeds, and thus it -is possible to establish in a salt-water aquarium such a balance of -animal and vegetable life that the water is maintained in its normal -condition, the carbonic acid gas being absorbed by the plants as fast as -it is excreted by animals, and oxygen supplied by the plants as rapidly -as it is consumed by the animals. - -This condition, however, is more difficult to obtain in a salt-water -aquarium than in one containing fresh-water life, partly because, -generally speaking, the sea-weeds do not supply oxygen to the water as -rapidly as do the plants of our ponds and streams, and partly because of -the difficulties attending the successful growth of sea-weeds in -artificial aquaria. Thus it is usually necessary to adopt some means of -mechanically aërating the water; but, for the present, we shall consider -the sea-weeds only, leaving the mechanical methods of aërating the water -for a later portion of this chapter. - -In the first place, let us advise the amateur to confine his attention -to the smaller species of weeds that are commonly found in small and -shallow rock pools, for the successful growth of the larger purple and -olive weeds will probably be beyond his power, even though his tank be -one of considerable capacity. The best plan is that we have already -suggested--namely, to chip off small pieces of rock with tufts of weed -attached, and to fix them amongst the rockery of the aquarium, being -careful to place those that grew in shallow water with full exposure to -the light, and those which occupied sheltered and shady places in the -rock pool, respectively, in similar situations in the artificial pool. - -For the purposes of aëration we have to rely principally on the bright -green weeds, and preference should be given to any of these that -exhibit, in their natural habitat, a multitude of minute air-bubbles on -the surface of their fronds, for the bubbles consist principally of -oxygen that is being liberated by the plant, and denote that the species -in question are those that are most valuable for maintaining the desired -condition of the water in an aquarium. - -Any small sea-weed may be tried at first, but experience will soon show -that some are much more easily kept alive than others. In this -experimental stage, however, a constant watch should be maintained for -the purpose of detecting signs of decay in the marine garden. A plant -should always be removed as soon as it presents any change from the -natural colour, or exhibits the smallest amount of slimy growths on the -surface, for decomposing plants, as well as decaying animals, will soon -convert an aquarium into a vessel of putrid and poisonous water. - -It seems almost unnecessary to name a selection of sea-weeds for small -aquaria, seeing that our rock pools produce so many extremely beautiful -species, most of which may be successfully kept alive in a well-managed -tank; but the common Sea Grass (_Enteromorpha compressa_), and the Sea -Lettuce (_Ulva latissima_), also known locally as the Green Laver or -Sloke, are particularly useful for the aëration of the water; while the -Common Coralline (_Corallina officinalis_), the Dulse (_Schizymenia -edulis_), the Peacock's tail (Padina pavonia), the Irish or Carrageen -Moss (_Chondrus crispus_), _Callithamnion_, _Griffithsia setacea_, -_Plocamium plumosium_, _Rhodymenia palmata_, _Rhodophyllis bifida_, and -_Ceramium rubrum_ are all beautiful plants that ought to give no trouble -to the aquarium-keeper. - -It is not advisable to introduce animal life into the aquarium -immediately it is filled, on account of the possibility of the water -being contaminated by contact with the cement that has been used to make -it water-tight. It is safer to allow the first water to stand for a few -weeks, the weeds and all other objects being _in situ_, and the -necessary means employed for perfect aëration during this interval, and -then, immediately before the animals are placed in their new home, to -syphon off the whole of the water, and refill with a fresh supply. - -In the selection of animals due regard should be paid to two important -points--first, the danger of overcrowding, and, secondly, the -destructive habits of some of the more predaceous species. - -No more than two or three animals should, as a rule, be reckoned for -each gallon of water; and the proportion of animals should be even less -than this when any of them are of considerable size. - -As regards the destructive species, these are intended to include both -those that are voracious vegetable feeders and also those whose habit it -is to kill and prey on other creatures. - -It must be understood that the weeds are to serve two distinct -purposes:--They are to supply at least some of the oxygen required for -the respiration of the animal inmates, and also to serve as food for -them. Some marine fishes and molluscs feed on the fronds of the weeds, -and among these the common periwinkle may be mentioned as one of the -most voracious. If many such animals are housed in the aquarium, it will -be necessary to replace at intervals those species of weeds that suffer -most from their ravages. The zoospores thrown off by the weeds, -particularly in the autumn, are also valuable as food for some of the -animals. - -Notwithstanding the destructive character of the periwinkle just -referred to, it has one redeeming feature, for it is certainly useful in -the aquarium as a scavenger, as it greedily devours the low forms of -vegetable life that cover the glass and rocks, thus helping to keep them -clean; and the same is true of the common limpet and other creeping -molluscs. Some of these are even more to be valued on account of their -partiality for _decaying_ vegetable matter, by devouring which they -reduce the amount of the products of decomposition passing into the -water. - -Other details concerning the selection of animal and vegetable life for -the indoor aquarium must be left to the discretion and experience of the -keeper, for it is impossible by written instructions and advice to cover -all the various sources of loss and trouble that may from time to time -arise. If, however, the general hints for the management of the marine -aquarium here given be faithfully followed, there ought to be no further -losses than must accrue from the injudicious selection of animal -species, and these will decrease as experience has been acquired -respecting the habits of the creatures introduced. - -We must now pass on to matters pertaining to the maintenance of the -healthy condition of an aquarium which, we will suppose, has been -established with due regard to scientific principles. Under this head we -shall consider, (1) the aëration of the water, (2) the repair of loss -due to evaporation, and (3) the regulation of light and temperature. - -It has already been shown that the marine aquarium can hardly be -maintained in a satisfactory condition as regards its air supply by -leaving the aëration of the water entirely to the action of plant life; -and herein this form of aquarium differs from that employed for the -animal and vegetable life derived from ponds and streams. Fresh-water -weeds develop and multiply with such rapidity, and are such ready -generators of oxygen gas that it is a very easy matter to establish a -fresh-water aquarium that will remain in good condition for years with -but little attention; it is therefore important that we should point out -the difference in treatment necessary to those of our readers who are -already acquainted with the comparative ease with which the fresh-water -aquarium may be kept in good order, lest they expect the same -self-aërating condition in the marine tank. - -It is never a good plan to leave the renovation of the water of the -aquarium until there are visible signs within that something is going -wrong. It is true that an unsatisfactory condition of the water, -revealed by a slight taint in the odour, or a general turbidity, or the -formation of a slight scum on the surface, may sometimes be rectified by -the prompt application of some method of artificial aëration, but the -aim of the aquarium-keeper should be not the rectification of -unsatisfactory conditions, but the establishment of such a method of -aëration that the unsatisfactory condition becomes an impossibility. We -do not wish to discourage anyone who has the slightest desire to start a -marine aquarium. Our aim is to point out any difficulties that lie in -the way in order that the aquarium may be a success; and thus, having -stated that the difficulties attending it are somewhat greater than -those connected with the management of a fresh-water aquarium, we should -like to add that these practically disappear when one is prepared to -devote a short time at regular intervals in order to see that the -process of aëration is properly carried out. - -Some recommend the occasional injection of air by a syringe as one means -of aërating the water; but, although this may be all very well as a -_temporary_ purifier of the slightly tainted aquarium, it is hardly -suitable as a means of maintaining a good, healthy condition. It must be -remembered that oxygen gas--the gas of the atmosphere so essential to -animal life--is only very slightly soluble in water. By this we mean not -only that water dissolves oxygen very slowly, but also that it can never -hold a large supply of the gas at any one time. This being the case, it -is clear that the use of a syringe for a short time, though it -discharges an enormous total volume of air into the water, will result -in the actual solution of only a small quantity. No method of aëration -is perfect that allows the admission of air for a short time only at -comparatively long intervals; the most perfect system is that in which -air is slowly but _continuously_ passed into solution. - -Since air is slightly soluble in water, it is clear that it must be -continuously passing into any body of water that has its surface freely -exposed to it; hence a wide and shallow aquarium is much more likely to -keep in good order than one that is narrower and deeper. But, with -marine aquaria, the simple absorption from the air at the surface is not -in itself sufficient, as a rule, to maintain a healthy condition. Yet it -will be advisable to remember this matter when constructing a tank for -marine life. - -One of the prettiest, and certainly one of the most effectual, methods -of supplying air to an aquarium is by means of a small fountain with a -very fine spray. The water need seldom be changed, but the fountain may -be fed by water from the aquarium, and as the fine spray passes through -the air it will absorb oxygen and carry it in solution to the tank. - -The accompanying diagram illustrates the manner in which this can be -accomplished. The aquarium (A) is supplied with an outlet (O) about an -inch from the top by means of which the water is prevented from -overflowing, and the outlet pipe leads to a vessel (V) of considerable -capacity which, for the sake of convenience and appearance, may be -concealed beneath the table on which the aquarium stands. Some feet -above the level of the aquarium is another vessel (C), supported on a -shelf, having about the same capacity as V, and supplied with a small -compo pipe that passes down into the aquarium, and then, hidden as much -as possible by the rockery, terminates in a very fine jet just above the -level of the water in the centre. The upper vessel should also be -provided at the top with a loose covering of muslin to serve as a -strainer, and this should be replaced at intervals as it becomes clogged -with sedimentary matter. - -In order that this arrangement may give perfect satisfaction the two -vessels (C and V) must each be of at least half the capacity of the -aquarium itself, and the total quantity of salt water sufficient to fill -the aquarium together with one of them. It should also be remembered -that since the pressure of water depends not on its quantity, but on its -height measured perpendicularly, it follows that the height to which the -fountain will play is determined by the height of the vessel C above the -level of the jet. - - [Illustration: FIG. 38.--METHOD OF AËRATING THE WATER OF AN AQUARIUM - A, aquarium with fountain; C, cistern to supply the fountain; - O, pipe for overflow; V, vessel for overflow] - -Let us now suppose that the aquarium and the upper vessel have both been -filled with sea water. The fine jet from the pipe plays into the air and -returns with a supply of oxygen to the aquarium, while the excess above -the level of O passes into the concealed vessel below the table. If the -two vessels are as large as we recommend, and the jet a very fine one, -the fountain may continue to play for hours before C is empty, the -animals of the tank being favoured all this time with a continuous -supply of air. And when the supply from above is exhausted, the contents -of the bottom vessel are transferred to the top one, and at the same -time so effectually strained by the layer of muslin that no sedimentary -matter passes down to choke the fine jet of the fountain. One great -advantage this method possesses is that the living creatures derive the -benefit of a much larger quantity of water than the aquarium alone could -contain; and thus, apart from the aërating effects of the fountain, the -result is the same as if a much larger tank were employed. - -In our next illustration (fig. 39) we give a modified arrangement based -on the same principle which may commend itself by preference to some of -our readers. Here the supply pipe to the fountain passes through a hole -in the bottom of the aquarium instead of into the top, and the outlet -pipe is bent downward within so as to form a syphon. - -Those who are acquainted with the principle of the syphon will -understand at once the working of such an arrangement as this. Let us -suppose the vessel _c_ to be full of water, and the fountain started, -while the water in the aquarium stands no higher than the level _l_. The -water slowly rises until the level _h_ of the bend of the outlet tube -has been reached, and during the whole of this time no water escapes -through the exit. As soon, however, as the latter level has been -attained, the water flows away into the lower vessel, into which it -continues to run until the lower level is reached, and then the outflow -ceases, not to commence again until the fountain causes the water to -rise to the upper level. - -From what has been said the reader will see that the total quantity of -water required in this instance need not exceed the capacity of the -aquarium; also that each of the vessels connected with water supply and -waste should have a capacity equivalent to the volume of water contained -in the aquarium between the two levels _h_ and _l_. - -The alternate rising and falling of the water produced in the manner -just described represents in miniature the flow and ebb of the tides, -but perhaps this is in itself of no great advantage in the aquarium -except from the fact that it allows those creatures that prefer to be -occasionally out of the water for a time a better opportunity of -indulging in such a habit. And further, with regard to both the -arrangements for aëration above described, it should be noted that -earthenware vessels are much to be preferred to those made of metal for -the holding of sea water, since the dissolved salts corrode metallic -substances rather rapidly, and often produce, by their chemical action, -soluble products that render the water more or less poisonous. - - [Illustration: FIG. 39.--AQUARIUM FITTED WITH APPARATUS FOR PERIODIC - OUTFLOW] - -Other methods of aërating the water of aquaria are practised, but these, -as a rule, are only practicable in the case of the large tanks of public -aquaria and biological laboratories, as the mechanical appliances -necessary to carry them out successfully are beyond the means of an -ordinary amateur. - -In such large tanks as those referred to it is common to force a fine -jet of air into the water by machinery. Sometimes this air is driven -downward from a jet just below the surface, and with such force that a -multitude of minute bubbles penetrate to a considerable depth before -they commence to rise, but in others the air is made to enter at the -bottom and must therefore pass right through the water. - -Of course the amateur aquarium-keeper may carry out this method of -aëration with every hope of success providing he has some self-acting -apparatus for the purpose, or can depend on being able himself to attend -to a non-automatic arrangement at fairly regular intervals, always -remembering that a single day's neglect, especially in the case of a -small tank with a proportionately large amount of animal life, may lead -to a loss of valuable specimens. - -We have already mentioned the use of a syringe as a means by which an -aquarium may be temporarily restored to a satisfactory condition -providing it has not been neglected too long, and some recommend forcing -air, or, still better, pure oxygen gas, from an india-rubber bag into -the water. We have used, for the same purpose, a stream of oxygen from a -steel cylinder of the compressed gas with very satisfactory results; and -since oxygen may be now obtained, ready compressed, at a very low -price--about twopence a cubic foot--there is much to be said in favour -of this method as an auxiliary in the hands of the owner of a small -tank, though we hardly recommend it as a prime means of aëration to take -the place of the fountain. - -In any case, where a stream of air or oxygen is employed, an exceedingly -fine jet should be used, in order that the expelled gas may take the -form of a stream of minute bubbles; for, as previously stated, the water -can absorb the gas only very slowly, so that there must necessarily be a -considerable waste when the gas issues rapidly. Further, the smaller the -bubbles passing through the water, the greater is the total surface of -gas in contact with the liquid, the volume of the supply being the same, -and hence the more effectually will the solution of the gas proceed. -Again, another advantage of the fine stream of minute bubbles lies in -the fact that the smaller these bubbles are the more slowly they rise to -the surface of the water, and thus the longer is the time in which the -gas may be absorbed during its ascent. - -A fine jet, well suited to the purpose here defined, may be made very -easily by holding the middle of a piece of glass tubing in a gas flame -until it is _very_ soft, and then, immediately on removing it, pulling -it out rather quickly. A slight cut made with a small triangular file -will then enable the operator to sever the tube at any desired point. - -Yet another method of maintaining the air supply of aquaria is adopted -in the case of some of the large tanks of public aquaria and biological -laboratories situated close to the sea, and this consists in renewing -the water at every high tide by means of pumps. - -It must not be supposed that an indoor aquarium, even when well -established, and supplied with the best possible system of aëration, -requires no further care and attention. In the first place there is a -continual loss of water by evaporation, especially in warm and dry -weather, and this must be rectified occasionally. Now, when water -containing salts in solution evaporates, the water passing away into the -air is perfectly free from the saline matter, and thus the percentage of -salt in the residue becomes higher than before. It is evident, -therefore, that the loss by evaporation in a marine aquarium must be -replaced by the addition of _fresh_ water, which should either be -distilled, or from the domestic supply, providing it is soft and -moderately free from dissolved material. - -But the question may be asked, 'Do not the marine animals and plants -utilise a certain amount of the saline matter contained in the salt -water?' The answer to this is certainly in the affirmative, for all -sea-weeds require and abstract small proportions of certain salts, the -nature of which varies considerably in the case of different species; -and, further, all the shelled crustaceans and molluscs require the salts -of lime for the development of their external coverings, and fishes for -the growth of their bony skeletons. Hence the above suggestion as to the -replenishment of loss by evaporation with pure water is not perfectly -satisfactory. It will answer quite satisfactorily, however, providing -the sea water is _occasionally_ changed for an entirely new supply. -Again, since carbonate of lime is removed from sea water more than any -other salt, being such an essential constituent of both the external and -internal skeletons of so many marine animals, as well as of the -calcareous framework of the coralline weeds, we suggest that the -aquarium may always contain a clean piece of some variety of carbonate -of lime, such as chalk, limestone, or marble, which will slowly dissolve -and replace that which has been absorbed. - -Water is rendered denser, and consequently more buoyant, by the presence -of dissolved salts; and, since the density increases with the proportion -of dissolved material, we are enabled to determine the degree of -salinity by finding the density of the solution. We can apply this -principle to the aquarium, as a means of determining whether the water -contains the correct amount of sea salt, also for testing any artificial -salt water that has been prepared for the aquarium. - -Probably some of our readers are acquainted with some form of -hydrometer--an instrument used for finding the density of any liquid; -but we will describe a simple substitute that may be of use to the owner -of a marine aquarium, especially if the salt water for the same is -artificially prepared. Melt a little bees-wax, and mix it with fine, -clean sand. Then, remembering that the wax is lighter than water, and -consequently floats, while sand is considerably heavier, and sinks, -adjust the above mixture until a solid ball of it is just heavy enough -to sink _very slowly_ in sea water. Now make two such balls, and then -cover one of them with a light coating of pure wax. We have now two -balls, one of which will float in sea water, and the other sink, and -these may be used at any time to test the density of the water in, or -prepared for, the aquarium. If the water is only a little too salt, both -balls will float; while, if not sufficiently rich in saline matter, both -will sink. - -We must conclude this chapter by making a few remarks on the important -matter of the regulation of light and temperature. Direct sunlight -should always be avoided, except for short and occasional intervals, not -only because it is liable to raise the temperature to a higher degree -than is suitable for the inmates of the aquarium, but also because an -excess of light and heat tends to produce a rapid decomposition of -organic matter, and a consequent putrid condition of the water, and this -dangerous state is most likely to occur when both light and temperature -are high at the same time. - -The water should always be cold; and as it is not always easy to -estimate the temperature, even approximately, by the sensation produced -on immersing the fingers, it is a good plan to have a small thermometer -always at hand, or placed permanently in the aquarium. In the summer -time the water should be kept down to fifty-five degrees or lower, and -in winter should never be allowed to cool much below forty. There may be -some difficulty in maintaining a temperature sufficiently low in summer, -but a small piece of ice thrown in occasionally to replace the loss due -to evaporation, especially on very hot days, will help to keep it down. - - - - - CHAPTER V - - _THE PRESERVATION OF MARINE OBJECTS_ - - -The sea-side naturalist, in the course of his ramblings and searchings -on the coast, will certainly come across many objects, dead or alive, -that he will desire to set aside for future study or identification in -his leisure moments at home. Some of these will be required for -temporary purposes only, while, most probably, a large proportion will -be retained permanently for the establishment of a private museum, that -shall serve not only as a pleasant reminder of the many enjoyable hours -spent on the shore, but also as a means of reference for the study of -the classification of natural objects and of their distribution and -habitats. - -We will first deal with those specimens that are required for temporary -purposes only--those of which the collector desires to study the general -characters, as well as, perhaps, something of the internal structure; -but before doing so we cannot refrain from impressing on the reader the -advisability of learning as much as possible of the external features -and mode of growth of the different living creatures while still alive, -for it must be remembered that it is impossible to preserve many of them -without more or less destruction of their natural colouring and -distortion of their characteristic forms. - -In those cases where it is possible to keep the creatures alive for a -short time only, it is a good plan to make notes of their movements and -all observed changes in form, and their methods of feeding, and also to -illustrate these notes by sketches drawn from life. This may seem quite -an unnecessary procedure to many beginners in the study of natural -objects, and may even, as far as the sketches are concerned, present -difficulties that at first appear to be insurmountable; but the power to -sketch from nature will surely be acquired to a greater or less degree -by constant practice, and illustrated notes prepared for the purpose we -suggest will undoubtedly be of great value to the student. Further, -though it may often be necessary to set specimens aside in a -preservative fluid until one has the leisure to examine their structure, -it should always be remembered that they never improve by keeping, also -that they are rarely in such good condition for dissection after -saturation with the preservative as when perfectly fresh. - -One of the most convenient preservatives for general use is undoubtedly -methylated spirit. This is alcohol that has been adulterated in order to -render it undrinkable, so that it may be sold free from duty for use in -the various arts and manufactures without any danger of its being -employed for the concoction of beverages. It may be used just as -purchased--that is, in its strongest condition--for many purposes, but -in this state it has a powerful affinity for water, and will rapidly -abstract water from animal and vegetable objects, causing the softer -ones to become hard, shrunken, and shrivelled, often to such an extent -that they are almost beyond recognition. - -By diluting the spirit, however, we satisfy to a great extent its -affinity for water, and thus prevent, or, at least, reduce the action -just mentioned. A mixture of equal quantities of spirit and water is -quite strong enough. Unfortunately the common methylated spirit of the -shops produces a fine white precipitate, that gives the whole mass a -milky appearance, when it is diluted. This is due to the presence of -mineral naphtha, which is added in a certain fixed proportion in -accordance with the Government regulations. But it _is_ possible, by -special application, to obtain the 'non-mineralised' or 'ordinary' -methylated spirit of former years, though not in small quantities, and -this liquid dissolves in water without the formation of a precipitate. -It should be noted, however, that the use of the spirit as a -preservative is in no way interfered with by the presence of the mineral -naphtha, the only disadvantage of this impurity lying in the fact that -the milkiness consequent on dilution prevents the objects in a specimen -jar from being observed without removal. - -We have just referred to the hardening action of strong spirit as a -disadvantage, and so it is when it is required to preserve soft -structures with as little as possible of change in general form and -appearance; but there are times when it becomes necessary to harden -these soft structures in order that sections may be made for the purpose -of examining internal structure with or without the aid of the -microscope, and for such purposes strong spirit is one of the best -hardening agents that can be employed. - -Formaldehyde is another very good preservative. It is a colourless -liquid, and should be considerably diluted for use, a two per cent. -solution being quite strong enough for all ordinary purposes. It -possesses some distinct advantages as compared with spirit. In the first -place, it does not destroy the natural colours of objects to the extent -that spirit does; and, although a hardening agent as well as a -preservative, it does not harden soft structures by the extraction of -the water they contain, and therefore does not cause them to become -shrivelled or otherwise distorted. It will also occur to the reader -that, since a small bulk of formaline represents a large volume of the -diluted preservative, it is very conveniently stored, and a very small -bottle of it taken for outdoor work may, on dilution with water, be made -to yield all that is required for the preservation of the takings of a -successful day, or even of a longer period. Formaldehyde is usually sold -in solution of about forty per cent. strength, and for the preparation -of a two per cent. solution it will be found convenient to provide a -glass measure graduated either into cubic centimetres or fluid ounces -and drams. One hundred volumes of the original solution contain forty of -pure formaldehyde, and if water be added to make this up to two thousand -volumes, a two per cent. solution is obtained. Thus, one hundred cubic -centimetres of the original solution is sufficient to prepare two litres -(three and a half pints) of suitable preservative. - -A very good preservative liquid may be made by dissolving two ounces of -common salt, one ounce of alum, and two or three grains of corrosive -sublimate (a deadly poison) in one quart of water, and then, after -allowing all sedimentary matter to settle to the bottom, decanting off -the clear solution. This mixture is known as _Goadby's fluid_, and is -well adapted for the preservation of both animal and vegetable -structures. It does not cause any undue contraction of soft tissues, -and, as a rule, does not destroy the natural colours of the objects kept -in it. - -Glycerine is valuable as a preservative for both animal and vegetable -objects, and especially for the soft-bodied marine animals that form -such a large percentage of the fauna of our shores. It maintains the -tissues in a soft condition, and preserves the natural tints as well as -any liquid. - -An inexpensive preservative may also be made by dissolving chloride of -zinc--about one ounce to the pint of water. This is considered by some -to be one of the best fluids for keeping animal structures in good -condition. - -Now, although the different fluids here mentioned are described in -connection with the _temporary_ preservation of natural objects, it must -be remembered that they are equally adapted for the permanent -preservation of the animals and plants that are to figure in the museum -of the sea-side naturalist; and, although some marine objects may be -preserved in a dry state in a manner to be hereafter described, yet -there are many species of animals, and also some plants, that can be -satisfactorily preserved only by immersion in a suitable fluid. - -This method may be applied to all soft-bodied animals, such as anemones, -jelly-fishes, marine worms, shell-less molluscs (sea slugs, cephalopods, -&c.), the soft parts of shelled molluscs, fishes, &c.; and most sponges -retain their natural appearance much better in a preservative fluid than -in a dry condition. Many sea-weeds also, which are practically destroyed -by the most careful drying process, are most perfectly preserved in -fluid. - -But the puzzled amateur will probably be inclined to ask: 'Which is the -best preservative liquid for this or that specimen?' No satisfactory -general rule can be given in answer to such a question, and a great deal -will have to be determined by his own experiments and observations. -Whenever he has two or three specimens of the same object, as many -different fluids should be employed, and the results compared and noted. -In this way a very great deal of useful information will be obtained and -by the best possible means. However, it may be mentioned that all the -fluids alluded to above may be safely used for almost every animal or -vegetable specimen with the following reservations: strong spirit should -not be employed for _any_ very soft animal, nor should it be used for -delicate green plants, since it will dissolve out the green colouring -matter (_chlorophyll_), leaving them white or almost colourless. -Further, the greatest care should be exercised in dealing with sea -anemones and jelly-fishes. If spirit is used for preserving these -creatures, it should be very dilute, at least at first, but may with -advantage be increased in strength afterwards, though this should be -done gradually. - -Whatever be the preservative used, it is sure to be more or less charged -with sedimentary and coloured matter extracted from the object immersed -in it; hence, if the specimen concerned is to form part of a museum -collection, it will be necessary to transfer it to a fresh solution -after a time, and a second, and even further changes may be necessary -before the object ceases to discolour the fluid or render it turbid. - -Considerable difficulty will sometimes be found in the attempts to -preserve a soft-bodied animal in its natural attitude. Thus, when a sea -anemone is removed from its native element, it generally withdraws its -tentacles, and, contracting the upper part of its cylindrical body, -entirely conceals these appendages, together with the mouth they -surround; and a mollusc similarly treated will generally pull itself -together within its shell, leaving little or no trace of the living body -inhabiting the lifeless case. Then, if these animals are transferred to -any fluid other than sea water, or placed anywhere under unnatural -conditions, they usually remain in their closed or unexpanded form. -Thus, almost every attempt to kill them for preservation deprives them -of just the characteristics they should retain as museum specimens. - -Some such animals may be dealt with satisfactorily as follows: Transfer -them to a vessel of fresh sea water, and leave them perfectly -undisturbed until they assume the desired form or attitude. Then add a -_solution_ of corrosive sublimate very gradually--a drop or two at -intervals of some minutes. In this way the bodies of anemones may be -obtained ready for preservation with expanded tentacles, tube-secreting -worms with their heads and slender processes protruding from their limy -or sandy cases, molluscs with their 'feet' or their mantles and gills -protruding from their shells, and barnacles with their plume-like -appendages projecting beyond the opening of their conical shells. - -The specimens thus prepared may be placed at first in very dilute -spirit, and then, after a time, finally stored in a stronger solution of -spirit in water; or they may be transferred to one of the other -preservative solutions previously mentioned. - -All specimens permanently preserved in fluid for a museum should be -placed in jars, bottles, or tubes of suitable size, each vessel -containing, as a rule, only one. Where expense is no object, stoppered -jars made expressly for biological and anatomical specimens may be used -for all but the smallest objects; or, failing this, ordinary -wide-mouthed bottles of white glass, fitted with good corks or glass -stoppers. - -For very small specimens nothing is more suitable than glass tubes, but -it must be remembered that wherever corks are used, even if they are of -the best quality procurable, it will be necessary to look over the -specimens occasionally to see if the preserving fluid has disappeared to -any extent either by leakage or evaporation; for such loss is always -liable to occur, although it may be very slow, and especially when -methylated spirit is the liquid employed. - - [Illustration: FIG. 40.--JARS FOR PRESERVING ANATOMICAL AND BIOLOGICAL - SPECIMENS] - -The writer has preserved many hundreds of small marine and other objects -in glass tubes of dilute spirit that have been hermetically sealed, thus -rendering the slightest loss absolutely impossible, while the perfect -exclusion of air prevents the development of fungoid growths that -sometimes make their appearance in imperfectly preserved specimens. The -making and closing of such tubes, though a more or less difficult -operation at first to those who have had no previous experience in -glass-working, become exceedingly simple after a little practice; and -believing it probable that many of our readers would like to try their -hand at this most perfect method of preserving and protecting small -objects, we will give a description of the manner in which it is done. - -The apparatus and materials required for this work are:--Lengths of -'soft' glass tubing, varying from about one quarter to a little over -half an inch in internal diameter; a supply of diluted spirit--about -half spirit and half water; a Herapath blowpipe, preferably with -foot-bellows; and a small triangular file. - -The glass tubing may be cut into convenient lengths by giving a single -sharp stroke with the file, and then pulling it apart with, at the same -time, a slight bending _from_ the cut made. - - [Illustration: FIG. 41.--SHOWING THE DIFFERENT STAGES IN THE MAKING OF - A SMALL SPECIMEN TUBE] - -Cut a piece of tubing about eight or nine inches long, heat it in the -blowpipe flame, turning it round and round all the time, until it is -quite soft, then remove it from the flame and immediately pull it out -_slowly_ until the diameter in the middle is reduced to about a -sixteenth of an inch (fig. 41, 2). Make a slight scratch with the file -at the narrowest part, and divide the tube at this point (fig. 41, 3). -Now heat one of these pieces of tubing as before just at the point where -the diameter of the drawn part begins to decrease; and, when very soft, -pull it out rather quickly while it is _still in the flame_. The part -pulled now becomes completely separated, and the tube is closed, but -pointed. Continue to heat the closed end, directing the flame to the -point rather than to the sides, until the melted glass forms a rather -thick and flattened end; and then, immediately on removing it from the -flame, blow gently into the open end until the melted glass is nicely -rounded like the bottom of a test-tube (fig. 41, 4). When the tube is -cold, the specimen that it is to contain, and which has already been -stored for a time in dilute spirit, is dropped into it. The tube is now -heated about an inch above the top of the specimen, drawn out as shown -in fig. 41, 5, and again allowed to cool. When cold, the fresh spirit is -poured into the open end of the tube, but the middle part is so narrow -that the spirit will not run down freely. If, however, suction be -applied to the open end, air from the bottom will bubble through the -spirit, and then, on the cessation of the suction, the spirit will pass -down to take the place of the air that was withdrawn. This may be -repeated if necessary to entirely cover the specimen with the fluid. Any -excess of spirit is then thrown from the upper part of the tube, and the -latter cut off. Nothing is now left but to close the tube hermetically. -This is done by heating the lower part of the narrow neck, and then -drawing it out _in the flame_, taking great care that the tube is -withdrawn from the flame the moment it is closed. The tube must also be -kept in an upright position until it has cooled. The appearance of the -finished tube is shown in fig. 41, 6. - - [Illustration: FIG. 42.--SMALL SPECIMEN TUBE MOUNTED ON A CARD] - -All preserved specimens should have a label attached on which is written -the name of the specimen, the class and order to which it belongs, the -locality in which it was found, together with any brief remarks that the -owner desires to remember concerning its habits &c. - -The bottles or tubes that are too small to have a label attached to them -in the ordinary way may be mounted on a card, as represented in fig. 42, -and the desired particulars then written on the card. - -When soft or delicate specimens are preserved in a bottle of fluid they -frequently require some kind of support to keep them in proper form and -to display them better for observation. Perhaps the best way to support -them is to fasten them to a very thin plate of mica of suitable size by -means of a needle and very fine thread. The mica is so transparent that -it is invisible in the fluid, and the few stitches are also hardly -perceptible, thus making it appear as if the specimen floats freely in -the fluid. - -We will now pass on to consider those objects of the shore that are -usually preserved in a dry condition, commencing with - - - STARFISHES AND SEA URCHINS - -Starfishes are commonly preserved by simply allowing them to dry in an -airy place, with or without direct exposure to the sun's rays, and this -method is fairly satisfactory when the drying proceeds rapidly; but care -should be taken to maintain the natural roughness of the exterior as -well as to have the numerous suckers of the under surface as prominent -as possible. If the starfish is simply laid out on some surface to dry, -the side on which it rests is often more or less flattened by the weight -of the specimen itself, which therefore becomes adapted for the future -examination of one surface only; but a better result, as regards both -the rapidity of drying and the after appearance of the specimen, may be -obtained by suspending it on a piece of fine net or by threads. A still -better plan is to put the dead starfish into _strong_ spirit, which will -rapidly extract the greater part of the moisture that its body -contained. After allowing it to remain in this for a day or two to -harden it, put it out to dry as before mentioned. The spirit, being very -volatile, will soon evaporate, so that the specimen will shortly be -ready for storing away. - -It is most important to observe that dried specimens--not starfishes -only, but all animal and vegetable objects--should never be placed in -the cabinet or other store-case until _perfectly_ dry, for a very small -amount of moisture left in them will often encourage the development of -moulds, not only on themselves, but on other specimens stored with them. - -Very small and delicate starfishes, when preserved in a dry condition, -may be protected from injury by fastening them on a card by means of a -little gum, or by keeping them permanently stored on cotton wool in -glass-topped boxes. - -Sea urchins, or sea eggs, as they are commonly called, may be preserved -exactly in the same way as starfishes, though it is more essential in -the case of these to soak them in strong spirit previous to drying, -otherwise the soft animal matter within the shell will decompose before -the drying is complete. Here, however, it is possible to remove the -whole interior with the aid of a piece of bent wire, and to thoroughly -clean the inner surface of the shell before drying it. - -Some of the shells should be preserved with the spines all intact, and -others with these removed in order to show the arrangement of the -plates which compose the shell, as well as the perforations, and the -rounded processes to which the spines are articulated. - -The majority of sea urchins are provided with a most complicated and -beautiful arrangement of teeth which are well worthy of study. These -should be removed from a moderately large specimen, the soft surrounding -structures carefully dissected away, and then cleaned by means of an old -tooth-brush without disarranging them. - -It will be found that dried sea urchins will require care when preserved -with spines attached, for these appendages are usually very brittle and -are easily dislocated at their bases where they are united to the shell -by ball-and-socket joints. - -It may be mentioned here that corrosive sublimate is very valuable for -preventing the development of mould on the surfaces of starfishes, sea -urchins, and museum specimens generally. It is best supplied in the form -of an alcoholic solution made by dissolving a few grains in about half a -pint of methylated spirit; the advantage of this over an aqueous -solution being the rapidity with which it dries. In most cases it is -simply necessary to apply the solution to the object by means of a soft -brush, but, as regards starfishes and urchins it is far better to -dissolve a few grains of the corrosive sublimate in the spirit in which -the objects are placed previous to drying. - - - CRUSTACEANS - -The preservation of crustaceans by the dry method often requires some -care and demands a certain amount of time; but the process is never -really difficult, and the satisfaction of having produced a good -specimen for a permanent collection well repays one for the trouble -taken and time spent. - -Some of our crustaceans are only partially protected by a firm outer -covering, and almost every attempt to preserve these as dry objects -results in such a shrivelling of the soft tissues that the natural -appearance is quite destroyed. This is the case with some of the -barnacles, and the abdominal portion of the bodies of hermit crabs, -which are, therefore, far better preserved in fluid. Dilute spirit is -quite satisfactory for most of these as far as the preservation of the -soft structures is concerned, but it has the disadvantage that it turns -the shells of some crustaceans red, making them appear as if they had -been boiled. - -Other crustaceans are so small, or are hardened externally to such a -slight extent, that they also are not adapted for the dry method of -preservation. Speaking generally, such crustaceans as shrimps and -sand-hoppers are best preserved in fluid, while the different species of -crabs and lobsters are more conveniently preserved dry unless it is -desired to study any of their soft structures. - -It is quite impossible to remove the soft parts from small crabs and -lobsters previous to drying them, hence the drying should be conducted -as rapidly as possible, so that no decomposition may set in. Where the -process goes on very slowly, as is the case when the air is damp, or -when the specimens are not set out in an airy spot, a decay of the soft -structures soon proceeds, and the products of this decay will generally -saturate the whole specimen, giving rise to most objectionable odours, -and destroying the natural colour of the shell. - -If it has been found that the species in question are not reddened by -the action of methylated spirit, they should be allowed to remain in -this fluid, with a few grains of dissolved corrosive sublimate, for at -least a few hours, and then they will dry rapidly without any signs of -putrefaction; and even those species that _are_ reddened by spirit may -be treated to a shorter immersion in this fluid with advantage. - -The specimens should always be set out in some natural attitude to dry, -unless it is desired to spread out the various appendages in some manner -that is more convenient for the study of their structure. A sheet of -blotting-paper may be placed on cork or soft wood, the specimens placed -on this, and the appendages kept in the desired positions when necessary -by means of pins placed beside, but not thrust through them. When more -than one specimen of the same species has been collected, one should be -set in such a manner as to exhibit the under side; and, further, in -instances where the male and female of the same crustacean differ in -structure, as is commonly the case, two of each should be preserved, one -displaying the upper, and the other the under surface. - -When perfectly dry, all small crustaceans should be mounted on cards -with the aid of a little gum, and the name and other particulars to be -remembered then written on the card. - -The question may well be asked: 'Which is the best gum to use?' In -answer to this we may say that gum tragacanth is certainly as good as -any. It holds well, and leaves no visible stain on a white card. A small -quantity of the solid gum should be put into a bottle with water in -which a grain or so of corrosive sublimate has been dissolved. It -absorbs much water, becoming a very soft, jelly-like mass. Any excess of -water may be poured off, and the gum is then ready for use. - -The larger crabs and lobsters contain such an amount of soft tissue -within that it becomes absolutely necessary to clear them in order to -avoid the unpleasant and destructive effects of decomposition. - - [Illustration: FIG. 43.--SMALL CRAB MOUNTED ON A CARD] - -In the case of lobsters the abdomen should be removed from the large -cephalo-thorax by cutting through the connecting membrane with a sharp -knife. The soft portions of both halves of the body are then raked out -by means of a piece of wire flattened and bent at one end, and the -interior cleaned with the aid of a rather stiff bottle-brush. The large -claws are then removed by cutting through the membrane that unites them -with the legs, and these are cleared in a similar manner. The different -parts are next laid out to dry on blotting-paper, with the various -appendages attached to the body arranged just as in life; and, finally, -when all parts are quite dry, both within and without, the separated -parts are reattached by means of some kind of cement. For this purpose a -solution of gelatine in acetic acid is much better than gum tragacanth, -as it has a far greater holding power, and this is necessary when we -require to unite rather large structures with but small surfaces in -contact. - -Large crabs are to be dealt with much in the same manner, but, instead -of removing the abdomen only, which, in the crab, is usually very small -and doubled under the thorax, the whole carapace--the large shell that -covers the entire upper surface of the body--should be lifted off, and -replaced again after the specimen has been cleaned and dried. - - - MARINE SHELLS &C. - -We have previously dealt with the preservation of the shell-less -molluscs, and the soft bodies of the shelled species when such are -required, so we will now see what should be done with the shells. - -Numerous shells are often to be found on the sea beach--shells that have -been washed in by the breakers, and from which the animal contents have -disappeared, either by the natural process of decay, aided by the action -of the waves, or by the ravages of the voracious or carrion-eating -denizens of the sea; and although these shells are rarely perfect, -having been tossed about among the other material of the beach, yet we -occasionally find here the most perfect specimens of both univalve and -bivalve shells in such a condition that they are ready for the cabinet, -and these often include species that are seldom found between the -tide-marks, or that are otherwise difficult to obtain. - -However, the shell-collector must not rely on such specimens as these -for the purpose of making up his stock, but must search out the living -molluscs in their habitats and prepare the shells as required. - -The molluscs collected for this purpose are immersed in boiling water -for a short time, and the animal then removed from the shell. In the -case of bivalves it will generally be found that the hot water has -caused the muscles of the animal to separate from the valves to which -they were attached, or, if not, they have been so far softened that they -are easily detached, while it does not destroy the ligament by means of -which the valves are held together at the hinge; but the univalve -molluscs must be removed from their shells by means of a bent pin or -wire. In the latter instance care must be taken to extract the whole of -the body of the animal, otherwise the remaining portion will decompose -within the shell, giving rise to the noxious products of natural decay. - -The univalves have now simply to be placed mouth downwards on -blotting-paper to drain and dry, when they are ready for the cabinet. -If, however, they include those species, like the periwinkles and -whelks, that close their shells by means of a horny lid (_operculum_) -when they draw in their bodies, these lids should be removed from the -animal and attached to their proper places in the mouth of the shell. -The best way to accomplish this is to pack the dry shells with cotton -wool, and then fasten the opercula to the wool by means of a little gum -tragacanth or acetic glue. - -Bivalve shells should, as a rule, be closed while the ligament is still -supple, and kept closed until it is quite dry, when the valves will -remain together just in the position they assume when pulled together by -the living animal. The shells of the larger species may be conveniently -kept closed during the drying of the ligament by means of thread tied -round them, but the very small ones are best held together by means of a -delicate spring made by bending fine brass wire into the form shown in -fig. 44. - - [Illustration: FIG. 44.--SPRING FOR HOLDING TOGETHER SMALL BIVALVE - SHELLS] - -There are many features connected with the internal structure and -surface of the shells of molluscs that are quite as interesting and -instructive as those exhibited externally; hence a collection of the -shells intended for future study should display internal as well as -external characteristics. Thus, some of the spiral univalve shells may -be ground down on an ordinary grindstone in order to display the central -pillar (the _columella_) and the winding cavity that surrounds it, while -others, such as the cowries, may be ground transversely to show the -widely different character of the interior. Bivalve shells, too, may be -arranged with the valves wide open for the study of the pearly layer, -the lines of growth, the scars which mark the positions of the muscles -that were attached to the shell, and the teeth which are so wonderfully -formed in some species. - -Some collectors make it a rule to thoroughly clean all the shells in -their collection, but this, we think, is a great mistake; for when this -is done many of the specimens display an aspect that is but seldom -observed in nature. Many shells, and especially those usually obtained -in deep water, are almost always covered with various forms of both -animal and vegetable growth, and it is advisable to display these in a -collection, not only because they determine the general natural -appearance, but also because these growths are in themselves very -interesting objects. Further, it is a most interesting study to inquire -into the possible advantages of these external growths to the -inhabitants of the shells, and _vice versâ_--a study to which we shall -refer again in certain chapters devoted to the description of the -animals concerned. - -But there is no reason whatever why some of the _duplicate_ specimens -should not be cleaned by means of a suitable brush, with or without the -use of dilute hydrochloric acid (spirits of salt), or even polished, in -some few cases, to show the beautiful colours so often exhibited when -the surface layer has been removed. This, however, should be done -somewhat sparingly, thus giving the greater prominence to the exhibition -of those appearances most commonly displayed by the shells as we find -them on the beach or dredge them from the sea. - -Very small and delicate shells may be mounted on cards, as suggested for -other objects; but, as a rule, the specimens are best displayed by -simply placing them on a layer of cotton wool in shallow boxes of -convenient size. - -The number of insects that may be described as truly marine is so small -that their preservation is not likely to form an important part of the -work of the sea-side naturalist; and even though a considerable number -of species exhibit a decided partiality for the coast, living either on -the beach or the cliffs, the study of these is more generally the work -of the entomologist. For this reason, and partly because we have already -given full instructions for the setting and mounting of insects in a -former work of this series, we consider a repetition inadmissible here. - -The subject of the preservation of fishes, also, will require but few -words. There is no satisfactory method of preserving these in a dry -state, though we often meet with certain thin-bodied species, such as -the pipe-fish, that have been preserved by simply drying them in the -sun. Fishes should be placed in dilute spirit, or in one of the other -liquids recommended, but a change of fluid will always be necessary -after a time, and also frequently the gentle application of a brush to -remove coagulated slime from the surface of the scales. - -The great drawbacks in the way of preserving a collection of fishes are -the expense of the specimen jars, and the large amount of space required -for storing the specimens. Of course the former difficulty can be -overcome by substituting ordinary wide-mouthed bottles in the place of -the anatomical jars, while the latter can be avoided to a considerable -extent by limiting the collection to small species, and to small -specimens of the larger species. If this is done, it is surprising what -a large number of fishes can be satisfactorily stored in bottles of only -a few ounces' capacity. - - - FLOWERS AND SEA WEEDS - -The apparatus required for the preservation of the wild flowers of our -cliffs, and the sea weeds, consists of a quantity of blotting paper or -other thick absorbent paper cut to a convenient size, a few thin boards -and a few pieces of calico of the same size, some heavy weights, and -several sheets of drawing paper. - -The wild flowers are arranged on the sheets of absorbent paper while -still fresh, care being taken to display the principal parts to the best -advantage. They are then placed in a single pile, with a few extra -sheets of absorbent paper between each two specimens to facilitate the -drying, boards at the bottom and top as well as at equal distances in -the midst of the pile, and the weights on the top of the whole. - -The natural colours of leaves and flowers are not very often preserved -satisfactorily, but the best results are obtained when the drying -process proceeds most rapidly. Hence, if the press contains any -specimens of a succulent or sappy nature, they should be taken out after -the first day or two, and then replaced with a fresh supply of dry -paper. - -The flowers must be left in the press until quite dry, and they may then -be mounted on sheets of drawing paper, by fixing them with a little gum -tragacanth, or by narrow strips of gummed paper passing over their -stems. - -Some collectors prefer simply placing their botanical specimens inside -double sheets of drawing paper, not fastening them at all, and there is -much to be said in favour of this, especially as it allows the specimens -to be examined on both sides; and even when they _are_ fastened to the -paper double sheets are much to be preferred, for the specimens are not -then so liable to be damaged by friction when being turned over, -especially when the names are written on the outside of each sheet. - -The larger sea-weeds may be dried in the same manner, though it is a -good plan to absorb the greater part of the moisture they contain by -pressing them between pieces of calico previous to placing them in the -ordinary press. It should be observed, however, that many sea-weeds -exude a certain amount of glutinous substance that makes them adhere to -the paper between which they are dried, while they do not so freely -adhere to calico. These should be partially dried in the calico press, -and then laid on the paper on which they are to be finally mounted, and -re-pressed with a piece of dry calico on the top of each specimen. - -Many of the smaller weeds may be treated in the manner just described, -but the more delicate species require to be dealt with as -follows:--Place each in a large, shallow vessel of water, and move it -about, if necessary, to cause its delicate fronds to assume that -graceful form so characteristic of the algæ of our rock pools. Then -immerse the sheet of paper on which the weed is to be finally mounted, -and slowly raise the specimen out of the water, on the paper, without -disturbing the arrangement of the fronds. If it is found necessary to -rearrange any of the fronds, it may be done by means of a wet camel-hair -brush. Now lay the specimen on calico or absorbent paper, placed on a -sloping board, to drain; and, after the greater part of the moisture has -disappeared by draining and evaporation, transfer the specimen to the -press with a piece of dry calico immediately over it. All are dealt with -in turn in the manner described, and allowed to remain in the press -until perfectly dry, when it will be found that the majority of them -have become firmly attached to the mount, and require nothing but the -label to fit them for the herbarium. - -Sea-weed collectors often make the great mistake of pressing tufts that -are far too dense to admit of the structural characters being -satisfactorily examined. To avoid this fault, it will often be necessary -to divide the clusters collected so that the forms of their fronds may -be more readily observed. - -The calcareous corallines may be pressed in the same way as the other -algæ, but very pretty tufts of these, having much the appearance of the -living plant, may be obtained by simply suspending them until thoroughly -dry; though, of course, specimens so prepared must not be submitted to -pressure after they are dry, being then so brittle that they are easily -broken to pieces. - -The hard framework of these interesting corallines is composed -principally of carbonate of lime, a mineral substance that dissolves -freely in hydrochloric acid (spirits of salt). Thus, if we place a tuft -of coralline in this acid, which should be considerably diluted with -water, the calcareous skeleton immediately begins to dissolve, with the -evolution of minute bubbles of carbonic acid gas; and after a short -time, the end of which is denoted by the absence of any further -bubbling, nothing remains but the vegetable matter, now rendered soft -and pliant. A decalcified specimen of coralline may be pressed and -dried, and then mounted beside the plant in its natural condition for -comparison; and the true appearance of the vegetable structure may also -be retained, and in a far more satisfactory manner, by preserving a -portion of the specimen in dilute spirit. - -Finally, it may be observed that many sea-weeds, like wild flowers, do -not retain their natural forms and colours when preserved dry. They are -spoilt by the pressure applied, or become so shrivelled and discoloured -in the drying as to be but sorry representatives of the beautifully -tinted and graceful clothing of the rocks of the coast. But many of -those that suffer most in appearance when dried may be made to retain -all their natural beauty by preserving them in a fluid; and it is most -important that this should be remembered by all who desire to study the -weeds at home, and particularly by those who possess a microscope, and -wish to search into the minute structure of marine algæ. Our own plan is -to keep not only the dried specimens for the purpose of studying the -general characters and classification of the algæ, but also to keep a -few large bottles--stock bottles--filled with weeds of all kinds in a -preservative fluid. These latter are exceedingly useful at times, and -are frequently brought into requisition for close inspection, with or -without the microscope. Small pieces may be detached for microscopic -examination when required, and sections may be cut either for temporary -or permanent mounting just as well as from living specimens, such -sections showing all the details of structure exhibited by the living -plant. - - - THE MUSEUM - -One of the greatest difficulties besetting the young collector lies in -the choice and construction of the cabinet or other store-house for the -accommodation of the specimens that accumulate as time advances. - -Of course, when expense is a matter of no great consideration, a visit -to the nearest public or private museum to see the manner in which the -specimens are housed, followed by an order to a cabinet-maker, will set -the matter right in a short time; but it is probable that the majority -of our readers are unable to fit up their museum in this luxurious -style, and will either have to construct their own cabinets and -store-boxes or to purchase cheap substitutes for them. - -Where one has the mechanical ability, and the time to spare, the -construction of a cabinet with the required number of drawers may be -undertaken, and there is no better form of store than this. The whole -should be made of well-seasoned wood, and the drawers should vary in -depth according to the size of the specimens they are to contain. Some -of these drawers may be lined with sheet cork, and the cork covered with -white paper or a thin layer of cotton wool. This will enable some of the -specimens to be fixed in their places by means of pins. As a rule, -however, no pins will be required, and the specimens will be most -conveniently arranged in shallow cardboard boxes, placed in rows in the -drawer, a little cotton wool covering the bottom of each. - -Failing the usual cabinet, the specimens may be stored in shallow trays -or boxes, or even in the little cardboard cabinets so often sold for -storing stationery &c. The best and cheapest things of this kind we have -ever met with are the little cabinets, each containing either six or -twelve drawers, made by Macdonald & Co., of Temple Row, Birmingham. By -the use of such as these the specimens may be neatly stored away, and -additions to match may always be made as the collection increases in -magnitude. - -The specimens should all be classified according to their positions in -the animal or vegetable world, and accompanied by labels giving the name -of species and genus, together with localities, habitats, &c. The -outlines of classification may be studied from the later chapters of -this work, in which the common objects of the sea shore are described in -their scientific order, beginning with the lowest sub-kingdoms and -classes; and further, it will be observed that the sub-kingdoms are -divided into classes, the classes into orders, orders into families, -families into genera, and that the genera contain a smaller or larger -number of closely allied species. - -The collection must be kept in a perfectly dry place, otherwise many of -the specimens will be liable to develop moulds, and this will, of -course, quite spoil their appearance. It is almost sure to be attacked -by mites and other animal pests unless some means be taken to prevent -their intrusion. - -As regards the latter, it is well to know that it is far easier to -prevent the intrusion of small animal pests than it is to exterminate -them after they have once found an entrance; and so, from the very -commencement of the formation of the collection, all drawers and boxes -should be charged with some substance that is objectionable, if not -fatal, to them. Small lumps of naphthaline (albo-carbon) put into the -various compartments, and renewed occasionally as they disappear by -evaporation, will generally suffice to prevent the entrance of all -pests, but this substance is not effectual as an insecticide for the -purpose of killing them after they are in. - -Perhaps the best of all insecticides is the corrosive sublimate already -mentioned, and this may be applied to any animal or vegetable object -that is capable of providing food for museum pests, and it is difficult -to find such an object on which they will not feed. - -Many of the specimens that find a place in a museum have been -temporarily preserved in spirit previous to being dried, and if a little -corrosive sublimate was dissolved in this spirit, the specimens will -have been rendered perfectly free from all attacks of marauders, since -the spirit will have saturated the whole object, carrying with it the -dissolved poison. - -Most of the specimens that have not been treated by the above method -would not suffer from a short immersion in spirit containing the -corrosive sublimate; but in cases where it is considered inexpedient to -do this, the same liquid may be applied to them by means of a soft -brush. In this way even the dried botanical specimens may be rendered -perfectly secure from attacks. - - - - - CHAPTER VI - - _EXAMINATION OF MARINE OBJECTS--DISSECTION_ - - -An enthusiastic observer of nature will learn much concerning the -structure of natural objects with the unaided eye, but there are times -when he will desire some kind of magnifier to reveal more perfectly the -structure of minute parts, or to enable him to observe the small -creatures that are invisible to the naked eye. Further, one may learn -many interesting and instructive facts relating to animal and plant life -by cutting sections for close examination, or by making such simple -dissections as will enable one to observe the more salient features of -internal structure; we therefore propose in the present chapter to make -a few remarks and suggestions regarding work of this kind. - -A pocket magnifier is of great value to the young naturalist, both for -the inspection of natural objects while engaged in out-door work, and -for the subsequent examination of the specimens collected for study. It -is often necessary to enable one to identify and classify small animals -and plants, and will be in constant demand for the purpose of studying -the less conspicuous external features. Such an instrument should be -regarded as an essential companion of the naturalist, and should -accompany him on every ramble. - -There are several different forms of pocket lenses, but for general work -there is, perhaps, nothing more convenient and serviceable than the -'triplet' magnifier. It is a combination of three lenses, enclosed in a -pocket case, and so arranged that they may be used separately or in -combination, thus supplying a variety of powers. The three lenses of the -triplet are themselves of different magnifying powers, and these powers -may be increased by combining two or all of them. - -For work at home a 'dissecting microscope' is very useful. This consists -of a magnifying lens, mounted on a support over a surface on which small -objects may be examined and dissected, the height of the lens being, of -course, adjusted according to its focal distance. Lenses ready mounted -on adjustable stands may be purchased for this purpose, but no one ought -to experience much difficulty in designing and constructing some simple -stand that will give every satisfaction. - -The arrangement just described is, of course, suitable for the -dissection of only small objects, and these are placed on a material -adapted to the nature of the work to be done. Thus it is sometimes -convenient to place the object to be examined on a small sheet of cork, -in order that it may be secured by means of pins while the dissection -proceeds, while at other times it is essential that it be laid on a hard -and unyielding surface, such as that of a slip of glass. But whatever be -the nature of the substance on which the dissection is made, its colour -may be regulated according to that of the object. If, for example, we -are dissecting a small white flower on a piece of cork, we should -naturally blacken the cork, or cover it with a piece of dead black -paper; or, if we are to dissect a small, light-coloured object on a -glass surface, we lay the glass on black paper. - - [Illustration: FIG. 45--THE TRIPLET MAGNIFIER] - -The advantage of dissecting objects under water does not seem to be -generally appreciated by beginners, who often allow their specimens to -become dry and shrivelled, almost beyond recognition, during the -progress of their examination. This mode of dissection is certainly not -necessary with all objects, but may be generally recommended for soft -and succulent vegetable structures, as well as for almost all animal -dissections. - -This being the case, arrangements should certainly be made to provide a -miniature dissecting trough as an accessory to the dissecting -microscope, and the following instructions will enable the reader to -construct a highly satisfactory and inexpensive one:-- - -Procure the flat lid of a cylindrical tin box, or the lid of a glass or -porcelain pomade pot, such lid to be about two inches in diameter and -about half an inch in depth. Cement the flat side of this lid to a small -slab of hard wood, or to a square piece of sheet lead, by means of -acetic glue--ordinary glue or gelatine dissolved in glacial acetic -acid--to give it the necessary steadiness during the dissection. When -the cement is quite hard, pour into the lid some melted paraffin -(paraffin wax) which has been blackened by the admixture of a small -quantity of lamp-black in the form of a fine powder. The paraffin should -be melted by putting it into a beaker or wide-mouthed bottle, and -standing it in hot water, and the lamp-black should be added, with -stirring, as soon as it is entirely liquefied. The quantity of the -mixture used must be sufficient to half fill the lid, thus leaving a -space to contain water to the depth of about a quarter of an inch. The -blackened wax provides a good background on which to work, and provides -a hold for pins when these are necessary in order to fix the object -under examination. - - [Illustration: FIG. 46.--A SMALL DISSECTING TROUGH] - -The complete trough is represented in fig. 46; and will be found to -answer its purpose admirably, except that it occasionally displays one -fault, but one that is easily remedied. The wax contracts on cooling, -and may, therefore, detach itself from the trough; and, being lighter -than water, will float instead of remaining submerged. This may be -prevented by securing the disc of wax in its place by means of a ring of -brass wire, or by weighting the wax with two or three small pieces of -lead pushed down into it while it is yet soft. - -With such a dissecting microscope and trough as we have described one -may do a great deal of exceedingly useful work, both hands being quite -free to manipulate the object under examination. - -The dissection may be conducted with the aid of a small scalpel or other -very sharp knife, the parts being arranged or adjusted by means of a -needle, mounted in a handle, and held in the left hand. Sometimes, -however, the object to be dissected is so minute that even a small -scalpel is too large for the purpose, and in such cases nothing is -better than little dissecting instruments made by mounting large sewing -needles in suitable handles, and then grinding down the points of the -needles on two opposite sides, on a hone, so as to produce little -pointed, two-edged blades. Bent needles are often useful, too, and these -may be prepared by heating the points to redness in a gas-flame, bending -them as desired while hot, and then hardening them by suddenly thrusting -them, at a red heat, into cold water. - -The compound microscope will often prove useful for the examination of -very minute objects, as well as for the study of the structure of the -principal tissues of the larger species; but since detailed instructions -for the management of the microscope, and for the preparation of objects -for microscopic examination would occupy much more space than we can -spare, we shall content ourselves with nothing more than a few general -hints on this portion of the young naturalist's work, dealing more -particularly with those points which commonly present difficulties to -the amateur. - -If it is desired to examine some minute living object, such as a -protozoon, place the object in a drop of the water in which it lived -just in the middle of a clean glass slip, and cover it with a -cover-glass. The quantity of water should be just sufficient to fill the -space between the two glasses. If less than this has been used, a little -more applied to the edge of the cover by means of a glass rod will -immediately run in between the glasses; while if an excessive amount was -employed, the surplus may be removed by the application of a strip of -blotting paper. Place the glass slip on the stage of the microscope, and -reflect light through it from the mirror below. - -Examine it first with a low power; and, after having observed as much as -possible of the creature's movements and structure with this aid, repeat -with a higher power. This rule applies not only to such small objects as -we have now under consideration, but to all objects, and parts of them, -in which minute details are to be observed. - -Beginners with the microscope often find prolonged examination very -tiring to the eyes, but this, we believe, would seldom be the case if -right methods were followed. Both eyes should always be open, and the -microscopist should train himself to use both eyes equally for the -actual observation. - -The higher the magnifying power used, the nearer must the objective (the -lower combination of lenses) be brought to the object itself, and it is -no uncommon thing for the amateur, in his attempts to focus his object, -to lower the body of the microscope beyond its proper position, causing -the objective to crush the object, break the thin cover-glass, and -become wetted with the liquid, if any, in which the object was being -examined. All this may be avoided by lowering the body of the microscope -until it nearly touches the cover-glass before attempting to view the -object through it, and then, with the eye above the object-glass, to -gradually raise the body until the object is in focus. - - [Illustration: FIG. 47.--CELL FOR SMALL LIVING OBJECTS] - -The top of the cover-glass should always be perfectly dry; and if by any -chance the objective becomes wet it should be wiped perfectly dry with a -piece of old silk or with chamois leather. Also, if permanent mounting -is attempted, and the preservative liquid is allowed to come in contact -with the objective, such liquid must, of course, be washed off with some -suitable solvent before any attempt is made to wipe the lens dry. - -If the object under examination is of such dimensions that the -cover-glass has a tendency to rock on it, or if it is a living object of -such a size that it is unable to move freely in the exceedingly thin -film of water between the cover and the slip, it should be placed in a -cell. The cell may be made by cementing a ring of glass or vulcanite to -the middle of a slip, or it may be a little circular cavity prepared in -the slip itself. In either case the cell must be quite full of water -before the cover-glass is applied, so that no air-bubbles are included. - -Hitherto we have spoken only of mounting small objects in water, and -this is advisable when the object is moist, whether it be animal or -vegetable, alive or dead. But dry objects may be examined in the dry -state, in which case they need not be covered. If they are composed of -transparent material they are to be dealt with in the manner recommended -before, as far as the management of the light is considered; that is, a -moderately strong light is sent through them by the reflector below the -stage; but opaque objects are best examined on a dead black ground, the -light being directed on to them by means of a condensing lens placed -between them and the source of light. - -A collector who has done only a few days' work on the sea shore will -probably find himself the possessor of a host of interesting objects -that will afford much pleasure and instruction when placed under the -microscope--objects, many of which have been somewhat hastily deposited -in a bottle of spirit or other preservative for study in his future -leisure moments. These objects, if small, may be examined as above -described, simply placing them under a cover-glass, or in a cell, with a -clear drop of the same liquid in which they have been kept. - -The general characters of the larger objects may also be observed by -means of some kind of hand lens, but even these are generally best -examined under water or other suitable liquid. - -A great deal may be learnt of natural objects by preparing very thin -sections for microscopic examination; and although special works should -be consulted if one desires to become proficient in the different -methods of cutting and preparing such sections, yet a great amount of -good work may be done with the aid of a sharp razor, manipulated with -nothing more than ordinary skill. - -Some objects, especially certain of those of the vegetable world, are of -such a nature that suitable sections may be cut, either from the fresh -or preserved specimen, without any preliminary preparation. All that is -required is to hold the object firmly between the finger and thumb of -the left hand, previously securing it in some kind of holder if -necessary, and pare off the thinnest possible slices with a horizontal -movement of the razor, both razor and object being kept very wet during -the process. As the sections are cut they may be allowed to drop into a -shallow vessel of water; and, the thinnest then selected for examination -in water as previously described. - -Other objects are so soft that the cutting of sections becomes -impossible without previously hardening them. Methylated spirit is a -good hardening reagent, and many of the soft structures that have been -preserved in this fluid, especially if it has been used undiluted, will -be found sufficiently hard for cutting thin sections. Among the other -hardening reagents used by microscopists may be mentioned a solution of -chromic acid--one part by weight of the solid acid dissolved in from one -hundred to two hundred parts of water, and a solution of bichromate of -potash--one part of the bichromate to about forty parts of water. In -either case the hardening of the object takes place slowly, and it -should be examined from day to day until the necessary consistence has -been obtained. - -The structures of many soft animals can never be satisfactorily hardened -for section-cutting by either of the above reagents, and thus it becomes -necessary either to freeze or to imbed them. In the former case the -object is first soaked in gum water--a thin solution of gum arabic--and -then frozen by an ether spray or by a mixture of ice and salt. The -sections should be cut with a razor just as the object is beginning to -thaw, and they may then be examined under a cover-glass, in a drop of -the gum water. - -The other method is conducted as follows:--The soft object is first -soaked in absolute alcohol to extract all the water it contains, and is -then transferred to paraffin that has been heated just to its -melting-point by standing it in warm water. After the object is -thoroughly permeated with the paraffin, the whole is cooled quickly by -immersion in cold water. Sections are now cut, the paraffin being sliced -away with the substance it contains. These sections are placed in warm -turpentine, where they are allowed to remain until the whole of the wax -has dissolved, and they may then be mounted in a drop of turpentine, and -covered with a cover-glass. - -We have given brief instructions for temporary mounting only, but most -amateur microscopists would undoubtedly prefer mounting their objects -permanently, so that they may be set aside for study at any future -period. Hence we append a few directions to this end, advising the -reader, however, to consult a work dealing especially with this subject -if he desires to become proficient in the preparation of microscopic -slides. - -Moist objects, including those which have been preserved in dilute -spirit, may be soaked in water, then transferred direct to the glass -slip, and covered with a drop of glycerine. Any excess of the glycerine -should then be absorbed from around the cover-glass by means of a strip -of blotting-paper, and the edge of the cover cemented by gold size -applied with a small camel-hair brush. - -Glycerine jelly is also a valuable mountant for permanent work. When -this is used the object should first be soaked in glycerine, and then in -the melted jelly. It is then transferred to a drop of melted jelly which -has been placed on a _warm_ slide, and covered as before. The jelly soon -solidifies, so that a ring of cement is not absolutely necessary, though -it is advisable, as a rule, to cement the cover-glass all round with -gold size or black varnish. - -Sections cut while frozen are best mounted in glycerine, to which they -may be transferred direct. - -Canada balsam is one of the best media for permanent mounting; and, as -it becomes very hard after a time, it serves the purposes of both -preservative and cement. When this is used the object must be entirely -freed from water by soaking it in absolute alcohol. It is then put into -turpentine for a minute or two, transferred to a warm slide, and covered -with a drop of the prepared balsam. Sections that have been imbedded in -paraffin may be mounted in this way, the turpentine acting as a solvent -for the paraffin in which it was cut. - -Although the compound microscope is absolutely necessary for the study -of the minutest forms of life and of the minute structure of the various -tissues of larger beings, yet the young naturalist will find that a vast -amount of good work may be done without its aid. Thus the general -structure of the larger species may be made out by means of simple -dissections requiring no extraordinary skill on the part of the worker, -and with appliances that may be obtained at a low cost. Certain of the -marine animals, however, require special treatment that can hardly be -described in a short chapter devoted to general instructions only, but -hints with regards to these will be given in future chapters in which -the animals referred to are described. - -The appliances referred to above include nothing more than a simple form -of dissecting trough, a few dissecting instruments, and one or two minor -accessories that may always be found at hand as required. - -The dissection of animals is always best performed under water, for by -this method the object examined may not only be kept clean as the work -proceeds, but the parts, having a tendency to float, readily separate -from one another and therefore become more distinctly visible when -submerged. - - [Illustration: FIG. 48.--SHEET OF CORK ON THIN SHEET LEAD] - -A very convenient form of trough may be made by taking any kind of -rectangular, flat-bottomed dish, one made of zinc being, perhaps, the -best of all, and covering the bottom with a slab of good cork carpet -which has been weighted with sufficient lead to prevent it from -floating. Or, instead of cork carpet, a sheet of cork may be used. In -either case, a piece of thin sheet lead, a little larger than the slab, -should be cut, the corners of which are then snipped off as shown in -fig. 48, and the edges finally turned over as represented in the next -illustration. The size of the trough must be regulated according to the -nature of the work to be done, but one measuring ten inches long, seven -wide, and two inches deep will answer most purposes. - - [Illustration: FIG. 49.--WEIGHTED CORK FOR DISSECTING TROUGH] - -The object to be dissected is placed in the trough, secured in position -by means of a few ordinary pins, and then completely covered with -water. - -We need hardly impress upon the reader the great importance of -thoroughly examining all external characters--all those structures that -are visible without actual dissection--before attempting to remove -anything; and we have already insisted on the importance of carefully -examining all creatures while alive before anything else is done. The -value of this latter stipulation can hardly be overestimated, for in -many instances it is almost impossible to detect the use of an organ -unless it has been observed in action; and the enthusiastic student will -go even further than this, for he will make it an invariable rule to -sketch everything he sees, and to make full notes on all his -observations. - -When pins are used to fix the object under examination--and it is -generally essential that the object be fixed--their heads should be -turned outwards; for then the object will not slip from its position, -nor will the pins tend to get in the way of the work. - -Some objects are of such a nature that they are not easily secured by -means of pins, and yet require to be fixed in some way or other. Thus, -one may desire to examine the structure and appendages of a prawn or -small crab, or to investigate the nature of a chiton. In such instances -as these it is a good plan to make a cake of paraffin wax of suitable -size by pouring the melted substance into a mould, then secure the -object in proper position in the wax while still fluid, and pin the -latter to the cork of the dissecting trough. - -It is often necessary to trace the courses of internal passages that -open on the surface of the body, or of tubes that are revealed during -the progress of dissection, and this may be done by means of a little -instrument called a seeker. It is simply a blunted needle, bent into a -large angle, and mounted in a handle; or, it may consist of nothing but -a moderately long and stiff bristle, rendered blunt at one end by -tipping it with melted sealing wax. This is not always sufficient, -however, for it frequently happens that certain tubes and passages in -animal forms are disposed in such a complicated manner that it is -impossible to send even the most flexible seeker through them. For -instance, suppose one desires to trace the course of the digestive tube -of some large bivalve mollusc with its many reflections, the seeker is -useless except that it will penetrate to the first sharp bend. The -arrangement of such a tube must be traced by dissecting along its -course, but this may be aided considerably by first filling it with some -coloured substance to enable its direction to be more easily followed. -In fact, the injection of some brightly coloured fluid, forced through -the tube by means of a fine-nozzled glass syringe will often enable the -course of such a tube to be seen without any dissection at all, the -colour of the fluid used being detected through the semi-transparent -tissues surrounding it. A mixture of Berlin blue and water, or a mixture -of plaster of Paris and water coloured with carmine is well adapted to -this purpose; and if the latter is employed it may be allowed to set, -and thus produce a permanent cast from the tube that is being dissected. -Perhaps it should be mentioned that if either of the injection mixtures -be used for this purpose it must be previously strained through muslin, -and that, in the case of the plaster, the mixing and straining should -occupy as little time as possible, or it may begin to set before the -injection has been completed. - -A very considerable insight into the structure of animals may be -frequently obtained by cutting sections through the body with all its -organs _in situ_, but, generally speaking, they are too soft to allow of -this without danger of the displacement of those very parts, the -relations of which we desire to determine. To avoid this the body should -be previously hardened by a somewhat prolonged soaking in methylated -spirit, or in a solution of chromic acid prepared as before directed. -Then, with the aid of a good razor, very interesting sections may be -prepared with the greatest of ease, and the true relations of the -various organs throughout the body may be exactly determined by cutting -a succession of slices, not necessarily very thin, from end to end, or, -transversely, from side to side. - -Even those crustaceans that are protected by a hard, calcareous -exo-skeleton, and the molluscs that cannot be removed from their stony -shells without injury to their soft structures, may be studied in the -manner just described, and this may be done by first soaking them in -dilute hydrochloric acid, renewed as often as may be necessary, until -all the mineral matter has been dissolved completely, and then hardening -the softer tissues in one of the reagents mentioned above. Hydrochloric -acid may also be used to dissolve the calcareous shells of foraminifers, -the vegetable corallines, and other small forms of life, previous to -microscopic examination of the soft parts. - - - - - CHAPTER VII - - _THE PROTOZOA OF THE SEA SHORE_ - - -We shall now study the principal forms of animal life to be found on the -sea shore; and, in order that the reader may thoroughly understand the -broader principles of classification, so as to be able to locate each -creature observed in its approximate position in the scale of life, we -shall consider each group in its zoological order, commencing with the -lowest forms, and noting, as we proceed, the distinguishing -characteristics of each division. - -The present chapter will be devoted to the _Protozoa_--the sub-kingdom -that includes the simplest of all animal beings. - -Each animal in this division consists of a minute mass of a jelly-like -substance called _protoplasm_, exhibiting little or no differentiation -in structure. There is no true body-cavity, no special organs for the -performance of distinct functions, and no nervous system. - -Perhaps we can best understand the nature of a protozoon by selecting -and examining a typical example: - -Remove a small quantity of the green thread-like algous weed so commonly -seen attached to the banks of both fresh and salt water pools, or -surrounding floating objects, and place it in a glass with a little of -the water in which it grew. This weed probably shelters numerous -protozoons, among which we are almost sure to find some _amoebæ_ if we -examine a drop of the water under the high power of a microscope. - - [Illustration: FIG. 50.--THE AMOEBA, HIGHLY MAGNIFIED] - -The amoeba is observed to be a minute mass of protoplasm with an -average diameter of about one-hundredth of an inch, endowed with a power -of motion and locomotion. Its body is not uniformly clear, for the -interior portion is seen to contain a number of minute granules, -representing the undigested portions of the animal's food. There is a -small mass of denser protoplasm near the centre, termed the _nucleus_, -and also a clear space filled with fluid. This latter is called the -_vacuole_, and is probably connected with the processes of respiration -and excretion, for it may be seen to contract at irregular intervals, -and occasionally to collapse and expel its contents. - -As we watch the amoeba we see that it is continually changing its -shape, sending out temporary prolongations (_pseudopodia_) of its -gelatinous substance from any part, and sometimes using these extended -portions for the purpose of dragging itself along. - -Its method of feeding is as remarkable as it is simple. On coming in -contact with any desired morsel, it sends out two pseudopods, one on -each side of the food. These two pseudopods gradually extend round the -food, till, at last, they meet and coalesce on the opposite side of it, -thus completely enclosing it within the body. Any part of the body of -the am[oe]ba may thus be converted into a temporary mouth; and, there -being no special cavity to serve the purpose of a stomach, the process -of digestion will proceed equally well in any part of the body except in -the superficial layer, where the protoplasm is of a slightly firmer -consistence than that of the interior. Further, the process of digestion -being over, any portion of the superficial layer may be converted into a -temporary opening to admit of the discharge of indigestible matter. - - [Illustration: FIG. 51.--THE AMOEBA, SHOWING CHANGES OF FORM] - - [Illustration: FIG. 52.--THE AMOEBA, FEEDING] - -The amoeba is an omnivorous feeder, but subsists mainly on vegetable -organisms, especially on diatoms and other minute algæ; and the -siliceous skeletons of the former may often be seen within the body of -the animal, under the high power of a microscope. - -The multiplication of the amoeba is brought about by a process of -fission or division. At first the nucleus divides into two, and then the -softer protoplasm contracts in the middle, and finally divides into two -portions, each of which contains one of the nuclei. The two distinct -animals thus produced both grow until they reach the dimensions of -their common progenitor. - - [Illustration: FIG. 53.--THE AMOEBA, DIVIDING] - -All the protozoons resemble the amoeba in general structure and -function; but while some are even simpler in organisation, others are -more highly specialised. Some, like the amoeba, are unicellular -animals; that is, they consist of a single, simple speck of protoplasm; -but others live in colonies, each newly formed cell remaining attached -to its parent cell, until at last a comparatively large compound -protozoon is formed. - -The sub-kingdom is divided into several classes, the principal of which, -together with their leading characteristics, are shown in the following -table:-- - - 1. _Rhizopods:_--Body uniform in consistence. - Pseudopods protruded from any point. - 2. _Protoplasta:_--Outer protoplasm slightly firmer in consistence. - Pseudopods protruded from any point. - (Often grouped with the _Rhizopods_.) - 3. _Radiolaria:_--Possessing a central membranous capsule. - Usually supported by a flinty skeleton. - 4. _Infusoria:_--Outer protoplasm firmer and denser; therefore - of more definite shape. - Possess permanent threadlike extensions of protoplasm - instead of pseudopods. - -We shall now observe the principal marine members of the protozoa, -commencing with the lowest forms, and dealing with each in its proper -zoological order as expressed in the above table. - - - MARINE RHIZOPODS - -When we stand on a beach of fine sand on a very calm day watching the -progress of the ripples over the sand as the tide recedes we frequently -observe whitish lines marking the limits reached by the successive -ripples as they advance toward the shore. If, now, we scrape up a little -of the surface sand, following the exact course of one of these whitish -streaks, and examine the material obtained by the aid of a good lens, we -shall in all probability discover a number of minute shells among the -grains of sand. - -These shells are of various shapes--little spheres, discs, rods, -spirals, &c.; but all resemble each other in that they are perforated -with a number of minute holes or _foramina_. They are the skeletons of -protozoons, belonging to the class _Rhizopoda_, and they exist in -enormous quantities on the beds of certain seas. - - [Illustration: FIG. 54.--A GROUP OF FORAMINIFERS, MAGNIFIED] - -We will first examine the shells, and then study the nature of the -little animals that inhabit them. - -The shells vary very much in general appearance as well as in shape. -Some are of an opaque, dead white, the surface somewhat resembling that -of a piece of unglazed porcelain; others more nearly resemble glazed -porcelain, while some present quite a vitreous appearance, much after -the nature of opal. In all cases, however, the material is the same, all -the shells consisting of carbonate of lime, having thus the same -chemical composition as chalk, limestones, and marble. - -If hydrochloric acid be added to some of these shells, they are -immediately attacked by the acid and are dissolved in a very short time, -the solution being accompanied by an effervescence due to the escape of -carbonic acid gas. - -The shells vary in size from about one-twelfth to one three-hundredth of -an inch, and consist either of a single chamber, or of many chambers -separated from each other by perforated partitions of the same material. -Sometimes these chambers are arranged in a straight line, but more -frequently in the form of a single or double spiral. In some cases, -however, the arrangement of chambers is very complex. - -We have already referred to the fact that the shells present a number of -perforations on the exterior, in addition to those which pierce the -partitions within, and it is this characteristic which has led to the -application of the name Foraminifera (hole-bearing) to the little beings -we are considering. - - [Illustration: FIG. 55.--A SPIRAL FORAMINIFER SHELL] - - [Illustration: FIG. 56.--A FORAMINIFER OUT OF ITS SHELL] - -The animal inhabiting the shell is exceedingly simple in structure, even -more so than the amoeba. It is merely a speck of protoplasm, -exhibiting hardly any differentiation--nothing, in fact, save a -contractile cavity (the _vacuole_), and numerous granules that probably -represent the indigestible fragments of its food. - -The protoplasm fills the shell, and also forms a complete gelatinous -covering on the outside, when the animal is alive; and the vacuole and -granules circulate somewhat freely within the semi-solid mass. Further, -the protoplasm itself is highly contractile, as may be proved by -witnessing the rapidity with which the animal can change its form. - -When the foraminifer is alive, it floats freely in the sea, with a -comparatively long and slender thread of its substance protruded through -each hole in the shell. These threads correspond exactly in function -with the blunt pseudopodia of the amoeba. Should they come in contact -with a particle of suitable food-material, they immediately surround -it, and rapidly retracting, draw the particle to the surface of the -body. The threads then completely envelop the food, coalescing as soon -as they touch, thus bringing it within the animal. - - [Illustration: FIG. 57.--THE SAME FORAMINIFER (FIG. 56) AS SEEN WHEN - ALIVE] - - [Illustration: FIG. 58.--SECTION OF THE SHELL OF A COMPOUND - FORAMINIFER] - -The foraminifer multiplies by fission, or by a process of budding. In -some species the division of the protoplasm is complete, as in the case -of amoebæ, so that each animal has its own shell which encloses a -single chamber, but in most cases the 'bud' remains attached to a parent -cell, and develops a shell that is also fixed to the shell of its -progenitor. The younger animal thus produced from the bud gives rise to -another, which develops in the same manner; and this process continues, -the new bud being always produced on the newest end, till, at last, a -kind of colony of protozoons is formed, their shells remaining attached -to one another, thus producing a compound shell, composed of several -chambers, arranged in the form of a line or spiral, and communicating by -means of their perforated partitions. It will now be seen that each -'cell' of the compound protozoon feeds not only for itself, but for all -the members of its colony, since the nourishment imbibed by any one is -capable of diffusion into the surrounding chambers, the protoplasm of -the whole forming one continuous mass by means of the perforated -partitions of the complex skeleton. - - [Illustration: FIG. 59.--SECTION OF A NUMMULITE SHELL] - -Some of the simplest foraminifers possess only one hole in the shell, -and, consequently, are enabled to throw off pseudopods from one side of -the body only. In others, of a much more complex nature, the new -chambers form a spiral in such a manner that they overlap and entirely -conceal those previously built; and the development may proceed until a -comparatively large discoid shell is the result. This is the case with -_Nummulites_, so called on account of the fancied resemblance to coins. -Further, some species of foraminifera produce a skeleton that is horny -in character, instead of being calcareous, while others are protected -merely by grains of sand or particles of other solid matter that adhere -to the surface of their glutinous bodies. - - [Illustration: FIG. 60.--_Globigerina bulloides_, AS SEEN WHEN ALIVE, - MAGNIFIED] - -We have spoken of foraminifera as floating freely about in the sea -water, but while it is certain that many of them live at or near the -surface, some are known to thrive at considerable depths; and those who -desire to study the various forms of these interesting creatures should -search among dredgings whenever an opportunity occurs. Living specimens, -whenever obtained, should be examined in sea water, in order that the -motions of their pseudopods may be seen. - - [Illustration: FIG. 61.--SECTION OF A PIECE OF NUMMULITIC LIMESTONE] - -If we brush off fragments from the surface of a freshly broken piece of -chalk, and allow them to fall into a vessel of water, and then examine -the sediment under the microscope, we shall observe that this sediment -consists of minute shells, and fragments of shells, of foraminifers. In -fact, our chalk beds, as well as the beds of certain limestones, consist -mainly of vast deposits of the shells of extinct foraminifera that at -one time covered the floor of the sea. Such deposits are still being -formed, notably that which now covers a vast area of the bed of the -Atlantic Ocean at a depth varying from about 300 to 3,000 fathoms. This -deposit consists mainly of the shells of a foraminifer called -_Globigerina bulloides_, a figure of which is given on the opposite -page. - -The structure of chalk may be beautifully revealed by soaking a small -piece of the rock for some time in a solution of Canada balsam, allowing -it to become thoroughly dry, and then grinding it down till a very thin -section is obtained. Such a section, when viewed under the low power of -a compound microscope, will be seen to consist very largely of minute -shells; though, of course, the shells themselves will be seen in -section only. - -The extensive beds of nummulitic limestones found in various parts of -South Europe and North Africa are also composed largely of foraminifer -shells, the most conspicuous of which are those already referred to as -nummulites--disc-shaped shells of a spiral form, in which the older -chambers overlap and hide those that enclose the earlier portion of the -colony. - -Before concluding our brief account of these interesting marine -protozoons, it may be well to point out that, although the foraminifera -belong to the lowest class of the lowest sub-kingdom of animals, yet -there are some rhizopods--the _Monera_, which are even simpler in -structure. These are mere specks of undifferentiated protoplasm, not -protected by any shell, and not even possessing a nucleus, and are the -simplest of all animal beings. - -The second division of the Protozoa--the class _Protoplasta_--has -already received a small share of attention, inasmuch as the amoeba, -which was briefly described as a type of the whole sub-kingdom, belongs -to it. - -The study of the amoeba is usually pursued by means of specimens -obtained from fresh-water pools, and reference has been made to it in a -former work dealing particularly with the life of ponds and streams; but -it should be observed that the amoeba inhabits salt water also, and -will be frequently met with by those who search for the microscopic life -of the sea, especially when the water examined has been taken from those -sheltered nooks of a rocky coast that are protected from the direct -action of the waves, or from the little pools that are so far from the -reach of the tides as to be only occasionally disturbed. Here the -amoeba may be seen creeping slowly over the slender green threads of -the confervæ that surround the margin of the pool. - -The third class--_Radiolaria_--is of great interest to the student of -marine life, on account of the great beauty of the shells; but, as with -the other members of this sub-kingdom, a compound microscope is -necessary for the study of them. - -The animals of this group resemble the foraminifers in that they throw -out fine thread-like pseudopods, but they are distinguished from them by -the possession of a membranous capsule in the centre of the body, -surrounding the nucleus, and perforated in order to preserve the -continuity of the deeper with the surrounding protoplasm. They have -often a central contractile cavity, and further show their claim to a -higher position in the animal scale than the preceding classes by the -possession of little masses of cells and a certain amount of fatty and -colouring matter. - - [Illustration: FIG. 62.--A GROUP OF RADIOLARIAN SHELLS, MAGNIFIED] - -Some of the radiolarians live at or near the surface of the ocean, while -others thrive only at the bottom. The former, in some cases, appear to -avoid the light, rising to the surface after sunset; and it is supposed -that the phosphorescence of the sea is due in part to the presence of -these animals. The latter may be obtained from all depths, down to -several thousand fathoms. - -The beauty of the radiolarians as a class lies in the wonderful shells -that protect the great majority of them. These shells are composed not -of carbonate of lime, as is the case with foraminifers, but of silex or -silica, a substance that is not acted on by the strongest mineral acids. -They are of the most exquisite shapes, and exhibit a great variety of -forms. Some resemble beautifully sculptured spheres, boxes, bells, cups, -&c.; while others may be likened to baskets of various ornamental -design. In every case the siliceous framework consists of a number of -clusters of radiating rods, all united by slender intertwining threads. - -It is not all the radiolarians, however, that produce these beautiful -siliceous shells. A few have no skeleton of any kind, while others are -supported by a framework composed of a horny material, but yet -transparent and glassy in appearance. - -The sizes of the shells vary from about one five-hundredth to one half -of an inch; but, of course, the larger shells are those of colonies of -radiolarians, and not of single individuals, just as we observed was the -case with the foraminifers. - -Those in search of radiolaria for examination and study should, whenever -possible, obtain small quantities of the dredgings from deep water. -Material brought up by the trawl will often afford specimens; but, -failing these sources of supply, the muddy deposit from deep niches -between the rocks at low-water mark will often provide a very -interesting variety. - -Place the mud in a glass vessel, and pour on it some nitric acid -(aqua-fortis). This will soon dissolve all calcareous matter present, -and also destroy any organic material. A process of very careful washing -is now necessary. Fill up the vessel with water, and allow some time for -sedimentary matter to settle. Now decant off the greater part of the -water, and repeat the process several times. By this means we get rid of -the greater part of the organic material, as well as of the mineral -matter that has been attacked by the acid; and if we examine the final -sediment under the microscope, preferably in a drop of water, and -covered with a cover-glass, any radiolarians present will soon reveal -themselves. - -It is often possible to obtain radiolarian shells, as well as other -siliceous skeletons, through the agency of certain marine animals. The -bivalve molluscs, for example, feed almost entirely on microscopic -organisms; and, by removing such animals from their shells, and then -destroying their bodies with aqua-fortis, we may frequently obtain a -sediment composed partly of the skeletons referred to. - -There remains one other class of protozoons to be considered, viz. the -_Infusorians_--the highest class of the sub-kingdom. In this group we -observe a distinct advance in organisation; for, in the first place, the -infusorians are enclosed in a firm cuticle or skin, which forms an -almost complete protective layer. Within this is a layer of moderately -firm protoplasm, containing one or more cavities that contract at -intervals like a heart. Then, in the interior, there is a mass of softer -material with cavities filled with fluid, two solid bodies, and numerous -granules. - - [Illustration: FIG. 63.--THREE INFUSORIANS MAGNIFIED] - -In these creatures we find, too, a distinct and permanent mouth, usually -funnel-shaped, leading to the soft, interior substance, in which the -food material becomes embedded while the process of digestion proceeds. -Here, then, for the first time, we meet with a special portion of the -body set apart for the performance of the work of a stomach; and, -further, the process of digestion being over, the indigestible matter is -ejected through a second permanent opening in the exterior cuticle. - -Again, the infusorian does not move by means of temporary pseudopods, as -is the case with the lower protozoons, but by means of minute hair-like -processes which permanently cover either the whole of the body, or are -restricted to certain portions only. These little processes, which are -called _cilia_, move to and fro with such rapidity that they are hardly -visible; and, by means of them the little infusorian is enabled to move -about in its watery home with considerable speed. - -In some species a few of the cilia are much larger than the others, and -formed of a firmer material. These often serve the purpose of feet, and -are also used as a means by which the little animal can anchor itself to -solid substances. - -As with the lower protozoons, the infusoria multiply by division; but, -in addition to this, the nucleus may sometimes be seen to divide up into -a number of minute egg-like bodies, each of which, when set free, is -capable of developing into a new animal. Should the water in which -infusorians have been living evaporate to dryness, the little bodies -just mentioned become so many dust particles that may be carried away by -air currents; but, although dry, they retain their vitality, and develop -almost immediately on being carried into a suitable environment. - -Infusorians are so called because they develop rapidly in infusions of -various vegetable substances; and those who desire to study their -structure and movements with the aid of a microscope cannot do much -better than make an infusion by pouring boiling water on fragments of -dried grass, and leaving it exposed for a few days to the warm summer -atmosphere. The numerous germs floating in the air will soon give rise -to abundance of life, including several different species of infusoria, -varying from 1/30 to 1/2000 of an inch in length. - -Fresh-water pools and marshes provide such an abundance of infusoria -that the animals are generally obtained for study from these sources, -and a few of the common and most interesting species inhabiting fresh -water have already been described in a former work. Nevertheless, the -sea is abundantly supplied with representatives of the class, and it is -certain that the beautiful phosphorescence sometimes observed in the sea -at night is in part due to the presence of luminous infusoria, some of -which appear to have an aversion to sunlight, retiring to a depth during -the day, but rising to the surface again after sunset. - - [Illustration: FIG. 64.--A PHOSPHORESCENT MARINE INFUSORIAN - (_Noctiluca_), MAGNIFIED] - - - - - CHAPTER VIII - - _BRITISH SPONGES_ - - -It seems to be the popular opinion that sponges are essentially natives -of the warmer seas, and it will probably be a surprise to many young -amateur naturalists to learn that there are about three hundred species -of this sub-kingdom of the animal world to be found on our own shores. -It must not be thought, however, that they are all comparable with the -well-known toilet sponges in regard to either size or general form and -structure, for some of them are very small objects, no larger than about -one-twentieth of an inch in diameter, and some form mere incrustations -of various dimensions on the surfaces of rocks and weeds, often of such -general appearance that they would hardly be regarded as animal -structures by those who have not studied the peculiarities of the group. - -Sponges are known collectively as the _Porifera_ or _Polystomata_, and -constitute a separate sub-kingdom of animals of such distinct features -that they are not readily confused with the creatures of any other -group. Their principal characteristic is expressed by both the group -names just given, the former of which signifies 'hole-bearing,' and the -latter 'many openings'; for in all the members of the sub-kingdom there -are a number of holes or pores providing a means of communication -between the body cavity or cavities and the surrounding water. Most of -these holes are very small, but there is always at least one opening of -a larger size at the anterior end. - -It will be seen from what we have just stated that sponges exhibit a -distinctly higher organisation than the _protozoa_ described in the last -chapter, inasmuch as they possess a permanent body-cavity that -communicates with the exterior; but in addition to this there are many -points of differentiation of structure that denote a superior position -in the scale of life. - -In order to ascertain the general features of a sponge we cannot do -better than select one of the simplest forms from our own shores. If we -place the live animal in a glass vessel of sea water, and examine it -with a suitable magnifying power, we observe a number of minute pores -scattered over its whole surface; and a much larger opening at the free -end. The animal is motionless, and exhibits no signs of life except that -it may contract slightly when touched. The water surrounding the sponge -also appears to be perfectly still, but if we introduce some fine -insoluble powder, such as precipitated chalk, or a drop of a soluble -dye, the motion of the suspended or soluble material will show that the -water is passing into the sponge through all the small pores, and that -it is ejected through the larger opening. - -On touching the sponge we observe that it is of a soft, gelatinous -consistence throughout, or if, as is often the case, the body is -supported by a skeleton of greater or less firmness, a gentle -application of the finger will still show that this framework is -surrounded by material of a jelly-like nature. This gelatinous -substance is the animal itself, and a microscopic examination will show -that its body-wall is made up of two distinct layers, the inner -consisting of cells, many of which possess a cilium or whip-like -filament that protrudes from a kind of collar, its free extremity -extending into the body-cavity. - - [Illustration: FIG. 65.--SECTION OF A SIMPLE SPONGE] - -These minute cilia are the means by which the water currents just -described are set up. By a constant lashing movement they urge the fluid -contained in the body-cavity towards the larger hole, thus causing the -water to flow in through the numerous small pores. This circulation of -sea water through the body-cavity of the sponge is the means by which -the animal is supplied with air and food. Air is, of course, absorbed -from the water by the soft material of the external layer of the body, -but the constant flow of fresh water through the body-cavity enables -this process of respiration to go on with equal freedom in the interior. -The mode of feeding of the sponge is very similar to that of the -_protozoa_. Organic particles that are carried into the body-cavity, on -coming in contact with the cells of the internal layer, are absorbed -into their protoplasm by which they are digested. Thus the sponge may be -compared to a mass of protozoon cells, all united into a common colony -by a more or less perfect coalescing of the cell-substance, some of the -units being modified in structure for the performance of definite -functions. The air and food absorbed by any one cell may pass readily -into the surrounding cells, and thus each one may be said to work for -the common weal. - - [Illustration: FIG. 66.--DIAGRAMMATIC SECTION OF A PORTION OF A - COMPLEX SPONGE] - -The description just given applies only to the simplest of the sponges, -and we have now to learn that in the higher members of the group the -structure is much more complicated. In these the surface-pores are the -extremities of very narrow tubes which perforate both layers of the -body-wall and then communicate with wider tubes or spaces within, some -of which are lined with the ciliated cells above described. These -spaces, which are sometimes nearly globular in form, and often arranged -in groups with a common cavity, communicate with wider tubes which join -together until, finally, they terminate in a large opening seen on the -exterior of the sponge. Hence it will be seen that the water entering -the minute pores of the surface has to circulate through a complicated -system of channels and spaces, some of which are lined with the ciliated -cells that urge the current onwards before it is expelled through the -large hole. Further, imagine a number of such structures as we have -described growing side by side, their masses coalescing into one whole, -their inner tubes and spaces united into one complex system by numerous -inter-communications, and having several large holes for the exit of the -circulating water, and you then have some idea of the general nature of -many of the more complex sponges to be found on our shores (see fig. -66). - - [Illustration: FIG. 67.--HORNY NETWORK OF A SPONGE, MAGNIFIED] - -But even this is not all, for as yet we have been regarding the sponges -as consisting of animal matter only, whereas nearly all of them possess -some kind of internal skeleton for the support of the soft, gelatinous -animal substance. The skeleton consists of matter secreted by certain -cells from material in the water and food, and is either horny, -calcareous, or siliceous. The horny skeleton is formed of a network of -fibres of a somewhat silky character, and often, as in the case of the -toilet sponges, highly elastic; but it is sometimes so brittle that the -sponge mass is easily broken when bent. The fibres of this framework -support not only the outer wall of the sponge, but also the walls of all -the internal tubes and spaces, which are often of so soft a nature that -they would collapse without its aid. - -The other forms of skeletons consist of minute bodies of carbonate of -lime or of silica, respectively, which assume certain definite shapes, -resembling stars, anchors, hooks, pins, spindles, &c., and are known as -_spicules_. Such spicules are usually present in those sponges that have -horny skeletons, but in others they form the entire skeleton. - -Sponges sometimes increase by division, a part being separated from the -parent mass and then developing into a complete colony; and they may be -reproduced artificially to almost any extent by this method, each piece -cut off, however small, producing a new sponge. They also increase by a -process of 'budding,' the buds produced sometimes remaining attached to -the original colony, thus increasing its size, but on other occasions -becoming detached for the formation of new colonies on a different site. -In addition to these methods of reproduction there are special cells in -a sponge that possess the function of producing eggs which are ejected -through the larger holes. The eggs are usually developed in the autumn, -and, after being ejected, swim about freely for a time, after which they -become fixed to rocks or weeds, and produce sponges in the following -year. The eggs may often be seen towards the end of the summer by -cutting through a sponge, or by carefully pulling it asunder. They are -little rounded or oval bodies, of a yellowish or brownish colour, -distinctly visible to the naked eye, occupying cavities in the interior. - -Sponges are classified according to the composition of the skeleton and -the forms of the spicules, the chief divisions being:-- - - 1. The CALCAREOUS Sponges (_Calcarea_). Skeleton consisting of - spicules of carbonate of lime in the form of needles and - three-or four-rayed stars. - - 2. The SIX-RAYED SPONGES (_Hexactinellida_). Skeleton of six-rayed - glassy spicules. - - 3. COMMON SPONGES (_Demospongia_). Skeleton horny, flinty, or - entirely absent. - -The first of these divisions contains about a dozen known British -species, which are to be found on the rockiest shores, attached to -stones, weeds, or shells, generally hidden in very secluded holes or -crevices, or sheltered from the light by the pendulous weeds. They -should be searched for at the lowest spring tide, particular attention -being given to the under surfaces of large stones, narrow, dark -crevices, and the roofs of small, sheltered caves. They may be readily -recognised as sponges by the numerous pores on the surface, though these -are often hardly visible without a lens, and the calcareous nature of -the skeleton may be proved by dropping a specimen into dilute -hydrochloric acid, when the carbonate of lime will speedily dissolve, -the action being accompanied by the evolution of bubbles of carbonic -acid gas. - -If calcareous sponges are to be preserved for future reference, they may -be placed in diluted spirit, in which case the animal matter, as well -as the mineral substance, will be preserved with but little alteration -in the natural appearance and structure. A specimen which has been -decalcified by means of acid, as above described, may also be preserved -in the same manner; and small portions of this will serve for the -microscopic study of the animal portion of the sponge. If the skeleton -only is required, the sponge is simply allowed to dry, when the soft -animal substance, on losing its contained water, will leave hardly any -residue; or, better, allow the calcareous sponge to macerate in water -for some days for the animal substance to decompose, and then, after a -few minutes in running water, set it aside to dry. - - [Illustration: FIG. 68.--_Grantia compressa_] - - [Illustration: FIG. 69.--SPICULES OF _Grantia_, MAGNIFIED] - -Small portions of the skeleton, examined under the microscope, will show -the nature of the calcareous spicules of which it is composed. These -consist of minute needles and stars, the latter having generally either -three or four rays. - -We give figures of three of the calcareous sponges of our shores, the -first of which (_Grantia compressa_) resembles little oval, flattened -bags, which hang pendulous from rocks and weeds, sometimes solitary, but -often in clusters. The smaller openings are thickly scattered over the -flat sides of the bag, and the larger ones, through which the water is -expelled, around the margin. When the sponge is out of the water and -inactive, the two opposite sides of the bag are practically in contact, -but, when active, the cavity is filled with water by means of the -whip-cells that line it, and the sides of the sponge are then more or -less convex. - - [Illustration: FIG. 70.--_Sycon ciliatum_] - -The ciliated sycon (_Sycon ciliatum_), fig. 70, though of a very -different appearance externally, is similar in structure to _Grantia_. -It is also found in similar situations, and is not uncommon on many -parts of the South Coast, from Weymouth westwards. The other example, -_Leucosolenia botryoides_, shown in fig. 71, is a branching calcareous -sponge, consisting of a number of tubes, all united to form one common -cavity which is lined throughout with whip-cells. It is usually found -attached to weeds. - - [Illustration: FIG. 71.--_Leucosolenia botryoides_, WITH PORTION - MAGNIFIED] - -Nearly all our British sponges belong to the group _Demospongia_--common -sponges; but the members of this group present a great variety of form -and structure. Most of them have a skeleton consisting of siliceous -spicules, but some have a horny skeleton, somewhat after the nature of -that of the toilet sponges; and others, again, have fleshy bodies -entirely, or almost entirely, unsupported by harder structures. They are -sometimes known collectively as the _Silicia_, for the greater number of -them have skeletons consisting exclusively of siliceous matter, while -the so-called horny sponges usually have spicules of silica -intermingled with the horny substance, and even those which are -described as having no skeleton at all sometimes contain scattered -spicules of silex. - - [Illustration: FIG. 72.--_Chalina oculata_] - -As the spicules of sponges are in themselves beautiful objects, and are -important to the naturalist, inasmuch as they form a basis for the -classification of sponges, it is well to know by what means they may be -separated from the animal for microscopic examination. The separation is -based on the fact that nitric acid (aqua-fortis) will destroy organic -matter while it has not the slightest action on silica. In some of our -common horny sponges the fibres are so transparent that, when teased out -and placed under the microscope, the siliceous spicules may be seen -embedded within them, but the spicules, both in these and the fleshy -sponges, may be separated completely from the animal matter by putting a -fragment of the sponge in a test-tube, covering it with nitric acid, and -boiling it for a short time. The tube should then be filled up with -water and allowed to stand undisturbed for a time, after which the -liquid is poured off gently from the sediment. If the sediment is then -put under the microscope on a slip of glass, it will be seen to consist -of grains of sand, of which there is always a considerable amount in the -pores and cavities of a sponge, and the siliceous spicules. - -Among the common objects of the sea shore is the horny skeleton of the -sponge _Chalina oculata_, which is frequently washed on the beach by -the waves, especially after storms. This sponge is not likely to be seen -between the tide-marks except at the lowest spring tide, when it may be -found suspended in a sheltered crevice or cave. The skeleton consists of -a fine network of horny fibres, in the centre of which lie the spicules, -imbedded in the horny material. The spicules are short and straight, -tapering at both ends. - - [Illustration: FIG. 73.--_Halichondria panicea_] - -The Bread-crumb sponge (_Halichondria panicea_) is even more common, for -it is to be found on every rocky coast, encrusting weeds and rocks, -often considerably above low-water mark. It is of a yellowish or pale -greenish colour, and forms an incrustation varying in thickness from -one-twentieth of an inch to half an inch or more; and, like most -sponges, should be looked for in narrow crevices, under heavy growths of -weeds, or in other situations where it is protected from the light. -Sometimes its free surface is unbroken, except, of course, by the minute -pores, and, here and there, the larger openings that serve for the -outgoing currents; but when it is found encrusting a rock in patches of -considerable size, the larger holes all occupy the summit of a little -cone resembling a miniature volcano with its crater. This sponge is -easily removed from the rock with the aid of a blunt broad-bladed knife, -and retains its natural appearance to perfection if preserved in -methylated spirit. Its horny skeleton is of a very compact nature, and -the spicules are minute siliceous needles pointed at both ends. - -Rambling on the sea beach we frequently meet with old oyster and other -shells perforated by a number of circular holes about the size of a -pin's head or less, and chalk and limestone rocks also are seen -similarly bored. On breaking into or grinding down the substance we find -that the openings are the ends of channels that form a network of canals -and chambers, some of which are so near the surface that they are -covered by an exceedingly thin layer of the calcareous substance. These -canals and chambers form the home of the Boring Sponge (_Cliona_), -which, although a very soft-bodied animal, has itself excavated them. - - [Illustration: FIG. 74.--SPICULES OF _Halichondria_, MAGNIFIED] - - [Illustration: FIG. 75.--AN OYSTER SHELL BORED BY _Cliona_] - -The manner in which the _Cliona_ excavates such a complicated system of -passages in so hard a material has naturally raised a considerable -amount of curiosity, and those who have studied the matter are divided -in opinion as to whether the work is done by chemical or by mechanical -action. - -Some of those who advocate the chemical theory suppose that an acid -fluid is secreted by the sponge, and that the carbonate of lime forming -the shell or stone is thereby dissolved; but such advocates have, as -yet, failed to detect the presence of any acid substance in the body of -the animal. Others ascribe the action to the solvent power of carbonic -acid gas. This gas certainly has the power of dissolving carbonate of -lime, as may be proved by a very simple experiment: Pour a little lime -water into a glass, and blow into it through a glass tube. The lime -water speedily becomes milky in appearance, the lime having been -converted into particles of chalk or carbonate of lime by union with the -carbonic acid gas from the lungs. Continue to blow into the liquid for -some time, and the carbonate of lime will slowly disappear, being -gradually dissolved by the excess of the gas--the gas over and above -that required for the formation of the carbonate. Thus, it has been -said, the carbonic acid gas evolved as a product of the respiration of -the sponge is the agent by which the channels are excavated. Whatever be -the acid to which this power is ascribed, whether it be the carbonic -acid or a special acid fluid secreted for the purpose, there is still -this difficulty in the way of accepting the theory, namely, that an -acid, though it has the power of dissolving the mineral matter of a -shell--the carbonate of lime--has no action on the laminæ of animal -substance that form part of the structure. If we put the shell of a -mollusc in hydrochloric or _dilute_ nitric acid, we obtain, after the -complete solution of the carbonate of lime, a substantial residue of -animal matter which the acid does not touch, but in the case of _Cliona_ -both animal and mineral substances yield to its power. - - [Illustration: FIG. 76.--SPICULES OF _Cliona_] - -Those who favour the mechanical theory assert that the material is worn -away by siliceous particles developed by the sponge, and kept in -constant motion as long as the animal lives; and the theory is supported -by the statement that, in addition to the spicules of silica, which are -pin-shaped, and occupy the interior of the animal, there are little -siliceous granules scattered on the surface of the sponge which are kept -in constant motion resembling that of cilia; and the minute particles of -carbonate of lime that form a dusty deposit within the galleries are -supposed to be the product of the rasping or drilling action of these -granules. - -The pin-shaped spicules of _Cliona_ may be obtained for microscopic -examination by breaking any old oyster shell that has formed its home, -and brushing out the dust from the galleries; or, a part of the shell -may be dissolved in acid, and the sediment examined for spicules on a -slip of glass. - - - - - CHAPTER IX - - _THE COELENTERATES--JELLY-FISHES, ANEMONES, - AND THEIR ALLIES_ - - -One of the most interesting groups of marine life is that including -jelly-fishes and anemones. In it are the pretty little sea firs, so -often mistaken for sea-weeds by the youthful admirers of these plants, -who almost always include them in their collection of marine _algæ_; the -transparent, bell-shaped jelly-fishes, which may often be seen in -thousands during the summer, carried by the tides, and swimming gently -by graceful contractions of their bells; and, most beautiful of all, the -lovely anemones--the 'sea flowers' of the older naturalists, by whom -they were regarded as forms of vegetable life. - - [Illustration: FIG. 77.--THREAD CELLS OF A COELENTERATE, MAGNIFIED - 1. Thread retracted 2. Thread protruded] - -The simplest animals of this group are minute jelly-like creatures, of a -more or less cylindrical form, usually fixed at one end, and having a -mouth at the other. The body is a simple hollow cylinder, the wall of -which is made up of two distinct layers, while the cavity within serves -the purpose of a stomach. The mouth is surrounded by a circle of arms or -tentacles by means of which the creature is enabled to capture its prey. -These arms are capable of free movement in every direction, and can be -readily retracted when the animal is disturbed. They are also armed with -minute oval, hollow cells, each of which has a slender filament coiled -up into a spiral within its cavity. Each filament is capable of being -suddenly protruded, thus becoming a free whip-like appendage, and these -are so numerous as to be very effectual in seizing and holding the -living beings on which the animal feeds. This would undoubtedly be the -case even if they were capable of mechanical action only, but, in many -instances at least, they seem to be aided by the presence of some -violent irritant, judging from the rapidity with which the struggling -prey is paralysed when seized, especially in the case of some of the -larger members of the group. - -The simple forms referred to increase by a process of budding, the buds -appearing first as simple swellings on the side of the parent creature, -and afterwards developing a mouth and tentacles, thus becoming exactly -like the adult form. Clusters of eggs also are developed in the outer -layer of the body-wall, and these are set free at intervals, and -produce new individuals. These animals possess no blood system of any -kind, and have no special organs for respiration, but the nutrient -matter absorbed from the body-cavity permeates the soft structures of -the flower-like body, and the oxygen required for respiratory purposes -is readily absorbed from the surrounding water. - - [Illustration: FIG. 78.--THE SQUIRREL'S-TAIL SEA FIR (_Sertularia - argentea_), WITH A PORTION ENLARGED] - -The higher coelenterates differ in certain particulars from the lower -forms just referred to. Thus, they frequently have a large number of -tentacles around the mouth, often arranged in several distinct whorls. -They have also a stomach separate from the general body-cavity, but -communicating with the latter below; and the body-cavity is divided into -compartments by a number of radiating partitions. Some, also, develop a -hard, stony skeleton by secreting carbonate of lime obtained from the -water in which they live. - - [Illustration: FIG. 79.--_Sertularia filicula_] - -We often see, when collecting on the beaches of rocky coasts, and -especially after storms, a number of vegetable-like growths, of a -greyish or brownish colour, each consisting of one or more main stalks -bearing a number of delicate branches. Some of them, by their peculiar -mode of growth, have suggested the name of sea firs, and a few of these, -together with other animals of the same group, may readily be recognised -by the accompanying illustrations. They are the objects already referred -to as being commonly included in collections of sea-weeds by young -naturalists, but they are in reality the horny skeletons of colonies of -coelenterates of the simplest type, belonging to the division -_Hydrozoa_. - - [Illustration: FIG. 80.--_Sertularia cupressina_] - -If we examine them with a lens we find that there are little cup-like -bodies projecting from each portion or branch of the stem-like -structure, and that the stem itself is hollow, with a communicating pore -at the base of each cup. This constitutes the skeleton only of the -colony--the dead matter, so to speak, which persists after the living -creatures have perished; but if the specimens collected have been -obtained fresh from the sea, placed in a glass of sea water, and then -examined with the aid of a lens, little jelly-like _hydroids_ or -_polypites_ will be seen to protrude from the cups, and extend their -short arms in search of food. - - [Illustration: FIG. 81.--THE HERRING-BONE POLYPE (_Halecium - halecinum_)] - -Each of the little creatures has a tubular stalk which passes through -the hole at the base of the cup, and is continuous with a tube of -gelatinous material in the interior of the horny stem, and thus each -member of the colony is directly connected with all the others, so that -any nutrient matter collected and digested by one member may be absorbed -into the central tube for the nourishment of the entire company of -little socialists, the activity of the one being thus made to compensate -for the laziness or incompetency of others. And this provision seems to -be absolutely necessary for the well-being of the colony as a whole, for -a close examination will often show that a kind of division of labour -has been established, since it includes two or three distinct kinds of -polypites, each adapted for the performance of a certain function. Thus, -in addition to the feeding or nutritive members of the community, there -are some mouthless individuals whose sole function seems to be the -production of eggs for the propagation of the species, while others, -also mouthless, develop an enormous number of stinging cells, probably -for the protection of the whole community against its enemies, and these -must therefore be provided, as we have seen they are, with a means by -which they may derive nourishment through the agency of the feeding -polypites. - - [Illustration: FIG. 82.--_Tubularia indivisa_] - - [Illustration: FIG. 83.--THE BOTTLE BRUSH (_Thuiaria thuja_)] - -When the eggs are liberated from what we may call the reproductive -members, they are carried away by the currents or tides, and soon -develop into little _larvæ_ which are very unlike the parent, since they -are covered with minute vibratile cilia by means of which they can swim -freely. This they do for a period, and then settle down, lose their -cilia, become stalked, and thus constitute the foundation of a new -colony. A tubular stalk grows upward from its root, new members are -added as outgrowths or buds from their progenitor, and so the growth -proceeds until an extensive colony of hundreds of individuals has been -formed. - -We have spoken of the hydroid communities as being washed up on the -beaches of our rocky coasts, but the collector of these interesting -objects should not depend on such specimens for purposes of study. It is -undoubtedly true that splendid examples of the sea firs and their allies -are frequently washed up by the waves, including some species that -inhabit deep water, and which are, consequently, not to be found by the -ordinary collector in their proper habitat, and that these may often be -secured with the polypites still alive; but several species are to be -obtained between the tide-marks, especially at extreme low water, -growing on rocks, weeds, and shells; and we have often met with good -specimens, still alive, attached to the shells of whelks, scallops, &c., -in fishmongers' stores, even in inland towns. - - [Illustration: FIG. 84.--_Antennularia antennia_] - -Sometimes individual polypites become detached from a colony, and -develop into little umbrella-shaped jelly-fishes, about a fifth of an -inch in diameter; and these float about freely, keeping themselves near -the surface by rhythmic contractions of their 'bells,' the margins of -which are fringed by numerous fine tentacles. The mouth is situated -centrally on the under side, and is surrounded by a circular canal from -which proceed radiating tubes; and pigmented spots, supposed to be -rudimentary eyes, are formed round the edge. These little bodies are -called _Medusoids_, and may frequently be seen floating round our coasts -towards the end of the summer. In the water they are almost invisible on -account of the extreme transparency of their bodies; but if a muslin -net be drawn through the water from the stern of a boat, and the net -then gently turned inside out in a vessel of sea water, a number of -medusoids may be obtained for examination. These creatures produce eggs -which yield small ciliated larvæ that swim about freely for a time, and -then settle down and establish stalked colonies as previously described. - -The larger jelly-fishes or _Medusæ_ so frequently seen floating in -enormous numbers near the surface of the sea during the summer months -are allied to the medusoids. Their bodies are so soft that it is a -difficult matter to remove them from the water without injury, and when -removed their graceful forms are completely destroyed by the pressure of -their own weight. When left stranded on the beach, as is often the case, -they seem to dissolve almost completely away, so readily does the soft -animal tissue disintegrate in the large proportion of water, which forms -about 95 per cent. of the weight of the whole body. - -Those who desire to examine the nature and movements of the medusæ will -find it necessary to observe them in water. The creatures may be lifted -out of the sea in a vessel placed below them, and then transferred to a -glass tank or a still rock pool by submerging the vessel and allowing -them to float out. It will then be observed that the mouth is situated -at the summit of a tube that projects from the middle of the under side -of the 'bell,' and is surrounded by lobed or frilled lips. Marginal -tentacles also generally fringe the edge of the bell, projecting -downwards into the water. Round the circumference of the body may be -seen a circular canal, from which several tubes converge towards, and -communicate with, the cavity of the stomach. - -When a medusa is inactive, its body gradually sinks to the bottom, being -usually slightly heavier than the water in which it lives; but it is -enabled to keep afloat by those rhythmic contractions of the bell with -which we are so familiar. It seems that the medusæ are very sensitive to -various external conditions, for they frequently disappear -simultaneously from the surface water, and as suddenly reappear in -shoals when the conditions are more favourable; but it is difficult to -understand the causes which give rise to these remarkable movements. - -The medusæ are often termed the _Acalephæ_--a word which signifies -'nettles,' and they are popularly known as sea nettles. They all possess -stinging cells, which are distributed most thickly in the tentacles, and -some of the larger species are undoubtedly able to produce an -impression on the bodies of unwary bathers, while almost all have the -power of paralysing the living prey on which they feed. - -By far the commonest of the jelly-fishes of our seas is the beautiful -blue medusa--_Aurelia aurita_. This species appears in enormous shoals -during the summer, and large numbers are washed upon flat, sandy -beaches. They vary in size from two or three inches to nearly a foot in -diameter, and may be recognised from our illustration. The 'bell' is -umbrella-shaped, and is so transparent that the stomach with its -radiating canals may be seen through its substance. Around the margin -there are little pigment spots which are supposed to be rudimentary -eyes, and little cavities, containing a clear fluid, that are thought to -serve the purpose of ears. - - [Illustration: FIG. 85.--_Aurelia aurita_] - -On the under surface may be seen the square mouth, furnished with four -long and graceful frilled lips, which are richly supplied with stinging -cells; also the four ovaries or egg-producing organs, rendered -conspicuous by their violet colouring. - -The life history of _Aurelia_ is most interesting. The eggs are produced -in pouches that communicate directly with the stomach-cavity, and these -give rise to little ciliated larvæ that are ejected through the mouth, -and then swim about freely in the water for a time. After this they -settle at the bottom, lose their cilia, and become little cylindrical -jelly-fishes, fixed by a short stalk-like foot to rocks or weeds. -Numerous tentacles develop as the creatures increase in size, and a -number of transverse furrows appear at the surface. The furrows -gradually increase in depth until, at last, the body is broken up into -several star-like discs, each of which floats away and develops into a -new medusa. - - [Illustration: FIG. 86.--THE EARLY STAGES OF _Aurelia_] - -Other jelly-fishes, some of which are considerably larger than -_Aurelia_, frequent our seas, and are often to be seen stranded on the -beach. Two of these--_Rhizostoma_ and _Chrysaora_--are figured. Although -they differ considerably in form from the blue aurelia, they closely -resemble it in general structure and habits. - - [Illustration: FIG. 87.--_Rhizostoma_] - - [Illustration: FIG. 88.--_Chrysaora_] - -When strolling on flat, sandy beaches, especially in the spring and -early summer, we commonly see what appear to be little balls of -exceedingly transparent and glassy jelly, no larger than an ordinary -marble. If picked up and examined, we observe that they are not quite -spherical, but oval in form, with a little tubercle at one end, and -eight equidistant bands running from this to the opposite end, like the -meridians on a globe. - -This extremely beautiful little creature is one of the coelenterates, -belonging to the division _Ctenophora_, or comb-bearing jelly-fishes, so -called because they possess comb-like ciliated plates, and is called the -Globular Beroe (_Cydippe pileus_). - -The ctenophores are very active creatures, swimming freely in the open -seas by means of their numerous cilia; and, although of such delicate -structure, are very predaceous, devouring small crustaceans and other -marine animals. They are usually globular in form, but some are like -long ribbons, and almost all are remarkable for their wonderful -transparency, which renders them nearly invisible when floating in -water. They have not the power of stinging or paralysing their prey, as -the medusæ have, but their fringed arms are provided with adhesive cells -by which they hold their prey tenaciously. - - [Illustration: FIG. 89.--_Cydippe pileus_] - -In order to observe the form and habits of the Beroe we transfer it to a -vessel of sea water, when it immediately displays its regular spheroid -form, and its eight rows of comb-like plates which form the meridians -before alluded to. Its mouth is situated on the little tubercle at what -we may call the lower pole, for it is the habit of the Beroe to swim in -an inverted position, and the digestive cavity may be seen through its -glassy body. - -At first no appendages of any kind are visible, but soon the animal -protrudes two long and exceedingly slender arms, fringed with slender -gelatinous threads, from two cavities, at opposite sides of the body, -into which they can be withdrawn. A close examination will also reveal -the rapid movements of the cilia of its combs, and it is remarkable that -these do not always work together, the animal being able to move any of -its plates independently, and to reverse their motion when occasion -requires. It has no tentacles corresponding with those of jelly-fishes -and anemones, but is assisted in the capture of its prey by its two long -arms, the chief use of which, however, seems to be that of a rudder for -steering. - -If the Beroe is left out of water for some time, the water which forms -such a large proportion of its body evaporates, leaving an almost -imperceptible residue of solid matter; and if left in water after it is -dead, its substance rapidly dissolves away, leaving not the slightest -trace of its presence. There seems to be no satisfactory way of -preserving this beautiful form of animal life. If placed in strong -spirit the water is rapidly extracted from its body, and its animal -substance shrivelled to a minute, shapeless mass; while in weak spirit -and in other fluid preservatives it becomes more or less distorted, and -deprived of its beautiful transparency, or else it disappears -altogether. - -We now come to the great favourites among the coelenterates--the -beautiful anemones-the animated flowers of the ocean, remarkable not -only for their lovely flower-like forms, but also for the great variety -of colour and of habits which they display. These, together with the -corals, form the division of the coelenterates known as the -_Zoantharia_, characterised by the possession of simple tentacles, the -number of which is a multiple of either five or six. The latter differ -from the former mainly in the power of secreting a calcareous skeleton -which remains attached by its base after the animal substance has -decayed. - -The expanded anemone exhibits a more or less cylindrical body, attached -by a suctorial base to a rock or some other object, and a broad circular -disc above. In the centre of this disc is the mouth, surrounded by the -tentacles, often very numerous, and arranged in one or more whorls. When -the animal is inactive the tentacles are usually completely withdrawn, -and the body contracted into a semiglobular or pear-shaped mass which is -very firm to the touch. - -The general internal structure of an anemone may be made out by simple -dissections, and the examination conducted with the specimen submerged -in water. A longitudinal section will show that the body is a double -tube, the outer being formed by the body-wall, and the inner by the -wall of the stomach. Thus there is a body-cavity distinct from that of -the stomach, but the two will be seen to communicate below, since the -stomach-wall does not extend as far down as the base. It will be seen, -too, that the body-wall is made up of two distinct layers--an outer -one, that is continued inward at the mouth to form the inner wall of the -stomach, and an inner one that lines the whole of the body-cavity. The -latter contains the muscular elements that enable the anemone to -contract its body. - -When the animal is expanded, the whole interior is filled with sea -water, as are also the tentacles, which are hollow tubes, really -extensions of the body-cavity, and formed by prolongations of the same -two layers that constitute the body-wall. As it contracts this water is -expelled, partly through the mouth, and partly through small openings -that exist at the tips of the tentacles. - - [Illustration: FIG. 90.--SECTION OF AN ANEMONE - _t_, tentacles; _m_, mouth; _s_, stomach; _b c_, body-cavity - _p_, mesentery; _o_, egg-producing organ] - -The outer layer of the body-wall is provided with stinging cells which -serve not only to protect the anemone from its enemies, but also to aid -it in the capture of its prey, for which latter purpose they are -distributed in much greater abundance in the tentacles. - -The body-cavity is divided into a number of communicating compartments -by means of vertical partitions running from the body-wall and -converging towards the centre of the cavity. These are called -mesenteries, and are extensions of the inner layer of the body-wall. -Five or six of these are larger than the others, extending from disc to -base, and are called _primary mesenteries_. Between these are an equal -number of smaller _secondary mesenteries_; and, sometimes, a third set -of still smaller _tertiary mesenteries_. - -These internal partitions are best displayed in a transverse section of -the body, which shows the double tube formed by the walls of the body -and the stomach, together with the wheel-like arrangement of the -mesenteries. At one time all animals that had a radial symmetry--the -regular arrangement of parts round a common centre--were grouped -together under the title of _Radiata_; but it has since been recognised -that the creatures of this group exhibited such a great diversity of -structure that they have been re-classified into two main divisions, one -of which constitutes the coelenterates which we are at present -considering, and the other containing such creatures as star fishes and -sea urchins. - - [Illustration: FIG. 91.--STINGING CELLS OF ANEMONE, HIGHLY MAGNIFIED - _a_ and _c_, with thread protruded; _b_, with cell retracted] - - [Illustration: FIG. 92.--DIAGRAMMATIC TRANSVERSE SECTION OF AN ANEMONE - _S_, stomach; _bc_, body-cavity; _m'_, _m''_, _m'''_, primary, - secondary, and tertiary mesenteries] - - [Illustration: FIG. 93.--LARVA OF ANEMONE] - -On the surface of the mesenteries of the anemone may be seen the ovaries -or egg-producing organs. These discharge the ova into the general -body-cavity, after which they are ejected through the mouth. The embryos -are minute jelly-like creatures that have an active existence, swimming -about freely in the ocean by means of vibrating cilia, but after this -period of activity they settle down and fix themselves, gradually -assuming the adult form common to the species. - -The habits of sea anemones are particularly interesting, and it will -well repay anyone to make a study of these animals in their natural -haunts as well as in the aquarium. The gentle swinging of the tentacles -when searching for food, the capture and disposal of the prey, the -peculiar modes of locomotion, and the development of the young, are -among the chief points of interest. As regards locomotion, the usual -method of moving from place to place is by an exceedingly slow gliding -of the base or 'foot'; and while some anemones are almost constantly on -the move, others hardly ever stir from the secluded niche in which they -have taken up their abode. - -Sometimes an anemone will detach itself from the rock, and drag itself -along, but very slowly, by means of its tentacles, sometimes inverting -its body and walking on its head, as it were, and though one may never -have the opportunity of witnessing this manoeuvre on the shore, we have -found it far from an uncommon occurrence in the aquarium. - -The natural food of anemones consists of small crustaceans, such as -shrimps, and crabs, molluscs, small fishes, and in fact almost every -kind of animal diet, and there need never be any difficulty in finding -suitable viands for species kept in captivity. It is really astonishing -to see what large morsels they can dispose of with the assistance of -their extensile mouths and stomachs. It is not even necessary, indeed, -that the morsel be so small as to be entirely enclosed by the walls of -its digestive cavity, for the anemone will digest one portion while the -other remains projecting beyond its mouth. Further, it will even attack -bodies which it cannot swallow at all, by protruding its stomach so as -to partially envelope them, and then digesting the portion enclosed. -Indigestible portions of its food, such as the shells of small molluscs, -are ejected through the mouth after the process of digestion has been -completed. - -We have already referred to the reproduction of sea anemones by means of -eggs, but it is interesting to note that they may also increase by a -division of the body into two or more parts, and that this division may -be either natural or artificial. - -If an anemone be cut into halves longitudinally, each half will develop -into a complete animal. If cut transversely, the upper portion will -almost always develop a new suctorial disc, and produce a new individual -complete in every respect; and it has been stated that the basal portion -of the divided animal will also, occasionally, produce a new disc and -tentacles. - -The natural division of the anemone has frequently been spoken of as by -no means an uncommon occurrence, but, as far as our experience of -captive anemones go, this mode of multiplication does not seem to take -place except as the result of some mechanical force applied, or as a -means by which the animal may relieve itself of a solid body that it is -unable to eject. Thus, on one occasion, when a stone had slipped so that -its narrow edge rested across the middle of the disc of a large -_Mesembryanthemum_, the animal, apparently unable to free itself from -the burden, simply withdrew its tentacles and awaited results. In a few -days two individuals were to be seen, one on either side of the stone, -both undoubtedly produced as the result of the pressure applied. This -instance seems to be exactly akin to artificial division, for it is far -more likely that the animal was severed by the simple pressure of the -stone than that it divided itself to be relieved of its burden. - -On another occasion an anemone that had almost entirely surrounded a -mussel on which it had been feeding, gradually released itself of the -shell by a longitudinal division of its body; but here, again, it is -probable that the fission was the result of pressure applied rather than -of any power on the part of the animal. - -A few of the British sea anemones are shown on Plates II. and III., and -although the coloured illustrations will probably suffice for purposes -of identification, yet a short description of each one represented may -be acceptable. - -The most common and most widely distributed species is undoubtedly the -familiar Beadlet (_Actinia mesembryanthemum_--Plate II., figs. 1, 2, 3), -which is to be found on every bit of rocky coast around the British -Isles, and even on some stony beaches where there are no standing rocks -between the tide-marks. - -The colour of this species is exceedingly variable, but the most -abundant variety is of a liver-brown colour, with crimson disc and -tentacles, brilliant blue spots round the margin of the disc, and a line -of bright blue around the base. In others the prevailing colour is deep -crimson, orange, yellowish brown, or green. Fig. 1 represents a variety -commonly known as the Strawberry Beadlet (_Fragacea_), which is -distinguished by its superior size, and in which the dark-red ground is -often conspicuously spotted with green. - -Two members of the same genus are also shown on Plate III. One of -these--_A. glauca_ (fig. 3)--is of a bluish-green colour; while the -other--_A. chiococca_ (fig. 4)--is bright scarlet, with deep crimson -disc and white spots round the disc. - - [Illustration: PLATE II. - - SEA ANEMONES - - 1, 2, 3, Actinia mesembryanthemum. - 4. Caryophyllia Smithii. - 5. Tealia crassicornis. - 6. Sagartia bellis. - 7. Balanophyllia regia. - 8. Actinoloba dianthus.] - -The general form of this genus is that of an expanded flower on a -short column; the name Beadlet is applied on account of the little -bead-like projections on the margin of the disc. The tentacles number -nearly two hundred in a fully grown individual, and are arranged in -several rows; but when the animal is disturbed and the tentacles -retracted, its form is almost hemispherical. - -It is interesting to note that _A. mesembryanthemum_ not only exists in -varieties distinguished by distinct colours, but that the same -individual will sometimes change its tint, as may be observed when it is -kept in the aquarium; and it may be mentioned, by the way, that it is -very easily reared in captivity, either in the natural or the artificial -salt water, for not only may the same individuals be kept alive for -years with only a moderate amount of attention, but their offspring may -be reared without difficulty. - -On Plate II. (fig. 8) are two illustrations of the beautiful _Actinoloba -dianthus_, which grows to a length of five or six inches, and is easily -distinguished by its expanded and frilled disc, its very numerous short -and slender tentacles, and its tall, pillar-like body. Its colour is -somewhat variable, being either salmon, flesh-colour, cream, white, red, -orange, or brownish; but whatever be the tint of the body and tentacles, -the margin of the mouth is always red or orange. When young it may -easily be mistaken for another species, as its disc is not then frilled, -and the tentacles are much fewer in number. - -This pretty anemone usually inhabits deep water, and is frequently -brought in, attached to shells and stones, by trawlers, but it may be -commonly observed in the dark crevices of rocks, a little above -low-water mark, where it is usually seen contracted into a ball, or even -so much flattened that it looks like a mere pulpy incrustation of the -rock. It is very common on the rocky coasts of Dorset, Devon, and -Cornwall, as well as in many parts of Scotland and Ireland. - -Like the Beadlet, it is easily kept alive in the aquarium, where it -commonly multiplies by natural division; but as it does not generally -expand in full daylight, its beauty is often better observed at night by -artificial light. - -On Plate II. (fig. 5) we have an illustration of the beautiful Dahlia -Wartlet (_Tealia crassicornis_), which may be readily recognised by its -thick, banded, horn-like tentacles, and the numerous little adhesive -warts that almost cover the surface of its body. - -This species is as abundant as it is beautiful, for it is to be found in -plenty on almost every rocky coast, where it may be seen in the rock -pools and in the crevices of rocks near low-water mark. The diameter of -its cylindrical body often reaches two or three inches, while the -expanded tentacles embrace a circle of four or five inches. Specimens -even much larger than this are sometimes obtained by dredging in deep -water. - - [Illustration: FIG. 94.--THE TRUMPET ANEMONE (_Aiptasia Couchii_), - CORNWALL; DEEP WATER] - -The 'Dahlia' is not so frequently seen by sea-side collectors as its -abundance would lead one to expect, and this is principally due to the -fact that it not only conceals itself in narrow and out-of-the-way -crevices and angles of rocks, but also that, on the retreat of the tide, -it generally covers itself with small stones, fragments of shells, &c., -held fast to its body by means of its numerous suckers. In this manner -it conceals its beauty so well that the sense of touch, as well as that -of sight, is necessary in determining its whereabouts. As a rule, -however, it does not resort to this method of concealment when it -inhabits deep water, or even a permanent rock pool between the -tide-marks, and thus it is in the latter home where one may expect to -see this sea flower in all its glory, for when permanently covered with -water it will seldom hide its crown, except when alarmed, or when in the -act of swallowing its food. - - [Illustration: FIG. 95.--_Peachia hastata_, S. DEVON] - -It should be noted, too, that the rock pool is the right place in which -to study the habits of this anemone, for it is not nearly so easy to -rear in the artificial aquarium as the species previously described, -and, moreover, it requires a great deal of food. We have found it live -longest in running water, kept cool, and frequently renewed by supplies -fresh from the sea. It may be fed on almost any, if not every, form of -animal life inhabiting a rock pool. A small fish or a prawn is perfectly -helpless when once it is seized by the creature's tentacles. Mussels, -winkles, limpets, &c., are eagerly swallowed, and the indigestible -shells disgorged after the animal substance has been dissolved by the -digestive fluid. Even the active shore crab, armed as it is with a coat -of mail and powerful pincers, is no match for its powerfully adhesive -tentacles; nor do the sharp spines of the prickly urchin preserve it -from so voracious a creature. - -The rocky coasts of Devon and Cornwall are the chief haunts of the -pretty 'Daisy Anemone' (_Sagartia bellis_), and here it is very abundant -in places. This species lives in holes and crevices of the rocks, its -body usually entirely hidden from view, but its dark brown disc, -intersected by bright red radiating lines, and fringed with numerous -small tentacles, fully exposed to view as long as it is submerged. The -length of its body is always adapted to the depth of the hole or crevice -in which the animal lives, and may vary from half an inch to two or -three inches, the diameter of the columns being greatest where the -length is least. - - [Illustration: FIG. 96.--_Sagartia pallida_, DEVON AND CORNWALL] - -Sometimes the 'Daisy' may be seen living a solitary life, having settled -down in a hole just large enough to accommodate it, but more commonly it -is seen in company with several others of its species, occupying a -crevice in a rock pool, and often so closely packed together that the -tentacles of each individual are intermingled with those of its -neighbours, thus exhibiting a more or less continuous cluster or line of -'flowers,' each disc being from one to two or three inches in diameter -when fully expanded. - -On account of the peculiar positions selected by this species, it is not -easily removed without injury, and hammer and chisel are almost always -necessary for its removal; but if it is obtained without injury, and -transferred to the indoor aquarium, but little difficulty will be found -in keeping it alive and in health. It is also very prolific, and a -single specimen placed in the indoor tank will frequently produce a -large number of young. - -The colour of _S. bellis_, like that of many of our anemones, is very -variable, but the species may easily be recognised by the radiating -lines of the disc, and the numerous small tentacles. One variety, -however, deviates considerably in form, colour, and habit from the -normal. It (Plate II., fig. 6) is of a dull yellow colour, and has a -much less graceful form; and, instead of living in the holes and -crevices of rocky coasts, where it would be washed by fresh sea water at -every tide, it inhabits the muddy and foetid waters of narrow inlets of -the sea in the neighbourhood of Weymouth. - - [Illustration: FIG. 97.--_Sagartia nivea_, DEVON AND CORNWALL] - -Three other species of the same genus are represented on Plate III. The -first of these--_Sagartia troglodytes_, sometimes called the -Cave-dweller (fig. 1)--though very variable in colour, may be known by -its barred tentacles, each with a black B-like mark near its base. It -lives in sheltered, sandy, or muddy hollows between the rocks on most -rugged coasts, often with its body entirely buried beneath the sediment; -or, if only partially buried, the projecting portion of the column -concealed by particles that adhere to its suckers. - -The column is usually of an olive colour, striped longitudinally with a -paler tint, and sometimes reaches a length of two inches, while the -diameter of the expanded 'flower' may even exceed this length. - -This anemone is not a very conspicuous object of the shore, since the -exposed portion of its column is usually more or less covered by -sedimentary matter, and the tentacles are generally of a tint closely -resembling that of the surrounding surface. Thus the anemone is -protected from its enemies by its peculiar habit and colouring, while at -the same time the spreading tentacles constitute an unseen but deadly -snare for the unwary victims that come within their range. - - [Illustration: FIG. 98.--_Corynactus viridis_, DEVON AND CORNWALL] - -This species is often difficult to secure without injury on account of -its preference for narrow chinks in awkward situations, but we have -found that it is sometimes easily removed by first clearing away the -surrounding débris, and then gently pushing it from its hold by means of -the finger-nail. It seems, in fact, that its base is occasionally quite -free from the underlying rock, being simply imbedded in sand or mud. In -other cases hammer and chisel are necessary to remove it from its snug -hole. - -If placed in the aquarium it should be allowed to get a foot-hold in a -suitable hole or crevice, which should be afterwards partially filled -with sand. It is not difficult to keep, and although not a showy -species, and having a decided preference for shady places, yet its -habits will be found interesting. - -The Orange-disked Anemone (_Sagartia venusta_) is represented in fig. 2 -of the same plate. It may be easily distinguished by its brilliant -orange-coloured disc, surrounded by white tentacles, which, when fully -expanded, commands a circle of from one to one and a half inches. -South-west Wales is said to be the headquarters of this pretty sea -flower, but we have found it abundant on parts of the north Devon coast, -especially in places between Ilfracombe and Lynton. Like the last -species, it may be termed a cave-dweller, for it delights to hide in -corners and crevices that are so overhung with rocks and weeds that the -light is never strong. - -Yet another species of this genus (_S. rosea_) is depicted in Plate -III., fig. 8. It has been termed the Rosy Anemone, from the brilliant -rosy tint of its numerous tentacles. The column is generally of a dull -brown colour, with suckers scattered over the upper portion, and the -flower reaches a diameter of an inch or more. This anemone may be seen -at rest on overhanging rocks near low-water mark when the tide is out, -its disc only partially hidden, and the tips of its bright tentacles -just exposed. It may be seen on many parts of the Devon coast, and is, -or, at least, was, abundant in localities near Brixham and Shaldon. - -On the same plate is an illustration (fig. 7) of one of the most -abundant and most interesting of our anemones. It is commonly known as -the Opelet, and its scientific name is _Anthea cereus_. Almost everyone -who has done a little collecting on the rocky shores of the south-west -of England, or on the shores of Scotland or Ireland, must have seen this -species, easily distinguished by its long, slender, smooth tentacles, -all of about equal length, and presenting a waxy appearance. These -appendages are usually green and tipped with pink, but sometimes pale -yellow or red, and are of such a length that they cover a circle of five -or six inches. - -This species is decidedly of social disposition, for a number may -generally be seen in a cluster, crowded closely together; and when we -see them, as we often do, occupying a little tide pool that contains -scarcely sufficient water to enable them to give free play to their -tentacles, and exposed for hours to the full blaze of the summer sun, we -naturally form the opinion that they ought to require no special care in -the indoor aquarium. And this is actually the case, for they thrive well -with but little trouble. - -Perhaps the chief interest attached to this anemone is the deadly nature -of its grip. The numerous long tentacles have considerable clinging -power throughout their length, and their paralysing power is very -considerable compared with that of many other species of the same size. -Even the human skin is more or less affected by the irritating influence -of this species, a sensation approaching to a sting being sometimes -produced, and the skin showing visible signs of the injury done. The -grip, too, is so tenacious that tentacles are sometimes torn off when -the hand is quickly withdrawn from their hold. - -Our next example is the Red-specked Pimplet (_Bunodes Ballii_), shown in -fig. 5 of Plate III., which has received its popular name on account of -the numerous longitudinal rows of red-specked warts that run down its -short yellow column, and other red spots on the column itself, between -the rows. Its tentacles are usually pale yellow or white, but sometimes -grey or greenish, and often tinged with pink. - - [Illustration: FIG. 99.--_Bunodes thallia_, WEST COAST] - -This anemone is common on some parts of the coasts of Hampshire, Dorset, -Devon, and Cornwall, as well as on the south coast of the Isle of Wight, -and may be found in secluded crevices of the rocks, or under the large -stones that are scattered on the beach. - -The Gem Pimplet (_Bunodes gemmacea_) is shown on the same plate (fig. -6). It is easily distinguished by the six conspicuous longitudinal rows -of large white warts, between which are several other rows of smaller -ones. The column is pink or brownish, and the thick tentacles are -conspicuously marked by light-coloured roundish spots. It is not -uncommon on the south-west coast of England, where it may be seen in the -rock pools and on the surfaces of rocks between the tide-marks. Both of -the species of _Bunodes_ above mentioned may be kept in the aquarium -without much trouble. - - [Illustration: PLATE III. - - SEA ANEMONES - - 1. Sagartia troglodytes - 2. Sagartia venusta - 3. Actinia glauca - 4. Actinia chiococca - 5. Bunodes Ballii - 6. Bunodes gemmacea - 7. Anthea cereus - 8. Sagartia rosea] - -All the anemones so far briefly described are quite devoid of any kind -of skeleton, the whole body being of a pulpy or leathery consistence, -but some of our British species develop an internal calcareous skeleton, -consisting of a hollow cylinder of carbonate of lime secreted by the -body-wall, and attached to the rock by means of a similar deposit formed -in the base, and also, within the cylinder, of a number of thin plates -attached to the skeleton of the body-wall and projecting inwards towards -the axis, thus resembling, in fact, the skeletons of a number of the -tropical corals with which we are familiar. The animals in question are -often collectively spoken of as British corals. - - [Illustration: FIG. 100.--_Bunodes gemmacea_, WITH TENTACLES - RETRACTED] - -One of the finest of these corals is the Devon Cup-Coral (_Caryophyllia -Smithii_), figured on Plate II. It may be found in many parts of Devon -and Cornwall, attached to the rocks between the tide-marks, often in -very exposed places, but is much more abundant in deep water. - -Its skeleton is white or pale pink, and very hard, and is in itself a -beautiful object. The animal surrounding this stony structure is of a -pale fawn colour, with a white disc relieved by a deep brown circle -round the mouth. The tentacles are conical, almost colourless and -transparent, with the exception of the deep-brown warts scattered -irregularly over them, and are tipped by rounded white heads. - -Of course a hammer and chisel are necessary for the removal of these -corals, but they are hardy creatures, and may be kept for a considerable -time in captivity. Their habits, too, are particularly interesting, and -two or more may sometimes be found with skeletons attached, suggesting -that branched arrangement so common in many of the corals from warmer -seas. - -Another of these stony corals (_Balanophyllia regia_) is shown on the -same plate. It is much smaller than the last species, but exceedingly -pretty. It is also much less abundant, being confined almost exclusively -to the coast of North Devon, and is seldom seen far above the lowest ebb -of the tide. - - [Illustration: FIG. 101.--_Caryophyllia cyathus_] - -Our few brief descriptions of British anemones and corals have been -confined to those species which appear in our coloured plates, but we -have interspersed here and there between the text a few illustrations -which will assist in the identification of other species and also help -to show what a rich variety of form is exhibited by these beautiful -creatures. Some of these inhabit deep water only and are consequently -beyond the reach of most sea-side observers during the ordinary course -of their work; yet they may often be seen in fishing villages, -especially in the south-west, where they are frequently brought in among -the haul of the trawlers, attached either to shells or stones; and live -specimens of these deep-sea anemones may even be seen on the shells of -whelks and bivalve molluscs in the fishdealers' shops of London and -other large towns. - - [Illustration: FIG. 102.--_Sagartia parasitica_] - -One of the species in question--the Parasitic Anemone (_Sagartia -parasitica_) is generally found on the shell of the whelk or some other -univalve; and, if removed from its chosen spot, it will again transfer -itself to a similar shell when an opportunity occurs. This interesting -anemone is usually seen among the dredgings of the trawler, but may be -occasionally met with on the rocky coasts of the south-west, at extreme -low-water mark. Though sometimes seen attached to stones, shells may -undoubtedly be regarded as constituting the natural home of the species, -and many regard the former position as accidental or merely temporary, -and denoting that the animal had been disturbed and removed from its -favourite spot, or that circumstances had recently rendered a change of -lodgings necessary or desirable. Further, the shell selected by this -anemone is almost always one that is inhabited by a hermit crab; and -this is so generally the case that the occasional exceptions to the rule -probably point to instances in which the occupant of the shell had been -roughly ejected during the dredging operations. - - [Illustration: FIG. 103.--THE CLOAK ANEMONE (_Adamsia palliata_) ON A - WHELK SHELL, WITH HERMIT CRAB] - -The peculiar habit of the anemone just referred to makes it an -interesting pet for the aquarium, for if removed from its natural home, -and placed in the aquarium with a hermit crab, it will, sooner or later, -as the opportunity occurs, glide from its hole on the stone or rock, and -transfer itself to its favourite moving home. - -It may be difficult at first to see what advantage can accrue to the -anemone by the selection of such a situation; and, moreover, it becomes -an interesting question as to whether the advantage is a mutual one. -Close observations may, and already have, thrown some light on this -matter, though it is probable that there still remains something to be -learnt concerning the relations which exist between the inside and -outside occupants of the portable house. - -It may be noticed that the anemone almost invariably takes up a position -on the same portion of the shell, and that, when fully expanded, its -mouth is usually turned towards that of the crab. This seems to be a -very favourable position for the anemone, since it is one that will -enable it to catch the waste morsels from the crab's jaws by its -expanded tentacles. But it is, perhaps, not so easy to suggest a means -by which the anemone can make an adequate return for free board thus -obtained. It is well to remember, however, that crabs are regarded as -such delicate morsels by fishes that we have already spoken of the value -of these crustaceans as bait; while the fact that sea anemones remain -perfectly unmolested in rock pools inhabited by most voracious fishes, -coupled with the fisherman's experience as to the absolute worthlessness -of anemones as bait, is sufficient in itself to justify the conclusion -that these creatures are very distasteful to fishes. This being the -case, it is possible that the hermit crab is amply repaid by the anemone -for its liberal board not only by partially hiding the crab from the -view of its enemies, and thereby rendering it less conspicuous, but also -by associating its own distasteful substance with that which would -otherwise be eagerly devoured. - -When the hermit grows too large to live comfortably in its shell, a -change of home becomes necessary, and it is interesting to observe that -the anemone living on the outside of the shell transfers itself at the -same time; and this is a matter of vital importance to the crab, since -it usually changes its lodging at the moulting period, at which time its -body is covered by a soft skin, and is then even more acceptable as prey -to the fishes. Thus the anemone accompanies its host, affording it -continued protection during the period of its greatest danger. - -Before leaving the coelenterates we must refer to one other form which, -though not often having its habitat between the tide-marks, is -nevertheless a very common object in the neighbourhood of fishing -villages, where the refuse from the nets used in deep water has been -thrown on the beach. We refer to the peculiar animal known to fishermen -as 'Dead Men's Fingers,' and to the naturalist as the _Alcyonium_. - -When seen out of water it is not by any means an inviting object, but is -apparently a mass of gristly matter, of a dirty yellowish or brownish -colour, sometimes flattened and shapeless, and sometimes lobed in such a -manner as to suggest the popular name so commonly applied. It is always -attached to some hard object, such as a stone or a shell, and is so -frequently associated with oyster shells that it is by no means an -uncommon object in the fishmonger's shop, from which we have often -obtained live specimens for the aquarium. - -When placed in sea water it gradually imbibes the fluid surrounding it, -becoming much swollen. Then little star-like openings appear, the -circumference of each of which protrudes so as to form a little -projecting tube. Finally, a crown of eight little tentacles is -protruded, and the mass, so uninteresting at first sight, reveals itself -as a colony of pretty polyps. - -In general structure the Alcyonium resembles the sea anemone, but the -firm body-wall of the colony is supported and protected to some extent -by the presence of minute spicules of carbonate of lime; and it is -interesting to note that while the tentacles of anemones and corals make -up a number that is a multiple of either five or six, those of the -Alcyonaria and the allied 'Sea pens' are always in multiples of four. - - - - - CHAPTER X - - _STARFISHES, SEA URCHINS, ETC._ - - -Still passing up the scale of animal life, we now come to the -_Echinodermata_--the other sub-kingdom which we have already referred to -as forming, with the Coelenterates, the old division of Radiata. The -term _Echinoderm_ signifies 'hedgehog skin,' and is applied to the group -on account of the fact that the majority of its species possess a skin -that is either distinctly spiny, or exhibits numerous more or less -defined prominences. This skin is also supported and hardened by the -deposit of little plates or spicules of carbonate of lime, all joined -together so as to form a kind of scaffolding or 'test' for the -protection of the animal; and this secretion of carbonate of lime is not -always confined to the outer skin, for, in some cases, it occurs in the -walls of the internal organs as well. - -Most of the animals of this sub-kingdom display a regular radiate -symmetry; that is, the parts of their bodies are arranged regularly -round a common axis, and the arrangement is usually a five-fold one, as -may be observed in the case of the common Five-fingered Starfish of our -coasts (see Plate IV.), and it is worthy of note that this radiate -disposition of parts is not merely external, but that, as in the case of -anemones and jelly-fishes, it also obtains within, and determines the -arrangement of the internal organs. Further, although this radiate -symmetry characterises the adult animals of the group we are -considering, yet some show a tendency towards bilateral symmetry (parts -arranged equally on two opposite sides of a common axis), while this is -the rule, rather than the exception, with the early stages or _larvæ_ of -these creatures. Observe, for instance, the larva of the common Brittle -Starfish, the adult of which species exhibits an almost perfect radiate -symmetry, and we see something more than a mere trace of a two-sided -disposition. - -We have not to look far into the structure of any typical echinoderm to -see that it is a distinct advance on the anemones in the matter of -organisation. To begin with its digestive system--this consists of a -tube having no communication with the general body-cavity, but remaining -quite distinct throughout its length, with both ends communicating -directly with the exterior. Its nervous system also is more highly -developed, for it has a well-formed ring of nerve matter round the -mouth, from which pass two or three systems of nerve fibres, each system -having its own special function to perform. The sense organs, however, -do not appear to be well developed, though there exist certain 'pigment -spots,' in which nerve fibres terminate, and which are supposed to serve -the purpose of eyes. - - [Illustration: FIG. 104.--LARVA OF THE BRITTLE STARFISH] - -One of the most interesting features in connection with the echinoderms -is undoubtedly the structure and function of the apparatus for -locomotion. Examine a live sea urchin, or the common five-rayed -starfish, in a rock pool or aquarium, and it will be seen to possess a -large number of soft, flexible, and protrusible processes, each of which -terminates in a little sucking-disc that enables the animal to obtain a -good 'foot-hold;' and, having fixed itself on one side by means of a -number of these little 'feet,' it is enabled, by the contraction of -certain muscles, to pull itself along. - -The little feet we are examining are really tubes filled with water, and -capable of being inflated by the injection of water into them from -within the body of the animal. Each one communicates with a water tube, -several of which (usually five) radiate from a circular canal of water -that surrounds the mouth. This circular canal does not communicate with -the mouth, but with a tube, known as the 'stone canal' because of the -carbonate of lime deposited within its walls, that opens at the surface -of the body on the opposite side, and is guarded at the orifice by one -or more perforated plates through which water gains admission. Thus the -animal can fill its 'water system' direct from the sea, and, by the -contraction of muscles that surround the main canals, force this water -into the little 'tube-feet,' causing them to protrude and present their -sucking-discs to any solid object over which it desires to creep. We may -observe, however, that some of the little protrusible tubes have no -sucking-discs, and probably serve the purpose of feelers only; also, -that while these tube-feet are the principal means of locomotion in -certain species, in others the movements of the body are performed -almost exclusively by the five or more rays that extend from the centre -of the animal, and which are readily curved into any desired position by -the action of well-developed muscles. - -All the echinoderms come within the domain of the marine naturalist, for -no members of the sub-kingdom are inhabitants of fresh water; and it is -interesting to observe that, unlike the animals previously described, -none of them live in colonies. - -A general examination of the various starfishes to be found in our seas -will show that they may be divided into three distinct groups. One of -these contains the pretty Feather Stars, which are distinguished by -their long and slender 'arms,' usually ten or more in number, each of -which bears a number of pinnules that give it quite a feathered -appearance. The second includes the Brittle Stars, possessing five -slender arms that are jointed to the small, flattened, central disc, and -which are so named on account of the readiness with which the animal -falls to pieces when alarmed or disturbed; and the third is formed by -the remaining five-rayed stars, the arms of which, instead of being -jointed to, are continuous with, the centre of the body. - -All these starfishes have a leathery skin, supported and hardened by a -framework of calcareous plates, and presenting a number of hard ridges -or spines. In addition to the system of water tubes already mentioned as -characteristic of the echinoderms, they also possess a second circular -vessel round the mouth, from which a number of vessels are distributed -to the walls of the digestive tube. These, however, are bloodvessels, -and are directly concerned with the nutrition of the body. Some, also, -have imperfectly developed eyes at the ends of the arms or rays. - -Contrary to what one would expect after watching the somewhat sluggish -movements of starfishes, they are really very voracious creatures, -attacking and devouring molluscs and small crustaceans, sometimes even -protruding their stomachs to surround their prey when too large to be -passed completely through the mouth; and they are also valuable as -scavengers, since they greedily devour dead fishes and other -decomposible animal matter. - - [Illustration: FIG. 105.--LARVA OF THE FEATHER STAR] - -Feather Stars differ from other starfishes in that they are stalked or -rooted during one portion of their early life. At first they are little -free-swimming creatures, feeding on foraminifers and other minute -organisms that float about in the sea. Then they settle down and become -rooted to the bottom, usually in deep water, at which stage they are -like little stalked flowers, and closely resemble the fossil encrinites -or stone lilies so common in some of our rock beds, and to which they -are, indeed, very closely allied. After a period of this sedentary -existence, during which they have to subsist on whatever food happens to -come within their reach, they become free again, lose their stalks, and -creep about by means of their arms to hunt for their prey. - - [Illustration: FIG. 106.--THE ROSY FEATHER STAR] - -The commonest British species of these starfishes is the Rosy Feather -Star (_Antedon rosaceus_); and as this creature may be kept alive in an -aquarium for some considerable time without much difficulty, it will -repay one to secure a specimen for the observation of its habits. It is -not often, however, that the Feather Star is to be found above low-water -mark, its home being the rugged bottom under a considerable depth of -water, where a number usually live in company; but there is no -difficulty in obtaining this and many other species of interesting -starfishes in fishing towns and villages where trawlers are stationed, -for they are being continually found among the contents of the net. - -Although the Feather Star can hardly be described as an active creature, -yet it will cover a considerable amount of ground in the course of a -day, creeping over rocks and weeds by means of its arms, which are -raised, extended, and again depressed in succession, each one thus in -turn serving the purpose of a foot. These arms are capable of being -moved freely in any direction, as are also the little more or less rigid -pinnules appended to them. The latter are bent backwards on an extended -arm that is being used to pull the animal along, so that they form so -many grappling hooks that hold on the bottom; and then the arm in -question is bent into a curve by the contraction of its muscles, thus -dragging the body forward. The arms on the opposite side of the body are -also used to assist the movement by pushing it in the same direction, -and this is accomplished by first bending the arms, and then, after -curving the pinnules in a direction from the body, again extending them. -Other movements of the feather star are equally interesting. Thus, the -manner in which it will suddenly extend its arms and apply its pinnules -to the surface on which it rests in order to obtain a good hold when -alarmed, and the way in which it apparently resents interference when -one of the arms is touched, are worthy of observation. The arms -themselves are readily broken, and will continue to move for some time -after being severed from the body, but the loss to the animal is only -temporary, for a new arm grows in the place of each one that has been -broken off. - -This tendency to break into pieces is much greater in the Brittle Stars, -as might be expected from their popular name; and is, in fact, such a -marked characteristic of the group that it is not by any means an easy -matter to obtain a collection of perfect specimens. They will often snap -off all their arms, as if by their own power of will, when disturbed or -alarmed, and even when removed from their hold without injury, they will -frequently break themselves into pieces if dropped into spirit or in any -way subjected to a sudden change of conditions. - -The tube-feet of Brittle Stars are very small and are not provided with -suckers, but are very sensitive, serving the purpose of feelers; also, -having thin, permeable walls, they probably play a large part in the -process of respiration. Both arms and disc are hardened by a dense -scaffolding of calcareous plates; and not only are the former attached -to the latter by a well-formed joint, but the arms themselves are -constructed of a number of segments that are held together by a kind of -'tongue and groove' joint. Round the mouth are a number of tentacles -that are kept in constant motion with the object of carrying the food -towards it, and of holding the larger morsels while the act of -swallowing is progressing. - - [Illustration: FIG. 107.--THE COMMON BRITTLE STAR] - -The various species of Brittle Stars live among the rocks and weeds, -chiefly in deep water, where they move about by means of the muscular -contraction of their arms, the disc being raised on the curved arms as -the animal proceeds. Some species are to be found between the -tide-marks, and especially abundant on the south-west coast are two -small species that live among the tufts of coralline weeds, sometimes so -crowded together that dozens may be taken from a little patch of -coralline only two or three inches square. These have such small discs, -and such slender arms, and are, moreover, so well concealed by their -colouring, which closely resembles that of the weed-tuft they inhabit, -that they are only to be detected by close inspection. - -The remaining division of the starfishes, sometimes distinguished by the -name of Common Stars, possess five arms or rays, which may be either -long or short, and which are not jointed with the central disc, but -continuous with it; that is, there is no sharp line of demarcation -between arm and disc. One or two species are well known to all -frequenters of the sea-side, but the majority of them inhabit deep -water, where they creep about over the rocks and weeds, obtaining their -food from the bed below them. - -If we examine the common five-finger star that is so often stranded on -the beach, and so frequently found in rock pools between the tide-marks, -we see that each arm has a large and conspicuous groove running along -its centre on the under side, and on each side of these are the rows of -tube-feet, arranged in such a manner that they have suggested the -appearance of an avenue of trees on each side of a garden walk, and have -consequently earned the name of _ambulacrum_. These tube-feet may be -protruded for some distance; and, being provided with suckers that -possess considerable clinging power, they form the principal means of -locomotion. - -Put the starfish in the aquarium, or in a tidepool by the sea, and you -will find it very interesting to observe how the animal progresses, -while some idea of the clinging power of the tube-feet may be -ascertained by allowing the animal to creep over the submerged hand. - -The movements of the tube-feet may also be seen to advantage when the -starfish is laid upside down in a pool, and, what is still more -interesting, the manner in which the animal turns itself over. To do -this it will first bend the tips of one or two of its arms so as to -bring the suckers against the ground; and then, aided by the pulling -action of these, it will gradually bring other suckers into a similar -position till, at last, the whole body has been turned over. Some of our -common starfishes have rays so short that they may be termed angles -rather than arms, and these are unable to turn their inverted bodies by -the gradual method just described. They generally raise their bodies on -the tips of three or four of the rays, assuming somewhat the form of a -three-or four-legged stool, and then, bending the remaining one or two -arms over the body, they alter the position of the centre of gravity -till eventually the body topples over to the desired position. - -Some of the common five-rayed stars have no suckers on their tube-feet, -and consequently have to creep by means of the muscular contractions of -their arms; and several of them are like the brittle stars in breaking -up their bodies when irritated or seized. This latter peculiarity will -account for the frequency with which we come across animals with one or -more rays smaller than the others, the smaller rays being new ones that -have been produced in the place of those lost. Again, we sometimes meet -with such monstrosities as a five-rayed star with six or more rays, some -smaller than others, the smaller ones representing two or more that have -grown in the place of one that has been lost; or a starfish with -branched or forked arm, illustrating the tendency to produce a new arm -even when the original one has been only partially severed. - -A close observation of a starfish in water may enable us to detect a -number of little transparent processes standing out between the -prominences of the rough skin of the upper surface. These are little -bags filled with fluid, formed of such thin walls that gases can readily -pass through them, and are undoubtedly connected with the process of -respiration. Also, on the upturned extremity of each arm a red spot may -be seen; and this from the nature of its structure, and from its -association with the nervous system, has been regarded as a rudimentary -eye. - -On the upper side of the disc one may also observe a more or less -conspicuous spot of variable colour, on one side of the centre. It is a -plate, finely perforated, covering the outer extremity of a short canal -which communicates with the system of water tubes that were described in -the earlier part of this chapter. It is, in fact, the entrance through -which water is admitted into the central ring round the mouth, and from -this into the radial water tubes that run through each arm of the -starfish to supply the tube-feet. The short tube referred to is always -filled with sand, and thus the water that enters into the water-vascular -system is filtered before it reaches the circular vessel. It is -interesting to note, in this connection, that here is one respect in -which the radiate symmetry of the starfish is broken, there being only -one entrance, and that not a central one, by which water is distributed -into the five rays. - -Of course, when the ray of a starfish has been broken off the water -vessel or vessels that it contained are destroyed, as is also the -prolongation of the stomach, in the form of a long, blind tube, that -extended into it. But no inconvenience attaches itself to this loss, for -the starfish has the power of reproducing even its lost viscera, as well -as any of the five rays of the body that may be broken off. - -We must briefly refer to one other feature of the common star, viz. the -possession of small prehensile organs around the mouth. These are little -spines, the extremities of which are movable, and take the form of -little pincers by means of which the animal can hold its prey. - -When it is desired to preserve starfishes for future study, immersion in -diluted spirit or a solution of formaldehyde will answer all purposes, -the soft parts being thus preserved as well as the harder structures; -but it is usual to preserve them in a dry state when they are required -merely for purposes of identification, as is usually the case with the -specimens in an ordinary museum collection. In the latter case it is -advisable to put the starfishes in strong spirit for a few days, -changing the spirit if several specimens are put together, and then -drying them as quickly as possible in the open air. - - [Illustration: FIG. 108.--SECTION OF THE SPINE OF A SEA URCHIN] - -We have now to consider the Sea Urchins or Sea Eggs, which are readily -known by the hedgehog-like covering of hard spines. Externally they -appear as globular or heart-shaped bodies, the surface entirely hidden -by spines except, perhaps, the mouth on the under side, which is -provided with an apparatus for mastication. If alive, and in the water, -one may notice that the animal creeps along the bottom, mouth downwards, -moving itself either by means of its moveable spines, or by soft -tube-feet resembling those of starfishes, that are protruded between the -spines, or by both combined; and the movements of its masticating organ -may be seen by observing the animal through the side or bottom of a -glass vessel of sea water. The last-named organ is surrounded by an area -of soft skin, and is not present in all species. - -A closer examination of the common globular urchin will show that it is -wonderfully constructed. Even the spines, which are in themselves -uninteresting objects to the naked eye, are most beautifully formed, a -transverse section revealing a radiate or reticulated structure when -viewed through the microscope. Each spine has a concave base which fits -on a little tubercle of the calcareous shell or test that covers the -body of the animal, forming a perfect ball-and-socket joint, and is -capable of being moved in any direction by means of small muscular -bands. - - [Illustration: FIG. 109.--SEA URCHIN WITH SPINES REMOVED ON ONE SIDE] - -On removing the spines the shell is seen to completely enclose the -animal with the exception of the mouth, with its masticatory apparatus, -and the small area around it which is covered by the uncalcified skin -just referred to. - -At the very top of the shell, exactly opposite the mouth, there is a -small plate perforated by the extremity of the digestive tube. Round -this are five angular plates, each perforated by the ducts of the -ovaries or egg-producing glands, but one of these is enlarged and -further perforated, that it may serve the second purpose of allowing -water to enter the system of water tubes that supply the tube-feet, and -thus corresponds exactly with the plate already noticed on the upper -surface of the starfish. Between these are five smaller plates, each -with a rudimentary eye that receives a fine nerve-thread. - - [Illustration: FIG. 110.--APEX OF SHELL OF SEA URCHIN] - -The remaining and greater portion of the shell of the urchin is composed -of ten radiating segments, each of which is made up of two rows of flat -angular plates united at their edges. Five of these segments, arranged -alternately with the others, are perforated by numerous holes, through -which the tube-feet of the urchin are protruded, while the remainder -are imperforate; and all ten plates bear the little hemispherical -processes to which the spines are jointed. - - [Illustration: FIG. 111.--SHELL OF SEA URCHIN WITH TEETH PROTRUDING] - -One of the most interesting features of this urchin is undoubtedly its -complex and wonderful masticating system. There are five teeth, -symmetrically arranged, and all pointing towards the centre of the -mouth. Each is attached to a wedge-shape jaw, made up of several -pieces, and the whole apparatus is attached by ligaments to loops in the -interior of the shell, and is moved by no less than thirty distinct -muscles. The complete system may be readily dissected out, and is well -worthy of study and preservation. (The harder portions of the system may -often be found in the interior of the empty shell of an urchin after the -softer structures of the body have decayed away.) - - [Illustration: FIG. 112.--INTERIOR OF SHELL OR SEA URCHIN] - - [Illustration: FIG. 113.--MASTICATORY APPARATUS OF SEA URCHIN] - -An interesting dissection of the globular urchin may also be made by -cutting completely round the shell with a pair of sharp-pointed -scissors midway between the mouth and the apex, and then separating the -upper and lower halves, as shown in fig. 114. In this way the whole of -the digestive tube, with its numerous curves, may be traced from the -mouth to the anus at the opposite pole. The water-vessels that supply -the tube-feet in the regions of the five perforated plates may also be -seen, as well as the ovaries or egg-producing organs and the bases of -the five jaws with their complicated system of muscles. - -A little acquaintance with the commonest of the British sea urchins will -show that they may be divided into two well-defined groups, one -containing the globular or subglobular forms, of which the common sea -urchin or sea egg (_Echinus sphæra_) above described, is a type, as well -as the pretty little Green Pea Urchin (_Echinocyamus pusillus_), and the -little Purple-tipped Urchin (_Echinus miliaris_), which is found -principally on the west coast of Scotland; while the second group is -formed by the less symmetrical Heart Urchins, which differ from the -others in several interesting particulars of structure and habit. - - [Illustration: FIG. 114.--SEA URCHIN DISSECTED, SHOWING THE DIGESTIVE - TUBE] - -These heart urchins (Plate IV., fig. 4) are covered with short, delicate -spines which are not much used for purposes of locomotion, the animals -moving from place to place almost entirely by means of their tube-feet, -while the globular urchins travel principally by their spines, which are -stouter and more freely moved on well-formed ball-and-socket joints. -Also, while in the globular species the perforated plates that admit of -the protrusion of the feet are arranged with a perfect radiate symmetry, -those of the heart urchins are confined to one side of the shell; and -the digestive tube, which in the former terminates in the pole opposite -the mouth, in the latter ends close to the mouth itself. Further, the -heart urchins do not possess any kind of dental apparatus. - - [Illustration: PLATE IV - - ECHINODERMS - - 1. Asterias rubens - 2. Goniaster equestris - 3. Ophiothrix fragilis - 4. Echinocardium cordatum - 5. Echinus miliaris - 6. Echinus esculentus] - -The habits of sea urchins are interesting, and may be watched in the -aquarium, where the movements of the spines and of the tube-feet may -be seen perfectly. Some species are very inactive, living in holes and -crevices, or under stones, and seldom move from their hiding-places, -while others travel considerable distances. The former have generally no -eyes, and, instead of seeking their food, simply depend for their -subsistence on the material carried to them by the movements of the -water; while the latter possess visual organs similar to those observed -in certain starfishes. Some species also protect themselves from their -enemies when in the open by covering their bodies with sand, small -stones, shells, or weeds, and thus so perfectly imitate their -surroundings that they are not easily detected. The feet that are used -for purposes of locomotion terminate in suckers resembling those of the -common five-fingered starfish, and have considerable clinging power, but -some have either very imperfectly developed suckers or none at all, and -are probably used as feelers only. - -Sea urchins, like their allies the starfishes, generally inhabit deep -water beyond low-water mark, where they often exist in enormous numbers, -feeding on both animal and vegetable substances; but some species are -often to be met with between the tide-marks, where they may be seen -under stones, and frequently half hidden in mud. The globular species -occur principally on rocky coasts, but the heart urchins are more -commonly dredged from banks of sand or mud that are always submerged. - -The life-history of urchins closely resembles that of starfishes, for -the young are free-swimming creatures of an easel-like form, and during -this early larval existence their bodies are supported by a calcareous -skeleton. - -We will conclude our short account of the British echinoderms with a -description of the peculiar Sea Cucumbers, which belong to the division -_Holothuroidea_. These creatures are so unlike starfishes and urchins in -general appearance that the uninitiated would hardly regard them as -close relatives. The body is, as the popular name implies, -cucumber-shaped, with the mouth at one end, and the general aspect is -wormlike. There is, however, a radiate symmetry--a five-fold arrangement -of parts, though not so regular as in most echinoderms. Running -lengthwise along the body are five rows of tube-feet, but only two of -these are well developed and terminate in functional suckers; and, as -might be expected, the animal crawls with these two rows beneath it. The -feet are outgrowths of a system of water tubes similar to that of the -urchin, there being a circular tube round the mouth, from which branch -five radial tubes, one for each row. - -The mouth of the sea cucumber is surrounded by plumed tentacles which -can be retracted at will, and which are used in capturing the smaller -living things that form its food. Like the earthworm, it will often -swallow large quantities of sand, from which it digests the organic -matter contained. - -The body-wall of the _Holothuroidea_ is strong and muscular, and is -strengthened by the presence of numerous spicules of carbonate of lime, -often in the form of little anchors, wheels, and crosses, while the -outer surface is rough and slimy, and often of a colour so closely -resembling the surroundings of these animals that they are not easily -observed. This feature is one of great value to the creatures, since -they have no means of defence from their enemies, and seem to owe their -safety entirely to their protective colouring. - - [Illustration: FIG. 115.--THE SEA CUCUMBER] - -There are several species of sea cucumbers on our coasts, but all -inhabit deep water and are seldom to be seen above low-water level. They -are, as a rule, easily obtained from fishermen, who will bring them in -when requested to do so. Live specimens may be kept for a considerable -time in the indoor aquarium, and seem to prefer a rocky bottom on which -they can hide under stones at times, and a bed of sand on which they -will occasionally crawl. They will readily devour small molluscs and -crustaceans, and will partake of dead organic matter in a partially -decomposed state. - -The following tabular summary of the classification of Echinoderms may -possibly be of use for reference:-- - - SUB-KINGDOM _ECHINODERMATA_ - +-------------------------------------------+-------------+-------------+ - |Body star-shaped. |Body glob- |Body | - +------------+------------------------------+ ular, sub- | elongated, | - |Body |Body not stalked. | globular, | and covered | - | stalked, |Tube-feet used for locomotion.| or heart- | with a | - | at least |=Class:= _Stelleridæ._ | shaped, | soft skin | - | during +--------------+---------------+ and cov- | containing | - | early |Arms jointed |Arms contin- | ered with | calcareous | - | stage. | to disc, and | uous | a con- | spicules. | - | Feet not | not contain- | with disc, | tinuous | | - | used for | ing prolong- | and contain- | shell. |=Class:= | - | loco- | -tions of the| ing processes | | _Holothu- | - | motion. | internal | of the |=Class:= | roidea_ | - | | organs | viscera. | _Echinoidea_| (Sea | - |=Class:= | | | (Sea Ur- | Cucumbers).| - | _Crinoidea_|=Order:= |=Order:= | chins). | | - | (Feather | _Ophiuroidea_| _Asteroidea_ | | | - | Star). | (Brittle | (Common | | | - | | Stars). | Stars). | | | - +------------+--------------+---------------+-------------+-------------+ - - - - - CHAPTER XI - - _MARINE WORMS_ - - -Some groups of animals are so well defined that the individual species -contained in them can be assigned their proper place without any -difficulty, the main characteristics by which the group is distinguished -running with more or less precision throughout the series; but, -unfortunately this is not the case with the 'worms,' which constitute -the sub-kingdom _Vermes_. Here we have a most heterogeneous assemblage -of animals, collectively exhibiting exceedingly wide variations in both -form and structure. - -We have already referred to the sea cucumber as wormlike in form, and -this creature is only one of a large number of wormlike animals that are -not worms; and it is also a fact that a considerable number of the worms -are not wormlike. It appears as if the sub-kingdom Vermes were a kind of -receptacle into which we may throw almost any invertebrate animal that -does not readily fall in line with the general characteristics of the -other important groups; for in it we have such a varied assemblage of -creatures that, speaking of them collectively as worms, it becomes most -difficult, if not absolutely impossible, to say exactly what a worm is; -and it is a question whether the sub-kingdom ought not to be divided -into at least two or three groups of the same standing. - -This being the case we can hardly give a satisfactory summary of the -characteristics of the group, and therefore it must be understood that -in our attempt to do so we unavoidably exclude some forms that belong to -it according to our present system of classification. This being -remembered, we will define worms as soft-bodied and elongated animals, -exhibiting a bilateral symmetry (that is, having appendages and organs -arranged symmetrically on each side of a plane extending from the dorsal -to the ventral surface through the centre of the body), and with the -body usually divided into a succession of segments, each of which -resembles the one preceding and following it. Though many of the worms -are generally looked upon as uninteresting creatures, of such an -unattractive appearance and with such depraved habits that they are -beneath respect, yet a study of the sub-kingdom will prove that not only -does it include a number of wonderful forms with the most marvellous -life histories, but that some of them are very beautiful objects; and -this last remark refers more particularly to many of the marine worms, -which come directly within the scope of our work. - -Before passing on to the special study and classification of the marine -species, however, we must say a few words concerning the worms in -general, reminding the reader that all our statements regarding the -anatomy of the creatures may be readily verified by simple dissections -of one or two typical species, such as the common earthworm, the -fisherman's lugworm, the sea mouse, or the common horse-leech of our -fresh-water ponds. With this object in view, the animal may be killed by -immersion in spirit, then pinned out in the dissecting tray under water, -and the body-wall opened by means of a pair of sharp-pointed scissors. - -The digestive tube of a worm runs completely through the length of the -body, and though there is no distinct head, there is always a mouth, and -this is often provided with horny jaws, and sometimes also with horny -teeth, with which the animal is enabled to inflict wounds on its prey. - -Like the preceding sub-kingdom--the _Echinodermata_--worms possess a -system of water tubes; this system, however, is not in any way connected -with the function of locomotion, but is, in many cases at least, if not -in all, intimately associated with the process of respiration. It -consists of a series of tubes, arranged in pairs in the successive -segments, communicating with the body-cavity internally, and opening at -the exterior by means of pores in the cuticle. In some there is a highly -organised system of bloodvessels, containing blood that is usually -either colourless, red, or green, but the colour of the blood is never -due to the presence of corpuscles, as is the case with higher animals, -the tint being due to the plasma or fluid portion of the blood; and -though worms cannot be said to possess a true heart, yet they often have -one or more contractile bloodvessels which serve the purpose of -propelling the blood. - -Most worms possess a nervous system, and, where this is present, it -consists of a chain of ganglia, placed along the ventral side of the -body, beneath the digestive tube, all united by means of a nerve cord, -and distributing nerves in pairs to various parts of the body; and it -may be well to note here one very important point of distinction between -the general arrangement of the central portion of the nervous system in -the worms and higher invertebrates, as compared with that of the -corresponding structure in the vertebrates:--In the former the main axis -of the system, consisting, as we have seen, of a chain of ganglia -connected by a nerve cord, is invariably placed along the _ventral_ -portion of the body-cavity--the surface on which the animal crawls; -while in the vertebrates the axis of the nervous system lies along the -upper or dorsal part of the body; and, instead of lying in the general -body-cavity, in company with the organs of digestion and circulation, is -enclosed in the bony canal formed by the vertebral column. It will be -seen from this that when it is desired to examine the nervous system of -the invertebrate animal, the body-wall should be opened along the middle -of the ventral surface, while, in the vertebrate, the central axis -should be exposed from above. - -Many of the vermes are parasitic, either attaching themselves to the -exterior of other animals, and deriving nourishment by sucking their -blood, or they are internal parasites, living in the digestive canal of -their hosts and partaking of the digested food with which they are -almost perpetually surrounded, or burrowing into the tissues and -imbibing the nutritive fluids which they contain; and it is interesting -to study even these degraded members of the group, if only to observe -how their physical organisation degenerates in accordance with their -depraved mode of living. In them we find no digestive system with the -exception of the simplest sac from which the fluids they swallow may be -absorbed, for their food is taken in a condition ready for direct -assimilation; and the food so obtained being readily absorbed into all -parts of their soft bodies, and being sufficiently charged with oxygen -gas by the respiration of their hosts, they require no special organs -for circulation or respiration, nor, indeed, do we find any. Further, we -find that the nervous system is often undeveloped; for since the -parasites, and especially the internal ones, are so plentifully -surrounded with all the necessaries of existence, their bodies are so -simple in construction that no complex nervous system is required to -promote or control either locomotion or internal functions. Even the -general body-cavity often disappears in these degraded creatures, the -internal organisation being of such a low type that there is no -necessity for it; and all the abundant nourishment absorbed over and -above that required for the sustenance of their simple bodies is -utilised in the reproduction of the species; consequently we find, as a -rule, the reproductive organs well represented, and the species -concerned very prolific. - -It is an interesting fact, too, that these parasites, in their earliest -stage, possess organs which are present in the higher worms, but which -degenerate as they approach the adult form, thus indicating that they -have descended from more respectable members of the animal world, and -that the low physical development which they ultimately attain is the -natural result of their base mode of living. - -The young marine naturalist, working on our coasts, will not be brought -into intimate contact with parasitic worms to any large extent, yet we -have said this little on parasitism to show that these degenerate -creatures are not really devoid of interest, and that they will repay -study whenever they are found. They will be more frequently met with -during the examination of the animals--usually higher types--that become -their hosts, and thus they hardly come within the scope of this work. - - [Illustration: FIG. 116.--A TURBELLARIAN, MAGNIFIED - _a_, mouth; _b_, cavity of mouth; _c_, gullet; _d_, stomach; _e_, - branches of stomach; _f_, nerve ganglion; _g_ to _m_, reproductive - organs.] - -The simplest of the worms are those forming the class _Turbellaria_, so -designated on account of the commotion they produce in the water -surrounding them by means of the vibratile cilia that fringe their -bodies--a characteristic that is also expressed by their popular name of -Whirl Worms. They are usually small creatures, with soft, flattened, -unsegmented bodies, though some of the larger species are really -wormlike in form, and are more or less distinctly divided into a chain -of segments. Many of them are marine, and may be seen gliding over -stones left uncovered by the receding tide with a smooth slug-like -motion, and when disturbed in a rock pool, occasionally swimming with a -similar smooth motion by the aid of their cilia. They avoid bright -light, and are consequently generally found on the under surfaces of -stones, especially in rather muddy situations, and where the stones are -covered with a slimy deposit of low forms of life. In these -turbellarians the mouth is situated on the under surface, thus enabling -the animal to obtain its nourishment from the slimy surface over which -it moves, and it is also provided with an extensile proboscis that aids -it in the collection of its food. The digestive tube is generally very -complex in form, extending its branches into every part of the soft -body; and, there being no special organs of respiration, the animal -derives all the oxygen required by direct absorption from the water -through the soft integument. - -When searching for turbellarians on the sea shore one must be prepared -to meet with interesting examples of protective colouring that will -render a close examination of rocks and stones absolutely necessary. -Some of these worms are of a dull greyish or brownish colour, so closely -resembling that of the surface over which they glide that they are not -easily distinguished; and the thin bodies of others are so transparent -that the colour of the stone beneath is visible through them, thus -preventing them from being clearly observed. - -Overturned stones should be examined for their flattened bodies gliding -along rapidly in close contact with the surface. They may be removed -without injury by placing a wet frond of a sea weed close to the stone, -in front of one end of the body, and then urging them to glide on to it -by gently touching the opposite end. Sometimes, however, the -turbellarians remain perfectly still when exposed to the light, in which -case they are even more difficult to detect, but a little practice will -soon enable one to distinguish them with readiness. - -Allied to the turbellarians are the Spoon Worms or Squirt Worms, some -species of which inhabit deep water round our shores, where they burrow -into the sand or mud of the bed of the sea. These form the class -_Gephyrea_, and consist of creatures with sac-like or cylindrical and -elongated bodies, and a protrusible proboscis, which is often of great -length. Their bodies are not distinctly segmented, nor do they bear any -appendages. The skin is tough and horny, and the body-wall, which is -very thick and muscular, is often contracted when the animal is -disturbed, thus causing a jet of water to be forcibly ejected. - -All the most interesting of the marine worms belong to the _Annelida_ or -_Chætopoda_, popularly known as the Bristle-footed worms, because their -locomotion is aided more or less by the presence of stiff bristles that -project beyond the surface of the skin. These are all highly organised -worms, mostly with very elongated bodies that are distinctly segmented -exteriorly by a number of transverse grooves, while the interior is -correspondingly divided into a number of compartments by means of a -series of _septa_. - -In addition to the bristles already mentioned, there are often numerous -appendages, but these must be distinguished from the more perfect -appendages of the arthropods, to be hereafter described; for while the -latter are distinctly jointed to the body, and are themselves made up of -parts that are jointed together, the former are mere outgrowths of the -body-wall. The digestive and circulatory systems are well developed, as -is also the system of water tubes that connect the body-cavity with the -exterior, while the body-cavity itself is full of fluid. - -This group of worms is subdivided into two divisions, the many bristled -(_Polychæta_) and the sparsely bristled (_Oligochæta_) worms. The latter -contain the common earthworms and some less known species, while the -former include a number of interesting and even beautiful worms, all of -which are marine, and many of them among the commonest objects of the -sea shore. - -These Polychætes exhibit a great variety of habit as well as of -appearance. Some live in crevices of the rocks or under stones and -weeds, or make burrows in the sand or mud of the bed of the sea, and -roam about freely at times in search of food. They are continually -coming within the ken of the sea-side collector, being revealed by -almost every overturned stone near the low-water mark, and are often -seen crawling over the wet rocks just left uncovered by the receding -tide; while their burrows are often so numerous that hundreds may be -counted in every few square feet. But many are sedentary species, and -these are not so generally known to young sea-side naturalists, who -frequently observe, and even preserve, the interesting homes they -construct, while less attention is given to the architects that build -them. - -It is very interesting to observe some of the general differences -between the roving and the sedentary species--differences which -illustrate the principle of adaptation of structure to habit. The roving -species are provided with a lobe that overhangs the mouth, bearing -feelers and eyes, and are thus enabled to seek out any desired path and -to search for their food. They are provided with bristles and other -appendages by means of which they can travel freely over the surfaces of -solid objects, and are able to swim well either by undulations of the -body, or by fringed appendages, or both. The carnivorous species, too, -are provided with strong, horny jaws, and sharp, curved teeth, by means -of which they can capture and hold their prey. The sedentary species, on -the other hand, unable to move about in search of food, are supplied -with a number of appendages by means of which they can set up water -currents towards their mouths, and which also serve the purpose of -special breathing organs, and, having no means of pursuing and devouring -animals of any size, they do not possess the horny jaws and curved teeth -so common in the rovers. Their eyes, too, are less perfectly developed, -and the tactile proboscis of their free-moving relatives is absent. - - [Illustration: FIG. 117.--_Arenicola piscatorum_] - -Of the roving worms, perhaps, the Lugworm or Sandworm (_Arenicola -piscatorum_) is the best known. Its burrows may be seen on almost every -low sandy or muddy shore, and, being so highly valued as a bait, its -general appearance is well known to all professional and amateur sea -fishers. It reaches a length of eight inches or more, and varies in -colour according to the sand or mud in which it lives. The segments of -this worm are very different in structure in different parts of the -body. Those in the front of the body have a few tufts of bristles -arranged in pairs, while the middle portion of the body has large -brush-like tufts of filamentous gills placed rather close together; and -the hindmost part has no bristles or appendages of any kind, and is so -well filled with the sand or mud that it is quite hard and firm to the -touch. As is the case with our common earthworms, the sand or mud is -swallowed in enormous quantities, and this is not only the means by -which the lugworm derives its food, but also assists it considerably in -making its burrows; the extent to which this creature carries on its -work of excavation may be estimated by the thousands of little -contorted, worm-like heaps of sand that lie on the surface at every -period of low water. These little heaps are known as 'castings,' and -consist of the sand that passed through the worm's body as the burrowing -proceeded. - -The Ragworm is another species that is highly valued as bait. It burrows -into the odorous mud that is so commonly deposited in harbours and the -mouths of sluggish rivers. In this species the segments are similar -throughout the length of the body, and the numerous flattened appendages -give it the ragged appearance that has suggested its popular name. Quite -a number of marine worms closely allied to the common ragworm, and -resembling it in general form, are to be found on our shores. Many of -these may be seen by turning over stones that are left exposed at low -tide, while others hide themselves in snug little crevices of the rock, -or in the empty shells of the acorn barnacle and various molluscs; and -some species, including one of a bright-green colour, creep freely over -the wet rocks in search of food or home, often exposing themselves to -the rays of a fierce summer sun. - - [Illustration: FIG. 118.--THE SEA MOUSE] - -The Sea Mouse (_Aphrodita aculeata_) is certainly one of the most -interesting of the roving marine worms, and, though seldom seen above -low-water line, may often be obtained by the sea-side collector with the -aid of friendly fishermen, who sometimes find it plentifully among the -contents of their trawl nets. Failing such aid, it may be looked for -among the encrusted stones that are exposed only at the lowest spring -tides, especially in places where a certain amount of mud has been -deposited under the shelter of outlying rocks; and the chances of -success are much greater if the search is made immediately after a -storm, for at such times much of the life that exists in deep water will -have been driven shoreward by the force of the waves. - -At first sight the sea mouse would hardly be associated with the worms; -for, instead of having the elongated and cylindrical form that is -usually regarded as characteristic of these creatures, it is broad and -slug-like in shape, the under surface, on which it crawls, being flat, -while the upper side is convex. The segmentation of the body, too, is -not readily seen in the upper surface on account of the thick felt-like -covering of hairs, but is at once apparent when the creature has been -turned over to expose the ventral side. - -When seen for the first time in its natural haunt one naturally wonders -what the moving mass may be. Crawling sluggishly over incrusted stones, -or remaining perfectly still in a muddy puddle that has been exposed by -overturning a stone, it looks like a little mound of mud itself, about -four or five inches long, and its general colour and surface so closely -resembles that of its surroundings that an inexperienced collector may -never even suspect that the mass is a living animal form. But take the -creature and wash it in the nearest rock pool, and it will be recognised -as a broad segmental worm, thickly covered with fine hairs above, and -its sides adorned by bristles that display a most beautiful iridescence. -It is not easy to see the value of this gorgeous colouring to the -animal, and it is doubtful whether, on account of the muddy nature of -the creature's home, such colouring is often displayed to the view of -other inhabitants of the sea; but it is well known, on the other hand, -that sea mice are readily devoured by fishes, even though they possess -an armature of stiff and sharp spines, and that they must therefore be -often preserved from destruction by the close resemblance of the general -colour to that of their surroundings. - -The gills of the sea mouse are not prominent appendages, as with most -marine worms, but are soft fleshy structures situated beneath the -overlapping scales that lie hidden below the thick hair of the upper -surface. - -As it is most probable that the reader may desire to preserve a sea -mouse at some time or other, a few words concerning the best methods of -doing this may be of value. If it is to be preserved in fluid, it should -be thoroughly washed to remove all the mud that normally covers its -body, and then placed in spirit or formaldehyde, both of which fluids -have no destructive effects on the iridescent colouring of the bristles. -If, however, it is desired to keep the specimen in a dry state, it -should first be put into strong spirit containing a few grains of -corrosive sublimate, for a few days. It should then be put under -considerable pressure between several thicknesses of absorbent paper to -expel the fluid it contains, as well as all the softer internal -structures. By this means it will have been squeezed quite flat, so that -it presents anything but a natural appearance; but the skin may be blown -out to the normal shape by means of a glass tube inserted into the -mouth, and then set aside to dry. As the water it originally contained -has been extracted by the strong spirit, the drying takes place very -quickly; and the small amount of corrosive sublimate that has penetrated -into its substance will be sufficient to protect it from the invasion of -those pests that commonly attack our museum specimens. - -Passing now to the sedentary or fixed worms, we meet with some that are -very interesting and beautiful creatures, even when considered apart -from the wonderful homes they construct. The several species of the -genus _Terebella_ form a soft and flexible tube by binding together -particles of sand, shells, or mud with a sticky substance that exudes -from their own bodies. These tubes are to be found in abundance between -the tide-marks on almost every low, sandy shore, the nature of the tubes -varying, of course, with the character of the materials at the disposal -of the builder. - -In some cases the tubes are exposed throughout the greater part of their -length, but very frequently they are more or less buried in the sand or -other material of the beach, so that one has to dig to a moderate depth -in order to extricate them. In either case, however, the tube of -Terebella may be known by the free tufts of sandy threads that form a -deep fringe around its mouth. - -These worms almost invariably select a sheltered situation for their -abode, and should be searched for at the foot of rocks, or under stones, -and it is no easy matter to move the buried tube with its occupant -intact. - -When turning over the stones of a sandy or muddy beach one frequently -discovers the slender, thread-like tentacles of the Terebella, together -with the sandy filaments that surround the mouth of the tube, the -remainder of the tube and its occupant being beneath the surface, and -the ground is often so hard and stony that a strong tool is necessary -to dig it out; but the work entailed will be amply repaid if a perfect -specimen be obtained and placed for observation in the aquarium. - - [Illustration: FIG. 119.--TUBE-BUILDING WORMS: _Terebella_ (LEFT), - _Serpula_ (MIDDLE), _Sabella_ (RIGHT)] - -The reader may possibly be acquainted with the tubes or cases that are -constructed by the larvæ of caddis flies in fresh-water ponds and -streams, and perhaps has noticed the ease with which these creatures may -be made to construct new homes after having been turned out of doors. -Similar experiments may be performed with Terebella; for when the worm -has been extricated from its tube without injury--a work that requires -great care on account of the soft and slender nature of the creature's -body--and placed in the aquarium with a bed of suitable material, it -will build itself a new dwelling. As with the caddis larvæ, the -different species may be known by the materials they select to construct -their tubes, but in captivity they may be compelled to employ other than -their favourite substance for this purpose. It is unfortunate, however, -that Terebella is a nocturnal builder, and thus its movements are not so -easily observed. - -When removed from its tube its first movements suggest a resentment at -the untimely ejection. This being over, it seeks a sheltered situation -beneath the edge of a stone, and, at nightfall, commences the slow -process of the construction of a fresh home. The particles of material -at hand are seized by the tentacles, placed in position round the body, -where they are held together by the sticky secretion already mentioned. - - [Illustration: FIG. 120.--_Terebella_ REMOVED FROM ITS TUBE] - -The tentacles are employed in two distinct ways:--They may be flattened -into slender ribbon-like structures, which, by being folded -longitudinally at any point, may be made to grasp a particle of sand; -and, in addition to this, the tip of the tentacle may be converted into -a minute cup-shaped sucker by the withdrawal of the fluid it contains -into the body. - -Some species of Terebella build their tubes of ordinary sand, while -others select fragments of shells. Some employ mud only, and -occasionally we meet with tubes constructed of the silky secretion of -the body with hardly any foreign matter. - -We sometimes see edges of rocks, on low, sandy shores, covered with what -appears to be large masses of consolidated sand, full of holes a little -more than an eighth of an inch in diameter; and these masses are often -so extensive and so firm that they seem to form the greater part of the -rock itself. Such masses are particularly abundant on the south coasts -of Devon and Cornwall, but are more or less plentiful on most sandy -shores of Great Britain. They consist of the tubes of a species of the -marine worm _Sabella_, which have been built up much in the same manner -as those of Terebella, but usually exist in such numbers in the same -spot that, together with the sand that has been washed between them, -they form the dense masses just described. - -A cluster of some dozens of these tubes may be detached with the aid of -a hammer and chisel; or, in some instances, where the mass of tubes is -not held so firmly together, by the mere pressure of the hand; and it -will then be observed that each tube consists of a flexible membrane, of -a somewhat leathery nature, formed by a sticky secretion from the body -of the worm, with its outer surface covered with grains of sand. The -tubes may be easily opened, and the occupants extracted for examination, -when it will be observed that the front or upper portion of the worm is -short and thick, while the hindmost portion is much thinner, and is -doubled forwards in the tube. The body is also provided with numerous -bristles, by means of which the worm is enabled to grasp the membranous -lining of the tube, and thus secure a firm hold within its home. - -A cluster of these tubes should be placed in a rock pool, or in the -marine aquarium, when the worms may be seen to protrude gradually, and -expose a large number of feathered tentacles, which, by their incessant -motion, keep up the constant circulation of the water for the purpose of -respiration as well as to bring food particles towards the mouths of the -worms. - -It is possible to keep these worms alive for some time in the aquarium, -but special care is required for the reason that it is a very difficult -matter to secure a cluster of tubes without injury to a certain number -which are sure to be broken or otherwise damaged; and these, dying and -decomposing within their homes, speedily pollute the water. Hence it is -necessary to keep a sharp watch for dead specimens, which should, of -course, be removed at once. The presence of a putrefying worm may often -be detected by the appearance of a whitish fungoid growth round the -mouth of what appears to be an empty tube; and if, through neglect, the -water of the aquarium has been allowed to become contaminated by the -products of decomposition, it will often happen that some of the living -worms will come entirely out from their tubes, as if to seek a more -sanitary situation. Thus, the exit of worms from their homes may always -be looked upon as pointing to a suspicious condition of the water which, -if not corrected immediately, may lead to the death of all. - -The species we have briefly described is by far the commonest of the -genus Sabella, but there are several others to be found on our shores. -Some are of a solitary nature, and construct a sandy tube so much like -that of a certain species of Terebella that they may be mistaken for -that genus. Another solitary species builds a hard stony tube of -carbonate of lime that has been extracted from the sea water; and -although it is hardly possible to take the live worm from this -calcareous tube without injury, the animal may be obtained intact for -examination or preservation by dissolving away the tube in dilute -hydrochloric acid. - - [Illustration: FIG. 121.--A TUBE OF _Serpula_ ATTACHED TO A SHELL] - -While engaged in collecting specimens on the sea shore we are -continually meeting with stones and shells that are more or less covered -with white, limy tubes twisted into all manner of serpentine forms. -These are the tubes of other marine worms known as the _Serpulæ_, which, -like the species previously mentioned, are interesting objects for the -aquarium. - -The tubes themselves are worthy of study and preservation, more -especially as they vary in form, and may, to some extent, provide a -means by which the different species may be identified. They are -composed of fine layers of calcareous matter secreted by the body of the -worm within, and lined by a thin leathery membrane which may be easily -exposed by dissolving away the mineral matter as just described. Some -are triangular in section, and often distinctly keeled, while others are -cylindrical, and flattened more or less on the lower side. The -triangular tubes are attached to stones or shells throughout their -length, but the cylindrical ones are often elevated above the surface in -the wider and newer part. - -If a cluster of these tubes, freshly gathered from between the -tide-marks, be placed in the aquarium, the worms will soon protrude the -foremost portion of their bodies, exposing beautiful fan-like gills, -often brilliantly coloured in shades of scarlet, blue, or purple, which -are kept in motion in such a manner as to convey water, and consequently -also food, towards the mouth. The gills are of course, richly supplied -with blood, for their main function is to aërate that liquid by exposing -it to the water in order to absorb oxygen gas. The body of the worm is -provided also with little cilia, which, by their constant vibratory -motion, keep up a circulation of water through the tube; and this not -only keeps the tubular home free from excrement and other sedimentary -matter, but also probably assists in the function of respiration by -bringing fresh supplies of water in contact with the animal's soft and -absorbent skin. - - [Illustration: FIG. 122.--_Serpula_ REMOVED FROM ITS TUBE] - -When the worms are disturbed they immediately withdraw themselves within -the tubes, this being done by the aid of the numerous minute hooklets on -the surface of the body that enable the worms to cling firmly to the -membranous linings of their homes; and it will then be observed that the -mouth of each tube is closed by a lid (_operculum_), which hangs as by a -hinge when not in use. These operculi vary much in character, and supply -another aid in the identification of the various species. They differ -much in shape, and may be either membranous, horny, or calcareous. - -Little calcareous tubes, somewhat similar to those of the _Serpulæ_, but -always in the form of a spiral, may often be seen on stones and shells, -and the fronds of sea weeds, sometimes so closely packed together as to -almost entirely cover the surface. The average diameter of these spirals -is only about a sixteenth of an inch, and many are so small that a lens -is necessary to discern their shape. In general form they closely -resemble some of the small species of _Planorbis_ shells that are so -common in our ponds and streams, but these latter are the shells of -freely moving _molluscs_, and are generally of a brownish colour. - - [Illustration: FIG. 123.--THE SEA MAT (_Flustra_)] - -The minute worms that live within the tubes in question belong to the -genus _Spirorbis_, and are very similar to those of the _Serpulæ_, and -their pretty plumed gills may be seen with a lens when a cluster of the -tubes is placed in a shallow vessel of sea water. A sharp tap on the -table on which the vessel rests will cause the little creatures to -suddenly retire into their homes, the entrances to which may then be -seen to be closed by an operculum. - -There is an interesting group of animals known collectively as the -_Bryozoa_ or _Polyzoa_, or, popularly, as the Moss Polyps, that are -often classed with the worms, though they are not, according to the -general idea, wormlike in appearance. They live in pretty colonies, many -of which are certainly familiar objects to all who ramble along the sea -shore. Some form pretty lacelike patches on the fronds of sea weeds, -while others are built up into flat, frond-like, branching objects that -are often mistaken for sea weeds by young collectors. Among the latter -is the Sea Mat (_Flustra_), that is so commonly washed up on the shore -in great abundance. An examination with a lens will show that, in both -instances, the mass consists of very many minute cells, with horny or -calcareous walls, the mouth of each cell being close by an operculum. - -On placing the colony in sea water, however, we find that each little -cell is the home of a small animal, that protrudes from the cell, -exposing a mouth that is surrounded by a crown of tentacles. A -moderately high magnifying power will also show that the tentacles are -covered with minute vibratile cilia, by means of which currents of water -are set in motion towards the mouth to supply the animal with food. -Some, too, have a lip by means of which the mouth may be closed. - - [Illustration: FIG. 124.--_Flustra_ IN ITS CELL, MAGNIFIED] - -In addition to the colonies just briefly described, there are other moss -polyps that build up little, branching, tree-like clusters which closely -resemble some of the sea firs, and many of these are to be found in the -sheltered crevices of rocks, or attached to the under sides of stones -between the tide-marks. - -While searching the surfaces of rocks and weeds at low tide, one's -fingers will be constantly coming in contact with fixed, soft-bodied -animals that suddenly eject a fine stream of water as they are touched. -These are the Sea Squirts, sometimes spoken of as the Tunicate Worms. -They are semi-transparent creatures of oval or elongated form, and -usually of a pale yellow, brown, or pink colour; and derive their -popular name from the fact that they are covered externally by a -continuous tunic or wall of tough structure. - -Although the tunicates resemble worms in many points of structure, it is -interesting to note that in their young or larval state the body -consists of two cavities, one of which contains the internal organs, -while in the other the central portion of the nervous system is -developed, in which respects they resemble the vertebrate or back-boned -animals--fishes, amphibians, reptiles, birds, and mammals. At this -stage, too, the creatures possess a tail that is supported by a rod of -gristle similar to that which gives place to the backbone in the -developing vertebrate. These features, though only transitory, are -regarded as a mark of relationship to the higher forms of animal life, -and thus the tunicates have been separated from the sub-kingdom Vermes -by some zoologists, and given an exalted place at the top of the -invertebrate scale, where they form a sub-kingdom of their own, and are -looked upon as a link connecting the invertebrates with the vertebrates. - - [Illustration: FIG. 125.--SEA SQUIRT] - -Before passing on to the next sub-kingdom, we should observe that the -interesting Rotifers or Wheel Animals also belong to the Vermes; but -although many of these minute creatures are to be found in sea water, -their principal home is the stagnant water of fresh-water ponds and -ditches, and thus we may be excused for neglecting them here. - - - - - CHAPTER XII - - _MARINE MOLLUSCS_ - - -The sub-kingdom _Mollusca_ includes a great variety of soft-bodied -animals which differ from the members of the last division in the fact -that they are never segmented, and in the possession of a thick outer -covering, of a leathery nature, which completely envelops the body, and -which usually secretes a calcareous shell of one or more parts. A -general idea of the extent of the group may be formed when we state that -it contains the Octopus and the Cuttlefish; all Snails and Slugs, and -animals of a similar nature; and all those numerous 'bivalves' which are -represented by the well-known Oysters, Mussels, Scallops, &c. - -By far the greater number of the molluscs are aquatic in habit; and of -these such a large proportion are marine that the group provides plenty -of occupation for the sea-side naturalist. This being the case, we shall -devote the present chapter to a description of the general -characteristics of these animals, and to the principles of their -classification, illustrating our remarks by a few selections from all -the chief divisions. - -Although, as we have already hinted, the body of a mollusc generally -bears but little resemblance to that of the typical elongated and -segmented worm, yet the study of the earliest stages of the former shows -that a certain relationship exists between the two sub-kingdoms, the -newly hatched mollusc being often a minute free-swimming creature with -expanded lobes fringed with cilia, and bearing a resemblance to certain -of the Rotifers, Moss Polyps, and other animals that are included among -the _Vermes_. But in the adult molluscs this resemblance is lost, these -creatures being generally easily distinguished from all others by -certain well-marked external features, as well as by internal characters -that are peculiar to them and fairly constant throughout the group. - -The external shell, where it exists, is usually composed of one or of -two parts, and therefore we speak of univalve and bivalve molluscs; and -no internal skeleton of any kind is to be found except in the division -containing the Cuttlefishes, the 'bone' of which is one of the common -objects washed up on our shores by the breakers. - -In all the molluscs there is a well-formed digestive tube, and often a -complex arrangement of small teeth which sever the food by a rasp-like -action. There is also a well-formed heart, consisting of two or more -cavities, by means of which the blood is forced through the body; but, -as a rule, blood vessels are either few or absent, the blood being -driven through spaces between the tissues that serve the same purpose. - - [Illustration: FIG. 126.--LARVÆ OF MOLLUSCS - _v_, ciliated 'velum'; _f_, rudimental foot] - -The nervous system consists of a few masses of nerve substance -(_ganglia_), connected by nerve cords, and sending off fibres to various -parts of the body, the principal ganglion being one situated close to -the mouth, and often surrounding the first portion of the digestive -tube. - -The animals of this sub-kingdom are grouped into three principal and -well-marked divisions--the _Lamellibranchs_, or Plate-gilled molluscs, -the gills of which are composed of plate-like layers, and the headless -bodies enclosed in a bivalve shell; the _Cephalophora_, or head-bearing -molluscs, protected by a univalve shell; and the _Cephalopoda_, or -Head-footed molluscs, so called because the mouth is surrounded by -tentacles or arms by which the animal can cling to objects or seize its -prey. - -We shall deal with these three divisions in the above order, taking -first the bivalves, the shells of which are found in great variety along -our shores. - -The general nature of a lamellibranch is easily made out by the -examination of one of the common species that may be obtained alive on -any part of the coast, such as the Edible Mussel, the Cockle, or the -Oyster, and the reader will do well to secure a few specimens and -examine them with the aid of the following description of the principal -distinguishing features. - -The shell is formed of two valves, united by a hinge which is sometimes -of the simplest possible description, but which often exhibits a -beautiful arrangement of interlocking teeth. A _ligament_ of flexible -and elastic substance often holds the two valves together. - - [Illustration: FIG. 127.--SHELL OF THE PRICKLY COCKLE (_Cardium - aculeatum_) SHOWING UMBO AND HINGE; ALSO THE INTERIOR SHOWING THE - TEETH] - -The reader has probably observed that the valves of a dead lamellibranch -usually gape. This is due either to the pull exerted by a ligament that -is attached to the valves outside the hinge, or to the pressure of an -internal cartilage which unites the valves within, and which is -compressed when the shell is closed. When the animal is alive, it has -the power of closing its shell by the contraction of the adductor -muscles, to be presently described, and when the valves are brought -together by this means the external ligament is more or less stretched, -or the cartilage within, which is also an elastic material, is -compressed. - -Examining the shell from the exterior we observe that each valve has a -nucleus (the _umbo_) close to the hinge, round which are usually a -number of more or less distinct concentric lines, extending to the lower -or ventral margin. This nucleus represents the whole shell of the young -mollusc, and the lines are the lines of growth, each one marking the -extreme limit of the valve at a particular period of the animal's -existence. Further it will be observed that the lines of growth are -often wider apart in some directions than in others, thus denoting the -unequal rate of growth that determined the form of the adult shell. - - [Illustration: FIG. 128.--INTERIOR OF BIVALVE SHELL, SHOWING MUSCULAR - SCARS AND PALLIAL LINE] - -The shell of a bivalve is often made up of two very distinct layers, the -outer one called the prismatic layer because, when examined -microscopically, it is seen to consist of minute vertical prisms of -calcareous matter; and the inner one presenting a beautiful pearly -iridescence, due to the fact that it is made up of a number of extremely -thin and finely waved layers of calcareous substance that have the power -of decomposing light. This latter layer is secreted by the whole surface -of the mantle that lies in contact with it, while the outer, prismatic -portion of the shell is formed only by the free edge of the mantle; and -we often find a distinct line (the _pallial line_), some little distance -from the ventral margin that marks the junction of the muscle of the -mantle with the shell. The shape of this line is a very important -feature of the shell, since it is of great value in the determination of -relationships. - -Further, the inner surface of each valve is marked by the impressions or -scars of other muscles, the number and position of which vary -considerably in different species. They include the _adductor_ muscle or -muscles (one or two in number) that pull the valve together; the muscle -or muscles that withdraw the foot, called the _retractor pedis_, and the -_protractor pedis_ that pulls the foot out. Not only are these scars -often very distinct in themselves, but we may frequently observe lines -running tangentially from their circumferences towards the umbo, to -which they all converge. These lines enclose the areas previously -occupied by the muscular impressions; in other words, they show the -directions in which the muscles named above shifted their positions as -the animal grew. - - [Illustration: FIG. 129.--DIAGRAM OF THE ANATOMY OF A LAMELLIBRANCH - _f_, mouth, with labial palps; _g_, stomach; _i_, intestine, - surrounded by the liver; _a_, anus; _r_, posterior adductor muscle; - _e_, anterior adductor muscle; _c_, heart; _d_, nerve ganglion; - _m_, mantle (the right lobe has been removed); _s_, siphons; _h_, - gills; _ft_, foot] - -Now let us obtain a few species of live lamellibranchs, put them in a -vessel of sea water, and observe them after they have been left -undisturbed for a time. The shell will be seen to gape slightly, -exposing the edges of the two lobes of the mantle which lie closely on -the inner surface of the valves, thus completely enveloping the body of -the animal; and at one end, usually the narrower end in the case of -irregular shells, we shall observe two openings--the _siphons_, -sometimes enclosed within a tube formed by a prolongation of the united -mantle lobes, and protruding from between the valves, and sometimes -formed by the mere contact of the mantle lobes at two adjacent points. -If now we introduce a little carmine or other colouring matter by means -of a glass tube, setting it free near the lower siphon--the one more -remote from the umbo of the shell, we observe that it enters the body of -the mollusc through this opening, and reappears shortly afterwards -through the upper or dorsal siphon. Thus we see that water currents are -incessantly circulating in the body of the animal, entering by the -_inhalent_ or _ventral siphon_, and leaving by the _exhalent_ or _dorsal -siphon_. These currents are maintained by the vibratile action of -thousands of minute cilia belonging to cells that line the cavities of -the body, and serve to supply the animal with both air and food; for -lamellibranchs, being gill-breathers, derive the oxygen necessary for -respiration from the air held in solution by the water, and their food -consists entirely of the minute living creatures that always abound in -natural waters. - -Again, we shall find that some of our live bivalves have protruded a -thick, conical, fleshy mass--the _foot_, from the opposite end of the -body. This organ is the means of locomotion in the case of the burrowing -and other free-moving bivalves, but is developed to a less extent in -those species that lead a sedentary life. Thus, the common Edible Mussel -secretes a tuft of strong silky fibres (_byssus_) by means of which it -fixes itself to a rock or other body, and therefore does not need the -assistance of a muscular foot; and an examination of its body will show -that the foot is very small in proportion to the size of the animal, as -compared with that of the wandering and burrowing species. The same is -true of the oyster, which lies fixed on its side, the lower valve being -attached to the surface on which it rests. - - [Illustration: FIG. 130.--_Mytilus edulis_, WITH BYSSUS] - -We have made use of the terms _dorsal_ and _ventral_ in speaking of the -shell of a bivalve, and it is important that these and a few other -similar terms be well understood by those who are about to read the -descriptions of the animals, or who may desire to describe them -themselves. To do this, take a bivalve in your hand, and hold it before -you in such a position that the hinge is uppermost, and the siphons -turned towards you. The foot of the animal is now pointing in the -direction you are looking, and the mouth, situated at the base of the -foot, is also directed the same way. You have now placed the shell, and, -of course, also the animal, in such a position that its _dorsal_ side is -uppermost, the _ventral_ side below, the _anterior_ end turned from you, -the _posterior_ (often narrower) end towards you, the _right valve_ on -your right, and the _left valve_ on your left. Knowing the exact uses of -these few terms you are in a better position to understand the -descriptions of bivalves, and to locate the exact situations of the -various internal organs named in such descriptions. - -A great deal of the internal anatomy of a bivalve mollusc may be made -out by easy dissections, and although the structure of the different -species varies in several details, the general characteristics of the -group are practically the same in all and may be gathered by the -examination of a few specimens. - - [Illustration: FIG. 131.--A BIVALVE SHELL (_Tapes virgineana_) - _a_, anterior; _p_, posterior; _l_, left valve; _r_, right valve; - _u_, umbo, on dorsal side] - -For this purpose the shell should be prised open by means of some -flattened but blunt implement, such as the handle of a scalpel, and -then, after inserting a piece of cork to keep the valves apart, gently -remove the mantle lobe from the valve which is held uppermost with the -same implement, being careful to separate it from the shell without -doing any damage to the soft structures. Separating the mantle from the -shell in this way we meet with one or more hard masses of muscle that -are joined very firmly to the latter. These are the adductor muscles -that pass directly from valve to valve, and on cutting them through -close to the uppermost valve, the latter can be raised so as to expose -the body of the animal, mostly hidden by the overlying mantle lobe. - -Before raising the upper mantle lobe we observe the heart, on the dorsal -margin of the body, near the hinge of the shell, situated in a -transparent cavity (the _pericardium_) containing a colourless fluid. It -consists of at least two cavities--a thick-walled ventricle and a -thin-walled auricle, and its slow pulsations may be watched with or -without the use of a hand lens. On opening the pericardium the heart is -still better seen, and if we carefully cut into the thick-walled -ventricle we find a tube running completely through its cavity. This is -the _rectum_--the last part of the digestive tube, that commences at the -mouth, and terminates in a cavity at the posterior end communicating -with the exhalent siphon. - -After noting the nature and position of the one or two adductor muscles -previously cut through, we turn the upper mantle lobe upwards, laying -it back over the hinge of the shell, cutting it through at the bases of -the siphons if we find it is united with the opposite lobe at those -points; or, if not united, we observe two points at which the lobes -touch each other in order to form the siphonal openings. - -Several organs are now exposed to view. The lower mantle lobe is seen in -close contact with the valve below it, and if we touch its edge we shall -probably observe that it is retracted slightly by the contraction of its -own muscular fibres. The tip of the foot is also seen projecting towards -the anterior end, its base being hidden between the two sets of -plate-like gills that extend along the length of the body. On touching -the tip of the foot we find it retract by the contraction of the -muscular fibres of which it is composed, aided, perhaps, by the action -of one or more _retractor pedis muscles_ with which it is supplied. On -raising the upper gill-plates we may observe the dark colour of the -digestive gland (liver) at the base of the foot, and also see two or -more _tentacles_ or _labial palpi_ on the anterior side of the same. - -Between the labial palpi is the mouth, which leads into the stomach by a -short, wide tube, and then into a convoluted tube which finally passes -through the heart, and terminates near the exhalent siphon as above -described. The whole length of this tube may be followed by careful -dissection, its direction being determined at short intervals by probing -it with a bristle that has been tipped with a little melted sealing wax. -It will be seen to wind through the base of the foot, surrounded through -the greater part of its course by the digestive gland, from which a -digestive fluid enters it through small ducts. - -The diagram on p. 194 shows the general internal anatomy of a -lamellibranch, parts of which have been removed to reveal the underlying -structures. The animal lies in its left valve, the right valve, the -right mantle lobe, and the right set of gill-plates having been -completely dissected away. The whole course of the digestive tube has -also been exposed, and the positions of the three nerve ganglia, with -their connecting nerve cords, constituting the central portion of the -nervous system, are also indicated. - -It will be interesting, finally, to learn the direction taken by the -water currents which supply the animal with air and food in their course -through the system. Passing in through the inhalent siphon, the water -immediately enters a large cavity between the mantle lobes. This cavity -(the _branchial cavity_) contains gills, as we have already seen, and -also extends to the mouth. The water, urged on by the motion of myriads -of minute ciliated cells in the walls of the cavity, passes in part -through the digestive tube, and in part around, between, and through the -gill plates, which are perforated by numerous holes. After thus -completely bathing the gills, and supplying the oxygen necessary for -respiration, this latter current passes into a second cavity above the -gills, and thence into the exhalent siphon, where it mingles with the -fluid from the digestive tube as well as with other excretory matter. - -Lamellibranchs are, as a rule, exceedingly prolific, a single individual -of some species discharging more than a million ova in one season. The -larvæ swim freely in the water, and are provided with eyes that enable -them to search for their food, but the eyes always disappear when the -young settle down to a more sedentary life. It is true that adult -bivalves sometimes possess visual organs, often in the form of -conspicuous coloured spots on the edge of the mantle, these, however, -are not the same that existed during the larval stage, but are of a more -recent development. - -Lamellibranchs are classified in various ways by different authorities, -the arrangement being based principally on the number and position of -the adductor muscles, or on the nature of the gills. For our present -purpose we shall look upon them as consisting of two main divisions--the -_Asiphonida_ and the _Siphonida_, the former including those species -which do not possess true tubular siphons, the inhalent and exhalent -openings being formed merely by the touching of the mantle lobes; and -the latter those in which the mantle lobes are more or less united and -tubular siphons formed. Each of these divisions contains a number of -families, most of which have representatives that inhabit the sea; and -we shall now note the principal characteristics by which the more -important families are distinguished, and take a few examples of each, -starting with the _Siphonida_. - -Examining the rocks that are left exposed at low tide we frequently find -them drilled with holes that run vertically from the surface, seldom -communicating with each other within, and varying in diameter from less -than a quarter of an inch to half an inch or more. Some of these holes -are the empty burrows of a boring mollusc, while others still contain -the living animal _in situ_. - -The molluscs in question belong to the family _Pholadidæ_, which -contains a number of species that exhibit very remarkable features both -as regards structure and habit. The shell is very thin and fragile, but -yet composed of hard material, and its surface is relieved by a series -of prominent concentric ridges that bear a number of little rasp-like -teeth. It gapes at both ends, has neither true hinge nor ligament, and -is often strengthened externally by two or more extra or accessory -valves. The _hinge-plate_ is a very peculiar structure, for it is -reflected over the exterior of the umbones, above which they are -supported by about ten thin shelly plates, the whole thus forming a -series of chambers. The accessory valves are supported by these bridged -structures, and a long, straight, calcareous plate also fills the space -along the dorsal side of the shell in some species. The muscular scars -and the pallial line are distinctly seen on the inner surface, and a -peculiar curved shelly plate projects from under the umbo of each valve. - - [Illustration: FIG. 132.--_Pholas dactylus_ - 1, ventral aspect, with animal; 2, dorsal side of shell showing - accessory valves] - -The animal inhabiting the shell is somewhat wormlike in general form, -and the mantle lobes are united in front--that is at the lower end of -the shell as it lies in the burrow--except that an opening is left for -the protrusion of the short foot. The siphons are united and much -elongated, so that they protrude beyond the mouth of the burrow when the -animal is active; the gills are narrow, and extend into the exhalent -siphon; and the anterior adductor muscle, being very near the umbones, -serves the double purpose of adductor and ligament. - -Such are the general distinguishing features of this family, all the -species of which burrow into stone or other material. Those more -commonly met with on our coasts belong principally to the genus -_Pholas_, and are popularly known as Piddocks. - -It was long a puzzle as to how the fragile piddocks could excavate the -tubular burrows in which they live, and, since their shells are so thin -that it seemed almost impossible for hard stones to be ground away by -them, it was suggested that the rocks were excavated by the action of an -acid secretion. This, however, would not account for the formation of -holes in sandstone and other materials which are insoluble in acids; -and, as a matter of fact, no such acid secretion has ever been -discovered. The boring is undoubtedly done by the mechanical action of -the rasp-like shell, which is rotated backwards and forwards, somewhat -after the manner of a brad-awl, though very slowly, by the muscular -action of the foot of the animal. - -Piddocks are found principally in chalk and limestones, though, as -before hinted, they are to be seen in sandstones and other rocks, the -material in any case being, of course, softer than the shell that bores -it. The largest holes and the largest specimens are to be found in chalk -and other soft rocks; while the piddocks that burrow into harder -material are unable to excavate to the same extent and are, as a -consequence, more stunted in their growth. The burrowing is continued as -long as the animal grows, the hole being always kept at such a depth -that the shell is completely enclosed; and not only this, for when the -rock is soft, and the surface is worn down by the sea, the piddock has -to keep pace with this action, as well as to allow for its increase in -size. - -As a result of the rasping action of the pholas shell on the surrounding -rock the space hollowed out becomes more or less clogged with débris. -This is ejected at intervals by the sudden contraction of the foot of -the animal, which brings the shell quite to the bottom of the burrow, -thus causing the water with its sediment to shoot upwards, - -It is not usually an easy matter to obtain perfect specimens of the -pholas by simply pulling them from their burrows, the shells being so -thin and fragile, and the mouth of the burrow being often narrower than -the widest part of the shell. The best plan is to chip away the rock -with the aid of a mallet and chisel, or to break it into pieces with a -hammer, thus laying open the burrows so that the molluscs fall from -their places. - -The Common Piddock (_Pholas dactylus_) may be identified by the -illustrations, and the other members of the family may be recognised at -once by the similarity in structure and habit. The principal species are -the Little Piddock (_P. parva_), the shell of which is wider in -proportion to the length, with only one accessory valve; and the White -Piddock (_P. candida_), also with a single accessory. In all the above -the foot is remarkable for its ice-like transparency. - - [Illustration: FIG. 133.--_Pholas dactylus_, INTERIOR OF VALVE; AND - _Pholadidea_ WITH ANIMAL] - -There is another genus--the _Pholadidea_--the species of which are very -similar to _pholas_ both in structure and habit. The shells are, -however, more globular in form, and are marked by a transverse furrow. -The gape at the anterior (lower) end is also very wide, and covered over -with a hardened plate in the adult. Also, at the posterior (upper) end -of the shell is a horny cup through which the siphons protrude, and the -latter, which are combined throughout their length, terminate in a disc -that is surrounded by a fringe of little radiating appendages. - -In the same family are the molluscs popularly known as ship worms, which -are so destructive to the woodwork of piers and jetties, or which burrow -into masses of floating timber. Some of these, belonging to the genus -_Xylophaga_--a word that signifies 'wood eaters'--have globular shells -with a wide gape in front, and burrow into floating wood, nearly always -in a direction across the grain. The burrows are about an inch deep, and -are lined with a calcareous deposit. The siphons, combined except at the -ends, are slender and retractile; and the foot, which is thick, is -capable of considerable extension. - - [Illustration: FIG. 134.--THE SHIP WORM] - - [Illustration: FIG. 135.--1. _Teredo navalis._ 2. _Teredo norvegica_] - -Other ship worms belong to the genus _Teredo_, and are very similar in -general characters. The shell is small and globular, with a wide gape at -both ends, and consists of two three-lobed valves with concentric -furrows. It is so small in proportion to the size of the animal that it -encloses but a small portion of the body, and lies at the bottom of the -burrow, which is of considerable length--often from one to two feet. The -animal is very wormlike in form; and although the shell is so small, yet -all the internal organs are enclosed by it. The mantle lobes are united -in front, except where the sucker-like foot passes through them; the -gills are long and narrow, and extend into the siphonal tube; and the -two very long siphons are united almost throughout their length. It is -also interesting to note that in these animals the rectum does not pass -through the heart, as it does in nearly all molluscs, and that a pair of -horny or calcareous 'styles' or 'pallets' project from the place where -the two siphonal tubes begin to diverge. - -Several species of _Teredo_ are to be met with on our coasts, but they -are so similar in general structure that the above brief description -applies almost equally well to all. - -Other boring molluscs frequent the British shores, but they belong to -quite a distinct family called the _Gastrochænidæ_ because their shells -gape widely on the ventral side. Their valves are equal in size and very -thin, the hinge has no teeth and the pallial line is sinuated. The -margins of the mantle lobes are thickened and united except where a -small aperture is left for the protrusion of the finger-like foot. The -siphons are very long and retractile, and the gills extend into the -inhalent tube. These animals burrow into mud, shells, or stone, often -dwelling together in such numbers that their galleries cross one another -and form a most intricate network, and the different species are to be -found from low-water mark to a depth of a hundred fathoms or more. - - [Illustration: FIG. 136.--_Gastrochæna modiolina_ - 1, Animal in shell; 2, shell; 3, cell] - -The British species belong to two genera--the typical genus -_Gastrochæna_, and the _Saxicava_ or stone-borers. - -The former contains the Common Flask shell (_G. modiolina_) which -burrows into limestone and shells, in the latter case passing generally -through the shells into the ground below, and completing its home by -cementing together any fragments of hard material that come in its way -into a flask-shaped cell. The opening of the burrow is shaped like an -hour-glass, the two expansions serving for the protrusion of the -siphonal tubes, and the neck of the flask-shaped abode is usually -lined with a calcareous layer that projects slightly to afford further -protection to the extended siphons. Although this species is very common -on some parts of our coast, it is seldom obtained without the aid of a -dredge, for it usually lives at a depth of from five to ten fathoms; and -when found it is generally no easy matter to extricate them from their -holes, to the sides of which they often cement their shells. - -The genus _Saxicava_ contains a few species that drill holes, often -several inches deep, in shells and stone, and frequently do great damage -to breakwaters and other artificial structures. The foot is usually -provided with a byssus by which the animal fixes itself to a little -projection on the side of its burrow. The species are to be found from -low-water mark to a depth of one hundred fathoms or more. - -The next family, named _Anatinidæ_, contains a number of molluscs that -burrow in mud or sand or live in seclusion in the crevices of rocks. -Their shells are thin, with a granulated outer surface, and the valves -are united by a thin external ligament. The inner surface is pearly, the -pallial line usually sinuated, and both valves are pitted for the -reception of the somewhat stout internal cartilage. The mantle lobes are -united, as are also the siphons to a greater or lesser extent; and there -is only one gill on each side. - - [Illustration: FIG. 137.--1. _Thracia phaseolina._ 2. _Thracia - pubescens_, SHOWING PALLIAL LINE] - -Some of the common species of this family are popularly known as Lantern -shells, and perhaps the most familiar of these is _Thracia phaseolina_, -the specific name of which is given on account of a fancied resemblance -of the shell to a bean. The shell is very fragile, and although large -numbers may often be seen stranded on sandy beaches, but few of them are -perfect specimens. - -The family _Myacidæ_ may be recognised by the thick, strong, opaque -shells, usually gaping at the posterior end; the wrinkled epidermis -which covers the whole or part of the shell; and the united siphons, -which are more or less retractile. The mantle cavity is also closed with -the exception of a small hole left for the protrusion of the small foot. -The pallial line of the shell is sinuated. - - [Illustration: FIG. 138.--1. _Mya truncata._ 2. INTERIOR OF SHELL. - 3. _Mya arenaria._ 4. _Corbula nucleus_] - -In the above illustration we represent the Common Gaper (_Mya -arenaria_), which burrows to a considerable depth in the sand or mud, -especially in the estuaries of rivers, from between the tide-marks to a -depth of twenty fathoms or more. It may be readily distinguished, in -common with the other species of the same genus, by the characteristic -wrinkled, membranous tube that encloses its fringed siphons, the -membrane being a continuation of the epidermis that extends over the -shell. Another characteristic feature of the genus is the large, flat -process inside the left valve for the attachment of the internal -cartilage. An allied species, _Mya truncata_, is often found abundantly -in company with the above, and may be known by the abruptly squared -posterior end. - -Other species of the _Myacidæ_ inhabit our shores, including the little -Basket shell (_Corbula nucleus_), the left valve of which is much -smaller than the right, which overlaps it. The latter, also, is covered -with epidermis, while the former, which is flat, is quite naked. - - [Illustration: FIG. 139.--_Solen siliqua_ - The valves have been separated and the mantle divided to expose the - large foot] - -We now come to the interesting family of Razor shells (_Solenidæ_), -specimens of which are washed up on almost every sandy beach, while the -living molluscs may be dug out of their burrows at low-water mark. The -shells are elongated, gaping at both ends with an external ligament; and -the hinge has usually two teeth in one valve and three in the other. The -foot of the animal is cylindrical, large and powerful; and the siphons -are short and united in the long species, but longer and only partially -united in the shorter ones. The gills are long and narrow, and are -prolonged into the inhalent siphon. - -These molluscs lie vertically in their deep burrows at low-water mark, -the opening of the burrow having a form resembling that of a keyhole. -While covered with water they occupy the upper portion of their abode, -but sink to a depth of a foot or more when the tide goes out. As we walk -along the water's edge at extreme low tide we may observe jets of water -that are shot into the air before us. These are produced by the sudden -retreat of the 'Razor-fish' to the bottom of its burrow when alarmed by -the approaching footsteps. Owing to this wariness on the part of the -mollusc, and to the considerable depth of its burrow, specimens cannot -be obtained by digging without much labour; but if a little salt or some -other irritant be dropped into the hole, the animal will soon rise to -eject it, and may then be shut out from the lower part of the burrow by -sharply driving a spade below it. This is undoubtedly the best method of -securing perfect specimens for study or preservation, but fishermen -often obtain large numbers, either for food or for bait, by suddenly -thrusting a long hook down into the gaping shells, and then pulling them -out. This method always does injury to the soft body of the animal, and -often damages the shell, but answers the fisherman's purpose exactly. - -We give illustrations of two shells belonging to the typical genus -(_Solen_), including one on Plate V.; also a British representative of -each of two other genera of the family--_Cerati-solen_ and _Solecurtus_, -the latter of which, as the name implies, contains shorter species. - - [Illustration: FIG. 140.--1. _Solen ensis._ 2. _Cerati-solen legumen._ - 3. _Solecurtus candidus_] - -The next family--the _Tellinidæ_--contains a number of well-known -molluscs that burrow into sand or mud, and are enclosed in shells that -are often very prettily marked; and although the family includes several -genera, all may be recognised by the following general features. The -shell is compressed, composed of two equal valves, with little or no -gape, and the ligament situated on the shortest side. The central or -_cardinal_ teeth never exceed two in number in each valve, and the -adductor impressions are round and polished. The mantle is quite open at -the anterior end, and its margins are fringed; the foot is flattened and -tongue-shaped; and the siphons, which are quite separate, are generally -long and slender. - -In the typical genus (_Tellina_), of which we represent two very common -British species, the ligament is very prominent, and the slender siphons -are often much longer than the shell. The members of this group move -very freely, travelling about by means of a broad, flattened foot. - - [Illustration: FIG. 141.--_Tellinidæ_ - 1. _Psammobia ferroensis._ 2. _Donax anatinus._ 3. _Tellina - crassa._ 4. _Tellina tenuis._ 5. _Donax politus_] - -The shells of the genus _Psammobia_ are popularly known as Sunset -shells, being prettily marked with radiating bands of pink or other -tint, reminding one of the beams of the sun when setting in a cloudy -sky. In these, too, the ligament is very prominent, and the shell gapes -slightly at both ends. - -The same family contains the pretty little Wedge shells, which are so -called on account of their triangular form, and constitute the genus -_Donax_. These shells, which are seldom much over an inch long, are very -common on some of our sandy beaches, being washed up in considerable -numbers after the animals have died, but the specimens are seldom -perfect. The molluscs themselves are burrowers, and live in the sand, at -and just below low-water mark; and, as they usually burrow to a depth of -only a few inches, are easily obtained alive. - -The shells are rather thin, closed at both ends, blunt and rounded at -the anterior end, but straight and more pointed at the shorter -posterior end; and the margins of the valves are very finely grooved in -such a manner as to resemble the milling of a coin. Each valve has two -central hinge teeth, with one long lateral tooth on each side; and the -ligament is external and prominent. The lobes of the mantle are fringed; -the siphons are separate and diverging, but shorter and thicker than in -most of the other _Tellinidæ_, and the foot is comparatively large, -flattened, and pointed. - -The genus contains many species, the commonest being, perhaps, _D. -anatinus_, the colour of which is yellowish, banded with brown, and -marked by a number of radiating white lines. This colour, however, is -due entirely to the thin, shining epidermis that completely covers the -valves; and if this is rubbed off the shell itself will exhibit a pale -pinkish tint. Another common species (_D. politus_) may be recognised by -the broad patch of white running from the hinge to the margin, on the -posterior side of the middle of each valve. - -The family _Mactridæ_ contains some British shells popularly known as -Trough shells, and the family name itself is derived from the word -_mactra_, which signifies a kneading trough. In this group the shells -are all more or less triangular in form, with the valves equal, and are -either closed or very slightly gaping. The ligament, perhaps more -correctly designated the cartilage, is generally internal, and contained -in a deep triangular hollow; and the shell is covered with epidermis. -The mantle of the animal is open in front, and the siphonal tubes are -united and fringed. The foot is usually large and flattened. - -The typical genus, _Mactra_, contains some common molluscs that bury -themselves just beneath the surface of sandy beaches; and these are so -abundant in some parts of Great Britain that they are used largely for -feeding pigs. Some of the mactras are remarkable for the great power and -extensibility of the foot, which, in some cases, is used so vigorously -that the animal turns itself quickly over, or even leaps on the ground. - -Our example of this genus is _M. stultorum_, which is a very common -object of the shore. Its colour is very variable, usually some shade of -grey or brown, and marked by radiating white lines. - -The Otter shells (_Lutraria_), of which we figure one species, are much -like the _Mactræ_ in structure, and are usually included in the same -family, but in some respects they resemble the _Myacidæ_ or Gapers. The -shell is oblong rather than triangular, and gapes at both ends; and the -animal buries itself deep in sand or mud, principally in the estuaries -of rivers, from low-water mark to a depth of about ten fathoms. The -shells are not very common objects of the shore, for they are found only -in muddy places, and those of the commonest species (_L. elliptica_) are -too large and heavy to be washed ashore in the sheltered estuaries where -they abound. - - [Illustration: FIG. 142.--1. _Lutraria elliptica._ - 2. PART OF THE HINGE OF _Lutraria_, SHOWING THE CARTILAGE PIT. - 3. _Macra stultorum._ 4. INTERIOR OF SAME SHOWING PALLIAL LINE] - -We now leave the burrowers, to consider a family of molluscs that move -about somewhat freely by means of a flattened tongue-shaped foot, and -which only rarely fix themselves in any way. The shells of the group are -popularly known as Venus shells, probably on account of the beauty of -some of the species, and the family in question as the _Veneridæ_. - -The shells of the various species are usually of a graceful oval or -oblong form, frequently marked by chevron-shaped lines in pretty -colours, and distinctly grooved along the lines of growth. The ligament -is external, the hinge has usually three diverging teeth in each valve, -and the pallial line is sinuated. - -The principal genus is _Venus_, in which the shells are ovate in form, -thick, and smooth, and the margins of the valves are minutely -crenulated. The genus is a very large one, and contains several British -species, two of which we represent in the accompanying illustrations. - -Allied to these is the larger but pretty shell _Cytherea chione_, which -inhabits deep water off the southern coasts, to about one hundred and -fifty fathoms. It is much like the _Venus_ shells in form, but the -margins are not crenulated. - - [Illustration: FIG. 143.--_Veneridæ_ - 1. _Venus fasciata._ 2. _Venus striatula._ 3. _Tapes virgineana._ - 4. _Tapes aurea_] - -The same family (_Veneridæ_) contains the large genus _Tapes_, so called -because many of its shells are marked in such a manner as to recall the -patterns of tapestry. The general form of these shells is oblong, and -the margins are quite smooth. They are frequently washed up on the -beach, especially during storms, but the animals may be found alive at -low water, buried in sand, or hiding in the crevices of rocks or among -the roots of the larger sea weeds. The mantle is open at the anterior -end, and the siphons are either quite distinct or only partly united. - -Some of the shells are very prettily coloured. One (_T. aurea_) receives -its name from the yellow ground, which is variously marked by deeper -tints; another (_T. decussata_) is so called on account of the cross -grooves with which the shell is sculptured; and a third (_T. -virgineana_), which inhabits the muddy bottoms of deep water, is -prettily marked by radiating bands that run from the umbones to the -ventral margins. - -We now come to the family _Cyprinidæ_, in which the shell is regular in -form, oval or elongated; and the valves, which are equal in size, are -thick and solid, and fit closely. The teeth are beautifully formed, the -central ones numbering from one to three in each valve, and the pallial -line is not sinuated. The mantle lobes are united on the posterior side -by means of a kind of curtain that is pierced by two siphonal openings. -There are two gills on each side, united posteriorly, and the foot is -tongue-shaped and thick. - -The typical genus--_Cyprina_--contains a large mollusc (_C. islandica_), -which is moderately common round our shores, especially in the north, -but is not often seen above low-water mark, except when washed up by -storms. The shell is oval and thick, with the umbones prominent and -turned towards the posterior side, and the ligament is strong and -prominent. It is entirely covered with a thick epidermis, of a rich -brown colour, often exhibiting a fine silky gloss, especially near the -margins. The interior of the shell is white, and the adductor -impressions oval and polished. - -The same family includes some smaller shells that inhabit deep water, -and are therefore not commonly seen on the beach. Among these are two -species of the genus _Astarte_, one of which is deeply furrowed in a -direction parallel with the margins; also _Circe minima_, which seldom -exceeds half an inch in length. Although so small compared with -_Cyprina_, these shells may be identified by their clothing of -epidermis, together with the family characteristics given above. - -The _Cyprinidæ_ also contains the interesting Heart Cockle (_Isocardia -cor_), the form of which is so characteristic that identification is -easy. The heart-shaped shell is thick and strong, and is swollen out in -such a manner that the umbones are wide apart. These latter are also -curved into a spiral form, and the ligament between them is prominent. -The colour of the shell is variable, the epidermis being of any shade -from a yellow to a dark brown. The foot is small and pointed, and the -siphons fringed. - -The Heart Cockle burrows in sand by means of its foot, going down just -far enough to bury the whole of its shell, and always leaving its -siphons exposed at the surface. It inhabits deep water, and is not -likely to be obtained without the use of the dredge or trawl. - - [Illustration: FIG. 144.--_Cyprinidæ_ - 1. _Cyprina islandica._ 2. _Teeth of Cyprina._ 3. _Astarte - compressa._ 4. _Circe minima._ 5. _Isocardia cor_] - -The molluscs of the family _Lucinidæ_ are found principally in tropical -and sub-tropical seas, ranging from the shore to a very great depth, but -a few are moderately common in our own waters. They are closely allied -to the _Cyprinidæ_, but the shell is round rather than oval, and is -obliquely grooved inside. The mantle lobes of the animal are not united -on the ventral side, but at the posterior end they are continuous, -except where they form one or two siphonal openings. The foot is long -and of almost the same thickness throughout when extended; and the -gills, numbering either one or two on each side, are large and thick. In -all the members of this family, as in the last, the pallial line of the -shell is simple. None of the shells are really common objects of our -shores, since the animals inhabit deep water, some of them moving about -freely on the bottom, while others moor themselves by means of a byssus. - -We shall take only one example of the family--_Galeomma Turtoni_--the -generic name of which means 'weasel eye.' This pretty little mollusc may -be found on our southern coasts, where it often moors itself to the -rocks or weeds by means of its silken byssus; or, having broken itself -away from its temporary place of rest, creeps freely on the bottom by a -long, flattened foot, applied closely to the surface over which it -travels, and used much in the same way as the broad foot of a snail or -whelk, its valves being all the time spread out nearly in the same -plane. - - [Illustration: FIG. 145.--_Galeomma Turtoni_] - -The shell itself is oval, with central umbones, and is covered with a -thick epidermis. The mantle lobes are united behind, where they form a -single siphonal opening; and the margins are double, with a row of -eye-like spots on the inner edge of each. - -The true Cockles, some few species of which are known to almost every -one, constitute the family _Cardiadæ_, so called on account of the -cordate or heart-shaped form of the shell as viewed from the anterior or -posterior side. The shell is regular, or nearly so, and the valves, -which are equal, are ornamented with prominent rays that run from the -umbones to the margin. The ligament is short, strong and prominent, and -the valves fit closely by the interlocking of their crenulated margins, -or gape slightly on the posterior side. There are two central teeth in -each valve, and a long lateral tooth both on the anterior and posterior -sides. The mantle lobes are open in front, with the margins plaited, and -the siphons, which are usually short, are provided with a number of -little tentacles. The foot is large and powerful, and is usually curved -into the form of a sickle. - -Although the general nature of the common edible cockle (_Cardium -edule_) is so well known even to the inhabitants of inland towns that a -description may seem out of place here, yet it is possible that but few -of our readers have ever taken the trouble to place the animal in a -vessel of sea water, either obtained direct from the sea or artificially -prepared, for the purpose of studying its movements or other habits; -and it will be well to remember that this and several other species of -edible molluscs which reach our towns alive may be very conveniently -studied at home, and often at times and seasons when work at the -sea-side is undesirable or impossible. - - [Illustration: FIG. 146.--1. _Cardium pygmæum._ 2. _Cardium fasciatum._ - 3. _Cardium rusticum_] - -The edible species referred to lives in banks of sand or mud, buried -just below the surface, and frequently in spots that are exposed for -several hours between the tides. They are usually obtained by means of a -rake similar to that used in our gardens. - - [Illustration: FIG. 147.--_Cardium aculeatum_] - -On the coasts of Devon and Cornwall we find a much larger species, also -valued as an article of diet, and known locally as the Prickly Cockle -(_C. aculeatum_). Its shell is beautifully formed, the rays being very -prominent, each bearing a number of calcareous spines arranged in a -single row. We give an illustration of this species, together with two -sketches to show the nature of the teeth of the shell. - -In addition to the two species named, we have the red-footed, _C. -rusticum_, which can suddenly turn itself over by the action of its -powerful pedal organ; the Banded Cockle (_C. fasciatum_), a very small -species distinguished by the brown bands of the shell; and a still -smaller one (_C. pygmæum_), with a triangular shell, occurring on the -Dorset and Devon coasts (fig. 146). - -Passing now to the _Asiphonida_, we deal first with the family _Arcadæ_. -These include a number of shells which, though very variable in general -form and appearance, may all be recognised by the long row of similar -comb-like teeth that form the hinge. The shells of this group are -regular in form, with equal valves, and are covered with epidermis. The -mantle of the animal is open, the gills are united by a membrane behind, -and the foot is large, curved, and grooved. - - [Illustration: FIG. 148.--_Pectunculus glycimeris_, WITH PORTION OF - VALVE SHOWING TEETH, AND _Arca tetragona_] - -One of the prettiest shells in the family is _Pectunculus glycimeris_, -which reaches a length of about two inches. The shell is grooved in the -direction of the lines of growth, and there are also very delicate -striations running radially from umbones to margin; and the ground -colour of white or pale yellowish is beautifully mottled with reddish -brown. We give a figure of this species, together with a drawing of the -peculiar and characteristic teeth, but a more typical shell of this -family may be seen in the Noah's Ark (_Arca tetragona_). This shell is -almost quadrate in form, swollen, and strongly ribbed. The hinge is -straight, with many comb-like teeth--increasing in number with the age -of the shell; and the umbones are separated by a diamond-shaped -ligament. The foot of the animal is heeled--that is, it has a creeping -surface that extends backwards as well as forwards; the mantle is -furnished with minute eyes (_ocelli_), and the animal has two distinct -hearts. We give a figure of this peculiar shell, and the other British -members of the same genus, though varying more or less in form, may be -recognised at once by the same general characteristics. - -In the same family we have the small nutshells (genus _Nucula_), which -are often dredged up from deep water in large numbers; and the elongated -shells of the genus _Leda_, also inhabitants of deep water; and, as -before stated, the affinities of all may be readily established by the -characteristic nature of the teeth. - -We now pass on to the family of Mussels (_Mytilidæ_), of which the -common Edible Mussel (_Mytilus edulis_) is a typical species. In this -interesting group the shell is oval or elongated, with equal valves, and -is covered with a dark-coloured epidermis which is often distinctly -fibrous in structure. The umbones are at the anterior end of the shell, -which end is usually very narrow and pointed, while the posterior is -broad and rounded. The hinge has small teeth or none, and the ligament, -which is long, is internal. The shells of mussels consist of two -distinct layers; on the inner, which is often of a most beautiful pearly -lustre, may be traced the simple pallial line and the impressions of the -small anterior and the large posterior muscles. - -The mantle lobes of the animal are united only at a point between the -two siphonal openings. There are two elongated gills on either side, and -the foot is thick and more or less grooved. - - [Illustration: FIG. 149.--_Mytilus edulis_] - -Mussels inhabit salt, brackish, and fresh waters, generally attaching -themselves by means of a silken byssus, but sometimes concealing -themselves in ready-made holes, or in burrows of their own; and some -even hide themselves in a nest which they prepare by binding together -fragments of shells or sand. - -The edible mussel, which forms such an important article of diet, -especially among the poorer classes in our large towns, may be easily -distinguished from similar species of another genus by the very pointed -umbones, and the coarse and strong fibrous byssus by which it clings to -any solid object. It is found most abundantly on muddy coasts, and on -mud banks in the estuaries of rivers, generally in such situations as -are uncovered at low tide. The fry abound just below low-water level, -and grow so rapidly that they reach their full size in a single year. - -It is well known that a diet of mussels occasionally produces very -unpleasant and even dangerous symptoms in the consumer, and this result -has been attributed to the action of a particular organ of the animal -which has not been carefully removed before eating. This, however, is -not the case, as proved by the fact that the eating of these edibles is -usually perfectly safe when no such precautions have been taken. It is -highly probable that the deleterious character referred to is due to a -disease which sometimes attacks the mussels themselves, but the exact -nature of this has not been thoroughly made out. - - [Illustration: FIG. 150.--1. _Modiola modiolus._ 2. _Modiola tulipa._ - 3. _Crenella discors_] - -There is another genus (_Modiola_) containing several species commonly -known as Horse Mussels, and these may be distinguished from _Mytilus_ by -their habit of burrowing, or of constructing a nest by spinning together -various fragments. The shell, also, is more oblong in form, and much -swollen near the anterior end; and the umbones are not so pointed. The -epidermis covering the shell is of fibrous structure, and often extends -beyond the edges of the valves in the form of a fringe. - -Several species of Horse Mussels inhabit our shores, from low-water mark -to a depth of fifty fathoms, but none of them is used for food. The -commonest species is _Modiola modiolus_, which has a particularly strong -byssus, and its fibres generally bind together such a number of stones -&c. that the shell is completely hidden in the entangled mass. Other -British species include _M. barbata_, so called on account of the -peculiar fringed threads of the epidermis; _M. phaseolina_, in which -the epidermis threads are not fringed; and _M. tulipa_, named from the -streaks of crimson or purple that radiate from the umbones of the shell -and remind us of the colouring of the tulip flower. - -An allied sub-genus (_Crenella_) includes a few small British molluscs -the shells of which are crenulated on the dorsal margin behind the -ligament. The shells are short and swollen, and lined by a brilliant -pearly layer. One species (_C. discors_) is pale green, with radiating -lines from umbo to margin. It is common on many of our shores, but is -not easily found, as it hides at or below low water mark, in a nest -formed by binding together small stones. Other species, one of which is -black, are less abundant, and are not readily obtained except by the use -of the dredge. - -Before leaving this family we must refer to the remarkable _Dreissena -polymorpha_, sometimes called the Chambered Mussel, on account of the -chamber which is formed in the beak of the shell by means of a pearly -plate that stretches across it. This animal is not indigenous to -Britain, but was introduced from the East by trading vessels, either -attached by its silken byssus to timber that had been left floating in -water previous to being shipped, or to the bottoms of the ships. It -seems to thrive almost equally well in salt, brackish, and fresh waters, -and has spread very rapidly since its introduction. It is more commonly -found, however, in docks, canals, and rivers, and is on that account -usually described with the fresh-water species. - - [Illustration: FIG. 151.--_Dreissena polymorpha_] - -The form of the shell is very similar to that of _Mytilus_, but has no -internal pearly layer, and the valves are bluntly keeled. The mantle is -closed, the siphons short, and the foot small. - -Our next family--the _Aviculidæ_--contains those shells that are -distinguished by peculiar flat processes on each side of the umbones, -one of which, the posterior, is generally wing-like in form. They are -popularly known as Wing Shells, and the family includes the so-called -Pearl Oysters. Most of the species are natives of tropical seas, but -several are common on our own shores. - - [Illustration: FIG. 152.--_Avicula_, AND _Pinna pectinata_] - -One species of the typical genus is sometimes found off the coasts of -Cornwall and Devon. The shell is very oblique, and the valves are -unequal, the right one, on which the animal rests, being somewhat -smaller than the left; and the epidermis is very scanty. The hinge is -long and straight, without teeth, and the cartilage is contained in -grooves. The interior of the shell is pearly. The posterior adductor -impression is large, and not far from the middle of the shell, while the -anterior, which is small, is close to the umbones. The mantle of the -animal is open, and the margins of the lobes fringed; and the small foot -spins a powerful byssus. - -Most of the British species of the family belong to the genus _Pinna_, -so called on account of the fins or wings on the dorsal side of the -shell. In this group the shell is more or less wedge-shaped, with equal -valves, and the umbones are quite at the anterior end, while it is -blunted and gaping at the other end. The hinge has no teeth. The margins -of the mantle are doubly fringed, and the byssus is extremely powerful. - -The Common Pinna (_P. pectinata_) is a very large mollusc, sometimes -measuring a foot in length, and is very abundant off the south-west -coast, where it moors itself vertically at the bottom of the water with -the pointed end buried, and the broad end gaping widely so as to expose -its body. It has been stated that fishes are frequently tempted to -intrude into the open shell for the purpose of devouring the animal -within, and that they are immediately crushed by the sudden closing of -the valves, which are pulled together by two large and powerful -adductors. - -We have already referred to the little Pea Crab that inherits the shell -of the Pinna, living permanently in the mantle cavity of the animal. - -The last family of the Lamellibranchs is the _Ostreidæ_ or Oysters, of -which the edible oyster may be taken as a type. In this group the shells -are frequently unequal, and they lie on one side either free or adherent -to the surface below them; the hinge is usually without teeth. The -mantle is quite open, the gills number two on each side, and the foot is -either small or absent. - -The Edible Oyster is a type of the typical genus _Ostrea_, its -scientific name being _Ostrea edulis_; and as this mollusc may be -readily obtained at any time, it is a convenient species for the study -of the general characteristics of its family. Its shell is irregular in -form, and the animal always rests on its left valve, which is convex, -while the upper or right valve is either flat or concave. The lower -valve is also thicker and laminated in structure, and is attached to the -surface on which it rests. On examining the interior we find that the -shell is somewhat pearly in appearance, and that the edges of the mantle -lobes are finely fringed. The gills, too, are united with each other and -with the mantle on the posterior side, thus forming a distinct branchial -chamber. - -Oysters are found on banks at the depth of several fathoms, where they -spawn in early summer, and the fry or spats are collected in large -numbers and transferred to artificial beds or tanks, where they are kept -in very shallow water so as to be easily obtainable when required for -food. It is interesting to note, however, that their growth is slow on -these artificial grounds, the full size being attained in about seven -years, while, in the natural beds, they are full grown in a little more -than half that time. - -Native oysters--those that are reared on artificial beds--are of course -removed as soon as they are ready for the market, but those that live on -natural banks are often left undisturbed till their shells are thick -with age. The latter, too, are often destroyed in large numbers by the -boring sponge (p. 124), which so completely undermines the substance of -the shell that it finally breaks to pieces. - -In the genus _Anomia_ the lower valve is concave, and perforated with a -large oval hole very near the hinge, while the upper one is very convex, -but the shell is very variable in shape, since the animal sometimes -clings permanently to an object, and the shell, during its growth, -accommodates itself to the surface of that object. The use of the hole -is to allow of the protrusion of a set of muscles which proceed from the -upper valve, and give attachment to a plug or button, more or less -calcified, by which the animal clings. - - [Illustration: FIG. 153.--1. _Anomia ephippium._ 2. _Pecten tigris._ - 3. _Pecten_, - ANIMAL IN SHELL] - -One species (_A. ephippium_), known as the Saddle Oyster, is common on -some parts of our coast. It is seldom found on the beach at low water, -but the empty shells are often washed up by the waves. - -The same family includes the Scallops, which constitute the genus -_Pecten_. In these the shell is nearly round, with ears on each side of -the umbones, those on the anterior side being generally much more -prominent than the others, and both valves are ornamented by prominent -radiating ribs. The shell is often very prettily coloured, and the -animal rests on the right valve, which may be distinguished from the -left by its greater convexity, and by the presence of a notch under -the anterior ear. The hinge is straight, with a very narrow ligament, -and the internal cartilage is situated in a central pit. - - [Illustration: PLATE V. - - MOLLUSCS - - 1. Solen ensis - 2. Trivia Europæa - 3. Trochus umbilicatus - 4. Trochus magnus - 5. Littorina littorea - 6. Littorina rudis - 7. Haminea (Bulla) hydatis - 8. Tellina - 9. Capulus hungaricus - 10. Chrysodomus antiquus - 11. Buccinum undatum - 12 & 13 Scalaria communis - 14. Pecten opercularis - 15. Pecten varius - 16. Pecten maximus] - -The mantle of the animal is free, with double margins, the inner of -which forms a finely fringed curtain all round, and on this curtain are -a number of black eyes surrounded by very fine tentacles. The gills are -in the form of very thin crescents, and the foot is shaped like a -finger. - -Although the majority of scallops are inhabitants of tropical seas, -several species are to be found off our coasts, where they range from -depths of about four to forty fathoms, and the empty shells, often in -the most perfect condition, are frequently found on the beach. - -The Common Scallop (_P. maximus_) is largely used as food, and is -therefore a common object in the fishmonger's shop. Its colour is very -variable, and the shell has equal ears and about twenty radiating ribs. -The Quin (_P. opercularis_) is also an important article of diet in some -parts. - -Perhaps the prettiest of the British species is the Variable Scallop -(_P. varius_), so called on account of the very variable colour of the -shell, the ground tint of which may be almost anything between a very -pale yellow and a dark reddish brown, and this is irregularly patched -with some lighter colour. The chief distinguishing features of the -species are the spiny projections of the numerous ribs, most prominent -near the margin of the valves, and the presence of a permanent byssus, -which, in other species, occurs only in the young. Three of the species -named above are shown on Plate V. - -We may also mention the Tiger Scallop (_P. tigrinus_), the radiating -ribs of which are sometimes slightly formed, and which has only one ear -in each valve; and _P. pusio_, in which the adult shell is often greatly -altered in form. - -It may be noted, in conclusion, that all the species of this genus have -the power of swimming rapidly by flapping their valves--a mode of -locomotion very common among the bivalves especially during an early -stage of their existence. - -Before passing on to the univalve molluscs, we must refer briefly to a -group of animals that are enclosed in bivalve shells, and which were -once included with the Mollusca, but are now made to form quite a -distinct group by themselves. We refer to the Brachiopods, at one time -very abundant, as proved by the immense number of fossil shells embedded -in various stratified rocks, but now represented by only a few living -species. - -The shells of these animals are commonly known as Lamp Shells, on -account of their resemblance to an antique lamp; and although at first -sight they bear a general likeness to certain bivalve shells of -lamellibranchs, a close examination will show that not only the shell, -but also the animal residing within it, are both of a nature very -different from that of the molluscs with which they were at one time -supposed to be closely related. - - [Illustration: FIG. 154.--_Terebratulina._ THE UPPER FIGURE REPRESENTS - THE INTERIOR OF THE DORSAL VALVE] - -The valves of the shell are unequal, and are not placed respectively on -the right and left sides of the body of the animal, but rather on the -dorsal and ventral or upper and lower sides. The ventral shell is the -larger, and is produced into a beak which sometimes has a round hole -corresponding in position with the hole for the wick of an antique lamp, -and the dorsal or smaller valve is always imperforate. The hinge is a -perfect one, the junction of the two valves being so well secured by it -that it is impossible to separate them without injury. It is formed by -two curved teeth on the margin of the ventral valve that fit into -corresponding sockets on the dorsal. A few brachiopods, however, have no -hinge, the valves being secured by means of numerous muscles. The hole -in the shell serves for the protrusion of a pedicel or foot by means of -which the animal is enabled to attach itself. - -Two long arms, covered with vibratile cilia, and capable of being folded -or coiled, are attached at the sides of the mouth. They are practically -processes of the lips, mounted on muscular stalks, and attached to a -delicate calcareous loop on the dorsal valve; and serve not only to -produce water currents for the conveyance of food to the mouth, but also -answer the purpose of gills. - -The digestive system of a brachiopod includes an oesophagus that leads -into a simply formed stomach round which is a large digestive gland. The -heart has only one cavity, but the animal is provided with two smaller -and separate organs that assist in the propulsion of the blood, which -circulates through numerous blood spaces in the bristly mantle. - -About two thousand fossil species of brachiopods are known, extending -over a vast range of time; and the living species, numbering less than a -hundred, are found from shallow water to the greatest habitable depths. - -Since the reader is hardly likely to form any extensive acquaintance -with the Brachiopods, we shall illustrate our remarks by the -introduction of only one species--the Serpent's Head Terebratula -(_Terebratulina caput-serpentis_), which is found in deep water in the -North Sea. The interior of the dorsal valve, showing the calcareous loop -above referred to, is represented in fig. 154, as is also the exterior -of the shell, which is finely striated. The latter represents the dorsal -aspect of the shell in order to show the hole in the upturned beak of -the ventral valve. - - [Illustration: FIG. 155.--UNDER SIDE OF THE SHELL OF _Natica catena_, - SHOWING THE UMBILICUS; AND OUTLINE OF THE SHELL, - SHOWING THE RIGHT HANDED SPIRAL] - -We have now to consider the large group of head-bearing molluscs -(_Cephalophora_), the study of which forms a very important part of the -work of the sea-side naturalist; and while we deal with the general -characteristics of this group, the reader will do well to have before -him a few living typical species in order that he may be able to verify -as many as possible of the descriptions here given by actual -observation. These types may include such creatures as the whelk, -periwinkle, and limpet; or if marine species are not at hand at the -time, the garden snail, fresh-water snail, and slug will serve the -purpose fairly well. - -By far the large majority of Cephalopods are enclosed in a single shell, -though a few have a rudimentary shell or none at all. - -As is the case with the lamellibranchs, the shell is composed of both -animal and mineral substance, the latter being a calcareous deposit -secreted by the mantle of the animal. The shell is usually spiral in -form, as in the whelk, but sometimes conical (limpet) or tubular. - -Spiral shells are nearly always _dextral_ or right-handed; that is, if -we trace the direction of the spiral from the apex to the mouth, we -find that its turns or whorls run in the same direction as the hands of -a watch. A few, however, are _sinistral_, or left-handed, and -occasionally we meet with left-handed varieties of those species that -are normally of the right-handed type. The cavity of the shell is a -single spiral chamber which winds round a central pillar, and each whorl -of the shell generally overlaps the preceding one, the two being -separated externally by a spiral depression called the _suture_. - -Sometimes the coils of a shell are not close together internally, so -that the central column of the spiral is hollow, and opens to the -exterior at the base of the shell. In this case the shell is said to be -_umbilicated_, and the opening referred to is the _umbilicus_. In others -the spiral winds round a solid central pillar which is spoken of as the -_columella_. - - [Illustration: FIG. 156.--SECTION OF THE SHELL OF THE WHELK, SHOWING - THE COLUMELLA] - -The apex of the shell, sometimes called the _nucleus_, is the oldest -part, and represents what was once the whole. It is generally directed -backwards as the animal crawls, and in adult shells is often more or -less worn away by constant friction. We speak of the whorls as first, -second, third, &c., taking them in the order of their growth, and it -will generally be found that the last whorl is much larger than the -others, so much so that it contains the greater part of the body of the -animal; hence this one is commonly spoken of as the _body-whorl_, and -the others make up the _spire_ of the shell. - -The mouth of the shell is of different forms in different species, but -in the herbivorous kinds it is usually simple, while in the carnivorous -species it is notched or produced. The edge of the mouth (_peristome_) -is formed by an _outer lip_ which is usually sharp in young shells and -either thickened, reflected (turned outward), or inflected (turned -inward) in adults; also it may be considerably expanded, or ornamented -by a fringed margin. The _inner lip_ is that side of the peristome -adjacent to the central pillar of the shell. - -If we examine the external surface of several different shells, we find -that they are usually more or less distinctly furrowed or sculptured, -and that they are often marked by lines or bands of a colour different -from that of the ground tint. These furrows, lines, or bands sometimes -pass directly from the apex, across the various whorls, to the base of -the shell, in which case they are said to be _longitudinal_. If they -follow the course of the whorls, they are described as spiral; and if -parallel with the peristome, so that they mark the former positions of -the mouth of the shell, thus denoting the _lines of growth_, they are -said to be _transverse_. - -Most univalve shells are covered with epidermis, but in some instances -the animal, when extended, surrounds the exterior of the shell with its -mantle, as do the cowries, and then the outside of the shell is always -glazed. Other species keep their shells covered with the mantle, and in -these the shell is always colourless. - -The body of the head-bearing mollusc is attached to the shell internally -by one or more muscles, and if we examine the interior surface we are -generally able to distinguish the impressions or scars denoting the -points of attachment. - -The reader will have observed that the periwinkle, whelk, and other -univalves close their shells by a kind of lid when they retract their -bodies. This lid is called the _operculum_, and is constructed of a -horny material, often more or less calcified on the exterior, and is -attached to the hinder part of the foot. It sometimes fits accurately -into the mouth of the shell, but in some species it only partially -closes the aperture. The operculum, like the shell itself, often -exhibits distinct lines of growth which display the manner in which it -was built up. If these lines are concentric we know that the operculum -grew by additions on all sides; but if its nucleus is at one edge, and -the lines of growth widest apart at the opposite side, the growth must -have taken place on one side only. Some, even, are of a spiral form, -denoting that the additions were made continuously at one edge, and such -opercula may be right-handed or left-handed spirals. - -It will be noticed that in the above general description of univalve -shells we have introduced a number of technical terms which are printed -in italics, and this we have done advisedly, for the employment of these -terms is a very great convenience when giving descriptions of individual -shells, and we shall use them somewhat liberally in noting the -distinguishing characteristics of the families and genera; but before -entering into this portion of our work we must briefly note the general -features of the bodies of the _Cephalophora_. - - [Illustration: FIG. 157.--DIAGRAM OF THE ANATOMY OF THE WHELK, THE - SHELL BEING REMOVED - - _c_, stomach; _e_, end of intestine; _g_, gills; _h_, ventricle of - the heart; _a_, auricle; _f_, nerve ganglia; _b_, digestive gland; - _ft_, foot; _o_, operculum; _d_, liver] - -Sometimes these bodies are bilaterally symmetrical, as we have observed -is the case with the worms, but more commonly the organs on one side are -aborted, while the growth proceeds apace on the opposite side. Thus the -animal assumes a spiral form, being coiled towards the aborted side, -with the gills and other organs developed on that side only. As a rule -this curvature is such that the body takes the form of a right-handed or -dextral spiral, as we have already observed in the shells which cover -them, the mouth being thus thrown to the right, but sometimes it takes -the opposite direction. - -When one of these animals is extended and creeping, we observe that it -has a distinct head, furnished with a mouth below, and tentacles and -eyes above; also, if an aquatic species, the gills are more or less -prominent. Further, the exposed portion of the body is covered with a -leathery mantle, and the animal creeps on a broad, flattened surface -which is called the foot. - -The tentacles or feelers are usually retractile, and, when retracted, -are turned outside-in. Each one is provided with a muscle that runs from -the body internally to the tip; and, by the contraction of this muscle -the tentacle is involuted just in the same way as the finger of a glove -could be by pulling a string attached to the tip inside. In addition to -these tentacles, and the eyes and mouth previously mentioned, the head -is furnished with ear-sacs, which are little cavities, filled with fluid -containing solid particles, with nerve filaments distributed in the -walls. - -On the floor of the mouth there is a ribbon, supported on a base of -gristle, and covered with numerous minute teeth arranged regularly in -rows. The gristle is moved backwards and forwards by means of muscles in -such a manner that this 'lingual ribbon' acts like a rasp, and is -employed in scraping or tearing away portions of the substance on which -the animal is feeding. By this action the teeth are gradually worn away -in front, but this is of no consequence, for the lingual ribbon is -always growing forwards, the worn material being replaced by new growth -behind. - - [Illustration: FIG. 158.--A PORTION OF THE LINGUAL RIBBON OF THE WHELK, - MAGNIFIED; AND A SINGLE ROW OF TEETH ON A MUCH LARGER SCALE - _b_, medial teeth; _a_ and _c_, lateral teeth] - -The arrangement and form of the teeth are characteristic and important; -and since they afford one of the means by which we may trace the natural -affinities of similar species, they will be frequently referred to when -dealing with the principles of classification. For this reason the -student should be prepared to examine the lingual ribbons of molluscs -with the aid of a compound microscope as occasion requires. As a rule -the ribbon is easily stripped away from the floor of the mouth; and, if -placed in a drop of water and covered with a cover-glass, the teeth are -readily observed. Until a little experience has been gained the -observations may be confined to some of the larger species, in which the -ribbon is both large and easily obtained. In the common whelk, for -example, it often measures more than an inch in length. - -It is difficult to understand how the univalve mollusc manages to glide -along so rapidly and gracefully on its expanded foot when we observe it -from above, but the difficulty is cleared away when we see it creeping -on the side of a glass aquarium, or when we place it on a sheet of glass -and observe its movements from the other side. We then see that the foot -is in complete contact with the glass, and that a steady but rapid -undulatory movement is produced by the successive expansions and -contractions of the disc, brought about, of course, by the action of -muscular fibres. - -A few of the univalves are viviparous--that is, they produce their young -alive; but the majority lay eggs. The eggs are often enclosed in horny -cases, some of which may be commonly seen washed up on the beach, or -attached to rocks and weeds between the tide-marks. The larvæ are always -enclosed in a shell, though they are sometimes wholly or partially -concealed by the mantle. The shell is usually closed by an operculum; -but as the animal advances in age the shell sometimes disappears -altogether, or is reduced to a mere shelly plate, as is the case with -the land and marine slugs and sea lemons. The young of the -water-breathers always swim about freely by means of a pair of ciliated -lobes or fins, but these remain only for a brief period, after which the -animal settles to the bottom for a more or less sedentary existence. - - [Illustration: FIG. 159.--EGG CASES OF THE WHELK] - -The Cephalophora fall naturally into two fairly well-defined groups, -which we may describe as the air-breathers and the water-breathers. The -former breathe air direct from the atmosphere through an aperture on the -right side of the body, the air passing into a pulmonary organ or lung, -in the walls of which the bloodvessels ramify, and they include all the -land snails and slugs. The latter breathe by gills which are more or -less prominent on the sides of the body, and include all the fresh-water -snails, as well as the marine species which fall within our special -province. - -We shall first consider the class _Pteropoda_ or Wing-footed Molluscs, -so called from the wing-like appendages that are attached to the side of -the mouth, or to the upper side of the foot, which is either very small -or altogether wanting. - -These Pteropods are in many respects lowly organised as compared with -the higher molluscs; and as they spend the whole of their existence in -the open sea, they can hardly be considered as falling within the scope -of the sea-side naturalist's work. Yet since their shells are -occasionally drifted on to the shore, and because a knowledge of them is -essential to the student of the mollusca, we shall briefly note their -principal characteristics. - -The pteropods are extremely abundant in some seas, occurring in such -vast numbers that they discolour the water for miles. They swim about by -flapping the pair of wings already referred to. They are known to form -an important article of the diet of the whale, and are also devoured in -enormous numbers by various sea birds; and they are themselves -carnivorous, feeding on various smaller creatures that inhabit the open -waters. - - [Illustration: FIG. 160.--PTEROPODS] - -In appearance they much resemble the young of higher species of -molluscs. The nervous system consists of a single ganglion situated -below the gullet, and the eyes and tentacles are either rudimentary or -absent. The digestive system includes a muscular gizzard provided with -teeth for the mastication of food, and a digestive gland or liver for -the preparation of a digestive fluid. The heart has two cavities, and -respiration is effected by a surface covered with minute cilia. This -surface is either quite external or is enclosed in a chamber through -which water freely circulates. - -The shell is very different from that of a typical head-bearing mollusc, -for it generally consists of two glassy, semitransparent plates, -situated dorsally and ventrally respectively on the body of the animal, -with an opening for the protrusion of the body, and others at the sides -for processes of the mantle; and it terminates behind in one or three -pointed processes. Sometimes, however, its form is conical or spiral, -with or without an operculum. We append illustrations of a few -pteropods, selecting for our purpose species that have been found in the -Atlantic. - -It will have been noticed from the above short description that the -pteropod is very unlike the typical Cephalophore as outlined in our -general remarks on the group, especially in the symmetrical form of both -body and shell and in the total or almost total absence of the foot; and -this distinction is so marked that the pteropods are often separated -from all the other _Cephalophora_ into a class by themselves, while all -the remainder are placed in a separate extensive class called the -_Gasteropoda_, because they creep on the ventral surface of the body, -the term signifying stomach-footed. - -These gasteropods are divided into four orders: the _Nucleobranchiata_, -in which the respiratory and digestive organs form a nucleus on the -posterior part of the back; the Opisthobranchiata, with gills more or -less exposed towards the rear of the body; the _Pulmonifera_, or -lung-breathing order; and the _Prosobranchiata_, in which the gills are -situated in advance of the heart. The third order includes all the land -snails and slugs, and does not therefore fall within the scope of our -work; but the remaining three consist either exclusively or principally -of marine species, and will be dealt with in the order in which they are -named. - -The Nucleobranchs are not really gasteropods in the strictest sense of -the term, for they do not creep along by means of their foot, but all -swim freely in the open ocean, always at the surface, and sometimes -adhere to floating weed by means of a sucker. In fact, the foot of these -creatures is greatly modified in accordance with their habits, one part -being often expanded into a ventral swimming fin, and provided with a -sucking-disc for adhesion, and another produced into a posterior fin for -locomotion. - -Like the pteropods, the nucleobranchs are purely pelagic, so that we can -hardly expect to meet with a specimen on or near the shore; and thus we -shall content ourselves with a brief notice of their general characters. - -The shell is very variable in size and form, and sometimes even entirely -absent. Large-bodied species often possess but a very small shell, while -some are able to entirely retract themselves and close the mouth of the -shell by an operculum. These animals are generally provided with a large -cylindrical proboscis, and the tongue has recurved teeth. The body is -usually very transparent, often so much so that the blood may be seen -circulating within it, and the nervous system is much more perfectly -developed than in the pteropods. The eyes, too, are perfectly formed. - -The presence of special breathing organs may seem to be superfluous in -such delicate and soft-bodied creatures as these, for it may be supposed -that all the oxygen required could be absorbed directly from the water -through their soft structures, as is really the case with many aquatic -creatures; and as a matter of fact some of the nucleobranchs possess no -gills, but others have these organs fully formed. - -Passing now to the true gasteropods, we shall first consider the -_Opisthobranchs_, which are commonly known as Sea Slugs and Sea Lemons. -Some of these have no shell at all, and even where one exists it is very -rudimentary, usually very small and thin, and concealed within the -mantle. The gills are either branched and tree-like, or are composed of -tufts or bundles of filaments; and, as the name of the order implies, -are situated towards the posterior part of the body. They are also -retractile, and when the animal is alarmed it will conceal its gills, -thus reducing its body to a shapeless, slimy mass, inviting neither to -sight nor to touch. - -The sea slugs are principally animal feeders, subsisting on small -crustaceans, other molluscs, &c.; the food being first reduced by the -rasping action of the teeth, and then masticated in a gizzard which is -provided internally with horny spines or hard, shelly plates. - -It will not be necessary to enumerate all the different families of this -order, especially as the species are mostly to be found beyond the -tide-marks, and are therefore obtained only with the aid of the dredge; -but we shall describe a few of the British species with a view of -showing the general characteristics of the animals. - -They are usually divided into two sections, those with exposed or naked -gills (_Nudibranchiata_) forming the first, and those in which the gills -are covered either by the shell or the mantle (_Tectibranchiata_) -comprising the second. - -In the Nudibranchs the shell exists only during the embryonic stage, and -the external gills are arranged on the back or along the sides. The -tentacles are not employed as organs of touch, but are probably -connected only with the sensation of smell, being provided with -filaments of the olfactory nerve; the eyes are small dark-coloured spots -embedded in the skin behind the tentacles. Various species are to be -found on all rocky coasts, where they range from low-water mark to a -depth of fifty or sixty fathoms, but a few are pelagic, living on the -surface of floating sea weeds. - -It is almost impossible to identify the species of nudibranchs from dead -specimens, for the classification of the section is based largely on the -arrangement of the gills, which are almost always retracted in the dead -animals. This is also the case even with living specimens when disturbed -or removed from the water; hence they should always be examined alive in -sea water, while the animals are extended and moving. - - [Illustration: FIG. 161.--NUDIBRANCHS - 1. _Doto coronata._ 2. _Elysia viridis._ 3. _Proctonotus - mucroniferus._ 4. _Embletonia pulchra_] - -It will be understood from the above statements that special methods -will be necessary when it is required to preserve specimens for future -study, the gills being always retracted when the animal is killed for -this purpose by any rapid process. We have found two methods, however, -that are fairly satisfactory in the majority of instances.--Place the -living animals in a suitable vessel of sea water, and leave them quite -undisturbed till they are fully extended, and then either _gradually_ -raise the temperature till they are dead, or introduce into the water, -cautiously, a solution of corrosive sublimate. In the latter case a much -larger proportion of the sublimate will be required than when used for a -similar purpose with freshwater molluscs. When the animals are dead it -will be found that their gills are more or less extended, sometimes -fully so, and they may then be transferred to diluted spirit or a two -per cent. solution of formaldehyde. - - [Illustration: FIG. 162.--NUDIBRANCHS - 1. _Dendronotus arborescens._ 2. _Tritonia plebeia._ 3. _Triopa - claviger._ 4. _Ægirus punctilucens_] - -In fig. 162 we represent four species. Two of these--_Triopa claviger_ -and _Ægirus punctilucens_--belong to the family _Doridæ_, the members of -which are popularly known as Sea Lemons, and are distinguished by the -presence of plume-like gills situated on the middle of the back. Another -family (_Tritoniadæ_), characterised by the arrangement of the gills -along the sides of the back, and by tentacles that can be retracted into -sheaths, is represented by _Tritonia plebeia_ and _Dendronotus -arborescens_ in the same figure, and by _Doto coronata_ in fig. 161. The -family _Æolidæ_ also have their gills arranged along the sides of the -back, but they differ from the last in that their tentacles are not -retractile. They include the two species numbered 3 and 4 on fig. 161. -The remaining one on fig. 161--_Elysia viridis_--is a member of the -family _Phillirhoidæ_, characterised by a pair of tentacles on the -dorsal side of the head and by the foot being either very narrow or -absent, the latter feature denoting that the animals are not adapted for -creeping on the bottom. In fact, several of the species of this family -swim freely by means of flattened tails. - -The Tectibranchs are similar in general structure, but are very -different in appearance, inasmuch as the gills, so prominent in the last -division, are here covered by the mantle, or by the shell, which is -often well developed. The latter is very variable in form, being of a -globular, twisted, spiral, or other shape, but is sometimes absent in -the adult. In fig. 163 we give a few examples of the shells of British -species; and one (_Bulla hydatis_) is shown on Plate V. - - [Illustration: FIG. 163.--SHELLS OF TECTIBRANCHS] - -We now pass on to the largest and last order of gasteropods--the -_Prosobranchiata_--so called because the gills are situated in front of -the heart. This group is an important one to the sea-side naturalist, -since it contains nearly all the univalve molluscs that are common -between the tide-marks of our shores, as well as some abundant species -that are protected by a shell of several distinct parts. In nearly all -of them the abdomen is well developed, and the shell is sufficiently -large to cover the whole animal when the latter is retracted; and the -gills, which are either pectinated (comb-shaped) or plumed, are lodged -in the chamber formed over the head of the animal by the mantle. - -The order is often divided into two sections--the _Holostomata_ or Sea -Snails, in which the margin of the aperture of the shell is entire, and -the _Siphonostomata_, in which the margin of the mantle is prolonged -into a siphon by which water passes into the gill chamber. This division -does not seem to be very satisfactory, as the sections are not separated -by very prominent natural characteristics, but it becomes convenient on -account of the great extent of the order. - -In the _Holostomata_ the shell is either spiral, conical, tubular, or -composed of several valves, and the spiral forms are usually closed by -a horny or shelly operculum of the spiral kind. The head is provided -with a proboscis that is generally non-retractile, and the gills usually -extend obliquely across the back, or are attached to the right side -behind the head. - -We shall first consider the lower forms, starting with the family -_Chitonidæ_, the animals of which, as the name implies, are covered with -a shell that resembles a coat of mail. - -Some of these creatures are very common on our rocky coasts, and yet -their nature is such that they are liable to be overlooked by those who -are not acquainted with their appearance and habits. The shell is oval -or oblong, often so coloured as to closely resemble the rocks and stones -over which they crawl; and the animal is so inactive when left exposed -by the receding tide, and its flat under surface so closely applied to -that on which it rests, that it looks merely like a little convexity of -the rock. But after a few have been discovered the eye becomes -accustomed to their appearance, and large numbers may be obtained in a -short space of time. - -The shell will be seen to consist of eight transverse, curved plates, -overlapping each other at their edges, and all enclosed in a leathery -mantle, which also forms a projecting margin all round. The middle six -plates are different from the first and last in that they are grooved in -such a manner that each one displays a dorsal and two lateral areas. - -The animal holds on tightly to the rocks by its large creeping disc-like -foot, but may be removed without injury by forcing a knife-blade under -the margin of its shell. When examined it will be found that it has not -a well-formed head like the majority of the gasteropods, and both eyes -and tentacles are wanting. The gills form a series of lamellæ round the -posterior end of the body, between the edge of the foot and the mantle; -and it is interesting to note that the Chitons further justify the low -position assigned to them among the gasteropods by their possession of a -simple, central, tubular heart, similar to that of worms. - -Perhaps the commonest of the British species is _Chiton cinereus_. Its -colour is a dull grey, but the ground is variously mottled, often in -such a manner as to give it a protective resemblance to its -surroundings. _C. ruber_ is the largest of our species: its shell is -variously mottled with shades of yellow and brown; _C. fascicularis_ is -bristled. Another rather common species (_C. lævis_) is distinguished by -the glossy appearance of the dorsal portion of the shell. - -It will have been observed that the chitons differ from the majority of -gasteropods in that their shells and bodies are both bilaterally -symmetrical, and the same is true of the next family--_Dentaliadæ_, -which derive their name from the tooth-like form of their conical -shells. They are popularly known as the Tooth Shells, and although they -generally live beyond low-water level, they may sometimes be seen alive -on the beach, and the empty shells are often washed up by the waves. - -The shells (fig. 165) are curved, and open at both ends, the narrower -extremity being the posterior. The mouth is circular, and the outer -surface is quite smooth or grooved. - - [Illustration: FIG. 164.--CHITON SHELLS] - - [Illustration: FIG. 165.--SHELLS OF _Dentalium_] - -In these animals, too, the head is imperfectly formed, without eyes or -tentacles. The foot is conical and pointed, with two symmetrical side -lobes; and the gills, also two in number, are symmetrically disposed. -The margin of the mouth is fringed, and the animal is attached to the -shell near the posterior end. - -The _Dentaliadæ_ are carnivorous, subsisting on minute molluscs, -foraminifera, &c., and generally live on sandy or muddy bottoms, in -which they sometimes bury themselves. - -Our next family includes the familiar Limpets, and is designated -_Patellidæ_ on account of the resemblance of the conical shell to a -little dish. In these the apex of the cone is not central, but situated -more or less towards the anterior; and the muscular impression within is -shaped like a horseshoe, with its open end turned to the front. - -Unlike the members of the preceding families, the limpets have a -well-formed head furnished with both eyes and tentacles, the former -situated at the bases of the latter. They have a horny upper jaw, and -the tongue, which is very long, is supplied with numerous hooked teeth. -The foot is a very large disc, as large as the shell, and the gills -consist either of one or two branched plumes, or of a series of lamellæ -almost or entirely surrounding the animal between the shell and the -margin of the mantle. - -The reader has probably experienced the difficulty of detaching a limpet -from its hold on the rocks. The tenacity of the grip is not due to the -mere adhesive power of the foot itself, but to atmospheric pressure, the -effect of which is complete on account of the total exclusion of air -from under the disc of the foot; and when we remember that this pressure -amounts to fifteen pounds on every square inch of surface, we can -readily understand the force required to raise a large limpet from its -position. - - [Illustration: FIG. 166.--_Patellidæ_ - 1. _Patella vulgata._ 2. _P. pellucida._ 3. _P. athletica._ - 4. _Acmæa testudinalis_] - -The Common Limpet (_Patella vulgata_) is found on all our rocky coasts -between the tide-marks, often at such a level that it is left exposed to -the air for eight or nine hours at a time. The apex of the shell of this -species is nearly central, and the exterior is sometimes nearly smooth, -but more commonly relieved by radiating ribs. - -Although the shell itself is not a particularly pretty object, it is -often rendered very beautiful and interesting by the various animal and -vegetable organisms that settle on it. Those shells that are left dry -for hours together are commonly adorned with clusters of small acorn -barnacles, while the limpets that have found a home in a rock pool and -are perpetually covered with water, often resemble little moving gardens -in which grow beautiful tufts of corallines or other weeds, as well as -polyzoa and other animal forms. - -It appears that limpets are not great travellers, the appearance of the -rock from which they have been removed being such as to point to a very -long period of rest. Those on hard rocks are generally situated on a -smooth surface just the size of the shell and generally worn slightly -below the surrounding level by the constant friction of the shell; while -others that have settled on very rugged spots have their cones adapted -to the irregular surface. It has been suggested that the animals make -occasional short excursions from their chosen spot, but return again to -it; and whether or not this is the case, it is evident that they -frequently keep to one small spot for a considerable length of time. - -Limpets on chalk and other soft rocks are sometimes in circular pits so -deep that even the apex of the shell is below the general level around; -and though it is possible that the abrasion is produced entirely by the -friction of the shell as the animal turns, yet, in the case of chalk, -the action may be partly due to the carbonic acid gas given off by the -animal as a product of respiration, for it is a well-known chemical fact -that this gas, in solution, has the power of dissolving calcareous -material. - -The other British Limpets include _P. pellucida_, which lives on the -fronds and stalks of the tangle, the form of the shell varying according -to that of the surface on which it rests; also the Horse Limpet (_P. -athletica_), the bold radiating ribs of which are irregularly notched; -and _Acmæa testudinalis_--the Tortoiseshell Limpet, with reddish-brown -mottlings on the exterior, and a dark-brown patch at the apex within. -The last-named species lives principally on sea weeds, and has a single -pectinated gill in the cavity between foot and mantle, which is -protruded on the right side when the animal is extended. This latter -feature is interesting since it shows a tendency to that one-sided -development already referred to as characteristic of the typical -gasteropod, resulting in the spiral form of the adult. - -In the limpets the lingual ribbon is proportionately long, and is easily -removed for examination. In _P. vulgata_ it may exceed an inch in -length, and the teeth are arranged in rows each of which contains four -central, with laterals on either side, while in _Acmæa_ there are only -three laterals on each side of the central line. - -Other so-called limpets belong to separate families. Thus we have the -Cup-and-Saucer Limpet and the Bonnet Limpet in the _Calyptræidæ_. Both -these differ from Patella in that the apices of their shells show a -tendency to assume a spiral form, thus denoting a somewhat closer -relationship to the more advanced univalves. They have distinct heads, -with prolonged muzzles, and well-formed antennæ and eyes. The teeth of -the lingual ribbon are single, with dentated laterals on either side. - -The Cup-and-saucer Limpet (_Calyptræa sinensis_) is so called on account -of a curved plate that projects from the interior of the shell, at the -apex; and though this plate takes the form of a half-cup rather than of -a cup, the whole shell has suggested the popular name, while the generic -name is derived from _calyptra_, which signifies a cap. This mollusc is -occasionally found among stones at low tide, but usually lives beyond -this line, thus necessitating the use of a dredge. The Bonnet Limpet -(_Pileopsis hungaricus_) is of similar structure and habit, but the -nucleus of the shell is a more decided spiral (see Plate V.). Both these -animals adhere to stones and rocks, and, like the common limpet, seldom -or never move from their selected sites; hence their shells are variable -in form, being adapted to the rock below, and the movements of the shell -often cause a little hollow to be scooped out of the softer materials. - - [Illustration: FIG. 167.--_Calyptræa sinensis_] - -Yet other limpets belong to the next family _Fissurellidæ_, which is -characterised by a perforation or a notch in the shell. In these, too, -the shell is conical, with a tendency to assume the spiral form, but the -curve of the nucleus, which is always apparent in the young shell, -frequently disappears as the growth proceeds. - - [Illustration: FIG. 168.--_Fissurellidæ_ - 1. _Puncturella noachina._ 2. _Emarginula reticulata._ - 3. _Fissurella reticulata_] - -In the Keyhole Limpet (_Fissurella reticulata_) which is found chiefly -on our southern shores, the perforation is at the summit of the shell; -but as the animal grows the hole increases in size, encroaching on the -curved nucleus until the latter quite disappears. In the genus -_Puncturella_ the perforation is just in front of the recurved apex, and -is surrounded by a rim internally; while in the Notched Limpets (genus -_Emarginula_) it is represented by a fissure on the anterior _margin_ of -the cone. In all, however, the hole or notch serves the same purpose, -for it is the means by which water enters the siphon. - -It is doubtful whether we ought to claim the beautiful Ear shell -(_Haliotis tuberculata_) as one of our own, but it is generally included -among the British molluscs on the ground that it is abundant on the -coast of the Channel Islands, where it is called the Omar; and it is -certainly too beautiful an object to be excluded from the British -species without ample cause. - - [Illustration: FIG. 169.--_Haliotis_] - -It belongs to the family _Haliotidæ_, and our illustration will show -that the shell is less elevated than that of limpets, and that the -spire, though not prominent, is a fairly well-formed spiral. All along -the outer lip of the very large aperture is a series of perforations, -occupying the summit of a prominent, spiral ridge, and becoming -gradually smaller and smaller towards the spire. The whole shell is -pearly in structure, and displays a great variety of rich colouring. It -is used largely for inlaying and other ornamental purposes, and for -making the so-called pearl buttons. The animal is used largely as an -article of food in the Channel Islands, but it is of so tough a nature -that it requires a vigorous beating previously to being cooked. - - [Illustration: FIG. 170.--_Ianthina fragilis_] - -The same family contains the beautiful violet _Ianthina_, which also is -not a British species, but a free-swimming oceanic snail. It is, -however, occasionally drifted to our shores, though generally in an -imperfect condition. In the Atlantic and the Mediterranean it sometimes -abounds in such multitudes as to distinctly colour the surface of the -sea. - -It will be seen that the shell is round, with a well-formed spiral. The -spire is white, but the base is of a deep violet colour. The animal is -very remarkable in some respects. In the first place, though it has -pedicels similar to those on which the eyes of the higher univalves are -placed, yet it has no eyes. Then the foot, which is in itself small, -secretes a float or raft so large that it cannot be retracted into the -shell, with numerous air vesicles to render it light, and the -egg-capsules of the animal are attached to the underside of this. The -animal has no power of sinking, but lives exclusively at the surface; -and, when disturbed, it exudes a violet fluid that colours the -surrounding water. It is apparently the only gasteropod that lives in -the open sea and has a large and well-formed spiral shell. - -Passing now to the family _Turbinidæ_ we meet with turbinated or -pyramidal shells that are of a brilliant pearly lustre within, and -frequently without also when the epidermis is removed. The animals -inhabiting them have well-formed heads with a short muzzle, long and -slender tentacles, and eyes mounted on peduncles. The sides are -ornamented with fringed lobes and several tentacle-like filaments, and -the aperture of the shell is closed, when the animal is retracted, by a -spiral operculum. They are all vegetable feeders; and, as is usual with -the plant-eating molluscs, the teeth on the lateral portions of the -lingual ribbon are very numerous. - -We have a few common species belonging to this group, mostly members of -the typical genus _Trochus_ and commonly known as Top Shells. In these -the shell is a pyramid formed of numerous flat whorls, with an oblique -and rhomboidal aperture. Of the three species figured (including two on -Plate V.) _T. umbilicatus_ and the Large Top (_T. magnus_) are -umbilicated, the umbilicus being very large in the latter; and the -former is characterised by the zigzag greyish or reddish markings that -run radially across the whorls. The other (_T. zizyphinus_) is usually -of a yellowish or pink colour and has no umbilicus. - -The same family contains the pretty little Pheasant Shell (_Phasianella -pullas_), which is richly coloured with red, brown, and yellow on a -light ground; and _Adeorbis subcarinatus_, shown in the same group. - -The well-known Periwinkle (_Littorina littorea_) and the species to the -right of it on Plate V., belong to the family _Littorinidæ_, the -members of which are similar in structure and habit to _Trochus_, but -the shell is usually more depressed, and is never pearly. The shell of -the Periwinkle is thick, having but few whorls, and is not umbilicated; -and the lingual ribbon, which is coiled up on the gullet, contains no -less than about five hundred rows of teeth; but only a little more than -twenty of these rows are in action at any one time, the remainder being -a reserve stock to come into active service as the ribbon grows forward. -In the genus _Lacuna_ there is a narrow umbilicus, and the aperture of -the shell is semilunar in form; and the species of _Rissoa_ are very -small, with white or horny shells, much more pointed and having more -whorls than those of the _Littorina_. - - [Illustration: FIG. 171.--1. _Trochus zizyphinus._ 2. UNDER SIDE OF - SHELL. 3. _Trochus magnus._ 4. _Adeorbis subcarinatus_] - - [Illustration: FIG. 172.--_Rissoa labiosa_ AND _Lacuna pallidula_] - -Our next illustration shows three shells of the family _Turritellidæ_, -so named from the resemblance of the shells to a tower or spire. The -form indeed is so characteristic that they can hardly be mistaken. It -will be seen that _Turritella communis_ is striated spirally, while the -surface of _Scalaria communis_ (Plate V.) is relieved by strongly marked -transverse ribs. Both these species are very common, and the latter is -peculiar for its power of ejecting a dark purple fluid when molested. -The other representative of the family--_Cæcum trachea_--has a shell -something like that of _Dentalium_ (p. 238), being cylindrical and -tubular, but it differs in being closed at one end. - - [Illustration: FIG. 173.--SECTION OF SHELL OF _Turritella_] - - [Illustration: FIG. 174.--_Turritella communis_ AND _Cæcum trachea_] - -In the succeeding shells, of the family _Cerithiadæ_, the spire is also -considerably produced, so much so that some of the species closely -resemble the Turret shells, but they are distinguished by usually having -an expanded lip, at least in the adult form; and the mouth is channelled -in front, and sometimes also behind. The animals of the group have short -muzzles that are not retractile, the tentacles are wide apart, and the -eyes are mounted on short pedicels. The median teeth are arranged in a -single row, with three laterals on either side of each. - - [Illustration: FIG. 175.--_Cerithium reticulatum_ AND _Aporrhais - pes-pelicani_] - -_Cerithium reticulatum_ receives its generic name from its appearance to -a small horn, and the specific name refers to the netted appearance of -its surface due to the presence of numerous little tubercles arranged in -rows--a feature that serves to distinguish it from the small Turret -shells. It is a common shell, as is also the other representative of the -family illustrated, but the latter is rendered conspicuous by the -enormously expanded lip that has earned for it the popular name of Spout -Shell. Its scientific name is _Aporrhais pes-pelicani_, and the -application of the specific term will be understood when the shell is -viewed from above, for the expanded lip is drawn out into long -finger-like lobes that suggest the foot of a bird. This is a very solid -shell, sometimes reaching a length of two inches; and the animal -inhabiting it is carnivorous. - - [Illustration: FIG. 176.--_Aporrhais pes-pelicani_, SHOWING BOTH SHELL - AND ANIMAL] - -We have yet some turreted shells to deal with, belonging to the family -_Pyramidellidæ_, but they need not be confused with the preceding groups -if carefully examined. In the first place, the aperture of the shell is -very small; and the operculum, instead of being spiral, as in the -turreted shells before mentioned, is imbricated or made up of parallel -layers denoting that the growth took place on one side only. Another -distinguishing feature is seen in the nucleus--that small portion of the -spire that was developed within the egg--which is sinistral or -left-handed. In addition to this, the animal has broad, ear-like -tentacles, a retractile proboscis, and a lingual ribbon without teeth. - -The British species of this family belong principally to the genera -_Odostomia_, characterised by a tooth-like fold of the columella; -_Eulima_, containing small, white, polished shells with numerous level -whorls; and _Aclis_, with little polished shells not unlike -_Turritella_. - - [Illustration: FIG. 177.--1. _Odostomia plicata._2. _Eulima polita._ - 3. _Aclis supranitida_] - -The last family of the _Holostomata_ is the _Naticidæ_, the shells of -which are almost globular, with only a few whorls, and a small, blunt -spire. The mouth is semilunar in form, and the lip sharp. The proboscis -of the animal is long and retractile, and the foot large; but perhaps -the most characteristic feature is the presence of large mantle lobes -which hide some of the shell when the animal is crawling. In _Natica_ -(fig. 155), the typical genus, the shells are somewhat thick and smooth, -with a large umbilicus. As the animal crawls a large fold of the mantle -is reflected back over the head, completely covering it, and apparently -obstructing its view; but this is not the case, for the creature has no -eyes. _Natica_ is very abundant on some sandy beaches, where it devours -small bivalves and other animals; and it is frequently washed up alive -by the waves. Its shell is also a favourite one with hermit crabs. Its -eggs, all connected together in a spiral band, may often be seen -stranded on sandy coasts. Several species of Natica are found on our -shores. An allied mollusc--_Velutina lævigata_, so called on account of -the velvety epidermis that clothes the shell, completely surrounds the -shell by its mantle folds when creeping. - -The _Siphonostomata_ form a much smaller section than the last, and its -members are distinguished mainly by the presence of a true siphon, -formed by the prolongation of the mantle margin, and serving to convey -water into the gill chamber. In all these the shell is spiral, usually -without an umbilical opening, and the margin of the mouth is prolonged -into a canal or distinctly notched. The operculum is horny, and lamellar -or imbricated. The animal has a retractile proboscis, and the eyes or -eye-pedicels are joined to the tentacles. All the species of this -division are marine. - - [Illustration: FIG. 178.--_Cypræa (Trivia) europæa_] - -We will first take the family _Cypræidæ_, which contains the familiar -Cowries, these forming the lowest group of the division. An examination -of the shells may at first seem rather puzzling, for the spire is -concealed, and the whole is convoluted in such a manner as to make the -mouth long and narrow, with a channel at either end. The outer lip is -also thickened and bent inward, and there is no operculum. - -The animal itself is particularly interesting, for, as it creeps along -on its broad foot, abruptly shortened in the front, the mantle lobes -bend over the top, meeting along the middle line, where they are usually -fringed with little tentacle-like processes; and, as a result, the whole -shell is beautifully enamelled on the outer surface. In all the Cowries -the central teeth are single, and the laterals are arranged either in -twos or threes. - -Perhaps the commonest representative of this family is the pretty little -_Cypræa_ (_Trivia_) _europæa_ (Plate V.), the shells of which are -sometimes washed up in large numbers on sandy beaches. The animal lives -mainly below low-water level, but it may often be found in the larger -rock pools, creeping rapidly over the tangles, and may be easily secured -with the aid of a net. - -In the same family we have the little _Erato_ (_Marginella_) _lævis_, -the white shell of which is minutely furrowed along the lips; and also -_Ovulum patulum_ (_Calpurna patula_), so called on account of its -fancied resemblance to a poached egg. - -We have also several species of Cone shells (family _Conidæ_) on our -coasts, readily recognised by their form, which is a cone, with a long, -narrow aperture, partially closed by a minute operculum. As in the last -family, the foot is abruptly shortened in front. The head is very -prominent, with eyes situated on the tentacles. There are two gills, and -the teeth are arranged in pairs. - - [Illustration: FIG. 179.--1. _Ovulum patulum._ 2. _Erato lævis_] - - [Illustration: FIG. 180.--_Mangelia septangularis_ AND _Mangelia - turricula_] - -The Conidæ are principally inhabitants of tropical seas, where some very -large species exist. Two of the British representatives, both common -shells, are shown in fig. 180. - -Our next family (_Buccinidæ_) is so well distributed on our coasts, that -it would be difficult, we imagine, to find a spot quite free from its -familiar forms. It contains all those creatures commonly known as -Whelks, Dog Whelks, and Dog Winkles, ranging from deep water almost to -high-water mark. - -In all these the shell is notched in front, or the canal is turned -abruptly upward. The foot of the animal is broad, the eyes are situated -either on the tentacles or at their bases, and there are two gill -plumes. - -All the species are carnivorous, and some are said to be very -destructive to mussels and young oysters. - -The Common Whelk (_Buccinum undatum_, Plate V.) lives in deep water, -whence it is dredged up largely for the market. Its clusters of egg -cases are washed up in large numbers on the beach, where they form one -of the commonest materials among the refuse at high-water mark. It is -not uncommon, also, especially after storms, to find the unhatched eggs -stranded by the waves, and these are so transparent that the embryos, -several in each capsule, may be seen within. The hole through which the -young escape may also be seen on the inner side. - - [Illustration: FIG. 181.--1. _Purpura lapillus._ 2. EGG CASES OF - _Purpura_. 3. _Nassa reticulata_] - -The Dog Periwinkle (_Purpura lapillus_) abounds on all our coasts and is -remarkable for the production of a dull crimson or purple fluid that may -be obtained from it by pressing on the operculum. This fluid turns to a -brighter colour on exposure to air, and is said to have been used -largely in former times as a dye. It will be seen from our figure that -the spire of this shell is shorter in proportion than that of -_Buccinum_; but both are alike in that the operculum is made up of -layers with a nucleus on the external edge. - -The other species figured is _Nassa reticulata_, popularly known as the -Dog Whelk, and characterised by a tooth-like projection of the inner lip -close to the anterior canal. It is very common near low-water mark, -where it may be seen crawling over the rocks on its broad foot, from -which project two hornlike appendages in front and two narrow tails -behind. - - [Illustration: FIG. 182.--_Murex erinaceus_] - -From the last family of the gasteropods (the _Muricidæ_) we select two -common species--_Murex erinaceus_ and _Fusus antiquus_ (Plate V.). In -both these the anterior canal of the shell is straight and the posterior -wanting. The eyes are on the tentacles, and there are two plumed gills. -Both are carnivorous species, feeding on other molluscs; and the former -is said to bore through the shells of its prey with the prominent beak -of its shell. - -_Murex_ may be readily distinguished by the prominent longitudinal -ridges of the thick shell, its rounded aperture, and by the partly -closed canal running through the beak. It is known to fishermen as the -Sting Winkle; the other species is called the Red Whelk in some parts, -and in Scotland is known as the Buckie. Like the common whelk, it is -dredged largely for the market, and is said to be far more esteemed than -the former, from which it may be distinguished by the fusiform shape of -the shell and the long straight canal. - -We now pass to the last and highest class of the mollusca, called the -_Cephalopoda_ because they have a number of arms attached to the head, -round the mouth. Unlike the majority of molluscs they are bilaterally -symmetrical: and are much more highly organised, in some respects even -making an approach to the vertebrates. Thus they generally have an -internal hard structure, either horny or calcareous in structure, -representing the vertebral column, and the circulatory system consists -of arteries and veins, connected by minute capillaries. The corpuscles -of the blood are also similar in form to those of the vertebrates. -Externally they are all naked, with the exception of the nautilus and -argonaut of the warmer seas. - -The arms, so characteristic of the class, are eight or ten in number, -long and muscular, and provided with numerous suckers by which the -animal can cling with remarkable tenacity. These suckers are situated on -the inner surface of the arms, and the disc of each one displays a -series of muscular fibres, all converging from the circumference towards -the centre, which is occupied by a softer structure that works inwards -and outwards like the piston of a pump. Thus the suckers form a system -of exhausting air-pumps by which a vacuum can be produced, and the -tenacity of the grip, maintained by atmospheric pressure, is so great -that the arms, strong as they are, may be torn asunder by attempting to -pull them from their hold; and yet the animal can release its grip with -the greatest of ease by simply releasing the pistons of its pumps. - -The cephalopods are further distinguished by their very large, glaring -eyes, situated on the sides of the well-formed head, and by powerful -jaws that work in a vertical plane, like those of the vertebrates, but -somewhat resembling the beaks of certain birds. The tongue is also very -large and fleshy, and in part armed with numerous hooked spines or -teeth. - -The class is usually divided into two orders, one characterised by the -possession of two gills, and the other of four; but the British species -belong to the former, known technically as the _Dibranchiata_. This -order is subdivided into two sections according to the number of arms; -and the divisions are called the _Octopoda_ and _Decapoda_ respectively. - - [Illustration: FIG. 183.--OCTOPUS] - -The former section includes the Octopods, of which some species inhabit -our seas. They all have eight arms, of unequal size, with the suckers -arranged in two rows, and their round or oval bodies seldom have any -fins, locomotion being effected by means of the arms, and by the sudden -expulsion of water from the siphon. The shell is rudimentary, being -represented merely by two short 'styles' within the mantle. The species -vary considerably in size, some being only about an inch long when fully -grown, while others measure two feet or more, and are looked upon as -formidable creatures by man. Sometimes they are washed up on our -beaches, but the best way to make their acquaintance is to examine the -contents of the fishermen's drag nets as they are hauled on the beach. - -In the same manner we may secure various species of the Decapods or -Ten-footed Cephalopods, which comprise the Calamaries, Squids, and -Cuttlefishes. These, too, properly speaking, have but eight arms, the -other two appendages being really tentacles, which are usually longer -than the arms, and more or less retractile; they are also expanded at -the ends. The decapods are also to be distinguished from the octopods -by their elongated bodies, and a flattened, fin-like appendage on either -side. Their eyes, also, are capable of being rotated within the orbits, -while those of the octopods are fixed; and the shell consists of one or -more horny 'pens,' or of a calcareous 'bone,' contained in a cavity so -loosely that it drops out of its place when the cavity is opened. - - [Illustration: FIG. 184.--_Loligo vulgaris_ AND ITS PEN] - - [Illustration: FIG. 185.--_Sepiola atlantica_] - -The Common Calamary (_Loligo vulgaris_) may be recognised by the -accompanying illustration, from which it will be observed that the body -tapers behind, bearing two rhomboidal fins in the rear. The suckers are -arranged in two rows on the arms, but in fours on the expanded tips of -the tentacles. The animal is a good swimmer, and sometimes crawls, head -downwards, on the disc surrounding the mouth, pulling itself along by -means of its arms. Its shell is a horny pen, lanceolate in form, but it -divides as the age of the animal advances, so that two or more may be -found in the same specimen. - -Belonging to the same family we have the Common Squid (_Sepiola -atlantica_), also a very abundant species. Here the body is shorter and -purse-like, and the fins are dorsal and rounded. It seldom exceeds four -or five inches in length, and, like the Calamary, is used largely as a -bait by fishermen. - -Another family--the _Sepiadæ_--contains the Cuttlefish (_Sepia -officinalis_), the 'bone' of which is such a common object on the beach. -This latter is a broad, curved plate of carbonate of lime, made up of a -number of regular layers, and having a cavity hollowed out at the -posterior end. It is exceedingly light and porous in structure, and at -one time was used largely as an antacid as well as a dentifrice. It is -also proportionately large, being both as long and as broad as the body -of the animal. - - [Illustration: FIG. 186.--_Sepia officinalis_ AND ITS 'BONE'] - -Cuttlefishes live principally in the shallow water close to shore, where -they swim backwards by the sudden propulsion of water from their -siphons; and their eggs, which look like clusters of black grapes, are -frequently thrown up on the beach, generally attached to the stems and -fronds of sea weeds. - -As a rule the cephalopods swim slowly by the aid of their fins or by a -rhythmic contraction by which water is expelled from their siphons, but -when in danger the muscular contraction is so violent that they dart -through the water with great speed, and even leap into the air to avoid -their enemies. But they have another and much more remarkable way of -escaping from their foes:--They possess a gland, the duct of which opens -into the base of the funnel or siphon, that prepares an inky fluid; and -when the animal is disturbed it suddenly ejects this fluid, rendering -the surrounding water so cloudy that it is often enabled to retreat -unobserved. The 'ink' of the _Sepia_ was used for writing in former -times, and is still employed in the preparation of the artist's pigment -that bears the same name. Fishermen are well acquainted with this -peculiar characteristic of the animal, for they are frequently -bespattered with the contents of the ink bag of the _Sepia_ when the -creature is included in the contents of their draw-nets, and have learnt -to handle it cautiously until the objectionable fluid has been all -discharged. - - [Illustration: FIG. 187.--EGGS OF _Sepia_] - -We will conclude this chapter by giving a tabular summary of the -classification of the molluscs which will probably be useful to the -collector of marine objects. - - - CLASSIFICATION OF THE MOLLUSCA - - Class =LAMELLIBRANCHIATA=--Plate-gilled. Headless, usually enclosed - in bivalve shell. - Section =SIPHONIDA=--Mantle lobes more or less united to form - tubular siphons. - Families--_Pholadidæ_, _Gastrochænidæ_, _Anatinidæ_, - _Myacidæ_, _Solenidæ_, _Tellinidæ_, _Mactridæ_, - _Veneridæ_, _Cyprinidæ_, _Lucinidæ_, _Cardiadæ_, &c. - Section =ASIPHONIDA=--Mantle lobes free or nearly so. No true - siphons. - Families--_Arcadæ_, _Mytilidæ_, _Aviculidæ_, _Ostreidæ_, - &c. - - Class =CEPHALOPHORA=--Head-bearing. Usually enclosed in a univalve - shell. - Section =PTEROPODA=--Wing-footed molluscs. - Section =GASTEROPODA=--Stomach-footed molluscs. - Order =Nucleobranchiata=--Viscera form a nucleus on the back. - Order =Opisthobranchiata=--Shell generally absent. Gills more - or less exposed. - Section NUDIBRANCHIATA--Naked gills. - Section TECTIBRANCHIATA--Gills covered by shell or mantle. - Order =Pulmonifera=--Lung-breathers. Terrestrial. - Order =Prosobranchiata=. - Section HOLOSTOMATA--Aperture of shell entire (sea snails). - Families--_Chitonidæ_, _Dentaliadæ_, _Patellidæ_, - _Calyptræidæ_, _Fissurellidæ_, _Haliotidæ_, - _Turbinidæ_, _Littorinidæ_, _Turritellidæ_, - _Cerithiadæ_, _Pyramidellidæ_, _Naticidæ_, &c. - Section SIPHONOSTOMATA--Possess a true siphon. Carnivorous. - Families--_Cypræidæ_, _Conidæ_, _Buccinidæ_, _Muricidæ_, - &c. - - Class =CEPHALOPODA=--Sucker-bearing arms round the mouth. - Order =Dibranchiata=--Two gills. - Section OCTOPODA--Eight arms. - Families--_Argonautidæ_, _Octopodidæ_. - Section DECAPODA. - Families--_Teuthidæ_ (Calamaries, Squids), _Sepiadæ_, &c. - Order =Tetrabranchiata=--Four gills (containing _Nautilidæ_). - - - - - CHAPTER XIII - - _MARINE ARTHROPODS_ - - -The sub-kingdom _Arthropoda_ contains a vast assemblage of animals, all -of which, as the name implies, possess jointed appendages. Their bodies -are covered with a skin that is hardened by a horny substance -(_chitin_), and frequently, also, by the deposit of carbonate of lime. - -The body of Arthropods is made up of a chain of segments, all of which -are built up on one common pattern, and each one is surrounded by a ring -of the hardened skin or exo-skeleton that gives attachment to a pair of -appendages. Commonly, however, two or more of the segments become fused -together, being covered by a continuous plate or shield, in which the -boundaries of the rings are almost or completely obliterated; but in -such cases the appendages they bear always remain distinct, so that the -true number of segments is always apparent. The skin between those -segments that are not so fused together remains soft and flexible, thus -allowing the body to be freely bent. - -The appendages exhibit a great variety of structure, and are as varied -in their functions. Some are used as feelers, and others as jaws for -seizing or masticating food. Some are developed into powerful seizing -organs for purposes of defence or attack, some into paddles for -swimming, while others are legs adapted for walking. - -All these appendages are made up of segments, each of which, like those -of the body itself, is surrounded by a ring of hardened skin, and -connected with its neighbours by a flexible integument that allows -perfect freedom of movement; while within are the muscles, often very -powerful, by which the appendage is moved. - -In the arthropods we have a sub-kingdom of highly organised animals, -with distinct, and often very complicated, systems of organs for -digestion, circulation, and respiration; and the nervous system consists -of a well-developed chain of ganglia, connected by nerve cords, and from -which nerve fibres are distributed to the various parts of the body. It -should be noted, however, that some members of the group have -degenerated into parasites, and in these, as with all such degraded -creatures, many of the organs have retrogressed to such an extent that -they are quite functionless, or have even disappeared entirely. These -parasitic forms, when very young, are really highly organised creatures, -not unlike the young of their industrious and more noble relatives; but, -as the natural result of their degraded mode of living, in which they -find no use for their organs of locomotion, digestion, circulation and -respiration, these eventually disappear, with the result that the organs -of reproduction predominate to such an extent that they often fill the -greater part of the cavity of the body. - -It should be noted, too, that the sense organs of arthropods are well -developed, most of them being supplied with complex eyes, hearing -organs, and highly sensitive feelers. - -This sub-kingdom consists of four classes--the _Crustacea_, including -lobsters, crabs, shrimps, prawns, &c.; _Arachnoidea_, containing -spiders, mites, and scorpions; _Myriopoda_--centipedes and millepedes; -and _Insecta_. - - [Illustration: FIG. 188.--THE NERVE-CHAIN OF AN ARTHROPOD (LOBSTER) - _o_, optic nerve; _c_, cerebral ganglion; _i_, large ganglion - behind the oesophagus; _th_, ganglia of the thorax; _ab_, ganglia - of the abdomen] - -The first of these classes consists mainly of marine animals, and will -therefore occupy much of our attention, but the members of the other -three are mostly terrestrial and aërial creatures that do not fall -within the scope of this work, except in the case of a few species that -are more or less decidedly marine in their tendencies. The aquatic -members are generally provided with well-formed gills by means of which -they are enabled to extract the dissolved oxygen from the water in which -they live, while those of terrestrial and aërial habits breathe by means -of a system of tracheæ or air-tubes that are open to the air and supply -branches to all parts of the body. - -The _Crustaceans_ are mostly gill-breathers, though some of the aquatic -species have no special organs for respiration, but obtain the oxygen -necessary for respiration by absorption through their thin, soft skin, -while the terrestrial species breathe by means of tracheæ, as we have -just observed. - -Most of them are covered with a calcified skin, as in the case of crabs -and lobsters; but many are protected with a chitinous or horny covering -such as we observe in shrimps and prawns. In either instance the -hardened integument constitutes what is known as the _exo-skeleton_. -None of the crustaceans have an internal skeleton of any kind, though -some of the inner parts are supported by extensions of the hard skin -that penetrate into the body. - -It will be readily understood from the nature of the exo-skeleton of the -crustacean, and especially of the more or less rigid calcareous covering -of the crab and the lobster, that a uniform growth of the body is -absolutely impossible, and, in fact, that an increase in size cannot -take place without an occasional casting of the hard coat of mail. Hence -we find most crustaceans throwing off their coverings at intervals, and -growing by fits and starts during the periods between the 'moultings' -and the hardening of the newly exposed skin. - -When a crab or a lobster is about to undergo the process of moulting, it -retires to a secluded niche in the rock, where it is not so easily found -by its numerous enemies--a necessary precaution, since the creature in -its soft or unarmoured condition is eagerly devoured by fishes and other -marine animals--and there awaits the first stage of the ordeal. -Presently the skin splits; and, after a time, the crustacean succeeds in -extricating itself from its shell, which is cast off in a perfect -condition, every joint being entire, even to the coverings of the -antennæ, the stalked eyes, and other delicate appendages. And not only -this, for the portions of the shell that penetrate inward into the body -are also discarded, as well as the linings of the stomach and the gills; -and these cast-off coats of crabs and lobsters--especially the -former--may often be found in the most perfect condition on the sea -shore, being washed up without injury on the sandy beach, or found in -the very niche in which the creature changed its attire. - -If one examines the powerful pincers of a crab or lobster, a thin plate -of considerable size will be seen to extend within from the movable -'jaw' to give attachment to the muscles by which it is moved, and it -seems impossible that this can be removed with the cast skin without -considerable injury to the new claw that is already formed, though as -yet in a soft condition, within the old and hard one. But it has been -observed that this plate actually cuts through the new claw, and that -the claw thus divided almost immediately closes up and unites again. - -The moulting process being over, the crustacean's body extends itself -within the new, yielding skin; and, the latter becoming gradually hard -by the deposition of carbonate of lime, the creature is able, after a -period of rest, to roam at large again, without much fear of injury, -until the time for the next moulting has arrived. - -Those who have made but a slight acquaintance with the common -crustaceans of our shores must have noted the frequency with which -imperfect specimens occur--specimens with missing appendages, or with a -well-formed limb on one side of the body opposed to a puny and almost -useless fellow on the opposite side. As to the loss of appendages, this -matter will be readily understood by those who have watched crustaceans, -and especially crabs and lobsters, in their native element, so often do -these pugnacious creatures become engaged in furious broils with their -neighbours. And, when we are at work at the collection of various -species on the sea shore, how often do we find that a creature escapes -from our grip by leaving us in possession of a severed limb, while the -owner retreats rapidly among the stones and weeds apparently none the -worse for its trifling loss! This is, in fact, a very common method of -securing its escape from an enemy; and it appears that many crustaceans -have the power of thus rendering a seized limb so brittle that it may be -snapped off with the greatest of ease. - -We have spoken of the loss thus sustained as a trifling one; and so it -is, for crustaceans have the faculty of reproducing lost appendages; and -though the loss may be one of considerable inconvenience at first, a new -limb eventually appears in the place of each one so willingly discarded. - -When such mutilations occur, it will be observed that the severed limb -invariably breaks away at the end of the first or basal joint--a point -where the bloodvessels are so narrow and contractile that but little -loss of blood takes place when the rupture is made--and it has been said -that the animal would soon bleed to death if the fracture were to take -place at any other point. As it is, the wound soon heals, but no trace -of a new limb is to be seen, at least without dissection, until the time -of the next moult. The part is developing, however, beneath the cover of -the basal joint; and when the moulting period arrives, the new limb, -still very small, is exposed to view. It then rapidly enlarges, though -not to anything like its proper size, and its surrounding skin becomes -hardened by the deposit of the calcareous secretion simultaneously with -that of the rest of the body. Further enlargements of the new appendage -take place at subsequent moults, with the final result that it is but -slightly inferior to its fellow either in size or in power. - -The eye of a crustacean is a very complicated structure, commonly -described as a compound eye. It consists of a large number of conical, -radiating, crystalline rods, collected together into a mass that -presents a convex outer surface. This surface is covered with a -transparent layer of chitin which naturally presents a more or less -distinct netted appearance, the bases of the rods being in contact with -its inner surface, and visible through it. Each rod is surrounded by a -layer of pigment that prevents light from passing from one to another, -and the optic nerve passing into the base of the compound structure -sends a sensitive filament into each one. - - [Illustration: FIG. 189.--SECTION THROUGH THE COMPOUND EYE OF AN - ARTHROPOD] - -In many crustaceans this compound eye is situated on the end of a -movable stalk that generally allows it to be protruded or drawn under -cover as occasion requires, but in others the organ does not project -beyond the general surface of the body. Thus we hear of the animals of -this class being divided into the _stalk-eyed_ and the _sessile-eyed_ -groups; the former being represented by crabs, lobsters, shrimps, &c.; -and the latter by sandhoppers and sandborers. - -Crustaceans undergo metamorphoses while very young, the body being -altered considerably in form at several successive moults. Some, in -their earliest stage, consist of a little oval body that shows no signs -of a division into segments. It swims about by means of three pairs of -appendages, and has only one eye. Others start life with four pairs of -limbs, attached to the front portion of the body, a segmented abdomen, -as yet perfectly limbless, and a pair of compound eyes. Then as the -successive moultings take place, new segments and new appendages are -developed, until, at last, the form of the adult is assumed. The -accompanying illustration shows four stages in the development of the -Common Shore Crab. - - [Illustration: FIG. 190.--FOUR STAGES IN THE DEVELOPMENT OF THE COMMON - SHORE CRAB] - -The lowest division of the crustaceans contains the _Cirripedia_ or -Curl-footed crustaceans, which includes the Barnacles that are so -frequently seen attached to the bottom of ships and of floating timber, -and the Acorn Barnacles, the conical shells of which often completely -cover large masses of rock on our shores. - - [Illustration: FIG. 191. THE BARNACLE] - -For some time naturalists could not agree as to the proper place of -these animals in the scale of life, but the matter was finally settled -when some minute creatures only about a twelfth of an inch in length, -and closely resembling the early stages of certain crustaceans, were -seen to undergo metamorphoses, and finally develop into acorn barnacles. -Their position in the animal kingdom was thus determined by their early -stages; but these, instead of changing into a segmented and highly -organised creature like the typical crustacean, lose some of their -appendages, cease to be free-moving animals, and attach themselves to -floating bodies by which they are carried about. Thus they are enabled -to find the food they can no longer seek without such aid. In their -young state they possess not only the means of freely moving in search -of their food, but have organs of vision to aid them in the capture of -their prey. As they grow, however, the foremost appendages are -transformed into a sucking-disc, and the eyes, no longer necessary, -disappear. It will thus be seen that the degenerated adult--the product -of a _retrograde development_--is attached by what was originally the -front of its body, while the abdomen is undeveloped, and the thorax, -with its appendages, forms the summit of the free extremity. - - [Illustration: FIG. 192.--FOUR STAGES IN THE DEVELOPMENT OF THE ACORN - BARNACLE - A, newly hatched larva; B, larva after second moult; C, side view - of same; D, stage immediately preceding loss of activity; - _a_, stomach; _b_, base of future attachment. All magnified] - -Some of the Cirripedes attach themselves to the bodies of whales and -other marine animals. The majority of these are -pseudo-parasites--creatures that live on the bodies of other animals, -but do not derive their food at the expense of their hosts; others, -however, are true parasites, subsisting on the nourishing juices they -extract from the animals to which they are attached. - - [Illustration: FIG. 193.--A CLUSTER OF ACORN SHELLS] - -The Acorn Barnacles, so numerous on our shores, are good types of the -_Cirripedia_, and they are so easily kept alive in the indoor aquarium -that their interesting movements may be well observed. A cluster of -these animals may be obtained by chipping off a piece of the rock on -which they grow; or, instead of this, a few minutes' searching on a -rocky coast at low tide will certainly provide us with a stone of -suitable size, or the shell of a mollusc, on which the creatures have -found a home. - - [Illustration: FIG. 194.--SHELL OF ACORN BARNACLE (_Balanus_)] - -Place them in the indoor aquarium, or in any shallow vessel containing -just sufficient sea-water to cover them, and carry out your -observations with the aid of a hand lens. They will soon open the inner -cone of their many-valved shell, and slowly protrude six pairs of -gracefully curved and delicately-feathered appendages which, as -previously stated, are attached to the thoracic portion of the body. -Then, with a much more rapid movement, the appendages will be withdrawn, -and the shell closed. These alternate movements are continued -incessantly, and are the means by which the animals provide themselves -with both food and air. The reader should also obtain some specimens of -the larger species for the examination of the shell, the structure of -which is interesting and, of course, peculiar to this order. - - [Illustration: FIG. 195.--THE ACORN BARNACLE (_Balanus porcatus_) WITH - APPENDAGES PROTRUDED] - -In general structure and habits Barnacles are very similar to the acorn -barnacles, except that the body is supported on a tough stalk, which, as -we have already stated, is the modified anterior portion of the animal. -These animals also may be easily kept alive and examined in the indoor -aquarium. They are not creatures of the sea shore, but may often be -obtained on masses of timber that have been washed ashore, or from the -bottoms of ships that have been placed in the dry dock for repairs. - -Another order of the crustaceans--the _Copepoda_, or oar-footed -group--is so called on account of the bristled feet that are employed -after the manner of oars when the creatures are swimming. - -These Copepods are small animals, so small indeed that the compound -microscope is generally necessary merely for the examination of their -external characters. Many species inhabit fresh water, and the study of -the group is more commonly pursued by the investigator of fresh-water -pond life than by the sea-side naturalist. However, marine species are -abundant, and may be captured in the open water or in rock pools by -means of a muslin net. As with the last order, some degenerate from the -comparatively complicated free-swimming and eyed larval state to blind -and limbless parasites that feed on the bodies of fishes and are known -as fish lice. - -The body of the typical copepod is distinctly segmented, and the head -and thorax are both enclosed in a hardened buckler. It has two pairs of -antennæ, two pairs of foot jaws by which it captures its prey, and four -or five pairs of bristled feet for swimming. The jointed abdomen has -also a tuft of bristles at its extremity. The annexed illustration -represents some marine species, and will serve to show the general -features of the order. - - [Illustration: FIG. 196.--A GROUP OF MARINE COPEPODS, MAGNIFIED] - -The sea-side naturalist, intent on the collection of small life, may -possibly meet with representatives of two other orders of -crustaceans--the _Ostracoda_ or shelled crustaceans, the bodies of which -are enclosed in a bivalve, hinged shell; and the _Branchiopoda_, so -called because the branchiæ or gills are attached to the feet. - - [Illustration: FIG. 197.--A GROUP OF OSTRACODE SHELLS] - -The Ostracodes have two or three pairs of feet which subserve -locomotion, but are not adapted for swimming; and two pairs of antennæ, -one of which assists in locomotion. The mouth is provided with organs of -mastication, the branchiæ are attached to the hind jaws, and the -animals have but one eye. Some of these crustaceans inhabit deep water -only, while others live in sand between the tide-marks; but several -species, belonging chiefly to the genus _Cythere_, abound in rock pools, -where they may be readily obtained by scraping the confervæ and -corallines with a small muslin net. - -The branchiopods are free swimmers, and are protected by a buckler-like -envelope. Most of them are inhabitants of fresh water, and are popularly -known as water fleas. We have figured one marine species, belonging to -the genus _Evadne_, which has a colourless body, and a single -conspicuous black eye, and is interesting as being the food of the -herring. - - [Illustration: FIG. 198.--_Evadne_] - -The four orders of crustaceans that have been briefly described belong -to the division _Entomostraca_, which signifies 'shelled insects.' This -term is not a happy one when judged from the standpoint of our present -knowledge of animal life, but it must be remembered that, at the time it -was applied (1785), spiders and crustaceans were all included in the -same class as the insects; and this is hardly surprising when we observe -the close relationship of these animals, as shown in their segmented -bodies and jointed appendages; for, as we have already shown, the lowly -organised parasitic crustaceans which, in the adult state, lose most of -their appendages and cease to be distinctly segmented, are more or less -insect-like in their larval and free-swimming stage. - -All the other crustaceans are included under the term _Malacostraca_, or -soft shelled, since, although many of them are protected by an -exo-skeleton that is hardened by the deposit of carbonate of lime, yet, -generally speaking, their coverings are softer than those of the -molluscs; and therefore the term _Malacostraca_ was originally applied -by Aristotle in order to distinguish them from the animals that are -covered by harder and thicker shells. - -This division of the crustaceans contains wood lice, sandhoppers, -lobsters, shrimps, crabs, &c., and consists of two main groups--the -Sessile-eyed (_Edriophthalmata_) and the Stalk-eyed (_Podophthalmata_) -crustaceans. - -We shall now consider the Sessile-eyed group, dealing first with the -order _Isopoda_ or equal legged, and then the _Amphipoda_, which have -appendages adapted both for walking and swimming. - -The general nature of an Isopod may be readily understood by the -examination of the common woodlouse that abounds in gardens and damp -places almost everywhere, and the reader will probably remember having -seen similar creatures crawling over the rocks on the sea shore. - -The body is generally depressed or flattened, but convex above, and is -composed of seven segments, each segment bearing a pair of legs which -terminate in a pointed claw, while the posterior appendages are modified -into flat, leaf-like organs of respiration. - - [Illustration: FIG. 199.--MARINE ISOPOD - 1. _Sphæroma serratum._ 2. _Limnoria lignorum._ 3. _Ligia - oceanica._ 4. _Nesæa bidentata._ 5. _Oniscoda maculosa_] - -When engaged in 'shrimping' one frequently meets with shrimps or prawns -that are disfigured by a tumourous swelling on the side of the body, and -if the swelling be opened a little parasite will be dislodged. This -parasite is an Isopod (_Bopyrus_), the appendages of which are -imperfectly developed. The female is very much larger than the male, -and, as is usual with parasitic creatures, the greater part of the -body-cavity is occupied by the well-developed organs of reproduction. - -There are several other parasitic isopods, some of which live on the -bodies of fishes, and are popularly known as fish-lice, but these are -not so likely to come in the way of the sea-side naturalist as the more -typical forms that crawl about on the rocks and among the weeds of the -coast. A few of the latter are shown in the accompanying illustration, -including the Sea Pill-ball (_Nesæa bidentata_), common on the rocky -coasts of the south-west, and distinguished by the two sharp -projections on the last segment; the Serrated Pill-ball (_Sphæroma -serratum_), very common on most rocky shores, and characterised by the -fine sawlike teeth on the outer edge of the outer plates of the 'tail'; -the Great Sea-slater (_Ligia oceanica_), also an abundant species; the -Spotted Hog Louse (_Oniscoda maculosa_) that lives among the tufted sea -weeds; and the Boring Pill-ball (_Limnoria lignorum_) that bores into -the woodwork of piers and jetties, often doing considerable damage. - - [Illustration: FIG. 200.--MARINE AMPHIPODS - 1. The spined sea screw (_Dexamine spinosa_). 2. _Westwoodia - coecula._ 3. _Tetromatus typicus._ 4. The sandhopper (_Orchestia - littorea_). 5. _Montagua monoculoides._ 6. _Iphimedia obesa._ All - enlarged] - -The above and other isopods feed on various animal and vegetable -substances, some species being quite omnivorous in habit. Most of them -are eagerly devoured by birds and fishes. - -The Amphipods, six species of which are shown in the above illustration, -include the Sandhoppers or Beach Fleas, so numerous on our coasts that -it is almost impossible to go any distance without making their -acquaintance. They are invaluable as scavengers, as they rapidly devour -decaying sea weeds, and will speedily reduce the body of any animal -washed on the beach to a clean skeleton. Although they are all small -creatures, they make up in numbers for any deficiency in size; and -though devoured in enormous quantities by the various shore birds, they -multiply so prodigiously that they are never lacking wherever there is -decomposing organic matter to be consumed. - -The bodies of these animals are usually flattened from side to side, -very distinctly segmented, and have a well-developed abdomen. The head -is furnished with two pairs of antennæ and a pair of sessile eyes, -though some species possess only one pair of antennæ, while others have -four eyes. The limbs of the thorax are used either for walking or for -swimming, and give attachment to the gills. The abdomen has generally -six pairs of appendages, the foremost three pairs of which are usually -small, and employed in swimming, while the others are stronger and -directed backwards, and are often adapted for jumping. - -It is very interesting to observe the habits of the Sandhoppers and -other Amphipods both on the sandy beach and in the water, and the -student will find that certain species burrow into the sand with -considerable agility, and live principally at the extreme high-water -mark, where they feed on the organic matter washed in by the breakers at -each high tide, while others dwell almost exclusively in the water, -among weeds and stones, and should be searched for at low water. The -latter may be kept alive for some time in the aquarium providing they -are the only occupants, but a little experience will show that these and -all other Amphipods are readily devoured by many marine creatures, and -consequently they are of real value to the aquarium keeper as food for -other animals. - -We now come to the Stalk-eyed Crustaceans (_Podophthalmata_), which -contain those members of the class most generally known, such as crabs, -lobsters, shrimps, and prawns. In these the eyes are mounted on movable -pedicels, the head and thorax are generally covered by a large shield -called the carapace, and the appendages are adapted partly for seizing -and masticating, and partly for locomotion. - -The group includes two orders--the _Stomapoda_ or Mouth-footed -crustaceans, so called because some of the limbs are crowded round the -region of the mouth; and the _Decapoda_, or Ten-footed crustaceans. - -The Stomapods, though very abundant in tropical seas, are not often met -with on our own shores. However, since a few interesting species are -inhabitants of our seas we will briefly describe the distinguishing -characteristics of the group. - -We have just mentioned the fact that the head and thorax of a decapod is -usually covered by a large shield--the carapace. Now, the general -character of this carapace may be seen at once in either the shrimp or -the lobster. In these animals the segments that form the head and the -thorax are all fused together, and are completely covered by the -protective buckler of hardened skin; but in the Stomapoda the carapace -is much smaller in proportion, and a few of the segments of the thorax, -instead of being fused into the general mass of the _cephalo-thorax_, -are quite distinct from it. The abdomen, also, is large and strongly -formed in these animals. Five pairs of the thoracic limbs are directed -forwards, and are adapted both for catching food and for climbing, while -others are used in walking. The limbs of the abdomen generally number -six pairs, of which the first five bear feathery gills. - - [Illustration: FIG. 201.--THE MANTIS SHRIMP (_Squilla Mantis_)] - -Two species of Mantis Shrimps, one of which is represented in fig. 201, -have been found off the south and south-west coasts, but these are not -likely to be seen on the shore, since they inhabit deep water. Allied to -these, and sometimes included with the Stomapods, are the Opossum -shrimps, so called because the females of some species carry their eggs -in a kind of pouch, thus reminding us of the marsupial quadrupeds of the -same name. They are of very slender build compared with the mantis -shrimps, and differ from them in that the carapace completely covers the -thorax; but though this is the case, the fusion of the thoracic segments -is not complete, since the posterior ones have still a certain amount of -freedom of movement. Some species of opossum shrimps are abundant in the -rock pools of our coasts, particularly in the south-west, but their -bodies being often so transparent as to be almost invisible, they are -consequently easily overlooked. Their general appearance may be -gathered from our illustration of _Mysis chamæleon_, which is probably -the most common species inhabiting our coast. - -The highest crustaceans--the Decapods--are divided into two -sub-orders--the _Macrura_, or Great-tailed, including lobsters, shrimps, -&c.; and the _Brachyura_ (Short-tailed), containing the crabs; but the -number of British species is so large that it is impossible to give, in -our limited space, a detailed description of all the commonest even. All -we can do is to note a few of the more interesting features of certain -species, to introduce such illustrations as will enable the young -naturalist to identify a number of the commoner ones, and to give the -general characteristics of the main divisions so that the student may be -able to classify his specimens intelligently. - - [Illustration: FIG. 202.--THE OPOSSUM SHRIMP (_Mysis chamæleon_)] - -In the _Macrura_, as with other divisions of the crustaceans, we meet -with very interesting modifications of the appendages, adapted to quite -a variety of uses; and if the reader is unacquainted with these -adaptations of structure to habit he cannot do better than secure a -lobster or crayfish for study. It will be observed that the body may be -divided into two main portions--the _cephalothorax_, consisting of head -and thorax combined, and the _abdomen_. The former is composed of -fourteen segments, so thoroughly fused together that they are denoted -only by the fourteen pairs of appendages to which they give attachment, -while the calcified skin forms one continuous shield surrounding the -whole. The abdomen, on the other hand, consists of six distinct -segments, each of which is surrounded by its own ring of the hardened -integument, and is connected with its neighbours by means of a portion -of uncalcified skin that renders the whole very flexible. A groove in -the front portion of the great shield (_carapace_) marks the division -between the head and the thorax, the former composed of six, and the -latter of eight united segments. - - [Illustration: FIG. 203.--PARTS OF LOBSTER'S SHELL, SEPARATED, AND - VIEWED FROM ABOVE] - -The calcareous covering of each segment consists of an upper portion, -called the _tergum_, and a lower, named the _sternum_, united at the -sides; the sternal portion of the cephalothorax, which gives attachment -to the walking limbs, is a most complicated and beautifully formed -structure. - - [Illustration: FIG. 204.--A SEGMENT OF THE ABDOMEN OF A LOBSTER - _t_, tergum; _s_, sternum, bearing a pair of swimmerets; _h_, - bloodvessel; _d_, digestive tube; _n_, nerve chain] - -The six pairs of appendages belonging to the head are easily made out -with a little care. The first are the jointed _eye-stalks_ that bear the -compound eyes previously described; and these are followed by two pairs -of _antennæ_, or feelers, the first being shorter and double, while the -second are very long. The former contain the organs of hearing. Then, in -front of the mouth, and completely hiding it, are a pair of strong -_mandibles_ or jaws that move horizontally, and the two pairs of -_maxillæ_ that are also employed in reducing the food. - -Following these, but belonging to the thorax, are three pairs of -appendages that are known as foot-jaws; for, although they assist the -preceding organs in breaking up the food, they bear a resemblance in -some respects to the longer limbs behind them. Of the latter there are -five pairs (hence the term _decapoda_), the first being a very powerful -pair of seizers or pincers, and the remaining four, which are well -adapted for walking, terminating in either double or single claws. - -All the appendages above mentioned are not only attached to the body by -movable joints, but are themselves made up of jointed parts, sometimes a -considerable number, each of which, like the segments of the body -itself, is surrounded by a ring of hardened skin, and connected with -those above and below it by a portion of soft and flexible skin. - - [Illustration: FIG. 205.--APPENDAGES OF A LOBSTER - 1. Second maxilla. 2. Third foot-jaw. 3. Third walking leg. - 4. Fifth walking leg] - -Lastly, beneath the abdomen, are paired limbs called _swimmerets_, which -are used as paddles, and probably assist the animal more or less in its -progress through the water; but the principal organ of locomotion in the -_macrura_ is undoubtedly the powerful muscular abdomen, aided by the -broad and fanlike tail formed by the appendages of the last segment. To -demonstrate this fact, put a live lobster, or even a shrimp, in a still -rock pool, and threaten it from before, when it will rapidly retreat -backwards by a series of powerful jerks, produced by suddenly doubling -its abdomen forwards beneath its body. - -In addition to the external characters above mentioned, there are many -interesting features connected with the internal structure of the -lobster that may be studied on making easy dissections. Thus, the gills, -which are attached to the bases of the thoracic limbs, may be exposed by -cutting away the side of the carapace, and at the same time we may -discover the bailing organ by means of which a current of water is kept -flowing forwards through the gill-cavity to keep up the necessary supply -of oxygen for respiration. The removal of the upper portion of the -carapace will expose the heart and some of the principal bloodvessels, -and also the stomach with its powerful and complicated 'gastric mill,' -formed by the hardening of portions of the wall of the latter organ for -the purpose of crushing and masticating the food. Then, if these organs -be carefully removed from above, together with the others we have not -space to describe, and the powerful muscles that fill up the segments of -the abdomen, the chain of ganglia and their connecting nerve cords that -form the central part of the nervous system may be seen extending along -the central portion of the body. - - [Illustration: FIG. 206.--LONGITUDINAL SECTION OF THE LOBSTER - _a_, antenna; _r_, rostrum or beak; _o_, eye; _m_, mouth; _s_, - stomach; _in_, intestine; _l_, liver; _gl_, gills; _h_, heart; - _g_, genital organ; _ar_, artery; _n_, nerve ganglia] - -Several species of lobsters inhabit our seas, but they are generally to -be found beyond the tide-marks, and are, therefore, not often caught by -sea-side collectors without the aid of some kind of trap or the -assistance of fishermen. The common lobster (_Homarus vulgaris_), -however, is often left behind by the receding tide on our rocky coasts, -and may be seen and caught if one knows where to look and how to -capture. - -On cautiously approaching a deep rock pool one may often see a lobster -rapidly retreat in its usual backward fashion, and snugly house itself -in a narrow chink from which it is impossible to remove it. And, when -once surprised, it is not likely to show itself again as long as the -intruder is in view. - -If one remains perfectly still for a time, a pair of waving antennæ may -be seen gradually protruding from the safe retreat; but, as soon as the -stalked eyes have advanced sufficiently to detect the figure of a -stranger, the lobster silently withdraws itself till quite out of sight. - -Lobsters, usually of rather small size, may often be seen quite out of -the water at low tide, in the narrow chinks of the rock, or under large -stones, but it is no easy matter, as a rule, to get them out. It is of -little use poking a stick into the entrance of their hiding-places, -though occasionally they will grasp the stick so tenaciously with their -forceps that they may be pulled within reach. You _may_ be able to haul -them out by their long antennæ, but if you can find a second way into -their home such that you can disturb them from behind you are pretty -sure of your victim. - - [Illustration: FIG. 207.--THE SPINY LOBSTER (_Palinurus vulgaris_)] - -It will be unnecessary to describe other species of lobsters -individually, but we have introduced figures of a few for -identification. The Norway Lobster (_Nephrops norvegicus_) is often -landed in large numbers by the fishermen of the east and south-east -coasts and sold at a shilling or so a dozen under the name of Norway -Prawns. They are pretty and interesting creatures, and may be easily -kept alive in the indoor aquarium, where they may be fed on any kind of -fish. - - [Illustration: FIG. 208.--THE NORWAY LOBSTER (_Nephrops norvegicus_)] - -Fig. 209 represents the two allied creatures that may sometimes be dug -out of the sandy beach, or from the mud in the estuary of a river. The -one on the left is the mud-borer (_Gebia stellata_), which is of a dull -yellowish colour, marked more or less distinctly by pinkish starlike -spots--a feature that has suggested the specific name. The beak in front -of the carapace is very prominent and spiny, and the long abdomen is -narrower in front than in the middle. This creature hides in the holes -that have been excavated by boring molluscs, and seems also to extend -the cavities it inhabits by its own labours. - -The other is very similar in general form, but has no spiny beak and the -abdomen is much broader in the middle than at the base. It is also to be -distinguished by the very unequal size of its front legs, one of which -is much more developed than the other. - -It is known as the mud-burrower (_Callianassa subterranea_), and is said -to burrow very deeply into mud-banks, scooping out its retreat -principally by means of the second and third pairs of legs. Although -found at times between the tide-marks, its principal habitat is probably -in the mud that is covered by deep water, for it is not uncommonly to be -found in the stomachs of fishes that habitually feed in such localities. - - [Illustration: FIG. 209.--THE MUD-BORER (_Gebia stellata_) (1) AND THE - MUD-BURROWER (_Callianassa subterranea_) (2)] - -Lobsters of all kinds, and, indeed, the marine crustaceans generally, -are essentially the scavengers of the sea, for they are carrion-feeders, -greedily devouring flesh in all stages of decomposition. Hence the value -of their work on the sea shore is very considerable. - -An examination of shrimps and prawns will at once show their close -relationship with lobsters. The general build of their bodies is -practically the same, and their appendages, though often different in -form from the corresponding limbs of the lobster, will be seen to -resemble them closely in arrangement and structure. The exo-skeletons -of these creatures are, however, generally hardened by a horny substance -(_chitin_) instead of a stony deposit of carbonate of lime. - -The shrimps and prawns sold for food in our markets are very similar in -appearance when alive, the leading distinguishing feature being, -perhaps, the presence of a sharp, serrated beak projecting forward from -the front portion of the carapace of the latter. - -The reader is probably acquainted with the fact that the shrimps and -prawns used as food have quite a different appearance when alive and in -their native element to that displayed by the corresponding wares in the -fishmonger's shop--a fact that applies equally well to the edible crabs -and lobsters. Most crustaceans change to a bright red colour when -boiled, and, as stated in a previous chapter, the same result is -produced by the action of strong spirit. - - [Illustration: FIG. 210.--THE COMMON SHRIMP (_Crangon vulgaris_)] - -The Common Shrimp (_Crangon vulgaris_) is an exception, however, for it -may be distinguished when boiled by its dull greyish brown colour. When -alive this species is of a very pale greenish or greyish tint, lightly -spotted with brown; and its habits are so interesting that it will well -repay one to watch it either in the aquarium or in a rock pool. It -frequents sandy coasts, and can hide itself very quickly by burying its -body in the sand, using for this purpose both its legs and its antennæ. - -The Prawn frequents rocky coasts, where it may often be obtained in -large numbers by sweeping with a suitable net under the cover of weeds -and stones. Its body is of an exceedingly pale greenish colour, and so -transparent that it is quite inconspicuous when in the water. Prawns are -turned to a rose-red colour by boiling, and they are captured in large -numbers when young and sold as 'red shrimps.' - - [Illustration: FIG. 211.--THE PRAWN (_Palæmon serratus_)] - -In addition to the common species mentioned there are quite a number of -shrimps and prawns to be found in our seas, but some of them inhabit -deep water and are rarely to be found between the tide-marks. All, -however, are eagerly devoured by fishes, and, on that account, are often -to be obtained in good condition by examining the contents of the -stomachs of freshly caught fishes. In fact, this mode of search for the -smaller species of deep-sea life is not to be despised, for it is a -means by which we can obtain specimens that are not often secured by the -methods coming within the ordinary range of the amateur's work. - -It will be remembered that we spoke of the Decapods as consisting of two -main groups--the Great-tailed (_Macrura_) and the Short-tailed -(_Brachyura_). Frequently, however, we find the order divided into three -sub-orders as follows:-- - - 1. _Macrura_ (Great-tailed), 2. _Anomura_ (Peculiar-tailed), - 3. _Brachyura_ (Short-tailed); - -the first containing lobsters, shrimps, &c.; the third the typical -crabs, such as the shore crab and the edible crab; while in the second -are placed those species of crabs which have been regarded as -intermediate in character. Thus, in the _Anomura_ we find decapods in -which the abdomen, though not so well developed as in the _Macrura_, is -either permanently extended or is capable of being extended and used for -swimming as occasion requires. The hindmost legs, also, are not well -developed and adapted for walking, but are employed only as organs of -prehension; and, as is the case with the first sub-order, there are -often two pairs of well-developed antennæ. - -In this sub-order of 'queer tails' we find the Soldier or Hermit Crabs, -and those flat-bodied crabs that live almost exclusively on the surface -of stones, and are hence known as Stone Crabs; but as opinion now seems -inclined against the formation of a special suborder for these -creatures, we shall briefly deal with them as a first section of the -_Brachyura_. - -The Stone Crabs are extremely interesting creatures, and the observation -of their habits, both in and out of the water, is particularly -entertaining and instructive. One species--the Broad-Clawed Porcelain -Crab (_Porcellana platycheles_), shown on Plate VI.--is very abundant on -all our rocky coasts, and may be found in immense numbers near low-water -mark. - -Turn over some of the large encrusted stones that strew the beach among -the rocks, and you are almost sure to find numbers of these little crabs -clinging to the freshly exposed surface. A few of them may remain -perfectly still, and exhibit no sign of surprise on their untimely -exposure to the light; and these, on account of their small size, the -closeness with which they apply their flattened bodies to the encrusted -stone, and more than all to the protective colouring of their dingy -bodies, which so closely resembles that of the surface to which they -cling, may well be overlooked by the inexperienced collector. But the -majority of them will immediately scamper away in their own peculiar -fashion towards the edge of the stone, and rapidly make their way to -what is now the under side. As they progress with a hasty, sliding -movement they never for one moment loosen their firm hold on the rough -surface of the stone, but keep both body and limbs in close contact with -it, clinging hard by means of their pointed claws as well as by the -numerous hairs and bristles with which their appendages are liberally -fringed. - -Attempt to pull one from its hold, or even take other than the gentlest -means to arrest its progress, and you will probably find that it -suddenly parts company with one of its broad claws in its endeavour to -escape; and, unless some special precautions be taken to remove these -crabs, it is possible that quite half the specimens taken will have been -damaged in this way during their struggles to escape. If, however, you -gently thrust the point of a penknife beneath the body, and then apply -the thumb above, you may lift them from a stone without injury. Another -plan is to press a frond of smooth sea weed as closely as possible to -the surface of the stone in the front of the crabs, and then allow them -to crawl on to it, or cause them to do so if necessary. The piece of -weed, with crab or crabs attached, may then be bagged for future -examination. - -On turning over the Broad-clawed Crab its under surface will be seen to -be perfectly smooth, with an appearance closely resembling that of white -porcelain. Its foot-jaws, also, are proportionately large, and closely -fringed with hairs; and the last pair of legs, which are very slender in -build, are folded closely beneath the body. Further, the abdomen is -wide, composed of six distinct movable segments, and terminating in a -tail-fin composed of five fringed plates. - -Drop the crab into water, and it will immediately extend its abdomen, -which it will flap sharply under its body somewhat after the manner of -lobsters and shrimps, and thus swim backward by a series of jerks as it -sinks to the bottom. On reaching the bottom it instantly grasps the -solid material, applies itself closely to the surface, and glides away -into the nearest chink it can find. - -As one observes the nature and movements of these interesting little -crabs one cannot fail to see how beautifully their form and structure -are adapted to their habits. They are peculiarly constructed for abode -in narrow chinks and crannies, and for feeding on the small forms of -life that inhabit such sheltered places. Their legs move in the plane of -their flattened bodies, and as they glide among the confervæ and other -low forms of life that encrust the stones of the beach they feel their -way by, and are possibly also guided by the sense of smell located in, -their long outer antennæ, while the close fringes of their claws and -foot-jaws form admirable sweep-nets by means of which the little animals -that form their food are swept towards the mouth. - -We have other species of stone crabs, one or two of which resemble the -last species, and belong to the same genus, but the others are very -different in general appearance. The Northern Stone Crab (_Lithodes_), -found principally on and off the coasts of Scotland and Ireland, has a -spiny covering with a long beak. Another species--_Dromia vulgaris_--is -somewhat similar in habit, though it can hardly be termed a stone crab, -since it inhabits deep water, and apparently lives among the sponges, -sea firs, and weeds that cover the bottom. - - [Illustration: FIG. 212.--_Dromia vulgaris_] - - [Illustration: FIG. 213.--THE HERMIT CRAB IN A WHELK SHELL] - -The remainder of the Peculiar-tailed Decapods belong to the Soldier or -Hermit Crabs, and constitute the genus _Pagurus_. - -Every one who has searched a few rock pools will have seen the familiar -Hermits, and will probably have been interested in their varied antics. -First you observe the shell of a mollusc--a Trochus, Periwinkle, or a -Whelk--travelling at an abnormal rate for a member of its class. You -approach closely to make an inquiry into the matter, when the motion -suddenly ceases, and the shell instantly drops into position with its -mouth close to the surface below. If left undisturbed for only a short -time, the rapid and somewhat jerky motion is resumed, only to cease as -suddenly as before as soon as the inhabitant is again threatened. - -On examining the shell we find that it is the home of a species of crab, -and that the animal within it is completely hidden with the exception of -its head, stalked eyes and long, slender antennæ, one very large claw, -and a few walking legs. - -To remove the creature from its home is no easy matter as a rule. To -pull it out by means of its legs or its antennæ would probably be to -sever some portion of its body; but if you thrust the creature, shell -and all, among the spreading tentacles of a large anemone, it will at -once grasp the peril of the situation; and, if the shell has already -been secured by the clinging petals of this dangerous marine flower, the -hermit will speedily quit its home and endeavour to rush from the many -snares in order to secure its freedom. Or, it not infrequently happens -that the occupied shell is one that has withstood many a storm, but not -without the loss of the apex of its cone. In this case the insertion of -a very flexible fibre into the opening thus made will cause the hermit -to leave its home in the possession of the enemy. - -Having, by some means or other, managed to drive the crab from its -shell, we place it in a shallow rock pool, or in a vessel of sea water, -and observe the chief features of its structure. - -The first thing that strikes one is the absence of a calcified skin on -the extended abdomen, which is so soft that, remembering with what -eagerness fishes will attack and devour crabs of all kinds, we can at -once understand the necessity of such a home as the creature selects. -Again, we observe the presence of appendages at the tip of the abdomen -by means of which the crab is enabled to hold itself securely in the -shell. Also, when we note the general form of the armoured portion of -the body, and the position of the soft-skinned abdomen, we can see how -well adapted the whole is to fit snugly into the spiral shell of a whelk -or winkle. - -We also observe that one of the pincers is much larger than the other, -and the value of such an arrangement may be estimated when we see the -animal at home. The smaller claw, together with the other appendages -used for walking or prehension, can be retracted within the shell, but -the large claw, which constitutes a formidable weapon of attack and -defence, is not only in such a position as to be ready for immediate -use; but, lying as it does in front of the body, with other portions -hidden more or less behind it, it serves the purpose of a shield when -the animal retires. - -If we place a homeless hermit crab in a rock pool, the behaviour of the -creature immediately suggests a feeling of uneasiness--a sense of -danger--for it moves about in a very erratic fashion that is quite -different from the straightforward and deliberate action of the same -animal when properly protected; and very amusing results may be obtained -by making it the subject of a few harmless experiments. For instance, -drop down before it an empty whelk-shell that is much too large to -properly accommodate its body. It will immediately approach the -untenanted house, search and probe it well with its antennæ and other -appendages, and then, finding it uninhabited, and having no apartment of -more suitable size at hand, will abruptly gives its body a turn and -hastily thrust itself backwards into it. - -If at the time of this experiment the advancing tide disturbs the water -of the pool, the result is somewhat ludicrous, for the shell, too -cumbersome to be controlled by the creature within, is, regardless of -its attempts to maintain a normal position, turned over and over as each -wave advances and retreats. - -Again, supposing the shell supplied to be too small for the intended -occupant, it will, after the usual examination of the interior, thrust -its soft abdomen as far in as possible, and make the best of the -unsatisfactory circumstances until a more suitable home can be found. -And if, at this distressing period, we drop before it a shell of just -the right size--the one from which the creature was originally expelled -for instance, it is astonishing how quickly the change of houses will be -accomplished. After a brief examination of the shell with the object of -determining whether all is right within, during which the crab continues -to avail itself of the imperfect accommodation afforded by the previous -shell, it rapidly extracts its body from the one and thrusts itself -backwards into the other. Its normal habits are at once resumed, all its -movements being now suggestive of confidence and contentment. - -We have already referred (p. 153) to the fact that a large anemone -(_Sagartia parasitica_) is commonly found attached to a whelk shell, -which at the same time forms the home of the hermit crab, and (p. 44) -that a marine worm (_Nereis_) is also a common associate of the hermit, -taking up its abode in the interior of the same shell; and we also -briefly discussed the mutual advantage of such an arrangement to the -parties concerned. These triple combinations are not so frequently met -with on the shore between the tide-marks, but are dredged in -considerable numbers by the trawler; and the reader will find it repay -him to secure one in order that he may be able to watch the interesting -habits of the associates. The movements of the hermit crab are always -pleasing, particularly the manner in which it seizes and manipulates its -food; and still more so is the occasional appearance of the head of the -worm, always in exactly the same place, for the purpose of deliberately -stealing the food from the very jaws of the crab. - -Hermit crabs are easily kept in captivity, and may be fed on any kind of -animal food, but care should be taken not to allow an excess of food to -remain in the water and render it putrid by decomposition. As long as -the crabs are active and remain within their shells you may assume that -the conditions are favourable; but when they become sluggish in their -movements, and leave their homes, the sanitary condition of the -aquarium should be regarded with suspicion; for hermit crabs, like many -of the marine tube worms, generally quit their homes when the conditions -are unfavourable, as if they preferred to die outside. - -The Common Hermit Crab (_Pagurus Bernhardus_), also known as the Soldier -Crab, on account of its very pugnacious habits, is common almost -everywhere on our coasts, and may be distinguished by the numerous -little tubercles on the claws and on the upper edge of the front legs; -and there are several other species, belonging to the same genus, -distributed more or less locally on the various shores. All are similar -in general structure and habits, the various species being identified -principally by means of their colour, the variations in the form of the -appendages, and the general character--smooth, tubercular, spiny, -&c.--of the exo-skeleton. One species, found in the sandy bays of -Cornwall, burrows rapidly in the sand. - -Coming now to the true crabs--the _Brachyura_, or Short-tailed -crustaceans, as sometimes distinguished from the _Anomura_--we find -quite a variety of interesting creatures, many species of which are -always within the reach of the collector at work between the tide-marks. -In all these the abdomen is only slightly developed, and is never used -in swimming, being permanently folded beneath the thorax. This portion -of the body, however, is usually very distinctly segmented, and if it be -lifted from its position it will be found that some of the segments bear -appendages corresponding with the swimmerets of the lobster. It is also -wider in the female than in the male, and crabs of the former sex may -often be found during the summer with the abdomen more or less -depressed, and the space beneath it quite filled with eggs. - -The upper surface of the carapace of crabs is often very distinctly -grooved, and it is interesting to note that these features of the -exo-skeleton are not merely of external significance, for they usually -correspond in position with various internal structures, some of them -denoting the areas of the insertions of important muscles, and others -enclosing the regions of certain of the internal organs. - -It will be noticed, too, that the carapace, which in lobsters is often -less than half the length of the body, covers the entire body of the -crab, except, perhaps, a very small linear portion between the bases of -the last pair of legs, where the first part of the segmented abdomen is -visible from above. - -The true crabs of our seas may be divided into four groups, as follow: - - 1. _Oxystomata_, or Pointed-mouthed Crabs; - 2. _Oxyrhyncha_, or Pointed-beaked Crabs; - 3. _Catometopa_, with forehead turned downwards; and - 4. _Cyclometopa_, or Round-headed Crabs; - -and we shall briefly observe some of the more conspicuous and -interesting species in the order of the tribes as just given. - -The first division is not well represented in our seas, the principal -species being the Nut Crabs and the Long-armed Crab, all of which may be -distinguished by the peculiar arrangement of the foot-jaws, which, when -closed, form a triangle with an acute angle turned towards the front. -The Nut Crabs are mostly small; and, since they generally inhabit deep -water, are not commonly seen on the shore; but perfect specimens may -sometimes be found among the contents of fishes' stomachs. They derive -their name from the nature of the carapace, which is of a rounded form -and very hard and strong. - -Pennant's Long-armed Crab (_Corystes Cassivelaunus_) may commonly be -seen entangled among fishermen's nets, but is not often seen on the -shore at low tide. Its carapace is very convex above, with three sharp -spines on each side, and the grooves are so arranged as to suggest the -appearance of a face. Our illustration represents the female, but the -'arms' of the male are very much longer than those of this sex. - -The Sharp-beaked Crabs (_Oxyrhyncha_) include all those long-legged -creatures that are known collectively as the Spider Crabs; and here, -again, we have to do with species that almost exclusively inhabit deep -water. Although this is the case, but little difficulty is experienced, -as a rule, in obtaining specimens. If you are unable to take a trip in a -trawler for the purpose of examining the 'rubbish' that is dredged from -deep water, simply obtain permission to search the nets and the boats as -they arrive in port. In the latter case you are almost certain to find -the crabs you require, though it is probable that some of the species -will have been damaged by the hauling and shaking of the nets. - - [Illustration: FIG. 214.--THE LONG-ARMED CRAB (_Corystes - Cassivelaunus_)] - -These interesting crabs have been spoken of as the monkeys of the sea, -and the comparison will certainly be tolerated by anyone who has watched -the creatures as they climb among the corallines and sea firs in an -aquarium. Among such growths they are quite at home; and although their -movements do not often suggest the extreme agility of the monkey tribe, -yet the ease with which they seize the branches of the submarine forest -with their long 'arms' and pull their bodies from one tree-like -structure to another is decidedly monkey-like. Their comparison with the -long-legged spiders is also a happy one as far as their general form and -movements are concerned, but it must be remembered that they have not -the same reputation for cruel, predaceous habits, for they are more -truly the scavengers of the deep, subsisting mainly on the decomposing -bodies of their dead associates. The movements of most spider crabs are -so slow and deliberate that one can hardly imagine them capable of -anything of the nature of violent action; yet, when occasion requires -it, they will sometimes strike at the object of their wrath with a most -vigorous snap of their claws. - - [Illustration: FIG. 215.--SPIDER CRABS AT HOME] - -In these crabs, too, we find most interesting instances of protective -resemblance to their surroundings. Some of the small, slender-legged -species are not to be recognised without a careful search when they are -at rest among clusters of sea firs, their thin appendages and small -bodies being hardly discernible in the midst of the slender, encrusted -branches, and their peculiar forms are still more concealed by their -colouring, which generally closely resembles that of the growths among -which they live. Further, the carapace of spider crabs is in itself a -garden on which thrive low forms of both animal and vegetable life. -Minute _Algæ_, and occasionally some of moderate size, are rooted to the -shell, often securely held by the aid of the rough hairs and tubercles -that are so characteristic of the exo-skeletons of these creatures; and -patches and tufts of animal colonies that have found a convenient -settlement on the moving bed still further serve to obscure the nature -of the living mass below--a mass that is always in danger of becoming -the prey of the fishes which inhabit deep water. It is probable, -therefore, that this association is one that is beneficial to both -sides as far as the animal life is concerned, the lower species serving -to disguise the true nature of the crab, thus protecting it from its -numerous enemies, while they in return are conveyed, carriage paid, to -the feeding-grounds, where they can freely partake of the fragments that -become diffused in the surrounding water. - -Our illustration on p. 288 shows three species of spider crabs, all of -which are common on parts of our shores. The Scorpion Spider Crab -(_Inachus dorsetensis_) derives its specific name from the fact that it -was first found off the coast of Dorset; but it is abundant off many of -our shores, both in the south and north, and may frequently be seen -entangled among the fishermen's nets. It may be distinguished from other -and similar species by the four spines arranged in a line across the -front portion of the carapace, and the five large, pointed tubercles -behind them. This species is undoubtedly a favourite food of the cod, -for several specimens may often be taken from the stomach of a single -fish. - -The next species--The Slender-beaked Spider Crab (_Stenorhynchus -tenuirostris_)--is seldom missing from the dredgings hauled in off the -south-west coast, and is fairly common in other parts. Its legs are -extremely slender, and bear spines on the inner side, and its body, -where free from the incrustations so often covering the carapace of -spider crabs, is of a fresh pink colour. - -The other one shown in the same illustration is _Arctopsis lanata_, -sometimes known as Gibb's Crab, the carapace of which is pointed behind, -bears a large pointed tubercle on each side, and is completely covered -with a thick clothing of stiff hairs. It is also common on many parts of -our coasts, more especially the coasts of Devon and Cornwall. - -Closely allied to the last-named, and belonging to the same family, is -the well-known Thornback Crab (_Maia Squinado_), also a very common -crab, of which we give a separate illustration. - -The tribe _Catametopa_ does not contain many British species, the -principal being the Pea Crabs; the Floating Crab, which is occasionally -washed on the south-west coast; and the beautiful Angular Crab. In these -the front of the carapace is turned downwards--a feature that has -suggested the name of the tribe. - -The pea crabs are all small, and they are parasites, living within the -shells of bivalve molluscs. One species--the Common Pea Crab -(_Pinnotheres pisum_) is frequently found in the Edible Mussel; the -female, which is much larger than the male, being much more commonly -found. Another species--the Pinna Pea Crab (_P. veterum_), infests the -Pinna and Modiolus. - - [Illustration: FIG. 216.--THE THORNBACK CRAB (_Maia Squinado_)] - - [Illustration: FIG. 217.--THE PEA CRAB (_Pinnotheres pisum_)] - -On Plate VI. is a drawing of the Angular Crab (_Gonoplax angulata_) -mentioned above, the striking form and delicate colouring of which can -never be mistaken. We would, however, call particular attention to the -broad and square front of the cephalothorax, with its two sharp spines, -and to the length of the eye-stalks. Unfortunately for the amateur, this -pretty crab is only to be found in deep water, off the coasts of Devon -and Cornwall, so that here, again, the aid of the fisherman is valuable; -but, as observed in the case of other deep-sea dwellers, may also be -looked for in the stomachs of cod and other bottom fishes. The sex -figured is the male, in which, when fully grown, the front legs are much -longer than in the female. - - [Illustration: PLATE VI. - - CRUSTACEA - - 1. Gonoplax angulata - 2. Xantho florida - 3. Portunus puber - 4. Polybius Henslowii - 5. Porcellana platycheles] - -The remaining division of the crabs--the _Cyclometopa_ or Round-fronted -Crabs, contains the larger number of species that may truly be described -as common objects of the shore, for while some of them are well adapted -for swimming, and live in the open water, the majority inhabit the -shore, either between or just beyond the tide-marks, roaming about more -or less freely when in the water, but usually hiding under stones or -weeds, or burrowing into the sand, when left behind by the receding -tide. - - [Illustration: FIG. 218.--THE COMMON SHORE CRAB (_Carcinus mænas_)] - -The members of this tribe may be known at sight by the form of the -carapace, which is wide and rounded in front, and narrowed behind. - -The accompanying illustration represents the commonest of the group--the -Common Shore Crab (_Carcinus mænas_), which is found plentifully on all -our coasts, and even in brackish water far up the estuaries of rivers. -It is a very voracious and pugnacious creature, probably the most active -of all our crabs, and its movements, whether connected with its feeding, -its sports, or its warfare, are always very interesting when observed -through clear water. This crab varies considerably in colour, but is -usually of the greenish tinge shown in the frontispiece. - -Another abundant and well-known species is the Edible Crab (_Cancer -pagurus_), which is as familiar an object in town as on the sea coast. -Unlike the common lobster, its natural colour is not considerably -changed by boiling, being only turned from a dull to a brighter red. - -The finest specimens of this crab are to be caught beyond low-water -mark, the usual snare being the basket or pot, baited with fish refuse, -but large numbers live among the stones and rocks left exposed at low -tide, and sometimes include specimens of considerable size. They should -be looked for under large stones that are loosely piled together, or in -the narrow chinks of rocks. - -It is very interesting to compare the habits of the two common crabs -just mentioned. The former, when molested, will run off in great haste, -but always retreat with its front to the enemy, and its sharp and -powerful pincers far apart and wide open, ready for immediate use in its -own defence if necessary. The latter species, on the other hand, though -strongly built and provided with formidable claws, seldom runs far, and -hardly ever attacks one in the act of pulling it out of its -hiding-place; but, on the contrary, doubles all its ten legs under its -body as if endeavouring to approach, as nearly as possible, the form of -a ball, and will allow itself to be rolled about without showing any -signs of life. - -The genus _Xantho_ contains two or three species that are common on the -Cornish and Devon coasts, and which may be known by their depressed and -deeply-grooved carapace and the presence of three or four prominent -tubercles on the latero-anterior margins. The abdomen of the female has -seven joints, while that of the male has only five. One of these -(_Xantho florida_), shown on Plate VI., is a powerfully built crab, as -may be seen when, after being disturbed, it pushes its way among the -loose stones of the beach, often lifting masses many times its own -weight. - -On the same plate is also a figure of the pretty Velvet Crab (_Portunus -puber_), also known as the Lady Crab and the Violet Fiddler. The first -of these popular names has its origin in the dense covering of close -hairs that clothe the carapace, and the last refers to the beautiful -violet colouring of parts of the front legs, and, to a lesser extent, of -the remaining legs. This is, perhaps, the most ferocious of all our -shore crabs, and its attacks, when disturbed, are of such a determined -nature that the catching of the larger specimens is quite a lively -sport. Though it can hardly be described as an abundant species, yet it -sometimes occurs locally in such numbers that it may be found under -nearly every stone of any size. In fact, we have searched two or three -localities on the south-west coast where this crab is not only -extremely numerous, but is at the same time almost the only species to -be found; and it seems not unlikely that the pugnacious Lady has been -the means of driving the less formidable species from its favourite -haunts. - -When you disturb a Velvet Crab it will immediately raise itself in a -menacing attitude, stretching its brightly coloured pincers as wide -apart as possible, and then it will either retreat backwards, or even -make a firm stand, ready to strike as soon as it is threatened with an -attempted touch. Try to grasp it, and its two powerful weapons of -defence are brought together with lightning-like rapidity giving one a -decidedly smart blow, possibly followed by a grip of great tenacity for -a creature of its size; but, should it miss its aim, its pincers strike -together with a sharp click, only, however, to extend at once in -preparation for the next attempt. - -It will be observed that the walking legs of this crab are all -flattened, and that while the first three pairs terminate in sharp, -lance-like claws, the last pair are broad and fringed with hairs, thus -showing their close relationship to the swimming crabs. In fact, the -same genus contains British species which are popularly known as -Swimming Crabs. - -One of the swimmers is represented in fig. 4 of Plate VI. It is -generally known as Henslow's Swimming Crab or the Nipper, the scientific -name being _Polybius Henslowii_. The carapace of this species is quite -smooth, thus enabling the crab to move through the water with less -resistance, and the walking legs, particularly the last pair, are -flattened and fringed for use as paddles. It is said that this crab can -raise itself from the bottom to the surface of moderately deep water by -means of the swimming feet, and that it preys on fishes which it pursues -with some vigour. - -Other crabs than those briefly described will reveal themselves to the -sea-side collector, but we have not the space to introduce them here. -Sufficient information has been given, however, to enable the reader to -broadly classify his specimens--a matter of more importance to the young -naturalist than the mere naming of species. - -Leaving the crustaceans now, and passing for a moment to the -_Arachnoidea_--the second great division of the arthropods--we shall -briefly describe the Shore Spider (_Pycnogonum littorale_), which is the -only representative of the class likely to be met with by the sea-shore -collector. - -It will be seen by our illustration that this creature by no means -resembles a typical spider. The powerful jaws, really modified antennæ, -that are such formidable weapons in the latter, together with other -appendages of the head, are undeveloped in the shore spider, and the -head is prolonged forward to form a rigid beak with the mouth at the -summit, and the head and thorax together form a cephalothorax of four -distinct segments, each of which bears a pair of legs. Further, the -cephalothorax forms almost the whole of the body, for the abdomen, -usually so large in spiders, is here represented by a mere tubercle. The -shore spider is unable to swim, but crawls about among the weeds and -stones of the bottom, clinging firmly by means of the curved claws of -its eight thick legs, and is protected by its dull grey colour which -closely resembles that of the encrusted stones among which it spends the -greater portion of its existence. It may sometimes be found hiding under -stones near low-water mark, but is far more commonly seen among the -'rubbish' hauled in by the trawl. - - [Illustration: FIG. 219.--THE SHORE SPIDER] - -We shall conclude our brief survey of the marine arthropods by a short -account of the insect life of the sea shore, referring to a few of the -more prominent forms and observing some of their habits; but since it is -probable that some of our readers are not well acquainted with the -general characters of this interesting class of animal life, it will be -advisable to precede our remarks by a short summary of their principal -distinguishing features, more particularly those in which they differ -from the other arthropods. - -Insects, then, may be defined as those arthropods in which the body is -divided into three distinct parts--the _head_, composed of from four to -six fused segments, and bearing as many pairs of appendages; the -_thorax_, formed of three segments, each of which gives attachment to a -pair of legs; and the _abdomen_, composed of eight segments that bear no -appendages. - -The head of an insect is furnished with a pair of compound eyes, very -similar in structure to those of a crustacean, and often, in addition, a -cluster of simple eyes; also a pair of antennæ, usually composed of many -joints. These antennæ are important organs of touch, and are employed, -at least by many forms, as a means of communication between one insect -and another. In them are also located the organs of hearing, and, -possibly, those of other senses. - -The mouth varies very considerably in different insects, but is often -supplied with a pair of mandibles or biting jaws, and, below them, a -pair of maxillæ or chewing jaws, both pairs being jointed to the head in -such a manner as to be capable only of horizontal movements. Above and -below these jaws are, respectively, the upper lip or labrum, and the -lower lip or labium, the latter having appended to it a pair of jointed -feelers called the labial palpi, and an additional pair of palpi are -also frequently attached to the maxillæ, and therefore called the -maxillary palpi. - -These organs of the mouth of an insect are modified in various ways -according to the functions they are called upon to perform. Thus, in -bees, the upper lip, as well as the mandibles, are adapted for chewing, -while the maxillæ and the labium are grooved in such a manner that when -brought together they form a tube through which fluids may be sucked -into the mouth. Also, in the butterfly and the moth, the maxillæ are not -constructed for chewing, but consist of two channelled rods which, when -approximated, form a long tube or proboscis employed for suction; and in -these insects the labial palps are large for the protection of the -proboscis, which is retracted and closely coiled between them when not -in use. Further, in the bugs, the labium is long and tubular, while the -mandibles and maxillæ are often modified into sharp, stiff bristles that -work within the tube, the whole thus forming a combined piercing and -sucking arrangement. - - [Illustration: FIG. 220.--THE LEG OF AN INSECT] - -The leg of an insect is built up much in the same manner as that of the -typical crustacean. It consists of a basal hip joint or coxa, a ring -segment or _trochanter_, a thigh (_femur_), a shin (_tibia_), and the -tarsus or foot of several joints which terminates in a claw or claws, -and is often provided with sucking-pads. The wings, when present, are -attached to the second and third segments of the thorax, if two pairs, -but if, as in the case of the house fly, the insect has only one pair of -wings, these are always appended to the second segment. - -Insects are developed from eggs, but in their young state they are -segmented larvæ, with strong jaws, antennæ, simple eyes, and usually -three pairs of legs attached to the first three segments next to the -head. - -As regards internal structure, we need only mention here that the body -is traversed by numerous branching tubes (_tracheæ_) that open at the -exterior and constitute the respiratory apparatus; that the insect is -provided with a contractile, tubular heart by means of which the blood -is propelled through a system of blood-vessels; that the nervous system -consists of a chain of ganglia, connected by a nerve cord, sending nerve -filaments to all parts of the body; and that the digestive tube is often -a complicated structure, especially in the case of those insects that -feed on herbivorous matter. - - [Illustration: FIG. 221.--TRACHEA OF AN INSECT, MAGNIFIED] - -The above outline will be sufficient to show that insects are not very -unlike the crustaceans in their general characteristics; and, indeed, -when we examine certain forms, noting the distinct segmentation of the -body, the hardened exo-skeleton of chitinous material, and the -unhardened skin between the segments to admit of freedom of movement, we -see a striking resemblance in external appearance to some of the typical -crustaceans. - -Insects are divided into several orders, and some of these are fairly -well represented on the sea coasts, though it must be understood that -but few species are strictly aquatic and marine in their habits. -Fresh-water pools and streams teem with insect life, and quite a large -number of the insects that live in these situations are peculiarly -adapted for a life of submersion, their general form being often such as -to allow of rapid progress through the water, their appendages modified -into admirable swimming organs, and, in many cases, their breathing -apparatus adapted for the direct absorption of oxygen dissolved in the -water. - -However, one would hardly expect to find similar forms of life abundant -in the water that washes our shores, the disturbing action of the waves, -even in calm weather, being more than such fragile creatures could -withstand. And this is really the case, for there are but few insects -that may be described as marine in the strictest sense of the word; and -of these the species that have been observed are mostly inhabitants of -warmer seas. - -It is noteworthy that all the insects which exhibit marine tendencies -are small, and they seldom, if ever, live permanently below the surface. -But few of them can swim. A few run on the surface of the water, -supporting themselves on the surface film after the manner of -water-gnats, whirligig beetles, &c., without ever being wetted; and -these are said to feed on different kinds of floating matter, and -occasionally to dive below the surface. - -A rambler on the sea shore in the summer time will always meet with -plenty of insect life, but the number of species observed may not be -large: and omitting all those which show no decided preference for the -coast, but are found in inland districts as well, we find that by far -the larger proportion live at or near the high-water mark, where they -feed on the refuse washed up by the waves. Some species, however, live -among the stones, or burrow into the sand, between the tide-marks; and -these, as a rule, are not driven inland by each advancing tide, but -allow the sea to wash over them, having at first protected themselves -from disturbance by burrowing or seeking other suitable shelter. - -These latter, like many of the insects that inhabit fresh water, are -well adapted to withstand prolonged immersion. Their bodies are not -capable of being wetted, a covering of short hairs effectually -preventing the water from coming into actual contact with the body. The -openings of the breathing tubes (spiracles) are also guarded by closely -set hairs which prevent the water from entering; and, in some cases, the -creatures are provided with special air-sacs in which a supply of air is -stored for use while the insect is shut off from the external -atmosphere. - -The lowest order of insects includes the so-called Bugs (_Rhynchota_), -which are parasitic on plants or animals. Quite a number of these are to -be found inhabiting fresh water, but only one is truly marine in its -tendencies. This one is a small insect, only about an eighth of an inch -in length, and named _Æpophilus_ (fig. 222). It has never been seen -except between the tide-marks, and occurs so near low-water level that -it is submerged during the greater part of its existence. But little is -known of this peculiar creature. Even its food has not been ascertained. -As with the other Rhynchota, but little change of form takes place -during growth, the young being very much like the adult in appearance. -It has been observed that the larvæ live crowded together under the -protection of stones. - -The reader is probably acquainted with those fresh-water bugs that are -popularly known as 'boatmen' on account of the oar-like action of their -long, fringed hind legs; and although none of these may be described as -marine, yet certain species may often be seen in salt and brackish -water, living in company with creatures that are decidedly inhabitants -of the sea. - - [Illustration: FIG. 222.--SEA SHORE INSECTS - 1. _Æpophilus._ 2. _Machilis maritima._ 3. _Isotoma maritima._ - 4. _Coelopa_] - -We frequently meet with a pretty, slender-bodied insect, measuring about -half an inch in length without appendages, creeping over the rocks in -the sunshine, generally very near the crevices in which they hide, and -leaping from place to place when disturbed. These are the Bristle-tails -(_Machilis_), belonging to the order _Thysanura_, the members of which, -like the bugs, scarcely undergo any metamorphoses. This insect (fig. -222) has long antennæ, and also a long, stiff, and elastic bristle -extending backwards from the tip of the abdomen; and this bristle is the -means by which the creature leaps. Occasionally the machilis may be -found resting on the surface of the still water of a rock pool, in which -case its body is not wetted, its weight not being sufficient to break -the surface film of the water; and, in fact, the film is even -sufficiently firm to enable the insect to leap on the surface just as it -would on a solid body. - -Allied to the bristle-tails, and usually grouped with them in the same -order, are the little Spring-tails, some species of which may often be -seen huddled together on the surface of the water of a rock pool. They -are so small that, unless closely examined, they may be mistaken for -particles of floating inorganic matter which have been blown into a -sheltered corner of the pool, and this idea may be strengthened by the -fact that these minute creatures _are_ driven by the wind into such -sheltered spots. But when we disturb them their true nature immediately -becomes apparent, for they may then be seen to move about on the surface -of the water, sometimes creeping on the surface film, and clambering on -the adjacent rock or weed, or leaping more or less vigorously, in which -latter case their bodies do not become wetted, the surface film -remaining unbroken by their exertions. And even when the rising tide -drives the spring-tails into crevices where they remain submerged, -perhaps for hours together, their bodies still remain dry, the water -being kept off by numerous short bristles and prominences with which -they are furnished. - -When we examine a spring-tail by means of a lens we observe that it has -no traces of wings, but that each of the three segments representing the -thorax bears a pair of short legs, and that the abdomen consists of only -five or six segments. The head is furnished with a pair of jaws, and the -antennæ, which are short and thick, are composed of but few -joints--never more than six in number. - -Some spring-tails live among the refuse washed up on the beach, where -they may be seen jumping about in company with the sandhoppers when the -material is disturbed. Such is the case with _Isotoma maritima_, the -illustration of which shows the forked tail that enables the little -animal to jump about so vigorously. But some of the marine spring-tails -are not so true to their name, since they are not provided with this -characteristic jumping organ, and have to content themselves by creeping -about slowly with the aid of their short legs. One of these springless -spring-tails (_Anurida maritima_) is one of the commonest of the group, -and is distributed over almost every part of our coast. - -Passing over several orders of insects which do not seem to have any -marine representatives, we come to the _Diptera_ or two-winged insects, -of which the familiar house-fly is a type, and here we have to deal with -those troublesome creatures that literally swarm in the neighbourhood of -the matter washed up to the highest level of the tide during the whole -of the summer months. But although these insects are so very numerous, -we do not find among them a particularly large number of species, their -abundance being due more to the extreme prolificacy of those that -occur. - -In this order, which includes all gnat-like creatures, as well as those -insects that are generally known as flies, the first pair of wings are -well developed, while the second pair are rudimentary, and represented -merely by a pair of scales, or by two little pin-like bodies called the -balancers or _halteres_. Some are provided with piercing organs by means -of which they can inflict a small wound and then extract the juices of -their victim, as does the female gnat, but the majority have a proboscis -adapted for suction only. The larvæ of the _Diptera_ are generally -limbless maggots, gifted with a pair of jaws, and they are usually very -voracious feeders, devouring decomposing animal or vegetable matter in -enormous quantities. - -If we turn over a fermenting mass of the miscellaneous matter thrown up -on the beach quite beyond the reach of the tides, we may observe a -multitude of little maggots which feed on the moist, odorous portion -that was protected from the direct rays of the sun, together with a -number of dark-coloured pupæ that lie at the very bottom of the heap or -buried in the sand below. These are two stages of the black fly -(_Coelopa frigida_) that is so attentive to us when we rest on the dry -sand above high-water mark. This fly is very like the common house-fly -in general appearance, though its body is rather smaller. Other species -of the same genus often accompany them, all being very similar in -general appearance and habits, and none of the larvæ seem adapted to a -life in the water. They are always found beyond the reach of the tide, -and are drowned if submerged for any length of time. - -Another species belonging to the genus _Actora_ will often be seen in -the same company, and this is readily distinguished by their lighter -greyish colour and its superior size. Also, along the water-line, we -often meet with species of the family _Dolichopodidæ_, so called on -account of the length of their legs, and noted for the beautiful -metallic colours which adorn their bodies. These flies are carnivorous -in habit, deriving their food from living as well as from freshly killed -animals, and their short, fleshy proboscis contains a piercing bristle -by which they can puncture the skins of the animals that provide them -with food. Most of the flies of this group live on trees, walls, fences, -&c., where they pursue and attack their prey, but certain species follow -the line of breakers on the sea shore, as before indicated, and obtain -their food from the various marine animals that are stranded on the -beach. A peculiar feature of the family is the nature of the abdomen of -the males, which is bent under the body and furnished with a number of -appendages. - -Another marine dipterous insect is a gnat-like fly closely allied to -_Chironomus_, which we have described in a former work[A] of this series -dealing with fresh-water life; and it will be sufficient to mention here -that _Chironomus_ is commonly known as the window-gnat on account of the -frequency with which it may be seen flying on the windows of our -dwellings; also that the larva, known popularly as the bloodworm, is -truly aquatic in habit, being able to swim by rapidly looping its body -in opposite directions, and being provided with a breathing apparatus -adapted for the absorption of the oxygen gas contained in solution in -water. The larva of the marine species referred to above may sometimes -be seen in rock pools, where it shelters itself among the sediment at -the bottom. It is much like the bloodworm in appearance and structure, -but its body is greenish instead of red. - -The last order of insects calling for notice here is the _Coleoptera_ or -sheath-winged insects, popularly known as beetles, and characterised by -the hard and horny nature of the front pair of wings (elytra), which are -modified into sheaths and serve to protect the second pair; the latter -are thin and membranous, usually adapted for flight, and lie folded -beneath the former when not in use. - -One large section of beetles is known as the _Geodephaga_ or Ground -Beetles--a group of very predaceous insects that burrow into the soil -and attack almost every living thing that comes in their way, and well -represented by numerous species that may be found in our gardens, and, -in fact, almost everywhere. - -A considerable number of these insects show a decided preference for -salt marshes and the sea shore, where they hide under stones, or burrow -into the sand or mud in search of their prey. They are not marine in the -strictest sense of the word, for they are not adapted for a life of -submersion in water, either in the larval or in the perfect condition; -yet they are often found below high-water level, and some species burrow -into the sand of the beach as the tide advances, allowing the water to -cover them for hours together. - -One interesting family of the ground beetles (the _Bembidiidæ_) includes -several small species, all of which frequent salt and wet places, such -as salt marshes, the mouths of rivers, and the sea shore. We give -enlarged illustrations of a few of these, the actual size being denoted -at the side of each. - -[Footnote A: _Life in Ponds and Streams._] - - [Illustration: FIG. 223.--MARINE BEETLES OF THE GENUS _Bembidium_ - 1. _B. biguttatum._ 2. _B. pallidipenne._ 3. _B. fumigatum._ - 4. _B. quadriguttatum_] - -_Bembidium biguttatum_ may be identified by its brilliant bronze-green -colour, and the two distinct impressions on the elytra which have -suggested the specific name. _B. pallidipenne_ is, as its name implies, -a pale-winged species, the elytra being of a light yellowish colour. _B. -fumigatum_ is so called on account of the smoky tint of the elytra; and -the last species of the same genus figured (_B. quadriguttatum_) may be -known by the four conspicuous spots on the deep violet-coloured outer -wings. - -The same family contains an interesting little beetle--_Cillenium -laterale_--only about one-sixth of an inch in length, that lives among -the refuse washed on the beach, where it feeds on the sandhoppers; and -although the latter are so much superior in size, the beetle has no -difficulty in holding and killing its prey, always seizing it on the -ventral side of the body, which is less protected by the hardened skin. -This species, which is of a copper colour, does not confine its ravages -to that portion of the beach which is above high-water mark, but often -allows itself to be covered by the advancing tide, remaining submerged -for a considerable time. Another species--_Aëpus (Æpys) marinus_--is -even more aquatic in its habits, for it searches out its prey among -stones, chiefly at the mouths of rivers, below high-water level, and is -often submerged for hours together. It is even provided with air-sacs to -enable it to withstand such prolonged submersions. - - [Illustration: FIG. 224.--MARINE BEETLES - 1. _Æpys marinus._ 2. _Micralymma brevipenne_] - -There is another section of beetles which has elytra so short that they -cover only a small portion of the abdomen; but although so short, these -elytra completely cover the long membranous wings, which are folded up -beneath them in a wonderfully compact manner. The section referred to is -termed _Brachelytra_, from the feature just mentioned, and includes a -few species that are more or less marine in their habits. One of -them--_Micralymma brevipenne_--lives under stones below high-water -level, and apparently passes through all its stages within reach of the -waves. Another of the _Brachelytra_ (_Bledius_) burrows into the sand or -mud near high-water mark, throwing up the débris as it proceeds. Both -these beetles are carnivorous, and the latter is in turn preyed upon by -a ground beetle of the genus _Dyschirius_, which hunts and devours it -within its own home. - -The reader will have observed that the sub-kingdom _Arthropoda_ is not -only a very extensive one in the sense that it contains a vast number of -animal forms, but also that its members exhibit a very great variety of -form and structure; and the beginner will probably find no little -difficulty in locating his specimens in their correct position in the -scale of life. The following table, however, will serve to show the -general classification of the group at a glance, and thus form a basis -for a more detailed study at any future time:-- - - - - - SUB-KINGDOM ARTHROPODA - - CLASSIFICATION - - - Class =CRUSTACEA=. - Sub-class =ENTOMOSTRACA=. - Order =Astracoda=--Free. Body enclosed in a bivalve shell. - Order =Copepoda=--Free. Five pairs of feet adapted for swimming. - Order =Cirripedia=--Sessile. Enclosed in a shell of many valves. - Order =Branchiopoda=--Free. Gills attached to feet. - Sub-class =MALACOSTRACA=. - Division =EDRIOPHTHALMATA=, or Sessile-eyed Crustaceans. - Order =Isopoda=--Body flattened. Seven pairs of legs--equal. - Order =Amphipoda=--Body flattened laterally. Legs adapted for - both walking and swimming. - Division =PODOPHTHALMATA=, or Stalk-eyed Crustaceans. - Order =Stomapoda=--Anterior appendages directed towards the - mouth. - Order =Schizopoda=--Cleft-footed Crustaceans. - Order =Decapoda=--Ten-footed Crustaceans. - Sub-order =Macrura=--Great-tailed. Lobsters, &c. - Sub-order =Brachyura=--Short-tailed. Crabs. - - Class =ARACHNOIDEA=. - Order =Scorpionidæ=--Scorpions. - Order =Araneidæ=--Spiders. - Order =Acarina=--Mites. - - Class =MYRIOPODA=. - Order =Chilopoda=--Centipedes. - Order =Chilognatha=--Millepedes. - - Class =INSECTA=. - Order =Rhynchota=--Imperfect metamorphoses, suctorial mouth. - Bugs. - Order =Thysanura=--Imperfect metamorphoses. No wings. - Divided tail. Spring-tails. - Order =Euplexoptera=--Abdomen with terminal forceps. Earwigs. - Order =Thysanoptera=--Four equal membranous wings. Thrips. - Order =Orthoptera=--Anterior wings usually shorter and firmer. - Grasshoppers, &c. - Order =Neuroptera=--Two pairs of glassy wings--equal. - Order =Trichoptera=--Wings unequal, clad with hairs or scales. - Caddis flies. - Order =Aphaniptera=--No wings, no compound eyes. Fleas. - Order =Diptera=--Two membranous wings. Flies. - Order =Lepidoptera=--Wings clad with scales. Butterflies and - Moths. - Order =Coleoptera=--Fore wings hard and horny. Beetles. - Order =Hymenoptera=--Four membranous wings. Larvæ, footless - grubs. Ants, Bees, &c. - - - - - CHAPTER XIV - - _MARINE VERTEBRATES_ - - -The vertebrates form the highest sub-kingdom of animal life--the -sub-kingdom to which we ourselves belong, the chief distinguishing -characteristic of the group being the presence of an internal skeleton, -the principal part of which consists of a rod or column of cartilaginous -or bony material running along the dorsal side of the body, known as the -_vertebral column_. - - [Illustration: FIG. 225.--TRANSVERSE SECTION THROUGH THE BONY - FRAMEWORK OF A TYPICAL VERTEBRATE ANIMAL - 1. Spinous process of the vertebra. 2. Neural arch. 3. Transverse - process. 5. Body of the vertebra. 6. Breast-bone. 7. Rib. The space - between 2 and 5 is the neural cavity; and that between 5 and 6 is - the visceral cavity] - -This column is usually composed of a number of elements called vertebræ, -each of which gives off two processes that unite and form an arch on its -dorsal side, while all the arches form a tube through which passes the -central portion of the nervous system. - -Below, or on the ventral side of the column, is the body-cavity -containing the organs of digestion and circulation; so that if we make a -transverse section of a vertebrate animal we find that there are two -distinct tubes or cavities--a _neural_ or _cerebro-spinal cavity_ on -the dorsal side of the vertebral column, formed by extensions from the -substance of the latter, and enclosing the chief portion of the nervous -system; and a _body-cavity_ on the ventral side containing the viscera -or internal organs. - -The above features are highly important, and will always prove quite -sufficient to enable us to decide whether any particular animal is a -vertebrate or an invertebrate, for it will be remembered that the body -of the latter has only one cavity, containing the nervous system as well -as the viscera, and that the nervous system is commonly placed along the -ventral side, but never along the dorsal. In addition to this the -vertebrates never have more than two pairs of limbs, and these are -always directed _from_ the nervous system; and the jaws, which are -appendages that move in the horizontal plane in invertebrates, are, in -the higher animals, portions of the framework of the head and move -vertically. In vertebrates, too, there is always a complete blood -system, consisting of a heart with two, three, or four cavities, a -system of arteries to convey the blood to the different parts of the -body, veins to return the blood to the heart, and networks of fine -capillaries connecting the former with the latter. - -All vertebrates, at an early stage of their existence, have a -cartilaginous rod running through the dorsal portion of the body, called -the _notocord_. In some of the lowest animals of the division this rod -persists without any important alterations in structure, while in the -higher forms it gives place to the series of cartilaginous or bony -elements above referred to as the vertebræ; and the arrangement of the -vertebrates into their relative positions in the scale of life is based -largely on the degree of development of the vertebral column from the -notocord. Another interesting feature in the development of a vertebrate -is the formation of five or more transverse, archlike thickenings on -each side of the digestive tube, just behind the head; and, in the -spaces between them, of a series of slits forming a communication -between the pharynx and the exterior. These arches and clefts have but a -brief existence in many vertebrates, while in others they persist -throughout life; and, like other points referred to, they assist us in -recognising the relations of the vertebrates to one another. - -The vertebrates are divided into the following classes:-- - - 1. _Cyclostomata_--Lampreys. - 2. _Pisces_--Fishes. - 3. _Amphibia_--Frogs, Toads, Newts, &c. - 4. _Reptilia_--Snakes, Lizards, Tortoises, &c. - 5. _Aves_--Birds. - 6. _Mammalia_--Mammals. - -The first of these includes only a few species, one of which is found in -our seas, and will receive a short notice here. The fishes will, of -course, demand a fair share of our attention. Amphibians and reptiles -have no British marine representatives, and are therefore quite excluded -from this work. As to the birds, although there are so many that live -entirely on the sea and in its immediate neighbourhood, these have been -so ably dealt with by Mr. Hudson in one of the books of this series that -it would be superfluous to mention them. The mammals include a -considerable number of marine species, but as only one of these--the -Porpoise--is really commonly observed round our coasts, it alone will be -selected for description. - -Lampreys and their few allies were formerly classified with fishes, but -are now made to form a small class by themselves; and there is abundant -reason for the separation. It will be remembered that vertebrates, in -the early stages of their development, are characterised by a -cartilaginous rod running through the dorsal region of the body, below -the central cord of the nervous system, and that they possess a series -of slits opening into the sides of the pharynx. Now, while these -characteristics are usually only transitory in the vertebrates, the -Lampreys and their relatives are the only animals in which they persist -throughout life, and it is for this reason that they are exalted to the -dignity of a class under the title _Cyclostomata_. - -This name signifies 'round-mouthed,' while the Lampreys themselves form -the still smaller division _Marsipobranchii_, which means -'pouch-gilled,' these two being among the most evident characters of the -creatures concerned. They have no true jaws, the circular mouth being -supported by a ring of cartilage, and provided with a rasp-like tongue -that enables them to divide their food. They have no true bone in their -bodies, the simple skeleton, without limbs and ribs, being entirely -cartilaginous, and the rudimentary skull is not movable on the dorsal -cartilage. Their bodies are elongated and eel-like, with a single medial -fin, supported by fine cartilaginous rays, and with seven little slits -on each side of the neck, communicating with as many gills in the form -of little pouches. The mouth is suctorial, presenting, when open, a -circular adhesive disc, by which the animals can attach themselves to -any solid object, but assumes the form of a mere slit when closed. The -young differ from the adult in a few points of structure. Thus they have -no eyes, and the long fin, divided in the adult, is continuous. With the -above characteristics in mind, there will be no danger of confusing the -lampreys with the eels and other similar fishes. - -There are three or four British lampreys, two or three of which inhabit -fresh water. Their habits do not seem to be well understood, but it -appears certain that the Sea Lamprey (_Petromyzum marinus_), which -reaches a length of from one to two feet, ascends rivers to spawn, while -the smaller River Lamprey (_P. fluviatilis_) has been caught in the sea; -and it is probable that the migrations of both, together with the -sojourn of the young of the former for a longer or shorter period in -fresh waters, have been the cause of the widespread confusion between -species. - -Lampreys are carnivorous creatures, and attach themselves to fishes by -their suctorial mouths, and rasp away the flesh. They have also been -known to attack bathers. - - [Illustration: FIG. 226.--THE SEA LAMPREY] - -Passing now to the true fishes, we must first study the general features -of the group by which they are to be distinguished from other animals. -Since there are so many creatures outside this class that are more or -less fishlike in some respects, it becomes no easy matter to give a -concise definition of a fish, and the shortest satisfactory description -must necessarily include several points of structure. Thus, we may -define a fish as a cold-blooded vertebrate that does not undergo -metamorphoses, with limbs modified into fins, possessing also median -fins on the dorsal and ventral surfaces, having distinct jaws, a heart -with two chambers, and breathing by gills. To this we may add that the -young are generally produced from eggs, and that the skin is covered -with scales or bony plates, or is naked. - -But let us now look more closely into the structure of fishes, so that -we may be enabled to see how marvellously they are adapted to their -aquatic life, and in order that we may become acquainted with the few -technical terms which will, as a matter of convenience, be used in the -descriptions of species. - -Taking first the external features, we note that the body is generally -covered with scales, sometimes very large and distinct, but often so -small and closely set that they are not visible without careful -examination; indeed they are often so small, and so thoroughly embedded -in the slimy skin as not to be discovered without the aid of a -microscope. When the scales have unbroken edges and overlap one another -they are said to be _cycloid_, but when the projecting edges are toothed -or serrated, giving a roughness to the touch, they are described as -_ctenoid_. Sometimes the scales are modified into bony plates or little -isolated bony granules, and in either case they are practically -identical in structure with teeth, consisting as they do of dentine, -capped with a little harder substance resembling enamel. - - [Illustration: FIG. 227.--THE PILCHARD - 1. Dorsal fin. 2. Pectoral fin. 3. Pelvic fin. 4. Ventral or anal - fin. 5. Caudal fin.] - -We often observe a row of scales, of a different nature from those -covering the body generally, running along each side of a fish from near -the eye to the end of the tail; and these constitute what is called the -_lateral line_. If we examine these scales closely, we observe that each -one is pierced by a hole that communicates with a little sac beneath -containing a gelatinous material, and in which a nerve tendril -terminates. The presence of the nerve filament evidently denotes that -the scales in question, with the little sacs beneath them, are organs -connected with sensation, and it is also believed that they have -something to do with the secretion of the slimy mucus that covers the -scales of the body. - -The mouth of a fish is generally situated on the extreme front of the -head, but occasionally, as in the sharks and rays, quite on the under -side. If it contains a tongue at all, this organ is of small size and -simple structure; thus it is highly probable that the sense of taste is -very feeble in these animals, and this is just what one might expect -when one remembers that fishes never retain their food in the mouth for -any length of time, but simply bolt it without any attempt at -mastication. - -The arrangement and nature of the teeth are very variable. Often they -are developed on the membrane of the mouth only, in which case they are -generally renewed as fast as they are worn down, but sometimes they are -persistent structures more or less embedded in the bone of the jaws. In -some cases teeth are altogether wanting, but in others they are situated -not only on the jaws, but also on the tongue, the roof of the mouth, and -even on the bony arches that support the gills. - -A glance at the fins of a typical fish will suffice to show that they -may be divided into two groups--the paired fins, representing the two -pairs of limbs in most of the higher animals, and the median fins -occupying the middle line of the body. The former comprise the two -_pectoral fins_ that correspond with our arms, and are attached to the -bones of the pectoral or shoulder girdle; and the _pelvic fins_, -corresponding with the lower extremities. The pectorals, too, are -present in nearly all fishes, while the pelvic pair are rather more -frequently absent than the pectorals. - -The medial fins comprise the _dorsal_, the _ventral_, and the _caudal_ -or tail-fin, and are not to be regarded as limbs, but rather mere -outgrowths of the skin. They are not directly connected with any part of -the main bony framework of the body, though they are generally jointed -with a series of bones (interspinal bones) that run between processes of -the vertebral column. The dorsal and ventral fins are often divided into -two or more parts, and the tail fin is commonly distinctly forked. - -Although the seven fins above mentioned differ considerably in general -form, some being fanlike, while others form fringe-like expansions, yet -they generally agree in that they consist of bony or cartilaginous rays, -between which is a soft membrane. The rays, however, vary much in -character, being sometimes developed into very hard and sharp spines, -and sometimes quite soft and flexible. The fins also differ in function, -as will be seen when we observe the movements of a fish as it swims. It -will then be noticed that the caudal fin, which is spread in the -vertical plane and moved sharply from side to side by the powerful -muscles of the tail, is the chief propelling organ, while the others are -concerned principally in maintaining the balance of the body. This -latter point becomes much more evident when we observe the movements of -a fish in which one or more of the fins have been injured or lost, as we -shall see presently. - -It is true that the pectoral fins are sometimes used to propel, but -forward movement is brought about almost entirely by the caudal fin, -which acts much in the same way as the blade of the propelling 'screw' -of a steam-vessel, the pectorals being used at the same time for -steering. Occasionally, too, the latter are both spread out at right -angles to the body when the fish desires to stop suddenly, and are even -employed at times in swimming backwards. - -When a fish wants to turn to one side, it will be seen to give the tail -a sharp motion to the opposite side. The pectoral of the latter side is -also brought into play, while the other is kept close against the body. - -If the pectoral or pelvic fin of one side is injured, the body of the -fish will incline to the opposite side; and if all the paired fins are -functionless the fish swims with its head inclined downwards. -Observations of fishes in which the dorsal or ventral fins are injured -will also show that these organs are necessary to maintain a steady -motion in the water. - -In addition to the above facts, it may be mentioned here that the paired -fins are often modified into long finger-like processes that serve as -organs of touch, and even as means by which the fish can creep along the -bottom. This is notably the case with gurnards and a few of the other -fishes that spend their time almost exclusively on the bed of the sea. - -Fishes are essentially gill-breathers, the gills being generally -fringe-like organs, supported on bony arches (the gill arches), -numbering four on each side, the cavity containing them being covered by -a gill-cover (_operculum_) that opens behind. Water is taken in at the -mouth, whence it passes into the gill-chamber; and after passing between -and around the gills, it escapes under the opercula. The gills -themselves are richly supplied with bloodvessels that are distributed -close to the surface, and an exchange of gases takes place through their -exceedingly thin walls, carbonic acid gas passing from the blood to the -surrounding water, and oxygen, held in solution in the water, passing -from the water to the blood. - -When fishes are in foul water, containing but little oxygen in solution, -they rise to the surface in order to make up the deficiency by taking -oxygen direct from the air. This, however, is an unnatural proceeding -with the majority of fishes; but there are some that are provided with -accessory breathing organs specially adapted to the extraction of oxygen -direct from the air, and these are so dependent on the supply from this -source that they are suffocated if prevented from reaching the surface. - -In other fishes, such as the sharks and rays, the gills are of an -entirely different character from those described above, for they are -pouch-like and five in number on each side, each pouch communicating -with the pharynx as well as with the exterior by a slit-like opening. - -Before leaving the external characters of fishes we must say a word or -two about their forms and colours. As regards the former, it is well -known that fishes are well adapted for rapid progression through water, -but there are many exceptions to this rule. These exceptions, however, -apply principally to those species that have no need to swim rapidly, -and a study of their habits will show that their form is just as -perfectly adapted to their mode of life. They are often species that -live on the bottom, or hide in the crevices and holes of rocks, and -examples will be given in our future descriptions. - -Variations in colour are even more interesting, especially as they are -so commonly connected with the nature of the surroundings and the -protection of the animals. In nearly all cases the colour is darker on -the upper surface than on the lower, thus making it appear that the -influence of light has something to do with the formation of the -pigments of the skin, and experiment proves that this is, at least to a -certain extent, the case; for when fishes have been kept for some time -in an aquarium into which light is admitted through the bottom only, -pigment spots have formed in the skin on the lower surface. - -Fishes that swim at the surface are generally tinted on the dorsal side -with some shade that closely resembles the colour of the water as viewed -from above, and are white and silvery below. Such colouring is of course -highly protective, for they are not readily distinguished by the sea -birds and other enemies that would pounce on them from above, and are -almost invisible against the sky to eyes below. This form of protective -resemblance is beautifully illustrated in the mackerel, which is barred -on the back with black and green, closely imitating the ripples on the -surface of the deep green sea, while the under side is of a silvery -whiteness that is hardly visible from below with the bright sky as a -background. - -The flat fish afford other interesting examples, for these live on the -bottom, and are coloured above so as to resemble the bed on which they -live; the tints being those of mud, sand, or gravel. - -But what are we to say of the gaudy colours of the gurnards, rock -fishes, &c.? These are certainly not protective in all cases, for we -sometimes find brightly coloured species conspicuous among duller -surroundings. Such instances, however, are comparatively rare, the gaudy -species living principally among the variously coloured rocks, weeds, -and corals; and when they do occur it is probable that they serve -principally as a means by which the brightly coloured sex--usually the -male--attracts its mate. We say 'usually the male,' but why so? Because -the female requires the protection of a more sombre colour in order that -she may with safety deposit her spawn for the perpetuation of her -species. Again, the male referred to needs the assistance of his gaudy -coat only during the breeding season, hence we find that he assumes the -bright colours as a wedding garment, to be cast off when the breeding -season is over. - -This leads us to the subject of changeability of colours in the same -individual. That such changes do occur is well known, and it is still -more remarkable that they are produced in rapid succession, apparently -at the will of the fish concerned; for its tints will vary as it moves -from place to place so as to always harmonise with the surroundings, and -also in response to other conditions. The mechanism by which such -variations are produced has also been studied and explained:--The -colouring matter is held in little vesicles beneath the skin, and these -vesicles are capable of being compressed by muscles quite under the -control of the fish. When they are globular in form the contained -pigment appears dark, but when they are flattened by muscular -compression, the pigment is spread over a much larger area, and thus -greatly reduced in depth of tint. - -As with all vertebrates, the central axis of the internal skeleton of a -fish consists of the backbone and the skull. The structure of the latter -is so complicated, and its description so full of technicalities, that -we deem it advisable to pass it over in a work like this where the scope -is so large in proportion to the space available; and this we do with -reluctance, because the detailed study of the skull is of real -importance to those who would thoroughly understand the principles of -classification. - -The backbone consists of a variable number of cylindrical vertebræ, -united end to end to form a continuous column, both the anterior and -posterior faces of each being concave. On the dorsal surface of each -vertebra there is a V-shaped arch, surmounted by a spine, the former -serving to protect the spinal cord, and the latter giving attachment to -the muscles of the back. Some of the vertebræ are also provided with -processes for the attachment of the ribs, and those of the tail possess -an arch and a spine on the ventral as well as on the dorsal side. - -It has already been shown that the pectoral fins are jointed to a -girdle. This girdle corresponds with the shoulder-blade of higher -animals, and gives direct attachment to the rays of the fin, which may -be regarded as the equivalent of the fingers, and thus there is no part -of the limb corresponding with the arm. The pelvic fins also are -frequently jointed to a pelvic girdle or hip, but this is a very -rudimental structure, or is even entirely absent in some species. - -The rays of the caudal fin articulate with the extremity of the -backbone, but this portion of the fish's anatomy undergoes such -remarkable changes that we must devote a few words to it. It is probably -well known to our readers that the tails of fishes exhibit three -distinct forms. The first of these is a simple fringe formed by the -union of unaltered dorsal and ventral fins; the second is the -unsymmetrical or unequally lobed tail so characteristic of sharks, -dogfishes, and rays; and the third is the broad symmetrical tail fin, -often distinctly forked or bi-lobed, such as we meet with in the -majority of our bony fishes. These three kinds are known respectively as -the _diphycercal_, _heterocercal_, and the _homocercal_ tails. - - [Illustration: FIG. 228.--THE SKELETON OF A FISH (PERCH) - _d_, dorsal fin; _p_, pectoral fin; _v_, pelvic fin; _t_, tail fin; - _a_, anal fin] - -Now, it is an interesting fact that the most ancient fishes of our globe -possessed tails of the first type; and that these gradually gave place -to the heterocercal form; while the higher fishes of the present day -nearly all possess the homocercal tail. Thus as time advanced the -heterocercal tail was gradually evolved from the diphycercal, and the -homocercal from the heterocercal. - -Further, if we watch the development of one of the highest fishes of the -present day from its embryo, we find that similar changes take place in -the individual. At first its tail is a simple fringe round the extremity -of the backbone, the latter being straight, or nearly so, to the end, so -that the embryo fish, as yet still in the egg, reflects a characteristic -of its very early ancestors. Then the end of the vertebral column turns -upward, and strong fin-rays are developed on its ventral side, so that -the tail becomes a heterocercal one like that of the less remote -ancestors of a later geological period. Next, the upward-bending portion -of the vertebral column is slowly absorbed, till nothing of it remains -except a small upturned bony spine, while, at the same time, the ventral -lobe expands on the upper side until the tail fin is once more of a -symmetrical form. - - [Illustration: FIG. 229.--THE INTERNAL ORGANS OF THE HERRING - _a_, oesophagus; _bc_, stomach; _e_, intestine; _l_, duct of - swimming bladder; _k_, air-bladder; _h_, ovary] - -Following these interesting changes, it becomes evident that the -symmetry of the tail fin of the bony fishes is really a false one, the -whole of it having been formed from the ventral lobe of a heterocercal -tail; and although the backbone seems to terminate abruptly exactly -opposite the middle of the fin, it still contains the remnant of the -raised extremity of the backbone that ran to the tip of the dorsal lobe -when the tail was of the heterocercal type. - -The flesh or muscle of fishes is usually white, but it often assumes a -pink colour in the case of those fishes that feed largely on -crustaceans. This is due to the presence of a substance in the horny or -calcareous skins of the crustaceans that is turned red by the action of -the digestive fluids--the same substance that is turned red when the -crustaceans are boiled. This is notably the case with the salmon; but -the red pigment thus derived originally from the crustaceans frequently -shows itself more in the skin of the fish than in the flesh, as -observed in the common red gurnard. - -Most fishes possess a membranous bag containing air, situated just below -the backbone, and known as the air-bladder; but this organ does not -exist in sharks and rays and in some of the heavier bony fishes that -live on the bottom. The air-bladder is capable of being compressed by -the action of certain muscles, and its principal use seems to be the -adjustment of the specific gravity of the fish to that of the -surrounding water; but it is interesting to note that the development of -this air-bladder is precisely the same as that of the lungs of -air-breathing animals, and that in some fishes which live in foul muddy -waters it is really a functional lung by means of which the fishes can -breathe direct from the atmosphere. - -We can find space to refer only to one other internal structure of the -fish, namely, the roe of the female. This usually consists of a very -large number of eggs of small size, sometimes numbering many thousands, -and even millions, in a single individual. So numerous, indeed, are the -eggs, that were it not for the multitudes of carnivorous animals that -devour both eggs and fry, the sea and fresh-water lakes and rivers would -soon become so thickly populated that the fish would die in millions for -lack of food and air. - -In some cases, however, the eggs are much larger and fewer in number, -but these are generally protected from the ravages of predaceous species -by a hard covering, as we shall observe in the sharks and rays. - -Finally, a word or two must be said about the distribution of fishes. We -have already referred briefly to species that live principally at the -surface, and others that make the bottom their home: but some of the -former go to the bottom for food or to deposit their spawn, while some -of the latter occasionally rise to the surface and swim in shoals. We -have noticed, too, that the paired fins of bottom fishes are sometimes -modified into feelers, or into fingerlike processes adapted for -creeping. Similar organs, employed undoubtedly as organs of touch, and -called barbels or barbules, are often developed on the chins or jaws of -these fishes. - -Although we have to deal principally with the species that belong more -or less to the shore--the _littoral_ fishes--we should like to refer -briefly to one or two interesting features of those that live at great -depths. It will be readily understood that much light is lost as the -rays penetrate into deep water, so that the bottoms of deep seas must -be more or less darkened. To allow for this loss, we find that the -species living at moderate depths are provided with larger eyes to -enable them to see their prey and their mates; but at still greater -depths, where the sun's light cannot penetrate, the fishes are either -blind, or are possessed of luminous organs which enable them to see -their way. Again, as the sea is so thinly populated at such great -depths, the carnivorous species do not find abundant food always at -hand, hence they are often provided with such mouths and stomachs as -will allow them to make the best of favourable opportunities, some being -capable of swallowing a fish quite as large as themselves. - -We often find fishes roughly classified into fresh-water and salt-water -species, and although such a division is at times convenient, it must be -remembered that some of the former migrate into brackish and even into -salt water, while some of the latter ascend estuaries and rivers either -for the purpose of obtaining suitable food, or for the deposition of -their eggs. - -The fishes that frequent our coasts may be classified into two main -groups, those with cartilaginous skeletons (_Elasmobranchii_), and the -bony fishes (_Teleostomi_). Both these are divided into family groups, -and we shall deal more or less briefly with all the important families -that include common British marine fishes, but giving more attention to -those species that are truly littoral in habit--species that may be -found in the rock pools or under stones at low tide, and which may be -obtained by the amateur angler working from rocks, piers, &c. - -The cartilaginous fishes include the Sharks, Dogfishes, and Rays. They -have pouchlike gills, five or more on each side, each one opening to the -exterior by a separate slit. The skin generally contains bony elements -that are toothlike in structure and often in form; the mouth is usually -on the under side of the head, and the tail is nearly always of the -heterocercal kind. They are all carnivorous creatures, and often -exceedingly voracious; and are represented in our seas by the Rays and -Dogfishes. - -Rays or Skates (family _Raiidæ_), of which there are six or seven -British species, are readily known by their broad flattened rhomboidal -bodies, with the mouth on the under side of the head, a longitudinal -fold on each side of the tail, and pectoral fins extending quite or -nearly to the front point of the head. - -Two of these fishes are very common in our markets, one being the -Thornback Skate (_Raia clavata_), distinguished by the clawlike spines -down the middle of the back as well as on other parts of the body; and -the Common Skate (_R. vulgaris_), a very voracious species, from two to -four feet long, with a very sharp muzzle. - -All the members of this family are bottom fish, without air-bladders; -and their eggs, which are large and detached, are enclosed in horn -capsules which are so commonly washed up on the beach that they are well -known to frequenters of the sea-side, who call them Skates' Barrows or -Shepherds' Purses. These cases are oblong in form, with a process at -each corner, and the material of which they are composed looks very much -like that of some of the coarser sea weeds after they have been dried in -the sun. As a rule only the empty cases are cast ashore by the waves, -open at the end where the little skate made its escape; but occasionally -we meet with the complete egg, and the case, while still wet, is -sometimes sufficiently transparent to show the form of the embryo -within. - - [Illustration: FIG. 230.--THE EGG-CASE OF DOGFISH] - -Dogfishes are also fairly well known to sea-side ramblers, for not only -are some species used as food in many places, but they are also -frequently to be seen cast aside with the refuse from the fishermen's -nets. The common Spiny Dogfish (_Acanthias vulgaris_), belonging to the -family _Spinacidæ_, frequents all parts of our coasts. It reaches a -length of three or four feet, and is of a slate-blue colour above and -very pale yellow below. The pectoral fins are very large, the ventral -fin absent, and there is a very sharp spine in front of each dorsal. The -creature is ovo-viviparous; that is, the eggs are hatched while still -within the body of the parent. - -Another family (_Scylliidæ_) contains two British species without -spines, and is also characterised by having the first dorsal fin far -behind. They are the Larger Spotted Dogfish (_Scyllium canicula_) also -known as the Nurse Dog and the Bull Huss; and the Lesser Spotted -Dogfish (_S. catulus_), called also the Huss and the Rough Hound. The -egg capsules of both these are occasionally washed on the beach, and -those of the latter species may be known by the yellowish colour and the -long tendrils by which they are anchored to sea weeds. - -In addition to these we may briefly refer to two of the Blue Sharks -(family _Carchariidæ_) that frequent our shores, distinguished by their -long and prominent muzzle, and the crescent-shaped mouth. They may be -regarded as higher in the scale of fish life, as compared with the -sharks and rays previously named, because the vertebræ are more or less -hardened by the deposit of calcareous matter, and, therefore, make a -nearer approach to the character of true bone. The species referred to -are the Common Blue Shark (_Carcharius glaucus_), and the Smooth Hound -(_Mustelus lævis_). The former often exceeds twelve feet in length, and -is commonly seen off our south and west coasts during the summer months. -It is a nocturnal marauder, and is said to sleep at the surface by day -with its tail exposed above the water. The Smooth Hound is a bottom -feeder, subsisting on molluscs and crustaceans, the shells of which are -easily crushed by its flat and blunt teeth. It is a small shark, -measuring only three or four feet in length, and brings forth its young -alive. - - [Illustration: FIG. 231.--THE SMOOTH HOUND] - -The next division (_Teleostomi_) contains all the bony fishes, which may -be distinguished generally from the cartilaginous group by the following -features:--The skeleton is more or less hardened by the deposit of -calcareous matter, and the tail is generally not of the heterocercal -type. The paired fins are fan-like, and the pectoral girdle is attached -to the hinder part of the skull. These fishes generally have an -air-bladder, and the gills lie close together in a cavity covered by an -operculum. The eggs, too, are generally very small and numerous, and -massed together. - -Of these we will take first the family _Salmonidæ_, of which the Salmon -(_Salmo salar_), and the Smelt (_Osmerus eperlanus_) are well-known -examples. Several species of the family are remarkable for their -periodical migrations from fresh to salt water or _vice versa_, and we -cannot do better than briefly relate the interesting life-history of the -salmon as a striking instance of these peculiar wanderings. This fish -quits the sea at the close of the summer, and ascends the rivers for the -purpose of depositing its spawn, the colder water of the rivers being -necessary for the development of the young. Its upward journey is beset -with many difficulties, for it has to shoot the various rapids and leap -the cascades, the latter often demanding the most prodigious efforts on -the part of the fish, which frequently leaps several feet out of the -water, and even then has sometimes to renew its attempts over and over -again before it finally succeeds. Indeed, the difficulties to be -overcome are so numerous that the fish often reaches the goal in such an -exhausted condition that it would hardly be recognised as the salmon by -those who have only seen it in the prime condition in which it is -captured during its return to the sea in the following spring or summer. -The male, at this period called the _kipper_, is of a dull red colour, -irregularly blotched with yellow and light brown, and its skin is -covered with a slimy secretion. Its body is lean, and the head, now -large and out of all proportion, is rendered still more unsightly by the -protrusion of the lower jaw, which at this season, when the males are -particularly pugnacious, becomes a formidable weapon of offence. The -condition of the female, now called the _baggit_, is equally poor, and -the skin has changed its bright silvery colour for dark and dingy -shades. - -The female digs a nest in the form of a deep trench by wriggling her -body in the gravel of the bed of the stream, and there deposits her -eggs, many thousands in number, small quantities at a time. As each -batch is deposited the eggs are fecundated by the kipper, and then -covered over lightly with gravel by the baggit; and this work having -been accomplished, both male and female rest and feed, with the result -that their condition is rapidly improved. - -After about eighteen weeks the eggs begin to hatch, and the fry wriggle -out of the nest and seek shelter under stones in the immediate -neighbourhood. They are now peculiar little creatures, as much like -tadpoles as fishes, with big heads and narrow bodies, and a bag of -albuminous yolk-matter attached to the ventral side. The young subsist -on this store of food for from twelve to twenty days, during the whole -of which time they remain under shelter, having, of course, no need to -expose themselves to the numerous enemies with which they are -surrounded, and they then leave their hiding-place in search of food, -being now about an inch in length. They feed on aquatic and other -insects, which are now becoming plentiful on the approach of the warm -weather; and, growing rapidly, reach a length of four inches in a month -or two. They are now called _parr_, and are distinguished by the dark -bars that cross their bodies transversely--a feature that persists for a -year or more from this time. - -Towards the end of May the parr migrate seawards, accompanied by the -adult salmon, but as their enemies include the voracious fishes, wading -birds, and even the adults of their own species, it is probable that -only a small proportion of the original number ever enter salt water. - -In the sea they feed on crustaceans, molluscs, and small fishes, the -young still growing rapidly, and attaining a weight of about five pounds -in the following autumn, when both young (now called _grilse_) and old -again ascend the rivers to spend the colder half of the year; the former -will have reached a weight of ten pounds or more on their return to the -sea in the following year. - -The Smelt may be seen in thousands in our estuaries during the spring, -for at that time they come up to spawn in the brackish water. In the -summer they swim about in shoals along the coast, and are caught largely -in nets for the market. In some parts they are taken in large shallow -circular nets suspended on a line. This is lowered into the water, and -hauled up when the fish are seen swimming above it. Many amateurs secure -numbers of smelt by means of rod and line, fishing from piers, jetties, -&c. They bite freely at almost any kind of bait, and will snap at an -almost bare hook, with the tiniest fragment of the bait at its point. - -The Herring family (_Clupeidæ_) contains some well-known food-fishes to -which we need only casually refer. They are mostly littoral species, -none inhabiting deep water, and none straying into the open ocean. Their -bodies are covered with silvery scales, and are laterally compressed, so -much so on the ventral side that there is a moderately sharp ridge along -the middle line. The principal fishes of the family are the Herring -(_Clupea harengus_), the Sprat (_C. sprattus_), and the Pilchard (_C. -pilchardus_). - -These fishes are particularly interesting on account of their gregarious -habits and the enormous size of the shoals they form, a single shoal -often containing millions of individuals; and they are often captured in -such quantities that large numbers are sold to farmers as manure to -enrich the soil. The shoals are followed closely by many larger -carnivorous species that devour them in great numbers, as well as by -flocks of sea birds that prey on them, and yet their numbers are not -appreciably reduced by such ravages. They spawn in shallow waters near -the coast, and feed principally on the crustaceans and worms of the -littoral zone. - -Sprats were once considered to be the young of the Herring, but it is -now universally acknowledged that they are a distinct species, and quite -a number of characteristics have been given as a means of distinguishing -between the two. The young of the herring are, however, used largely as -food, for that miscellaneous mixture of fry and small species known as -Whitebait consists largely of these and the young of the sprat. - - [Illustration: FIG. 232.--THE COMMON EEL] - -Herrings are captured principally off the north and east coasts, but the -pilchards, which are often confused with them, and even at times sold -under the same name, are caught chiefly off the coast of Cornwall. - -Although the Eels (_Anguillidæ_) are so readily distinguished by their -general form and appearance, yet it may be advisable to call attention -to one or two of the leading characters that would possibly be -overlooked by an ordinary observer, and in doing this we ask the reader -to note that our remarks apply to the true eels only, and not to the -sand eels and other fish that may be confused with them. - -The elongated bodies of the _Anguillidæ_ are covered with a slimy skin -that is apparently scaleless, but an examination with the microscope -will show that there are small scales embedded in it. The dorsal and -ventral fins extend to the tail, and the pelvics are absent; the -gill-slits, which are very narrow, are at the base of the pectorals. - -It might well be expected that eels would be possessed of some form of -accessory breathing apparatus, seeing that they can live so long out of -water, but this is not the case. They have, however, a pouch-like -gill-cavity which can be inflated and filled with water by the fish, -thus keeping the gills moist and functional. In most other fishes the -gill-chamber is not capable of holding water, and thus the gills soon -become dry and sticky, so that they adhere together and fail to absorb -the necessary oxygen when the fish is out of water. - -Thus the Eel (_Anguilla vulgaris_), in the remarkable migrations for -which it is noted, is capable of travelling over dry land for -considerable distances in search of suitable homes. - -If an eel be taken out of the water, these gill-pouches will be seen to -swell out almost immediately, and remain filled with water as long as -the fish is kept on land; but when it is returned to its natural -element, it will at once discharge the water that kept its gills moist, -and which has become foul with the products of respiration, and, with a -few vigorous gulps, renew the supply. - -Eels spend their breeding season, which extends from July to September, -in salt or brackish waters; and early in the following summer, the -young, which are now called _elvers_, and measure from three to five -inches in length, ascend the rivers, travelling enormous distances and -overcoming obstacles that we might well expect to be insurmountable. -Thus they perform two migrations annually, though it is thought by some -observers that the adult never returns to the sea, but dies soon after -it has deposited its spawn. - -The family of Flat-fishes (_Pleuronectidæ_) present many interesting -points of structure and habit in which they stand alone, the variations -in structure as compared with other fishes being due, of course, to the -habits which they have acquired. - -One of the first features that strike the observer on looking at a -flat-fish is the unsymmetrical form of the body. It is very much -compressed, and the fish having acquired the habit of lying on the bed -of the sea, sometimes on the left and sometimes on the right side, the -lower surface has become flattened more, and is of an almost pure white -colour, while the upper convex side is more or less coloured with -pigment produced by exposure to light. The dorsal and ventral fins are -both very long; and, as is usual with bottom fishes, the swimming or air -bladder is absent. - -Young flat-fish are at first perfectly symmetrical in form, with one eye -on each side of the head, and they swim freely in the water with their -bodies in a vertical plane; but they very soon acquire the habit of -swimming on one side, and the eye of that side slowly passes round to -the other side of the skull, rotating in its orbit as it moves, till at -last both are on the uppermost surface. This, of course, is accompanied -by a considerable distortion of the bones of the skull, which is very -evident in the skeleton of the adult. The young fish then takes to the -bottom, with the result that its under-surface is flattened, while the -upper becomes strongly pigmented. - -These fish spend almost the whole of their time on the bottom, only -occasionally rising for short intervals, when they swim by undulatory -movements of their bodies and fins; their food consists of crustaceans, -worms, and other small marine animals. - -They furnish very interesting illustrations of protective colouring, the -upper surface always closely resembling the ground on which they rest -and feed; and thus they are not only protected from their own enemies, -but are enabled to lie unseen by the animals that form their prey. Those -which live on sandy shores are finely spotted with colours that closely -imitate the sand, while those that lie on mud are of dark and dingy -hues. Others, again, are irregularly marked with spots of various sizes -and colours that resemble a gravelly bottom; and most species are still -further protected by their habit of throwing sand or mud on the top of -their bodies by means of their dorsal and ventral fins. - -Small flat-fishes, especially young Plaice and Flounders, live so close -to the shore that they are often left behind in rock pools and sandy -hollows by the receding tide, and it is very interesting to observe the -habits of these in their natural conditions. It will generally be -noticed that it is most difficult to detect them while they are at rest; -and when disturbed, they usually swim but a short distance, settling -down very abruptly, and immediately throwing a little sand over their -bodies by a few vibrations of their fins. - -Another peculiarity of some of the flat-fishes is their indifference to -the nature of the water in which they live. Flounders may not only be -caught in the estuaries of our rivers, but they even ascend to, and -apparently live perpetually in, perfectly fresh water. In many -instances they may be seen miles from the sea, and even flourishing in -little fresh-water streams only a few feet in width. Thus they may be -found in numbers in the upper waters of the small rivers of the Isle of -Wight and of many streams of the mainland. - -The principal British flat-fishes are the Plaice (_Pleuronectes -platessa_) and Flounder (_P. flexus_) above mentioned, and also the Sole -(_Solea vulgaris_), the Lemon Sole (_S. aurantiaca_), the Turbot -(_Rhombus maximus_), and the Halibut (_Hippoglossus vulgaris_); and as -all these are well-known food-fishes it is hardly necessary to describe -them. - - [Illustration: FIG. 233.--THE LESSER SAND EEL] - -Sand Eels (family _Ophidiidæ_) resemble the true eels in the general -form of their elongated bodies, but may be readily distinguished by -their bright silvery colour, the large gill-openings, and the more -strongly developed dorsal and ventral fins, the former of which extends -almost along the whole length of the back. The lower jaw is also longer -than the upper. - -Two species are to be found on our shores--the Lesser Sand Eel -(_Ammodytes tobianus_), and the Greater Sand Eel (_A. lanceolatus_), the -former attaining a length of six or seven inches, and the latter nearly -three times this size. They may be seen off the south coast, swimming in -shoals over sandy bottoms, and when disturbed they descend and burrow -into the sand with remarkable agility. They approach the shore so -closely that they are often washed up by the waves, but immediately -disappear into the sand; and large numbers commonly remain behind as -the tide recedes, burying themselves to the depth of a few inches, and -are dug out by fishermen for bait. - -The smaller species is by far the more common, and is taken in large -numbers by means of the draw net to be sold as food. It is particularly -abundant at Teignmouth, where it is known as the Sand Sprat, and forms -an important article of diet. - -Quite a number of our important food-fishes belong to the Cod family -(_Gadiadæ_), and although some of these are caught almost entirely in -deep water some distance from shore, others give employment to the -angler fishing from rocks, piers, and jetties. - -In all, the gill-openings are very wide, and the body is covered with -small overlapping scales. The caudal fin is quite free, the dorsal is -generally divided into three distinct parts which extend over the -greater part of the back, and the ventral fin is also frequently -divided. - - [Illustration: FIG. 234.--THE THREE-BEARDED ROCKLING] - -The typical species--the Cod (_Gadus morrhua_)--is too well known to -need a description, and although it is a large fish, often measuring -four feet and more, it approaches so close to the shore that it may be -caught with a hand line thrown out from rocks or piers. The barbel -projecting from the chin denotes that it is a bottom feeder. - -On the rocky coast of the south the Pollack or Pollock (_G. pollachius_) -is very abundant, and may be taken with rod and line from the shore. It -also enters estuaries in large numbers, and may be caught close to quays -and jetties. This species is a very free biter, and will take almost any -of the baits used for sea fishing. It has no barbel. - -The same genus includes the Whiting (_G. merlangus_), distinguished by a -black spot at the base of the pectoral fin and the absence of barbels; -the Whiting Pout (_G. luscus_), with a similar black spot at the base of -the pectorals, also dark, transverse bands, and a barbel; and the -Haddock (_G. æglefinus_), with a black patch on either side above the -pectorals, and a dark lateral line. The family also includes the Ling -(_Molva vulgaris_) and the Hake (_Merluccius vulgaris_), both of which -are caught in deep water; and the Rocklings (genus _Motella_), three -species of which frequent our rocky shores. - - [Illustration: FIG. 235.--THE SNAKE PIPE-FISH] - -The last mentioned are interesting little fishes that may be found on -stony beaches at low tide, for they often remain under cover between the -tide-marks, and may be seen on turning over stones and weeds. Perhaps -the commonest of them is the Five-bearded Rockling (_M. mustela_), which -has four barbels on the upper lip and one on the lower. It is of a -dark-brown colour above, and light below, and makes nests of corallines -in rock cavities. The Three-bearded Rockling (_M. tricirrhata_), known -also as the Sea Loach and the Whistle-fish, is a larger species, -sometimes reaching a length of a foot or more. Its colour is light -brown, marked with darker spots, and, like the other species, it lives -in the shallow water of rocky and weedy places. Another species--the -Four-bearded Rockling (_M. cimbria_), known by the three barbels on the -upper lip and one on the lower, is about eight inches long when full -grown, and is found principally on the northern shores. - -Our next family (_Syngnathidæ_) contains some peculiar creatures called -Pipe-fishes because their jaws are united into a tube. They have long -and slender bodies that are covered with bony plates which form a kind -of coat of mail and give them an angular form. They have very small -gill-openings, a single dorsal fin, and no pelvics. - -Pipe-fishes are very sluggish in habit, swimming but little, and living -in the shelter of weeds and stones on rocky coasts. In fact, they are -not adapted for swimming, and their attempts at this mode of locomotion -are awkward in the extreme, for their bodies are rigid and the tail very -small. When removed from their hiding-places they move but little, and -look as much like pieces of brown or greenish wood as fishes; and their -rigid bodies are so completely encased in the bony plates that they -alter but little in appearance when dried, and consequently the dried -specimens are often seen in museum collections. - -All the British species, four in number, are small fishes, inhabiting -the shallow water of rocky shores, and are often found hiding under -stones near low-water mark. The largest is the great Pipe-fish or -Needle-fish (_Syngnathus acus_), which grows to a length of about -fifteen inches; and the smallest is the Worm Pipe-fish (_S. -lumbriciformis_), which is of an olive-green colour, and has a short, -upturned snout. The Lesser Pipe-fish (_S. typhle_), also known as the -Deep-nosed Pipe-fish, is very abundant on nearly all rocky coasts, and -may be distinguished from the others by having the ridge on the tail -continuous with the lateral line and not with the dorsal angle. The -other species is the Slender-nosed Pipe-fish or Snake Pipe-fish -(_Nerophis ophidium_), the body of which is extremely slender, and the -tail long and narrow. The male is provided with a series of small, -cup-like cells, in each of which he carries an egg. - -In all the bony fishes previously mentioned the fin rays are soft and -flexible, and in this respect they differ from those that are to follow, -for the remaining families are all characterised by the presence of one -or more sharp rigid spines on the dorsal fin, and often by similar -spines on other fins. They constitute the group of Spiny-finned fishes. - -Of these we shall first take the prettily coloured Wrasses (family -_Labridæ_), which live in the holes of rocks and under the cover of -weeds on rugged coasts. These fishes are very voracious in habit, and -the sea angler will find that they are ready to seize almost any bait -that may be offered them, and even to attack almost everything that -moves within sight; but they are likely to give much trouble since they -will rush into the crevices of rocks or among large weeds when hooked, -and thus frequently lead to the breaking of the line. - -Wrasses feed principally on molluscs and crustaceans, and are provided -with extensile telescopic lips that enable them to pull the former from -the rocks on which they creep, and the latter from their hiding-places -among the rocks. They have also strong teeth in the gullet, by which -they can crush the shells of their prey. - -There are several British species of Wrasses, one of which is shown in -the accompanying illustration. The commoner ones are known to fishermen -and juvenile anglers by quite a variety of local names. - - [Illustration: FIG. 236.--THE RAINBOW WRASS (_Labrus julis_)] - -The family _Gobioesocidæ_ contains some small and very prettily coloured -fishes of very peculiar habits, known popularly as Sucker-fishes. They -have one or two adhesive suckers between the pelvic fins by which they -attach themselves to rocks, stones, and shells. Some are littoral -species, and may be searched for at low tide; but others inhabit deeper -water, and are seldom obtained without a dredge. - - [Illustration: FIG. 237.--THE CORNISH SUCKER] - -One of the former is the Cornish Sucker (_Lepadogaster cornubiensis_), -which may sometimes be taken in a hand net by scraping the rocks and -weeds at low tide on the south-west coast. It has two suckers, each -circular in form, surrounded by a firm margin, within which is a soft -retractile centre. This central portion is attached to muscles by which -it can be withdrawn; and a vacuum is thus produced, so that the sucker -adheres by atmospheric pressure. The structure of the sucking organs can -be seen to perfection when the fish attaches itself to the side of a -glass aquarium, and if it be taken in the hand it will cling quite -firmly to the skin. - -This peculiar little fish is only about three inches long, and its broad -head is marked with two conspicuous purple spots, with a blue dot in the -centre, and surrounded by a yellowish ring. - -The allied species include the very small Two-spotted Sucker (_L. -bimaculatus_), which is of a bright red colour, and adheres to stones -and shells in deep water; the Sea Snail (_Cyclopterus liparis_), about -four or five inches long, with a soft and slimy semi-transparent body; -and Montagu's sucker (_C. Montagui_), which is usually under three -inches in length, and may be distinguished by its peculiar habit of -curling the body laterally when at rest. - -Equally interesting are the little Sticklebacks (family _Gastrosteidæ_), -the fresh-water representatives of which are known to almost everyone. -Their pugnacious habits, the bright colours assumed during the breeding -season, and the wonderful nests which they build for the protection of -their eggs and young, have all served to make them popular with those -who take interest in the forms and ways of animals. They are, moreover, -such hardy creatures that they may be kept alive for a considerable time -in any well-managed aquarium. - - [Illustration: FIG. 238.--THE FIFTEEN-SPINED STICKLEBACK AND NEST] - -In this family the hindmost portion of the dorsal fin is soft-rayed, but -the front portion is represented by a row of strong, sharp, erectile -spines, which constitute a formidable weapon of offence and defence. -Most of the species live in fresh water, but all the members of the -family seem to be able to live almost equally well in both salt and -fresh water. - -We have one marine species--the Sea Stickleback or Fifteen-spined -Stickleback (_Gastrosteus spinachia_), which may be caught on rocky and -weedy coasts. It derives one of its popular names from the presence of -fifteen spines along the middle of the back. Its tail is long and -narrow, and its snout elongated, with the under jaw projecting beyond -the upper. - -The nest of this species is a pear-shaped mass of soft sea weeds and -corallines, all bound together by a silky secretion, and suspended to -the rock in a sheltered spot. Within this the female deposits her eggs -in little clusters, all of which are bound together and to the nest -itself by the silk. If the nest is damaged while occupied, it is -immediately repaired, the male, it is said, taking upon himself the -responsibility of this task. - -Sand Smelts (family _Atherinidæ_) resemble the true smelts previously -described, but may be readily distinguished by the anterior dorsal fin, -which is small and spinous. We have two species of this family, of which -_Atherina presbyter_ is by far the more common. It is a very pretty -fish, about five inches long, with a broad silvery stripe along each -side. It is very common on the sandy coasts of the south, where it also -enters the brackish waters of estuaries. Young anglers catch them in -considerable numbers by means of rod and line; but the professional -fisherman, taking advantage of the fact that sand smelts swim in shoals, -captures them in large, round, shallow nets. The net is baited with -bread, crushed mussels, or offal of almost any kind, and is then lowered -several feet below the surface by means of a long pole, to the end of -which it is suspended. It is raised to the surface at short intervals, -and will often enclose dozens of fish in a single haul. - -The shallow waters of our southern coasts, including the estuaries and -harbours, are also frequented by the Grey Mullet (_Mugil capito_), of -the family _Mugilidæ_. This fish may be distinguished from other similar -species by the four stiff spines of the front dorsal fin, and by the -absence of a lateral line. The mouth is small, and without teeth, and -the mode of feeding is somewhat peculiar. The food consists of worms, -molluscs, and various organic matter contained in the sand or mud of the -bottom. It is sucked into the mouth, together with more or less of the -mud and sand, and the former is strained through a special straining -apparatus situated in the pharynx. - -The Grey Mullet may be taken with rod and line, and bites freely when -the rag-worm is employed as bait. It is often taken in the fisherman's -drag net; but, being a splendid jumper, it frequently makes its escape -as the net is drawn on the beach. - -Few of our littoral fishes are so well known as the Little Blennies -(family _Blenniidæ_), which are to be found hiding amongst the weeds in -almost every rock pool, and under stones as they await the return of -the tide. Their bodies are generally cylindrical, and are either naked -or covered with very minute scales. The dorsal fin runs along the whole -length of the back, and each pelvic has one spine and two soft rays. -When taken out of the water the gill-cavities widen considerably, and -the eyeballs will be seen to move independently of each other, like -those of the chamæleon. - -Most of the blennies are very active and voracious fishes, often giving -considerable trouble to the angler when fishing with a rod among the -rocks. They will bite at almost anything that moves, and, completely -swallowing the angler's hook, will immediately rush into a crevice from -which it is often difficult to remove them. - -Most of them have tentacles on the head by which they assist their -movements among the rocks and stones; and some actually creep up the -rugged surfaces of rocks by means of their ventral fins. They can all -live for a long time out of the water, being able to retain a supply of -water in their expanded gill-chambers to keep the gills moist. - - [Illustration: FIG. 239.--THE SMOOTH BLENNY] - -The Smooth Blenny or Shanny (_Blennius pholis_) is one of the commonest -species. It reaches a length of four or five inches, and has no -tentacles on the head. The Eyed Blenny or Butterfly Blenny (_B. -ocellatus_) may be distinguished by the conspicuous spot on the spinous -portion of the dorsal fin. The Large Blenny (_B. gattorugine_) inhabits -deeper water, chiefly off the south-west coast, and reaches a length of -a foot or more. The Crested Blenny (_B. cristatus_) is named from the -small crest on the head which can be raised and depressed; and the -Viviparous Blenny (_Zoarces viviparus_), as its name implies, brings -forth its young alive. The last species often exceeds a foot in length, -and is found principally on the north and east coasts. The newly-born -young are so transparent that the circulation of the blood within the -body may be seen under the microscope quite as easily as in the web of -the frog's foot and in the tail of the tadpole. - -One very common species of the _Blenniidæ_ differs considerably in -general form from the others, its body being elongated and eel-like, but -much compressed laterally. We refer to the Butterfish or Butter Gunnel -(_Blennius gunellus_), which is often mistaken for a small eel by young -sea-side naturalists. It is exceedingly common under stones at low tide, -and may be recognised at once by the light rectangular spots along the -flattened sides of the body. It is quite as slippery and as difficult to -hold as the eel itself. - -It will be interesting to note that the ugly Sea Cat or Wolf-fish -(_Anarrhichas lupus_), which is sometimes sold for food in our large -towns, is also a member of the blenny family. It is a powerful, -rapacious fish--a veritable wolf of the sea, always ready to attack -anything. It feeds on molluscs and crustaceans, the shells of which are -easily reduced between the powerful crushing teeth that line the jaws -behind the formidable canines. - - [Illustration: FIG. 240.--THE BUTTERFISH] - -The Gobies (_Gobiidæ_) form another interesting family of small littoral -fishes, easily distinguished by the fact that the ventral fins are -united in such a manner that they enclose a conical cavity. The first -portion of the dorsal fin has also six flexible spines. The Spotted Goby -(_Gobius minutus_) is commonly to be found on sand-banks, where it is -well protected by the colouring of its upper surface, which closely -resembles that of the sand on which it rests. It is said to make a nest -by cementing fragments together round some little natural hollow, or to -utilise an empty shell for a similar purpose, fixing the shell to the -surrounding bed, and constructing a tunnel by which it can enter or -leave. The eggs are deposited in this nest, and the male keeps guard -over the home. The Black or Rock Goby (_G. niger_) inhabits rocky -coasts, clinging to the rocks by means of a sucker formed of the -modified pelvic fins. - -A brightly coloured fish known as the Dragonet (_Callionymus lyra_) is -sometimes classed with the Gobies, though its pelvic fins are not -united. It is not a well-known species, and is seldom obtained except -with the dredge, as it inhabits deep water. - - [Illustration: FIG. 241.--THE BLACK GOBY] - -A peculiar little fish called the Pogge or Hook-nose (_Agonus -cataphractus_), also known as the Armed Bull-head, is commonly taken in -shrimpers' nets on the south and east coasts. Its head and body are very -angular, and are covered with an armour of keeled scales. It seldom -exceeds six inches in length, and is classed with the Flying Gurnards in -the family _Dactylopteridæ_. - - [Illustration: FIG. 242.--THE FATHER LASHER] - -The true Gurnards and the Sea Bullheads form the family _Cottidæ_. -Several species of the former are included among our food-fishes, and -are therefore more or less familiar to our readers. They are -characterised by their large, square, bony heads, and by the finger-like -rays of the pectoral fins which are used as organs of touch and for -creeping along the bottom of the sea. The Bullheads are represented by -the peculiar Father Lasher or Sting Fish (_Cottus bubalis_), which is -very common on our rocky coasts and is frequently captured in shrimp -nets. Its head and cheeks are armed with sharp spines which constitute -formidable weapons of offence. When taken out of the water it distends -its gills enormously; and, unless very cautiously handled, its sharp -spines may be thrust deeply into the flesh. Young specimens, with -imperfectly developed spines, may be seen in almost every rock pool, and -the full-grown fish is easily taken with rod and line by fishing in the -deep gulleys between the rocks. - -The remarkable Angler Fish (_Lophius piscatorius_), known also as the -Fishing Frog and the Sea Devil (family _Lophiidæ_) is sometimes taken -off the coasts of Devon and Cornwall; and although it cannot be truly -described as a littoral species, its structure and habits are so -peculiar that it deserves a passing notice. It is an ugly fish, with an -enormous head, a short naked body, and a comparatively slender tail. The -mouth is very capacious, sometimes measuring over a foot from angle to -angle, and is directed upwards. The scaleless body is furnished with -numerous slender filaments that resemble certain filamentous sea weeds, -and these together with the dull colouring of the body generally enable -the fish to rest unobserved on the bottom. The front portion of the -dorsal fin is on the head and fore part of the body, and consists of a -series of six tentacles, three long ones on the top of the head and -three shorter just behind them; and the foremost of these, which is the -longest, terminates in a little expansion which is kept in constant -movement by the fish. The mouth is armed with rasplike teeth which can -be raised or depressed at will, and when raised they are always directed -backward; the eyes are directed upward, and the gill-openings are very -small. - -This strange creature habitually rests on the bottom of the sea, -disguised by its filamentous appendages and adaptive colouring, dangling -the expanded extremity of its first dorsal filament just over its -upturned cavernous mouth. It does not swim much, indeed it is at the -best but a bad swimmer; and when it moves it simply shuffles its heavy -body along the bottom, gliding between the stones and rocks, where it -may remain unobserved, its movements being produced by the action of the -tail, and of the paired fins, which are better adapted for walking than -for swimming. Unwary fishes, attracted by the dangling of the angler's -bait, approach the watchful monster, and while speculating on the nature -of the bait, are suddenly engulfed in the capacious mouth, from which -there is no escape on account of the backward direction of the teeth. - -The family _Trachinidæ_ contains the fishes known popularly as the -Stargazers and the Weavers. These are small, carnivorous species, with -rather elongated bodies, terminating in tail fins that are not forked. -The first dorsal fin is distinct and spinous, and the spines, as well as -others that are developed on the gill-covers, are grooved for the -passage of a poisonous fluid that is secreted at their bases. - -Our littoral species include two well-known fishes (the Greater and -Lesser Weavers) that are dreaded by fishermen on account of the very -painful wounds they are capable of inflicting, and the smaller of the -two is also a considerable annoyance to bathers on certain sandy coasts. - - [Illustration: FIG. 243.--THE LESSER WEAVER] - -The Greater Weaver (_Trachinus draco_) lives at the bottom of deep -water, and is often dredged up in the trawl. Some fishermen call it the -Sting Bull, and always take the precaution of cutting off the poisonous -spines before disposing of the fish. It lives on the bottom with its -mouth and eyes directed upward, always in readiness to seize its unwary -prey, and the sharp spines of the dorsal fins are kept erect for the -purpose of promptly attacking approaching foes. Its mouth and palate are -armed with sharp teeth which render the escape of its prey almost -impossible. The smaller species (_T. vipera_) seldom exceeds six inches -in length. It lives in shallow water on sandy coasts, with dorsal spines -erect; and the wounds it produces on the unprotected feet of bathers are -often exceedingly painful on account of the injected poison, which also -causes the part to swell and turn to a dark purple colour. - -The remaining important families, although they contain well-known -British food-fishes, do not include littoral species, and for this -reason we shall pass them over with but brief notice. - -The Mackerel (_Scomber vernalis_) belongs to the family _Scomberidæ_, -and is so well known that no description need be given for the purposes -of identification. We have already referred to it as a beautiful -illustration of protective colouring, its upper surface resembling the -ripples of a deep green sea and the lower the brightness of the sky. -Mackerel swim in shoals in the open sea, pursuing and devouring the fry -of herrings and other fish; and in order that they may be enabled to -cover enormous distances their muscles are richly supplied with blood. -This not only gives a pinkish colour to the flesh, but results in a -greater amount of oxidation and the maintenance thereby of a body -temperature several degrees higher than that of the surrounding water. -We would also call attention to the five or six small fins behind the -dorsal and anal fins as characteristic of the _Scomberidæ_. - -Our next family (the _Cyttidæ_) contains the John Dory (_Zeus-faber_), -concerning which some superstitions are still prevalent in parts. It is -brightly coloured, but not graceful in form, and is often caught in -large numbers off the coasts of Devon and Cornwall. Some fishermen call -it the Cock, on account of the crest on the back; while others know it -as St. Peter's Fish, and will point out the impression of the Apostle's -finger on each side--a black spot surrounded by a light ring. - -The Horse Mackerel (_Caranx trachurus_) is found principally in the same -parts, where it devours the fry of other fishes. It is not a very close -relative of the common mackerel, but belongs to a distinct family -(_Carangidæ_), of which it is the only British representative. It is a -carnivorous fish, easily distinguished from _Scomber_ by its conical -teeth, as well as by the bony plates of the lateral line, the posterior -of which are keeled or spined. - -While the last-mentioned families contain only fishes of truly pelagic -habits, the next (_Sparidæ_), formed by the Sea Breams, generally keep -near the coast, and often enter fresh waters. In these the body is much -compressed laterally, and is covered with large scales; the first half -of the dorsal fin is also spinous. The Common Sea Bream (_Sparus -auratus_), characterised by its red colour with brilliant golden -reflections, and by a dark spot on the shoulder, may often be angled -from rocks and piers. The young, in which the dark spots have not yet -appeared, are known as Chads, and are often regarded as a distinct -species. The Black Bream (_Cantharus lineatus_) is an omnivorous feeder, -and will take both animal and vegetable baits. - -The Red Mullets (family _Mullidæ_) may be distinguished from the grey -mullets previously described by the two long erectile barbules on the -lower jaw. The scales are large and thin, with serrated edges, and the -front portion of the dorsal fin has weak spines. The common British -species (_Mullus barbatus_) frequents our south and east coasts, being -specially abundant round Devon and Cornwall, where they often occur in -vast shoals, and the young are often to be caught in estuaries and -harbours. - -Our last example is the Common Bass or Sea Perch (_Morone abrax_), of -the family _Serranidæ_. It is also known locally as the White Salmon -and the Salmon Dace. This fish may be taken with rod and line on rocky -coasts and at the mouths of rivers. The sand-eel, or an artificial -imitation of it, is commonly used as bait, but the Cornish fishermen -more frequently employ a piece of herring or pilchard for the purpose. -The first dorsal fin of this fish has very strong spines which may -inflict severe wounds when the live creature is carelessly handled. - - * * * * * - -Omitting all mention of sea birds, for the reason previously given, we -now pass to the highest division of vertebrates--the Mammals--of which -we shall describe but one species--the Common Porpoise, this being the -only marine mammal that can be regarded as a frequent visitor to the -British coasts in general. - -It may be well at the outset to understand exactly why the porpoise is -classed with the mammals and not with the fishes--to see how its -structure and functions correspond with those of our own bodies rather -than with those of the animals dealt with in the preceding portion of -the present chapter. - -First, then, while the young of fishes are almost invariably produced -from eggs and are not nourished by the parents, the young of the -porpoise are produced alive, and are nourished with milk secreted by the -mammary glands of the mother. This is an all-important feature, and is -the one implied in the term _mammal_. The porpoise also differs from -nearly all fishes in that it breathes by lungs instead of gills, -obtaining its air direct from the atmosphere, and not from the water. -Hence we find it coming to the surface at frequent intervals to -discharge its vitiated air and to inhale a fresh supply. The body-cavity -of a mammal is divided into two parts by a muscular diaphragm, the -foremost division, called the thorax, containing the heart and lungs, -and the other (the abdomen) the remainder of the internal organs, while -the diaphragm itself plays an important part in the respiratory movement -by which air is drawn into the lungs. The body of the porpoise is so -divided, but no such division ever occurs in any of the fishes. Lastly, -the heart of the porpoise, in common with the rest of the mammals, is -divided into four cavities, and the blood is warm, while the heart of a -fish has generally only two divisions, and the blood propelled by it is -of about the same temperature as that of the surrounding medium. Several -other important differences between the porpoise and the fish might be -given, but the above will be quite sufficient to show why they are -placed in different classes. - -Mammals are divided into several classes, and one of these (_Cetacea_) -includes the fish-like Whales, Porpoises, and Dolphins, all of which are -peculiarly adapted to a purely aquatic life. Like most of the fishes, -their upper surfaces are of a dark colour, and the lower very light. -Their fore limbs are constructed on the same plan as those of the higher -mammals, the bones of the arm being attached to a large shoulder-blade, -and the hand formed of four or five well-developed fingers which are -enclosed in skin, so that they constitute a paddle or flipper well -adapted for propulsion through water. There is no collar-bone, however, -and the fingers have no nails or claws. There are no hind limbs visible -externally, but a rudimentary pelvic girdle forms a part of the internal -skeleton. A dorsal fin exists, but this is merely an extension of the -skin of the back, and is not supported by either bones or rays. The skin -itself has no scales, like that of most fishes, but is smooth and naked; -and below it lies a large amount of fat, which, being a very bad -conductor of heat, serves to prevent the escape of heat from the body. - -The tails of cetaceans are also mere folds of the skin, supported in the -centre by the extremity of the vertebral column; but unlike the tail -fins of fishes, they are expanded horizontally instead of in the -vertical plane. This latter is an important adaptive feature of the -cetaceans, since the vertical movement of a tail so disposed is exactly -what is required to assist the animals as they alternately rise to the -surface for air and again descend into the sea in search of their food. - -Among the other external characters of the cetacean we may note the -nostrils, which are always situated on the highest point of the head, -and are thus the first part exposed when the creature rises to renew its -supply of air; also the ears, which are two small apertures behind the -eye, without any form of external appendages. - -The skeleton of the cetacean is formed of light spongy bones, saturated -with oily matter; and although the animal has no true neck, visible as -such externally, it is interesting to note that, in common with all -other mammals, even with the long-necked giraffe, it possesses its seven -cervical or neck vertebræ. - -Porpoises and Dolphins together form the family _Delphinidæ_, -characterised by having the blow-hole in the form of a crescent with its -convexity turned towards the front, and of these the Porpoises -constitute the genus _Phocæna_. - -The Common Porpoise (_P. communis_) is the species that is so often -seen close to our shores and in the harbours and estuaries, swimming in -shoals with a graceful undulatory movement. Porpoises move forward -entirely by the vertical action of their powerful horizontal tails, and -extend their flippers only to change their course or to arrest their -progress. At short intervals they rise to the surface, exposing their -slate-coloured backs and dorsal fins for a moment, and then immediately -dive downwards in such a manner as to appear to turn a series of -somersaults. Occasionally they will leap quite out of the water, -exhibiting their white under surfaces, which shine with a sudden flash -when illuminated by the rays of a bright sun. The blow-hole is the first -part exposed, and if one is sufficiently near the shoal a fountain of -spray may be seen to shoot into the air, and the outrush of the expired -air may be heard as each one makes its appearance. - - [Illustration: FIG. 244.--THE COMMON PORPOISE] - -The true nature of the spouting of a cetacean seems to be very generally -misunderstood, the fountain of spray produced at each exhalation giving -the idea that the animal is expelling a quantity of water from its -nostrils. This, of course, is not the case; for the cetacean, being an -air-breather, has no need to take in a supply of water, as the -gill-breathing fishes have. Air only is expelled through the nostrils; -but as the expiration sometimes commences before these apertures are -brought quite to the surface, a certain amount of water is shot upwards -with the expired air; and even if the expiration commences after the -nostrils are exposed, the small quantity of water they contain is blown -into a jet of spray; and in a cool atmosphere, the density of this is -increased by the condensation of vapour contained in the warm and -saturated air from the lungs of the animal. It will be noticed, too, -that the creature does not check its course in the least for the purpose -of respiration, the foul air being expelled and a fresh supply taken in -exchange during the short time that the blow-hole remains above the -surface of the water. - -The Common Porpoise measures five or six feet in length, and subsists on -pilchards, herrings, mackerel, and other fish, the shoals or 'schools' -of which it pursues so closely that it is often taken in the fishermen's -nets. Its flesh was formerly eaten in our own country, but it is now -seldom hunted except for its oil and its hide. About three or four -gallons of the former may be obtained from each animal; and the latter -is highly valued on account of its durability, though it should be known -that much of the so-called porpoise-hide manufactured is really the -product of the White Whale. - - - - - CHAPTER XV - - _SEA WEEDS_ - - -We now pass from the animal to the vegetable kingdom, our object being -to give a general outline of the nature and distribution of the -principal marine algæ or sea weeds that grow on our shores; and to -supply a brief account of those flowering plants that either exhibit a -partiality for the neighbourhood of the sea, or that grow exclusively on -the rocks and cliffs of the coast. The present chapter will be devoted -to the sea weeds themselves, but we consider it advisable to precede our -account of these beautiful and interesting plants by a brief outline of -the general classification of plant-life, in order that the reader may -be able to understand the true position of both these and the flowering -plants in the scale of vegetable life. - -Plants are divided into two great groups, the _Cryptogams_ or Flowerless -Plants and the _Phanerogams_ or Flowering Plants. In the former the -reproductive organs are not true seeds containing an embryo of the -future plant, but mere cells or _spores_, which give rise directly to a -thread or mass of threads, to a cellular membrane, or to a cellular body -of more or less complexity of form from which the flowerless plant is -afterwards developed; while in the latter the reproductive organs are -flowers that give rise to true seeds, each of which contains the embryo -plant. - -The _Cryptogams_ are subdivided into four groups--the _Thallophytes_, -the _Charales_, the _Muscineæ_, and the _Vascular Cryptogams_. - -The first of these includes all the very low forms of vegetable life, -the simplest of which (_Protophyta_) are minute plants, each consisting -of a single microscopic cell that multiplies by a process of budding, no -sexual organs of any kind being produced. Some of these minute -unicellular organisms contain chlorophyll--the green colouring matter of -plants, by the action of which, under the influence of light, the plant -is enabled to decompose the carbonic acid gas of the atmosphere, using -the carbon for the purpose of building up its own substance, and setting -free the oxygen into the air again. Others contain no chlorophyll; and -these, having no power of feeding on carbonic acid gas, are more or less -dependent on organic matter for their supplies of carbon. - -Only very slightly removed from these minute plants are the _Algæ_ of -fresh and salt water, varying in size from microscopic dimensions to -enormous plants, the lengths of which may reach many yards and the -weight several stone. They contain chlorophyll, and can therefore avail -themselves of inorganic food material; and although some multiply only -by repeated subdivision of their cells, others develop sexual organs by -the union of which fertilised spores are formed. The nature of these -Algæ will be more fully described presently; and we will go no further -now than to justify the location of such large and conspicuous plants -(as many are) so low in the scale of vegetable life by stating that they -are entirely cellular in structure, never producing true vessels such as -we see in higher plants; and that though some of them develop parts -which more or less resemble the leaves and roots of higher forms, the -former are far more simple in structure and function than true leaves -and the latter are never engaged in the absorption of food from the soil -to which they are fixed. - -Another important group of the _Thallophytes_ is formed by the _Fungi_, -which include the familiar mushrooms, toadstools, and the sap-balls so -commonly seen on decaying trees; also the smaller forms known as moulds, -mildew, and smut. These, also, are entirely cellular in structure; and, -since they develop no chlorophyll, are compelled to live as parasites on -living beings or to derive their food from decaying organic matter. Thus -they are the creatures of corruption, their presence always denoting the -breaking down of living matter or of matter that has previously lived. - -Now leaving the _Thallophytes_, and passing over the small group of -aquatic plants known as the _Charales_, we come to the _Muscineæ_, which -contains the Liverworts (_Hepaticæ_) and the Mosses (_Musci_). - -The plants of both these groups require much moisture, and are found -principally in damp, shady situations. Like the preceding groups they -are cellular in structure, never producing true vascular bundles such as -the higher plants possess; and their life histories are rendered -interesting by the 'alternation of generations' which they exhibit. The -first generation is a sexual one produced from the spores, and consists -either of a mass of delicate threads from which a plant with a leafy -axis is developed by a process of budding, or of a little green frond -(the _thallus_). These bear the male and female elements, called -respectively the _antheridia_ and the _archegonia_; and when the central -cells of the latter are fertilised by the former, they give rise to a -case, with or without a stalk, containing a number of spores. When the -case is ripe, it opens horizontally by means of a lid, thus liberating -the spores. - -Following these in the ascending scale are the _Vascular Cryptogams_, in -which some of the cells become modified into true vessels. Here, too, -the plants exhibit a distinct alternation of generations, the spore -first giving rise to a small, leafless body, the _prothallium_, which -bears the sexual organs; and then the female elements, after -fertilisation, produce the spore-bearing plant. - -This group contains quite a variety of beautiful and interesting plants, -including the Ferns (_Filicales_), Horsetails (_Equisetales_), -Club-mosses (_Lycopodiales_), Water Ferns (_Rhizocarpeæ_), and -_Selaginellales_. - -Ferns usually produce their little green prothallia above ground, and -the perfect plant generally has a creeping rhizome or underground stem. -Some, however, have strong, erect, woody stems, such as we see in the -tree ferns of tropical and sub-tropical countries. The horsetails and -the club-mosses are also produced from prothallia that are formed above -ground. The perfect plants of the former have branching underground -stems which give off numerous roots, and send up annually green, -jointed, aërial stems that bear whorls of fine leaves, each whorl -forming a toothed, ring-like sheath. The fertile shoots terminate in -cones, on the modified leaves of which the sporangia are produced. The -stems of the club-mosses are clothed with small overlapping leaves, in -the axes of which the sporangia are produced; and the spores, which are -formed in abundance, constitute the lycopodium powder with which -druggists often coat their pills. - -Water ferns either float on the surface of water or creep along the -bottom, and produce their fruit either at the bases of the leaves or -between the fibres of submerged leaves. The Selaginellas are -characterised by a procumbent stem that branches in one plane only, -producing small, sessile leaves, with a single central vein. A number of -roots grow downward from the under side of the stem, and the fruit is -developed in the axils of the leaves that form the terminal cones of the -fertile branches. - -The above are all the principal divisions of the flowerless plants, and -we have now to note the general characteristics of the _Phanerogams_. -The chief of these is, of course, the possession of flowers as -reproductive organs; and although it is not convenient to give a full -description of the flower at the present time, it will be necessary to -say a little concerning it in order that we may be able to grasp the -broad principles of classification. - -A flower, in its most complex form, consists of parts arranged in four -whorls arranged concentrically. The first and second whorls, commencing -from the outside, usually consist of leaf-like bodies, united or -distinct, and are called respectively the _calyx_ and the _corolla_. The -third whorl consists of _stamens_, which are the male reproductive -organs of the plant, and each stamen consists essentially of a case--the -_anther_--in which are formed a number of little _pollen cells_. When -the anther is ripe it opens, thus liberating the pollen, so that it may -be dispersed by insects, by the wind, or by other mechanical means. The -remaining whorl constitutes the _pistil_, which is generally made up of -parts (_carpels_) arranged round a common centre, and each surmounted by -a _stigma_ adapted for the reception of the pollen cells. This portion -of the flower contains the _ovules_, enclosed in a case called the -_ovary_, and is, therefore, the female organ of the plant. When the -ovules have been fertilised by the pollen, they develop into seeds, each -one of which contains an embryo plant; and the ovary itself, ripening at -the same time, develops into the _fruit_. - -Such is the general description of a flower in its most complex form, -but it must be remembered that one or more of the whorls named above may -often be absent. Thus, calyx or corolla, or both, may not exist; and the -male and female organs may be developed on separate flowers of the same -plant, or even, as is frequently the case, on different plants of the -same species. In the latter instance the flowers are spoken of as -unisexual, those bearing the stamens being the staminate or male -flowers, and those bearing the pistil the pistillate or female flowers. - -The _Phanerogams_ are divided into two main groups, the _Gymnosperms_ -and the _Angiosperms_. In the former the ovules are naked, no ovary or -seed-case being developed. The pollen, carried by the wind, falls -directly on the ovule, and then develops a tube which penetrates to the -nucleus of the ovule, thus fertilising it. In the Angiosperms the -ovules are always enclosed in an ovary, and the pollen grains, alighting -on the stigma, are held by a gummy secretion. The tubes they produce -then penetrate through the underlying tissues, and thus come into -contact with the ovules. - -The _Gymnosperms_ include a group of small palm-like trees and shrubs -(the _Cycadeæ_), of which the so-called Sago Palm is a representative; -and the _Coniferæ_ or cone-bearing shrubs and trees, which may be spoken -of collectively as the Pines. In the latter the leaves are either stiff, -linear, and needle-like, or short and scale-like, or are divided into -narrow lobes; and the plants are noted for their resinous secretions. -The flowers are always unisexual, and are generally arranged in -cylindrical or short catkins, where they are protected by closely packed -scales; but the female flowers may be solitary. There is no calyx or -corolla, but the naked ovules and seeds are sometimes more or less -enclosed in the scales (_bracts_) or in a fleshy disc. - -The _Angiosperms_ form the highest division of the flowering plants; and -are subdivided into two extensive groups--the _Monocotyledons_ and the -_Dicotyledons_. The chief distinguishing feature of these is that -implied in the above names, the embryo of the former containing but one -rudimentary leaf (_cotyledon_), while that of the latter contains two. -The Monocotyledons are also characterised by having the bundles of -vessels (_vascular bundles_) of the stems dispersed; the veins of the -leaves are also usually parallel, and the parts of the flower are -arranged in whorls of three or six. In the Dicotyledons the vascular -bundles of the stem are united into a ring which surrounds a central -pith; the veins of the leaves form a network, and the parts of the -flower are arranged in whorls of four or five. - -We are now enabled to understand the relative positions of the principal -groups of plants in the scale of vegetable life, and to locate -approximately the forms with which we have to deal; and to aid the -reader in this portion of his work we present a brief summary of the -classification of plants in the form of a table for reference:-- - - - THE CLASSIFICATION OF PLANTS - - I. =CRYPTOGAMIA=--Flowerless plants. - - (_a_) =THALLOPHYTES=--Leafless, cellular plants. - 1. =Protophyta=--Unicellular plants. - 2. =Algæ=--Sea weeds, &c. - 3. =Fungi=--Mushrooms, &c. - (_b_) =CHARALES.= - (_c_) =MUSCINEÆ.= - 1. =Hepaticæ=--Liverworts. - 2. =Musci=--Mosses. - (_d_) =VASCULAR CRYPTOGAMS.= - 1. =Filicales=--Ferns. - 2. =Equisetales=--Horsetails. - 3. =Lycopodiales=--Club-mosses. - 4. =Rhizocarpeæ=--Water ferns. - 5. =Selaginellales.= - - II. =PHANEROGAMIA.= - - (_a_) =GYMNOSPERMIA.= - 1. =Cycadeæ=--Cycads. - 2. =Coniferæ=--Cone-bearing trees. - (_b_) =ANGIOSPERMS.= - 1. =Monocotyledons.= - 2. =Dicotyledons.= - -We have now to deal more particularly with those marine _Algæ_ that are -commonly known as Sea Weeds, and which add so much to the beauty of our -rocky coasts. These exhibit such a variety of graceful forms, and such -charming colours, that they are admired and treasured by thousands of -sea-side ramblers, who are attracted by them merely on account of their -pleasing general appearance; but the naturalist has all this and a great -deal more to interest and instruct him, for the sea weeds possess quite -a number of peculiar and characteristic features that render them well -worthy of a detailed study, especially when they are compared and -contrasted with the better-known flowering plants of our fields, woods, -and hedgerows. - -It has already been observed that sea weeds differ from the majority of -flowering plants in that they have no true roots or leaves, though they -are often attached to rocks and other substances by a root-like disc, -and sometimes have leaf-like expansions that are supported by stem-like -rods. The root-like structures, however, serve simply for the attachment -of the plant, and are never concerned in the absorption of nourishment -like the true roots of higher plants; and the leaf-like expansions, -though they are sometimes symmetrical in form, never exhibit the spiral -arrangement that obtains in the leaves of higher plants, from which they -also differ in function. - -The plant-body of a sea weed is called a _thallus_, and differs -considerably in the various species. Sometimes it has no expanded -portion whatever, but is more or less cylindrical in all parts, and may -be either branched or simple; and in some species it forms a simple -crust or a soft jelly-like covering on a rock. - -All portions of a sea weed are made up of cells, and these are never -modified into vessels such as we see in the stems, leaves, and roots of -higher forms of vegetable life; and one who is commencing the study of -the algæ will find much interesting work in the examination of their -microscopic structure. Thin sections of various parts of the larger -weeds, cut with a sharp knife or a razor, and examined in a drop of -water under a cover-glass, will show the cellular structure perfectly; -while minute fragments of the small and slender species are sufficiently -thin and transparent to display the form and arrangement of their cells -without any previous preparation. - -One of the principal charms of the marine algæ lies in the great variety -of colour that they display. They all contain chlorophyll--that -remarkable green colouring matter which enables a plant, under the -influence of light, to feed on the carbonic acid gas existing in the -atmosphere, or held in solution in water; and with its aid the sea weeds -can utilise this product of decay and animal respiration that would -otherwise accumulate in the water of the sea. But, in addition to this -bright green chlorophyll, many of the sea weeds contain a second -colouring substance, and in these the great variety of tint is dependent -on the nature of the latter and on the proportion in which it is present -as compared with the chlorophyll itself. - -The different means by which the algæ reproduce their kind forms a most -engrossing subject, and to the botanist a most important one, for it has -much to do with the classification of the species. The affinities of -plants may be better determined by the nature of their reproductive -processes than by any other features, but unfortunately this is not so -well understood with regard to the algæ generally as compared with many -other divisions of the vegetable kingdom; and, as a consequence, there -is still a considerable difference of opinion, not only as to the extent -of the whole group, but also as to its divisions and subdivisions. The -reason for this is clear; for while it is quite an easy matter to trace -a flowering plant through its complete cycle from seed to seed, it -requires a much more careful examination, combined with much microscopic -work, to trace a lowly organised plant from spore to spore. - -Some of the algæ may be reproduced without the agency of any sexual -elements; that is, without the aid of parts that correspond with the -ovules and the fertilising pollen of a flowering plant. Some of these -are reproduced by a repeated subdivision, or by the separation of a -portion of the plant that is capable of independent growth; while others -produce spores that do not result from the fusion of two different -cells. In most, however, sexual differences are to be observed, some -cells being modified into female organs, containing one or two more -minute bodies that are capable of developing into new plants after they -have been fertilised, and other cells produce the male elements by means -of which the fertilisation is accomplished. The fertilised cells are -spores, but are named differently according to the nature of their -development. They all differ from true seeds in that they never contain -an embryo plant, but germinate by the elongation of some particular -part, which subsequently grows by a continuous process of cell-division; -or the cell-division may originate directly in the spore without any -previous elongation or expansion. - -The sea weeds are usually classified according to the colour of their -spores; but, since this colour generally corresponds with that of the -plant itself, we may almost say that they are grouped according to their -general tints. There are three main divisions:-- - - The _Chlorospermeæ_, or Green-spored; - The _Rhodospermeæ_, or Red-spored; and - The _Melanospermeæ_, or Brown-spored. - -The _Chlorospermeæ_ contain no colouring matter other than the -chlorophyll. They are mostly small weeds, of a delicate green colour; -and, although they are not particularly conspicuous on our shores, they -contribute very considerably to the beauty of the rock pools, where -their delicate green fronds contrast richly with the olive -_Melanosperms_ and the pink and white corallines. The thallus or -plant-body is very varied in form, sometimes consisting of a broad -membrane, but more commonly of tufts of slender green filaments or of -narrow, flattened fronds. - -These weeds are most beautiful objects for the microscope, and they are -generally so thin and transparent that no section-cutting is necessary, -nothing being required except to mount very small portions in a drop of -water. In this simple manner we may study the beautiful arrangement and -the various forms of the cells of which they are composed. The more -delicate species will be found to consist of a single layer of cells -only, while in the larger forms--the _Ulvaceæ_, for example--the thallus -may be formed of two or three distinct layers, and some of the cells may -be elongated into tubes. - -A remarkable feature of the green-spored weeds is the large size of the -chlorophyll granules as compared with those of the other groups, and -also the great variety of forms which these granules assume. They may be -easily seen under a low power, and the examination of the weeds will -show that the thalli are not uniformly green, but that the colour of the -plants is due entirely to the chlorophyll granules, the remainder of the -plant substance being quite colourless. - -If a green sea weed be placed in alcohol for a short time, it will be -found that the liquid assumes a green colour, while the plant itself -becomes colourless. The explanation is, of course, that chlorophyll is -soluble in alcohol. The presence of starch also in the weed may be -proved in a very simple manner, as follows:--Mount a small piece in -water, and then put a drop of iodine solution by the edge of the -cover-glass. The solution will gradually diffuse itself around the -object, turning the starch-grains to a deep blue colour, and so -rendering them very conspicuous under a moderately high power. - -The manner in which the green weeds are reproduced is very interesting -also. In some cases the fragments of a thallus that have been detached -by storms or other mechanical means possess the power of independent -growth, and develop into plants; and this mode of reproduction may often -be watched in the indoor aquarium. Another method is by the agency of -little spores (_zoospores_) that are produced at the edges or -extremities of the thallus. Certain of the cells become modified into -what are called _zoosporangia_, and the minute zoospores are formed -within them. The walls of the cells either gradually degenerate, or are -fractured, and the zoospores are thus set free. The latter are provided -with little vibratile cilia, by which they move about freely in the -water. Some eventually settle down and germinate without any further -aid, but others are unable to develop until they have been fertilised by -fusion with another cell. The former is therefore an _asexual_ -development, while the latter is _sexual_. - -Some of the delicate, filamentous green algæ are reproduced by another -process termed _conjugation_. In this case two adjacent threads that lie -close together become lightly united by a covering of gelatinous -substance, and a cell of each throws out a process. The processes are -directed towards each other, and unite to form a tube in which the -contents of the two cells become fused together, with the result that -zoospores are produced. - -Among the lowest of the green sea weeds are the plants known -collectively as the _Confervaceæ_, which consist of delicate green -filaments, usually attached to rocks in dense masses, but often found -floating freely in the rock pools. The filaments are composed of cells -joined together at their ends, and are always unbranched. - -Confervæ are found principally in the tide pools, especially near -high-water mark, and often abound in hollows in the rock even above -high-water mark, where the spray of the waves is mingled with rain-water -or the drainage from the land. They exist in both fresh and salt water, -and some species seem capable of thriving in brackish water of any -degree of salinity. - -Allied to the confervæ is a group of marine algæ called _Cladophora_, -very similar to the former in general appearance, and found in similar -situations, but readily distinguished by the branching of their jointed -filaments. The various species of this group are very beautiful weeds, -their delicate filaments looking very pretty as they float and sway in -the water of the pools. They are also exquisite objects for the -microscope; but, unfortunately, often lose their natural colour when -preserved dry. They vary in colour, some few being of a dull green tint, -while others are bright green, sometimes with a beautiful silky gloss. - -One species (_C. pellucida_) is more rigid than most of the others; its -fronds stand out erect and firm, and are repeatedly forked near the -tips. It is a moderately common weed, found in the lower rock pools, and -may be readily recognised by the long one-celled joints, from the tops -of which the branches proceed. Another species (_C. diffusa_) is also -very firm in structure, so much so that its bristly tufts retain their -form when removed from the water, instead of becoming matted together in -a shapeless mass. Its branches are rather long, and bear a few simple -branchlets towards their extremities. It is found in rock pools between -the tide-marks. _C. lanosa_ is a very pretty little weed, growing in -dense globular woolly tufts, an inch or more in diameter, on the olive -tangles between the tide-marks. It is of a pale yellowish-green colour, -which becomes much paler, or is even altogether lost, when the plant is -preserved in a dry state, and, at the same time its fine glossy -appearance is lost. Its fronds have straight branches, all making very -acute angles, and they have also small root-like filaments. It much -resembles another species (_C. arcta_), which grows in dense tufts on -rocks, but the latter is larger, not so slender, and more freely -branched. The cells, too, of _C. arcta_ are longer, being about ten -times the length of the diameter, and the fronds are silvery at the -tips. - -Nearly thirty species of _Cladophora_ have been described, but it is -impossible to give here a detailed description of all. We add, however, -a brief summary of the distinguishing features of a few other species -that are common on our coasts. - -_C. rupestris_ is common everywhere, and easily recognised by its rigid, -branching, tufted fronds, of a dark greyish-green colour; its branches, -which are opposite, bear awl-shaped branchlets. It is found in rock -pools from half-tide downwards, and in deep water beyond the tide-marks, -the plants growing in the latter situations being generally of a fine -dark-green colour. - -_C. lætevirens_ is also very common on rocks between the tide-marks. Its -fronds are tufted and freely branched, of a pale-green colour and soft -flexible texture, and about six inches long. The branchlets are usually -slightly curved. - -_C. gracilis_ is a beautiful plant that grows on large weeds, especially -the Sea Grass (_Zostera_) in deep water; and although not very common, -it is sometimes found on the beach after storms. It is characterised by -its slender silky fronds, from a few inches to a foot in length, of a -yellowish-green colour. It may always be known by the comb-like -branchlets growing only on one side of each branch. - -_C. refracta_ grows in dense tufts, two or three inches long, in rock -pools near low-water mark. Its fronds consist of rigid stems in -rope-like bundles that are very freely branched, the whole tuft being of -a yellow-green colour and silky texture. _C. albida_ closely resembles -it in structure and habit, but may be distinguished by its paler colour, -which disappears when the weed is dried, and by its longer and more -delicate branches. - -In another order of the green-spored algæ (the _Siphoneæ_ or -_Siphonaceæ_) the frond is formed of single branching cells, and many of -these are often interwoven into a spongy mass, and sometimes coated with -a deposit of calcareous matter. - -In the genus _Codium_ the fronds are of a sponge-like texture, composed -of interwoven branching fibres, and are of a globular, cylindrical, or -flattened form. The commonest species is _C. tomentosum_ (Plate VII.), -which consists of sponge-like, dark-green cylindrical fronds, which are -forked and covered with short hairs that give it a woolly appearance -when in the water. Each frond is composed of slender interwoven fibres -with club-shaped filaments passing vertically to the surface. It grows -on rocks in the pools between the tide-marks, and is abundant on nearly -all our coasts. - -The Purse Codium (_C. bursa_) has spongy hollow fronds of a globular -form, varying from a quarter of an inch to five or six inches in -diameter. It is a rare species, being found only at a few places on the -south coast. Another species (_C. adhærens_) adheres to rocks, over -which the fronds spread in irregular soft patches, the club-shaped -vertical filaments of its interwoven fibres giving it the appearance of -rich green velvet. - -An allied weed (_Bryopsis_), named from its moss-like appearance, grows -in erect tufts, each frond consisting of a branched one-celled filament. -There are two species of the genus, one (_B. plumosa_) characterised by -the light feathery nature of its fronds, the stems of which are branched -only near the top. It is found in rock pools on most of our coasts. The -other (_B. hypnoides_) is more freely branched, and the branches are -long, and issue from all sides of the stem. Like the last species, it -has branches on the outer part of the stem only, but it is of a softer -texture. - -The best known of the green-spored weeds are certainly those belonging -to the _Ulvaceæ_, characterised by their flat or tubular fronds, -sometimes of a purplish colour, the cells of which multiply both -horizontally and vertically as the plants grow. In the typical genus, -_Ulva_, the frond is sometimes in two distinct layers, and becomes more -or less inflated by the accumulation of either water or oxygen between -them. The commonest species are _U. lactuca_ and _U. latissima_, both of -which are eaten by the dwellers on some of our coasts. The former, -commonly known as the Lettuce Ulva, has a frond of a single layer of -cells, and grows on rocks and weeds between the tide-marks. It is common -on many oyster beds, and is employed by the fishermen to cover the -oysters when sent to market; they call it 'oyster green.' This species -is shown on Plate VIII. _U. latissima_ or the Broad Ulva sometimes -reaches a length of two feet, and a breadth of nearly a foot. The fronds -are composed of two layers of cells, are of an irregular shape, with a -very wavy, broken margin, and of a bluish-green colour, It is known -as the Green Laver, and is used as food in districts where the true -laver (_Porphyra_) is not to be obtained. A third species--the Narrow -Ulva (_U. Linza_)--has smaller and narrower fronds, of a more regular -shape and of a bright-green colour. The fronds are composed of two -layers of cells. - - [Illustration: Plate VII. - - SEA-WEEDS - - 1. Fucus nodosus - 2. Nitophyllum laceratum - 3. Codium tomentosum - 4. Padina pavonia - 5. Porphyra laciniata] - -The _Ulvæ_ retain their colour perfectly when dried, and, with the -exception of _U. latissima_, are of a mucilaginous nature, and adhere -well to paper, but, unfortunately, the graceful wavy outline of the -fronds is lost in pressed specimens. - -The 'true laver' mentioned above, which is also popularly known as -Sloke, is closely allied to _Ulva_, but may be distinguished from it by -the colour of its membranous fronds, which vary from a light rose to a -deep purple or violet, occasionally inclining to olive, but never green. -Its scientific name is _Porphyra laciniata_ (Plate VII.), and it differs -from the majority of the _chlorospermeæ_ in having dark-purple spores, -which are arranged in groups of four in all parts of the frond. The -fronds are very variable in form and size, being sometimes ribbon-like, -and sometimes spreading into an irregular sheet of deeply-divided -segments; and the remarkable variety of form and colour has led to a -division into several species. These, however, merge into one another so -gradually that the separation seems to be hardly necessary. - -The same remark concerning the multiplicity of species applies to -another allied genus called _Enteromorpha_, in which the fronds are -green and tubular, and often more or less branched. In these the colour -varies from a pale to a dark green, and the cells are arranged in such a -manner as to give a reticulated appearance. The commonest and -best-defined species are _E. intestinalis_, the tubular fronds of which -are constricted at intervals in such a manner as to resemble the -intestines of an animal, and _E. compressa_, with branched fronds of -variable form and size. The former is common on all our coasts, and may -even be found in rivers and ditches some distance from the sea. It -thrives equally well in fresh and salt water, and appears to grow most -luxuriantly in the brackish waters of tidal rivers. The latter species -also thrives best in similar situations. - -Coming now to the red-spored sea weeds (_Rhodospermeæ_), we have to deal -with some of the most charming of the marine algæ that invariably -attract the sea-side rambler, and provide many of the most delightful -objects in the album of the young collector. Their brilliant colours, -varying from a light red to dark purple and violet, are sufficient in -themselves to render them popular with the collector, but in addition to -this striking feature they are characterised by extreme elegance of form -and delicacy of texture. They are to be found in most rock pools, from -near high-water mark downwards, the smaller and more delicate forms -adding much to the beauty of these miniature seas; but the largest and -many of the prettiest species exist only at or beyond the lowest ebb of -the tide, and hence the algologist, in quest of these beautiful plants, -will find it necessary to work at the very lowest spring tides, with the -occasional aid of a small boat drifted into the narrow channels among -outlying rocks, and a long hook with which to haul up submerged -specimens; and it will also be advisable to search the line of débris at -high-water mark after stormy weather for rare weeds that may have been -detached and washed ashore by the angry waves. - -While engaged in the former of these employments--the searching of -outlying rocks with the boat--and also when examining the outer rock -pools which are disturbed by the waves that wash over their banks, the -simple instrument known as the water-telescope will prove invaluable. -Everyone must have noticed how difficult it is to observe objects in -water, the surface of which is disturbed by the wind or some other -cause; but the simple appliance named, consisting only of a long tube of -metal, a few inches in diameter, and painted a dead black inside, will -enable the observer to see all submerged objects with the greatest of -ease when the water is itself clear. The principle of the -water-telescope is as simple as its construction; for the tube, -protecting the surface of the water within it from the disturbances -outside, prevents the light from being refracted successively in -different directions, while the dead-black surface of the interior -prevents those internal reflections that would otherwise cause the -vision to be indistinct. - -A few hours spent with the rhodosperms at the sea-side will be -sufficient to show not only the great variety of their form and -colouring, but also that the same species may vary according to the -position in which it grows. Most of the smaller forms are delicate and -filamentous, but others have expanded fronds which are very leaf-like. -The brightest colours are usually to be found at or beyond low-water -mark, where the weeds are covered with a considerable height of water -for hours together, and also in shady situations at higher levels, while -some of the species that grow in the upper rock pools are often of such -a deep colour, with so much admixture of brown, that they may be easily -mistaken for the olive melanospores to be presently described. - -Most of the rhodosperms are attached directly to the rocks, and the -larger species have often a root-like disc by which they are very firmly -held; but some of the smaller species grow attached to larger weeds, -into the substance of which they frequently penetrate; and it is -possible that these derive some amount of nourishment from the sap of -their supporters. Some are of a recumbent nature, being attached to the -rock throughout their whole length, while others are so incrusted with -carbonate of lime which has been extracted from the water that they -resemble corals rather than forms of vegetable life. Nearly all of them -contain a bright-red colouring matter in addition to the chlorophyll by -which they are enabled to feed on carbonic acid gas. - -None of the rhodosperms are of really microscopic dimensions, and they -all grow by the repeated division of the cells of the apex, while the -branches are derived by the similar division of new cells at the sides. - -All plants are particularly interesting during the period of fruiting, -and this is remarkably the case with many of our red-spored sea weeds, -which are brighter and prettier while laden with their spore-producing -cells; and the collector of marine algæ should always endeavour to -obtain as many species as possible in fruit, not only on account of the -brighter appearance that may characterise them at this time, but mainly -because the opportunity of studying the mode of reproduction should not -be missed. - -In the rhodosperms the reproduction may be either asexual or sexual. In -the former case fertile spores are produced without the necessity for -any outside fertilising element, and four are usually produced in each -one of the sporangia, hence they are generally known as _tetraspores_. -Where the reproduction is of the sexual type, the male cells are -produced singly in the terminal cells of the fronds, and since they are -usually crowded together in considerable numbers, and contain none of -the red colouring matter that exists in the other parts of the plant, -their presence is easily observed. - -The female cells (_carpogonia_) are also produced on the tips of the -branches, and when the male elements escape from their cells, they are -conveyed passively by the movements of the water, for they have no -vibratile cilia by which they are propelled, and on coming into contact -with the female cell they adhere closely. An opening is then formed in -the latter, and the male element enters the carpogonium, which -germinates, deriving its nourishment from the parent plant, and the -spores are thus formed. Lastly, it is interesting to note that the -asexual spores, the male cells, and the female cells are generally -produced on different plants of the same species. - -We will now proceed to examine some of the best known and most -interesting of the rhodosperms, beginning with the order _Ceramiaceæ_, -which contains a number of red or reddish-brown weeds with jointed, -thread-like fronds that enclose a single tube, and which are generally -surrounded by a cuticle of polygonal cells. The spores are contained in -transparent berry-like sacs which are naked; and the four-parted spores -(_tetraspores_) are formed in the cells of the cuticle or at the tips of -the fronds. - -Over twenty British species belong to the genus _Callithamnion_, and -nearly all of them are pretty red or rose-coloured, feathery plants that -are conspicuous for their beauty. Nearly all are of small size, the -largest measuring only seven or eight inches, while some are so small -that they would scarcely be noticed except by those who search -diligently for them. The principal features of the genus are, in -addition to those mentioned above as common to the order, that the -spores are angular, and clustered within a transparent sac, and the -tetraspores are naked and distributed on the branches. - -In some species the fronds have no stem, and these are very small, -generally only about a quarter of an inch in height or less, and they -grow on rocks or weeds, sometimes clothing the surfaces with a -velvet-like covering. _C. floridulum_ forms a kind of reddish down on -the rocks, sometimes in little rounded patches, but sometimes completely -covering the surface. It occurs on several parts of the English coast, -but is so abundant on the west coast of Ireland that the beach is strewn -with it after stormy weather. Other allied species grow in minute tufts -on rocks, or are parasitic on other weeds, and are so inconspicuous that -they are but little known. - -Another section of the genus is characterised by pinnate fronds with -opposite segments, and the species are very pretty plants with fronds -generally a few inches in length. One of the commonest of these is the -Feathered Callithamnion (_C. plumula_), a great favourite with -collectors of sea weeds, and a most interesting object for the -microscope. Its soft and flexible fronds grow in tufts from two to five -inches long. The branches are regularly arranged, and the comb-like -branchlets bear the tetraspores on the tips of the plumules. This -beautiful weed grows near low-water mark, and in deep water, and is -often very abundant on the beach after storms. _C. Turneri_ is another -common species, easily known by its creeping fibres, attached by little -discs to some larger weed, and from which the tufts of branched fronds -stand out erect. On the west and south-west coasts of Britain we may -often meet with the allied Crossed Callithamnion (_C. cruciatum_), which -grows on rocks, close to low-water mark, that are covered with a muddy -deposit. It grows in tufts, somewhat resembling those of _C. plumula_, -but its plumules are arranged two, three, or four at a level, and are -very crowded at the tips of the branches. - - [Illustration: FIG. 245.--_Callithamnion roseum_] - - [Illustration: FIG. 246.--_Callithamnion tetricum_] - -Still another section of this large genus contains weeds of a more -shrubby growth, with veined stem and branches jointed obscurely. Of -these the Rosy Callithamnion (_C. roseum_) is not uncommonly found on -muddy shores, and especially in and near the estuaries of rivers. It -grows in dense dark-coloured tufts, two or three inches long, with -alternate branches much divided. The tetraspores occur singly, one at -the top of each of the lower joints of the pinnules of the plumes. _C. -byssoideum_ grows on larger weeds in the rock pools, and especially on -_Codium tomentosum_ (p. 353), in dense tufts of exceedingly fine -filaments, jointed, and branched irregularly. The upper branches are -plumed, and their tips bear very fine colourless filaments. The -spore-clusters are arranged in pairs, and the tetraspores are thinly -scattered on the pinnules of the plumes. This species is so very -delicate in structure that a lens is absolutely necessary to make out -its structure. It is, in fact, impossible to distinguish between the -various species of Callithamnion without such aid; and many of them, -particularly the species last described, require the low power of a -compound microscope. - -Among the other common species, belonging to the same section, we may -mention _C. corymbosum_, distinguished by its very slender, rosy, -jointed fronds, with the ultimate divisions of the branches disposed in -a level-topped (_corymbose_) manner, growing on rocks and weeds near -low-water mark; _C. polyspermum_, growing in globular tufts on _Fucus -serratus_ and _F. vesiculosus_, with short awl-shaped pinnules, and -closely-packed clusters of spores; _C. Hookeri_, with opaque stem and -branches, and spreading branchlets that are themselves branched, and -bear spreading plumules at their tips; and _C. arbuscula_, found on the -west coasts, with a stout stem, naked below, and having a very bushy -habit. - -It is often by no means an easy matter to distinguish between the -different species in such a large genus as _Callithamnion_, and we -strongly recommend the beginner to first study the characteristics on -which the classification of the _Algæ_ is based, and to arrange his -specimens according to the orders and genera to which they belong; and -then, after mastering the principles of classification, he should refer -to one of those larger works in which all known British species are -described, and make himself acquainted with the features of each -individual species in his collection. - -Before leaving the present genus we ought also to mention the fact that -many of the species lose their natural colour rapidly when placed in -fresh water; hence when they are being cleansed for mounting salt water -should be employed. Further, even after they have been satisfactorily -mounted, they are liable to be spoiled if left exposed to moist air. The -salt water used need not be the natural sea water; a solution of common -table salt, made up to approximately the same strength as sea water, -will answer the purpose just as well. - -The genus _Griffithsia_ includes some very beautiful weeds of delicate -threadlike structure and of a fine rose colour. The frond contains a -single tube, and is jointed and forked, the joints being usually -transparent. The spore clusters are enclosed in a gelatinous sac -surrounded by a whorl of little branchlets, the spores themselves being -minute and angular. The tetraspores are attached to the inner side of -whorled branchlets. - -The commonest species is _G. setacea_, which is of a bright-red colour -and slightly branched. It is also of a somewhat firm structure, but soon -loses both firmness and colour when removed from salt water; and, like -_Callithamnion_, rapidly fades if put into fresh water, which is -readily absorbed through its membranes, causing them to burst and -discharge their colouring matter. It receives its specific name from its -bristle-like forked fronds. _G. secundiflora_ is somewhat like -_Setacea_, but is larger, and the tips of its branches are obtuse. Its -fronds grow in fan-shaped tufts five or six inches long. It is not a -common weed, but may often be met with on the coast of Devon and -Cornwall. - - [Illustration: FIG. 247.--_Griffithsia corallina_] - -_G. barbata_, or the Bearded Griffithsia, receives its name from its -very delicate fibres, which bear spherical, pink tetraspores. It seems -to occur only on the south and south-west coasts, where it grows on -stones or attached to other weeds. Our last example of the genus is _G. -corallina_, which is of a deep-crimson colour, and is so jointed as to -have the appearance of a coralline. Its fronds are from three to eight -inches long, regularly forked, and of a gelatinous nature. The joints -are somewhat pear-shaped, and the spore clusters are attached to their -upper ends. It soon fades, and even if its colour is satisfactorily -preserved, the pressure of the drying press destroys the beautiful -rounded form of its bead-like joints. It forms a lovely permanent -specimen, however, when preserved in a bottle of salt water, with the -addition of a single grain of corrosive sublimate. - - [Illustration: FIG. 248.--_Halurus equisetifolius_] - - [Illustration: FIG. 249.--_Pilota plumosa_] - -Our next genus (_Halurus_) contains a common weed of the south coast -which was once included in _Griffithsia_. It is the Equisetum-leaved -Halurus (_H. equisetifolius_), so called because its branches are -regularly whorled round the nodes of the jointed branches, thus -resembling the semi-aquatic Mare's Tail. Its frond is tubular, and the -spore-clusters are situated on the tips of the branches, surrounded by a -whorl of small branchlets. - -The genus _Pilota_ has a slightly flattened cartilaginous frond, divided -pinnately, and the axis surrounded by a cuticle of two layers of cells. -The spore-clusters, at the tips of the branches, are surrounded by a -whorl of branchlets. It contains only two British species, one of which -(_P. plumosa_) is a very feathery species, with comb-like branchlets, -growing on the stems and fronds of other weeds found on our northern -shores. The other (_P. elegans_), with narrower fronds, in long flaccid -tufts, is found all round our coasts. - -Our last genus of the _Ceramiaceæ_ is the large and typical one -_Ceramium_, which contains about a dozen British species in which the -frond is threadlike, jointed, branched or forked repeatedly, with the -tips of the branchlets usually curled. The spore-clusters are enclosed -in transparent sessile sacs, surrounded by a whorl of very short -branchlets; and the tetraspores are embedded in the cortex, but -distinctly visible. As a rule the fronds are very symmetrical, and the -branches radiate in a regular fan-like manner. - -In one species of the genus the frond is completely covered with cortex -cells, and at each node of the frond there is a single spine which, -although so small as to be invisible without a lens, so effectually -locks the threads together that they form an entangled mass that is not -easily arranged to the satisfaction of the collector. The species -referred to is _C. flabelligerum_--the Fan-bearing Ceramium--and is very -rare except in the Channel Islands. - -Other species are armed with one or more spines at the nodes, but the -nodes only are covered with cortex cells, which render them opaque, -while the internodes or joints are transparent. In this group we have -_C. ciliatum_--the Hairy Ceramium, with reddish-purple segments, and a -regular whorl of hairs, directed upwards, round each node; each hair or -spine consists of three segments. This plant is common during the summer -and autumn, and may be found in the tide pools at all levels, either -attached to the rocks or parasitic on other weeds. The same section -contains _C. echinotum_, with rigid, forked fronds, and -irregularly-scattered one-jointed spines; it is common on the south -coast, where it may be found on the rocks and weeds of the upper tide -pools; and _C. acanthonotum_, also common in the rock pools, with a -single strong three-jointed spine on the outer side of each filament. -The last-named weed is found principally on the northern shores, -especially on rocks covered with the fry of the common mussel. - -Other species are characterised by transparent internodes as above -described, but have no spines at the joints, and may thus be easily -floated on to a sheet of paper without the troublesome matting of their -fronds. These include the Straight Ceramium (_C. strictum_), with erect -and straight branches growing in dense tufts, and conspicuous -tetraspores arranged round the nodes of the upper branchlets, _C. -gracillimum_, of the lower rock pools, with very slender gelatinous -fronds, swollen nodes and small fan-shaped branchlets; _C. tenuissimum_, -closely resembling _C. strictum_ in general appearance, but -distinguished by having its tetraspores only on the outer side of the -nodes; and the Transparent Ceramium (_C. diaphanum_), which may be found -throughout the year on rocks and weeds in the rock pools. The last -species is the largest and most beautiful of the genus, and may be -readily recognised by its light-coloured, transparent stem with swollen -purple nodes, and its conspicuous spore-clusters near the tips of the -filaments. - - [Illustration: FIG. 250.--_Ceramium diaphanum_] - -Our last example of the genus is the Common Red Ceramium (_C. rubrum_), -which may be found in the rock pools at all levels. It is very variable -in form, but may be known by its contracted nodes, in which the red -tetraspores are lodged, and its spore-clusters surrounded by three or -four short branchlets. It differs from most of the other species in -having both nodes and internodes covered with cortex-cells, and hence -the latter are not transparent. - -The order _Spyridiaceæ_ has a single British representative which may be -found in various localities on the south coast. It is _Spyridia -filamentosa_, a dull-red weed with thread-like, tubular, jointed fronds, -from four inches to a foot in length. The main stem is forked, and -densely clothed with short and slender branchlets. The frond is covered -with a cortex of small cells. The spore-clusters are grouped together, -several being enclosed in a membranous cell in conceptacles, or external -sacs, at the ends of the branchlets; and the tetraspores are arranged -singly along the jointed branchlets. - -The next family (_Cryptonemiaceæ_) is an extensive one, containing -nearly twenty British genera of red or purple weeds, with unjointed, -cartilaginous, gelatinous, and sometimes membranous fronds. The spores -are irregularly distributed, and are contained either in sunken cells or -in conceptacles. The tetraspores are either in cells at the edges of the -frond or collected together in compact groups. - -Of the genus _Dumontia_ we have only one species (_D. filiformis_), the -frond of which is a simple or branched tube, from an inch to more than a -foot in length, containing a loose network of filaments when young, and -only a gelatinous fluid when the plant is mature. The spores exist in -rounded clusters among the cells of the tube, and the tetraspores are -similarly situated. A variety with wide wavy fronds is sometimes found -in the brackish water near the mouths of rivers. - -_Gloiosiphonia capillaris_ is a very delicate and beautiful weed found -in the lowest tide pools of the south coast. Its frond is a very slender -branched tube, filled with a gelatinous fluid, and composed of delicate -filaments embedded in transparent gelatine. It is a beautiful object for -the microscope. - -_Schizymenia_ (_Iridæa_) _edulis_ has flat, oval, dark-red fronds that -grow in clusters; and, being eaten by various marine animals, is often -found imperfect and full of holes. The fronds are sometimes a foot or -more in length, and five or six inches wide. They are thick and -leathery, and each is supported on a short, cylindrical stem. - -In the lower tide pools we commonly meet with _Furcellaria fastigiata_, -with brownish-red, cylindrical fronds, solid, forked, and densely -tufted. The branches are all of the same height, with sharp tips; and -the spore-clusters are contained in terminal lanceolate pods. This weed -is very much like _Polyides_, of another order, but may be distinguished -by its fibrous, creeping root, while that of _Polyides_ is a disc. - -The genus _Chylocladia_ is characterised by a tubular rounded frond -composed of two layers, the inner consisting of branching filaments, and -the outer cellular. The spores are contained in external cones with a -pore at the apex, and the tetraspores are among the superficial cells of -the branches. There are two common British species of the genus, one of -them--_C. articulata_--with long, tubular fronds, constricted at -intervals, the lower branches forked and the upper whorled and tufted; -and _C. clavellosa_, with freely branched fronds bearing short -spindle-shaped branchlets. - -One of the best-known algæ of the present family is the Irish Moss or -Carrageen (_Chondrus crispus_), which will be at once recognised by its -representation on Plate VIII. Its fronds are cartilaginous, forked and -fan-shaped; and, when growing in deep, sheltered pools, its branches are -often broad and much curled. This weed is an important article of -commerce, being still used as a food for invalids. When boiled it -yields a colourless gelatine. - -In the genus _Gigartina_ the frond is cartilaginous, flat, or -threadlike, irregularly branched, and of a purplish-red colour. The -spores are contained in external tubercles, and the tetraspores are -arranged in masses beneath the surface. The only common species is _G. -mamillosa_, which has a linear, furrowed stem, with fan-shaped, -deeply-cleft fronds. The spores are contained in mamilliform tubercles -scattered over the surface of the frond. - -_Callophyllis_ (_Rhodymenia_) _laciniata_ is found on most rocky coasts. -It has bright-red, fleshy fronds that are deeply cleft into wedge-shaped -segments, the fertile specimens with waved edges and small marginal -leaflets. It is found on rocks and Laminaria stems beyond the -tide-marks, but is commonly washed up on the beach during storms. It is -a beautiful weed, and retains its colour well when dried. - -_Cystoclonium_ (_Hypnæa_) _purpurascens_ is a very common weed, growing -on other algæ between the tide-marks, and sometimes reaching a length of -two feet. Its cartilaginous, purple fronds are much branched, and become -almost black when dried. The spores are embedded in the smallest -branches, and the tetraspores are arranged among the superficial cells. - -The genus _Phyllophora_ contains a few British weeds with a stiff, -membranous frond, bearing leaf-like appendages, and supported on a -stalk. The tetraspores are contained in external wart-like swellings. -The commonest species is _P. membranifolia_, the fronds of which are -divided into wedge-shaped segments, and grow in tufts from an expanding -root. The spores are contained in stalked sporangia, and the tetraspores -are near the centres of the segments. Another species--_P. rubens_--has -a shorter stem, and grows in deep and shady rock pools. Its fronds are -densely tufted; and, as the plant grows, new series of segments are -formed at the tips of the older ones. A third species (_P. -palmettoides_) has a very bright-red frond and an expanded root. - -The order _Rhodymeniaceæ_ includes a number of red or purple sea weeds -with flat or thread-like unjointed, cellular fronds, the surface cells -forming a continuous coating. The spores are lodged in external -conceptacles, and are at first arranged in beaded threads. The -tetraspores are either distributed among the surface cells, collected in -clusters, or situated in special leaflets. - -The typical genus (_Rhodymenia_) contains two red, membranous weeds, -the commoner of which is _R. palmata_ (Plate VIII.), so common on the -Scottish and Irish coasts, where it forms an important article of diet, -and is known as the Dulse or Dillisk. It is also widely distributed over -the English coasts. Its broad, fleshy fronds are divided into -finger-like lobes, and are either sessile or supported on a stalk that -proceeds from a small discoid root. The frond is very variable in form, -being sometimes divided into very narrow segments, and sometimes quite -undivided. One variety has a number of small stalked leaflets on its -margin (see Plate VIII.); and another is very narrow, with wedge-shaped -irregular lobes. _R. palmetta_ is a smaller and less common species that -grows on rocks and large weeds in deep water. The tetraspores form -crimson patches on the tips of the lobes. - -_Maugeria_ (_Delesseria_) _sanguinea_ (Plate VIII.) is a large and -beautiful weed, of a blood-red colour, that grows in the lower rock -pools or beyond low-water mark, under the shade of high rocks or hidden -by the olive tangles. Its frond is thin and membranous, with a -well-defined midrib. The spores are contained in globular stalked -conceptacles, usually on one side of the midrib; and the tetraspores may -be seen in pod-like leaflets attached to the bare midrib during the -winter. - -Passing over some of the rarer membranaceous _Rhodymeniaceæ_, we come to -the beautiful _Plocamium_, distinguished by its linear compressed -crimson fronds, which are pinnate, with comb-like teeth, the branchlets -being alternately arranged on either side in threes and fours. The -spores are on radiating threads, in globular conceptacles; and the -tetraspores are in the outer divisions of the frond. We have only one -species of this beautiful genus, and that is _P. coccineum_, which is of -such a brilliant colour that it is always a favourite with collectors. - - [Illustration: FIG 251..--_Plocamium_] - -Our last example of the order is _Cordylecladia_ (_Gracilaria_) -_erecta_, with threadlike, cartilaginous frond, irregularly branched and -cellular in structure. The fronds arise from a disc-like root; and bear -spores in thickly-clustered spherical conceptacles, and tetraspores in -lanceolate pods at the tips of the branches, both in the winter. It is a -small weed, and grows principally on sand-covered rocks near low-water -mark. - -The order _Sphærococcoideæ_ contains red or purple sea weeds with -unjointed cartilaginous or membranaceous fronds, composed of many-sided, -elongated cells, with spores in necklace-like strings, lodged in -external conceptacles. The typical genus (_Sphærococcus_) contains the -Buck's-horn sea weed which grows at and beyond low-water mark on the -south and west coasts, where it is sometimes washed up on the beach -during storms. Its fronds are flattened and two-edged, freely branched, -and the upper branches are repeatedly forked, and terminate in -fan-shaped, cleft branchlets. Both branches and branchlets are fringed -with slender cilia, in which the spores are embedded. It is a handsome -weed, of a bright-red colour and a somewhat coral-like form. - -Allied to this is _Gelidium corneum_, with flattened, horny fronds, -repeatedly pinnate, with the smallest branchlets obtuse and narrower at -the base. The spores are contained in conceptacles near the extremities -of the branchlets, and the tetraspores are imbedded in club-shaped -branchlets. There are a large number of varieties of this species, -differing in form, size, and the mode of branching of the fronds. The -size varies from one to five or six inches, and the colour is red or -reddish green. - -In the genus _Gracilaria_ the frond is thick and horny, and the surface -cells are very small, while the central ones are large. The spores, -formed on necklace-like threads, are enclosed in sessile conceptacles -along the branches, and the tetraspores are imbedded among the surface -cells of the fronds. The only common species is _G. confervoides_, with -cylindrical cartilaginous fronds bearing long thread-like branches, -sometimes reaching a length of two feet. The spore conceptacles are -situated on the slender branches, giving them a knotted or beaded -appearance. The colour is a dark purple, which rapidly fades when the -weed is placed in fresh water or left exposed to the air. Two other -species--_G. multipartita_ and _G. compressa_--are rare. - -_Calliblepharis ciliata_, perhaps more commonly known as _Rhodymenia -ciliata_, has a branching root, short round stem, and a broad, crisp -frond that is generally ciliated. Sometimes the frond is simple and -lanceolate, with small leaf-like appendages on its edge; and sometimes -it is deeply cleft. The spores are arranged in beaded threads in sessile -conceptacles on the marginal leaflets. Another species of the same genus -(_C. jubata_) is very similar in structure, but is of a duller-red -colour, gradually changing to olive green at the tips; and it has its -tetraspores in the cilia only, while in _C. ciliata_ they are collected -in patches in all parts of the frond. Both species grow in deep water, -and are frequently washed up during storms. - -The large genus _Nitophyllum_ contains some beautiful rose-red sea -weeds, with irregularly cleft membranaceous fronds, either veinless, or -with a few indistinctly visible veins only at the base. The spores are -in rounded sessile conceptacles scattered on the surface of the frond; -and the tetraspores occur in clusters similarly scattered. - -One of the species--_N. laceratum_--so called from the torn and jagged -appearance of the frond, is represented on Plate VII. The fronds are -attached to a disc-like root, and are very variable in form, being -sometimes so narrow as to appear almost threadlike. The plant grows on -rocks and large weeds in the lower rock pools and in deep water. In the -same genus we have _N. punctatum_, with broad pink fronds, dotted all -over with spore-conceptacles and dark-red clusters of tetraspores; also -a few other less common species that are seldom seen except after -storms, as they grow almost exclusively in deep water. - -The genus _Delesseria_ contains some beautiful rose-coloured and -reddish-brown weeds with delicate, leaf-like, symmetrical fronds, each -of which has a darker midrib from which issue transverse veins. The -spores are arranged like minute necklaces, and are contained in sessile -conceptacles either on the midrib of the frond or on leaflets that grow -from the midrib. The tetraspores are in clusters which are scattered -over the frond or on its leaflets. The algæ of this genus are seldom -found growing between the tide-marks, as they generally thrive in deep -water, but splendid specimens are often washed up on the beach during -storms, especially on the south and south-west coasts. - - [Illustration: FIG. 252.--_Delesseria alata_] - - [Illustration: FIG. 253.--_Delesseria hypoglossum_] - -Among these we may specially mention _D. alata_, known popularly as the -Winged Delesseria, with a dark-red, forked frond, consisting of a -strong midrib, bordered by a wing-like lamina of very variable width, -supported by opposite veins. In this species the clusters of tetraspores -are arranged on each side of the midrib or special leaflets near the -tips of the frond. _D. sinuosa_ is a less common weed, with a disc-like -root and an oblong, cleft and toothed frond, and tetraspores in leaflets -growing from its margin. Another species--_D. hypoglossum_--is -characterised by the leaflets of the midrib bearing still smaller -leaflets in the same manner. - -We have already referred (p. 366) to a sea weed commonly known as the -Dock-leaved Delesseria, the scientific name of which is _Maugeria_ -(_Delesseria_) _sanguinea_. This plant was once included in the present -order, but has been removed on account of the different structure of its -fruit. - -Our next order is the interesting one containing the coral-like weeds, -some of which are so common and so conspicuous in the rock pools. The -order is known as the _Corallinaceæ_, and all its species secrete -carbonate of lime, which hides their vegetable structure and gives them -more the appearance of stony corals. - -The typical genus (_Corallina_) includes two weeds with jointed pinnate -fronds, and spore-conceptacles at the tips of the branches with a -terminal pore. - -These and the allied sea weeds are very unlike plants in their general -nature, their stony covering of carbonate of lime hiding all traces of -the delicate cellular structure so characteristic of the various forms -of vegetable life, and especially those of aquatic or marine habit. If, -however, the weed is put into dilute hydrochloric (muriatic) acid the -calcareous matter will be completely dissolved in a minute or two, with -evolution of bubbles of carbonic acid gas; and if a portion of the frond -be then examined in a drop of water under the microscope, the cellular -structure referred to will be seen as well as in any other weed. Another -characteristic of the plant, or rather of the carbonate of lime which it -secretes, is its property of becoming intensely luminous when held in a -very hot flame. Thus if a tuft of coralline be held in the flame of a -Bunsen burner, it will glow so brilliantly as to remind us of the lime -light. Further, if we examine the plant in its natural state, we find -that the carbonate of lime is not secreted uniformly in all parts, but -that the nodes of the jointed frond are free from the stony deposit, and -are therefore flexible. - -Our commonest species--_C. officinalis_--may be found in almost every -rock pool between the tide-marks, growing on rocks, shells, and other -weeds. The joints of the stem and branches are cylindrical or somewhat -wedge-shaped, while those of the branchlets are linear; and the colour -varies from a dark purple to white, the former prevailing in the deep -and shady pools and the depth of tint decreasing according to the amount -of exposure to the bleaching action of the sun. - -A second species (_C. squamata_) is very similar in growth and habit, -but is much less common, and is confined to the neighbourhood of -low-water mark. It may be distinguished from the last by the form of the -segments, which are short and globose in the lower portions of the stem, -and become broader and more flattened towards the tips of the branches. - -Another genus--_Jania_--contains a few coralline weeds that are somewhat -like _Corallina_, but are of a more slender habit and smaller, and have -a moss-like appearance. They may be distinguished by the _forked_ -branching of the slender frond, and by the position of the conceptacles -in the axils of the branches, and not at the tips. _J. rubens_ is a very -common red species that grows in tufts on other weeds. It has -cylindrical segments, longer towards the tips of the branches; while -another and less common one (_J. corniculata_), found principally on the -south coasts, has flattened segments except in the branchlets. - -A third genus of the order--_Melobesia_--contains a very peculiar group -of algæ that would certainly never be regarded as plants by those who -did not know them. They are apparently mere solid incrustations of -calcareous matter, without any jointed structure, and often of very -irregular form, covering the surfaces of rocks, shells, or weeds. They -are of varying colours, some prevailing tints being dark purple, lilac, -rose, and yellow; and they are equally variable in form, some being -decidedly lichen-like, some resembling fungoid masses, and others -consisting of superimposed leaf-like layers. They are not weeds to be -pressed for the collector's album, but require storing in boxes or trays -like sea shells. As in the case of the branched corallines, the hidden -vegetable structure may be revealed by dissolving away the carbonate of -lime; and the spore-conceptacles, with terminal pores, may be seen -scattered irregularly over the surface. - -The order _Laurenciaceæ_ contains some beautiful pink, red, and purple -weeds with round or flattened branching fronds. They may be known by the -disposition of the tetraspores, which are irregularly scattered over the -branches; and by the pear-shaped spores in rounded capsules. The -typical genus (_Laurencia_) includes an abundant weed (_L. pinnatifida_) -which was formerly eaten in parts of Scotland, where it is known as the -Pepper Dulse on account of its peppery taste. It is found in the tide -pools on many parts of the coast, and varies much in size, form, and -colour according to the situation in which it grows. The plants which -are exposed to the air at low tide are usually small, and of a pale -brown colour, while those found in the permanent rock pools at or near -low-water mark are larger and dark brown or purple. The fronds are flat -and cartilaginous, with stout branches bearing alternate divided -branchlets, which are blunt at the tips. The stem itself is unbranched. -The spores are pear-shaped, in oval cells; and the tetraspores are -irregularly distributed near the tips of the branches. - -Another common species, known as the Tufted Laurencia (_L. cæspitosa_), -is very similar to the last mentioned, and is not easily distinguished -from it. It is, however, of a bushy habit, while _L. pinnatifida_ is -flat, and its fronds are less firm. This species grows on rocks and -stones between the tide-marks, and is variegated in colour from a pale -green to a purple. - - [Illustration: FIG. 254.--_Laurencia pinnatifida_] - - [Illustration: FIG. 255.--_Laurencia obtusa_] - -A third species--the Obtuse Laurencia (_L. obtusa_)--is widely -distributed on our coasts, and may be known by its thread-like bipinnate -fronds with short blunt branchlets, cup-shaped at the tips. It is -parasitic on various other weeds. - -The genus _Lomentaria_ includes a few weeds with tubular fronds that are -constricted at intervals, and divided internally by transverse -membranous septa. The spores are pear-shaped and lodged in spherical -cells; and the tetraspores are scattered on the surface of the branches. -One species called the salt-wort (_L. kaliformis_) is widely -distributed. Its colour is pink, sometimes yellowish, and it grows on -rocks or stones, and sometimes on other weeds. It may always be known by -its spherical fruit, without any visible opening, containing crimson -pear-shaped spores. Another species (_L. ovalis_), found on the coasts -of Devon and Cornwall, may be recognised by its _solid_ branched frond -and little oval leaf-like branchlets, which are hollow, jointed, and -divided by partitions internally. - -The one remaining order of the red-spored sea weeds is the -_Rhodomelaceæ_, which has either a jointed or a many-tubed axis, and the -surface divided up into little definite areas. The fronds are either -leafy or thread-like, and the prevailing colours are red, reddish brown, -and purple. The spores are pear-shaped, and occupy the terminal cells of -tufted threads in external, globular, or rounded conceptacles; and the -tetraspores are lodged in special receptacles, or in special modified -branchlets. The order contains some of our most beautiful weeds, while -some of its members are of a very dark colour and unattractive form. - -The typical genus--_Rhodomela_--contains two British species with -dark-red, cartilaginous fronds, cylindrical, unjointed, and irregularly -branched; and the tetraspores imbedded in the tips of the slender -branchlets. The name of the genus signifies 'red-black,' and is applied -on account of the tendency of the dark-red fronds to turn black when -dried. - -_R. subfusca_ is very common on all our coasts. It has rigid fronds, -irregularly branched; and is in its best condition during the summer. -The other species--_R. lycopodioides_--has long undivided branches with -thickly-set and freely-divided branchlets. - -When turning over the fronds of different species of the larger olive -weeds we commonly find them more or less clothed with tufts of -filamentous plants, sometimes small and delicate, and sometimes larger -and of more robust growth, varying in colour from a purplish brown to a -dark violet, and the articulated filaments more or less distinctly -striated with parallel lines. These weeds belong to the genus -_Polysiphonia_, and derive their generic name from the fact that the -threadlike fronds are composed of several parallel tubes. The surface -cells are also arranged in regular _transverse_ rows, and it is this -which gives rise to the striated appearance above referred to. - -Over twenty species of _Polysiphonia_ are to be found on our shores, -where they exist at all levels between the tide-marks. They are -distinguished from one another partly by their general form and mode of -growth, and also by the number of tubes in their threadlike fronds. - -Although they would not always be considered as lovely weeds and are -often anything but beautiful when dried and mounted, yet in their fresh -condition they are generally pretty objects, and their microscopic -structure is particularly interesting on account of the beautiful and -symmetrical arrangement of their siphons and tubes. - -If the reader is the fortunate possessor of a compound microscope, it -will amply repay him to make transverse sections of the fronds for -examination. A short length of the frond should be inserted into a slit -cut in a piece of carrot or elder pith; and, while thus supported, very -thin transverse sections may be easily cut with a sharp razor, care -being taken to keep both razor and object very wet during the process. -Allow the sections to fall into a vessel of water as they are cut, and -then select the thinnest for examination, mounting them in a drop of -water in the usual way. - -Specimens in fruit should always be obtained when possible, so that the -nature of the fructification may be observed. Two kinds of spores may be -seen in each species, but, as is usually the case with the red sea -weeds, on different plants. Some are small pear-shaped bodies, enclosed -in oval cells at the tips of the fronds; and the others are arranged in -clusters of four in swollen parts of the threads. - -The commonest species is _P. fastigiata_, which may be found in -abundance as bushy brownish tufts on the fronds of _Fucus nodosus_ (p. -386). A transverse section of this weed is a very beautiful microscopic -object. It resembles a wheel, with a dark centre to the nave, and -several spokes enclosing about sixteen regularly arranged tubes. The -swollen tips of fronds should also be examined for the urn-shaped cells -containing the spores; and if a gentle pressure be applied to the -cover-glass with a needle, the little pear-shaped spores may be -expelled. The other kind of spores may be found near the bases of the -branches on different plants. - - [Illustration: FIG. 256.--_Polysiphonia fastigiata_] - -Among other species we may briefly mention--_P. parasitica_, sometimes -found near low-water mark, growing in little feathery tufts of a -bright-red colour, on the lichen-like _Melobesia_ or on corallines. It -has seven or eight parallel siphons in its fronds, all regularly -arranged round a small central space. - -_P. Brodiæi_ is moderately common on our coasts. This is a large brown -species, with seven siphons surrounded by a thick cellular layer which -conceals the articulations and is too opaque to allow the siphons to be -seen without dissection. Its branches, which are alternate, bear short -tufts of delicate branchlets. - - [Illustration: FIG. 257.--_Polysiphonia parasitica_] - - [Illustration: FIG. 258.--_Polysiphonia Brodiæi_] - -_P. byssoides_, so called on account of the pink filaments that fringe -the fronds, has also seven siphons. It is a large and beautiful weed, -moderately common on our coasts, of a bright-red colour, with -conspicuous fructification. The branches are alternate, and the -branchlets are clothed with the byssoid filaments above referred to. - -_P. violacea_ is of a reddish-brown colour, with long silky alternate -branches, and four siphons. It receives its specific name from the fact -that it turns to a violet colour when dried. - -_P. nigrescens_ has, as the specific name implies, blackish fronds, and -these are freely branched. The tubes, about twenty in number, are flat, -and are arranged round a large central space. - - [Illustration: FIG. 259.--_Polysiphonia nigrescens_] - -Our last example--_P. atro-rubescens_--is of a dark reddish-brown -colour, with rigid and densely-tufted fronds. It has twelve tubes, -arranged _spirally_ round a central cavity. It is common in the lower -rock pools of some coasts. - -In the same order we have the genus _Chondria_, so called on account of -the cartilaginous nature of its thread-like fronds. These are pinnately -branched, and the club-shaped branchlets taper below. The main stem is -jointed and contains many siphons. The genus includes a common species -(_C. dasyphylla_), with thick fronds, that is found in shallow sandy -pools, where it grows on pebbles, shells, or on other weeds, the colour -varying from pink to a dark purple. _C. tenuissima_ is a very similar -weed, but may be distinguished by its more slender growth, and by its -long, rod-like simple branches, clothed with slender, bristle-like -branchlets that taper from the middle towards both ends. - -On the northern coasts of Britain we may meet with _Odonthalia dentata_, -the blood-red fronds of which are tufted, and arise from a hard, -disc-like root. Each frond projects from the axil of a tooth-like -projection of the main stem, and is deeply pinnatifid, with a distinct -midrib in the lower part, and thin and membranaceous towards the tip. -The pinna are dentate, and the spores are in stalked, oval conceptacles -in the axils of the pinnæ. The tetraspores are similarly situated in -stalked, lanceolate leaflets. - -The weeds of the genus _Rytiphlæa_ are very similar to some of the -_Polysiphonia_, the axis of the frond being jointed and transversely -striped, but the nodes are less distinct and are not constricted. They -are shrub-like weeds, with tufted spores in oval, sessile conceptacles; -and tetraspores in spindle-shaped branchlets or in little pod-like -leaflets. The principal British species are:-- - -_R. pinastroides_, a much-branched and shrub-like weed, of a dull-red -colour, which turns black when the plant is dried. The branches have -rigid, hooked branchlets arranged in such a manner as to give a combed -appearance. This species occurs on the south coast, and is in its prime -in very early spring. It is often rendered peculiarly interesting by the -colonies of zoophytes and the patches of _Melobesia_ with which it is -more or less covered. - -_R. fruticulosa_ is another shrubby species, with irregularly branched, -interlacing stems. It is to be found in the rock pools of the south and -west coasts, and is of a deep-purple colour in the deeper shady pools, -but varying to a yellowish tint where exposed to the full light of the -sun. The whole of the frond is covered with hooked branchlets, and the -weed is peculiar for the fact that, when removed from the rock pool, -little glistening beads of water remain attached to the tips of the -terminal branches. The tetraspores are situated in distorted branchlets. - -_R. thuyoides_ has creeping, fibrous roots, from which arise the erect -stems of purple-brown, branched fronds with short spine-like branchlets. -It occurs in the shallower rock pools, where it grows attached to rocks -or to other weeds. It is in its best condition during the summer, when -we may see its oval spore-conceptacles and the tetraspores in distorted -branchlets. - -The last genus of the _Rhodomelaceæ_ is _Dasya_, which contains some -very graceful and brightly-coloured weeds that are found principally on -our south and west coasts. In these the fronds are thread-like or -flattened, branched, and without visible joints. The main stem contains -many tubes, but the tubular structure is hidden by the outer layer of -cells; and the branchlets, which are slender, one-tubed, and jointed, -bear little lanceolate pods that contain the tetraspores. - -_D. ocellata_ has small tufted fronds, about two or three inches long, -attached to a small discoid root. The main stems are densely covered -with slender, forked branchlets, those at the tips being clustered in -such a manner as to recall the eye-like marks of the peacock's tail. It -grows principally on the mud-covered rocks beyond low-water mark, and is -not by any means a common weed. Another species--_D. arbuscula_--is -somewhat plentiful on parts of the Scottish and Irish coasts, but -comparatively rare in South Britain. It has a small disc-like root, and -stems thickly clothed with short branchlets. The spore-conceptacles are -tapering, on short stalks, and the tetraspores are contained in pointed -pods on the branchlets. The scarlet Dasya (_D. coccinea_) may be -commonly seen at and beyond low-water mark during late summer, at which -time splendid specimens may also be found on the beach after storms. Its -stem is thick, proceeding from a discoid root, and is clothed with -hair-like filaments; and the branches bear short, slender branchlets -that give them a feathery appearance. The tetraspores are contained in -elongated, pointed, and stalked pods. There are three other species on -the British list, but they are not common weeds. - -The last of the three great groups into which the sea weeds are divided -is the _Melanospermeæ_, or olive-spored algæ, the different species of -which are generally very readily distinguished by their olive-green or -olive-brown colour, for the whole plant, as well as the spores, contains -a dark olive colouring matter, in addition to the chlorophyll which is -always present. - -These weeds are often very large, frequently attaining a length of -twenty feet or more in our seas, and from eighty to a hundred feet in -warmer parts; and, being also extremely abundant almost everywhere, they -form a most conspicuous feature of the shore. They usually grow on rocks -and stones, from high-water mark to moderately deep water, but some of -the smaller species are pseudo-parasitic on other algæ. - -Their form is most varied. Some are minute filamentous plants, -consisting only of slender jointed threads, and others are mere -shapeless masses; but many of the larger species exhibit a great -differentiation of form, having root-like and stem-like structures, and -expansions that resemble leaves. The latter, too, often have large -vesicles that contain air, sometimes arranged singly along the median -line of the frond, or in lateral pairs, or a single vesicle at the base -of each segment of the thallus. - -The air vesicles, of course, serve to buoy up the plant when it is -submerged, thus enabling the light to penetrate between its fronds to -lower portions; and when the plants have been wrenched from their -moorings by the force of the waves, they immediately rise to the surface -and are drifted on to the shore or accumulate in the eddies of the -surface currents. In this way immense masses of floating weeds are -formed, the most remarkable being that of the Sargasso Sea in the North -Atlantic. - -Like other algæ, the melanospores grow by a continued process of -cell-division, and when portions of the thallus are worn away during -stormy weather, they are renewed by the same process. - -The cell-walls of many species are very mucilaginous, the gelatinous -covering being either the result of the degeneration of the cell-walls -themselves, or the secretion of special glands. - -As with the last division, the reproduction of the melanospores may be -asexual or sexual. The asexual spores, which are not motile, are formed -in some of the surface cells of the thallus. The male and female sexual -organs, called respectively the _antheridia_ and the _oogonia_, are -produced in cavities on special portions of the thallus, both kinds -being often formed in the same cavity or depression. The latter contains -from one to eight little bodies called _oospheres_. These escape and -float passively away when the wall of the oogonia ruptures. The -antheridia are also discharged whole, but the minute fertilising -elements (_antherozoids_), which are eventually set free from them, -swarm round the oospheres, being attracted by the latter. Soon one of -the antherozoids enters the oosphere, and from that moment all -attraction ceases, the remainder of the antherozoids floating passively -away; and the oosphere, previously naked and barren, now develops a -cell-wall, and becomes the fertile progenitor of a new plant. - -Starting with the lowest of the melanospores, we first deal with the -order _Ectocarpaceæ_, which is characterised by olive, thread-like, -jointed fronds, with spores on the branchlets or embedded in their -substance; two kinds of spores often existing in the same plant. - -The typical genus (_Ectocarpus_) contains many British species, though -several of them are rare. They are soft and flexible weeds, generally of -a dull olive colour, with slimy, tubular fronds, and grow in tufts on -other weeds or on mud-covered rocks. Spores of various shapes are -scattered over the fronds, and are also contained in pod-like bodies -formed of the branchlets. This latter feature is, perhaps, the best -distinguishing characteristic of the genus, but it is not an easy matter -to identify the several species it contains. - -_E. tomentosus_ is very commonly found on _Fucus_ and other weeds, where -it forms matted tufts of slender threads of a yellowish-brown colour. -The threads are clothed with transparent cilia, and together form a -dense, spongy mass. The spores are contained in narrow pods supported on -short stalks. _E. littoralis_ is another common species, of a very -unattractive appearance. It grows in matted tufts on other weeds, on -rocks, mud, or any submerged object, and its spores are contained in -linear swellings of the branches. This species thrives well in brackish -water, and may be seen far up certain tidal rivers. - - [Illustration: FIG. 260.--_Ectocarpus granulosus_] - - [Illustration: FIG. 261.--_Ectocarpus siliculosus_] - - [Illustration: FIG. 262.--_Ectocarpus Mertensii_] - -Among the other species we may briefly mention _E. granulosus_, an -abundant and beautiful weed that grows in feathery tufts on rocks and -weeds, with elliptical, stalkless pods, quite visible to the naked eye, -freely distributed over the opposite branchlets; _E. siliculosus_, a -pale olive, parasitic species with lanceolate stalked pods, pointed and -striped; _E. sphærophorus_, a small, soft, brownish-yellow species, with -dense matted branches and spherical pods arranged either opposite to one -another or to a branchlet; and _E. Mertensii_, a pretty species that -grows on muddy rocks, freely branched but not matted, and having pods -enclosed by the branchlets. The last species is rare, but may be found -in Cawsand Bay and a few other localities about Plymouth Sound. The -genus includes several other species, but all these are more or less -rare. - -In the genus _Myriotrichia_ we have two parasitic species with fragile, -hair-like, jointed fronds bearing simple straight branches that are -covered with transparent fibres. In these the spore-cases are rounded -and transparent, and arranged along the main threads; and the dark olive -spores are readily visible within. In _M. filiformis_ the branchlets are -short, and clustered at intervals, thus giving a somewhat knotted -appearance to the threads, and both branches and branchlets are covered -with long fibres. The other species--_M. clavæformis_--is very similar, -but may be distinguished by the arrangement of the branchlets, which are -not clustered at intervals, but are distributed regularly, and are -longer towards the tip of the frond, giving the appearance of minute -fox-brushes. - - [Illustration: FIG. 263.--_Sphacelaria cirrhosa_] - - [Illustration: FIG. 264.--_Sphacelaria plumosa_] - -The genus _Sphacelaria_ contains several British weeds with rigid -branched and jointed fronds, most easily distinguished by the tips of -the branches, which are flattened, contain a granular mass, and have a -withered appearance. _S. cirrhosa_ forms hair-like tufts of slender -fibres with closely-set branches on small weeds, the tufts varying from -a quarter of an inch to over an inch in length. The fronds are naked at -the base, and the spore-cases, which are globular, are arranged on the -branches. _S. filicina_ is, as its name implies, of a fern-like -appearance, but is very variable in form. Its fronds vary from one to -three inches in length, and the spores are arranged singly in the axils -of the branchlets. Excluding some rarer species we mention one other -example--the broom-like _S. scoparia_, the frond of which is coarse and -very rigid, of a dark-brown colour, two or three inches long, with the -lower portion clothed by woolly fibres. Its spores are arranged in -clusters in the axils of the branchlets. - - [Illustration: FIG. 265.--_Sphacelaria radicans_] - -The last genus of the _Ectocarpaceæ_ is _Cladostephus_, which grows in -dark-green tufts, usually five or six inches long, in the deeper tide -pools. The fronds are cylindrical, branched, inarticulate, and rigid; -and the branchlets, which are short and jointed, are arranged in whorls. -The spores are situated in short accessory branchlets, or in masses at -the tips of the ordinary branchlets. _C. verticillatus_ is a very common -species, the whorled branchlets of which are deciduous in winter, when -the accessory branchlets that bear spores begin to develop. _C. -spongiosus_ is densely clothed with branchlets, and is of a bushy habit, -with a very spongy feeling. It is by some regarded as a variety of _C. -verticillatus_. - - [Illustration: FIG. 266.--_Cladostephus spongiosus_] - - [Illustration: FIG. 267.--_Chordaria flagelliformis_] - -The order _Chordariaceæ_ is characterised by a compound gelatinous or -cartilaginous frond, consisting of interlacing horizontal and vertical -threads. The spores are not external as in the _Ectocarpaceæ_, but -contained in cells in the substance of the frond. In the typical genus -the frond has a cylindrical, branched, cartilaginous axis, surrounded by -whorls of club-shaped threads and slender gelatinous fibres. We have -only one common species--_Chordaria flagelliformis,_ the fronds of which -are from four to twenty inches long, of uniform thickness throughout, -with long, glistening, soft and slimy branches among which the spores -are disposed. It may be found in rock pools at almost all levels. - -In the genus _Elachista_ there are some very small and peculiar weeds -that are almost sure to be overlooked by inexperienced collectors. They -are parasitic, and are composed of two kinds of jointed threads, the -inner of which are forked and combined into a tubercle, while the outer -are simple and radiate from the tubercle. The spores are attached to the -inner threads. The largest species (_E. fucicola_) is parasitic on -_Fucus_, growing in brush-like tufts about an inch long. Some of the -smaller ones are mere star-like tufts of no attractive appearance, and -would be disregarded as troublesome parasites by most young collectors, -but all of them are very interesting objects for the microscope. - -The members of the genus _Myrionema_ are similarly liable to be -neglected, for they are minute parasites appearing only as decaying -spots on larger weeds, but nevertheless form interesting studies for the -microscope. Like the last group, they have two sets of jointed fibres, -the inner being branched, and spread over the surface of the plant on -which it grows, while the outer are simple and stand out at right -angles, but all are united into a rounded mass by a gelatinous -substance. Perhaps the best known is _M. strangulans_, which infests -_Ulva_ and _Enteromorpha_, producing the appearance of small decaying -spots. - -In the genus _Leathesia_ we have other unattractive weeds, the jointed -and forked threads of which are all united together into tuber-like -fronds that are common on rocks and weeds between the tide-marks. There -are three or four species, all similar in general appearance, with the -spores distributed among the outer threads. These weeds cannot be -satisfactorily pressed and dried in the usual way, and should be -preserved in formaldehyde or dilute spirit, when they will always be -available for microscopic examination. - -The last genus of the _Chordariaceæ_ is _Mesogloia_, so called because -the central axis of loosely-packed, interlacing threads is covered with -gelatinous substance. Around this axis there are radiating, forked -threads which are tipped with clubbed and beaded fibres among which the -spores are distributed. One species (_M. vermicularis_), common in most -rock pools, is of a wormlike form, of a dirty olive or yellow colour, -with soft, elastic fronds growing in tufts from one to two feet long. -_M. virescens_, also a common species, is of a pale greenish or olive -colour, and very soft and slimy. Its stem is round and slender, freely -branched, with short, simple branchlets. - -The order _Dictyotaceæ_ contains the olive weeds with inarticulate -fronds, and superficial spores disposed in definite lines or spots. In -the typical genus (_Dictyota_) the frond is flat and forked, somewhat -ulva-like and ribless, and the spores are produced in little superficial -discs just beneath the cuticle. There is only one British species--_D. -dichotoma_--but that is a very common one, and it assumes a great -variety of forms as regards the shape and division of its fronds -according to the situation in which it grows, the fronds being broadest -and strongest in the deepest water. The root is covered with woolly -fibres, and the frond is regularly forked. - -One of the most interesting algæ of this order is the Turkey-feather -Laver (_Padina pavonia_), which is the only British representative of -its genus (see Plate VII.). Its very pretty fan-shaped fronds are of a -leathery nature, curved, fringed along the upper margin, and marked with -concentric lines. They often bear small leaflets, and are partially -covered with a powdery substance which renders them beautifully -iridescent when in the water. The root has woolly fibres, and the spores -are arranged in lines along the upper margin. This weed seems to be -confined to the south coast, where it may often be seen in the deeper -tide pools; though in some of the sandy bays of the Isle of Wight it may -be seen in shallow pools, and even in places left exposed to the air at -low tide. - -The genus _Zonaria_ contains a British species (_Z. parvula_) that -covers the rocks in round patches; and though moderately common is not -very frequently seen by collectors on account of the fact that it grows -in the deep crevices of rocks at or near low-water mark. Its frond is -flat and membranaceous, more or less divided into lobes, without veins, -and rather obscurely divided into concentric zones. It is attached to -the rock by fibres that proceed from the under surface of the frond, and -the spores are arranged in clusters beneath the superficial cells. - -_Cutleria multifida_, though not very abundant, is to be found on most -of our coasts; but since it grows almost exclusively beyond low-water -mark, it should be looked for on the beach after storms, or in the -fishermen's nets. The frond is olive-green, fan-shaped, rather thick, -and irregularly divided into forked branches; and it has a beautifully -netted surface. The spore-cases may be seen scattered over the surface -of the frond as so many black dots, and the antheridia are elongated, -cylindrical bodies attached to tufted filaments on all parts of the -frond. - -In the genus _Stilophora_ the root is discoid; the frond cylindrical, -hollow, and branched; and the spores arranged in clusters over the -surface. One species (_S. rhizodes_) is occasionally to be seen on the -south coast. It is of a yellowish colour, from six to twenty inches -long, and may be known by its long thread-like branches, with scattered, -forked branchlets, and by the wart-like projections of the stem which -contain the spores. This weed is often the source of some disappointment -to the collector, for it soon turns to a jelly-like mass when removed -from the water, and should therefore be mounted as soon as possible -after it has been collected. - -The fennel-like _Dictyosiphon foeniculaceus_ is abundant in tide pools, -where it may be seen in its best condition during spring and early -summer. Its root is a small disc, the frond is tubular, thread-like and -branched, and the branches bear hooked branchlets. The spores are naked, -and distributed either singly or in clusters over the surface of the -frond. - -Our next genus--_Punctaria_--contains a few British species with a -shield-shaped root, and a flat, membranous, undivided frond, without a -midrib, and having the spores disposed as minute dots over the surface. -A plantain-like species (_P. plantaginea_) has broad, leathery, -lanceolate fronds, of a dark olive-brown colour, usually from six inches -to a foot in length. Two other weeds--the broad-leaved _P. latifolia_ of -the tide pools, and the slender, tufted _P. tenuissima_, which is -parasitic on _Zostera_ and soe algæ, are sometimes regarded as mere -varieties of _P. plantaginea_. - -In the genus _Asperococcus_ the root is shield-shaped, and the frond is -a membranous tubular sac of two distinct layers. The colour is pale -green, and the general appearance very similar to that of _Ulva_. The -spores are arranged in small oblong clusters which appear as dark dots -on the surface of the frond. _A. compressus_ has slightly swollen flat -fronds of a linear lanceolate form, tapering below. It grows in deep -water, but is often washed up during storms. A second species--_A. -Turneri_--has large, puffy, green fronds, contracted at intervals, and -grows in tufts on rocks between the tide-marks, being specially partial -to muddy shores. The genus also includes the prickly _A. echinatus_, the -long, thin fronds of which grow in dense tufts in deep water. - -The last genus of the order is _Litosiphon_, a parasitic group -characterised by a cylindrical, cartilaginous, unbranched frond, with -scattered, naked spores. A very small species (_L. pusillus_) with -tufted green fronds grows parasitic on the fronds of _Chorda_ and the -stems of _Laminaria_. It is only two or three inches long, has a -reticulated surface, and is covered with minute jointed fibres. A still -smaller species (_L. laminariæ_), seldom exceeding half an inch in -length, forms brown tufts on _Alaria_, and the rounded apex of its frond -is covered with minute fibres. - -The order _Laminariaceæ_ contains olive, inarticulate algæ, mostly of -large size, and generally growing in deep water beyond the tide-marks. -Their spores are superficial, either covering the whole surface of the -frond or collected into indefinite cloudy patches. - - [Illustration: FIG. 268.--_Laminaria bulbosa_] - - [Illustration: FIG. 269.--_Laminaria saccharina_] - -The typical genus (_Laminaria_) is characterised by flat leathery, -ribless fronds, either simple or cleft, and supported on a stem which is -often very thick and strong. The old laminæ fall off every year, and are -replaced by new fronds. The well-known Tangle or Sea Girdle (_L. -digitata_), is a very common species on the rocks just beyond low-water -mark. It has a very thick, solid, cylindrical stem, and an oblong -leathery frond which is entire when young but deeply cleft later. Small -specimens may be found just above low-water mark, but fine large ones -are commonly washed up on the beach. Although this weed may not be -regarded as an acquisition from the collector's point of view, it will -generally repay a careful examination, as it frequently bears rare -parasitic species. The other common species are the Furbelows (_L. -bulbosa_), known by its flat stem with waved margin, oblong frond cleft -into narrow strips, and the hollow bulb or tuber just above the root; -and the Sugared Laminaria (_L. saccharina_) characterised by a round -solid stem, and a lanceolate, entire, membranous frond. The last species -is the one most commonly used by the sea-side cottager as a weather -indicator. - - [Illustration: PLATE VIII. - - SEA-WEEDS - - 1. Chorda filum - 2. Fucus vesiculosus - 3. Fucus canaliculatus - 4. Delesseria (Maugeria) sanguinea - 5. Rhodymenia palmata - 6. Chondrus crispus - 7. Ulva lactuca] - - [Illustration: FIG. 270.--_Alaria esculenta_] - -_Alaria esculenta_ is an edible species known as the Badderlocks in -Scotland, and also locally as the Henware, Honeyware, and the Murlins. -It has a fibrous root, and a stalked, lanceolate, entire frond with a -distinct midrib throughout. The stem is winged with finger-like -leaflets, in which the spores are arranged in oblong clusters. - -In the genus _Chorda_ the frond is a simple, cylindrical tube, divided -internally by numerous transverse membranes, and the spores are -distributed over the surface. The commonest species is _C. filum_ (see -Plate VIII.), the frond of which is very slimy, and often from ten to -twenty feet in length. In its young state it is covered with gelatinous -hairs, but these are worn off as the plant develops. A smaller species -(_C. lomentaria_) is sometimes found on our shores. Its fronds are -constricted at intervals, taper at the tip, and grow in tufts. It is -seldom more than a foot long, and is not of a slimy nature. - - [Illustration: FIG. 271.--_Sporochnus pedunculatus_] - -The _Sporochnaceæ_ have inarticulate, thread-like fronds, and the spores -are contained in oblong, stalked receptacles, each of which is crowned -with a tuft of slender jointed filaments. The typical genus contains -only one British species--_Sporochnus pedunculatus_--and even that is by -no means common. It is, however, a very pretty weed of a delicate -texture and pale olive-green colour. Its stem is long and slender, -pinnately branched, and the branches bear numerous small thread-like -tufts. - -The same order contains the genus _Desmarestia_, in which the frond is -long and narrow, thread-like or flattened, with a tubular jointed -thread running through it. Young specimens have marginal tufts of -branching filaments. The species decay very rapidly after removal from -the water, and should therefore be dried and mounted as quickly as -possible. _D. ligulata_, so named from the flat, strap-like frond, is -common on all our coasts. It is pinnately branched, and all the branches -and branchlets taper towards both ends. _D. viridis_ has a cylindrical, -thread-like and freely-divided frond, with opposite branches and -branchlets. It occurs more commonly on the northern shores. - - [Illustration: FIG. 272.--_Desmarestia ligulata_] - -The last order of olive-spored weeds is the _Fucaceæ_, some species of -which are so abundant between the tide-marks, from high-water to -low-water levels, that they form a very important characteristic of our -shores. They are mostly large, tough, and leathery weeds, without -joints, and the spores are contained in spherical receptacles embedded -in the substance of the frond. - -In the typical genus--_Fucus_--the root is a conical disc, and the frond -flat or compressed and forked. Most of the species are furnished with -one-celled air-vessels in the substance of the frond, and these serve to -buoy up the plants and keep them more or less erect when submerged. The -spore-receptacles are usually embedded near the tips of the branches, -but are sometimes borne on special branches or shoots. They are filled -with a slimy mucus and contain a network of jointed filaments. The weeds -are very hardy, capable of withstanding long exposures to air and sun, -and are sometimes to be found _above_ high-water mark, where they are -watered only by the spray of the waves for a brief period at intervals -of about twelve hours. Although they are not usually looked upon as -ornaments in the collector's herbarium, they will repay examination for -the tufts of smaller and more beautiful weeds to which they often give -attachment and shelter. - -Four species are common on our coasts, and these may be readily -distinguished by the most cursory examination. The Serrated Wrack (_F. -serratus_) has a flat, forked frond with toothed edges and a strong -midrib, ranging from one to four feet long, and no air-vessels. The -Knotted Wrack (_F. nodosus_--Plate VII.) may be known by its flattened, -thick and narrow frond, without a distinct rib, from one to five feet -long. The branches are narrow at the base, pointed at the tip, and are -jointed to short projections on the main stem; and both these and the -main stem have very large oval air-vessels. The spore-receptacles are -mounted on slender stalks which arise from projections on the branches, -and are of a bright yellow colour when mature. This species does not -grow so near to high-water mark as do the others. Another species, the -Twin-Bladder Wrack (_F. vesiculosus_--Plate VIII.)--is abundant -everywhere along the coast, and is largely used by agriculturists both -as manure and as fodder for cattle. The frond is flat, with a distinct -midrib, and a non-serrated edge. Air-vessels are not always present, but -when they are they usually occur in pairs, one on each side of the -midrib, and are globular in form. The spore-receptacles are situated at -the tips of the branches, are full of mucus, and are frequently forked. -The last of the common species is the Channelled Wrack (_F. -canaliculatus_--Plate VIII.), distinguished by a narrow frond, rounded -on one side and channelled on the other. It has no midrib or -air-vessels, and the fruit is contained in forked receptacles at the -tips of the branches. This is the smallest of the genus, and may be -found at all levels between the tide-marks. Stunted specimens may also -be seen in situations where they are never submerged, but watered only -by the spray of the highest tides. - - [Illustration: FIG. 273.--_Himanthalia lorea_] - -The genus _Himanthalia_ provides us with a single species (_H. lorea_) -which is very peculiar on account of the small size of the frond as -compared with the enormous dimensions of the spore-receptacles. The -young frond is a pear-shaped sac which soon becomes flattened into a -hollow disc. This disc then becomes solid, and concave above, and from -its centre there arises a bi-forked, strap-like receptacle that often -reaches a length of three or four feet, and may be mistaken for the -frond of the weed by those who do not take the trouble to examine it. -This weed is commonly known as the Sea Thong. - -Belonging to the genus _Cystoseira_ we have a few well-known weeds with -conical disc-roots, and shrubby fronds with woody stem and alternate -branches. The air-cells are in the substance of the frond, and the -spore-receptacles at the tips of the branches. One of the species (_C. -ericoides_) is of a heath-like habit, with a short, woody stem, and -slender branches bearing hooked, leaf-like branchlets. Its air-cells are -small, and are arranged singly near the tips of the branches; and the -spore-receptacles are cylindrical, with hooked points. This weed is -common on the south and west coasts, and may be readily distinguished by -the beautiful iridescence it displays when in the water. _C. fibrosa_ is -very similar in general form, but is larger, and the air-vesicles are -more conspicuous. It is not iridescent when in the water. A third -species is named _C. granulata_ from the rough and knobby appearance of -the stem, due to numerous oval projections, from some of which spring -the slender, much-divided branches. The air-vesicles are arranged in -groups of two or three, and the spore-receptacles are at the ends of the -branchlets. Our last example is _C. foeniculacea_, found on the south -coast only, and readily distinguished by the numerous blunt spines that -cover its long branches. The air-vesicles are narrow and pointed, and -situated just below the forkings of the branchlets. - - [Illustration: FIG. 274.--_Cystoseira ericoides_] - -We conclude our _résumé_ of the British sea weeds with a short -description of the Podded Sea Oak (_Halidrys siliquosa_), which grows in -the tide pools from high-water to low-water mark, the specimens -inhabiting the shallow pools being only a few inches long, while those -that grow in deep water often reach a length of three or four feet. It -is an olive, shrub-like weed, with a conical, disc-like root that -adheres very firmly to the rock, and a pinnately-branched frond with -leaf-like branchlets. The air-vesicles are cylindrical and pod-like, -divided internally into about ten cells, and the spores are contained in -globular receptacles at the tips of the branchlets. - -The young algologist will probably meet with many difficulties in his -attempts to classify his sea weeds and name the various species in his -collection. In dealing with an unknown weed we strongly recommend him to -first determine the order to which it belongs. The genus should next be -settled; and then, if possible, the species. It must be remembered, -however, that he who has made himself acquainted with the principles of -classification has done good work, and that it is far better to be able -to arrange the weeds into properly-classified groups than to merely -learn the names of the different species without regard to the relations -which they bear to one another. The following table will probably assist -the reader in the determination of the orders, but it must be remembered -that a microscope will often be necessary for the examination of the -spores and the minute structure of fronds. - - - CLASSIFICATION OF SEA WEEDS - - =A.= =Chlorospermeæ=--Green-spored weeds. Fronds usually - grass-green, and filamentous or membranous. - - 1. _Confervaceæ_--Frond thread-like, composed of cylindrical - cells placed end to end. Spores very minute, formed - within the cells. - - 2. _Ulvaceæ_--Frond grass-green or purple, flat or tubular. - Spores minute, ciliated, formed in the cells of the - frond. - - 3. _Siphonaceæ_--Frond a single, thread-like, branching cell, - or a spongy mass of many such cells. - - =B.= =Rhodospermeæ=--Red-spored weeds. Spores in globular - conceptacles. Tetraspores (four-clustered spores) in - globular or cylindrical cells. Frond red, reddish - brown, or purple. - - 4. _Ceramiaceæ_--Frond thread-like, jointed, one-siphoned, and - more or less covered with a layer of cortical cells. - Spores grouped in transparent, membranous sacs, - sometimes surrounded by a whorl of short branchlets. - - 5. _Spyridiaceæ_--Frond thread-like, jointed, one-siphoned, - more or less covered with small cells. Spores formed in - the upper cells of branched, jointed, radiating - threads, enclosed in a cellular membrane in external - conceptacles. - - 6. _Cryptonemiaceæ_--Frond more or less cartilaginous, composed - of numerous jointed threads compacted by gelatine. - Spores grouped without order in internal cells or in - external conceptacles. - - 7. _Rhodymeniaceæ_--Frond inarticulate, membranaceous, composed - of polygonal cells, the surface cells forming a - continuous layer. Spores in beaded threads in external - conceptacles. - - 8. _Wrangeliaceæ_--Frond inarticulate, thread-like, traversed - by a jointed tubular axis. Spores formed in the - terminal cells of clustered, branching, naked threads. - - 9. _Helminthocladiæ_--Frond cylindrical, gelatinous, composed - of filaments imbedded in gelatine. Spores formed on - branching, radiating threads that are enclosed in the - frond without conceptacles. - - 10. _Squamariæ_--Frond lichen-like, rooted by under surface, - composed of _vertical_ filaments imbedded in firm - gelatine. Spores in beaded threads in wart-like - projections. - - 11. _Spongiocarpeæ_--Frond cylindrical, branching, - cartilaginous, composed of netted filaments imbedded in - firm gelatine. Spores large, in radiating clusters in - wart-like excrescences. - - 12. _Gelidiaceæ_--Frond cartilaginous, inarticulate, composed - of hair-like filaments. Spores attached to slender - threads in internal conceptacles. - - 13. _Sphærococcoideæ_--Frond leaf-like or thread-like, - inarticulate, cellular. Spores formed in beaded threads - in external conceptacles. - - 14. _Hapalidiaceæ_--Frond minute, calcareous, composed of a - single layer of cells. - - 15. _Corallinaceæ_--Frond calcareous. Spores in tufted threads - at the bases of the conceptacles. - - 16. _Laurenciaceæ_--Frond rounded or flattened, branching, - inarticulate, cellular. Spores in external oval or - globular conceptacles. Tetraspores irregularly - scattered over the branches. - - 17. _Rhodomelaceæ_--Frond leafy, thread-like, or jointed, - composed of polygonal cells. Spores in external - conceptacles. Tetraspores in distorted branchlets or in - receptacles. - - =C.= =Melanospermeæ=--Olive-spored weeds. Frond tough, leathery. - Spores in globular cavities in substance of frond. - - 18. _Ectocarpaceæ_--Frond jointed, thread-like. Spores attached to - or imbedded in branchlets. - - 19. _Chordariaceæ_--Frond gelatinous or cartilaginous, composed of - interlacing vertical and horizontal filaments. Spores - internal, attached to the filaments. - - 20. _Dictyotaceæ_--Frond inarticulate. Spores superficial, arranged - in definite spots or lines. - - 21. _Laminariaceæ_--Frond inarticulate. Spores covering the whole - frond or in cloud-like patches. - - 22. _Sporochnaceæ_--Frond inarticulate. Spores attached to jointed - filaments which are either free or compacted. - - 23. _Fucaceæ_--Frond inarticulate, large and tough. Spores in - globular cavities. - - - - - CHAPTER XVI - - _THE FLOWERING PLANTS OF THE SEA-SIDE_ - - -A considerable number of our flowering plants exhibit a decided -partiality for the neighbourhood of the sea, and many are to be found -only on the sea cliffs or in salt marshes not far from the shore. The -principal of these will be now briefly described, dealing first with the -monocotyledons, and then with the more highly organised dicotyledons. - -The chief distinguishing features of these two groups have already been -referred to, but it will be advisable here to give them in somewhat -fuller detail. - - [Illustration: FIG. 275.--TRANSVERSE SECTION OF THE STEM OF A - MONOCOTYLEDON] - -The _monocotyledonous plants_, then, are those in which the stem is more -or less woody and cylindrical, without either true bark or pith; and the -woody tissue is not arranged in concentric rings, but in isolated -bundles, which first bend inwards, as they rise, towards the centre of -the stem, and then curve outwards towards the surface, which is hardened -by the formation of a layer of hard woody matter. As a rule the stem is -unbranched, and its growth takes place by a single bud at the summit. In -nearly all of them the leaves are long and narrow, with veins running -parallel throughout their length; and the parts of the flower are -arranged in whorls of three or six. The outer whorl of the flower is -often a conspicuous white or coloured _perianth_ (that portion of the -flower which lies outside the anthers), but in some the perianth is -absent, the flower being protected by scaly bracts. The seeds are -produced in a case called the ovary, and are fertilised by pollen grains -which are developed in the anthers. When the pollen grains are set free -they alight on the adhesive stigma, and grow, sending their tubes down -into the ovary. The term monocotyledon is applied to these plants -because the embryo has only one cotyledon or seed-leaf. - - [Illustration: FIG. 276.--LEAF OF A MONOCOTYLEDON] - -The principal divisions of this group are the _Glumaceous -Monocotyledons_, in which the flower has no perianth, but is enclosed in -scaly bracts or husks called glumes; and the _Petaloid Monocotyledons_, -distinguished generally by the presence of a more or less conspicuous -white or coloured perianth. The first of these includes the rushes, -sedges, and grasses; and the other contains the lilies and orchids, with -their allies, together with certain aquatic and semi-aquatic plants. - -Among the Grasses there are several species that show a preference for -the immediate neighbourhood of the sea, some growing luxuriantly at the -bases of the cliffs where the beach is sandy, and others thriving best -in salt marshes; but before dealing with these individually we shall -note the general characteristics of the order (_Gramineæ_) to which they -belong. - -Grasses are distinguished by their jointed stems, which are usually -hollow, with a split sheath, and bearing alternately arranged narrow -leaves. The flowers, which are disposed either in spikes (sessile -flowers arranged along a common axis) or in panicles (flowers stalked -and arranged as in fig. 281), consist of scale-like bracts enclosing the -stamens and the pistil. The bracts are in two series, the outer usually -consisting of two _glumes_, and the inner of two _pales_; the upper -pale, however, has two ribs running through it, and is therefore usually -looked upon as a combination of two. In some species both glumes and -pales are absent; but the former, when present, enclose one or more -flowers, among which may be some that are abortive. The stamens are -generally three in number, attached to the base of the flower; and the -ovary is superior or free, that is, it grows above the other parts of -the flower, and contains but one seed. - -It will be convenient at this stage to refer briefly to the two -principal methods by which the pollen of flowers is transferred to the -stigmas for the purposes of fertilisation, and to see how various -species are structurally adapted to the means by which the transfer is -brought about. - -Speaking generally, we may classify flowers into those which are -fertilised by the wind (anemophilous flowers) and those in which the -pollen is transferred by insects (entomophilous flowers). The former -offer no attractions to allure the various forms of insect life. They -are, generally speaking, very inconspicuous, being of small size and -having no bright corollas. None of them are scented, nor do they produce -the sweet nectar that forms the principal food of so many insects. Their -anthers are borne on long filaments, so that they are exposed freely to -the wind; and they produce abundance of pollen to compensate for the -very wasteful method of wind-dispersion. The pollen, too, is not very -adherent, so that it may be readily carried away by the breeze; and the -plants concerned often produce their flowers early in the spring, before -the leaves have appeared, thus giving the wind very free play. - - [Illustration: FIG. 277.--EXPANDED SPIKELET OF THE OAT - G. glumes; P.e, outer pale; P.i, inner pale; A, awn; F.S, a sterile - flower. The stamens and the feathery stigmas of the fertile flower - are also shown] - -Insect-fertilised flowers, on the other hand, are usually of attractive -appearance; and, though often small and inconspicuous individually, they -are in such cases grouped together in more or less showy clusters. They -are also usually scented, and supply nectar and pollen to the insects -which they allure. Some are fertilised by insects that fly by day, and -these often close their petals on the approach of night, thus protecting -their pollen during the period in which their fertilisers sleep. Others, -fertilised by nocturnal insects, always spread their petals during the -night, and generally protect their pollen from waste by sleeping -throughout the day. As a rule, too, these night-bloomers have large and -pale-coloured petals that are more easily seen by night; they also evolve -a powerful scent to aid the insects in searching them out. - -It will be seen that the economic relationship existing between flowers -and insects is a mutual one, the latter visiting the former in order to -obtain food, while the former derive in return the advantage of a direct -transfer of pollen from flower to flower. - -It is a well-known fact that the self-fertilisation of a flower often -results in the development of very weak seedlings as compared with those -that are produced by crossing; and it often happens that the pollen of a -flower is incapable of producing the least effect when deposited on the -stigma of the same bloom. In some cases the contact of the pollen of a -flower with its own stigma will even act as a poison, causing the whole -to shrivel and die; and truly wonderful are the varied means by which -flowers contrive to secure a cross-fertilisation. It is here that the -work of the wind and insects proves so valuable to flowers; but, in -addition to this, a very large number of flowers are absolutely -incapable of self-fertilisation, for the anthers and the stigma are not -mature at the same time, or they exist in separate flowers, either on -the same plant or on distinct plants of the same species. It is most -interesting and instructive to study the many contrivances by which -flowers compel certain insects to convey the pollen exactly in the way -that best serves their purpose, sometimes even entrapping them after -they have been allured, and not allowing them to escape until they are -thoroughly dusted with the pollen which they are required to convey; but -it is hardly our province to enter more fully into this matter in these -pages. - -An examination of the grasses will show at once that they are adapted -for fertilisation by the wind. The flowers produce no nectar; and, -consistently, develop no bright petals and evolve no odours to attract -insects. On the other hand, their anthers produce abundance of -lightly-adhering pollen, and are mounted on long filaments which hold -them well exposed to the wind; and the stigmas are well adapted for -catching the scattered grains, being long and protruding, and often -covered with sticky hairy or feathery appendages. - -Although the flowers of grasses are generally wanting in attractive -colours, the clusters of blossoms are often very graceful and pretty, -especially when the large anthers, covered with bright-yellow pollen, -dangle in the breeze. - -We will now briefly describe the principal British grasses that grow -chiefly or exclusively in the immediate neighbourhood of the sea. - -The Sea Hard Grass (_Lepturus filiformis_) is a perennial species, -usually about six inches in height, very common on some sandy coasts, -and found in flower during the hottest months of the summer. The flowers -are arranged in simple spikes, on slender erect stems; and the glumes, -which are united at their bases, enclose a single bloom. - -In similar situations we may find the Sea Lyme Grass (_Elymus -arenarius_), a tall species, often reaching a height of four feet, with -glaucous rigid leaves. The flowers are arranged in a simple spike, but -the spikelets are clustered two or three together. This species flowers -in August. - -Of the well-known Barley Grasses there is one species (_Hordeum -maritimum_) that has its habitat along the coast. Like the others of its -genus, the spikelets are arranged in threes, each bearing a single -flower, and the pales have long slender processes (_awns_) which -constitute the so-called beard. It also resembles the common Meadow -Barley Grass in having the middle flower of each three perfect, while -the two laterals are abortive, but may be distinguished by its rough and -bristly glumes, and the semi-oval form of the pales of the lateral -flowers. It is a somewhat stunted species, sometimes only five or six -inches in height, and may be found in flower about Midsummer. - -The Brome Grasses have also a representative of a sea-loving nature, -which is to be found in fields near the cliffs. It is the Field Brome -Grass (_Bromus arvensis_), an annual grass that grows to a height of two -or three feet. Brome grasses generally are known by their loose panicles -of flowers, lanceolate and compressed spikelets, and awned florets -enclosed in unequal glumes; and _B. arvensis_ may be distinguished by -its hairy leaves and stem-sheath, and the drooping panicle with the -lower peduncle branched. - - [Illustration: FIG. 278.--THE SEA LYME GRASS] - -Among the Meadow Grasses we have three or four coast species. In these -the florets are in panicles and are not awned. The outer glumes are -keeled and traversed by several veins; and the lower pales are also -keeled, with five or more nerves. The Sea Meadow Grass (_Poa maritima_) -grows in salt marshes near the sea, its erect rigid panicles reaching a -height of about eight or ten inches. It has a creeping root, and its -leaves are curved inward at the margins. The Procumbent Meadow Grass -(_P. procumbens_) and a variety of the Reflexed Meadow Grass (_P. -distans_) are also plentiful in salt marshes. The former may be known by -the short rigid branches of its panicle and the five ribs of the lower -pales; and the latter is much like _P. maritima_, but grows taller, and -its spikelets are crowded. The Wheat Meadow Grass (_P. loliacea_) grows -on sandy shores. Its spikelets are arranged singly and alternately along -the central axis, and the upper glume reaches to the base of the fourth -floret. This species flowers in June, but the other three of the same -genus bloom from July to September. - -The reader is probably acquainted with the Fescue Grass, with its awned -flowers arranged in one-sided panicles. There are no less than seven -species, one of which--the Single-husked Fescue (_Festuca -uniglumis_)--grows on sandy shores, flowering in June and July, and -reaching a height of from nine to twelve inches. The panicles are -upright and unbranched, and the species may be readily known by the -flowers, which are compressed, with long awns, and with the lower glumes -wanting. - -_Knappia agrostidea_ is a dwarf species, rarely exceeding four inches in -height, that is found on certain sandy shores, but is very local. Its -flowers are arranged in a simple spike, the spikelets being solitary and -unilateral, with only a single flower, and the pales are shaggy. The -plant has several stems which bear short, rough leaves. - -The Mat Grass or Sea Reed (_Ammophila arundinacea_) is common on many -sandy coasts, where it grows to a height of three or four feet, and -flowers in July. The white flowers are clustered in dense cylindrical, -pointed spikes; and the leaves are of a glaucous green colour, rigid, -and curved inward at the edges. - -Dog's-tooth Grass (_Cynodon dactylon_). This species has a creeping -root, and the leaves are downy on the under side. The flowers are -arranged in a compound spreading spike, of three to five parts, and the -spikelets are of a purplish colour, ovate in form, and arranged in -pairs. The glumes are equal in size. It is found on sandy shores, grows -to a height of about six inches, and flowers in July. - -A species of Canary Grass (_Phalaris arundinacea_) is also to be seen on -sandy coasts. Unlike the other species of the same genus, its flowers -form an erect spreading panicle, and the glumes are not keeled. It is -also taller than the common canary grass of waste places, often reaching -a height of three feet, and is commonly known as the Reed Canary Grass. - - [Illustration: FIG. 279.--_Knappia agrostidea_] - - [Illustration: FIG. 280.--THE DOG'S-TOOTH GRASS] - - [Illustration: FIG. 281.--THE REED CANARY GRASS] - -The Sea Cat's-tail Grass (_Phleum arenarium_) is common on many coasts. -It is much smaller than the common species of Cat's-tail, being -generally less than a foot high. The spike is of an elongated oval form, -blunt at the tip and narrow at the base; and the glumes are narrow, -pointed at both ends, and fringed. Each spikelet has but one flower. - -In salt marshes we occasionally meet with the Perennial Beard Grass -(_Polypogon littoralis_), but it is somewhat rare. It has a creeping -root, and the flowers form a somewhat dense spike-like panicle. The -glumes have a slender awn. It grows to a height of one to two feet, and -flowers in July. - -The Tuberous Fox-tail Grass (_Alopecurus bulbosus_) is another rare -grass of the salt marshes, where it grows to the height of twelve to -sixteen inches, flowering in May and June. The genus to which it belongs -is very closely allied to _Phleum_, but may be distinguished by having -only one pale to each flower, and this species has a long awn attached -to the back portion. The panicle, too, is cylindrical and slender, the -glumes quite free and abruptly pointed, and the awns longer than the -pales. - -The last of the sea-side grasses are two rare species of Cord Grass -(_Spartina_), both of which are found in salt marshes. In these the -inflorescence is a compound spike, with one-sided spikelets inserted in -a double row. The glumes are keeled and pointed; the pales cleft, -pointed and without awns; and the styles two in number, very long. The -only British species of the genus are the two (_S. stricta_ and _S. -alternifolia_) referred to above. They both grow to a height of about -eighteen inches, and flower in late summer. In the former the spikes -number two or three, and are longer than the leaves; and the outer glume -is hairy, with a single nerve. The latter, which is the rarer of the -two, bears several spikes, shorter than the leaves; and the outer glume -has five nerves. - -Certain of the sedges (order _Cyperaceæ_) are also more or less familiar -to the sea-side naturalist, and must therefore receive a small share of -our attention. In general terms these are grasslike, monocotyledonous -plants, the stems of which are solid, jointed, and frequently angular. -The leaves are very similar to those of grasses, except that the -sheaths, which surround the stem, are not split. The flowers are -generally arranged in a spike, overlapping each other, and each one -supported on a scale-like bract. In some sedges the flowers are perfect, -each one possessing both stamens and pistil; but in some species the -flowers are unisexual, some bearing stamens and no pistil, and others -pistil only. The stamens are generally three in number, the ovary is -superior, and the stigmas either two or three. - -Sedges abound in moist places, some being peculiar to salt marshes, -while others grows on sandy shores; and a few of the British species of -the latter habitat are often so abundant that their creeping roots bind -the sand together, effectually holding it in place while the surrounding -portions of the beach are mercilessly driven by the wind. - -A few of the sea-side sedges belong to the genus _Carex_, in which the -flowers are imperfect, and the fruit is enclosed in the outer parts of -the flower. _C. extensa_ thrives in salt marshes, growing to a height of -a foot or more, and flowering about midsummer. Its fertile flowers form -oblong erect spikelets, while the barren spikelets are solitary. The -bracts are long and leafy, with short sheaths surrounding the stem. The -leaves are curved in at the edges, and the fruit is oval and ribbed, -with a short straight beak. - -On sandy shores the Sea Sedge (_C. arenaria_) is often common, and its -underground stems are used for sarsaparilla. It is a perennial species, -growing to a height of about nine inches, and flowering in June and -July. The flowers grow in an oblong interrupted spike, the upper -spikelets being barren, and the intermediate ones barren at the tip. -The fruit is oval, veined, and winged. - -Another species of this genus--the Curved Sedge (_C. incurva_)--is -sometimes to be seen on sandy shores, but it is rare, and is also a very -small sedge, growing only to a height of about three inches. It derives -its specific name from its curved stem, and may be further distinguished -by its channelled leaves and the globular mass of spikelets which are -barren on the top. - - [Illustration: FIG. 282.--MALE AND FEMALE FLOWERS OF _Carex_, - MAGNIFIED] - -Some of the so-called rushes belong to the same order as the sedges, and -a few of these are more or less restricted to the neighbourhood of the -sea. The Salt-marsh Club Rush (_Scirpus maritimus_), as its name -implies, is to be found in marshes near the sea. It is very variable in -height, ranging from one to three feet, and displays its dense terminal -cluster of spikelets in July and August. In this genus all the flowers -are perfect, the glumes imbricated and bristled; and the present species -may be distinguished by the glumes being divided into two sharply -pointed lobes. A variety of _S. lacustris_ may also be found on the sea -shore, but it is somewhat rare. It has a leafless glaucous stem, and -flowers arranged in compound spikes. The glumes are rough, and contain a -compressed fruit. - -A very small species of the Spike Rush (_Eleocharis parvula_), growing -only one or two inches high, is sometimes found on the muddy shores of -Ireland. It has perfect flowers, in a single terminal spikelet. The -leaves are very narrow, growing from the base of the plant; and the -round stem is enclosed in a single leafless sheath. - -The true rushes belong to the order _Juncaceæ_. These have fibrous roots -and narrow leaves, and bear clusters of brown flowers. The perianth -consists of six parts, and the stamens are usually six in number. The -ovary is generally three-celled, developing into a three-valved capsule. -The Lesser Sea Rush (_Juncus maritimus_) is common in salt marshes, -growing to a height of two or three feet, and flowering in July. It has -a rigid leafless stem, bearing lateral clusters of flowers. The segments -of the perianth are very narrow and sharp, and the seeds are enclosed in -a loose testa. Closely allied to this species is the Great Sea Rush (_J. -acutus_), which grows three or four feet high on sandy shores. In -general characteristics it resembles_ J. maritimus_, but the segments of -the perianth are oval and have thin transparent margins; and it is a -much rarer species. - - [Illustration: FIG. 283.--THE SEA SEDGE] - - [Illustration: FIG. 284.--THE CURVED SEDGE] - - [Illustration: FIG. 285.--THE GREAT SEA RUSH] - -We now pass to the peculiar Sea Grasses or Grass Wracks (_Zostera_) -which grow in salt water. They belong to the order _Naiadaceæ_, and are -characterised by cellular leaves with parallel veins, and inconspicuous -unisexual or bisexual flowers. The perianth, when present at all, -consists of two or four scale-like parts, and the stamens correspond in -number with these. The ovary is free, and the carpels, one or more in -number, contain each a single ovule. In _Zostera_ the flowers are -imperfect, and seem to grow in the slit of the leaf. There are two -species, both of which grow in shallow water close to the shore, often -in such dense masses that they impede the progress of boats. They have -long creeping stems that lie buried in the sand, giving off numerous -root-fibres, and send up to the surface slender branches that bear -grass-like leaves. The flowers are unisexual, and are arranged in two -rows on the same side of a flattened stalk that is enclosed in a sheath -formed by short leaves. They have no perianth, the male flowers being -composed of a single anther, and the female of a one-celled ovary -containing a single ovule, and surmounted by a style with two long -stigmas. - -There are two species--the Broad-leaved Grass Wrack (_Z. marina_) with -leaves one to three feet long and traversed by three or more parallel -veins, and the Dwarf Grass Wrack (_Z. nana_), the leaves of which are -less than a foot long, with veins numbering one to three. There is a -variety of the former, however, named _Angustifolia_, in which the -leaves are much narrower than usual, and the veins fewer in number. - - [Illustration: FIG. 286.--THE BROAD-LEAVED GRASS WHACK] - - [Illustration: FIG. 287.--THE SEA-SIDE ARROW GRASS] - - [Illustration: FIG. 288.--THE COMMON ASPARAGUS] - -The order _Alismaceæ_, which contains the water plantains, arrow-heads, -and other semi-aquatic plants, has a representative of marine tendencies -in the Sea-side Arrow Grass (_Triglochin maritimum_). The flowers of -this order are bisexual, with six stamens and a six-parted perianth. The -fruit consists of many carpels; and, although the plants are -monocotyledons, their leaves have netted veins; and altogether they -somewhat resemble the ranunculaceous exogens. The Sea-side Arrow Grass -is abundant in some salt marshes, growing to a height of about a foot, -and produces loose simple spikes of green flowers all through the -summer. The leaves are radical, narrow and fleshy; and the ovary -consists of six carpels. - -Of the interesting order _Liliaceæ_ we have only one plant of the coast, -and even that--the _Asparagus_--is not by any means generally common. It -is the same plant that is so largely cultivated as an article of diet, -and which is so highly valued on account of its diuretic properties. It -is moderately common on parts of the south coast, particularly in the -Isle of Portland and in West Cornwall, and its general appearance is so -graceful that it is largely employed as an ornamental garden plant. The -stem is erect and freely branched, bearing feathery bunches of bristled -leaves and pale-yellow axillary flowers. As is the case with the -_Liliaceæ_ generally, the flowers are bisexual, with a six-parted -perianth, six stamens, and a three-celled superior ovary; and the last -named, in the Asparagus, forms a bright-red berry in the autumn. - -We have now to leave the monocotyledonous plants and pass on to the -_dicotyledons_, which form the most highly developed of the primary -divisions of the vegetable kingdom. A few of the general characteristics -of this group have already been given, but we must now look rather more -closely into the nature of the plants included. - -The class receives its name from the presence of two cotyledons or -seed-leaves in the embryo plant, and is also known as the _Exogenæ_ -because the stems increase in thickness by the addition of zones of -woody tissue at the exterior. When the young dicotyledonous plant first -appears above the ground, the two cotyledons, which formerly served to -shelter the immature bud, usually appear as tiny fleshy leaves; but -these soon wither away, while the bud produces the more permanent leaves -that are of a very different structure. A section of the stem will -reveal distinct pith, wood, and bark, the wood being more or less -distinctly divided into wedge-shaped masses by rays from the pith; and, -in the case of perennial stems, the wood is arranged in concentric -rings, the number of which correspond approximately with the years of -growth. The leaves of exogens have their veins in the form of a network, -and the parts of the flower are generally arranged in whorls of two or -five or of some multiple of these numbers. - -The flowers always have stamens and pistil, but in some these organs -exist in separate flowers, either on the same plant, or on different -plants of the same species, and the ovules are nearly always contained -in a case called the ovary. - -Dicotyledons are divided into three main groups, the division being -based on the structure of the flowers. They are the _Apetalæ_ in which -the petals are absent, but the perianth is frequently petaloid, though -it is occasionally also absent; the _Gamopetalæ_, in which the petals -are united; and the _Polypetalæ_, in which the petals are always -distinct. - -Dealing with these divisions in the above order we come first to the -Spurges, three species of which occur on sandy shores. They belong to -the order _Euphorbiaceæ_, which includes, in addition to the spurges, a -number of herbs, trees, and shrubs with entire leaves often a milky -juice, and small flowers, sometimes enclosed in calyx-like bracts. The -flowers may have one or several stamens, and the perianth, if present, -consists of three or four parts; but perhaps the best distinguishing -feature of the order is the nature of the fruit, which separates -elastically into three carpels. - - [Illustration: FIG. 289.--THE SEA SPURGE] - -The Sea Spurge (_Euphorbia Paralias_) is commonly seen on sandy shores, -where its yellow flowers bloom in late summer and in autumn. It may be -distinguished among the numerous species of the genus by its narrow -oblong imbricated leaves, of a tough leathery nature, the broad -heart-shaped bracts, and the wrinkled capsules containing smooth seeds. -The Portland Spurge (_E. portlandica_) is a similar plant, found in -similar situations, and flowering from May to September. Its leaves are -oval and narrow, obtuse, and of a glaucous colour, and the bracts are -more triangular than those of the last species. The capsules are -slightly rough, as are also the seeds. There is yet another sea-side -spurge--the Purple Spurge (_E. peplis_)--a somewhat rare plant, found on -some of the sandy shores of the south of England. It grows to about -eight or nine inches in length, and blooms in late summer, the flowers, -like those of most of the spurges, being yellow. The stem is of a -glaucous colour, and trails along the ground; the leaves are opposite -and somewhat heart-shaped, and the flowers solitary. This species may be -distinguished from other spurges by its stipuled leaves. - -On sandy cliffs we sometimes meet with the Sea Buckthorn (_Hippophaë -rhamnoides_)--a spiny shrub, ranging from about two to seven feet in -height, the bark of which is covered with a silvery scaly scurf that -forms a beautiful object for the microscope. It is the British -representative of the Oleasters (order _Eleagnaceæ_). The leaves are -alternate, lanceolate, with a silvery surface; and the flowers are -small, green and unisexual. The male flowers grow in catkins, each -arising from a scaly bract, and have a green perianth. The female -flowers have a tubular perianth, and a free one-celled ovary. The latter -forms a hard nut-like fruit, which is surrounded by a succulent mass -formed by the former. This shrub flowers in the spring, while the leaves -are still very small. - - [Illustration: FIG. 290.--THE PURPLE SPURGE] - - [Illustration: FIG. 291.--THE SEA BUCKTHORN] - -Of the order _Polygonaceæ_, which includes the docks, knot grasses, -buckwheats, and sorrels, we have two sea-side representatives, both -belonging to the typical genus _Polygonum_. These are the sea-side Knot -Grass (_P. maritimum_) and Ray's Knot Grass (_P. Raii_). The plants of -this order are herbs, characterised by their alternate leaves with -sheathing stipules; and small flowers, usually bisexual, often with a -coloured perianth. Most of the species are remarkable for their -astringent and acid properties. In the genus _Polygonum_ the flowers are -usually in spikes or racemes; the perianth funnel-shaped, regular, and -five-cleft. The stamens vary from five to eight in number, and the -styles number two or three. The fruit is a small angular nut, usually -enclosed in the perianth. - -The sea-side Knot Grass is very common on some parts of the shore, where -it grows from one to three feet long, and flowers in August. The stem is -recumbent, tough and woody, bearing fleshy glaucous leaves with curled -edges. It may be further distinguished from the other knot grasses by -its long stipules, with freely-branching veins, and by the length of the -fruit exceeding that of the perianth. As in the other knot grasses, the -flowers arise from the axils of the leaves. - -Ray's Knot Grass is very much like the common knot grass so abundant in -all waste places, the leaves being flat; and the stipules, shorter than -in the last species, having but few veins; but while in the latter the -fruit is shorter than the calyx, in _P. Raii_ it is longer. This species -is found on many sandy shores, and flowers in July and August. - -The order _Chenopodiaceæ_ is particularly rich in sea-side plants, more -than a dozen of the British species growing almost exclusively near the -shore. They are mostly inconspicuous plants, with small flowers which -are sometimes unisexual. The perianth is deeply divided, and the stamens -are inserted in its base, opposite the divisions. The ovary is free, -containing a single ovule. - -The typical genus (_Chenopodium_) contains the weeds designated by the -name of Goosefoot, all characterised by their straggling stems and small -flat leaves. One species (_C. botryoides_) is common on some sandy -shores. It is a small weed, its prostrate stem measuring only a few -inches in length. The leaves are triangular and fleshy, and the flowers -are arranged in dense leafy clusters. A variety of the Red Goosefoot -(_C. rubrum_) is also found on the coast. It is of a reddish colour, -with rhomboid leaves and short crowded spikes of flowers. - - [Illustration: FIG. 292.--_Chenopodium botryoides_] - -On muddy shores we meet with the Common Beet (_Beta maritima_), the -leaves of which are often cooked and eaten where the plant is abundant; -and it is this species from which the different varieties of garden beet -and mangold wurzel have been produced by cultivation. There are two -distinct varieties of the wild plant. In one the root and leaves are of -a purple colour, while in the other they are of a yellowish green. The -former has been cultivated for its root, while the latter is sometimes -grown for the leaves. In the wild state it has many stems, the lower -parts being more or less procumbent, and the leaves are fleshy, -gradually narrowing down into the stalk. The flowers, which are arranged -in long, simple, leafy spikes, are bisexual, with a five-parted -perianth, five stamens inserted opposite each segment, in a fleshy ring -and a flattened one-celled ovary which develops into a one-seeded -utricle. - -In similar situations we meet with two species of Sea Purslane -(_Obione_), in which the flowers are unisexual, both male and female -flowers being on the same plant. They are also distinguished from most -other Chenopods by the perianth adhering to the wall of the ovary. The -Shrubby Sea Purslane (_O. portulacoides_) is, as its name implies, a -shrubby plant. It grows to a height of eighteen inches or two feet, -bearing silvery oval lanceolate leaves and sessile fruit. The other -species referred to--the Stalked Sea Purslane (_O. pedunculata_)--is -herbaceous, with oval, mealy leaves, and stalked fruit. - - [Illustration: FIG. 293.--THE FROSTED SEA ORACHE] - - [Illustration: FIG. 294.--THE PRICKLY SALT WORT] - -The Oraches (genus _Atriplex_) resemble the Purslanes in the granular -mealiness of the foliage, and the two are so closely allied that they -are often placed in the same genus. Oraches are most readily -distinguished among the Chenopods by the two bracts which enclose the -fruit and enlarge after flowering; and, like the Purslanes, they have -unisexual flowers, both male and female being on the same plant. Three -of our five British species are sea-side plants. The Frosted Sea Orache -(_A. arenaria_) grows on sandy shores, about six or eight inches in -height, and flowers during late summer and autumn. It may be known by -its buff-coloured stem, with triangular or rhomboidal, jagged, silvery -leaves, and clusters of sessile flowers in the axils of the leaves. -Another species (_A. Babingtonii_) may be seen on both rocky and sandy -shores, usually from one to two feet in height, and flowering from July -to September. Its stem is procumbent, green with reddish stripes; leaves -oval-triangular, lanceolate towards the top, three-lobed at the base of -the stem, light green, with a mealy surface; flowers in terminal -clusters as well as in the axils of the leaves. A third species--the -Grass-leaved Orache (_A. littoralis_) grows in salt marshes. All its -leaves are grass-like and entire, and the stem is generally marked with -reddish stripes as in _A. Babingtonii_. The flowers, too, are in sessile -axillary clusters only. This plant reaches a height of from one to two -feet, and flowers in the late summer. - -The Prickly Salt Wort (_Salsola kali_) is a very common sea-side plant -on some of our coasts, and may be recognised at a glance by its general -form and habit. The stem is very much branched and prostrate, forming a -very bushy plant about a foot in height. It is also very brittle and -succulent, furrowed and bristly, and of a bluish-green colour. The -leaves are fleshy, awl-shaped, nearly cylindrical, with a spiny point, -and little prickles at the base. The flowers are axillary and solitary. -This plant and its exotic allies are very rich in alkaline salts, -particularly carbonate of soda, and were formerly the principal source -from which this compound was obtained. - - [Illustration: FIG. 295.--THE CREEPING GLASS WORT] - -Our last example of the sea-side chenopods is the Glass Wort -(_Salicornia_), which thrives in salt marshes. In this genus the stem is -jointed and the flowers bisexual. The Jointed Glass Wort (_S. herbacea_) -is common in most salt marshes, where its erect, herbaceous, leafless -stem may be seen growing to a height of a foot or more. The joints are -thickened upwards, and shrink to such an extent when dry that the upper -part of each segment of the stem forms a membranous socket into which -fits the base of the next segment above. The flowers are arranged in -dense tapering spikes, also jointed, with a cluster of three flowers on -the two opposite sides of the base of each segment. Each flower is -composed of a perianth, closed with the exception of a small aperture -through which the stigma and, later, the stamens protrude. The Creeping -Glass Wort (_S. radicans_) has a woody procumbent stem, with the joints -only slightly thickened, and the spikes do not taper so much as in _S. -herbacea_. Both these plants yield considerable quantities of soda, and -they are named 'Glass Wort' because they formerly constituted one of the -sources from which soda was obtained for the manufacture of glass. - -We now come to those flowers in which both calyx and corolla exist, and -shall deal first with the division _Gamopetalæ_ or _Monopetalæ_, in -which the petals are united. - -Our first example of this division is the Seaside Plantain (_Plantago -maritima_), of the order _Plantaginaceæ_. This is a stem-less -herbaceous plant, with ribbed leaves and small green flowers, common on -many parts of the coast, and also found on the mountains of Scotland, -flowering throughout the summer. It may be distinguished from the other -plantains by its narrow fleshy leaves. As in the other species, the -flowers form a cylindrical spike. - - [Illustration: FIG. 296.--THE SEA-SIDE PLANTAIN] - - [Illustration: FIG. 297.--THE SEA LAVENDER] - -The order _Plumbaginaceæ_ contains several sea-side plants, including -the Sea Pink or Thrift (_Armeria maritima_) and the various species of -Sea Lavender (genus _Statice_). They are characterised by a tubular -membranous calyx, persistent and often coloured, a regular corolla of -five petals united at their bases, five stamens opposite the petals and -attached at the base of the ovary, and a free one-celled and one-seeded -ovary. The well-known Sea Pink, with its compact head of rose-coloured -flowers, in bloom throughout the spring and summer, and linear -one-veined leaves, may be seen on most of our coasts, as well as on high -ground in inland districts. The Sea Lavender, of which there are four -British species, have their flowers arranged in spikes. The commonest -species (_Statice limonium_) may be found principally on muddy shores. -Its leaves are narrow and one-ribbed, and the bluish-purple flowers -arranged in short dense spikes, the flower stalk being branched only -above the middle. One variety of it has its flowers in a loose pyramidal -cluster, while another bears its spikes in a compact level-topped corymb -with short firm branches. Another species (_S. bahusiensis_) is -characterised by long spikes of distant flowers, the stalk being -branched from near the base. The Upright Sea Lavender (_S. binervosa_) -of rocky shores has the stalk branched from the middle, with, usually, -nearly all the branches flowering, though there are varieties in which -the flowers are differently arranged. The Matted Sea Lavender (_S. -caspia_) grows in salt marshes on the east coast of England. Its flower -stalk is branched from the base, but the lower branches are barren and -tangled, while the upper bear small crowded lilac flowers. The leaves of -the last two species are spatulate in form. - -The Bittersweet or Woody Nightshade (_Solanum Dulcamara_) of the order -_Solanaceæ_ is common in hedgerows and waste places almost everywhere, -but a variety of it (_marinum_) has its habitat along the coast. It may -be distinguished from the normal form by its prostrate branched and -non-climbing stem, and by its fleshy leaves. The latter are all cordate, -while in the normal the upper leaves are auricular. The order to which -_Solanum_ belongs is characterised by a regular five-cleft calyx and -corolla, four or five stamens attached to the corolla, and a superior -two-celled ovary. The flowers are in axillary cymes, and the fruit is a -berry. - -_Convolvulaceæ_ is represented on sandy shores by the Sea-side Bindweed -(_Convolvulus Soldanella_), a small species, with pinkish purple -flowers, the prostrate stem of which rarely measures more than a foot in -length. The plants of this order are generally climbing plants with -alternate leaves and regular showy flowers. The calyx is composed of -five sepals, the corolla of four or five lobes, and the stamens are -attached to the corolla. The ovary is superior, two- or four-celled, and -the fruit a capsule. The above species may be recognised by its reniform -leaves (sagittate in the others), which are also fleshy. - -To the order _Gentianaceæ_ belong the Centaury (_Erythræa_), three out -of the four British species of which grow on sandy shores. In the -flowers of this order the calyx has from four to ten lobes; the stamens -also number four to ten, and are alternate with the lobes of the -corolla. The ovary is one- or two-celled, and the fruit is a berry with -many seeds. The leaves are usually opposite and entire, and the flowers -are generally showy, regular, and solitary. _Erythræa_ has a -funnel-shaped corolla, five stamens, and two stigmas, on a deciduous -style; and in all our species the flower is rose-coloured. The Dwarf -Centaury (_E. pulchella_), which is common on some sandy shores, is much -smaller than the species that thrives in pastures, being only two or -three inches in height. Its stem is also more freely branched, and its -flowers are axillary and terminal. The Tufted Centaury (_E. littoralis_) -and the Broad-leaved Centaury (_E. latifolia_) occur in similar -situations, but are comparatively rare. They are both small species, the -former with an unbranched stem, narrow leaves, and corymbose -inflorescence; and the latter with branched stem, broad elliptical -leaves, and flowers in dense forked tufts. - - [Illustration: FIG. 298.--THE DWARF CENTAURY] - -The extensive order _Compositæ_ contains comparatively few sea-side -plants, and, in dealing with these, we pass to another division of the -monopetalous flowers, in which the ovary is inferior and the stamens are -on the corolla. The order includes those herbaceous plants in which -sessile flowers are collected together into compound heads (_capitula_) -surrounded by a whorl of bracts. The corolla is either tubular or -strap-shaped (_ligulate_), the stamens four or five in number, and the -fruit one-seeded, usually crowned with the limb of the calyx in the form -of a scaly feathery or hairy pappus. - -The Little Lettuce (_Lactuca saligna_) is found in chalky pastures near -the east and south-east coasts, growing to a height of about a foot, and -bearing heads of yellow flowers in July and August. All the flowers are -ligulate and perfect, the pappus is composed of silvery hairs, and the -fruit is compressed and beaked, the beak being twice as long as the -fruit. The leaves are smooth, linear, and sagittate, terminating in a -sharp point. The Sea-side Cotton Weed (_Diotis maritima_) is -occasionally met with on sandy shores, and may be recognised by its -dense coating of downy hair, its sessile obtuse leaves, and heads of -yellow flowers forming a corymb. The heads are discoid, and the fruit -has no pappus. The Sea Wormwood (_Artemisia maritima_) is a common -sea-shore composite, bearing drooping heads of reddish-white flowers in -August. This is another of the downy species, its pinnatifid leaves -having quite a woolly appearance. The capitulum contains but few -flowers, all of which are perfect; and the fruit has no pappus. A -variety of this plant is sometimes seen, with dense erect capitula. The -Sea Aster or Michaelmas Daisy (_Aster tripolium_) of salt marshes may be -known by the yellow discs and purple rays of its flower heads, which are -arranged in a corymb. The florets of the ray form a single row, and the -fruit has a hairy pappus. The leaves of this plant are spatulate and -fleshy. A variety occurs in which the purple florets of the ray are -absent. The Golden Samphire (_Inula crithmoides_) is a very local -sea-side plant, being found principally on the south-west coast. Its -leafy stems grow to a height of a foot or more, and bear yellow heads of -flowers that radiate in all directions. The leaves are linear, acute, -and fleshy, and the bracts are linear and imbricated. Our last example -of the sea-side composites is the Sea-side Corn Feverfew or Scentless -Mayweed, which is a variety of _Matricaria inodora_ of waste places. The -leaves are sessile and pinnatifid, with very narrow segments, and the -white flowers grow in solitary heads. The maritime variety differs from -the normal form in having fleshy leaves. - -We next deal with another very extensive order (the _Umbelliferæ_), -which, however, has only three or four representatives on the shore, and -these introduce us to the last great division of the flowering plants, -namely, the _Polypetalous Dicotyledons_, in which the petals are not -united. Of these we shall first deal with that subdivision in which the -stamens are attached at the side of or upon the ovary. - -The most obvious characteristic of the _Umbelliferæ_ is that implied in -the name--the arrangement of the flowers in that form of inflorescence, -called the umbel, in which the pedicels all branch from one point in the -main stalk, and are such that the flowers are all approximately on a -level. The flowers are mostly small and white, with five sepals (when -present), five petals, and five stamens. The inferior ovary is -two-celled, bearing two styles; and the fruit separates into two dry -one-seeded carpels that are ribbed longitudinally. - -Our first example of this group is the Sea Carrot, a variety of the Wild -Carrot (_Daucus carota_). In the ordinary form, which is so common in -fields, the leaflets are pinnatifid, with acute segments; and the -central flowers of each umbel are purple, while the outer ones are -white. The umbel, when in fruit, is concave above. The maritime variety -differs from this in having fleshy leaves, and the umbel convex above -when in fruit. The Sea Samphire (_Crithmum maritimum_) grows on the -rocks close to the sea, and thrives well where there is hardly a -vestige of soil. It usually grows to a height of seven or eight inches, -bearing greenish-white flowers surrounded by a whorl of very narrow -leaves. The other leaves are glaucous and bi-ternate, the leaflets being -narrow, fleshy, and tapering towards both ends. On cliffs near the sea, -especially in chalky districts, we meet with the Fennel, with its -finely-divided leaves, split up into numerous capillary leaflets, and -its small yellow flowers without bracts. It may be distinguished from -other closely-allied plants by the form of the fruit, which is flattened -at the sides. It is grown in some parts for use as a potherb, and an -aromatic oil is also obtained from the seeds. The plant grows to a -height of four or five feet, but there is a smaller variety known as the -Sweet Fennel, and distinguished by the stem being compressed at the -base. Our next example of the _Umbelliferæ_ is the Sea Holly (_Eryngium -maritimum_), easily distinguished from the other umbellifers by its -spiny glaucous leaves, and the thistle-like heads of blue flowers -surrounded by a whorl of spiny bracts. Its fleshy creeping roots were -formerly gathered largely for the purpose of converting them into the -once-prized 'candied eryngo root,' which is still prepared in a few of -the fishing villages of our coast. The lower leaves of this plant are -spinous and very glaucous, and the upper ones palmate. The venation is -particularly strong and durable, so that the leaves and flowers are used -largely by the sea-side cottagers in the construction of skeleton -bouquets and wreaths. Another plant of the same genus--The Field Eryngo -(_E. campestre_)--is occasionally seen on sandy shores. It differs from -the last in having ternate radical leaves with pinnatifid lobes, and the -upper leaves, bi-pinnatifid. Our last example of the sea-side -umbellifers is the Wild Celery (_Apium graveolens_) of salt marshes and -ditches. This is the plant from which our highly-valued garden celery -has been produced, and it is remarkable that this sweet crisp and -wholesome vegetable has been derived from a wild plant of coarse taste -and odour, the acrid sap of which is highly irritating if not dangerous. -The plant may be known by its furrowed stem, and ternate leaves, the -leaflets of the lower leaves being round and lobed, while those of the -upper ones are notched. The umbels are sessile or nearly so, the flowers -have no calyx, and the fruit has five prominent ridges. - - [Illustration: FIG. 299.--THE SEA SAMPHIRE] - -On the sandy shores of the south-western counties we may meet with the -very local Four-leaved Allseed (_Polycarpon tetraphyllum_) of the order -_Illecebraceæ_. It is a small plant, only four or five inches in height, -with the lower leaves in whorls of four and the upper ones in opposite -pairs. The flowers are minute, and are disposed in small dense clusters. - -Another rare species is the shrub known as the English Tamarisk -(_Tamarix anglica_), which is our only representative of the order -_Tamariscaceæ_. There is some doubt, however, whether even this is -indigenous to Britain, though it occurs in a wild state on the coast. It -is a very twiggy shrub growing from six to ten feet in height, with -minute scale-like, acute leaves, and slender spikes of small -pinkish-white flowers. - -We now pass to the large order of Leguminous plants, characterised by -their stipuled leaves, and irregular papilionaceous flowers. The latter -usually have five united sepals, five petals forming an irregular, -butterfly-like corolla, ten stamens, and a superior ovary that develops -into a pod. - -Of these the Starry-headed Trefoil (_Trifolium stellatum_) is very -partial to the sea shore, though it is sometimes found some distance -inland. The genus to which it belongs is so called on account of its -trifoliate leaves which are characteristic of the clovers, trefoils, and -vetches, and which have stipules adhering to the petioles. The species -under notice receives its name from the star-like arrangement of the -long teeth of the hairy calyx. The stem of the plant is procumbent, -usually about six or eight inches long, with cylindrical and terminal -heads of yellowish-grey flowers. - -The Rough-podded Yellow Vetch (_Vicia lutea_) is somewhat rare, and -occurs principally on very rocky coasts. In common with the other -vetches it has pinnate, tendrilled leaves, without a terminal leaflet, -one stamen free and the rest united into a bundle, and a long, slender, -hairy style. Its stem is tufted and prostrate, averaging about a foot in -length, the leaflets long and narrow, and the yellow flowers sessile and -solitary. The teeth of the calyx are unequal, and the pods hairy and -curved. - - [Illustration: FIG. 300.--THE SEA-SIDE EVERLASTING PEA] - -The Sea-Side Everlasting Pea (_Lathyrus maritimus_) is a much commoner -plant of the coast, and may be readily recognised by its general -resemblance to the garden sweet-pea. The genus to which it belongs is -closely allied to the vetches, but may be distinguished by the style, -which is flattened below the stigma, hairy on the inner or upper side, -but quite smooth on the outer side. The sea-side species has an angled -(but not winged) stem, from one to three feet long, compound tendrilled -leaves with many oval leaflets, and large oval or cordate stipules. Its -purple flowers are in bloom during July and August. A variety of this -plant (_acutifolius_), with a slender straggling stem and narrow acute -leaflets, occurs on some parts of the Scottish coast. - - [Illustration: FIG. 301.--THE SEA STORK'S-BILL] - -The _Geraniaceæ_ is represented at the sea-side by the Sea Stork's-bill -(_Erodium maritimum_), which, however, is by no means a very common -flower. Its relationship to the other stork's-bills and the -crane's-bills may be readily proved by the five persistent sepals, five -distinct clawed petals, the five to ten stamens attached _under_ the -ovary (for we have now reached that division of the polypetalous exogens -distinguished by this mode of insertion of the stamens), and the five -carpels surrounding a long beak resembling that of the stork and the -crane. The plant may sometimes be seen on sandy shores, averaging a foot -in height, though very variable in this respect, and displaying its -pretty pink flowers during the whole of the summer. The principal -features by which it is to be distinguished from the two other British -plants of the same species are its ovate or cordate leaves with very -short petioles, and the presence of only one or two flowers on each -peduncle. - -Passing now to the Sea Mallow (_Lavatera arborea_), we are dealing with -another rather rare plant, of the order _Malvaceæ_, sometimes met with -on rocky coasts, chiefly, it appears, on the north coast of Cornwall and -Devon. This is a very shrubby plant, as its specific name implies, and -it is sometimes popularly known as the Tree Mallow on that account. It -has a very woody stem, growing to a height of four or five feet, and -bearing seven-pointed, downy leaves, and solitary, axillary, purple -flowers. As in the other mallows, the flowers have five petals, which -are curiously twisted when in the bud, five sepals, a large number of -stamens united into a tube, and an ovary of many cells, but it may be -distinguished from the other species of the order by its three-lobed -bracts. The plant is found principally in wild, uncultivated spots, but -is commonly grown as a garden plant by the cottagers of villages in the -south-west, and under cultivation it frequently grows to a height of -nine or ten feet, with a tree-like stem three or four inches in -thickness; and it produces such a quantity of fibre that its cultivation -for manufacturing purposes has been suggested. - -We now come to another of the very extensive orders, at least as far as -British plants are concerned, although it contains only a few sea-side -species. We refer to the _Caryophyllaceæ_, containing the pinks, -campions, catchflies, chickweeds, &c. The chief features of the order -are jointed, herbaceous stems, opposite leaves, and regular white or red -flowers with four or five sepals and petals, eight or ten stamens, and a -capsular fruit opening at the top with teeth. - -One of the commonest species we have to consider is the Sea Campion -(_Silene maritima_), common on nearly all coasts, and often growing in -small crevices of the bare rocks quite within the reach of the spray of -storm-waves. In common with the other members of its genus it is -characterised by a tubular calyx of united sepals, ten stamens, and a -three-celled capsule opening at the top with six teeth; but it may be -known at once by its small size, being only a few inches in height, and -its solitary flowers with calyx much inflated and the corolla only -shortly cleft. - -The Sea Sand Wort (_Spergularia marina_) is another common plant of the -coast, recognised by its slender, creeping stems; linear, stipuled, -fleshy leaves, convex below and blunt at the apex; and its pinkish-white -flowers. The Sea Purslane (_Honckenya peploides_), belonging to the same -order, is also a creeping plant, with ovate, acute fleshy leaves, -flowering from May to August. It is the only British plant of its genus, -and may be distinguished from others by the absence of stipules, -distinct sepals, petals entire, ten stamens, and from three to five -styles. The flowers are white, solitary, and sessile. The one remaining -species of the sea-side _Caryophyllaceæ_ is the Sea Pearl Wort (_Sagina -maritima_). This plant is closely allied to the last, being a creeper -with exstipulate leaves and distinct sepals, but its flowers are reddish -white, on erect peduncles, with very small petals. The leaves, too, are -linear, fleshy, and obtuse. There are three distinct varieties of this -plant, two of which have erect stems with short internodes, while the -third is procumbent with long internodes; and in all three the capsules -are shorter than the sepals. - - [Illustration: FIG. 302.--THE SEA CAMPION] - -A variety of the Common Milk Wort (_Polygala vulgaris_)--order -_Polygalaceæ_--is moderately common on sandy shores. The ordinary form -of the species, which is so common on heaths, is a small plant with a -woody stem, small ovate leaves crowded below, and opposite lanceolate -leaves above. The flowers are irregular with five persistent sepals, two -larger than the others; three to five petals, the lowest keeled, and all -united to the tube formed by the eight stamens, which are divided above -into two bundles; and the fruit is a flat capsule with two one-seeded -cells. The flowers are very variable in colour, being white, pink, -lilac, or blue; and the seeds are downy. The sea-side variety -(_oxyptera_) has smaller flowers than the normal form, and the wings of -the calyx are narrower. - -One species of Pansy (_Viola Curtisii_) is occasionally to be met with -on sandy shores, and may be at once recognised as one of the _Violaceæ_ -by its irregular spurred corolla, its five persistent sepals, and the -three-parted, one-celled ovary. The flowers are variable in colour and -size, the prevailing tints being blue and yellow, and the diameter of -the corolla occasionally reaching to one inch. It has a creeping woody -rootstock, and a rough angular stem; and the petals are generally but -little longer than the sepals. - - [Illustration: FIG. 303.--THE SEA PEARL WORT] - - [Illustration: FIG. 304.--THE SHRUBBY MIGNONETTE] - -The Shrubby Mignonette (_Reseda suffruticulosa_), of the order -_Resedaceæ_, is a common sea-side plant that grows to a height of one or -two feet on sandy shores, bearing spikes of white flowers in July and -August. The order is characterised by alternate exstipulate leaves, -persistent calyx with four or five sepals, corolla of from four to seven -petals, many stamens, and a three-lobed, one-celled ovary. The sea-side -species is very much like the wild mignonette so common in chalky -districts, but differs in having all its leaves pinnate, waved, and -glaucous, with linear segments; and in having five _equal_ sepals and -petals. In a variety of the species, however, the sepals and petals are -six in number. - -The Crucifers are fairly well represented by coast plants, there being -several maritime species of the order. The _Cruciferæ_ are named from -the nature of the corolla, the limbs of the four petals of which are -arranged so as to resemble the Maltese cross. The flowers have also four -sepals, six stamens, two of which are shorter than the other four, and -the fruit takes the form of a two-celled pod or pouch which opens by the -separation of its two valves from the central partition. - - [Illustration: FIG. 305.--THE WILD CABBAGE] - - [Illustration: FIG. 306.--THE ISLE OF MAN CABBAGE] - -Our first example is the Wild Cabbage (_Brassica oleracea_), which, -although so unlike the cabbage of our gardens, is really the parent of -all the cultivated varieties, including the cauliflower, broccoli, -Brussels sprouts, &c. It is a biennial plant, with fleshy lobed wavy -leaves that are covered with bluish bloom, and a fleshy cylindrical -root. It grows erect to a height of one or two feet, bearing yellow -flowers during the summer months. An allied species (_B. monensis_), -with a prostrate stem and deeply-divided leaves, occurs locally on the -sandy shores of the Isle of Man. - -Two species of Stock (_Matthiola_) are to be found on the coast, both -being characterised by purple flowers. The Great Sea Stock (_M. -sinuata_) is a rare plant growing on the shores of Wales and Cornwall, -and may be known by its herbaceous stem and narrow downy leaves; and the -other species--the Hoary Shrubby Stock (_M. incana_)--is also a rare -plant, found principally on the cliffs of the Isle of Wight, and is the -parent of the Brompton Stocks of our gardens. The latter has a branched -woody stem and narrow leaves. Both species grow to a height of about -eighteen inches, and the latter flowers in May and June, while the -former is in bloom during the hottest summer months. - -The Hare's-ear Treacle Mustard (_Erysimum orientale_) is a rare -crucifer, frequenting the cliffs of the southern and eastern counties. -It grows to a height of one to two feet, and bears its white flowers -about midsummer. It has glaucous leaves, and the fruit-pods are -quadrangular in form. - - [Illustration: FIG. 307.--THE GREAT SEA STOCK] - - [Illustration: FIG. 308.--THE HOARY SHRUBBY STOCK] - -The Common Scurvy Grass (_Cochlearia officinalis_) is abundant on many -shores, and its fleshy leaves, once highly valued as an antiscorbutic, -are still used for salad by the cottagers near the sea. It generally -grows to a height of six or seven inches, and displays its white flowers -during late spring and early summer. The root-leaves are cordate in -form, and the upper ones are sessile and angled, half embracing the -stem. The fruit is a rounded pouch. A variety (_danica_) with stalked, -deltoid leaves and an oval veiny pod, is _plentiful_ in some places. - - [Illustration: FIG. 309.--THE SCURVY GRASS] - - [Illustration: FIG. 310.--THE SEA RADISH] - -On some coasts we find the Sweet Alyssum (_Koniga maritima_)--a -naturalised plant with procumbent stem, narrow lanceolate, acute -leaves, and white flowers. It may be recognised by its compressed, -pointed pouch with one-seeded cells. This species flowers towards the -end of the summer. - -The Sea Radish (_Raphanus maritimus_) is a much larger plant, growing -three or four feet in height. In common with the Wild Radish of our -corn-fields, it has a tapering pod divided into one-seeded joints, but -it may be distinguished from the latter by its superior height and the -deeply-divided radical leaves. Its flowers are always yellow, while in -the field species they may be either yellow or white; and the style is -also shorter, being about the same length as the last joint of the pod. - -On sandy shores the Sea Rocket (_Cakile maritima_) is commonly seen, and -is readily distinguished by its zigzag branches, deeply-lobed, smooth, -fleshy leaves of a glaucous colour, and its succulent pod, which is -divided into two one-seeded cells by a horizontal partition. It grows -from one to two feet high, and bears pretty lilac flowers about -midsummer. - - [Illustration: FIG. 311.--THE SEA ROCKET] - -Our last example of the crucifers is the Sea Kale (_Crambe maritima_), a -hardy perennial, commonly seen growing among the sand and shingle of the -shore, which is the parent of the sea kale now so commonly cultivated in -our market gardens. It may be readily recognised by the fine glaucous -bloom of its stem, and its broad wavy toothed leaves of a glaucous grey -colour. It grows to a height of about eighteen inches, and bears white -flowers in June. The fruit is a two-jointed pouch, the upper being -rounded and one-seeded, while the lower is stalk-like and barren. This -plant is particularly common in the south-west of England, where the -leaves are sometimes blanched for food by burying them in the sand. - -One of the most striking plants of the coast is the Yellow Horned Poppy -(_Glaucium luteum_) of the order _Papaveraceæ_, which contains the -well-known poppies of corn-fields. The general characteristics of the -order are two deciduous sepals, four petals, many stamens inserted below -the ovary, and the ovary one-celled with membranous divisions. The -plants of this species usually contain a milky juice, have alternate -leaves without stipules, and the flowers, which are regular, generally -nod when in bud. The Horned Poppy is a very conspicuous plant, usually -growing quite alone on some inaccessible portion of the cliff, or among -the pebbles or shingle not far from high-water mark. Its stem is -glaucous and branched, and the large waved and deeply-cut leaves, which -clasp the stem, are also of a glaucous hue. The flowers are rendered -conspicuous by their large yellow petals, which, however, last only for -a day, and are succeeded by the hornlike seed-pods that sometimes reach -a foot in length. - - [Illustration: FIG. 312.--THE SEA KALE] - -We will conclude our list of sea-side flowers by a brief mention of the -Lesser Meadow Rue (_Thalictrum minus_), a variety of which (_maritimum_) -grows on sandy shores. The Meadow Rue belongs to the _Ranunculaceæ_, as -may be seen from the fruit of several distinct carpels, each containing -a single seed, the corolla of distinct petals, and the numerous stamens -inserted below the carpels. The normal form of the Lesser Meadow Rue, -which grows freely in some chalky pastures and thickets, has leaves -three or four times pinnate, and lax panicles of drooping flowers -without any petals. The sea-side variety differs from this in having the -stem leafless at the base, and the panicles leafless and broad. The -flowers are greenish white, and bloom in July and August. - - [Illustration: FIG. 313.--THE HORNED POPPY] - -To assist the reader in the identification of sea-side flowers we append -a list of the orders to which they belong, together with the principal -distinguishing characteristics of each. - - - - - SYNOPSIS OF THE NATURAL ORDERS - WHICH CONTAIN OUR PRINCIPAL - SEA-SIDE FLOWERING PLANTS - - - I. MONOCOTYLEDONS - - A. GLUMIFERÆ - - FLOWERS WITHOUT A PERIANTH, ENCLOSED IN GLUMES - - =1. Gramineæ=--Grassy plants with hollow stems enclosed in split - sheaths. Flowers generally bisexual with (usually) three - stamens. - - =2. Cyperaceæ=--Grassy plants with solid stems and entire sheaths. - Flowers arranged in spikelets, unisexual or bisexual, with - from one to three stamens. - - - B. PETALOIDÆ - - PERIANTH PETALOID - - =3. Juncaceæ=--Rushes, with narrow leaves and small brown flowers. - Perianth 6-partite, with scarious segments. Stamens - usually 6; ovary superior; fruit a 3-valved capsule. - - =4. Naiadaceæ=--Aquatic herbs with inconspicuous, unisexual or - bisexual flowers. Perianth absent or scale-like. Stamens - as many as the segments of the perianth. Fruit of from one - to four carpels--superior. - - =5. Alismaceæ=--Aquatic plants with radical net-veined leaves, and - (generally) conspicuous, white, bisexual flowers. Perianth - 6-partite. Stamens 6. Fruit of many carpels--superior. - - =6. Liliaceæ=--Herbs with narrow leaves and showy, bisexual - flowers. Perianth 6-partite. Stamens 6. Ovary superior, - 3-celled. Fruit a berry or capsule. - - II. DICOTYLEDONS - - A. CALYX, OR COROLLA, OR BOTH ABSENT - - =7. Euphorbiaceæ=--Herbs with entire leaves and (generally) a milky - juice. Flowers small, unisexual, dioecious (male and - female flowers on separate plants), sometimes enclosed in - calyx-like bracts. Perianth 3- or 4-partite or absent. - Stamens one or more. Ovary inferior. Fruit separating - into carpels elastically. - - =8. Eleagnaceæ=--Shrub with silvery scales, alternate, entire - leaves, and small, unisexual flowers--the staminate - flowers in catkins. Sepals of male flowers 3 or 4. Stamens - 4 to 8. Ovary superior. Fruit indehiscent (not splitting). - - =9. Polygonaceæ=--Herbs with sheathing stipules, alternate leaves, - and small (generally) bisexual flowers. Stamens 5 to 8. - Ovary superior. Fruit indehiscent. - - =10. Chenopodiaceæ=--Herbs with jointed stems and small unisexual or - bisexual flowers. Stamens usually 5, sometimes 1 or 2, - opposite the sepals. Ovary superior. Fruit indehiscent. - - B. PLANTS WITH BOTH CALYX AND COROLLA - - - _a._ COROLLA MONOPETALOUS - - 1. _Ovary Superior and Stamens generally on the Corolla_ - - =11. Plantaginaceæ=--Herbs with radical entire leaves, and spikes - of small, green flowers. Calyx 4-cleft. Corolla 4-lobed, - scarious. Stamens 4. Ovary 2- to 4-celled. Fruit - many-seeded. - - =12. Plumbaginaceæ=--Herbs with radical or alternate leaves, and - (generally) regular, blue flowers. Calyx tubular, - scarious. Corolla of 5 petals, united below. Stamens 5, - opposite the petals, attached below the ovary. Ovary - 1-celled and 1-seeded. - - =13. Primulaceæ=--Herbs with (generally) radical leaves and - conspicuous, regular flowers. Calyx 4- to 7-cleft. Corolla - 4- to 7-cleft. Stamens 4 to 7, generally opposite the - petals. Ovary 1-celled. Fruit a capsule with many seeds. - - =14. Solanaceæ=--Herbs with alternate leaves and axillary clusters - of regular flowers. Calyx 5-cleft. Corolla 5-cleft. - Stamens 4 or 5. Ovary 2-celled. Fruit a berry. - - =15. Convolvulaceæ=--Climbing herbs with alternate leaves and showy, - regular flowers. Sepals 5. Corolla 4- or 5-lobed. Stamens - 4 or 5. Ovary 2- to 4-celled. Fruit a capsule. - - =16. Gentianaceæ=--Herbs with opposite entire leaves and solitary - regular flowers. Calyx 4- to 10-lobed. Corolla 4- to - 10-lobed. Stamens 4 to 10, alternate with the lobes of the - corolla. Ovary 1- or 2-celled. Fruit a capsule. - - 2. _Ovary Inferior and Stamens on the Corolla_ - - =17. Compositæ=--Herbs with flowers (generally yellow or white) - collected into compact heads. Calyx absent or represented - by a pappus. Corolla tubular or ligulate. Stamens 4 or 5. - - _b._ COROLLA POLYPETALOUS - - 1. _Stamens Perigynous_ (_around the Ovary_), _or Epigynous_ - (_upon the Ovary_) - - =18. Umbelliferæ=--Herbs with (generally) compound leaves, and - small, white, umbelled flowers. Sepals (if present) 5. - Petals 5. Stamens 5. Ovary inferior. Fruit of two - adhering carpels. - - =19. Illecebraceæ=--Small herbs with sessile, entire leaves, and - small flowers. Sepals 4 or 5. Petals 4 or 5 or absent. - Stamens 1 to 5. Ovary superior. - - =20. Tamariscaceæ=--Shrub with small, scale-like leaves, and lateral - spikes of small regular flowers. Sepals 4 or 5. Petals 4 - or 5. Stamens 4 or more. - - =21. Leguminosæ=--Herbs or shrubs with alternate, stipuled, pinnate - or ternate leaves, sometimes tendrilled, and irregular - flowers. Sepals 4 or 5. Corolla of 5 petals, - papilionaceous (butterfly-like). Stamens usually 10. Ovary - superior. Fruit a pod. - - 2. _Stamens Hypogynous_ (_attached below the Ovary_) - - =22. Geraniaceæ=--Herbs with stipuled, lobed leaves, and showy - regular flowers. Sepals 5. Petals 5. Stamens 5 or 10. - Fruit of 5 carpels surrounding a long beak. - - =23. Malvaceæ=--Herbs with alternate, stipuled leaves, and axillary, - red, or purple flowers. Sepals 5. Petals 5, twisted in the - bud. Stamens numerous, united into a tube. Ovary of many - cells. - - =24. Caryophyllaceæ=--Herbs with (generally) jointed stems, opposite - leaves, and regular white or red flowers. Sepals 4 or 5. - Petals 4 or 5. Stamens 8 or 10. Fruit a 1-celled capsule - opening at the top with teeth. - - =25. Polygalaceæ=--Herbs with alternate, simple leaves (without - stipules), and irregular flowers. Sepals 5, the inner - petal-like. Petals 3 to 5, unequal. Stamens 8, in two - clusters. Fruit a 2-celled capsule. - - =26. Violaceæ=--Herbs with alternate, stipuled leaves and irregular - flowers. Sepals 5. Petals 5, unequal, the lower one - spurred. Stamens 5. Ovary 3-partite, but 1-celled. - - =27. Resedaceæ=--Herbs or shrubs with alternate, exstipulate leaves, - and spikes of irregular, green flowers. Sepals 4 or 5. - Petals 4 to 7, unequal. Stamens more than 10. Ovary - 3-lobed, and 1-celled. - - =28. Cruciferæ=--Herbs with alternate, exstipulate leaves, and - regular flowers. Sepals 4. Petals 4, cruciate. Stamens - 6--4 longer and 2 shorter. Ovary 1- or 2-celled. Fruit a - siliqua or a silicula. - - =29. Papaveraceæ=--Herbs with alternate, exstipulate leaves, a milky - juice, and regular, showy flowers. Sepals 2, deciduous. - Petals 4. Stamens numerous. Ovary 1-celled with membranous - partitions. - - =30. Ranunculaceæ=--Herbs with (generally) alternate leaves and - regular flowers. Sepals generally 5, distinct. Petals 5 or - more. Stamens numerous. Fruit of many, distinct carpels. - - - - - INDEX - - - Acalephæ, 134 - - Acanthias, 319 - - Acarina, 304 - - Aclis, 246 - - Acmæa, 240 - - Acorn Barnacles, 263 - - Actinia, 142 - - Actinoloba, 143 - - Actora, 300 - - Adamsia, 154 - - Adeorbis, 243 - - Ægirus, 235 - - Æolidæ, 235 - - Aëpus, 303 - - Agonus, 335 - - Aiptasia, 144 - - Alaria, 385 - - Alcyonium, 155 - - Algæ, 344, 347 - - -- reproduction, 351 - - Alismaceæ, 401, 423 - - Allseed, 413 - - Alopecurus, 397 - - Ambulacrum, 163 - - Ammodytes, 326 - - Ammophila, 396 - - Amoeba, 102 - - Amphibia, 307 - - Amphipoda, 267, 304 - - Anarrhichas, 334 - - Anatinidæ, 204, 255 - - Anemones, 127, 138 - - Angiosperms, 346, 348 - - Angler Fish, 336 - - Angling, 34 - - Anguilla, 324 - - Anguillidæ, 323 - - Angular Crab, 289 - - Annelida, 177 - - Anomia, 222 - - Anomura, 279 - - Antedon, 160 - - Anthea, 149 - - Anurida, 299 - - Apetalæ, 402 - - Aphaniptera, 305 - - Aphrodita, 179 - - Apium, 412 - - Aporrhais, 245 - - Aquarium, 51 - - -- aeration of, 61, 63 - - -- cement for, 54, 57 - - -- construction of, 53 - - -- fountain, 64 - - -- temporary, 52 - - -- weeds for, 61 - - Arachnoidea, 257, 293, 304 - - Araneidæ, 304 - - Arca, 216 - - Arcadæ, 216, 255 - - Arctopsis, 289 - - Arenicola, 178 - - Armeria, 408 - - Artemisia, 410 - - Arthropoda, 255 - - -- classification, 304 - - Asiphonida, 198, 216, 255 - - Asparagus, 402 - - Asperococcus, 383 - - Astarte, 212 - - Aster, 410 - - Asteroidea, 171 - - Atherina, 332 - - Atherinidæ, 332 - - Atriplex, 406 - - Aurelia, 135 - - Aviculidæ, 219, 255 - - - Badderlocks, 385 - - Baits, 39 - - Balanophyllia, 152 - - Balanus, 6, 263 - - Banded Cockle, 216 - - Barley Grasses, 395 - - Barnacles, 261 - - Bass, 338 - - Beach Fleas, 263 - - Beadlet, 142 - - Beard Grass, 397 - - Beet, 405 - - Bembidiidæ, 301 - - Bembidium, 302 - - Beroe, 137 - - Bittersweet, 409 - - Bledius, 304 - - Blennies, 332 - - Blenniidæ, 332 - - Blennius, 334 - - Blue Shark, 320 - - Bonnet Limpet, 240 - - Bopyrus, 267 - - Boring Pill-ball, 268 - - Boring Sponge, 124 - - Bottle-brush, 132 - - Brachelytra, 303 - - Brachiopods, 224 - - Brachyura, 271, 279, 285, 304 - - Branchiopoda, 265, 304 - - Brassica, 418 - - Bread-crumb Sponge, 123 - - Bristle-tails, 298 - - Brittle Starfish, 157, 159, 161 - - Broad-clawed Crab, 280 - - Brome Grasses, 395 - - Bromus, 395 - - Bryopsis, 354 - - Bryozoa, 188 - - Buccinidæ, 248, 255 - - Buccinum, 248 - - Bugs, 297 - - Bulla, 236 - - Bull-heads, 335 - - Bull Huss, 320 - - Bunodes, 150 - - Butter Gunnel, 334 - - Byssus, 43, 195 - - - Cabinets, 89 - - Cæcum, 245 - - Cakile, 420 - - Calamary, 252 - - Calcarea, 119 - - Calcareous Sponges, 119 - - Callianassa, 277 - - Calliblepharis, 367 - - Callionymus, 335 - - Callithamnion, 61, 358 - - Callophyllis, 365 - - Calpurna, 248 - - Calyptræa, 241 - - Calyptræidæ, 240, 255 - - Canary Grass, 396 - - Cancer, 292 - - Carangidæ, 338 - - Caranx, 338 - - Carapace, 272 - - Carchariidæ, 320 - - Carcharius, 320 - - Carcinus, 291 - - Cardiadæ, 214, 255 - - Cardium, 214 - - Carex, 398 - - Carrageen Moss, 61, 364 - - Caryophyllaceæ, 415, 425 - - Caryophyllia, 151 - - Catometopa, 286, 289 - - Cave-dweller, 147 - - Cell for live objects, 95 - - Cement for aquarium, 57 - - Centaury, 409 - - Centipedes, 305 - - Cephalophora, 191, 225, 255 - - Cephalopoda, 191, 250, 255 - - Ceramiaceæ, 358, 389 - - Ceramium, 61, 362 - - Cerati-solen, 207 - - Cerithiadæ, 245, 255 - - Cerithium, 245 - - Cetacea, 340 - - Chætopoda, 177 - - Chalina, 122 - - Chalk, 109 - - Chambered Mussel, 219 - - Channelled Wrack, 387 - - Charales, 343, 348 - - Chenopodiaceæ, 405, 424 - - Chenopodium, 405 - - Chilognatha, 305 - - Chilopoda, 305 - - Chironomus, 301 - - Chiton, 237 - - Chitonidæ, 237, 255 - - Chlorophyll, 74 - - Chlorospermeæ, 350, 389 - - Chondria, 374 - - Chondrus, 61, 364 - - Chorda, 385 - - Chordaria, 381 - - Chordariaceæ, 380, 390 - - Chrysaora, 136 - - Chylocladia, 364 - - Cillenium, 303 - - Circe, 212 - - Cirripedia, 261, 304 - - Cladophora, 352 - - Cladostephus, 380 - - Cliffs, 2 - - Cliona, 124 - - Cloak Anemone, 154 - - Club-mosses, 345 - - Club Rush, 399 - - Clupea, 322 - - Clupeidæ, 322 - - Coast--general characters of, 1 - - Cochlearia, 419 - - Cockles, 214 - - Cod, 327 - - Codium, 353 - - Coelenterates, 127 - - Coelopa, 300 - - Coleoptera, 301, 305 - - Columella, 226 - - Common sponges, 119 - - Compositæ, 410, 425 - - Cone Shells, 248 - - Conidæ, 248, 255 - - Coniferæ, 347, 348 - - Confervaceæ, 352, 389 - - Convolvulaceæ, 409, 425 - - Convolvulus, 409 - - Copepoda, 264, 304 - - Corallina, 61, 369 - - Corallinaceæ, 369, 390 - - Corallines--preserving 87 - - Corals, 151 - - Corbula, 206 - - Cord Grass, 398 - - Cordylecladia, 366 - - Cornish Sucker, 330 - - Corrosive sublimate, 75 - - Corystes, 286 - - Cottidæ, 335 - - Cottus, 335 - - Cowries, 247 - - Crab-pots, 26 - - Crabs--as bait, 44 - - -- preserving, 81 - - Crambe, 420 - - Crangon, 278 - - Crenella, 219 - - Crinoidea, 171 - - Crithmum, 411 - - Cruciferæ, 417, 426 - - Crustacea, 257, 304 - - Crustaceans--preserving, 80 - - Cryptogams, 343, 347 - - Cryptonemiaceæ, 363, 389 - - Ctenophora, 137 - - Cup Coral, 151 - - Cup-and-saucer Limpet, 240 - - Cutleria, 382 - - Cuttlefishes, 191, 251, 253 - - Cycadeæ, 347, 348 - - Cyclometopa, 286, 291 - - Cyclostomata, 307, 308 - - Cydippe, 137 - - Cynodon, 396 - - Cyperaceæ, 398, 423 - - Cypræa, 248 - - Cypræidæ, 247, 255 - - Cyprina, 212 - - Cyprinidæ, 212, 255 - - Cystoclonium, 365 - - Cystoseira, 387 - - Cythere, 266 - - Cytheria, 211 - - Cyttidæ 338 - - - Dactylopteridæ, 335 - - Dahlia Wartlet, 143 - - Daisy Anemone, 146 - - Danica, 419 - - Dasya, 376 - - Daucus, 411 - - Dead Men's Fingers, 155 - - Decapoda (Decapods), 251, 255, 269, 271, 279, 304 - - Delesseria, 366, 368 - - Delphinidæ, 340 - - Demospongia, 119 - - Dendronotus, 235 - - Dentaliadæ, 238, 255 - - Desmarestia, 385 - - Devon Cup-coral, 151 - - Dibranchiata, 251, 255 - - Dicotyledons, 347, 403, 424 - - Dictyosiphon, 383 - - Dictyotaceæ, 382, 390 - - Dillisk, 365 - - Diotis, 410 - - Diptera, 299, 305 - - Dissecting microscope, 91 - - Dissecting trough, 98 - - Dissection, 91 - - Dog-fishes, 318 - - Dog Whelks, 248 - - Dog Winkles, 248 - - Dog's-tooth Grass, 396 - - Dolichopodidæ, 300 - - Dolphin, 340 - - Donax, 208 - - Doridæ, 235 - - Doto, 235 - - Dragonet, 335 - - Dredge, 26 - - Dreissina, 219 - - Dromia, 282 - - Dulse, 61, 365 - - Dumontia, 363 - - Dyschirius, 304 - - - Ear-shell, 242 - - Echinocyamus, 168 - - Echinoderms, 157 - - Echinoidea, 171 - - Echinus, 168 - - Ectocarpaceæ, 378, 390 - - Ectocarpus, 378 - - Edible Cockle, 214 - - Edible Crab, 292 - - Edible Mussel, 217 - - Edriophthalmata, 266, 304 - - Eel, 323 - - Elachista, 381 - - Elasmobranchii, 318 - - Eleagnaceæ, 403, 424 - - Eleocharis, 399 - - Elymus, 395 - - Elysia, 235 - - Emarginula, 242 - - Enteromorpha, 61, 355 - - Entomostraca, 266, 304 - - Equisetales, 345, 348 - - Erato, 248 - - Erodium, 414 - - Eryngium, 412 - - Eryngo, 412 - - Erysimum, 418 - - Erythræa, 409 - - Establishment of port, 17 - - Eulima, 246 - - Euphorbia, 403 - - Euphorbiaceæ, 403, 424 - - Euplexoptera, 305 - - Exogenæ, 402 - - - Father Lasher, 335 - - Feather Starfish, 159, 160 - - Ferns, 345 - - Fescue Grass, 396 - - Festuca, 396 - - Filicales, 345, 348 - - Fishes, 307 - - -- classification, 318 - - -- colour of, 313 - - -- distribution, 317 - - -- fins of, 311 - - -- gills, 312 - - -- preserving, 85 - - -- scales of, 309 - - -- skeleton, 314 - - -- tails, 315 - - Fishing, 34 - - Fishing Frog, 336 - - Fissurella, 241 - - Fissurellidæ, 241, 255 - - Five-fingered Starfish, 157 - - Flat-fishes, 324 - - Floating Crab, 289 - - Flounders, 325 - - Flowering Plants--classification, 423 - - Flowers--fertilisation, 393 - - -- preserving, 86 - - -- structure, 346 - - Flustra, 188 - - Flying Gurnards, 335 - - Foraminifera, 106 - - Formaldehyde, 73 - - Fox-tail Grass, 398 - - Fragacea, 142 - - Fucaceæ, 386, 390 - - Fucus, 386 - - Fungi, 344, 347 - - Furbelows, 384 - - Furcellaria, 364 - - Fusus, 249 - - - Gadiadæ, 327 - - Gadus, 327 - - Galeomma, 214 - - Gamopetalæ, 403 - - Gaper shell, 205 - - Gasteropoda, 232, 255 - - Gastrochæna, 203 - - Gastrochænidæ, 203, 255 - - Gastrosteidæ, 331 - - Gastrosteus, 331 - - Gebia, 276 - - Gelidiaceæ, 390 - - Gelidium, 367 - - Gem Pimplet, 150 - - Gentianaceæ, 409, 425 - - Geodephaga, 301 - - Gephyrea, 176 - - Geraniaceæ, 414, 425 - - Gibb's Crab, 289 - - Gigartina, 364 - - Glass-wort, 407 - - Glaucium, 420 - - Globigerina, 109 - - Globular Beroe, 137 - - Gloisiphonia, 364 - - Glumiferæ, 423 - - Glycerine, 73 - - Goadby's fluid, 73 - - Gobies, 334 - - Gobiidæ, 334 - - Gobioesocidæ, 330 - - Gobius, 334 - - Golden Samphire, 411 - - Gonoplax, 290 - - Goosefoot, 405 - - Gracilaria, 366 - - Gramineæ, 392, 423 - - Grantia, 120 - - Grass-wracks, 400 - - Green Laver, 61 - - Green Pea-urchin, 168 - - Grey Mullet, 332 - - Griffithsia, 61, 360 - - Ground bait, 49 - - Gurnards, 335 - - Gymnosperms, 346, 348 - - - Haddock, 327 - - Hake, 328 - - Halecium, 131 - - Halibut, 326 - - Halichondria, 123 - - Halidrys, 388 - - Haliotidæ, 242, 255 - - Haliotis, 242 - - Halurus, 361 - - Hapalidiaceæ, 390 - - Hare's Ear, 418 - - Heart Cockle, 212 - - Heart Urchin, 168 - - Helminthocladiæ, 389 - - Henslow's Crab, 293 - - Henware, 385 - - Hepaticæ, 344, 348 - - Hermit Crab, 44, 154, 280, 232 - - Herring, 322 - - Herring-bone Polype, 131 - - Hexactinellida, 119 - - Himanthalia, 387 - - Hippoglossus, 326 - - Hippophaë, 403 - - Hog-louse, 268 - - Holostomata, 236, 255 - - Holothuroidea, 169 - - Homarus, 274 - - Honckenya, 416 - - Honeyware, 385 - - Hook-nose, 335 - - Hooks--fishing, 37 - - Hordeum, 395 - - Horned Poppy, 420 - - Horse Limpet, 240 - - Horse Mackerel, 338 - - Horse Mussels, 218 - - Horsetails, 345 - - Hydrozoa, 130 - - Hymenoptera, 305 - - Hypnæa, 365 - - - Ianthina, 242 - - Illecebraceæ, 412, 425 - - Inachus, 289 - - Infusoria, 104, 112 - - Insecta (Insects), 257, 294, 305 - - Inula, 411 - - Iridæa, 364 - - Irish Moss, 61, 364 - - Isocardia, 212 - - Isopoda, 267, 304 - - Isotoma, 299 - - - Jania, 370 - - Jelly-fishes, 127, 134 - - John Dory, 338 - - Juncaceæ, 400, 423 - - Juncus, 400 - - - Keyhole Limpet, 241 - - Knappia, 397 - - Knot-grasses, 404 - - Knotted Wrack, 386 - - Koniga, 419 - - - Labial palpi, 197 - - Labridæ, 329 - - Lactuca, 410 - - Lacuna, 244 - - Lady Crab, 292 - - Lamellibranchiata (Lamellibranchs), 191, 192, 255 - - Laminaria, 384 - - Laminariaceæ, 384, 390 - - Lampreys, 308 - - Lathyrus, 413 - - Laurencia, 370 - - Laurenciaceæ, 370, 390 - - Lavatera, 415 - - Laver, 61, 354 - - Leathesia, 381 - - Leda, 217 - - Leguminosæ, 413, 425 - - Lemon Sole, 326 - - Lenses, 91 - - Lepadogaster, 330 - - Lepidoptera, 305 - - Lepturus, 395 - - Lesser Rue, 422 - - Leucosolenia, 121 - - Ligia, 268 - - Liliaceæ, 402, 423 - - Limnoria, 268 - - Limpets, 43, 238 - - Ling, 328 - - Lithodes, 282 - - Litosiphon, 383 - - Little Lettuce, 410 - - Littorina, 243 - - Littorinidæ, 244, 255 - - Liverworts, 344 - - Lobster pots, 26 - - Lobsters, 274 - preserving, 81 - - Loligo, 252 - - Lomentaria, 371 - - Long-armed Crab, 286 - - Lophius, 336 - - Lucinidæ, 213, 255 - - Lugworm, 39, 178 - - Lutraria, 209 - - Lycopodiales, 345, 348 - - - Machilis, 298 - - Mackerel, 337 - - Macrura, 271, 279, 304 - - Mactra, 209 - - Mactridæ, 209, 255 - - Maia, 289 - - Malacostraca, 266, 304 - - Malvaceæ, 415, 425 - - Mammals, 307, 339 - - Mantis Shrimps, 270 - - Marginella, 248 - - Marine aquarium, 51 - - Marsipobranchii, 308 - - Mat-grass, 396 - - Matricaria, 411 - - Matthiola, 418 - - Maugeria, 366 - - Meadow Grasses, 395 - - Meadow Rue, 421 - - Medusæ, 134 - - Medusoids, 133 - - Melanospermeæ, 350, 376, 290 - - Melobesia, 370 - - Merluccius, 328 - - Mesembryanthemum, 142 - - Mesenteries, 139 - - Mesogloia, 381 - - Methylated spirit, 72 - - Michaelmas Daisy, 410 - - Micralymma, 303 - - Milkwort, 416 - - Millepedes, 305 - - Modiola, 218 - - Molluscs, 190 - - -- bivalve, 192 - - -- classification, 255 - - Molva, 328 - - Monera, 110 - - Monocotyledons, 347, 391, 423 - - Montagu's Sucker, 331 - - Morone, 338 - - Moss Polyps, 188 - - Mosses, 344 - - Motella, 328 - - Mud-burrower, 277 - - Mugil, 332 - - Mugilidæ, 332 - - Mullidæ, 338 - - Mullus, 338 - - Murex, 249 - - Muricidæ, 249, 255 - - Murlins, 385 - - Musci, 344, 348 - - Muscineæ, 343, 344, 348 - - Museum, 88 - - Mussels, 42, 217 - - Mustelus, 320 - - Mya, 205 - - Myacidæ, 205, 255 - - Myrionema, 381 - - Myriopoda, 257, 305 - - Myriotrichia, 379 - - Mytilidæ, 217, 255 - - Mytilus, 217 - - - Naiadaceæ, 400, 423 - - Nassa, 249 - - Natica, 246 - - Naticidæ, 246, 255 - - Nautilidæ, 255 - - Needle-fish, 329 - - Nephrops, 275 - - Nereis, 284 - - Nerophis, 329 - - Nesæa, 268 - - Nets, Collecting, 23 - - Neuroptera, 305 - - Nitophyllum, 367 - - Noctiluca, 114 - - Norway Lobster, 275 - - Notched Limpets, 242 - - Nucleobranchiata, 232, 255 - - Nucula, 217 - - Nudibranchiata, 233, 255 - - Nummulites, 108 - - Nummulitic limestone, 110 - - Nurse Dog, 320 - - Nut Crabs, 286 - - - Obione, 405 - - Octopoda, 251, 255 - - Octopus, 251 - - Odonthalia, 375 - - Odostomia, 246 - - OEpophilus, 297 - - Oleasters, 403 - - Oligochæta, 177 - - Omar, 242 - - Oniscoda, 268 - - Opelet, 149 - - Operculum, 83, 227 - - Ophidiidæ, 326 - - Ophiuroidea, 171 - - Opisthobranchiata, 232, 255 - - Opossum Shrimps, 270 - - Oraches, 406 - - Orange-disked Anemone, 148 - - Orthoptera, 305 - - Osmerus, 321 - - Ostracoda, 265, 304 - - Ostrea, 221 - - Ostreidæ, 221, 255 - - Outdoor work, 21 - - Ovulum, 248 - - Oxyptera, 416 - - Oxyrhyncha, 286 - - Oxystomata, 286 - - Oysters, 221 - - - Padina, 382 - - Pagurus, 282, 285 - - Pallial line, 193 - - Pansy, 417 - - Papaveraceæ, 420, 426 - - Parasitic Anemone, 153 - - Patella, 239 - - Patellidæ, 255 - - Paternoster, 48 - - Pea Crabs, 289 - - Pea Urchin, 168 - - Peachia, 145 - - Pearl Oysters, 219 - - Pecten, 222 - - Pectunculus, 216 - - Pennant's Crab, 286 - - Pepper Dulse, 370 - - Pericardium, 196 - - Peristome, 226 - - Periwinkle, 62, 243 - - Petaloidæ, 423 - - Phalaris, 396 - - Phanerogams, 343, 346, 348 - - Phasianella, 243 - - Pheasant Shell, 243 - - Phleum, 397 - - Phocæna, 340 - - Pholadidæ, 199, 255 - - Pholadidea, 201 - - Pholas, 200 - - Phosphorescence, 18, 111 - - Phyllirhoidæ, 286 - - Phyllophora, 365 - - Piddocks, 200 - - Pilchard, 322 - - Pileopsis, 241 - - Pilota, 361 - - Pimplet, 150 - - Pinna, 221 - - Pinna Pea-crab, 290 - - Pinnotheres, 290 - - Pipe-fishes, 328 - - Plaice, 325 - - Plantaginaceæ, 408, 424 - - Plantago, 408 - - Plants, classification, 343, 347 - - Plate-gilled Molluscs, 191 - - Pleuronectes, 326 - - Pleuronectidæ, 324 - - Plocamium, 61, 366 - - Plumbaginaceæ, 408, 424 - - Poa, 396 - - Podded Sea-oak, 388 - - Podophthalmata, 266, 269, 304 - - Pogge, 335 - - Pollack, 327 - - Polybius, 293 - - Polycarpon, 413 - - Polychæta, 177 - - Polygala, 416 - - Polygalaceæ, 416, 426 - - Polygonaceæ, 404, 424 - - Polygonum, 404 - - Polypetalæ, 403 - - Polypogon, 397 - - Polysiphonia, 372 - - Polystomata, 115 - - Polyzoa, 188 - - Porcelain Crab, 280 - - Porcellana, 280 - - Porifera, 115 - - Porphyra, 355 - - Porpoise, 339 - - Portland Spurge, 403 - - Portunus, 292 - - Prawn, 44, 278 - - Preservation of marine objects, 71 - - Preservatives, 72 - - Prickly Cockle, 215 - - Prickly Salt-wort, 407 - - Primulaceæ, 424 - - Prosobranchiata, 232, 236 - - Protophyta, 343, 347 - - Protoplasm, 102 - - Protoplasta, 104, 110 - - Protozoa, 102 - - -- classification, 104 - - Psammobia, 208 - - Pteropoda, 230, 255 - - Pulmonifera, 255 - - Punctaria, 383 - - Puncturella, 241 - - Purple Spurge, 403 - - Purple-tipped Urchin, 168 - - Purpura, 249 - - Pycnogonum, 293 - - Pyramidellidæ, 246, 255 - - - Radiata, 140 - - Radiolaria, 104, 110 - - Ragworm, 40, 179 - - Raiidæ, 318 - - Ranunculaceæ, 422, 426 - - Raphanus, 420 - - Rays, 318 - - Red Mullets, 338 - - Red-specked Pimplet, 150 - - Reptilia, 307 - - Reseda, 417 - - Resedaceæ, 417, 426 - - Rhizocarpeæ, 345, 348 - - Rhizopods, 104 - - Rhizostoma, 136 - - Rhodomela, 372 - - Rhodomelaceæ, 372, 390 - - Rhodophyllis, 61 - - Rhodospermeæ, 350, 355, 389 - - Rhodymenia, 61, 365, 367 - - Rhodymeniaceæ, 365, 389 - - Rhombus, 326 - - Rhynchota, 297, 305 - - Rissoa, 244 - - Rock-fishes, 46 - - Rocklings, 328 - - Rock-pools, 6, 31 - - Rosy Anemone, 149 - - Rosy Feather Star, 160 - - Rotifers, 189 - - Rushes, 400 - - Rytiphlæa, 375 - - - Sabella, 184 - - Saddle Oyster, 222 - - Sagartia, 146 - - Sagina, 416 - - Salicornia, 407 - - Salmo, 321 - - Salmon, 321 - - Salmon Dace, 339 - - Salmonidæ, 321 - - Salsola, 407 - - Salt-wort, 407 - - Sand Eels, 326 - - Sandhoppers, 268 - - -- preserving, 81 - - Sand Smelts, 332 - - Sandworm, 178 - - Saxicava, 203 - - Scalaria, 244 - - Scallops, 222 - - Scentless Mayweed, 411 - - Schizopoda, 304 - - Schizymenia, 61, 364 - - Scirpus, 399 - - Scomber, 337 - - Scomberidæ, 337 - - Scorpionidæ, 304 - - Scorpion Spider-crab, 289 - - Scurvy Grass, 419 - - Scylliidæ, 319 - - Scyllium, 319 - - Sea angling, 34 - - -- Aster, 410 - - -- Buckthorn, 403 - - -- Bullheads, 335 - - -- Bream, 338 - - -- Campion, 415 - - -- Carrot, 411 - - -- Cat, 334 - - -- Cat's-tail Grass, 397 - - -- Cucumbers, 169 - - -- Devil, 336 - - -- Eggs, 165 - - -- -- preserving, 79 - - -- Girdles, 384 - - -- Grass, 61, 353, 400 - - -- Hard-grass, 395 - - -- Holly, 412 - - -- Kale, 420 - - -- Lavender, 409 - - -- Lemons, 233 - - -- Lettuce, 61 - - -- Loach, 328 - - -- Lyme-grass, 395 - - -- Mallow, 415 - - -- Mat, 188 - - -- Meadow Grass, 396 - - -- Mouse, 179 - - -- Pearl-wort, 416 - - -- Perch, 338 - - -- Pill-ball, 268 - - -- Pink, 408 - - -- Purslane, 406, 416 - - -- Radish, 420 - - -- Reed, 396 - - -- Rocket, 420 - - -- Rushes, 400 - - -- Salt, 17, 59 - - -- Saltness of, 17 - - -- Samphire, 411 - - -- Sand-wort, 415 - - -- Sedge, 398 - - -- Slater, 268 - - -- Slugs, 233 - - -- Snails, 331 - - -- Spurge, 403 - - -- Squirts, 188 - - -- Stock, 418 - - -- Stork's-bill, 414 - - -- Urchins, 157, 165 - - -- -- preserving, 79 - - -- -- shell of, 166 - - -- teeth, 167 - - -- water, artificial, 59 - - -- composition, 59 - - -- weeds, 343 - - -- -- classification, 389 - - -- -- preserving, 86 - - -- Wormwood, 410 - - Seaside Arrow Grass, 401 - - -- Bindweed, 409 - - -- Cottonweed, 410 - - -- Feverfew, 411 - - -- Grasses, 392 - - -- Knot Grass, 404 - - -- Plantain, 408 - - -- plants, 391 - - -- classification, 423 - - Section cutting, 96 - - Sedges, 398 - - Selaginellales, 345, 348 - - Sepia, 253 - - Sepiadæ, 253, 255 - - Sepiola, 252 - - Serpula, 185 - - Serranidæ, 338 - - Serrated Pill-ball, 268 - - Serrated Wrack, 386 - - Sertularia, 128 - - Sessile-eyed crustaceans, 266 - - Shanny, 333 - - Sharks, 318 - - Shells, preserving, 83 - - Shore Crab, 261, 291 - - -- Spider, 293 - - Shrimps, 278 - - -- preserving, 81 - - Shrubby Mignonette, 417 - - Silene, 415 - - Silicia, 122 - - Siphonaceæ, 358, 389 - - Siphonida, 198, 255 - - Siphonostomata, 236, 247, 255 - - Six-rayed Sponges, 119 - - Skates, 318 - - Slender-beaked Crab, 289 - - Sloke, 61, 355 - - Smelt, 321 - - Smooth Hound, 320 - - Snoods, 37 - - Solanaceæ, 409, 424 - - Solanum, 409 - - Soldier Crab, 280 - - Sole, 326 - - Solea, 326 - - Solecurtus, 207 - - Solenidæ, 255 - - Sparidæ, 338 - - Spartina, 397 - - Sparus, 338 - - Spergularia, 415 - - Sphacelaria, 279 - - Sphærococcoideæ, 366, 390 - - Sphærococcus, 366 - - Sphæroma, 268 - - Spicules, 118 - - Spider Crabs, 288 - - Spike Rush, 399 - - Spiny-finned fishes, 329 - - Spirorbis, 187 - - Sponges, 115 - - Spongiocarpeæ, 390 - - Spoon Worms, 176 - - Sporochnaceæ, 385, 390 - - Sporochnus, 385 - - Spotted Dogfish, 320 - - Spotted Hog-louse, 268 - - Spout Shell, 245 - - Sprats, 323 - - Spring-tails, 299 - - Spurges, 403 - - Spyridia, 363 - - Spyridiaceæ, 368, 389 - - Squamariæ, 390 - - Squid, 252 - - Squirt Worms, 176 - - Stalk-eyed crustaceans, 266, 269 - - Starfishes, 157 - - -- preserving, 79 - - Stargazers, 336 - - Statice, 408 - - Stenorhynchus, 289 - - Sticklebacks, 331 - - Stilophora, 383 - - Sting Bull, 337 - - Sting Fish, 335 - - Stock, 418 - - Stomopoda, 269, 304 - - Stone Crab, 280 - - Strawberry Beadlet, 142 - - Sucker Fishes, 330 - - Sweet Alyssum, 419 - - Swimming Crab, 293 - - Sycon, 121 - - Syngnathidæ, 328 - - Syngnathus, 329 - - - Tamariscaceæ, 413, 425 - - Tamarisk, 413 - - Tangles, 384 - - Tapes, 211 - - Tealia, 143 - - Tectibranchiata, 238, 255 - - Tectibranchs, 236 - - Teleostomi, 318, 320 - - Tellina, 208 - - Tellinidæ, 207, 255 - - Terebella, 181 - - Terebratulina, 225 - - Teredo, 201 - - Tetrabranchiata, 255 - - Thalictrum, 421 - - Thallophytes, 343, 344, 347 - - Trichoptera, 305 - - Thornback Crab, 289 - - Thracia, 204 - - Thrift, 408 - - Thuiaria, 132 - - Thysanoptera, 298, 305 - - Tides, 9 - - Tooth shells, 238 - - Top shells, 243 - - Trachinidæ, 336 - - Trachinus, 337 - - Treacle Mustard, 418 - - Tree Mallow, 415 - - Trefoil, 413 - - Trifolium, 413 - - Triglochin, 401 - - Triopa, 235 - - Tritonia, 235 - - Tritoniadæ, 235 - - Trivia, 248 - - Trochus, 243 - - Trumpet Anemone, 141 - - Tubularia, 132 - - Tunicates, 188 - - Turbellaria, 175 - - Turbinidæ, 243, 255 - - Turbot, 326 - - Turkey-feather Laver, 382 - - Turret shells, 245 - - Turritella, 244 - - Turritellidæ, 244, 255 - - Twin-bladder Wrack, 387 - - Two-spotted Sucker, 331 - - - Ulva, 61, 354 - - Ulvaceæ, 389, 354 - - Umbelliferæ, 411, 425 - - Umbilicus, 226 - - Umbo, 193 - - - Vascular cryptogams, 345 - - Velutina, 247 - - Velvet Crab, 292 - - Veneridæ, 210, 255 - - Venus, 210 - - Vermes, 172 - - Vertebrates, 306 - - Vetch, 413 - - Vicia, 413 - - Viola, 417 - - Violaceæ, 417, 426 - - Violet Fiddler, 292 - - - Water Ferns, 345 - - Weavers, 336 - - Wedge shells, 208 - - Whales, 340 - - Wheel animals, 189 - - Whelks, 248 - - Whirl Worms, 175 - - Whistle Fish, 328 - - Whitebait, 323 - - White Salmon, 339 - - Whiting, 327 - - Wild Cabbage, 418 - - Wild Celery, 412 - - Wing shells, 219 - - Wolf Fish, 334 - - Woody Nightshade, 409 - - Worms, 172 - - -- parasitic, 174 - - Worm Pipe-fish, 329 - - Wrangeliaceæ, 389 - - Wrasses, 329 - - - Xantho, 292 - - Xylophaga, 201 - - - Yellow Poppy, 420 - - - Zeus, 338 - - Zoantharia, 138 - - Zoarces, 333 - - Zonaria, 382 - - Zostera, 353, 400 - - - _Printed in England at_ THE BALLANTYNE PRESS - SPOTTISWOODE, BALLANTYNE & CO. LTD. - _Colchester, London & Eton_ - - -Transcriber's Note - -Minor inconsistencies in the punctuation of tables or captions are -silently corrected. - -Hyphenation is variable. Those compound words which are hyphenated only -on line breaks are rendered using modern usage. - -The word 'movable' appears only once as 'moveable' (165), which is -retained. - -The index entry for 'OEpophilus' is considered to be an error. All -instances of the word appear in the text as 'Æpophilus'. This has been -corrected and moved to the appropriate alphabetic position. - -The following corrections were made to obvious printer's errors, - -devel[e/o]ped (336); co[n/m]posed (364); - -The following list contains punctuation corrections made: - - p. 65 one of them[.] Added. - - p. 255 [Class] =LAMELLIBRANCHIATA= Added to match other - entries. - - p. 257 their tendencies[,/.] Corrected. - - p. 292 low-water[-]mark Unhyphenated elsewhere. - - p. 340 [(]_Cetacea_) Added. - - p. 390 in firm gelatine[,/.] Corrected. - - p. 403 by its stipuled leaves[.] Added. - - p. 434 Rhodospermeæ, 350, 355, 38[9] Added. - - - - - -End of the Project Gutenberg EBook of The Sea Shore, by William S. 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S. Furneaux: a Project Gutenberg eBook. @@ -311,47 +311,7 @@ hr.chap </style> </head> <body> - - -<pre> - -The Project Gutenberg EBook of The Sea Shore, by William S. Furneaux - -This eBook is for the use of anyone anywhere at no cost and with -almost no restrictions whatsoever. You may copy it, give it away or -re-use it under the terms of the Project Gutenberg License included -with this eBook or online at www.gutenberg.org - - -Title: The Sea Shore - -Author: William S. Furneaux - -Illustrator: Robert Lillie - -Release Date: June 18, 2013 [EBook #42978] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK THE SEA SHORE *** - - - - -Produced by KD Weeks, Chris Curnow and the Online -Distributed Proofreading Team at http://www.pgdp.net (This -file was produced from images generously made available -by The Internet Archive) - - - - - - -</pre> - +<div>*** START OF THE PROJECT GUTENBERG EBOOK 42978 ***</div> <div class="transnote"> @@ -19619,382 +19579,6 @@ devel[e/o]ped (336); co[n/m]posed (364).</p> </table> </div> - - - - - - -<pre> - - - - - -End of the Project Gutenberg EBook of The Sea Shore, by William S. 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You may copy it, give it away or -re-use it under the terms of the Project Gutenberg License included -with this eBook or online at www.gutenberg.org - - -Title: The Sea Shore - -Author: William S. Furneaux - -Illustrator: Robert Lillie - -Release Date: June 18, 2013 [EBook #42978] - -Language: English - -Character set encoding: ASCII - -*** START OF THIS PROJECT GUTENBERG EBOOK THE SEA SHORE *** - - - - -Produced by KD Weeks, Chris Curnow and the Online -Distributed Proofreading Team at http://www.pgdp.net (This -file was produced from images generously made available -by The Internet Archive) - - - - - -Transcriber's Note - -Due to limitations of this format, some typographical features are not -possible. Italic and bold text is represented in this text as _italic_ -and =bold=. The 'oe' ligature is rendered with 'oe' as separate -characters. Finally, the few superscripted characters are given in-line, -e.g. 'Ltd' or A1. - -The colored plates and other illustrations cannot be given here. The -approximate positions of each, including any caption text, is shown -as [Illustration: caption]. Those which are shown in the middle of -paragraphs are positioned at the nearest paragraph break. - -Please consult the detailed note at the end of this text for any -corrections made, and for any other observations about the text. - - - - - THE SEA SHORE - - - - - +--------------------------------------------------------------+ - | THE OUT-DOOR WORLD SERIES. | - | | - | THE OUT-DOOR WORLD; or, the Young Collector's Handbook. | - | By W. S. FURNEAUX. With 18 Plates (16 of which are | - | Coloured), and 549 Illustrations in the Text. Crown | - | 8vo, 6s. 6d. net. | - | | - | FIELD AND WOODLAND PLANTS. | - | By W. S. FURNEAUX. With 8 Plates in Colour, and numerous | - | other Illustrations by PATTEN WILSON, and from | - | Photographs. Crown 8vo, 6s. 6d. net. | - | | - | BRITISH BUTTERFLIES AND MOTHS. | - | By W. S. FURNEAUX. With 12 Coloured Plates and 241 | - | Illustrations in the Text. Crown 8vo, 6s. 6d. net. | - | | - | LIFE IN PONDS AND STREAMS. | - | By W. S. FURNEAUX. With 8 Coloured Plates and 331 | - | Illustrations in the Text. Crown 8vo, 6s. 6d. net. | - | | - | THE SEA SHORE. By W. S. FURNEAUX. | - | With 8 Coloured Plates and over 300 Illustrations in the | - | Text. Crown 8vo, 6s. 6d. net. | - | | - | BRITISH BIRDS. By W. H. HUDSON. | - | With a Chapter on Structure and Classification by FRANK E. | - | BEDDARD, F.R.S. With 16 Plates (8 of which are Coloured), | - | and 103 Illustrations in the Text. Crown 8vo, 6s. 6d. net. | - | | - | LONGMANS, GREEN & CO., 39 Paternoster Row, London, E.C.4 | - | New York, Toronto, Bombay, Calcutta and Madras. | - +--------------------------------------------------------------+ - - - [Illustration: Plate I, A ROCK-POOL] - - - - - THE SEA SHORE - - BY - - W. S. FURNEAUX - - AUTHOR OF - - 'THE OUTDOOR WORLD' 'BRITISH BUTTERFLIES AND MOTHS' - 'LIFE IN PONDS AND STREAMS' ETC. - - [Illustration] - - _WITH EIGHT PLATES IN COLOUR_ - _AND OVER THREE HUNDRED ILLUSTRATIONS IN THE TEXT_ - - _NEW IMPRESSION_ - - LONGMANS, GREEN AND CO. - 39 PATERNOSTER ROW, LONDON, E.C.4 - NEW YORK, TORONTO - BOMBAY, CALCUTTA AND MADRAS - - 1922 - - All rights reserved - - - - - +------------------------------------------------+ - | BIBLIOGRAPHICAL NOTE. | - | | - | _First published in September, 1903._ | - | | - | _Re-issue at Cheaper Price, July, 1911._ | - | | - | _New Impression, November, 1922._ | - | | - | | - | _Made in Great Britain_ | - | | - +------------------------------------------------+ - - - - - PREFACE - - -To sea-side naturalists it must be a matter of great surprise that of -the inhabitants of our coast towns and villages, and of the -pleasure-seekers that swarm on various parts of the coast during the -holiday season, so few take a real interest in the natural history of -the shore. The tide flows and ebbs and the restless waves incessantly -roll on the beach without arousing a thought as to the nature and cause -of their movements. The beach itself teems with peculiar forms of life -that are scarcely noticed except when they disturb the peace of the -resting visitor. The charming vegetation of the tranquil rock-pool -receives but a passing glance, and the little world of busy creatures -that people it are scarcely observed; while the wonderful forms of life -that inhabit the sheltered nooks of the rugged rocks between the -tide-marks are almost entirely unknown except to the comparatively few -students of Nature. So general is this apparent lack of interest in the -things of the shore that he who delights in the study of littoral life -and scenes but seldom meets with a kindred spirit while following his -pursuits, even though the crowded beach of a popular resort be situated -in the immediate neighbourhood of his hunting ground. The sea-side -cottager is too accustomed to the shore to suppose that he has anything -to learn concerning it, and this familiarity leads, if not to contempt, -most certainly to a disinclination to observe closely; and the visitor -from town often considers himself to be too much in need of his -hard-earned rest to undertake anything that may seem to require energy -of either mind or body. - -Let both, however, cast aside any predisposition to look upon the -naturalist's employment as arduous and toilsome, and make up their minds -to look enquiringly into the living world around them, and they will -soon find that they are led onward from the study of one object to -another, the employment becoming more and more fascinating as they -proceed. - -Our aim in writing the following pages is to encourage the observation -of the nature and life of the sea shore; to give such assistance to the -beginner as will show him where the most interesting objects are to be -found, and how he should set to work to obtain them. Practical hints are -also furnished to enable the reader to successfully establish and -maintain a salt-water aquarium for the observation of marine life at -home, and to preserve various marine objects for the purpose of forming -a study-collection of the common objects of the shore. - -To have given a detailed description of all such objects would have been -impossible in a work of this size, but a large number have been -described and figured, and the broad principles of the classification of -marine animals and plants have been given such prominence that, it is -hoped, even the younger readers will find but little difficulty in -determining the approximate positions, in the scale of life, of the -various living things that come within their reach. - -Of the many illustrations, which must necessarily greatly assist the -reader in understanding the structure of the selected types and in the -identification of the different species, a large number have been -prepared especially for this work. - - - - - CONTENTS - - - CHAPTER PAGE - - I. THE GENERAL CHARACTERISTICS OF THE SEA SHORE 1 - - II. THE SEA-SIDE NATURALIST 21 - - III. SEA ANGLING 34 - - IV. THE MARINE AQUARIUM 51 - - V. THE PRESERVATION OF MARINE OBJECTS 71 - - VI. EXAMINATION OF MARINE OBJECTS--DISSECTION 91 - - VII. THE PROTOZOA OF THE SEA SHORE 102 - - VIII. BRITISH SPONGES 115 - - IX. THE COELENTERATES--JELLY-FISHES, ANEMONES, AND - THEIR ALLIES 127 - - X. STARFISHES, SEA URCHINS, ETC. 157 - - XI. MARINE WORMS 172 - - XII. MARINE MOLLUSCS 190 - - XIII. MARINE ARTHROPODS 256 - - XIV. MARINE VERTEBRATES 306 - - XV. SEA WEEDS 343 - - XVI. THE FLOWERING PLANTS OF THE SEA-SIDE 391 - - INDEX 425 - - - - - - LIST OF COLOURED PLATES - - _Drawn by_ MR. ROBERT LILLIE _and reproduced by_ - MESSRS. ANDRE & SLEIGH, LTD., _Bushey_. - - - - PLATE I--_A ROCK-POOL_ _Frontispiece_ - - PLATE II--_SEA ANEMONES_ _To face p. 142_ - - 1, 2, 3. _Actinia mesembryanthemum._ - 4. _Caryophyllia Smithii._ - 5. _Tealia crassicornis._ - 6. _Sagartia bellis._ - 7. _Balanophyllia regia._ - 8. _Actinoloba dianthus._ - - PLATE III--_SEA ANEMONES_ _To face p. 150_ - - 1. _Sagartia troglodytes._ - 2. " _venusta._ - 3. _Actinia glauca._ - 4. " _chiococca._ - 5. _Bunodes Ballii._ - 6. " _gemmacea._ - 7. _Anthea cereus._ - 8. _Sagartia rosea._ - - PLATE IV--_ECHINODERMS_ _To face p. 168_ - - 1. _Asterias rubens._ - 2. _Goniaster equestris._ - 3. _Ophiothrix fragilis._ - 4. _Echinocardium cordatum._ - 5. _Echinus miliaris._ - 6. " _esculentus._ - - PLATE V--_MOLLUSCS_ _To face p. 222_ - - 1. _Solen ensis._ - 2. _Trivia europaea._ - 3. _Trochus umbilicatus._ - 4. " _magnus._ - 5. _Littorina littorea._ - 6. " _rudis._ - 7. _Haminea_ (_Bulla_) _hydatis_. - 8. _Tellina._ - 9. _Capulus_ (_Pileopsis_) _hungaricus_. - 10. _Chrysodomus_ (_Fusus_) _antiquus_. - 11. _Buccinum undatum._ - 12, 13. _Scalaria communis._ - 14. _Pecten opercularis._ - 15. " _varius._ - 16. " _maximus._ - - PLATE VI--_CRUSTACEA._ _To face p. 290_ - - 1. _Gonoplax angulata._ - 2. _Xantho florida._ - 3. _Portunus puber._ - 4. _Polybius Henslowii._ - 5. _Porcellana platycheles._ - - PLATE VII--_SEAWEEDS_ _To face p. 354_ - - 1. _Fucus nodosus._ - 2. _Nitophyllum laceratum._ - 3. _Codium tomentosum._ - 4. _Padina pavonia._ - 5. _Porphyra laciniata_ (_vulgaris_). - - PLATE VIII--_SEAWEEDS_ _To face p. 384_ - - 1. _Chorda filum._ - 2. _Fucus vesiculosus._ - 3. " _canaliculatus._ - 4. _Delesseria (_Maugeria_) sanguinea_. - 5. _Rhodymenia palmata._ - 6. _Chondrus crispus._ - 7. _Ulva lactuca._ - - - - - OTHER ILLUSTRATIONS - - FIG. PAGE - - 1. CHALK CLIFF 3 - - 2. WHITECLIFF (CHALK), DORSET 4 - - 3. PENLEE POINT, CORNWALL 5 - - 4. BALANUS SHELLS 6 - - 5. A CLUSTER OF MUSSELS 7 - - 6. BREAKERS 8 - - 7. ILLUSTRATING THE TIDE-PRODUCING INFLUENCE OF THE MOON 10 - - 8. ILLUSTRATING THE TIDES 11 - - 9. SPRING TIDES AT FULL MOON 12 - - 10. SPRING TIDES AT NEW MOON 12 - - 11. NEAP TIDES 13 - - 12. CHART SHOWING THE RELATIVE TIMES OF HIGH TIDE ON DIFFERENT - PARTS OF THE BRITISH COAST 16 - - 13. THE VASCULUM 22 - - 14. WIRE RING FOR NET 24 - - 15. NET FRAME WITH CURVED POINT 24 - - 16. RHOMBOIDAL FRAME FOR NET 24 - - 17. RHOMBOIDAL NET 25 - - 18. SEMICIRCULAR NET 25 - - 19. THE DREDGE 25 - - 20. THE CRAB-POT 26 - - 21. AN OLD BIRD-CAGE USED AS A CRAB-POT 27 - - 22. A YOUNG NATURALIST AT WORK 32 - - 23. A GOOD HUNTING-GROUND ON THE CORNISH COAST 33 - - 24. ROUND BEND HOOK WITH FLATTENED END 37 - - 25. LIMERICK HOOK, EYED 37 - - 26. METHOD OF ATTACHING SNOOD TO FLATTENED HOOK 38 - - 27. METHOD OF ATTACHING SNOOD TO EYED HOOK 38 - - 28. THE LUGWORM 39 - - 29. THE RAGWORM 40 - - 30. DIGGING FOR BAIT 41 - - 31. METHOD OF OPENING A MUSSEL 42 - - 32. FISHING FROM THE ROCKS 46 - - 33. THE PATERNOSTER 48 - - 34. SECTION OF AN AQUARIUM CONSTRUCTED WITH A MIXTURE OF - CEMENT AND SAND 54 - - 35. CEMENT AQUARIUM WITH A GLASS PLATE IN FRONT 55 - - 36. AQUARIUM OF WOOD WITH GLASS FRONT 56 - - 37. HEXAGONAL AQUARIUM CONSTRUCTED OF ANGLE ZINC, WITH - GLASS SIDES 57 - - 38. METHOD OF AERATING THE WATER OF AN AQUARIUM 65 - - 39. AQUARIUM FITTED WITH APPARATUS FOR PERIODIC - OUTFLOW 67 - - 40. JARS FOR PRESERVING ANATOMICAL AND BIOLOGICAL SPECIMENS 76 - - 41. SHOWING THE DIFFERENT STAGES IN THE MAKING OF A SMALL - SPECIMEN TUBE 77 - - 42. SMALL SPECIMEN TUBE MOUNTED ON A CARD 78 - - 43. SMALL CRAB MOUNTED ON A CARD 82 - - 44. SPRING FOR HOLDING TOGETHER SMALL BIVALVE SHELLS 84 - - 45. THE TRIPLET MAGNIFIER 92 - - 46. A SMALL DISSECTING TROUGH 93 - - 47. CELL FOR SMALL LIVING OBJECTS 95 - - 48. SHEET OF CORK ON THIN SHEET LEAD 99 - - 49. WEIGHTED CORK FOR DISSECTING TROUGH 99 - - 50. THE AMOEBA, HIGHLY MAGNIFIED 102 - - 51. " " SHOWING CHANGES OF FORM 103 - - 52. " " FEEDING 103 - - 53. " " DIVIDING 104 - - 54. A GROUP OF FORAMINIFERS, MAGNIFIED 105 - - 55. A SPIRAL FORAMINIFER SHELL 106 - - 56. A FORAMINIFER OUT OF ITS SHELL 106 - - 57. THE SAME FORAMINIFER (FIG. 56) AS SEEN WHEN ALIVE 107 - - 58. SECTION OF THE SHELL OF A COMPOUND FORAMINIFER 107 - - 59. SECTION OF A NUMMULITE SHELL 108 - - 60. _Globigerina bulloides_, AS SEEN WHEN ALIVE, MAGNIFIED 108 - - 61. SECTION OF A PIECE OF NUMMULITIC LIMESTONE 109 - - 62. A GROUP OF RADIOLARIAN SHELLS, MAGNIFIED 111 - - 63. THREE INFUSORIANS, MAGNIFIED 113 - - 64. A PHOSPHORESCENT MARINE INFUSORIAN (_Noctiluca_), - MAGNIFIED 114 - - 65. SECTION OF A SIMPLE SPONGE 116 - - 66. DIAGRAMMATIC SECTION OF A PORTION OF A COMPLEX SPONGE 117 - - 67. HORNY NETWORK OF A SPONGE, MAGNIFIED 118 - - 68. _Grantia compressa_ 120 - - 69. SPICULES OF _Grantia_, MAGNIFIED 120 - - 70. _Sycon ciliatum_ 121 - - 71. _Leucosolenia botryoides_, WITH PORTION MAGNIFIED 121 - - 72. _Chalina oculata_ 122 - - 73. _Halichondria panicea_ 123 - - 74. SPICULES OF _Halichondria_, MAGNIFIED 124 - - 75. AN OYSTER SHELL, BORED BY _Cliona_ 124 - - 76. SPICULES OF _Cliona_ 125 - - 77. THREAD CELLS OF A COELENTERATE, MAGNIFIED 127 - - 78. THE SQUIRREL'S-TAIL SEA FIR (_Sertularia argentea_), - WITH A PORTION ENLARGED 128 - - 79. _Sertularia filicula_ 129 - - 80. " _cupressina_ 130 - - 81. THE HERRING-BONE POLYPE (_Halecium halecinum_) 131 - - 82. _Tubularia indivisa_ 132 - - 83. THE BOTTLE BRUSH (_Thuiaria thuja_) 132 - - 84. _Antennularia antennia_ 133 - - 85. _Aurelia aurita_ 135 - - 86. THE EARLY STAGES OF _Aurelia_ 136 - - 87. _Rhizostoma_ 136 - - 88. _Chrysaora_ 136 - - 89. _Cydippe pileus_ 137 - - 90. SECTION OF AN ANEMONE 139 - - 91. STINGING CELLS OF ANEMONE, HIGHLY MAGNIFIED 140 - - 92. DIAGRAMMATIC TRANSVERSE SECTION OF AN ANEMONE 140 - - 93. LARVA OF ANEMONE 140 - - 94. THE TRUMPET ANEMONE (_Aiptasia Couchii_), CORNWALL; - DEEP WATER 144 - - 95. _Peachia hastata,_ S. DEVON 145 - - 96. _Sagartia pallida,_ DEVON AND CORNWALL 146 - - 97. _Sagartia nivea,_ DEVON AND CORNWALL 147 - - 98. _Corynactus viridis,_ DEVON AND CORNWALL 148 - - 99. _Bunodes thallia,_ WEST COAST 150 - - 100. _Bunodes gemmacea,_ WITH TENTACLES RETRACTED 151 - - 101. _Caryophyllia cyathus_ 152 - - 102. _Sagartia parasitica_ 153 - - 103. THE CLOAK ANEMONE (_Adamsia palliata_) ON A WHELK - SHELL, WITH HERMIT CRAB 154 - - 104. LARVA OF THE BRITTLE STARFISH 158 - - 105. LARVA OF THE FEATHER STAR 160 - - 106. THE ROSY FEATHER STAR 160 - - 107. THE COMMON BRITTLE STAR 162 - - 108. SECTION OF THE SPINE OF A SEA URCHIN 165 - - 109. SEA URCHIN WITH SPINES REMOVED ON ONE SIDE 166 - - 110. APEX OF SHELL OF SEA URCHIN 166 - - 111. SHELL OF SEA URCHIN WITH TEETH PROTRUDING 167 - - 112. INTERIOR OF SHELL OF SEA URCHIN 167 - - 113. MASTICATORY APPARATUS OF SEA URCHIN 167 - - 114. SEA URCHIN DISSECTED, SHOWING THE DIGESTIVE TUBE 168 - - 115. THE SEA CUCUMBER 170 - - 116. A TURBELLARIAN, MAGNIFIED 175 - - 117. _Arenicola piscatorum_ 178 - - 118. THE SEA MOUSE 179 - - 119. TUBE-BUILDING WORMS: _Terebella, Serpula, Sabella_ 182 - - 120. _Terebella_ REMOVED FROM ITS TUBE 183 - - 121. A TUBE OF _Serpula_ ATTACHED TO A SHELL 185 - - 122. _Serpula_ REMOVED FROM ITS TUBE 186 - - 123. THE SEA MAT (_Flustra_) 187 - - 124. _Flustra_ IN ITS CELL, MAGNIFIED 188 - - 125. SEA SQUIRT 189 - - 126. LARVAE OF MOLLUSCS 191 - - 127. SHELL OF THE PRICKLY COCKLE (_Cardium aculeatum_) - SHOWING UMBO AND HINGE; ALSO THE INTERIOR - SHOWING THE TEETH 192 - - 128. INTERIOR OF BIVALVE SHELL, SHOWING MUSCULAR SCARS - AND PALLIAL LINE 193 - - 129. DIAGRAM OF THE ANATOMY OF A LAMELLIBRANCH 194 - - 130. _Mytilus edulis_, WITH BYSSUS 195 - - 131. A BIVALVE SHELL (_Tapes virgineana_) 196 - - 132. _Pholas dactylus_ 199 - - 133. " " INTERIOR OF VALVE; AND _Pholadidea_ - WITH ANIMAL 201 - - 134. THE SHIP WORM 202 - - 135. 1. _Teredo navalis._ 2. _Teredo norvegica_ 202 - - 136. _Gastrochaena modiolina_ 203 - - 137. 1. _Thracia phaseolina._ 2. _Thracia pubescens_, - SHOWING PALLIALLINE 204 - - 138. 1. _Mya truncata._ 2. INTERIOR OF SHELL. - 3. _Mya arenaria._4. _Corbula nucleus_ 205 - - 139. _Solen siliqua_ 206 - - 140. 1. _Solen ensis._ 2. _Cerati-solen legumen._ - 3. _Solecurtus candidus_ 207 - - 141. _Tellinidae_ 208 - - 142. 1. _Lutraria elliptica._ 2. PART OF THE HINGE OF - _Lutraria_, SHOWING THE CARTILAGE PIT. 3. _Macra - stultorum._ 4. INTERIOR OF SAME SHOWING PALLIAL - LINE 210 - - 143. _Veneridae_ 211 - - 144. _Cyprinidae_ 213 - - 145. _Galeomma Turtoni_ 214 - - 146. 1. _Cardium pygmaeum._ 2. _Cardium fasciatum._ - 3. _Cardium rusticum_ 215 - - 147. _Cardium aculeatum_ 215 - - 148. _Pectunculus glycimeris_, WITH PORTION OF VALVE - SHOWING TEETH, AND _Arca tetragona_ 216 - - 149. _Mytilus edulis_ 217 - - 150. 1. _Modiola modiolus._ 2. _Modiola tulipa._ - 3. _Crenella discors_ 218 - - 151. _Dreissena polymorpha_ 219 - - 152. _Avicula_, AND _Pinna pectinata_ 220 - - 153. 1. _Anomia ephippium._ 2. _Pecten tigris._ - 3. _Pecten_, ANIMAL IN SHELL 222 - - 154. _Terebratulina._ THE UPPER FIGURE REPRESENTS THE - INTERIOR OF THE DORSAL VALVE 224 - - 155. UNDER SIDE OF THE SHELL OF _Natica catena_, SHOWING - THE UMBILICUS; AND OUTLINE OF THE SHELL, SHOWING THE - RIGHT-HANDED SPIRAL 225 - - 156. SECTION OF THE SHELL OF THE WHELK, SHOWING THE - COLUMELLA 226 - - 157. DIAGRAM OF THE ANATOMY OF THE WHELK, THE SHELL BEING - REMOVED 228 - - 158. A PORTION OF THE LINGUAL RIBBON OF THE WHELK, - MAGNIFIED; AND A SINGLE ROW OF TEETH ON A MUCH - LARGER SCALE 229 - - 159. EGG CASES OF THE WHELK 230 - - 160. PTEROPODS 231 - - 161. NUDIBRANCHS 234 - - 162. " 235 - - 163. SHELLS OF TECTIBRANCHS 236 - - 164. CHITON SHELLS 238 - - 165. SHELLS OF _Dentalium_ 238 - - 166. _Patellidae_ 239 - - 167. _Calyptraea sinensis_ 241 - - 168. _Fissurellidae_ 241 - - 169. _Haliotis_ 242 - - 170. _Ianthina fragilis_ 242 - - 171. _Trochus zizyphinus_. 2. UNDER SIDE OF SHELL. - 3. _Trochus magnus._ 4. _Adeorbis subcarinatus_ 244 - - 172. _Rissoa labiosa_ AND _Lacuna pallidula_ 244 - - 173. SECTION OF SHELL OF _Turritella_ 245 - - 174. _Turritella communis_ AND _Caecum trachea_ 245 - - 175. _Cerithium reticulatum_ AND _Aporrhais pes-pelicani_ 245 - - 176. _Aporrhais pes-pelicani_, SHOWING BOTH SHELL AND ANIMAL 246 - - 177. 1. _Odostomia plicata._ 2. _Eulima polita._ - 3. _Aclis supranitida_ 246 - - 178. _Cypraea_ (_Trivia_) _europaea_ 247 - - 179. 1. _Ovulum patulum_. 2. _Erato laevis_ 248 - - 180. _Mangelia septangularis_ AND _Mangelia turricula_ 248 - - 181. 1. _Purpura lapillus._ 2. EGG CASES OF _Purpura_. - 3. _Nassa reticulata_ 249 - - 182. _Murex erinaceus_ 249 - - 183. OCTOPUS 251 - - 184. _Loligo vulgaris_ AND ITS PEN 252 - - 185. _Sepiola atlantica_ 252 - - 186. _Sepia officinalis_ AND ITS 'BONE' 253 - - 187. EGGS OF _Sepia_ 254 - - 188. THE NERVE-CHAIN OF AN ARTHROPOD (LOBSTER) 257 - - 189. SECTION THROUGH THE COMPOUND EYE OF AN ARTHROPOD 260 - - 190. FOUR STAGES IN THE DEVELOPMENT OF THE COMMON SHORE - CRAB 261 - - 191. THE BARNACLE 261 - - 192. FOUR STAGES IN THE DEVELOPMENT OF THE ACORN BARNACLE 262 - - 193. A CLUSTER OF ACORN SHELLS 263 - - 194. SHELL OF ACORN BARNACLE (_Balanus_) 263 - - 195. THE ACORN BARNACLE (_Balanus porcatus_) WITH APPENDAGES - PROTRUDED 264 - - 196. A GROUP OF MARINE COPEPODS, MAGNIFIED 265 - - 197. A GROUP OF OSTRACODE SHELLS 265 - - 198. _Evadne_ 266 - - 199. MARINE ISOPODS 267 - - 200. MARINE AMPHIPODS 268 - - 201. THE MANTIS SHRIMP (_Squilla Mantis_) 270 - - 202. THE OPOSSUM SHRIMP (_Mysis chamaeleon_) 271 - - 203. PARTS OF LOBSTER'S SHELL, SEPARATED, AND VIEWED FROM - ABOVE 272 - - 204. A SEGMENT OF THE ABDOMEN OF A LOBSTER 272 - - 205. APPENDAGES OF A LOBSTER 273 - - 206. LONGITUDINAL SECTION OF THE LOBSTER 274 - - 207. THE SPINY LOBSTER (_Palinurus vulgaris_) 275 - - 208. THE NORWAY LOBSTER (_Nephrops norvegicus_) 276 - - 209. 1. THE MUD-BORER (_Gebia stellata_). 2. THE - MUD-BORROWER (_Callianassa subterranea_) 277 - - 210. THE COMMON SHRIMP (_Crangon vulgaris_) 278 - - 211. THE PRAWN (_Palaemon serratus_) 279 - - 212. _Dromia vulgaris_ 282 - - 213. THE HERMIT CRAB IN A WHELK SHELL 282 - - 214. THE LONG-ARMED CRAB (_Corystes Cassivelaunus_) 287 - - 215. SPIDER CRABS AT HOME 288 - - 216. THE THORNBACK CRAB (_Maia Squinado_) 290 - - 217. THE PEA CRAB (_Pinnotheres pisum_) 290 - - 218. THE COMMON SHORE CRAB (_Carcinus maenas_) 291 - - 219. THE SHORE SPIDER 294 - - 220. THE LEG OF AN INSECT 295 - - 221. TRACHEA OF AN INSECT, MAGNIFIED 296 - - 222. SEA-SHORE INSECTS 298 - - 223. MARINE BEETLES OF THE GENUS _Bembidium_ 302 - - 224. MARINE BEETLES 303 - - 225. TRANSVERSE SECTION THROUGH THE BONY FRAMEWORK OF A - TYPICAL VERTEBRATE ANIMAL 306 - - 226. THE SEA LAMPREY 309 - - 227. THE PILCHARD 310 - - 228. THE SKELETON OF A FISH (PERCH) 315 - - 229. THE INTERNAL ORGANS OF THE HERRING 316 - - 230. THE EGG-CASE OF THE DOGFISH 319 - - 231. THE SMOOTH HOUND 320 - - 232. THE COMMON EEL 323 - - 233. THE LESSER SAND EEL 326 - - 234. THE THREE-BEARDED ROCKLING 327 - - 235. THE SNAKE PIPE-FISH 328 - - 236. THE RAINBOW WRASS (_Labrus julis_) 330 - - 237. THE CORNISH SUCKER 330 - - 238. THE FIFTEEN-SPINED STICKLEBACK AND NEST 331 - - 239. THE SMOOTH BLENNY 333 - - 240. THE BUTTERFISH 334 - - 241. THE BLACK GOBY 335 - - 242. THE FATHER LASHER 335 - - 243. THE LESSER WEAVER 337 - - 244. THE COMMON PORPOISE 341 - - 245. _Callithamnion roseum_ 359 - - 246. _Callithamnion tetricum_ 359 - - 247. _Griffithsia corallina_ 361 - - 248. _Halurus equisetifolius_ 361 - - 249. _Pilota plumosa_ 361 - - 250. _Ceramium diaphanum_ 363 - - 251. _Plocamium_ 366 - - 252. _Delesseria alata_ 368 - - 253. _Delesseria hypoglossum_ 368 - - 254. _Laurencia pinnatifida_ 371 - - 255. _Laurencia obtusa_ 371 - - 256. _Polysiphonia fastigiata_ 373 - - 257. _Polysiphonia parasitica_ 374 - - 258. _Polysiphonia Brodiaei_ 374 - - 259. _Polysiphonia nigrescens_ 374 - - 260. _Ectocarpus granulosus_ 378 - - 261. _Ectocarpus siliculosus_ 378 - - 262. _Ectocarpus Mertensii_ 378 - - 263. _Sphacelaria cirrhosa_ 379 - - 264. _Sphacelaria plumosa_ 379 - - 265. _Sphacelaria radicans_ 380 - - 266. _Cladostephus spongiosus_ 380 - - 267. _Chordaria flagelliformis_ 380 - - 268. _Laminaria bulbosa_ 384 - - 269. _Laminaria saccharina_ 384 - - 270. _Alaria esculenta_ 385 - - 271. _Sporochnus pedunculatus_ 385 - - 272. _Desmarestia ligulata_ 386 - - 273. _Himanthalia lorea_ 387 - - 274. _Cystoseira ericoides_ 388 - - 275. TRANSVERSE SECTION OF THE STEM OF A MONOCOTYLEDON 391 - - 276. LEAF OF A MONOCOTYLEDON 392 - - 277. EXPANDED SPIKELET OF THE OAT 393 - - 278. THE SEA LYME GRASS 395 - - 279. _Knappia agrostidea_ 397 - - 280. THE DOG'S-TOOTH GRASS 397 - - 281. THE REED CANARY GRASS 397 - - 282. MALE AND FEMALE FLOWERS OF _CAREX_, MAGNIFIED 399 - - 283. THE SEA SEDGE 400 - - 284. THE CURVED SEDGE 400 - - 285. THE GREAT SEA RUSH 400 - - 286. THE BROAD-LEAVED GRASS WRACK 401 - - 287. THE SEA-SIDE ARROW GRASS 401 - - 288. THE COMMON ASPARAGUS 401 - - 289. THE SEA SPURGE 403 - - 290. THE PURPLE SPURGE 404 - - 291. THE SEA BUCKTHORN 404 - - 292. _Chenopodium botryoides_ 405 - - 293. THE FROSTED SEA ORACHE 406 - - 294. THE PRICKLY SALT WORT 406 - - 295. THE CREEPING GLASS WORT 407 - - 296. THE SEA-SIDE PLANTAIN 408 - - 297. THE SEA LAVENDER 408 - - 298. THE DWARF CENTAURY 410 - - 299. THE SEA SAMPHIRE 412 - - 300. THE SEA-SIDE EVERLASTING PEA 413 - - 301. THE SEA STORK'S-BILL 414 - - 302. THE SEA CAMPION 416 - - 303. THE SEA PEARL WORT 417 - - 304. THE SHRUBBY MIGNONETTE 417 - - 305. THE WILD CABBAGE 418 - - 306. THE ISLE OF MAN CABBAGE 418 - - 307. THE GREAT SEA STOCK 419 - - 308. THE HOARY SHRUBBY STOCK 419 - - 309. THE SCURVY GRASS 419 - - 310. THE SEA RADISH 419 - - 311. THE SEA ROCKET 420 - - 312. THE SEA KALE 421 - - 313. THE HORNED POPPY 422 - - - - - THE SEA SHORE - - - - - CHAPTER I - - _THE GENERAL CHARACTERISTICS OF THE SEA SHORE_ - - -What are the attractions which so often entice us to the sea shore, -which give such charm to a ramble along the cliffs or the beach, and -which will so frequently constrain the most active wanderer to rest and -admire the scene before him? The chief of these attractions is -undoubtedly the incessant motion of the water and the constant change of -scene presented to his view. As we ramble along a beaten track at the -edge of the cliff, new and varied features of the coast are constantly -opening up before us. Each little headland passed reveals a sheltered -picturesque cove or a gentle bay with its line of yellow sands backed by -the cliffs and washed by the foaming waves; while now and again our path -slopes down to a peaceful valley with its cluster of pretty cottages, -and the rippling stream winding its way towards the sea. On the one hand -is the blue sea, full of life and motion as far as the eye can reach, -and on the other the cultivated fields or the wild and rugged downs. - -The variety of these scenes is further increased by the frequent changes -in the character of the cliffs themselves. Where they are composed of -soft material we find the coast-line washed into gentle curves, and the -beach formed of a continuous stretch of fine sand; but where harder -rocks exist the scenery is wild and varied, and the beach usually strewn -with irregular masses of all sizes. - -Then, when we approach the water's edge, we find a delight in watching -the approaching waves as they roll over the sandy or pebbly beach, or -embrace an outlying rock, gently raising its olive covering of dangling -weeds. - -Such attractions will allure the ordinary lover of Nature--the mere -seeker after the picturesque--but to the true naturalist there are many -others. The latter loves to read in the cliffs their past history, to -observe to what extent the general scenery of the coast is due to the -nature of the rocks, and to learn the action of the waves from the -character of the cliffs and beach, and from the changes which are known -to have taken place in the contour of the land in past years. He also -delights to study those plants and flowers which are peculiar to the -coast, and to observe how the influences of the sea have produced -interesting modifications in certain of our flowering plants, as may be -seen by comparing them with the same species from inland districts. The -sea birds, too, differing so much as they do from our other feathered -friends in structure and habit, provide a new field for study; while the -remarkably varied character of the forms of life met with on the beach -and in the shallow waters fringing the land is in itself sufficient to -supply the most active naturalist with material for prolonged and -constant work. - -Let us first observe some of the general features of the coast itself, -and see how far we can account for the great diversity of character -presented to us, and for the continual changes and incessant motions -that add such a charm to the sea-side ramble. - -Here we stand on the top of a cliff composed of a soft calcareous -rock--on the exposed edge of a bed of chalk that extends far inland. All -the country round is gently undulating, and devoid of any of the -features that make up a wild and romantic scene. The coast-line, too, is -wrought into a series of gentle bays, separated by inconspicuous -promontories where the rock, being slightly harder, has better withstood -the eroding action of the sea; or where a current, washing the -neighbouring shore, has been by some force deflected seaward. The cliff, -though not high, rises almost perpendicularly from the beach, and -presents to the sea a face which is but little broken, and which in -itself shows no strong evidence of the action of raging, tempestuous -seas; its chief diversity being its gradual rise and fall with each -successive undulation of the land. The same soft and gentle nature -characterises the beach below. Beyond a few small blocks of -freshly-loosened chalk, with here and there a liberated nodule of flint, -we find nothing but a continuous, fine, siliceous sand, the surface of -which is but seldom broken by the protrusion of masses from below. Such -cliffs and beaches do not in themselves suggest any violent action on -the part of the sea, and yet it is here that the ocean is enabled to -make its destructive efforts with the greatest effect. The soft rock is -gradually but surely reduced, partly by the mechanical action of the -waves and partly by the chemical action of the sea-water. The rock -being almost uniformly soft, it is uniformly worn away, thus presenting -a comparatively unbroken face. Its material is gradually dissolved in -the sea; and the calcareous matter being thus removed, we have a beach -composed of the remains of the flints which have been pulverised by the -action of the waves. Thus slowly but surely the sea gains upon the land. -Thus it is that many a famous landmark, once hundreds of yards from the -coast, now stands so near the edge of the cliff as to be threatened by -every storm; or some ancient castle, once miles from the shore, lies -entirely buried by the encroaching sea. - - [Illustration: FIG. 1.--CHALK CLIFF] - -The coast we have described is most certainly not the one with the -fullest attractions for the naturalist, for the cliffs lack those nooks -that provide so much shelter for bird and beast, and the rugged coves -and rock pools in which we find such a wonderful variety of marine life -are nowhere to be seen. But, although it represents a _typical_ shore -for a chalky district, yet we may find others of a very different nature -even where the same rock exists. Thus, at Flamborough in Yorkshire, and -St. Alban's Head in Dorset, we find the hardened, exposed edge of the -chalk formation terminating in bold and majestic promontories, while -the inner edge surrounding the Weald gives rise to the famous cliffs of -Dover and the dizzy heights of Beachy Head. The hard chalk of the Isle -of Wight, too, which has so well withstood the repeated attacks of the -Atlantic waves, presents a bold barrier to the sea on the south and east -coasts, and terminates in the west with the majestic stacks of the -Needles. - - [Illustration: FIG. 2.--WHITECLIFF (CHALK), DORSET] - -Where this harder chalk exists the coast is rugged and irregular. Sea -birds find a home in the sheltered ledges and in the protected nooks of -its serrated edge; and the countless wave-resisting blocks of weathered -chalk that have been hurled from the heights above, together with the -many remnants of former cliffs that have at last succumbed to the -attacks of the boisterous sea, all form abundant shelter for a variety -of marine plants and animals. - - [Illustration: FIG. 3.--PENLEE POINT, CORNWALL] - -But it is in the west and south-west of our island that we find both -the most furious waves and the rocks that are best able to resist their -attacks. Here we are exposed to the full force of the frontal attacks of -the Atlantic, and it is here that the dashing breakers seek out the -weaker portions of the upturned and contorted strata, eating out deep -inlets, and often loosening enormous blocks of the hardest material, -hurling them on the rugged beach, where they are eventually to be -reduced to small fragments by the continual clashing and grinding action -of the smaller masses as they are thrown up by the angry sea. Here it is -that we find the most rugged and precipitous cliffs, bordering a more or -less wild and desolate country, now broken by a deep and narrow chasm -where the resonant roar of the sea ascends to the dizzy heights above, -and anon stretching seaward into a rocky headland, whose former -greatness is marked by a continuation of fantastic outliers and smaller -wave-worn masses of the harder strata. Here, too, we find that the -unyielding rocks give a permanent attachment to the red and olive weeds -which clothe them, and which provide a home for so many inhabitants of -our shallow waters. It is here, also, that we see those picturesque rock -pools of all sizes, formed by the removal of the softer material of the -rocks, and converted into so many miniature seas by the receding of the -tide. - - [Illustration: FIG. 4.--BALANUS SHELLS] - -A more lovely sight than the typical rock pool of the West coast one can -hardly imagine. Around lies the rugged but sea-worn rock, partly hidden -by dense patches of the conical shells of the _Balanus_, with here and -there a snug cluster of young mussels held together by their -intertwining silken byssi. The surface is further relieved by the -clinging limpet, the beautifully banded shells of the variable -dog-periwinkle, the pretty top shells, and a variety of other common but -interesting molluscs. Clusters of the common bladdery weeds are also -suspended from the dry rock, and hang gracefully into the still water -below, where the mantled cowry may be seen slowly gliding over the olive -fronds. Submerged in the peaceful pool are beautiful tufts of white and -pink corallines, among which a number of small and slender starfishes -may climb unnoticed by the casual observer; while the scene is -brightened by the numerous patches of slender green and red algae, the -thread-like fronds of which are occasionally disturbed as the lively -little blenny darts among them to evade the intruder's glance. Dotted -here and there are the beautiful anemones--the variously-hued animal -flowers of the sea, with expanded tentacles gently and gracefully -swaying, ready to grasp and paralyse any small living being that may -wander within their reach. Here, under a projecting ledge of the rock, -partly hidden by pale green threads, are the glaring eyes of the -voracious bullhead, eager to pounce on almost any moving object; while -above it the five-fingered starfish slowly climbs among the dangling -weeds by means of its innumerable suckers. In yonder shady corner, where -the overhanging rock cuts off all direct rays of the sun from the deeper -water of the pool, are the pink and yellow incrustations of little -sponges, some of the latter colour resembling a group of miniature -inverted volcanic cones, while on the sandy floor of the pool itself may -be seen the transparent phantom-like prawn, with its rapidly moving -spinnerets and gently-waving antennae, suddenly darting backward when -disturbed by the incautious approach of the observer; and the spotted -sand-crab, entirely buried with the exception of its upper surface, and -so closely imitating its surroundings as to be quite invisible except on -the closest inspection. Finally, the scene is greatly enlivened by the -active movements of the hermit-crab, that appropriates to its own use -the shell which once covered the body of a mollusc, and by the erratic -excursions of its cousin crabs as they climb over the weedy banks of the -pool in search of food. - - [Illustration: FIG. 5.--A CLUSTER OF MUSSELS] - -Thus we may find much to admire and study on the sea shore at all times, -but there are attractions of quite another nature that call for notice -on a stormy day, especially on the wilder and more desolate western -coasts. At such times we delight to watch the distant waves as they -approach the shore, to see how they become gradually converted into the -foaming breakers that dash against the standing rocks and wash the -rattling pebbles high on the beach. The powerful effects of the sea in -wearing away the cliffs are now apparent, and we can well understand -that even the most obdurate of rocks must sooner or later break away -beneath its mighty waves. - - [Illustration: FIG. 6.--BREAKERS] - -The extreme mobility of the sea is displayed not only by the storm -waves, and by the soft ripples of the calm day, but is seen in the -gentle currents that almost imperceptibly wash our shores, and more -manifestly in the perpetual motions of the tides. - -This last-named phenomenon is one of extreme interest to the sea-side -rambler, and also one of such great importance to the naturalist that we -cannot do better than spend a few moments in trying to understand how -the swaying of the waters of the ocean is brought about, and to see what -determines the period and intensity of its pulsations, as well as some -of the variations in the daily motions which are to be observed on our -own shores. - -In doing this we shall, of course, not enter fully into the technical -theories of the tides, for which the reader should refer to -authoritative works on the subject, but merely endeavour to briefly -explain the observed oscillations of the sea and the general laws which -govern them. - -The most casual observer must have noticed the close connection between -the movements of the ocean and the position of the moon, while those who -have given closer attention to the subject will have seen that the -relative heights of the tides vary regularly with the relative positions -of the sun, moon, and earth. - -In the first place, then, we notice that the time of high tide in any -given place is always the same at the same period of the cycle of the -moon; that is, it is always the same at the time of new moon, full moon, -&c. Hence it becomes evident that the moon is the prime mover in the -formation of tides. Now, it is a fact that the sun, though about -ninety-three millions of miles from the earth, has a much greater -attractive influence on the earth and its oceans than the moon has, -although the distance of the latter is only about a quarter of a million -miles: but this is due to the vastly superior mass of the sun, which is -about twenty-six million times the mass of the moon. How is it, then, -that we find the tides apparently regulated by the moon rather than by -the sun? - -The reason is that the tide-producing influence is due not to the actual -attractive force exerted on the earth as a whole, but to the difference -between the attraction for one side of the globe and that for the -opposite side. Now, it will be seen that the diameter of the -earth--about eight thousand miles--is an appreciable fraction of the -moon's distance, and thus the attractive influence of the moon for the -side of the earth nearest to it will be appreciably greater than that -for the opposite side; while in the case of the sun, the earth's -diameter is such a small fraction of the distance from the sun that the -_difference_ in the attractive force for the two opposite sides of the -earth is comparatively small. - -Omitting, then, for the present the minor tide-producing influence of -the sun, let us see how the incessant rising and falling of the water of -the ocean are brought about; and, to simplify our explanation, we will -imagine the earth to be a globe entirely covered with water of uniform -depth. - -The moon attracts the water on the side nearest to it with a greater -force than that exerted on the earth itself; hence the water is caused -to bulge out slightly on that side. Again, since the attractive force of -the moon for the earth as a whole is greater than that for the water on -the opposite side, the earth is pulled away, as it were, from the water -on that side, causing it to bulge out there also. Hence high tides are -produced on two opposite sides of the earth at the same time, while the -level of the water is correspondingly reduced at two other parts at -right angles with these sides. - -This being the case, how are we to account for the observed changes in -the level of the sea that occur every day on our shores? - -Let us first see the exact nature of these changes:--At a certain time -we find the water high on the beach; and, soon after reaching its -highest limit, a gradual descent takes place, generally extending over a -period of a little more than six hours. This is then followed by another -rise, occupying about the same time, and the oscillations are repeated -indefinitely with remarkable regularity as to time. - - [Illustration: FIG. 7.--ILLUSTRATING THE TIDE-PRODUCING INFLUENCE OF - THE MOON] - -Now, from what has been previously said with regard to the tidal -influence of the moon, we see that the tide must necessarily be high -under the moon, as well as on the side of the earth directly opposite -this body, and that the high tides must follow the moon in its regular -motion. But we must not forget that the earth itself is continually -turning on its axis, making a complete rotation in about twenty-four -hours; while the moon, which revolves round the earth in about -twenty-eight days, describes only a small portion of its orbit in the -same time; thus, while the tidal wave slowly follows the moon as it -travels in its orbit, the earth slips round, as it were, under the tidal -wave, causing four changes of tide in approximately the period of one -rotation. Suppose, for example, the earth to be performing its daily -rotation in the direction indicated by the arrow (fig. 8), and the tide -high at the place marked A1, just under the moon, then, in about six -hours, this place will have been carried round to A2, where the tide is -low; and, after similar intervals, to A3 and A4 successively, where -the tide is high and low respectively. Hence the daily changes are to a -great extent determined by the rotation of the earth. - -But we have already observed that each change of tide occupies a little -more than six hours, the average time being nearly six hours and a -quarter, and so we find that the high and low tides occur nearly an hour -later every day. This is due to the fact that, owing to the revolution -of the moon round the earth in the same direction as that of the -rotation of the earth itself, the day as measured by the moon is nearly -an hour longer than the average solar day as given by the clock. - - [Illustration: FIG. 8.--ILLUSTRATING THE TIDES] - -There is yet another point worth noting with regard to the relation -between the moon and the tidal movements of the water, which is that the -high tides are never exactly under the moon, but always occur some time -after the moon has passed the meridian. This is due to the inertia of -the ocean, and to the resistance offered by the land to its movements. - -Now, in addition to these diurnal changes of the tide, there are others, -extending over longer periods, and which must be more or less familiar -to everyone who has spent some time on the coast. On a certain day, for -instance, we observe that the high tide flows very far up the beach, and -that this is followed, a few hours later, by an unusually low ebb, -exposing rocks or sand-banks that are not frequently visible. Careful -observations of the motions of the water for some days after will show -that this great difference between the levels of high and low-water -gradually decreases until, about a week later, it is considerably -reduced, the high tide not flowing so far inland and the low-water mark -not extending so far seaward. Then, from this time, the difference -increases again, till, after about two weeks from the commencement of -our observations, we find it at the maximum again. - - [Illustration: FIG. 9.--SPRING TIDES AT FULL MOON] - -Here again we find that the changes exactly coincide with changes in the -position of the moon with regard to the sun and the earth. Thus, the -_spring tides_--those which rise very high and fall very low--always -occur when the moon is full or new; while the less vigorous _neap tides_ -occur when the moon is in her quarters and presents only one-half of her -illuminated disc to the earth. And, as the moon passes through a -complete cycle of changes from _new_ to _first-quarter_, _full_, -_last-quarter_, and then to _new_ again in about twenty-nine days, so -the tides run through four changes from spring to neap, spring, neap, -and then to spring again in the same period. - - [Illustration: FIG. 10.--SPRING TIDES AT NEW MOON] - -The reason for this is not far to seek, for we have already seen that -both sun and moon exert a tide-producing influence on the earth, though -that of the moon is considerably greater than that of the sun; hence, if -the sun, earth, and moon are in a straight line, as they are when the -moon is full, at which time she and the sun are on opposite sides of the -earth, and also when new, at which time she is between the earth and -sun, the sun's tide is added to the moon's tide, thus producing the -well-marked spring tides; while, when the moon is in her quarters, -occupying a position at right angles from the sun as viewed from the -earth, the two bodies tend to produce high tides on different parts of -the earth at the same time, and thus we have the moon's greater tides -reduced by the amount of the lesser tides of the sun, with the result -that the difference between high and low tides is much lessened. - - [Illustration: FIG. 11.--NEAP TIDES] - -Again, the difference between high and low water marks is not always -exactly the same for the same kind of tide--the spring tide for a -certain period, for example, not having the same limits as the same tide -of another time. This is due to the fact that the moon revolves round -the sun in an elliptical orbit, while the earth, at the same time, -revolves round the sun in a similar path, so that the distances of both -moon and sun from the earth vary at different times. And, since the -tide-producing influences of both these bodies must increase as their -distance from the earth diminishes, it follows that there must be -occasional appreciable variations in the vigour of the tidal movements -of the ocean. - -As the earth rotates on its axis, while at the same time the tidal wave -must necessarily keep its position under the moon, this wave appears to -sweep round the earth with considerable velocity. The differences in the -level of the ocean thus produced would hardly be appreciable if the -earth were entirely covered with water; but, owing to the very irregular -distribution of the land, the movements of the tidal wave become -exceedingly complex; and, when it breaks an entrance into a gradually -narrowing channel, the water is compressed laterally, and -correspondingly increased in height. It is thus that we find a much -greater difference between the levels of high and low tides in -continental seas than are to be observed on the shores of oceanic -islands. - -We have occupied so much of our time and space in explanation of the -movements of the tides not only because we think it desirable that all -who delight in sea-side rambles should understand something of the -varied motions which help to give such a charm to the sea, but also -because, as we shall observe later, these motions are a matter of great -importance to those who are interested in the observation and study of -marine life. And, seeing that we are writing more particularly for the -young naturalists of our own island, we must devote a little space to -the study of the movements of the tidal wave round Great Britain, in -order that we may understand the great diversity in the time of high -tide on any one day on different parts of the coast, and see how the -time of high tide for one part may be calculated from that of any other -locality. - -Were it not for the inertia of the ocean and the resistance offered by -the irregular continents, high tide would always exist exactly under the -moon, and we should have high water at any place just at the time when -the moon is in the south and crossing the meridian of that place. But -while the inertia of the water tends to make all tides late, the -irregular distribution of the land breaks up the tidal wave into so many -wave-crests and greatly retards their progress. - -Thus, the tidal wave entering the Atlantic round the Cape of Good Hope -mingles with another wave that flows round Cape Horn, and the combined -wave travels northward at the rate of several hundred miles an hour. On -reaching the British Isles it is broken up, one wave-crest travelling up -the English Channel, while another flows round Scotland and then -southwards into the North Sea. - -The former branch, taking the shorter course, determines the time of -high tide along the Channel coast. Passing the Land's End, it reaches -Plymouth in about an hour, Torquay in about an hour and a half, the Isle -of Portland in two hours and a half, Brighton in about seven hours, and -London in about nine hours and a half. The other branch, taking a much -longer course, makes its arrival in the southern part of the North Sea -about twelve hours later, thus mingling at that point with the Channel -wave of the _next_ tide. It takes about twenty hours to travel from the -south-west coast of Ireland, round Scotland, and then to the mouth of -the Thames. Where the two waves meet, the height of the tides is -considerably increased; and it will be understood that, at certain -points, where the rising of one tide coincides with the falling of -another, the two may partially or entirely neutralise each other. -Further, the flow and the ebb of the tide are subject to numerous -variations and complications in places where two distinct tidal -wave-crests arrive at different times. Thus, the ebbing of the tide may -be retarded by the approach of a second crest a few hours after the -first, so that the ebb and the flow do not occupy equal times. At -Eastbourne, for example, the water flows for about five hours, and ebbs -for about seven and a half. Or, the approach of the second wave may even -arrest the ebbing waters, and produce a second high tide during the -course of six hours, as is the case at some places along the Hampshire -and Dorset coasts. - -Those who visit various places on our own coasts will probably be -interested in tracing the course of the tidal crests by the aid of the -accompanying map of the British Isles, on which the time of high tide at -several ports for the same time of day is marked. It will be seen from -this that the main tidal wave from the Atlantic approaches our islands -from the south-west, and divides into lesser waves, one of which passes -up the Channel, and another round Scotland and into the North Sea, as -previously mentioned, while minor wave-crests flow northward into the -Irish Sea and the Bristol Channel. The chart thus supplies the data by -means of which we can calculate the approximate time of high tide for -any one port from that of another. - - [Illustration: FIG. 12.--CHART SHOWING THE RELATIVE TIMES OF HIGH TIDE - ON DIFFERENT PARTS OF THE BRITISH COAST - _George Philip & Son. Ltd._ _The London Geographical Institute._] - -Although the time of high water varies so greatly on the same day over -such a small area of country, yet that time for any one place is always -approximately the same during the same relative positions of the sun, -earth, and moon; that is, for the same 'age' of the moon; so that it is -possible to determine the time of high water at any port from the moon's -age. - -The time of high tide is generally given for the current year in the -local calendars of our principal seaports, and many guide-books supply a -table from which the time may be calculated from the age of the moon. - -At every port the observed high water follows the meridional passage of -the moon by a fixed interval of time, which, as we have seen, varies -considerably in places within a small area of the globe. This interval -is known as _the establishment of the port_, and provides a means by -which the time of high water may be calculated. - -Before closing this short chapter on the general characteristics of the -sea shore we ought to make a few observations on the nature of the water -of the sea. Almost everyone is acquainted with the saltness while many -bathers have noticed the superior buoyancy of salt water as compared -with the fresh water of our rivers and lakes. The dissolved salts -contained in sea water give it a greater density than that of pure -water; and, since all floating bodies displace their own weight of the -liquid in which they float, it is clear that they will not sink so far -in the denser water of the sea as they would in fresh water. - -If we evaporate a known weight of sea water to dryness and weigh the -solid residue of sea salt that remains, we find that this residue forms -about three and a half per cent. of the original weight. Then, supposing -that the evaporation has been conducted very slowly, the residue is -crystalline in structure, and a careful examination with the aid of a -lens will reveal crystals of various shapes, but by far the larger -number of them cubical in form. These cubical crystals consist of common -salt (sodium chloride), which constitutes about three-fourths of the -entire residue, while the remainder of the three and a half per cent. -consists principally of various salts of magnesium, calcium, and sodium. - -Sea salt may be obtained ready prepared in any quantity, as it is -manufactured for the convenience of those who desire a sea bath at home; -and it will be seen from what has been said that the artificial -sea-water may be prepared, to correspond almost exactly with that of the -sea, by the addition of three and a half pounds of sea salt to about -ninety-six and a half pounds of water. - -This is often a matter of no little importance to the sea-side -naturalist, who may require to keep marine animals alive for some time -at considerable distance from the sea shore, while their growth and -habits are observed. Hence we shall refer to this subject again when -dealing with the management of the salt-water aquarium. - -The attractions of the sea coast are undoubtedly greater by day than at -night, especially in the summer season, when the excessive heat of the -land is tempered by the cool sea breezes, and when life, both on the -cliffs and among the rocks, is at its maximum. But the sea is grand at -night, when its gentle ripples flicker in the silvery light of the full -moon. No phenomenon of the sea, however, is more interesting than the -beautiful phosphorescence to be observed on a dark summer's night. At -times the breaking ripples flash with a soft bluish light, and the water -in the wake of a boat is illuminated by what appears to be liquid fire. -The advancing ripples, as they embrace a standing rock, surround it with -a ring of flame; while streaks and flashes alternately appear and -disappear in the open water where there is apparently no disturbance of -any kind. - -These effects are all produced by the agency of certain marine animals, -some of which display a phosphorescent light over the whole surface of -their bodies, while in others the light-giving power is restricted to -certain organs or to certain well-defined areas of the body; and in some -cases it even appears as if the creatures concerned have the power of -ejecting from their bodies a phosphorescent fluid. - -It was once supposed that the phosphorescence of the sea was produced by -only a few of the lower forms of life, but it is well known now that -quite a large number of animals, belonging to widely different classes, -play a part in this phenomenon. Many of these are minute creatures, -hardly to be seen without the aid of some magnifying power, while others -are of considerable size. - -Among the peculiar features of the phosphorescence of the sea are the -suddenness with which it sometimes appears and disappears, and its very -irregular variations both at different seasons and at different hours of -the same night. On certain nights the sea is apparently full of living -fire when, almost suddenly the light vanishes and hardly a trace of -phosphorescence remains; while, on other occasions, the phenomenon is -observed only on certain patches of water, the areas of which are so -well defined that one passes suddenly from or into a luminous sea. - -The actual nature of the light and the manner in which it is produced -are but ill understood, but the variations and fitfulness of its -appearances can be to a certain extent conjectured from our knowledge -of some of the animals that produce it. - -In our own seas the luminosity is undoubtedly caused principally by the -presence of myriads of minute floating or free-swimming organisms that -inhabit the surface waters. Of these each one has its own season, in -which it appears in vast numbers. Some appear to live entirely at or -near the surface, but others apparently remain near the surface only -during the night, or only while certain conditions favourable to their -mode of life prevail. And further, it is possible that these minute -creatures, produced as they generally are in vast numbers at about the -same time, and being more or less local, are greatly influenced by -changes of temperature, changes in the nature of the wind, and the -periodic changes in the tides; and it is probable that we are to look to -these circumstances for the explanations of the sudden changes so -frequently observed. - -In warmer seas the phenomenon of phosphorescence is much more striking -than in our own, the brilliancy of the light being much stronger, and -also produced by a greater variety of living beings, some of which are -of great size, and embrace species belonging to the vertebrates and the -higher invertebrate animals. - -Those interested in the investigation of this subject should make it a -rule to collect the forms of life that inhabit the water at a time when -the sea is unusually luminous. A sample of the water may be taken away -for the purpose of examination, and this should be viewed in a good -light, both with and without a magnifying lens. It is probable, too, -that a very productive haul may be obtained by drawing a fine muslin net -very slowly through the water. After some time the net should be emptied -and gently washed in a small quantity of sea water to remove the smaller -forms of life contained, and the water then examined at leisure. - -Of course it must not be assumed that all the species so obtained are -concerned in any way with the phosphorescence of the sea, but any one -form turning up in abundance when collected under the conditions named -will probably have some connection with the phenomenon. - -One may well ask 'What is the use of this light-emitting power to the -animals who possess it?' but this question is not easily answered. The -light produced by the glow-worm and other luminous insects is evidently -a signal by means of which they call their mates, and this may be the -case with many of the marine luminous animals, but it is evidently not -so with those which live in such immense numbers that they are simply -crowded together; nor can it be so with the many luminous creatures -that are hermaphrodite. It is a fact, however, that numbers of deep-sea -species possess the power of emitting light to a striking extent; and -the use of this power is in such cases obvious, for since the rays of -the sun do not penetrate to great depths in the ocean, these luminous -species are enabled to illuminate their own surroundings while in search -of food, and, in many cases at least, to quench their lights suddenly at -such times as they themselves are in danger. - - - - - CHAPTER II - - _THE SEA-SIDE NATURALIST_ - - - OUTDOOR WORK - -Assuming that the reader is one who desires to become intimately -acquainted with the wonderful and varied forms of life to be met with on -the sea shore, or, hoping that he may be lured into the interesting and -profitable pastimes of the sea-side naturalist, we shall now devote a -chapter to the consideration of the appliances required for the -collection and examination of marine life, and to general instructions -as to the methods by which we may best search out the principal and most -interesting objects of the shore. - -First, then, we shall describe the equipment of an enthusiastic and -all-round admirer of Nature--he who is interested in plant forms from -the flowering species down to the 'meanest weed that grows,' and is -always ready to learn something of any member of the animal world that -may happen to come within his reach. And this, not because we hope, or -even desire, that every reader may develop into an all-round naturalist, -but so that each may be able to select from the various appliances named -just those which would be useful for the collection and observation of -the objects which are to form his pet study. - -The most generally useful of all these appliances is undoubtedly some -kind of case of the 'hold-all' type, a case into which specimens in -general may be placed for transmission from the hunting-ground in order -that they may be studied at leisure, and we know of nothing more -satisfactory than the botanist's 'vasculum.' This is an oblong box of -japanned tin, fitted with a hinged front, and having both handle and -strap, so that it can be either carried in the hand or slung over the -shoulder. Of course almost any kind of non-collapsible box or basket -will answer the purpose, but we know of no utensils so convenient as the -one we have named. It is perfectly satisfactory for the temporary -storage of the wild flowers gathered on the cliffs, as it will keep them -moist and fresh for some considerable time; and for the reception of sea -weeds of all kinds it is all that could be desired, for it will -preserve them in splendid condition, and is so constructed that there is -no possibility of the inconvenience arising from the dripping of salt -water on the lower garments. Then, as regards marine animal-life in -general--starfishes, urchins, anemones, molluscs, crustaceans, fishes, -&c.--these may be conveyed away in it with a liberal packing of moist -weeds not only without injury, but in such a satisfactory condition that -nearly all may be turned out alive at the end of a day's work; and this -must be looked upon as a very important matter to him who aims at -becoming a naturalist rather than a mere collector, for while the latter -is content with a museum of empty shells and dried specimens, the former -will endeavour to keep many of the creatures alive for a time in some -kind of artificial rock pool in order that he may have the opportunity -of studying their development and their habits at times when he has not -the chance of visiting the sea shore for the purpose. - - [Illustration: FIG. 13.--THE VASCULUM] - -But although the vasculum is so generally useful for the temporary -storage and the transmission of the objects collected, yet it is not in -itself sufficient for all purposes. There are many marine animals so -small--but none the less interesting because they are small--that they -would probably be lost in a case containing a mass of sea weeds with -various larger creatures. These should be placed in small well-corked -bottles, and temporarily preserved in a little sea-water, or, -preferably, a tuft of one of the delicate weeds so common in our rock -pools. Others, again, though they may be larger, are of so fragile a -nature that they should be isolated from the general stock on that -account alone. Instead of bottles or tubes, small tin boxes may be used, -and these have the advantage of being unbreakable, though, of course, -they will not hold water. This, however, is of no consequence, as most -marine animals may be kept alive for some time in moist sea-weed quite -as well as in water. - -When small animals are required for structural examination only, they -may be put into methylated spirit as they are taken, and when stored in -this way a much larger number may be put into the same receptacle; hence -the collector will often find it convenient to have a small supply of -this liquid while at his work. - -A strong pocket-knife is essential for sea-side work. It serves to -remove those molluscs that adhere firmly to the rocks by suction, and -also others that fix themselves by means of a byssus of silken fibres, -as is the case with mussels. It will also be employed in the removal of -acorn barnacles, anemones, and small tufts of algae, and may be useful in -cutting through the stouter weeds. Small sponges and other low forms of -life often form incrustations on the solid rock, and may be peeled off -with the aid of a knife. In the case of the last-named, however, as well -as with the anemones and other fixed animals, it is often far more -satisfactory to remove a small portion of the rock itself with the -animal attached, and for this purpose a small hammer will be of great -service. - -A strong net of some kind is necessary in searching the rock pools, and -as suitable nets are, we believe, not to be obtained of the dealers in -naturalists' appliances, it devolves on one to manufacture a net -according to his requirements. - -The simplest form of net may be made by bending a piece of stout -galvanised iron wire into the form here shown (fig. 14), and firmly -wedging the two straight ends in a short piece of strong metal tube -which will also serve as a ferrule for the attachment of a tough handle. -Such a circular frame although satisfactory for a net to be used in -fresh-water ponds and streams, is not nearly so suitable for the -irregular rocky pools to be met with on the sea coast, for it will not -enable one to search the numerous corners and crevices into which many -marine creatures will retire on being disturbed, but it may be greatly -improved by bending the side opposite the ferrule into a moderately -sharp angle and then turning the angle slightly upward, as shown in fig. -15. - - [Illustration: FIG. 14.--WIRE RING FOR NET] - - [Illustration: FIG. 15.--NET FRAME WITH CURVED POINT] - -Another very convenient net frame may be made by bending the wire into a -rhomboidal form (fig. 16), the ferrule being attached by means of two -short, straight ends at one of the angles. The opposite angle will serve -the purpose of searching into the crannies of the rocks, while the -straight sides will prove very useful in removing the objects that lie -on the sandy bottoms so commonly seen in rock pools. The semicircular -net shown in fig. 18 will also prove useful for working on sands or for -scraping the flatter surfaces of weed-covered rocks. - - [Illustration: FIG. 16.--RHOMBOIDAL FRAME FOR NET] - -The material of the net should be some kind of strong gauze, or a -loosely-woven canvas. Leno answers very well, but is somewhat easily -torn, and will have to be frequently renewed. This, however, may be -avoided to a great extent if, instead of sewing the gauze directly round -the wire, a strip of strong calico be first attached to the frame, and -the gauze then sewn to the calico; for it will be understood that any -fragile material placed round the wire will soon be worn through by -friction against the rugged surfaces of the rocks and stones. The net -itself should not be very deep, and should have no corners; and as to -the length of the handle, that will be determined by the fancy of the -collector, or by the character of the ponds to be searched, but a tough -walking-stick with a crook handle will generally answer all purposes, -the crook being itself frequently useful for removing the larger weeds -and other obstructions. - - [Illustration: FIG. 17.--RHOMBOIDAL NET] - - [Illustration: FIG. 18.--SEMICIRCULAR NET] - - [Illustration: FIG. 19.--THE DREDGE] - -Although the net, as above described, will answer the requirements of -nearly all young collectors, yet there may be some, who, not satisfied -with the exploration of the rocks and pools exposed when the tide is -out, desire to know something of the creatures that live entirely beyond -low-water mark, where the water is generally too deep for work with a -hand net. To such we recommend a small dredge that may be lowered from a -boat and then drawn along the bottom. A good form of dredge is shown in -fig. 19, and a little skill and ingenuity will enable anyone to -construct one with the help of our illustration; but, seeing that the -best work is to be done on rough bottoms, it is absolutely necessary -that both frame and net should be made of the stoutest materials that -can be conveniently employed. - - [Illustration: FIG. 20.--THE CRAB-POT] - -Those who have ever accompanied a fisherman while taking a pull round to -examine the contents of his crab or lobster pots will probably have -noticed what strange creatures, in addition to the edible crabs and -lobsters, sometimes find their way into the trap. These creatures are -often of great interest to a young naturalist, and it will repay him to -take an occasional trip with a fisherman in order to obtain them; or, -still better, to have a crab-pot of his own. The writer has obtained -many good specimens by means of an inexpensive trap, on the same -principle as the ordinary crab-pot, made from an old metal bird-cage of -rather small size. The bottom was removed, and a very shallow bag of -thick canvas fixed in its place; and some of the wires were cut, and -bent inwards so as to allow the easy entrance of moderately large -crustaceans and other creatures, while at the same time they served as a -barrier to their escape. Such a trap, baited with pieces of fish, and -let down to a rocky bottom, will enable the young naturalist to secure -specimens that are seldom seen between the tide-marks; and the animals -thus obtained will include not only those larger ones for which the -opening was made, but also a variety of smaller creatures that may enter -between the wires of the cage. Some of the latter may, of course, escape -by the same way as the trap is being hauled up for examination, but this -is not so likely to occur if the canvas bottom is of a material so -loosely woven that water can pass through it very freely. It will, of -course, occur to the reader that the insertion of a stone or other -weight will assist in sinking the trap; also that the ordinary door of -the cage forms a ready means by which the captives may be removed. - - [Illustration: FIG. 21.--AN OLD BIRD-CAGE USED AS A CRAB-POT] - -One thing more: make it a rule never to go out collecting natural -objects of any kind without a note-book and pencil. This, to the -beginner who is anxious to get to his work, with the idea only too -prevalent with the amateur that the success of his labours is to be -measured only by the number of specimens obtained, may seem quite an -unnecessary part of the equipment. But it must be remembered that there -is much to _observe_ as well as much to collect on a well-selected -coast; and that without the aid of the book and pencil a great many of -the observations made will be forgotten, and thus much interest that -would otherwise be attached to the objects permanently preserved will be -lacking. - -The above appliances include the only necessary equipment of the -sea-side naturalist, with the exception of a few required for occasional -use in connection with the species of a somewhat restricted habitat, and -the outfit of the sea angler. The former will be dealt with in the -chapters where the species concerned are described, while the subject of -sea angling is of such general interest that we propose to devote a -short chapter exclusively to it. - -It may seem hardly necessary to discourse on the nature of the attire -most suitable for sea-side work, since the majority will readily form -their own opinions on this matter, but perhaps a few words of advice to -the inexperienced may not be altogether out of place. First, then, make -it a rule to wear no clothing of any value. The work will lead the -enthusiast over slippery weeds, on treacherous boulders, over rocks -covered with sharp acorn shells, and among slimy and muddy stones, and -many a slip may occur in the course of a day's work. Large pockets -specially but simply made by sewing square pieces of lining on the -inside of an old jacket are a great convenience; a cap rather than a -brimmed hat should be worn unless the latter be considered essential for -protection from a burning summer's sun; and a pair of old shoes, -preferably with rubber soles, are just the thing for both rough and -slippery rocks, as well as for wading through shallow waters. Other -details we can safely leave to the fancy of the reader himself. - -Now comes the most important question 'Where shall we go?' Fortunately -we are favoured with a great extent of coast-line considering the area -of our country, but the character of the coast is so diversified, both -with regard to its scenery and its life, that the naturalist will do -well to carefully select his locality according to the objects he -desires to study. The east coast of England is not generally noted -either for variety or abundance of marine life, and the same is true -both of the south-east and a large portion of the south coast. In some -places the beach is formed of an unbroken stretch of sand on which one -may walk for miles without seeing any sign of life, with the exception -of an occasional empty shell and a few fragments of dried sea-weed -washed in by the breakers during a recent storm; while at the same time -the cliffs, if such exist at all, are not very generous in their -production of the fauna and flora that are characteristic of the shore. -But even on the coasts referred to there are, here and there, isolated -spots where the uplands jut into the sea, giving rise to bold -promontories, at the foot of which are the fallen masses of rock that -afford protection to a moderate variety of truly marine life, while the -rough bottoms beyond yield numerous interesting forms that may be -secured by means of the dredge or suitable traps. Such spots are to be -found where the chalk hills abut on the sea, as at Flamborough and -Beachy Head, but it is in the neighbourhood of Weymouth that the English -coast really begins to be of great interest to the naturalist. From here -to the Land's End almost every part of the shore will yield a great -variety of life in abundance, and the same is true of the rocky coasts -of the west, and also of the more rugged shores of the Isle of Wight. -As an ideal hunting-ground one cannot do better than to select one of -the small fishing towns or villages on the rocky coasts of Devon and -Cornwall. With such a spot as his headquarters the most enthusiastic -sea-side naturalist will find ample employment. The exposed rocks and -rock pools yield abundance of life; and if these be searched when the -tide is out, there will remain plenty of sea angling and other -employments to occupy him at other times. - -We will now describe the actual work of the sea-side naturalist, giving -the necessary instructions for the observation and collection of the -various living things he will meet with. - -First, then, with regard to work on the cliffs, a very few words will -suffice; for, seeing that the objects of interest to be met with here -will consist principally of the various flowers that are peculiar to or -characteristic of the sea shore, and certain insects and other creatures -more or less partial to a life on the cliffs, we may regard these as -coming within the range of the general work of the botanist, -entomologist, &c.; and since instructions for the collection and -preservation of such objects have already been given in former works of -this series, we may pass them over at once in order to deal with those -objects which are essentially marine. - -It has already been hinted that the right time for collecting on the -shore is when the tide is at its lowest; and in order that the best work -may be done the collector should consult the local tide-tables, or -calculate, if necessary, the time of high tide from the establishment of -the port; and, of course, the period of spring tides should be selected -if possible. The time during which work should continue must be -regulated according to the enthusiasm of the collector or the time at -his disposal, but, as a rule, it is advisable to be on the scene of -action about three hours before the time of low tide, with a -determination to work continuously until the lowest ebb of the water. - -On reaching the beach it is always advisable to start by examining the -line of miscellaneous material at high-water mark, along which may be -found quite a variety of objects, more or less interesting, which have -been washed in by the breakers, especially just after a storm, together -with numerous scavengers of the shore that perform a most useful work in -devouring the decomposing organic matter that would otherwise tend to -pollute the air. - -Here we may find many useful and interesting objects of both the animal -and vegetable worlds. Among the former are the empty shells of both -univalve and bivalve molluscs, some of which are more or less worn by -the action of the waves, while others are in splendid condition for -examination and study. Here, too, are various species of sea firs and -the skeletons of sponges; the shell of the cuttle-fish, and occasionally -a cluster of the eggs of this creature--the sea-grapes of the fishermen; -also the egg-cases of the skate and the dog-fish--usually empty, but -sometimes enclosing the young animal still alive; and, lastly, we -frequently meet with portions of the skeletons of fishes in a perfect -state of preservation, the animal matter having been cleared away by the -combined action of the scavengers previously referred to. Then, as -regards the vegetable world, we often find beautiful specimens of -sea-weeds along the high-water mark, some of which are rarely met with -in the rock pools, since they are species that have been detached from -beyond the line of low water, and washed up by the breakers. - -On turning over the debris thus thrown on the beach we intrude on the -privacy of numerous living creatures which immediately scamper away to -find a new hiding-place. These consist principally of sand-hoppers, but -occasionally we find members of the insect world engaged in the same -useful work in addition to the numerous flies that perform their office -of scavengers in the bright sunshine on the top of the matter that -supplies them with food. - -It will be interesting to capture a few of these scavengers, and to -compare them with others of the same order obtained from different -localities. Thus, the flies may be compared with the more familiar house -fly, and the sand-hoppers of high-water mark with similar crustaceans to -be afterwards obtained lower on the beach. - -Attention should now be given to the rocks left exposed by the -retreating tide, and it is here that the real work begins. Examine each -rock pool as soon as possible after it is no longer disturbed by the -waves. Remove any tufts of corallines or other weeds required for study -or preservation, and simply place them, pro tem., in the vasculum or -other receptacle provided for the purpose. These will form a useful -protective packing for other objects that are to be carried away, so -that it will be advisable to secure a moderate amount rather early, even -though they may not be required for any other purpose. Live molluscs, -crabs, small fishes, &c., may all be put in the receptacle with this -weed, and all will probably be still alive after the collecting and the -homeward journey have been completed. Probe the corners of the pool -with the point of the net, and also sweep the net upward among the weeds -to remove any creatures that seek shelter among the fronds. Tufts of -corallines and other weeds should be searched for the small and delicate -starfishes that live among them, and any stones that may cover the -bottom of the pool should be lifted. Anemones may be removed from the -rocks by means of a rather blunt knife; but, if possible, it will be -better to chip off a small piece of the rock with the anemone attached -to it, and wrap it lightly round with a tuft of soft weed previous to -placing it in the collecting case. - -A number of rock pools should be searched in this manner, but those -chosen should vary as much as possible in general character. All very -small and delicate objects should be isolated from the general stock, -and placed, with the usual packing material, either in tin boxes or -small wide-mouthed bottles; and if any animals taken are not required -alive, but only for preservation, they should be preferably killed at -once and then stored in a separate case. Some creatures are easily -killed by simply dropping them into a bottle of fresh water, but others -should be covered with methylated spirit. It should be mentioned, -however, that the natural appearance of some of the crustaceans is quite -destroyed by strong spirit, which soon makes them look as if they had -been boiled. Some species are changed in this way much more readily than -others; and, until sufficient experience has been gained to enable the -young collector to distinguish between them, it will be advisable to -kill and temporarily preserve crustaceans in spirit that has been -considerably diluted with water--about two parts of water to one of -spirit, for example. Further, there are certain fragile starfishes that -have a way of breaking themselves into pieces when dropped into spirit, -or even when suddenly disturbed in almost any other manner. These must -always be handled gently, and if it is required to kill them for -preservation, the best way will be to put them in a little salt water, -and then gradually add fresh water until the desired result is obtained. - -Perhaps the most productive of all sea-shore work is the turning over of -the stones of various sizes near the low-tide mark, and the examination -of the chinks and sheltered hollows of the rocks that are left uncovered -for but a short period. This work should be carried on as near the -water's edge as possible, closely following the receding tide; and the -collector must now be prepared with a number of small bottles or tins -for the isolation of small and delicate specimens. He must also be on -the alert for numerous examples of protective resemblance, in which the -animals concerned so closely resemble their surroundings in colour and -general character of surface that they are detected only by careful -observation, while the difficulty of identification is still further -increased in instances where the creatures remain perfectly still even -when disturbed. - - [Illustration: FIG. 22.--A YOUNG NATURALIST AT WORK] - -Under the stones all manner of animals--fishes, crustaceans, worms, -molluscs, starfishes, anemones, &c.--will be hiding until covered by the -next tide. Some of these will be found on the ground beneath the stones, -and others attached to the under surfaces of the stones themselves; -therefore both should be carefully examined, attention being given at -first to the more active species that hurry away with all speed towards -a new shelter as soon as they find themselves exposed to the light; the -less active creatures may then be secured at leisure. - -The tide will not allow the collector a great deal of time in which to -turn over the most productive stones--those close to the low-water mark, -so there is but little opportunity of observing the movements and other -interesting habits of many of the animals found; hence it is advisable -to secure a good variety of living specimens, especially of the less -familiar species, in order that they may be placed in some kind of -aquarium, temporary or otherwise, for observation at home. - - [Illustration: FIG. 23.--A GOOD HUNTING-GROUND ON THE CORNISH COAST] - -One thing more remains to be done while the tide is well out, and that -is to examine the weed-covered rocks near the water's edge. Lift the -dangling weeds and carefully search the rocks for those low forms of -animal life that form incrustations on the surface, as well as for new -species of anemones, sea firs, &c. Lastly, look well into the dark and -narrow chinks of the rocks, for here several species of lowly animals -that are hardly met with elsewhere may be found, and also certain -crustaceans that delight to squeeze their bodies into the remotest -corner of a sheltered niche. - - - - - CHAPTER III - - _SEA ANGLING_ - - -We do not propose dealing with this subject from the point of view of -the angler, but rather that of the naturalist. The former is actuated -principally, if not entirely, by the mere love of sport; or, it may be, -to a great extent by the desire to obtain a supply of fish for food; and -he generally estimates the success of his expeditions not by the number -of _species_ captured, but by the total weight of his catch, no regard -being paid, as a rule, to the inedible specimens. The naturalist, -however, does not desire weight, or sweetness of flesh. He works the -greatest possible variety of habitats, with the object of determining -the number of species inhabiting the locality and of learning as much as -possible of their general form, habits, and adaptations of structure to -habits. His success is measured by the number and variety of species -caught, and he pays but little attention to superiority of size or -weight, or to the estimated market value of his haul. The element of -sport may enter more or less largely into the pleasure of his -occupation, but the main end in view is to learn as much as possible of -all the species obtainable. - -Further, our remarks will not include the subject of the different kinds -of fishing usually resorted to by sea anglers, but will be confined -almost exclusively to the simple means of catching the common species -that frequent the immediate neighbourhood of the shore. - -If the reader will follow the general instructions given in Chapter II. -on the outdoor work of the marine naturalist, he will undoubtedly make -the acquaintance of a considerable variety of interesting species which -may be captured in the rock pools, found under stones at low tide, or -obtained by means of a small dredge; but his knowledge of our littoral -fishes may be appreciably extended by the occasional employment of rod -and line from rocks and piers, or from a small boat in close proximity -to the shore. - -The appliances required are of a very simple nature, and not at all -costly. The long, heavy rod and strong tackle of the sea angler and -professional fisherman are not at all essential to our purpose, for our -work will be confined almost exclusively to shallow water, and the fish -to be caught will be chiefly of small size. True it is that one may -occasionally find his light tackle snapped and carried away by the -unexpected run of a large fish, for cod and other large species often -approach close to the shore, and bite at baits intended for the smaller -fish that make their home among the partly submerged rocks of the coast; -but such surprises will not frequently occur, and the young naturalist -may learn all he wants to know of the fishes of our shallow waters with -the aid of a light rod of about nine or ten feet and one or two light -lines of no great length. - -It must not be understood, however, that we assume the reader's -disinclination to know anything of the inhabitants of deep water, but -rather that we consider the whole subject of deep-sea fishing quite -beyond the scope of this work. It is a fact that quite a large number of -species, the forms and habits of which are extremely interesting, live -exclusively on deep bottoms. These should undoubtedly be studied by all -who are interested in the various phases of marine life; but unless the -reader is prepared to practise sea fishing in all its branches--to put -his trust in the restless sea, supplied with all the necessary heavy -gear, and to risk those internal qualms that arise from the incessant -swaying of the boat on open waters, he should make arrangements with the -professional deep-sea fisher--preferably a trawler--for the supply of -those disreputable species that invariably form part of the haul, while -the better-known food fishes can always be obtained from dealers for -purposes of study. - -On one occasion we had a rather unique and very successful interview -with a friendly trawler. She was sailing slowly towards her station in a -south-western fishing port, while two of her crew were clearing her -nets, and throwing all refuse into the sea. We rowed behind her in order -to see the nature of the rejected portion of the haul, and finding that -it included specimens of interesting fishes of ill repute, dead but -perfectly fresh, we followed her track, and collected a few for future -examination. Presently our movements were watched from aboard, and we -were invited to pull up to larboard, where a short explanation as to our -wants led to the acquisition of quite a variety of deep-sea life, -including several species of fishes not often seen on land, crabs, -shelled and shell-less molluscs, worms, star-fishes, and various lowly -organised beings, many alive and in good condition, together with -several good food fishes thrown in by way of sympathy. There is no doubt -that a naturalist can obtain much more deep-sea life with the aid of a -friendly trawler than by any amount of 'fishing' with ordinary tackle -from a boat; and this without the necessity of going to sea at all, if -he will only take the opportunity of examining the nets as the boats are -stranded on their return. - -But now to return to our angling:--We have to provide a light rod, about -ten feet long, with a winch, and a line of twisted silk or other thin -but strong material; also a light hand line, and a supply of gut, leads, -shot, and hooks, together with one or two small floats, and a few bait -boxes. - -We do not, as a rule, recommend the amateur angler to use both rod and -hand line at the same time, for the attempt to do this leads to the -neglect of both. In the end it is not likely to lead to any gain, so -many fish being lost through the inability to strike at the moment a -bite is given, and so much time having to be devoted to the baiting of -hooks rather than to the direct management of the lines. In most cases -the rod is much more convenient than the hand line. The young collector -will meet with the greatest variety of species in rocky and weedy -places, where abundant shelter exists for those fishes that prefer to -keep well under cover, and any attempt with a hand line in such spots -will certainly lead to frequent loss of hooks, and often of lead, line, -and temper. Such a line must be reserved for fishing on sandy bottoms, -while the ten-foot rod recommended will enable the angler to do good -work in the rockiest parts without much danger of fouling; and, in fact, -to fish anywhere along the coast. - -The arrangement of hooks and lead must necessarily depend on the -character of the place to be worked, but in all cases we strongly -recommend no such multiplicity of hooks as is made use of by fishermen -and others who fish for food. In their case the use of so many hooks -often pays them well; but, as we have previously hinted, the naturalist -does not desire quantity of fish so much as variety of species. Further, -there is no necessity to make his work heavy and arduous. His desire is -not to spend an undue proportion of his time in baiting hooks, but to -have his line so under control that he is ready to strike at any moment, -and to be able to alter the conditions of his work as often as his ideas -or the conditions change. - -In rugged and weedy places the hooks must be kept free from rocks and -weeds. This may be done by letting down the rod line with a lead at the -bottom, and one or two hooks fastened to gut at such a level as to keep -quite clear of weeds. A much better arrangement, and one which we -ourselves almost invariably employ, consists of a light lead, as a rule -not exceeding an ounce in weight, fastened at the end of the line, and -below it a few feet of gut terminating in a single hook. With such -tackle it is of course necessary to determine previously the depth of -the water, in order to adjust the line to such a length that the hook -keeps clear of rocks and weeds, and a float may be used if desired. - - [Illustration: FIG. 24.--ROUND BEND HOOK WITH FLATTENED END] - -We do not recommend a float for the general work of the marine -collector, for it is a decided advantage to be prepared to bring the -bait to any level from bottom to surface, especially when the water is -so clear that the fish may be seen swimming, in which case one is often -impressed with the desire to capture a specimen in order to establish -its identity, and for such work as this a float is superfluous. If, -however, a float is used, it should be a sliding one, so that it may be -adapted to the rising and falling of the tide. - - [Illustration: FIG. 25.--LIMERICK HOOK, EYED] - -Of hooks there is a great variety to choose from, differing in the form -both of the curve and of the end of the shank. As to the curve, those -with a decided twist are best adapted to our purpose, chiefly on account -of the fact that sea fishes generally have larger mouths than -fresh-water species of the same size, and are consequently better held -with a twisted hook. The shanks of sea hooks are either flattened or -eyed, and each is as good as the other providing the snood is firmly -attached; but some amateurs find a greater difficulty in attaching the -snood to the former than to the latter. - -Gut snoods are recommended for our purpose, and fig. 26 shows one method -by which they may be fastened to a flattened shank, while fig. 27 -illustrates the figure-of-eight knot by means of which the eyed shank -may be firmly secured. The gut should be soaked for some hours in cold -water previous to tying, and it may be kept soft for some considerable -time by giving it a few hours' immersion in a solution of -glycerine--about one part of glycerine to four or five parts of water. - - [Illustration: FIG. 26.--METHOD OF ATTACHING SNOOD TO FLATTENED HOOK] - -Small hooks will be most suitable for our purpose; and if the reader -finds any difficulty in attaching the snood firmly, he may purchase -suitable hooks ready mounted on gut, though, of course, these are more -expensive than the flattened or eyed hooks generally used for -sea-fishing. Such small and fragile hooks may be occasionally snapped -off by the run of a vigorous fish of moderate size, therefore it is -advisable to have a supply of larger hooks, ready fixed on strong -snoods, to be used when it is found that the shore is frequented by -larger fishes than those generally caught close to land. - - [Illustration: FIG. 27.--METHOD OF ATTACHING SNOOD TO EYED HOOK] - -When fishing with a rod and line from rocks, or from piers, the -foundations of which are covered with large weeds, the bait will -frequently be carried by currents among the weeds and snapped off when -endeavours are made to release the hook. This will especially be the -case when the hook is a few feet below the lead, as we have already -suggested it should be. To reduce the frequency of such mishaps, it will -be a good plan to weight the gut below the lead by means of a few split -shot. In fact, in sheltered places, where the water is not disturbed, -these shot may take the place of the lead, but little weight being -necessary for rod fishing in such localities. - -The amateur sea angler is often in great doubt as to the best bait to -use; and, believing that a certain kind of bait is absolutely necessary -for his work in some particular spot, is often at a loss to obtain it. -This bait difficulty is evidently a prevailing one among amateur sea -fishers, if one may judge from the frequent questions asked as to the -best or proper bait to use, and from the very common 'Can you oblige me -with a little bait?' - -This latter question, we believe, is frequently the outcome of -carelessness or laziness on the part of the asker. He has not the -forethought, born of enthusiasm, that would lead him to procure a -suitable bait, at a convenient time, previous to starting off on his -angling expedition, but rather depends on the possibility of being able -to beg or otherwise secure sufficient for his purpose at the time; yet -there are so many good baits that are easily secured at the proper time -and place that the enthusiastic angler need never be at a loss. Some of -these may be collected by himself at low tide, others may be obtained -from local fishermen, or from the tradesmen of the town or village. - - [Illustration: FIG. 28.--THE LUGWORM] - -Some anglers seldom collect their own bait, either purchasing it or -employing some one to collect it for them; but we are of opinion that -the pleasure of a day's fishing begins here, and especially so when the -angler is of the naturalist type, for he will frequently learn more of -the nature and habits of living creatures during one hour's -bait-collecting than during three or four hours' angling. It is true -that the work in question is often a bit laborious, particularly on a -warm day, and that it may be frequently described as dirty and odorous; -but what is that to one who is interested in his employment, and who -derives pleasure in doing his own work? - -Fishermen often use lugworms for bait, and although these constitute one -of the best baits for their own fishing, they are not so suitable for -the purposes of the amateur angler, fishing with small hooks close to -shore. They may be dug out of the sand when the tide is out, and are -most abundant where the sand is mixed with mud. A spade should be used, -and this should be thrust deep into the sand, selecting those spots -where the holes or burrows of the worms most abound. Lugworms should be -used whole; and being of large size, are suitable for baiting large -hooks only. They may be kept alive in wet sand or sea-weed, preferably -the latter for convenience, and stored till required in a wooden box. - -Ragworms also afford good bait, and are particularly adapted for shore -angling with small hooks. Almost all the fishes that frequent our shores -take them readily, but they are not to be found in all localities. They -are to be taken, though not usually in large numbers, on rocky shores -where numerous stones lie among the somewhat muddy deposits of the more -sheltered nooks, where they may be seen on turning over the stones. The -best situation for ragworms, however, is the more or less odoriferous -mud so frequently deposited in the estuaries of rivers and in landlocked -harbours. Here they maybe dug out in enormous numbers with a spade, -attention being directed to those spots where their burrows are most -numerous. They are best stored with a little of the mud in a shallow -wooden box provided with a sliding, perforated lid. - - [Illustration: FIG. 29.--THE RAGWORM] - -Failing a supply of the marine worms just mentioned, the common -earthworm may be used as a substitute, but it is decidedly less -attractive to the fishes; and the same may be said of gentles--the larvae -or grubs of flies. The latter may be bred in large numbers by simply -placing a piece of liver in the soil with only a small portion exposed. -If this is done in the summer time, hundreds of eggs will soon be -deposited on it, and in about a week or so it will be found to be a -living mass of fat white grubs, perhaps more useful to the fresh-water -angler than to his marine counterpart. - -Among the so-called shell fish of the class _mollusca_, mussels, -limpets, cockles, and whelks are all largely used for bait. The last of -these are too large for our purpose, but form a splendid bait for -deep-sea fishing, while the other three, and especially the mussels, are -well suited for shore work. Mussels, in fact, provide one of the best -possible baits for almost all kinds of shore fishing, the only drawback -being the excessive softness of their bodies, which enables them to be -easily torn from the hook. When small hooks are used, mussels of a small -size may be used whole, or the larger ones may be divided into portions -of suitable size; and in any case it will be found a good plan to tie -the bait to the hook with a short piece of cotton thread. - - [Illustration: FIG. 30.--DIGGING FOR BAIT] - -Mussels are not easily opened without injury, and consequently some -anglers give them a short immersion in hot water, to kill the animal and -thus cause the shell to gape. As far as our own experience goes, the -value of the bait is not deteriorated by this treatment, though some are -of opinion that it is not so attractive after scalding. Mussels are -opened, when alive, much in the same way as oysters, but the valves of -the shell fit together so closely that it seems at first almost -impossible to insert a knife between them. This, however, can be done -with ease if one valve is first made to slide a little way over the -other by pressing it with the thumb. This being accomplished, the two -valves should not be separated by the mere force of the knife, for this -would tear the animal within, and render it more or less unfit for its -purpose; but first direct the edge of the knife towards the _adductor -muscle_, by means of which the animal pulls its valves so firmly -together, and then cut through this close to the inner surface of the -upper valve. This valve can then be lifted without injury to the soft -parts, and the whole animal removed from the other valve by cutting -through the same muscle close to it. - - [Illustration: FIG. 31.--METHOD OF OPENING A MUSSEL] - -Between the two lobes of the _mantle_--the soft covering on both sides -of the animal that previously lined the shell--will be seen a brown, -fleshy, tongue-like body. This is the 'foot' of the mussel. The point of -the hook should first be run through this, and then from side to side -through the mantle, and finally through the adductor muscle previously -described. If this is carefully done, there will be little fear of the -bait becoming detached unless it is subjected to rough usage, and still -less if it is tied round the shank of the hook by means of a short piece -of cotton thread. - -It is probably superfluous to mention to the reader the fact that -mussels are to be found on almost every rocky coast, where they may be -seen attached to the rocks by means of a bunch of silky fibres called -the _byssus_; and that, failing this, they are to be obtained from -almost every fisherman and fish-dealer; if, however, these molluscs are -not to be obtained, cockles may be used as a substitute, though it will -probably be found that they are appreciably inferior, except when -fishing for dabs and plaice on sandy shores, in which case they are -highly satisfactory. Cockles abound on most sandy coasts, where they -live a little below the surface; and are usually obtained by means of an -ordinary garden rake. Sometimes we meet with them in large numbers in -the estuaries of rivers, where they lie buried in the banks of mixed -sand and mud that are left exposed at low tide. - -Limpets are extensively used for bait in some places, especially by -amateur anglers; and often with good results. They should always be -removed from the rocks without injury, and this is no easy matter to -those who do not know how to deal with them. If taken completely by -surprise, one sharp, but light tap on the side of the conical shell will -successfully detach them from their hold; or they may be raised by means -of the blade of a strong pocket-knife that has been thrust beneath the -cone. - -For our work small limpets will prove far more satisfactory than large -ones, and these may be used whole; but if the limpets are too large for -the hooks employed, the soft, upper part of the body only need be used. - -It is not an easy matter to remove fresh limpets from their shells -without destroying this soft portion of the animal, but if placed for a -minute or so in hot water they come out quite easily, and are apparently -none the less attractive as bait. Some fishermen on the Cornish coast -always collect the largest limpets for bait, remove them from their -shells by means of hot water, and arrange them on the rocks to become -partly dry. When required for bait, the soft parts only are used, but -these, having been more or less hardened by the drying process, hold -much better on the hook than when fresh. - -And now, after mentioning the fact that land snails are occasionally -used, though, we believe, with no very considerable success, for sea -fishing, we will note a few baits derived from the higher head-footed -molluscs--the squid, cuttle-fish, &c. There are several species of these -peculiar molluscs, but the common squid and the common cuttle of our -seas, and especially the former, is highly prized as bait. It may be -obtained from fishermen, who frequently haul it in their nets; but if -supplied alive and fresh from the sea it must be handled very -cautiously, otherwise it may discharge the contents of its ink-bag over -one with the most unpleasant results. It is certainly best used while -fresh, though some suspend it until dry, and then store it for future -use, in which case it will require soaking in water when required. The -thin tentacles or arms are very convenient for baiting small hooks, -though other parts of the body, cut into narrow strips, will serve the -purpose of the angler equally well. - -Of the crustaceans, shrimps and prawns, and various species of crabs are -used as bait. Shrimps and prawns are used whole for catching flat-fish, -but small pieces are better when fishing for smelt and other small -species of fish that swim close to shore. Little pieces of the flesh of -the crab are also well adapted for baiting hooks of small size, and will -prove very attractive to almost all kinds of fish. Small crabs, however, -may be used whole, but are of little use except when soft--that is, just -after the shedding of their shells, and before the new skin has had time -to harden. Such crabs may be found under stones and in other -hiding-places at low tide, for at such times they keep well secluded -from their numerous enemies by whom they are greedily devoured while in -this helpless and unprotected condition. - -The hermit-crab, which selects the empty shell of a whelk or winkle for -its home, is probably well known to our readers. The protection afforded -by such a home is absolutely necessary to its existence, since its -abdomen has no other covering than a soft, membranous skin. This soft -abdomen is frequently used as a bait with great success, as well as the -flesh of the larger claws. - -If the shell from which the hermit-crab is taken be broken, a worm, -something of the nature of the common ragworm, will almost always be -found, and this also is very serviceable as bait. - -In addition to all the baits previously named there are several other -good ones, many of which are to be obtained almost everywhere. Among -these may be mentioned strips cut from the mackerel, herring, or -pilchard, preferably with a portion of the silvery skin attached; also -thin strips of tripe. Sand-eels, which may be dug out of the sand near -the water's edge, are very useful, and may be cut into pieces for -baiting small hooks. Further, a large number of artificial baits are -employed in various kinds of sea fishing, but as these are not -essential for the work we have in hand we do not propose describing them -in detail. - -Now let us suppose that we are about to try our luck at sea angling, on -some rocky coast, such as that of Devon and Cornwall, our object being -to determine, as far as possible, what species of fishes frequent the -immediate neighbourhood of the shore. And this is not all; for, when -fishing with rod and line on such a coast, it frequently happens that we -land some species of crab that has been attracted to our bait. The -ordinary angler would regard such crab as an intruder, and, we are sorry -to say, would often consider it his duty to crush the unfortunate -crustacean beneath his foot. But it is far different with the -naturalist. He favourably regards all creatures from which something may -be learnt, and is as anxious, as a rule, to gather information -concerning the habitats of one class as of another. In fact, we may go -still further, and combine crab fishing with ordinary angling, both in -one and the same expedition, by letting a small crab-pot down into deep -water among the rocks, and allowing it to remain while the angling is -proceeding. - -We select a spot where there are several feet of water close to a -perpendicular rock, varied and broken by numerous holes and crevices, in -which various species of fishes and crustaceans habitually hide. - -Such a situation is an ideal one for a young naturalist, for not only -does he obtain the greatest variety of species here, but the takings -will surely include some of those remarkably interesting rock-dwelling -fishes that differ from our ordinary food fishes in so many points of -structure, all of which, however, display some interesting adaptation to -the habits and habitats of the species concerned. - -Our apparatus consists of nothing more than rod and line, one or two -small leads, a supply of hooks on gut snoods, a box of bait, and a -waterproof bag in which to pack the specimens we desire to preserve. - -We first determine the depth of the water by means of a lead on the -_end_ of the line, and then tie the hook on the end with a small lead a -few feet above it, and fish in such a manner that the hook is just on -the bottom, or, if the bottom is covered with weeds, the hook should be -kept just clear of fouling them. - -The peculiar rock fishes so common on such a coast as this on which we -are engaged need special treatment at the hands of the angler. They hide -in their holes, watching for the unwary creatures on which they feed, -and, pouncing upon them suddenly, rush back to their snug little nooks -in which they can secure themselves firmly by means of the sharp, hard -spines with which their bodies are furnished. When these fishes seize -the bait offered them--and they are not at all fastidious in the choice -of their viands--they should be hooked and pulled up with one vigorous -sweep of the rod, or they will dart into their homes, from which it is -almost impossible to dislodge them. - - [Illustration: FIG. 32.--FISHING FROM THE ROCKS] - -In addition to these, there will be various other species that require -gentler treatment, and may be hooked and landed much in the same manner -as fresh-water fishes, since they are free swimmers, usually keeping -well clear of the rocks and weeds. - -If the day is calm, and the water clear, the sea angler will often be -able to watch various fishes as they swim, and to bring the bait gently -within their reach; and here we find the advantage of the rod as -compared with the hand line. Sometimes quite a shoal of small fishes may -be seen sporting near the surface, and, as a rule, there will be no -difficulty in obtaining one for identification and study. These are -generally best secured by means of small hooks, with but very little -bait, and will often bite freely at the tiniest fragment of worm on an -almost naked hook. - -After the water has been searched at all depths, it will be well to -allow the bait to rest quite on the bottom, even at the risk of losing a -hook or two in the weeds and rocks. This may enable one to take some -fresh species of fish or to secure a crustacean or other creature that -is not often found between the tide-marks. Care should be always taken, -however, to keep the hook well clear of the weeds that grow on the sides -of the rock, and sway to and fro with every movement of the restless -waters. - -Angling from piers may be pursued much in the same manner as described -above in those places where the bottom is rocky, but since the chances -of hooking large fish are greater here than close to shore, it is -necessary to be provided with stronger tackle and larger hooks. If, -however, the bottom is sandy, the rod tackle may be modified by placing -the lead at the bottom, and arranging two or three hooks above it, about -one or two feet apart, the lowest one being near the lead. With such an -arrangement the line may be cast some distance out, but for angling -close to the pier itself there is, perhaps, nothing better than the -single-hook arrangement suggested above, for with this one may fish on -the bottom and at all depths without any alteration in the tackle being -necessary. - -If, however, the rod line is to be cast as suggested above, or if a hand -line is to be similarly used, the following hints may be useful as -regards the arrangement of hooks and lead. - -The line itself may be of twisted silk or hemp, terminated with about a -yard of strong gut. The lead, preferably of a conical or pear-shaped -form, should be placed at the extreme end, and its weight regulated -according to the necessities of the occasion. A few ounces of lead are -quite sufficient where there are no strong currents, but it is well to -be supplied with larger sizes, to be substituted if circumstances -require it. Two hooks will be ample. One of these should be only a few -inches from the lead, and the other about eighteen or twenty inches -higher. The whole arrangement, known as a Paternoster, is represented in -fig. 33, in which the method of fixing the lead and the hook links is -also illustrated. - - [Illustration: FIG. 33.--THE PATERNOSTER] - -It will be seen that a swivel has been introduced in connection with the -bottom hook, the object being to show the manner in which this useful -piece of tackle is fitted. It must not be supposed, however, that -swivels are always necessary. It is often useful to insert a swivel on -the line itself, above the Paternoster, when it is of twisted material, -in order to prevent it from kinking; but its use is more frequently -serviceable on the hook links, especially when fishing where the -currents are strong. When the bait used is one that presents two flat -surfaces to the water, as would be the case with a strip of mackerel, a -strong current will set it spinning round and round, thus causing the -hook link to kink if it has not been fitted with a swivel, and the same -effect is often produced by the spinning of a fish on the hook. - -The employment of a suitable ground bait will often make a wonderful -difference in the angler's haul. It frequently attracts large numbers, -keeping them near at hand for some considerable time, and apparently -sharpens their appetite. It may be often observed, too, that a fish will -bite freely at the angler's bait when in the neighbourhood of the ground -bait, while the former is viewed with suspicion in the absence of the -latter. - -When fishing on the bottom only, the ground bait should be weighted if -it is of such a nature that it does not sink readily or if it is liable -to be carried away by currents; but it will often be found more -convenient to secure it on the end of a string, tied up in a muslin bag -if necessary, so that it may be adjusted to any desired depth. - -Among the attractive viands suitable for this purpose we may mention -mussels, crushed crabs, pounded liver, the guts of any oily fish, and -the offal of almost any animal. - -Along the east coast, and in some of the sandy bays of Devon and -Cornwall, fishing from the beach is practised, but we can hardly -recommend this as of much value to the amateur whose object is to obtain -as great a variety as possible of fishes for study. Some good food -fishes are often caught by this means, but the methods employed are -often very primitive, and would lack all interest to those who love good -sport. - -On the east coast a long line, fitted with many hooks, is slung out as -far as possible by means of a pole, and the home end either held in the -hand of the fisher or fastened to the top of a flexible stick driven -into the sand. The latter plan becomes necessary when more than one line -is owned by the same individual, and he is made aware of the bite of a -large fish--and a large fish only, since the hooks are placed beyond a -heavy lead--by the bending of the stick. - -The naturalist, however, is as much interested in the small fish as the -large ones, and, even for beach fishing, a rod and line, fitted with one -or two hooks only, and a lead no heavier than is absolutely essential, -will be preferable. A little practice will of course be necessary in -order that one may become expert in the casting of the rod line, but -with large rings on the rod, and a reel without a check, or a check that -can be thrown off when desired, the necessary proficiency in casting -ought to be acquired without much difficulty. - -In some of the sandy bays of the south-west, long lines with a heavy -lead at both ends and baited hooks at short intervals throughout the -whole length, are placed on the sand at low tide close to the water's -edge, and left unwatched until the next tide is out. As far as our -observations go this primitive mode of fishing is usually anything but -successful, the receding of the tide generally revealing a long row of -clean hooks, with, perhaps, one or two dead or half-dead fish; and it is -probable that most of the bait is devoured by crabs and other -crustaceans before the water becomes sufficiently deep to allow the -desired fishes to reach it. - -There is one other method of fishing on which we may make a few remarks, -although it hardly comes under the heading of shore fishing. We refer to -a method of catching surface fishes from a moving boat, which method is -known as whiffing. The line is weighted with a lead which must be -regulated according to the speed of the boat. If the boat is an ordinary -rowing-boat, kept going at only a moderate speed, a few ounces of lead -will be sufficient, but a whiffing line trailing behind a sailing boat -travelling in a good breeze will require a pound or two of lead to keep -the bait only a little below the surface. - -Beyond the lead we have three or four yards of gimp or strong gut, at -the end of which is a single hook fitted with a spinner, or baited with -some attractive natural or artificial bait. Whatever be the bait used, -there will certainly be more or less spinning caused by the resistance -offered by the water, hence it will be necessary to have a swivel beyond -the lead. - -When whiffing near the shore, care must be taken to avoid outlying rocks -that approach the surface of the water, or a sudden snapping of the line -will give you an unwelcome warning of their existence. Further, we -should note that the fishes which are to be caught when whiffing do not -always swim at the same depth, thus it will be advisable to fish at -different distances from the surface by varying either the weight of the -lead or the speed of the boat. - - - - - CHAPTER IV - - _THE MARINE AQUARIUM_ - - -We have already advised our readers to take home their specimens alive -for the purpose of studying their growth and habits. Now, although there -may be some difficulties in the way of keeping marine animals and plants -alive for any considerable time, yet we are inclined to emphasise the -importance of this matter, knowing that the pleasure and instruction -that may be obtained from even a moderately successful attempt to carry -this out will far more than compensate for the amount of trouble -entailed. There are very many marine objects that are exceedingly pretty -and also very instructive, even when studied apart from the life with -which they were associated in the sea. Thus, a well-preserved sea-weed -may retain much of its original beauty of form and colour, the shells of -numerous molluscs and crustaceans exhibit a most interesting variety of -features well worthy of study, and a number of the soft-bodied animals -may be preserved in such a manner as to closely resemble their living -forms. This being the case, we can hardly say anything to discourage -those who gather sea-side objects merely for the purpose of making a -collection of pretty and interesting things to be observed and admired. -Such objects must necessarily afford much pleasure and instruction, and -the time spent in the collection and preparation will certainly cause -the collector to stray to the haunts of the living things, where he is -certain to acquire, though it may be to a great extent unconsciously, a -certain amount of knowledge concerning their habits and mode of life. -Moreover, sea-side collecting is one of the most healthy and -invigorating of all out-door occupations, and for this reason alone -should be encouraged. - -Yet it must be observed that he whose sea-side occupation is merely that -of a collector, and whose work at home is simply the mounting and -arranging of the objects obtained, can hardly be considered a -naturalist. Natural history is a living study, and its devotee is one -who delights in observing the growth and development of living things, -watching their habits, and noting their wonderful adaptation to their -environments; and it is to encourage such observation that we so -strongly recommend the young collector to keep his creatures alive as -far as it is possible to do so. - -The first thing to settle, then, is the nature of the vessel or vessels -that are to serve the purpose of aquaria for the work of the young -naturalist. - -As long as the outdoor work is in progress temporary aquaria will be -very useful as a means by which the objects collected may be sorted and -stored until a final selection is made for the permanent tank. These -temporary aquaria may consist of jars or earthenware pans of any kind, -each containing a few small tufts of weed, preferably attached to pieces -of rock, and a layer of sand or gravel from the beach. - -As such temporary aquaria will, as a rule, be within a convenient -distance from the sea-side where the collecting is being done, there -will be, we presume, no great difficulty in the way of obtaining the -frequent changes of water necessary to keep the animals and plants in a -healthy condition, so that we need do no more now than urge the -importance of avoiding overcrowding, and of renewing the water -frequently for the purpose of supplying the air required for the -respiration of the inmates. - -When it is desired to isolate small species in such a manner that their -movements may be conveniently observed, glass jars answer well; but -whatever be the form or size of the vessels used, care must be taken to -avoid excess of both light and heat. They should be kept in a cool -place, quite out of the way of direct sunshine, and the glass vessels -used should be provided with a movable casing of brown paper to exclude -all light except that which penetrates from above. - -Even temporary aquaria, used merely for the purpose suggested above, -should be carefully watched, for a single day's neglect will sometimes -result in the loss of several valuable captives. A dead animal should be -removed as soon as it is discovered to avoid the unpleasant results -arising from the putrefaction of its body. The appearance of a scum or -film on the surface of the water should always be regarded with -suspicion. Such a scum should be removed with the aid of absorbent -paper, since it tends to prevent the absorption of oxygen from the air; -and, should the water be tainted in the slightest degree, it should be -changed at once, or, if this is not practicable, air should be driven -into it for some time by means of a syringe with a very fine nozzle. -Such precautions, however, are not so urgently needed when the aquarium -contains crustaceans only, for the majority of these creatures suffer -less than others in the tainted sea water, some even being apparently -quite as comfortable in this as in a supply fresh from the sea. -Sea-weeds exhibiting the slightest tendency to decay must be removed at -once; and, as regards the feeding of the animals, one must be careful to -introduce only as much food as is required for immediate use, so that -there be no excess of dead organic matter left to putrefy. Some of the -marine animals obtained from our shores feed entirely on the minute and -invisible organisms that are always present in the sea water, and others -subsist principally on certain of the weeds. Many, however, of a more -predaceous disposition, capture and devour living prey, while some, and -more especially the crustaceans, are partial to carrion. If, therefore, -the observer desires to study the ways in which the various creatures -secure and devour their food, he should introduce into his aquaria live -marine worms and other small animals, and also small pieces of fish or -flesh. - -We will now pass on to the more serious undertaking of the construction -and management of a permanent salt-water aquarium. - -The first point to decide is, perhaps, the size of the proposed vessel, -and this will in many cases be determined partly by a consideration of -the space at one's disposal, and of the apartment it is intended to -occupy. If it is to be placed in a drawing-room or other ordinary -apartment of a dwelling-house, preference should be given to a window -facing the north in order to avoid the direct rays of the sun, but -perhaps no situation is more suitable than a cool conservatory in the -shady part of a garden; and in either case a strong table or other -support should be provided, of a form and size adapted to those of the -aquarium to be constructed. - -Various materials may be used in the construction of such an indoor -aquarium, and we shall deal with two or three different types, so that -the reader may make his selection according to his fancy, or to his -mechanical ability, if he intends that it shall be of his own -construction. - -We will begin with an aquarium constructed entirely of a mixture of -cement and fine sand, this being the most inexpensive and certainly the -easiest to make; and although it may not be regarded as the most -ornamental--but opinions will differ on this point--yet it has the -decided advantage of being the nearest approach to the natural rock -pool. Though somewhat heavy and cumbersome, even when empty, the amount -of material used in its construction may be varied according to the -taste and convenience of the maker. Further, this form of aquarium is -one that will readily admit of structural alterations at any future -period. It may be deepened at any time; lateral additions or extensions -may be made, or a portion may at any time be shut off for the purpose of -isolating certain of the animals procured. - - [Illustration: FIG. 34.--SECTION OF AN AQUARIUM CONSTRUCTED WITH A - MIXTURE OF CEMENT AND SAND] - -The first thing to do is to prepare a flat, strong slab of hard wood or -stone, the exact shape and size of the desired artificial pool, and then -cover this, if of wood, with a mixture of fine sand and cement, mixed to -a convenient consistency with water, to the depth of about one inch. The -banks or walls of the pool must then be built up on all sides, and this -is best done by the gradual addition of soft pellets of cement, applied -in such a manner as to produce an irregular surface. Unless the walls of -the aquarium be very thick and massive the cement will soon show a -tendency to fall from its place as the height increases, but this may be -avoided by doing the work in instalments, allowing each portion to set -before further additions are made to the structure. - -Since some marine animals like to occupy snug and shady niches in deep -water while others prefer full exposure to the light in shallows, -arrangements should be made for all by varying the depth of the bed, and -providing several little tunnels and caverns. This may be accomplished -either by working the cement itself into suitable form, or by means of -piled stones obtained from the sea beach; and if the latter plan is -adopted, the stones should not be obtained until the aquarium is quite -ready for its living contents; for then a selection of stones and rock -fragments with weeds, anemones, sponges, and other fixed forms of life -attached to them, may be made. The natural appearance of a rock pool is -thus more nearly approached, and in a shorter time than if the sedentary -life were required to develop on an artificial ground. - -Objection may be raised to the form of aquarium just described on the -ground that no life within it is visible except when viewed from above. -But is not this also the case with a rock pool on the sea shore? And has -any admirer of nature ever been heard to complain of the beauties of -such a pool because he was unable to look at them through the sides? -Further, it may be urged that the inmates of our aquarium will be living -under more natural conditions than those of the more popular glass-sided -aquaria, _because_ they receive light from above only. - - [Illustration: FIG. 35.--CEMENT AQUARIUM WITH A GLASS PLATE IN FRONT] - -However, should the reader require a glass front to his cement tank, the -matter is easily accomplished. Three sides are built up as before -described. A sheet of thick glass--plate glass by preference--is then -cut to the size and shape of the remaining space, and this is fixed by -means of cement pressed well against its edges, both inside and outside. - -Water should not be put into the tank until it is quite dry; and, if one -side is made of glass, not until the cement surrounding the edge of the -glass has been liberally painted with marine glue, hot pitch, or some -other suitable waterproof material. - -If any pipes are required in connection with the water supply of the -aquarium, according to either of the suggestions in a later portion of -this chapter, such pipes may be fixed in their proper places as the -cement sides are being built up. - -The next type of aquarium we have to describe is of low cost as far as -the materials are concerned, and one that may be made by any one who has -had a little experience in woodwork; and although the tank itself is of -a simple rectangular form, yet it may be made to look very pretty with a -suitable adjustment of rocks and weeds. - -It consists of a rectangular box, the bottom, ends, and back of which -are of hard wood, firmly dovetailed together, and the front of plate -glass let into grooves in the bottom and ends. All the joints and -grooves are caulked with marine glue, but no paint should be used in the -interior. - -This form of tank may be vastly improved by the substitution of slabs of -slate for the wood, though, of course, this change entails a much -greater expenditure of both time and cash; but supposing the work to be -well done, the result is everything that could be desired as far as -strength and durability are concerned. - - [Illustration: FIG. 36.--AQUARIUM OF WOOD WITH GLASS FRONT] - -In either of the rectangular tanks just described glass may be used for -two sides instead of one only; and since this is not a matter of very -great importance, the choice may well be left to the fancy of the one -who constructs it. - -Some prefer an aquarium with glass on all sides, and where this is the -case the framework may be made of angle zinc with all the joints -strongly soldered. Such an aquarium may be made in the form of any -regular polygon, for it is no more difficult to construct one of six or -eight sides than of four. It is more difficult, however, to make such an -aquarium perfectly watertight, for the glass, instead of being in -grooves, has to be securely fastened to the metal frame by means of a -cement on one side only, and this cement has to serve the double purpose -of holding the glass and keeping in the water. - -Various mixtures have been suggested for this purpose, and among them -the following are perfectly satisfactory:-- - - 1. Litharge 2 parts - Fine sand 2 " - Plaster of Paris 2 " - Powdered resin 1 part - -Mix into a very thick paste with boiled linseed oil and a little driers. - - 2. Red lead 3 parts - Fine sand 3 " - Powdered resin 1 part - -Mix with boiled linseed oil as above. - -Both these cements should be applied very liberally, and the aquarium -then allowed to remain quite undisturbed for at least two weeks before -any water is introduced. - - [Illustration: FIG. 37.--HEXAGONAL AQUARIUM CONSTRUCTED OF ANGLE ZINC, - WITH GLASS SIDES] - -When ready for the water, the bottom of the aquarium should be covered -with a moderately thick layer of fine sand from the sea shore, and -stones then piled in such a manner as to form little tunnels and caves -to serve as hiding-places for those creatures that prefer to be under -cover. As to the selection of stones, we have already suggested that -some may have weeds rooted to them, and that pieces of rock with -anemones, sponges, and other forms of life attached may be chipped off. -Further, on many of our rocky coasts we may find, near low-water mark, a -number of stones covered with a layer of vegetable growth, amongst which -many small animals live, often more or less concealed by their -protective colouring. Some of these stones placed on the bed of the -salt-water aquarium would add greatly to the natural appearance, as well -as give greater variety to the living objects. Shells bearing the -calcareous, snakelike tubes of the common serpula (p. 121), preferably -with the living animals enclosed, will also enhance the general -appearance and interest of the aquarium. - -In making preparations previous to the introduction of animal life, due -regard should be paid to the peculiar requirements of the creatures it -is intended to obtain. We have already referred to the advisability of -arranging the bed of the tank in such a manner that the water may vary -considerably in depth, so that both deep and shallow water may be found -by the animals as required, and to the provision of dark holes for -crustaceans and other creatures that shun the light. Very fine sand -should be provided for shrimps, prawns, and other animals that like to -lie on it; and this sand must be deep in places if it is intended to -introduce any of the burrowing molluscs and marine worms. - -The water used may be taken from the sea or be artificially prepared. -The former is certainly to be preferred whenever it can be conveniently -obtained, and at the present time few will find much difficulty in -securing a supply, for not only are we favoured with the means of -obtaining any desired quantity by rail at a cheap rate from almost any -seaport, but there are companies in various ports who undertake the -supply of sea water to any part of the kingdom. If the water is to be -conveyed from the coast without the aid of the regular dealers in this -commodity, great care must be taken to see that the barrel or other -receptacle used for the purpose is perfectly clean. Nothing is more -convenient than an ordinary beer or wine barrel, but it should be -previously cleansed by filling it several times with water--not -necessarily sea water--and allowing each refill to remain in it some -time before emptying. This must be repeated as long as the water shows -the slightest colouration after standing for some time in the barrel. - -Should any difficulty arise in the way of getting the salt water direct -from the sea, it may be made artificially by dissolving 'sea salt' in -the proper proportion of fresh water, or even by purchasing the -different salts contained in the sea separately, and then adding them to -fresh water in proportionate quantities. - -The composition of sea water is as follows:-- - - Water 96.47 per cent. - Sodium chloride 2.70 " - Magnesium chloride .36 " - Magnesium sulphate (Epsom salts) .23 " - Calcium sulphate .14 " - Potassium chloride .07 " - Traces of other substances .03 " - 100.00 - -and it will be seen from this table that artificial sea water may be -made by adding about three and a half pounds of sea salt, obtained from -the sea by the simple process of evaporation, to every ninety-six and a -half pounds of fresh water used. In making it there may be some -difficulty in determining the weight of the large volume of water -required to fill an aquarium of moderate dimensions, but this will -probably disappear if it be remembered that one gallon of water weighs -just ten pounds, and, therefore, one pint weighs twenty ounces. - -If the sea salt cannot be readily obtained, the following mixture may be -made, the different salts being purchased separately:-- - - Water 96-1/2 lbs. - Sodium chloride (common salt) 43-1/4 ozs. - Magnesium chloride 5-3/4 " - Epsom salts 3-3/4 " - Powdered gypsum (calcium sulphate) 2-1/4 " - -Although in this mixture the substances contained in the sea in very -small quantities have been entirely omitted, yet it will answer its -purpose apparently as well as the artificial sea water prepared from the -true sea salt, and may therefore be used whenever neither sea salt nor -the natural sea water is procurable. - -Assuming, now, that the aquarium has been filled with sea water, it -remains to introduce the animal and vegetable life for which it is -intended; and here it will be necessary to say something with regard to -the amount of life that may be safely installed, and the main conditions -that determine the proportion in which the animal and vegetable life -should be present in order to insure the greatest success. - -Concerning the first of these we must caution the reader against the -common error of overcrowding the aquarium with animals. It must be -remembered that almost all marine animals obtain the oxygen gas required -for purposes of respiration from the air dissolved in the water. Now, -atmospheric air is only very slightly soluble in water, and hence we can -never have an abundant supply in the water of an aquarium at any one -time. If a number of animals be placed in any ordinary indoor aquarium, -they very soon use up the dissolved oxygen; and, if no means have been -taken to replace the loss, the animals die, and their dead bodies soon -begin to putrefy and saturate the water with the poisonous products of -decomposition. - -It is probably well known to the reader that a large proportion of the -oxygen absorbed by the respiratory organs of animals is converted by -combination of carbon into carbonic acid gas within their bodies, and -that this gas is given back into the water where it dissolves, thus -taking the place of the oxygen used in its formation. - -If, then, an aquarium of any kind is to be a success, some means must be -taken to keep the water constantly supplied with fresh oxygen quite as -rapidly as it is consumed, and this can be done satisfactorily by the -introduction of a proportionate quantity of suitable living weeds, -providing there is not too much animal life present. - -The majority of living plants require carbonic acid gas as a food, and, -under the influence of light, decompose this gas, liberating the oxygen -it contained. This is true of many of our common sea-weeds, and thus it -is possible to establish in a salt-water aquarium such a balance of -animal and vegetable life that the water is maintained in its normal -condition, the carbonic acid gas being absorbed by the plants as fast as -it is excreted by animals, and oxygen supplied by the plants as rapidly -as it is consumed by the animals. - -This condition, however, is more difficult to obtain in a salt-water -aquarium than in one containing fresh-water life, partly because, -generally speaking, the sea-weeds do not supply oxygen to the water as -rapidly as do the plants of our ponds and streams, and partly because of -the difficulties attending the successful growth of sea-weeds in -artificial aquaria. Thus it is usually necessary to adopt some means of -mechanically aerating the water; but, for the present, we shall consider -the sea-weeds only, leaving the mechanical methods of aerating the water -for a later portion of this chapter. - -In the first place, let us advise the amateur to confine his attention -to the smaller species of weeds that are commonly found in small and -shallow rock pools, for the successful growth of the larger purple and -olive weeds will probably be beyond his power, even though his tank be -one of considerable capacity. The best plan is that we have already -suggested--namely, to chip off small pieces of rock with tufts of weed -attached, and to fix them amongst the rockery of the aquarium, being -careful to place those that grew in shallow water with full exposure to -the light, and those which occupied sheltered and shady places in the -rock pool, respectively, in similar situations in the artificial pool. - -For the purposes of aeration we have to rely principally on the bright -green weeds, and preference should be given to any of these that -exhibit, in their natural habitat, a multitude of minute air-bubbles on -the surface of their fronds, for the bubbles consist principally of -oxygen that is being liberated by the plant, and denote that the species -in question are those that are most valuable for maintaining the desired -condition of the water in an aquarium. - -Any small sea-weed may be tried at first, but experience will soon show -that some are much more easily kept alive than others. In this -experimental stage, however, a constant watch should be maintained for -the purpose of detecting signs of decay in the marine garden. A plant -should always be removed as soon as it presents any change from the -natural colour, or exhibits the smallest amount of slimy growths on the -surface, for decomposing plants, as well as decaying animals, will soon -convert an aquarium into a vessel of putrid and poisonous water. - -It seems almost unnecessary to name a selection of sea-weeds for small -aquaria, seeing that our rock pools produce so many extremely beautiful -species, most of which may be successfully kept alive in a well-managed -tank; but the common Sea Grass (_Enteromorpha compressa_), and the Sea -Lettuce (_Ulva latissima_), also known locally as the Green Laver or -Sloke, are particularly useful for the aeration of the water; while the -Common Coralline (_Corallina officinalis_), the Dulse (_Schizymenia -edulis_), the Peacock's tail (Padina pavonia), the Irish or Carrageen -Moss (_Chondrus crispus_), _Callithamnion_, _Griffithsia setacea_, -_Plocamium plumosium_, _Rhodymenia palmata_, _Rhodophyllis bifida_, and -_Ceramium rubrum_ are all beautiful plants that ought to give no trouble -to the aquarium-keeper. - -It is not advisable to introduce animal life into the aquarium -immediately it is filled, on account of the possibility of the water -being contaminated by contact with the cement that has been used to make -it water-tight. It is safer to allow the first water to stand for a few -weeks, the weeds and all other objects being _in situ_, and the -necessary means employed for perfect aeration during this interval, and -then, immediately before the animals are placed in their new home, to -syphon off the whole of the water, and refill with a fresh supply. - -In the selection of animals due regard should be paid to two important -points--first, the danger of overcrowding, and, secondly, the -destructive habits of some of the more predaceous species. - -No more than two or three animals should, as a rule, be reckoned for -each gallon of water; and the proportion of animals should be even less -than this when any of them are of considerable size. - -As regards the destructive species, these are intended to include both -those that are voracious vegetable feeders and also those whose habit it -is to kill and prey on other creatures. - -It must be understood that the weeds are to serve two distinct -purposes:--They are to supply at least some of the oxygen required for -the respiration of the animal inmates, and also to serve as food for -them. Some marine fishes and molluscs feed on the fronds of the weeds, -and among these the common periwinkle may be mentioned as one of the -most voracious. If many such animals are housed in the aquarium, it will -be necessary to replace at intervals those species of weeds that suffer -most from their ravages. The zoospores thrown off by the weeds, -particularly in the autumn, are also valuable as food for some of the -animals. - -Notwithstanding the destructive character of the periwinkle just -referred to, it has one redeeming feature, for it is certainly useful in -the aquarium as a scavenger, as it greedily devours the low forms of -vegetable life that cover the glass and rocks, thus helping to keep them -clean; and the same is true of the common limpet and other creeping -molluscs. Some of these are even more to be valued on account of their -partiality for _decaying_ vegetable matter, by devouring which they -reduce the amount of the products of decomposition passing into the -water. - -Other details concerning the selection of animal and vegetable life for -the indoor aquarium must be left to the discretion and experience of the -keeper, for it is impossible by written instructions and advice to cover -all the various sources of loss and trouble that may from time to time -arise. If, however, the general hints for the management of the marine -aquarium here given be faithfully followed, there ought to be no further -losses than must accrue from the injudicious selection of animal -species, and these will decrease as experience has been acquired -respecting the habits of the creatures introduced. - -We must now pass on to matters pertaining to the maintenance of the -healthy condition of an aquarium which, we will suppose, has been -established with due regard to scientific principles. Under this head we -shall consider, (1) the aeration of the water, (2) the repair of loss -due to evaporation, and (3) the regulation of light and temperature. - -It has already been shown that the marine aquarium can hardly be -maintained in a satisfactory condition as regards its air supply by -leaving the aeration of the water entirely to the action of plant life; -and herein this form of aquarium differs from that employed for the -animal and vegetable life derived from ponds and streams. Fresh-water -weeds develop and multiply with such rapidity, and are such ready -generators of oxygen gas that it is a very easy matter to establish a -fresh-water aquarium that will remain in good condition for years with -but little attention; it is therefore important that we should point out -the difference in treatment necessary to those of our readers who are -already acquainted with the comparative ease with which the fresh-water -aquarium may be kept in good order, lest they expect the same -self-aerating condition in the marine tank. - -It is never a good plan to leave the renovation of the water of the -aquarium until there are visible signs within that something is going -wrong. It is true that an unsatisfactory condition of the water, -revealed by a slight taint in the odour, or a general turbidity, or the -formation of a slight scum on the surface, may sometimes be rectified by -the prompt application of some method of artificial aeration, but the -aim of the aquarium-keeper should be not the rectification of -unsatisfactory conditions, but the establishment of such a method of -aeration that the unsatisfactory condition becomes an impossibility. We -do not wish to discourage anyone who has the slightest desire to start a -marine aquarium. Our aim is to point out any difficulties that lie in -the way in order that the aquarium may be a success; and thus, having -stated that the difficulties attending it are somewhat greater than -those connected with the management of a fresh-water aquarium, we should -like to add that these practically disappear when one is prepared to -devote a short time at regular intervals in order to see that the -process of aeration is properly carried out. - -Some recommend the occasional injection of air by a syringe as one means -of aerating the water; but, although this may be all very well as a -_temporary_ purifier of the slightly tainted aquarium, it is hardly -suitable as a means of maintaining a good, healthy condition. It must be -remembered that oxygen gas--the gas of the atmosphere so essential to -animal life--is only very slightly soluble in water. By this we mean not -only that water dissolves oxygen very slowly, but also that it can never -hold a large supply of the gas at any one time. This being the case, it -is clear that the use of a syringe for a short time, though it -discharges an enormous total volume of air into the water, will result -in the actual solution of only a small quantity. No method of aeration -is perfect that allows the admission of air for a short time only at -comparatively long intervals; the most perfect system is that in which -air is slowly but _continuously_ passed into solution. - -Since air is slightly soluble in water, it is clear that it must be -continuously passing into any body of water that has its surface freely -exposed to it; hence a wide and shallow aquarium is much more likely to -keep in good order than one that is narrower and deeper. But, with -marine aquaria, the simple absorption from the air at the surface is not -in itself sufficient, as a rule, to maintain a healthy condition. Yet it -will be advisable to remember this matter when constructing a tank for -marine life. - -One of the prettiest, and certainly one of the most effectual, methods -of supplying air to an aquarium is by means of a small fountain with a -very fine spray. The water need seldom be changed, but the fountain may -be fed by water from the aquarium, and as the fine spray passes through -the air it will absorb oxygen and carry it in solution to the tank. - -The accompanying diagram illustrates the manner in which this can be -accomplished. The aquarium (A) is supplied with an outlet (O) about an -inch from the top by means of which the water is prevented from -overflowing, and the outlet pipe leads to a vessel (V) of considerable -capacity which, for the sake of convenience and appearance, may be -concealed beneath the table on which the aquarium stands. Some feet -above the level of the aquarium is another vessel (C), supported on a -shelf, having about the same capacity as V, and supplied with a small -compo pipe that passes down into the aquarium, and then, hidden as much -as possible by the rockery, terminates in a very fine jet just above the -level of the water in the centre. The upper vessel should also be -provided at the top with a loose covering of muslin to serve as a -strainer, and this should be replaced at intervals as it becomes clogged -with sedimentary matter. - -In order that this arrangement may give perfect satisfaction the two -vessels (C and V) must each be of at least half the capacity of the -aquarium itself, and the total quantity of salt water sufficient to fill -the aquarium together with one of them. It should also be remembered -that since the pressure of water depends not on its quantity, but on its -height measured perpendicularly, it follows that the height to which the -fountain will play is determined by the height of the vessel C above the -level of the jet. - - [Illustration: FIG. 38.--METHOD OF AERATING THE WATER OF AN AQUARIUM - A, aquarium with fountain; C, cistern to supply the fountain; - O, pipe for overflow; V, vessel for overflow] - -Let us now suppose that the aquarium and the upper vessel have both been -filled with sea water. The fine jet from the pipe plays into the air and -returns with a supply of oxygen to the aquarium, while the excess above -the level of O passes into the concealed vessel below the table. If the -two vessels are as large as we recommend, and the jet a very fine one, -the fountain may continue to play for hours before C is empty, the -animals of the tank being favoured all this time with a continuous -supply of air. And when the supply from above is exhausted, the contents -of the bottom vessel are transferred to the top one, and at the same -time so effectually strained by the layer of muslin that no sedimentary -matter passes down to choke the fine jet of the fountain. One great -advantage this method possesses is that the living creatures derive the -benefit of a much larger quantity of water than the aquarium alone could -contain; and thus, apart from the aerating effects of the fountain, the -result is the same as if a much larger tank were employed. - -In our next illustration (fig. 39) we give a modified arrangement based -on the same principle which may commend itself by preference to some of -our readers. Here the supply pipe to the fountain passes through a hole -in the bottom of the aquarium instead of into the top, and the outlet -pipe is bent downward within so as to form a syphon. - -Those who are acquainted with the principle of the syphon will -understand at once the working of such an arrangement as this. Let us -suppose the vessel _c_ to be full of water, and the fountain started, -while the water in the aquarium stands no higher than the level _l_. The -water slowly rises until the level _h_ of the bend of the outlet tube -has been reached, and during the whole of this time no water escapes -through the exit. As soon, however, as the latter level has been -attained, the water flows away into the lower vessel, into which it -continues to run until the lower level is reached, and then the outflow -ceases, not to commence again until the fountain causes the water to -rise to the upper level. - -From what has been said the reader will see that the total quantity of -water required in this instance need not exceed the capacity of the -aquarium; also that each of the vessels connected with water supply and -waste should have a capacity equivalent to the volume of water contained -in the aquarium between the two levels _h_ and _l_. - -The alternate rising and falling of the water produced in the manner -just described represents in miniature the flow and ebb of the tides, -but perhaps this is in itself of no great advantage in the aquarium -except from the fact that it allows those creatures that prefer to be -occasionally out of the water for a time a better opportunity of -indulging in such a habit. And further, with regard to both the -arrangements for aeration above described, it should be noted that -earthenware vessels are much to be preferred to those made of metal for -the holding of sea water, since the dissolved salts corrode metallic -substances rather rapidly, and often produce, by their chemical action, -soluble products that render the water more or less poisonous. - - [Illustration: FIG. 39.--AQUARIUM FITTED WITH APPARATUS FOR PERIODIC - OUTFLOW] - -Other methods of aerating the water of aquaria are practised, but these, -as a rule, are only practicable in the case of the large tanks of public -aquaria and biological laboratories, as the mechanical appliances -necessary to carry them out successfully are beyond the means of an -ordinary amateur. - -In such large tanks as those referred to it is common to force a fine -jet of air into the water by machinery. Sometimes this air is driven -downward from a jet just below the surface, and with such force that a -multitude of minute bubbles penetrate to a considerable depth before -they commence to rise, but in others the air is made to enter at the -bottom and must therefore pass right through the water. - -Of course the amateur aquarium-keeper may carry out this method of -aeration with every hope of success providing he has some self-acting -apparatus for the purpose, or can depend on being able himself to attend -to a non-automatic arrangement at fairly regular intervals, always -remembering that a single day's neglect, especially in the case of a -small tank with a proportionately large amount of animal life, may lead -to a loss of valuable specimens. - -We have already mentioned the use of a syringe as a means by which an -aquarium may be temporarily restored to a satisfactory condition -providing it has not been neglected too long, and some recommend forcing -air, or, still better, pure oxygen gas, from an india-rubber bag into -the water. We have used, for the same purpose, a stream of oxygen from a -steel cylinder of the compressed gas with very satisfactory results; and -since oxygen may be now obtained, ready compressed, at a very low -price--about twopence a cubic foot--there is much to be said in favour -of this method as an auxiliary in the hands of the owner of a small -tank, though we hardly recommend it as a prime means of aeration to take -the place of the fountain. - -In any case, where a stream of air or oxygen is employed, an exceedingly -fine jet should be used, in order that the expelled gas may take the -form of a stream of minute bubbles; for, as previously stated, the water -can absorb the gas only very slowly, so that there must necessarily be a -considerable waste when the gas issues rapidly. Further, the smaller the -bubbles passing through the water, the greater is the total surface of -gas in contact with the liquid, the volume of the supply being the same, -and hence the more effectually will the solution of the gas proceed. -Again, another advantage of the fine stream of minute bubbles lies in -the fact that the smaller these bubbles are the more slowly they rise to -the surface of the water, and thus the longer is the time in which the -gas may be absorbed during its ascent. - -A fine jet, well suited to the purpose here defined, may be made very -easily by holding the middle of a piece of glass tubing in a gas flame -until it is _very_ soft, and then, immediately on removing it, pulling -it out rather quickly. A slight cut made with a small triangular file -will then enable the operator to sever the tube at any desired point. - -Yet another method of maintaining the air supply of aquaria is adopted -in the case of some of the large tanks of public aquaria and biological -laboratories situated close to the sea, and this consists in renewing -the water at every high tide by means of pumps. - -It must not be supposed that an indoor aquarium, even when well -established, and supplied with the best possible system of aeration, -requires no further care and attention. In the first place there is a -continual loss of water by evaporation, especially in warm and dry -weather, and this must be rectified occasionally. Now, when water -containing salts in solution evaporates, the water passing away into the -air is perfectly free from the saline matter, and thus the percentage of -salt in the residue becomes higher than before. It is evident, -therefore, that the loss by evaporation in a marine aquarium must be -replaced by the addition of _fresh_ water, which should either be -distilled, or from the domestic supply, providing it is soft and -moderately free from dissolved material. - -But the question may be asked, 'Do not the marine animals and plants -utilise a certain amount of the saline matter contained in the salt -water?' The answer to this is certainly in the affirmative, for all -sea-weeds require and abstract small proportions of certain salts, the -nature of which varies considerably in the case of different species; -and, further, all the shelled crustaceans and molluscs require the salts -of lime for the development of their external coverings, and fishes for -the growth of their bony skeletons. Hence the above suggestion as to the -replenishment of loss by evaporation with pure water is not perfectly -satisfactory. It will answer quite satisfactorily, however, providing -the sea water is _occasionally_ changed for an entirely new supply. -Again, since carbonate of lime is removed from sea water more than any -other salt, being such an essential constituent of both the external and -internal skeletons of so many marine animals, as well as of the -calcareous framework of the coralline weeds, we suggest that the -aquarium may always contain a clean piece of some variety of carbonate -of lime, such as chalk, limestone, or marble, which will slowly dissolve -and replace that which has been absorbed. - -Water is rendered denser, and consequently more buoyant, by the presence -of dissolved salts; and, since the density increases with the proportion -of dissolved material, we are enabled to determine the degree of -salinity by finding the density of the solution. We can apply this -principle to the aquarium, as a means of determining whether the water -contains the correct amount of sea salt, also for testing any artificial -salt water that has been prepared for the aquarium. - -Probably some of our readers are acquainted with some form of -hydrometer--an instrument used for finding the density of any liquid; -but we will describe a simple substitute that may be of use to the owner -of a marine aquarium, especially if the salt water for the same is -artificially prepared. Melt a little bees-wax, and mix it with fine, -clean sand. Then, remembering that the wax is lighter than water, and -consequently floats, while sand is considerably heavier, and sinks, -adjust the above mixture until a solid ball of it is just heavy enough -to sink _very slowly_ in sea water. Now make two such balls, and then -cover one of them with a light coating of pure wax. We have now two -balls, one of which will float in sea water, and the other sink, and -these may be used at any time to test the density of the water in, or -prepared for, the aquarium. If the water is only a little too salt, both -balls will float; while, if not sufficiently rich in saline matter, both -will sink. - -We must conclude this chapter by making a few remarks on the important -matter of the regulation of light and temperature. Direct sunlight -should always be avoided, except for short and occasional intervals, not -only because it is liable to raise the temperature to a higher degree -than is suitable for the inmates of the aquarium, but also because an -excess of light and heat tends to produce a rapid decomposition of -organic matter, and a consequent putrid condition of the water, and this -dangerous state is most likely to occur when both light and temperature -are high at the same time. - -The water should always be cold; and as it is not always easy to -estimate the temperature, even approximately, by the sensation produced -on immersing the fingers, it is a good plan to have a small thermometer -always at hand, or placed permanently in the aquarium. In the summer -time the water should be kept down to fifty-five degrees or lower, and -in winter should never be allowed to cool much below forty. There may be -some difficulty in maintaining a temperature sufficiently low in summer, -but a small piece of ice thrown in occasionally to replace the loss due -to evaporation, especially on very hot days, will help to keep it down. - - - - - CHAPTER V - - _THE PRESERVATION OF MARINE OBJECTS_ - - -The sea-side naturalist, in the course of his ramblings and searchings -on the coast, will certainly come across many objects, dead or alive, -that he will desire to set aside for future study or identification in -his leisure moments at home. Some of these will be required for -temporary purposes only, while, most probably, a large proportion will -be retained permanently for the establishment of a private museum, that -shall serve not only as a pleasant reminder of the many enjoyable hours -spent on the shore, but also as a means of reference for the study of -the classification of natural objects and of their distribution and -habitats. - -We will first deal with those specimens that are required for temporary -purposes only--those of which the collector desires to study the general -characters, as well as, perhaps, something of the internal structure; -but before doing so we cannot refrain from impressing on the reader the -advisability of learning as much as possible of the external features -and mode of growth of the different living creatures while still alive, -for it must be remembered that it is impossible to preserve many of them -without more or less destruction of their natural colouring and -distortion of their characteristic forms. - -In those cases where it is possible to keep the creatures alive for a -short time only, it is a good plan to make notes of their movements and -all observed changes in form, and their methods of feeding, and also to -illustrate these notes by sketches drawn from life. This may seem quite -an unnecessary procedure to many beginners in the study of natural -objects, and may even, as far as the sketches are concerned, present -difficulties that at first appear to be insurmountable; but the power to -sketch from nature will surely be acquired to a greater or less degree -by constant practice, and illustrated notes prepared for the purpose we -suggest will undoubtedly be of great value to the student. Further, -though it may often be necessary to set specimens aside in a -preservative fluid until one has the leisure to examine their structure, -it should always be remembered that they never improve by keeping, also -that they are rarely in such good condition for dissection after -saturation with the preservative as when perfectly fresh. - -One of the most convenient preservatives for general use is undoubtedly -methylated spirit. This is alcohol that has been adulterated in order to -render it undrinkable, so that it may be sold free from duty for use in -the various arts and manufactures without any danger of its being -employed for the concoction of beverages. It may be used just as -purchased--that is, in its strongest condition--for many purposes, but -in this state it has a powerful affinity for water, and will rapidly -abstract water from animal and vegetable objects, causing the softer -ones to become hard, shrunken, and shrivelled, often to such an extent -that they are almost beyond recognition. - -By diluting the spirit, however, we satisfy to a great extent its -affinity for water, and thus prevent, or, at least, reduce the action -just mentioned. A mixture of equal quantities of spirit and water is -quite strong enough. Unfortunately the common methylated spirit of the -shops produces a fine white precipitate, that gives the whole mass a -milky appearance, when it is diluted. This is due to the presence of -mineral naphtha, which is added in a certain fixed proportion in -accordance with the Government regulations. But it _is_ possible, by -special application, to obtain the 'non-mineralised' or 'ordinary' -methylated spirit of former years, though not in small quantities, and -this liquid dissolves in water without the formation of a precipitate. -It should be noted, however, that the use of the spirit as a -preservative is in no way interfered with by the presence of the mineral -naphtha, the only disadvantage of this impurity lying in the fact that -the milkiness consequent on dilution prevents the objects in a specimen -jar from being observed without removal. - -We have just referred to the hardening action of strong spirit as a -disadvantage, and so it is when it is required to preserve soft -structures with as little as possible of change in general form and -appearance; but there are times when it becomes necessary to harden -these soft structures in order that sections may be made for the purpose -of examining internal structure with or without the aid of the -microscope, and for such purposes strong spirit is one of the best -hardening agents that can be employed. - -Formaldehyde is another very good preservative. It is a colourless -liquid, and should be considerably diluted for use, a two per cent. -solution being quite strong enough for all ordinary purposes. It -possesses some distinct advantages as compared with spirit. In the first -place, it does not destroy the natural colours of objects to the extent -that spirit does; and, although a hardening agent as well as a -preservative, it does not harden soft structures by the extraction of -the water they contain, and therefore does not cause them to become -shrivelled or otherwise distorted. It will also occur to the reader -that, since a small bulk of formaline represents a large volume of the -diluted preservative, it is very conveniently stored, and a very small -bottle of it taken for outdoor work may, on dilution with water, be made -to yield all that is required for the preservation of the takings of a -successful day, or even of a longer period. Formaldehyde is usually sold -in solution of about forty per cent. strength, and for the preparation -of a two per cent. solution it will be found convenient to provide a -glass measure graduated either into cubic centimetres or fluid ounces -and drams. One hundred volumes of the original solution contain forty of -pure formaldehyde, and if water be added to make this up to two thousand -volumes, a two per cent. solution is obtained. Thus, one hundred cubic -centimetres of the original solution is sufficient to prepare two litres -(three and a half pints) of suitable preservative. - -A very good preservative liquid may be made by dissolving two ounces of -common salt, one ounce of alum, and two or three grains of corrosive -sublimate (a deadly poison) in one quart of water, and then, after -allowing all sedimentary matter to settle to the bottom, decanting off -the clear solution. This mixture is known as _Goadby's fluid_, and is -well adapted for the preservation of both animal and vegetable -structures. It does not cause any undue contraction of soft tissues, -and, as a rule, does not destroy the natural colours of the objects kept -in it. - -Glycerine is valuable as a preservative for both animal and vegetable -objects, and especially for the soft-bodied marine animals that form -such a large percentage of the fauna of our shores. It maintains the -tissues in a soft condition, and preserves the natural tints as well as -any liquid. - -An inexpensive preservative may also be made by dissolving chloride of -zinc--about one ounce to the pint of water. This is considered by some -to be one of the best fluids for keeping animal structures in good -condition. - -Now, although the different fluids here mentioned are described in -connection with the _temporary_ preservation of natural objects, it must -be remembered that they are equally adapted for the permanent -preservation of the animals and plants that are to figure in the museum -of the sea-side naturalist; and, although some marine objects may be -preserved in a dry state in a manner to be hereafter described, yet -there are many species of animals, and also some plants, that can be -satisfactorily preserved only by immersion in a suitable fluid. - -This method may be applied to all soft-bodied animals, such as anemones, -jelly-fishes, marine worms, shell-less molluscs (sea slugs, cephalopods, -&c.), the soft parts of shelled molluscs, fishes, &c.; and most sponges -retain their natural appearance much better in a preservative fluid than -in a dry condition. Many sea-weeds also, which are practically destroyed -by the most careful drying process, are most perfectly preserved in -fluid. - -But the puzzled amateur will probably be inclined to ask: 'Which is the -best preservative liquid for this or that specimen?' No satisfactory -general rule can be given in answer to such a question, and a great deal -will have to be determined by his own experiments and observations. -Whenever he has two or three specimens of the same object, as many -different fluids should be employed, and the results compared and noted. -In this way a very great deal of useful information will be obtained and -by the best possible means. However, it may be mentioned that all the -fluids alluded to above may be safely used for almost every animal or -vegetable specimen with the following reservations: strong spirit should -not be employed for _any_ very soft animal, nor should it be used for -delicate green plants, since it will dissolve out the green colouring -matter (_chlorophyll_), leaving them white or almost colourless. -Further, the greatest care should be exercised in dealing with sea -anemones and jelly-fishes. If spirit is used for preserving these -creatures, it should be very dilute, at least at first, but may with -advantage be increased in strength afterwards, though this should be -done gradually. - -Whatever be the preservative used, it is sure to be more or less charged -with sedimentary and coloured matter extracted from the object immersed -in it; hence, if the specimen concerned is to form part of a museum -collection, it will be necessary to transfer it to a fresh solution -after a time, and a second, and even further changes may be necessary -before the object ceases to discolour the fluid or render it turbid. - -Considerable difficulty will sometimes be found in the attempts to -preserve a soft-bodied animal in its natural attitude. Thus, when a sea -anemone is removed from its native element, it generally withdraws its -tentacles, and, contracting the upper part of its cylindrical body, -entirely conceals these appendages, together with the mouth they -surround; and a mollusc similarly treated will generally pull itself -together within its shell, leaving little or no trace of the living body -inhabiting the lifeless case. Then, if these animals are transferred to -any fluid other than sea water, or placed anywhere under unnatural -conditions, they usually remain in their closed or unexpanded form. -Thus, almost every attempt to kill them for preservation deprives them -of just the characteristics they should retain as museum specimens. - -Some such animals may be dealt with satisfactorily as follows: Transfer -them to a vessel of fresh sea water, and leave them perfectly -undisturbed until they assume the desired form or attitude. Then add a -_solution_ of corrosive sublimate very gradually--a drop or two at -intervals of some minutes. In this way the bodies of anemones may be -obtained ready for preservation with expanded tentacles, tube-secreting -worms with their heads and slender processes protruding from their limy -or sandy cases, molluscs with their 'feet' or their mantles and gills -protruding from their shells, and barnacles with their plume-like -appendages projecting beyond the opening of their conical shells. - -The specimens thus prepared may be placed at first in very dilute -spirit, and then, after a time, finally stored in a stronger solution of -spirit in water; or they may be transferred to one of the other -preservative solutions previously mentioned. - -All specimens permanently preserved in fluid for a museum should be -placed in jars, bottles, or tubes of suitable size, each vessel -containing, as a rule, only one. Where expense is no object, stoppered -jars made expressly for biological and anatomical specimens may be used -for all but the smallest objects; or, failing this, ordinary -wide-mouthed bottles of white glass, fitted with good corks or glass -stoppers. - -For very small specimens nothing is more suitable than glass tubes, but -it must be remembered that wherever corks are used, even if they are of -the best quality procurable, it will be necessary to look over the -specimens occasionally to see if the preserving fluid has disappeared to -any extent either by leakage or evaporation; for such loss is always -liable to occur, although it may be very slow, and especially when -methylated spirit is the liquid employed. - - [Illustration: FIG. 40.--JARS FOR PRESERVING ANATOMICAL AND BIOLOGICAL - SPECIMENS] - -The writer has preserved many hundreds of small marine and other objects -in glass tubes of dilute spirit that have been hermetically sealed, thus -rendering the slightest loss absolutely impossible, while the perfect -exclusion of air prevents the development of fungoid growths that -sometimes make their appearance in imperfectly preserved specimens. The -making and closing of such tubes, though a more or less difficult -operation at first to those who have had no previous experience in -glass-working, become exceedingly simple after a little practice; and -believing it probable that many of our readers would like to try their -hand at this most perfect method of preserving and protecting small -objects, we will give a description of the manner in which it is done. - -The apparatus and materials required for this work are:--Lengths of -'soft' glass tubing, varying from about one quarter to a little over -half an inch in internal diameter; a supply of diluted spirit--about -half spirit and half water; a Herapath blowpipe, preferably with -foot-bellows; and a small triangular file. - -The glass tubing may be cut into convenient lengths by giving a single -sharp stroke with the file, and then pulling it apart with, at the same -time, a slight bending _from_ the cut made. - - [Illustration: FIG. 41.--SHOWING THE DIFFERENT STAGES IN THE MAKING OF - A SMALL SPECIMEN TUBE] - -Cut a piece of tubing about eight or nine inches long, heat it in the -blowpipe flame, turning it round and round all the time, until it is -quite soft, then remove it from the flame and immediately pull it out -_slowly_ until the diameter in the middle is reduced to about a -sixteenth of an inch (fig. 41, 2). Make a slight scratch with the file -at the narrowest part, and divide the tube at this point (fig. 41, 3). -Now heat one of these pieces of tubing as before just at the point where -the diameter of the drawn part begins to decrease; and, when very soft, -pull it out rather quickly while it is _still in the flame_. The part -pulled now becomes completely separated, and the tube is closed, but -pointed. Continue to heat the closed end, directing the flame to the -point rather than to the sides, until the melted glass forms a rather -thick and flattened end; and then, immediately on removing it from the -flame, blow gently into the open end until the melted glass is nicely -rounded like the bottom of a test-tube (fig. 41, 4). When the tube is -cold, the specimen that it is to contain, and which has already been -stored for a time in dilute spirit, is dropped into it. The tube is now -heated about an inch above the top of the specimen, drawn out as shown -in fig. 41, 5, and again allowed to cool. When cold, the fresh spirit is -poured into the open end of the tube, but the middle part is so narrow -that the spirit will not run down freely. If, however, suction be -applied to the open end, air from the bottom will bubble through the -spirit, and then, on the cessation of the suction, the spirit will pass -down to take the place of the air that was withdrawn. This may be -repeated if necessary to entirely cover the specimen with the fluid. Any -excess of spirit is then thrown from the upper part of the tube, and the -latter cut off. Nothing is now left but to close the tube hermetically. -This is done by heating the lower part of the narrow neck, and then -drawing it out _in the flame_, taking great care that the tube is -withdrawn from the flame the moment it is closed. The tube must also be -kept in an upright position until it has cooled. The appearance of the -finished tube is shown in fig. 41, 6. - - [Illustration: FIG. 42.--SMALL SPECIMEN TUBE MOUNTED ON A CARD] - -All preserved specimens should have a label attached on which is written -the name of the specimen, the class and order to which it belongs, the -locality in which it was found, together with any brief remarks that the -owner desires to remember concerning its habits &c. - -The bottles or tubes that are too small to have a label attached to them -in the ordinary way may be mounted on a card, as represented in fig. 42, -and the desired particulars then written on the card. - -When soft or delicate specimens are preserved in a bottle of fluid they -frequently require some kind of support to keep them in proper form and -to display them better for observation. Perhaps the best way to support -them is to fasten them to a very thin plate of mica of suitable size by -means of a needle and very fine thread. The mica is so transparent that -it is invisible in the fluid, and the few stitches are also hardly -perceptible, thus making it appear as if the specimen floats freely in -the fluid. - -We will now pass on to consider those objects of the shore that are -usually preserved in a dry condition, commencing with - - - STARFISHES AND SEA URCHINS - -Starfishes are commonly preserved by simply allowing them to dry in an -airy place, with or without direct exposure to the sun's rays, and this -method is fairly satisfactory when the drying proceeds rapidly; but care -should be taken to maintain the natural roughness of the exterior as -well as to have the numerous suckers of the under surface as prominent -as possible. If the starfish is simply laid out on some surface to dry, -the side on which it rests is often more or less flattened by the weight -of the specimen itself, which therefore becomes adapted for the future -examination of one surface only; but a better result, as regards both -the rapidity of drying and the after appearance of the specimen, may be -obtained by suspending it on a piece of fine net or by threads. A still -better plan is to put the dead starfish into _strong_ spirit, which will -rapidly extract the greater part of the moisture that its body -contained. After allowing it to remain in this for a day or two to -harden it, put it out to dry as before mentioned. The spirit, being very -volatile, will soon evaporate, so that the specimen will shortly be -ready for storing away. - -It is most important to observe that dried specimens--not starfishes -only, but all animal and vegetable objects--should never be placed in -the cabinet or other store-case until _perfectly_ dry, for a very small -amount of moisture left in them will often encourage the development of -moulds, not only on themselves, but on other specimens stored with them. - -Very small and delicate starfishes, when preserved in a dry condition, -may be protected from injury by fastening them on a card by means of a -little gum, or by keeping them permanently stored on cotton wool in -glass-topped boxes. - -Sea urchins, or sea eggs, as they are commonly called, may be preserved -exactly in the same way as starfishes, though it is more essential in -the case of these to soak them in strong spirit previous to drying, -otherwise the soft animal matter within the shell will decompose before -the drying is complete. Here, however, it is possible to remove the -whole interior with the aid of a piece of bent wire, and to thoroughly -clean the inner surface of the shell before drying it. - -Some of the shells should be preserved with the spines all intact, and -others with these removed in order to show the arrangement of the -plates which compose the shell, as well as the perforations, and the -rounded processes to which the spines are articulated. - -The majority of sea urchins are provided with a most complicated and -beautiful arrangement of teeth which are well worthy of study. These -should be removed from a moderately large specimen, the soft surrounding -structures carefully dissected away, and then cleaned by means of an old -tooth-brush without disarranging them. - -It will be found that dried sea urchins will require care when preserved -with spines attached, for these appendages are usually very brittle and -are easily dislocated at their bases where they are united to the shell -by ball-and-socket joints. - -It may be mentioned here that corrosive sublimate is very valuable for -preventing the development of mould on the surfaces of starfishes, sea -urchins, and museum specimens generally. It is best supplied in the form -of an alcoholic solution made by dissolving a few grains in about half a -pint of methylated spirit; the advantage of this over an aqueous -solution being the rapidity with which it dries. In most cases it is -simply necessary to apply the solution to the object by means of a soft -brush, but, as regards starfishes and urchins it is far better to -dissolve a few grains of the corrosive sublimate in the spirit in which -the objects are placed previous to drying. - - - CRUSTACEANS - -The preservation of crustaceans by the dry method often requires some -care and demands a certain amount of time; but the process is never -really difficult, and the satisfaction of having produced a good -specimen for a permanent collection well repays one for the trouble -taken and time spent. - -Some of our crustaceans are only partially protected by a firm outer -covering, and almost every attempt to preserve these as dry objects -results in such a shrivelling of the soft tissues that the natural -appearance is quite destroyed. This is the case with some of the -barnacles, and the abdominal portion of the bodies of hermit crabs, -which are, therefore, far better preserved in fluid. Dilute spirit is -quite satisfactory for most of these as far as the preservation of the -soft structures is concerned, but it has the disadvantage that it turns -the shells of some crustaceans red, making them appear as if they had -been boiled. - -Other crustaceans are so small, or are hardened externally to such a -slight extent, that they also are not adapted for the dry method of -preservation. Speaking generally, such crustaceans as shrimps and -sand-hoppers are best preserved in fluid, while the different species of -crabs and lobsters are more conveniently preserved dry unless it is -desired to study any of their soft structures. - -It is quite impossible to remove the soft parts from small crabs and -lobsters previous to drying them, hence the drying should be conducted -as rapidly as possible, so that no decomposition may set in. Where the -process goes on very slowly, as is the case when the air is damp, or -when the specimens are not set out in an airy spot, a decay of the soft -structures soon proceeds, and the products of this decay will generally -saturate the whole specimen, giving rise to most objectionable odours, -and destroying the natural colour of the shell. - -If it has been found that the species in question are not reddened by -the action of methylated spirit, they should be allowed to remain in -this fluid, with a few grains of dissolved corrosive sublimate, for at -least a few hours, and then they will dry rapidly without any signs of -putrefaction; and even those species that _are_ reddened by spirit may -be treated to a shorter immersion in this fluid with advantage. - -The specimens should always be set out in some natural attitude to dry, -unless it is desired to spread out the various appendages in some manner -that is more convenient for the study of their structure. A sheet of -blotting-paper may be placed on cork or soft wood, the specimens placed -on this, and the appendages kept in the desired positions when necessary -by means of pins placed beside, but not thrust through them. When more -than one specimen of the same species has been collected, one should be -set in such a manner as to exhibit the under side; and, further, in -instances where the male and female of the same crustacean differ in -structure, as is commonly the case, two of each should be preserved, one -displaying the upper, and the other the under surface. - -When perfectly dry, all small crustaceans should be mounted on cards -with the aid of a little gum, and the name and other particulars to be -remembered then written on the card. - -The question may well be asked: 'Which is the best gum to use?' In -answer to this we may say that gum tragacanth is certainly as good as -any. It holds well, and leaves no visible stain on a white card. A small -quantity of the solid gum should be put into a bottle with water in -which a grain or so of corrosive sublimate has been dissolved. It -absorbs much water, becoming a very soft, jelly-like mass. Any excess of -water may be poured off, and the gum is then ready for use. - -The larger crabs and lobsters contain such an amount of soft tissue -within that it becomes absolutely necessary to clear them in order to -avoid the unpleasant and destructive effects of decomposition. - - [Illustration: FIG. 43.--SMALL CRAB MOUNTED ON A CARD] - -In the case of lobsters the abdomen should be removed from the large -cephalo-thorax by cutting through the connecting membrane with a sharp -knife. The soft portions of both halves of the body are then raked out -by means of a piece of wire flattened and bent at one end, and the -interior cleaned with the aid of a rather stiff bottle-brush. The large -claws are then removed by cutting through the membrane that unites them -with the legs, and these are cleared in a similar manner. The different -parts are next laid out to dry on blotting-paper, with the various -appendages attached to the body arranged just as in life; and, finally, -when all parts are quite dry, both within and without, the separated -parts are reattached by means of some kind of cement. For this purpose a -solution of gelatine in acetic acid is much better than gum tragacanth, -as it has a far greater holding power, and this is necessary when we -require to unite rather large structures with but small surfaces in -contact. - -Large crabs are to be dealt with much in the same manner, but, instead -of removing the abdomen only, which, in the crab, is usually very small -and doubled under the thorax, the whole carapace--the large shell that -covers the entire upper surface of the body--should be lifted off, and -replaced again after the specimen has been cleaned and dried. - - - MARINE SHELLS &C. - -We have previously dealt with the preservation of the shell-less -molluscs, and the soft bodies of the shelled species when such are -required, so we will now see what should be done with the shells. - -Numerous shells are often to be found on the sea beach--shells that have -been washed in by the breakers, and from which the animal contents have -disappeared, either by the natural process of decay, aided by the action -of the waves, or by the ravages of the voracious or carrion-eating -denizens of the sea; and although these shells are rarely perfect, -having been tossed about among the other material of the beach, yet we -occasionally find here the most perfect specimens of both univalve and -bivalve shells in such a condition that they are ready for the cabinet, -and these often include species that are seldom found between the -tide-marks, or that are otherwise difficult to obtain. - -However, the shell-collector must not rely on such specimens as these -for the purpose of making up his stock, but must search out the living -molluscs in their habitats and prepare the shells as required. - -The molluscs collected for this purpose are immersed in boiling water -for a short time, and the animal then removed from the shell. In the -case of bivalves it will generally be found that the hot water has -caused the muscles of the animal to separate from the valves to which -they were attached, or, if not, they have been so far softened that they -are easily detached, while it does not destroy the ligament by means of -which the valves are held together at the hinge; but the univalve -molluscs must be removed from their shells by means of a bent pin or -wire. In the latter instance care must be taken to extract the whole of -the body of the animal, otherwise the remaining portion will decompose -within the shell, giving rise to the noxious products of natural decay. - -The univalves have now simply to be placed mouth downwards on -blotting-paper to drain and dry, when they are ready for the cabinet. -If, however, they include those species, like the periwinkles and -whelks, that close their shells by means of a horny lid (_operculum_) -when they draw in their bodies, these lids should be removed from the -animal and attached to their proper places in the mouth of the shell. -The best way to accomplish this is to pack the dry shells with cotton -wool, and then fasten the opercula to the wool by means of a little gum -tragacanth or acetic glue. - -Bivalve shells should, as a rule, be closed while the ligament is still -supple, and kept closed until it is quite dry, when the valves will -remain together just in the position they assume when pulled together by -the living animal. The shells of the larger species may be conveniently -kept closed during the drying of the ligament by means of thread tied -round them, but the very small ones are best held together by means of a -delicate spring made by bending fine brass wire into the form shown in -fig. 44. - - [Illustration: FIG. 44.--SPRING FOR HOLDING TOGETHER SMALL BIVALVE - SHELLS] - -There are many features connected with the internal structure and -surface of the shells of molluscs that are quite as interesting and -instructive as those exhibited externally; hence a collection of the -shells intended for future study should display internal as well as -external characteristics. Thus, some of the spiral univalve shells may -be ground down on an ordinary grindstone in order to display the central -pillar (the _columella_) and the winding cavity that surrounds it, while -others, such as the cowries, may be ground transversely to show the -widely different character of the interior. Bivalve shells, too, may be -arranged with the valves wide open for the study of the pearly layer, -the lines of growth, the scars which mark the positions of the muscles -that were attached to the shell, and the teeth which are so wonderfully -formed in some species. - -Some collectors make it a rule to thoroughly clean all the shells in -their collection, but this, we think, is a great mistake; for when this -is done many of the specimens display an aspect that is but seldom -observed in nature. Many shells, and especially those usually obtained -in deep water, are almost always covered with various forms of both -animal and vegetable growth, and it is advisable to display these in a -collection, not only because they determine the general natural -appearance, but also because these growths are in themselves very -interesting objects. Further, it is a most interesting study to inquire -into the possible advantages of these external growths to the -inhabitants of the shells, and _vice versa_--a study to which we shall -refer again in certain chapters devoted to the description of the -animals concerned. - -But there is no reason whatever why some of the _duplicate_ specimens -should not be cleaned by means of a suitable brush, with or without the -use of dilute hydrochloric acid (spirits of salt), or even polished, in -some few cases, to show the beautiful colours so often exhibited when -the surface layer has been removed. This, however, should be done -somewhat sparingly, thus giving the greater prominence to the exhibition -of those appearances most commonly displayed by the shells as we find -them on the beach or dredge them from the sea. - -Very small and delicate shells may be mounted on cards, as suggested for -other objects; but, as a rule, the specimens are best displayed by -simply placing them on a layer of cotton wool in shallow boxes of -convenient size. - -The number of insects that may be described as truly marine is so small -that their preservation is not likely to form an important part of the -work of the sea-side naturalist; and even though a considerable number -of species exhibit a decided partiality for the coast, living either on -the beach or the cliffs, the study of these is more generally the work -of the entomologist. For this reason, and partly because we have already -given full instructions for the setting and mounting of insects in a -former work of this series, we consider a repetition inadmissible here. - -The subject of the preservation of fishes, also, will require but few -words. There is no satisfactory method of preserving these in a dry -state, though we often meet with certain thin-bodied species, such as -the pipe-fish, that have been preserved by simply drying them in the -sun. Fishes should be placed in dilute spirit, or in one of the other -liquids recommended, but a change of fluid will always be necessary -after a time, and also frequently the gentle application of a brush to -remove coagulated slime from the surface of the scales. - -The great drawbacks in the way of preserving a collection of fishes are -the expense of the specimen jars, and the large amount of space required -for storing the specimens. Of course the former difficulty can be -overcome by substituting ordinary wide-mouthed bottles in the place of -the anatomical jars, while the latter can be avoided to a considerable -extent by limiting the collection to small species, and to small -specimens of the larger species. If this is done, it is surprising what -a large number of fishes can be satisfactorily stored in bottles of only -a few ounces' capacity. - - - FLOWERS AND SEA WEEDS - -The apparatus required for the preservation of the wild flowers of our -cliffs, and the sea weeds, consists of a quantity of blotting paper or -other thick absorbent paper cut to a convenient size, a few thin boards -and a few pieces of calico of the same size, some heavy weights, and -several sheets of drawing paper. - -The wild flowers are arranged on the sheets of absorbent paper while -still fresh, care being taken to display the principal parts to the best -advantage. They are then placed in a single pile, with a few extra -sheets of absorbent paper between each two specimens to facilitate the -drying, boards at the bottom and top as well as at equal distances in -the midst of the pile, and the weights on the top of the whole. - -The natural colours of leaves and flowers are not very often preserved -satisfactorily, but the best results are obtained when the drying -process proceeds most rapidly. Hence, if the press contains any -specimens of a succulent or sappy nature, they should be taken out after -the first day or two, and then replaced with a fresh supply of dry -paper. - -The flowers must be left in the press until quite dry, and they may then -be mounted on sheets of drawing paper, by fixing them with a little gum -tragacanth, or by narrow strips of gummed paper passing over their -stems. - -Some collectors prefer simply placing their botanical specimens inside -double sheets of drawing paper, not fastening them at all, and there is -much to be said in favour of this, especially as it allows the specimens -to be examined on both sides; and even when they _are_ fastened to the -paper double sheets are much to be preferred, for the specimens are not -then so liable to be damaged by friction when being turned over, -especially when the names are written on the outside of each sheet. - -The larger sea-weeds may be dried in the same manner, though it is a -good plan to absorb the greater part of the moisture they contain by -pressing them between pieces of calico previous to placing them in the -ordinary press. It should be observed, however, that many sea-weeds -exude a certain amount of glutinous substance that makes them adhere to -the paper between which they are dried, while they do not so freely -adhere to calico. These should be partially dried in the calico press, -and then laid on the paper on which they are to be finally mounted, and -re-pressed with a piece of dry calico on the top of each specimen. - -Many of the smaller weeds may be treated in the manner just described, -but the more delicate species require to be dealt with as -follows:--Place each in a large, shallow vessel of water, and move it -about, if necessary, to cause its delicate fronds to assume that -graceful form so characteristic of the algae of our rock pools. Then -immerse the sheet of paper on which the weed is to be finally mounted, -and slowly raise the specimen out of the water, on the paper, without -disturbing the arrangement of the fronds. If it is found necessary to -rearrange any of the fronds, it may be done by means of a wet camel-hair -brush. Now lay the specimen on calico or absorbent paper, placed on a -sloping board, to drain; and, after the greater part of the moisture has -disappeared by draining and evaporation, transfer the specimen to the -press with a piece of dry calico immediately over it. All are dealt with -in turn in the manner described, and allowed to remain in the press -until perfectly dry, when it will be found that the majority of them -have become firmly attached to the mount, and require nothing but the -label to fit them for the herbarium. - -Sea-weed collectors often make the great mistake of pressing tufts that -are far too dense to admit of the structural characters being -satisfactorily examined. To avoid this fault, it will often be necessary -to divide the clusters collected so that the forms of their fronds may -be more readily observed. - -The calcareous corallines may be pressed in the same way as the other -algae, but very pretty tufts of these, having much the appearance of the -living plant, may be obtained by simply suspending them until thoroughly -dry; though, of course, specimens so prepared must not be submitted to -pressure after they are dry, being then so brittle that they are easily -broken to pieces. - -The hard framework of these interesting corallines is composed -principally of carbonate of lime, a mineral substance that dissolves -freely in hydrochloric acid (spirits of salt). Thus, if we place a tuft -of coralline in this acid, which should be considerably diluted with -water, the calcareous skeleton immediately begins to dissolve, with the -evolution of minute bubbles of carbonic acid gas; and after a short -time, the end of which is denoted by the absence of any further -bubbling, nothing remains but the vegetable matter, now rendered soft -and pliant. A decalcified specimen of coralline may be pressed and -dried, and then mounted beside the plant in its natural condition for -comparison; and the true appearance of the vegetable structure may also -be retained, and in a far more satisfactory manner, by preserving a -portion of the specimen in dilute spirit. - -Finally, it may be observed that many sea-weeds, like wild flowers, do -not retain their natural forms and colours when preserved dry. They are -spoilt by the pressure applied, or become so shrivelled and discoloured -in the drying as to be but sorry representatives of the beautifully -tinted and graceful clothing of the rocks of the coast. But many of -those that suffer most in appearance when dried may be made to retain -all their natural beauty by preserving them in a fluid; and it is most -important that this should be remembered by all who desire to study the -weeds at home, and particularly by those who possess a microscope, and -wish to search into the minute structure of marine algae. Our own plan is -to keep not only the dried specimens for the purpose of studying the -general characters and classification of the algae, but also to keep a -few large bottles--stock bottles--filled with weeds of all kinds in a -preservative fluid. These latter are exceedingly useful at times, and -are frequently brought into requisition for close inspection, with or -without the microscope. Small pieces may be detached for microscopic -examination when required, and sections may be cut either for temporary -or permanent mounting just as well as from living specimens, such -sections showing all the details of structure exhibited by the living -plant. - - - THE MUSEUM - -One of the greatest difficulties besetting the young collector lies in -the choice and construction of the cabinet or other store-house for the -accommodation of the specimens that accumulate as time advances. - -Of course, when expense is a matter of no great consideration, a visit -to the nearest public or private museum to see the manner in which the -specimens are housed, followed by an order to a cabinet-maker, will set -the matter right in a short time; but it is probable that the majority -of our readers are unable to fit up their museum in this luxurious -style, and will either have to construct their own cabinets and -store-boxes or to purchase cheap substitutes for them. - -Where one has the mechanical ability, and the time to spare, the -construction of a cabinet with the required number of drawers may be -undertaken, and there is no better form of store than this. The whole -should be made of well-seasoned wood, and the drawers should vary in -depth according to the size of the specimens they are to contain. Some -of these drawers may be lined with sheet cork, and the cork covered with -white paper or a thin layer of cotton wool. This will enable some of the -specimens to be fixed in their places by means of pins. As a rule, -however, no pins will be required, and the specimens will be most -conveniently arranged in shallow cardboard boxes, placed in rows in the -drawer, a little cotton wool covering the bottom of each. - -Failing the usual cabinet, the specimens may be stored in shallow trays -or boxes, or even in the little cardboard cabinets so often sold for -storing stationery &c. The best and cheapest things of this kind we have -ever met with are the little cabinets, each containing either six or -twelve drawers, made by Macdonald & Co., of Temple Row, Birmingham. By -the use of such as these the specimens may be neatly stored away, and -additions to match may always be made as the collection increases in -magnitude. - -The specimens should all be classified according to their positions in -the animal or vegetable world, and accompanied by labels giving the name -of species and genus, together with localities, habitats, &c. The -outlines of classification may be studied from the later chapters of -this work, in which the common objects of the sea shore are described in -their scientific order, beginning with the lowest sub-kingdoms and -classes; and further, it will be observed that the sub-kingdoms are -divided into classes, the classes into orders, orders into families, -families into genera, and that the genera contain a smaller or larger -number of closely allied species. - -The collection must be kept in a perfectly dry place, otherwise many of -the specimens will be liable to develop moulds, and this will, of -course, quite spoil their appearance. It is almost sure to be attacked -by mites and other animal pests unless some means be taken to prevent -their intrusion. - -As regards the latter, it is well to know that it is far easier to -prevent the intrusion of small animal pests than it is to exterminate -them after they have once found an entrance; and so, from the very -commencement of the formation of the collection, all drawers and boxes -should be charged with some substance that is objectionable, if not -fatal, to them. Small lumps of naphthaline (albo-carbon) put into the -various compartments, and renewed occasionally as they disappear by -evaporation, will generally suffice to prevent the entrance of all -pests, but this substance is not effectual as an insecticide for the -purpose of killing them after they are in. - -Perhaps the best of all insecticides is the corrosive sublimate already -mentioned, and this may be applied to any animal or vegetable object -that is capable of providing food for museum pests, and it is difficult -to find such an object on which they will not feed. - -Many of the specimens that find a place in a museum have been -temporarily preserved in spirit previous to being dried, and if a little -corrosive sublimate was dissolved in this spirit, the specimens will -have been rendered perfectly free from all attacks of marauders, since -the spirit will have saturated the whole object, carrying with it the -dissolved poison. - -Most of the specimens that have not been treated by the above method -would not suffer from a short immersion in spirit containing the -corrosive sublimate; but in cases where it is considered inexpedient to -do this, the same liquid may be applied to them by means of a soft -brush. In this way even the dried botanical specimens may be rendered -perfectly secure from attacks. - - - - - CHAPTER VI - - _EXAMINATION OF MARINE OBJECTS--DISSECTION_ - - -An enthusiastic observer of nature will learn much concerning the -structure of natural objects with the unaided eye, but there are times -when he will desire some kind of magnifier to reveal more perfectly the -structure of minute parts, or to enable him to observe the small -creatures that are invisible to the naked eye. Further, one may learn -many interesting and instructive facts relating to animal and plant life -by cutting sections for close examination, or by making such simple -dissections as will enable one to observe the more salient features of -internal structure; we therefore propose in the present chapter to make -a few remarks and suggestions regarding work of this kind. - -A pocket magnifier is of great value to the young naturalist, both for -the inspection of natural objects while engaged in out-door work, and -for the subsequent examination of the specimens collected for study. It -is often necessary to enable one to identify and classify small animals -and plants, and will be in constant demand for the purpose of studying -the less conspicuous external features. Such an instrument should be -regarded as an essential companion of the naturalist, and should -accompany him on every ramble. - -There are several different forms of pocket lenses, but for general work -there is, perhaps, nothing more convenient and serviceable than the -'triplet' magnifier. It is a combination of three lenses, enclosed in a -pocket case, and so arranged that they may be used separately or in -combination, thus supplying a variety of powers. The three lenses of the -triplet are themselves of different magnifying powers, and these powers -may be increased by combining two or all of them. - -For work at home a 'dissecting microscope' is very useful. This consists -of a magnifying lens, mounted on a support over a surface on which small -objects may be examined and dissected, the height of the lens being, of -course, adjusted according to its focal distance. Lenses ready mounted -on adjustable stands may be purchased for this purpose, but no one ought -to experience much difficulty in designing and constructing some simple -stand that will give every satisfaction. - -The arrangement just described is, of course, suitable for the -dissection of only small objects, and these are placed on a material -adapted to the nature of the work to be done. Thus it is sometimes -convenient to place the object to be examined on a small sheet of cork, -in order that it may be secured by means of pins while the dissection -proceeds, while at other times it is essential that it be laid on a hard -and unyielding surface, such as that of a slip of glass. But whatever be -the nature of the substance on which the dissection is made, its colour -may be regulated according to that of the object. If, for example, we -are dissecting a small white flower on a piece of cork, we should -naturally blacken the cork, or cover it with a piece of dead black -paper; or, if we are to dissect a small, light-coloured object on a -glass surface, we lay the glass on black paper. - - [Illustration: FIG. 45--THE TRIPLET MAGNIFIER] - -The advantage of dissecting objects under water does not seem to be -generally appreciated by beginners, who often allow their specimens to -become dry and shrivelled, almost beyond recognition, during the -progress of their examination. This mode of dissection is certainly not -necessary with all objects, but may be generally recommended for soft -and succulent vegetable structures, as well as for almost all animal -dissections. - -This being the case, arrangements should certainly be made to provide a -miniature dissecting trough as an accessory to the dissecting -microscope, and the following instructions will enable the reader to -construct a highly satisfactory and inexpensive one:-- - -Procure the flat lid of a cylindrical tin box, or the lid of a glass or -porcelain pomade pot, such lid to be about two inches in diameter and -about half an inch in depth. Cement the flat side of this lid to a small -slab of hard wood, or to a square piece of sheet lead, by means of -acetic glue--ordinary glue or gelatine dissolved in glacial acetic -acid--to give it the necessary steadiness during the dissection. When -the cement is quite hard, pour into the lid some melted paraffin -(paraffin wax) which has been blackened by the admixture of a small -quantity of lamp-black in the form of a fine powder. The paraffin should -be melted by putting it into a beaker or wide-mouthed bottle, and -standing it in hot water, and the lamp-black should be added, with -stirring, as soon as it is entirely liquefied. The quantity of the -mixture used must be sufficient to half fill the lid, thus leaving a -space to contain water to the depth of about a quarter of an inch. The -blackened wax provides a good background on which to work, and provides -a hold for pins when these are necessary in order to fix the object -under examination. - - [Illustration: FIG. 46.--A SMALL DISSECTING TROUGH] - -The complete trough is represented in fig. 46; and will be found to -answer its purpose admirably, except that it occasionally displays one -fault, but one that is easily remedied. The wax contracts on cooling, -and may, therefore, detach itself from the trough; and, being lighter -than water, will float instead of remaining submerged. This may be -prevented by securing the disc of wax in its place by means of a ring of -brass wire, or by weighting the wax with two or three small pieces of -lead pushed down into it while it is yet soft. - -With such a dissecting microscope and trough as we have described one -may do a great deal of exceedingly useful work, both hands being quite -free to manipulate the object under examination. - -The dissection may be conducted with the aid of a small scalpel or other -very sharp knife, the parts being arranged or adjusted by means of a -needle, mounted in a handle, and held in the left hand. Sometimes, -however, the object to be dissected is so minute that even a small -scalpel is too large for the purpose, and in such cases nothing is -better than little dissecting instruments made by mounting large sewing -needles in suitable handles, and then grinding down the points of the -needles on two opposite sides, on a hone, so as to produce little -pointed, two-edged blades. Bent needles are often useful, too, and these -may be prepared by heating the points to redness in a gas-flame, bending -them as desired while hot, and then hardening them by suddenly thrusting -them, at a red heat, into cold water. - -The compound microscope will often prove useful for the examination of -very minute objects, as well as for the study of the structure of the -principal tissues of the larger species; but since detailed instructions -for the management of the microscope, and for the preparation of objects -for microscopic examination would occupy much more space than we can -spare, we shall content ourselves with nothing more than a few general -hints on this portion of the young naturalist's work, dealing more -particularly with those points which commonly present difficulties to -the amateur. - -If it is desired to examine some minute living object, such as a -protozoon, place the object in a drop of the water in which it lived -just in the middle of a clean glass slip, and cover it with a -cover-glass. The quantity of water should be just sufficient to fill the -space between the two glasses. If less than this has been used, a little -more applied to the edge of the cover by means of a glass rod will -immediately run in between the glasses; while if an excessive amount was -employed, the surplus may be removed by the application of a strip of -blotting paper. Place the glass slip on the stage of the microscope, and -reflect light through it from the mirror below. - -Examine it first with a low power; and, after having observed as much as -possible of the creature's movements and structure with this aid, repeat -with a higher power. This rule applies not only to such small objects as -we have now under consideration, but to all objects, and parts of them, -in which minute details are to be observed. - -Beginners with the microscope often find prolonged examination very -tiring to the eyes, but this, we believe, would seldom be the case if -right methods were followed. Both eyes should always be open, and the -microscopist should train himself to use both eyes equally for the -actual observation. - -The higher the magnifying power used, the nearer must the objective (the -lower combination of lenses) be brought to the object itself, and it is -no uncommon thing for the amateur, in his attempts to focus his object, -to lower the body of the microscope beyond its proper position, causing -the objective to crush the object, break the thin cover-glass, and -become wetted with the liquid, if any, in which the object was being -examined. All this may be avoided by lowering the body of the microscope -until it nearly touches the cover-glass before attempting to view the -object through it, and then, with the eye above the object-glass, to -gradually raise the body until the object is in focus. - - [Illustration: FIG. 47.--CELL FOR SMALL LIVING OBJECTS] - -The top of the cover-glass should always be perfectly dry; and if by any -chance the objective becomes wet it should be wiped perfectly dry with a -piece of old silk or with chamois leather. Also, if permanent mounting -is attempted, and the preservative liquid is allowed to come in contact -with the objective, such liquid must, of course, be washed off with some -suitable solvent before any attempt is made to wipe the lens dry. - -If the object under examination is of such dimensions that the -cover-glass has a tendency to rock on it, or if it is a living object of -such a size that it is unable to move freely in the exceedingly thin -film of water between the cover and the slip, it should be placed in a -cell. The cell may be made by cementing a ring of glass or vulcanite to -the middle of a slip, or it may be a little circular cavity prepared in -the slip itself. In either case the cell must be quite full of water -before the cover-glass is applied, so that no air-bubbles are included. - -Hitherto we have spoken only of mounting small objects in water, and -this is advisable when the object is moist, whether it be animal or -vegetable, alive or dead. But dry objects may be examined in the dry -state, in which case they need not be covered. If they are composed of -transparent material they are to be dealt with in the manner recommended -before, as far as the management of the light is considered; that is, a -moderately strong light is sent through them by the reflector below the -stage; but opaque objects are best examined on a dead black ground, the -light being directed on to them by means of a condensing lens placed -between them and the source of light. - -A collector who has done only a few days' work on the sea shore will -probably find himself the possessor of a host of interesting objects -that will afford much pleasure and instruction when placed under the -microscope--objects, many of which have been somewhat hastily deposited -in a bottle of spirit or other preservative for study in his future -leisure moments. These objects, if small, may be examined as above -described, simply placing them under a cover-glass, or in a cell, with a -clear drop of the same liquid in which they have been kept. - -The general characters of the larger objects may also be observed by -means of some kind of hand lens, but even these are generally best -examined under water or other suitable liquid. - -A great deal may be learnt of natural objects by preparing very thin -sections for microscopic examination; and although special works should -be consulted if one desires to become proficient in the different -methods of cutting and preparing such sections, yet a great amount of -good work may be done with the aid of a sharp razor, manipulated with -nothing more than ordinary skill. - -Some objects, especially certain of those of the vegetable world, are of -such a nature that suitable sections may be cut, either from the fresh -or preserved specimen, without any preliminary preparation. All that is -required is to hold the object firmly between the finger and thumb of -the left hand, previously securing it in some kind of holder if -necessary, and pare off the thinnest possible slices with a horizontal -movement of the razor, both razor and object being kept very wet during -the process. As the sections are cut they may be allowed to drop into a -shallow vessel of water; and, the thinnest then selected for examination -in water as previously described. - -Other objects are so soft that the cutting of sections becomes -impossible without previously hardening them. Methylated spirit is a -good hardening reagent, and many of the soft structures that have been -preserved in this fluid, especially if it has been used undiluted, will -be found sufficiently hard for cutting thin sections. Among the other -hardening reagents used by microscopists may be mentioned a solution of -chromic acid--one part by weight of the solid acid dissolved in from one -hundred to two hundred parts of water, and a solution of bichromate of -potash--one part of the bichromate to about forty parts of water. In -either case the hardening of the object takes place slowly, and it -should be examined from day to day until the necessary consistence has -been obtained. - -The structures of many soft animals can never be satisfactorily hardened -for section-cutting by either of the above reagents, and thus it becomes -necessary either to freeze or to imbed them. In the former case the -object is first soaked in gum water--a thin solution of gum arabic--and -then frozen by an ether spray or by a mixture of ice and salt. The -sections should be cut with a razor just as the object is beginning to -thaw, and they may then be examined under a cover-glass, in a drop of -the gum water. - -The other method is conducted as follows:--The soft object is first -soaked in absolute alcohol to extract all the water it contains, and is -then transferred to paraffin that has been heated just to its -melting-point by standing it in warm water. After the object is -thoroughly permeated with the paraffin, the whole is cooled quickly by -immersion in cold water. Sections are now cut, the paraffin being sliced -away with the substance it contains. These sections are placed in warm -turpentine, where they are allowed to remain until the whole of the wax -has dissolved, and they may then be mounted in a drop of turpentine, and -covered with a cover-glass. - -We have given brief instructions for temporary mounting only, but most -amateur microscopists would undoubtedly prefer mounting their objects -permanently, so that they may be set aside for study at any future -period. Hence we append a few directions to this end, advising the -reader, however, to consult a work dealing especially with this subject -if he desires to become proficient in the preparation of microscopic -slides. - -Moist objects, including those which have been preserved in dilute -spirit, may be soaked in water, then transferred direct to the glass -slip, and covered with a drop of glycerine. Any excess of the glycerine -should then be absorbed from around the cover-glass by means of a strip -of blotting-paper, and the edge of the cover cemented by gold size -applied with a small camel-hair brush. - -Glycerine jelly is also a valuable mountant for permanent work. When -this is used the object should first be soaked in glycerine, and then in -the melted jelly. It is then transferred to a drop of melted jelly which -has been placed on a _warm_ slide, and covered as before. The jelly soon -solidifies, so that a ring of cement is not absolutely necessary, though -it is advisable, as a rule, to cement the cover-glass all round with -gold size or black varnish. - -Sections cut while frozen are best mounted in glycerine, to which they -may be transferred direct. - -Canada balsam is one of the best media for permanent mounting; and, as -it becomes very hard after a time, it serves the purposes of both -preservative and cement. When this is used the object must be entirely -freed from water by soaking it in absolute alcohol. It is then put into -turpentine for a minute or two, transferred to a warm slide, and covered -with a drop of the prepared balsam. Sections that have been imbedded in -paraffin may be mounted in this way, the turpentine acting as a solvent -for the paraffin in which it was cut. - -Although the compound microscope is absolutely necessary for the study -of the minutest forms of life and of the minute structure of the various -tissues of larger beings, yet the young naturalist will find that a vast -amount of good work may be done without its aid. Thus the general -structure of the larger species may be made out by means of simple -dissections requiring no extraordinary skill on the part of the worker, -and with appliances that may be obtained at a low cost. Certain of the -marine animals, however, require special treatment that can hardly be -described in a short chapter devoted to general instructions only, but -hints with regards to these will be given in future chapters in which -the animals referred to are described. - -The appliances referred to above include nothing more than a simple form -of dissecting trough, a few dissecting instruments, and one or two minor -accessories that may always be found at hand as required. - -The dissection of animals is always best performed under water, for by -this method the object examined may not only be kept clean as the work -proceeds, but the parts, having a tendency to float, readily separate -from one another and therefore become more distinctly visible when -submerged. - - [Illustration: FIG. 48.--SHEET OF CORK ON THIN SHEET LEAD] - -A very convenient form of trough may be made by taking any kind of -rectangular, flat-bottomed dish, one made of zinc being, perhaps, the -best of all, and covering the bottom with a slab of good cork carpet -which has been weighted with sufficient lead to prevent it from -floating. Or, instead of cork carpet, a sheet of cork may be used. In -either case, a piece of thin sheet lead, a little larger than the slab, -should be cut, the corners of which are then snipped off as shown in -fig. 48, and the edges finally turned over as represented in the next -illustration. The size of the trough must be regulated according to the -nature of the work to be done, but one measuring ten inches long, seven -wide, and two inches deep will answer most purposes. - - [Illustration: FIG. 49.--WEIGHTED CORK FOR DISSECTING TROUGH] - -The object to be dissected is placed in the trough, secured in position -by means of a few ordinary pins, and then completely covered with -water. - -We need hardly impress upon the reader the great importance of -thoroughly examining all external characters--all those structures that -are visible without actual dissection--before attempting to remove -anything; and we have already insisted on the importance of carefully -examining all creatures while alive before anything else is done. The -value of this latter stipulation can hardly be overestimated, for in -many instances it is almost impossible to detect the use of an organ -unless it has been observed in action; and the enthusiastic student will -go even further than this, for he will make it an invariable rule to -sketch everything he sees, and to make full notes on all his -observations. - -When pins are used to fix the object under examination--and it is -generally essential that the object be fixed--their heads should be -turned outwards; for then the object will not slip from its position, -nor will the pins tend to get in the way of the work. - -Some objects are of such a nature that they are not easily secured by -means of pins, and yet require to be fixed in some way or other. Thus, -one may desire to examine the structure and appendages of a prawn or -small crab, or to investigate the nature of a chiton. In such instances -as these it is a good plan to make a cake of paraffin wax of suitable -size by pouring the melted substance into a mould, then secure the -object in proper position in the wax while still fluid, and pin the -latter to the cork of the dissecting trough. - -It is often necessary to trace the courses of internal passages that -open on the surface of the body, or of tubes that are revealed during -the progress of dissection, and this may be done by means of a little -instrument called a seeker. It is simply a blunted needle, bent into a -large angle, and mounted in a handle; or, it may consist of nothing but -a moderately long and stiff bristle, rendered blunt at one end by -tipping it with melted sealing wax. This is not always sufficient, -however, for it frequently happens that certain tubes and passages in -animal forms are disposed in such a complicated manner that it is -impossible to send even the most flexible seeker through them. For -instance, suppose one desires to trace the course of the digestive tube -of some large bivalve mollusc with its many reflections, the seeker is -useless except that it will penetrate to the first sharp bend. The -arrangement of such a tube must be traced by dissecting along its -course, but this may be aided considerably by first filling it with some -coloured substance to enable its direction to be more easily followed. -In fact, the injection of some brightly coloured fluid, forced through -the tube by means of a fine-nozzled glass syringe will often enable the -course of such a tube to be seen without any dissection at all, the -colour of the fluid used being detected through the semi-transparent -tissues surrounding it. A mixture of Berlin blue and water, or a mixture -of plaster of Paris and water coloured with carmine is well adapted to -this purpose; and if the latter is employed it may be allowed to set, -and thus produce a permanent cast from the tube that is being dissected. -Perhaps it should be mentioned that if either of the injection mixtures -be used for this purpose it must be previously strained through muslin, -and that, in the case of the plaster, the mixing and straining should -occupy as little time as possible, or it may begin to set before the -injection has been completed. - -A very considerable insight into the structure of animals may be -frequently obtained by cutting sections through the body with all its -organs _in situ_, but, generally speaking, they are too soft to allow of -this without danger of the displacement of those very parts, the -relations of which we desire to determine. To avoid this the body should -be previously hardened by a somewhat prolonged soaking in methylated -spirit, or in a solution of chromic acid prepared as before directed. -Then, with the aid of a good razor, very interesting sections may be -prepared with the greatest of ease, and the true relations of the -various organs throughout the body may be exactly determined by cutting -a succession of slices, not necessarily very thin, from end to end, or, -transversely, from side to side. - -Even those crustaceans that are protected by a hard, calcareous -exo-skeleton, and the molluscs that cannot be removed from their stony -shells without injury to their soft structures, may be studied in the -manner just described, and this may be done by first soaking them in -dilute hydrochloric acid, renewed as often as may be necessary, until -all the mineral matter has been dissolved completely, and then hardening -the softer tissues in one of the reagents mentioned above. Hydrochloric -acid may also be used to dissolve the calcareous shells of foraminifers, -the vegetable corallines, and other small forms of life, previous to -microscopic examination of the soft parts. - - - - - CHAPTER VII - - _THE PROTOZOA OF THE SEA SHORE_ - - -We shall now study the principal forms of animal life to be found on the -sea shore; and, in order that the reader may thoroughly understand the -broader principles of classification, so as to be able to locate each -creature observed in its approximate position in the scale of life, we -shall consider each group in its zoological order, commencing with the -lowest forms, and noting, as we proceed, the distinguishing -characteristics of each division. - -The present chapter will be devoted to the _Protozoa_--the sub-kingdom -that includes the simplest of all animal beings. - -Each animal in this division consists of a minute mass of a jelly-like -substance called _protoplasm_, exhibiting little or no differentiation -in structure. There is no true body-cavity, no special organs for the -performance of distinct functions, and no nervous system. - -Perhaps we can best understand the nature of a protozoon by selecting -and examining a typical example: - -Remove a small quantity of the green thread-like algous weed so commonly -seen attached to the banks of both fresh and salt water pools, or -surrounding floating objects, and place it in a glass with a little of -the water in which it grew. This weed probably shelters numerous -protozoons, among which we are almost sure to find some _amoebae_ if we -examine a drop of the water under the high power of a microscope. - - [Illustration: FIG. 50.--THE AMOEBA, HIGHLY MAGNIFIED] - -The amoeba is observed to be a minute mass of protoplasm with an -average diameter of about one-hundredth of an inch, endowed with a power -of motion and locomotion. Its body is not uniformly clear, for the -interior portion is seen to contain a number of minute granules, -representing the undigested portions of the animal's food. There is a -small mass of denser protoplasm near the centre, termed the _nucleus_, -and also a clear space filled with fluid. This latter is called the -_vacuole_, and is probably connected with the processes of respiration -and excretion, for it may be seen to contract at irregular intervals, -and occasionally to collapse and expel its contents. - -As we watch the amoeba we see that it is continually changing its -shape, sending out temporary prolongations (_pseudopodia_) of its -gelatinous substance from any part, and sometimes using these extended -portions for the purpose of dragging itself along. - -Its method of feeding is as remarkable as it is simple. On coming in -contact with any desired morsel, it sends out two pseudopods, one on -each side of the food. These two pseudopods gradually extend round the -food, till, at last, they meet and coalesce on the opposite side of it, -thus completely enclosing it within the body. Any part of the body of -the am[oe]ba may thus be converted into a temporary mouth; and, there -being no special cavity to serve the purpose of a stomach, the process -of digestion will proceed equally well in any part of the body except in -the superficial layer, where the protoplasm is of a slightly firmer -consistence than that of the interior. Further, the process of digestion -being over, any portion of the superficial layer may be converted into a -temporary opening to admit of the discharge of indigestible matter. - - [Illustration: FIG. 51.--THE AMOEBA, SHOWING CHANGES OF FORM] - - [Illustration: FIG. 52.--THE AMOEBA, FEEDING] - -The amoeba is an omnivorous feeder, but subsists mainly on vegetable -organisms, especially on diatoms and other minute algae; and the -siliceous skeletons of the former may often be seen within the body of -the animal, under the high power of a microscope. - -The multiplication of the amoeba is brought about by a process of -fission or division. At first the nucleus divides into two, and then the -softer protoplasm contracts in the middle, and finally divides into two -portions, each of which contains one of the nuclei. The two distinct -animals thus produced both grow until they reach the dimensions of -their common progenitor. - - [Illustration: FIG. 53.--THE AMOEBA, DIVIDING] - -All the protozoons resemble the amoeba in general structure and -function; but while some are even simpler in organisation, others are -more highly specialised. Some, like the amoeba, are unicellular -animals; that is, they consist of a single, simple speck of protoplasm; -but others live in colonies, each newly formed cell remaining attached -to its parent cell, until at last a comparatively large compound -protozoon is formed. - -The sub-kingdom is divided into several classes, the principal of which, -together with their leading characteristics, are shown in the following -table:-- - - 1. _Rhizopods:_--Body uniform in consistence. - Pseudopods protruded from any point. - 2. _Protoplasta:_--Outer protoplasm slightly firmer in consistence. - Pseudopods protruded from any point. - (Often grouped with the _Rhizopods_.) - 3. _Radiolaria:_--Possessing a central membranous capsule. - Usually supported by a flinty skeleton. - 4. _Infusoria:_--Outer protoplasm firmer and denser; therefore - of more definite shape. - Possess permanent threadlike extensions of protoplasm - instead of pseudopods. - -We shall now observe the principal marine members of the protozoa, -commencing with the lowest forms, and dealing with each in its proper -zoological order as expressed in the above table. - - - MARINE RHIZOPODS - -When we stand on a beach of fine sand on a very calm day watching the -progress of the ripples over the sand as the tide recedes we frequently -observe whitish lines marking the limits reached by the successive -ripples as they advance toward the shore. If, now, we scrape up a little -of the surface sand, following the exact course of one of these whitish -streaks, and examine the material obtained by the aid of a good lens, we -shall in all probability discover a number of minute shells among the -grains of sand. - -These shells are of various shapes--little spheres, discs, rods, -spirals, &c.; but all resemble each other in that they are perforated -with a number of minute holes or _foramina_. They are the skeletons of -protozoons, belonging to the class _Rhizopoda_, and they exist in -enormous quantities on the beds of certain seas. - - [Illustration: FIG. 54.--A GROUP OF FORAMINIFERS, MAGNIFIED] - -We will first examine the shells, and then study the nature of the -little animals that inhabit them. - -The shells vary very much in general appearance as well as in shape. -Some are of an opaque, dead white, the surface somewhat resembling that -of a piece of unglazed porcelain; others more nearly resemble glazed -porcelain, while some present quite a vitreous appearance, much after -the nature of opal. In all cases, however, the material is the same, all -the shells consisting of carbonate of lime, having thus the same -chemical composition as chalk, limestones, and marble. - -If hydrochloric acid be added to some of these shells, they are -immediately attacked by the acid and are dissolved in a very short time, -the solution being accompanied by an effervescence due to the escape of -carbonic acid gas. - -The shells vary in size from about one-twelfth to one three-hundredth of -an inch, and consist either of a single chamber, or of many chambers -separated from each other by perforated partitions of the same material. -Sometimes these chambers are arranged in a straight line, but more -frequently in the form of a single or double spiral. In some cases, -however, the arrangement of chambers is very complex. - -We have already referred to the fact that the shells present a number of -perforations on the exterior, in addition to those which pierce the -partitions within, and it is this characteristic which has led to the -application of the name Foraminifera (hole-bearing) to the little beings -we are considering. - - [Illustration: FIG. 55.--A SPIRAL FORAMINIFER SHELL] - - [Illustration: FIG. 56.--A FORAMINIFER OUT OF ITS SHELL] - -The animal inhabiting the shell is exceedingly simple in structure, even -more so than the amoeba. It is merely a speck of protoplasm, -exhibiting hardly any differentiation--nothing, in fact, save a -contractile cavity (the _vacuole_), and numerous granules that probably -represent the indigestible fragments of its food. - -The protoplasm fills the shell, and also forms a complete gelatinous -covering on the outside, when the animal is alive; and the vacuole and -granules circulate somewhat freely within the semi-solid mass. Further, -the protoplasm itself is highly contractile, as may be proved by -witnessing the rapidity with which the animal can change its form. - -When the foraminifer is alive, it floats freely in the sea, with a -comparatively long and slender thread of its substance protruded through -each hole in the shell. These threads correspond exactly in function -with the blunt pseudopodia of the amoeba. Should they come in contact -with a particle of suitable food-material, they immediately surround -it, and rapidly retracting, draw the particle to the surface of the -body. The threads then completely envelop the food, coalescing as soon -as they touch, thus bringing it within the animal. - - [Illustration: FIG. 57.--THE SAME FORAMINIFER (FIG. 56) AS SEEN WHEN - ALIVE] - - [Illustration: FIG. 58.--SECTION OF THE SHELL OF A COMPOUND - FORAMINIFER] - -The foraminifer multiplies by fission, or by a process of budding. In -some species the division of the protoplasm is complete, as in the case -of amoebae, so that each animal has its own shell which encloses a -single chamber, but in most cases the 'bud' remains attached to a parent -cell, and develops a shell that is also fixed to the shell of its -progenitor. The younger animal thus produced from the bud gives rise to -another, which develops in the same manner; and this process continues, -the new bud being always produced on the newest end, till, at last, a -kind of colony of protozoons is formed, their shells remaining attached -to one another, thus producing a compound shell, composed of several -chambers, arranged in the form of a line or spiral, and communicating by -means of their perforated partitions. It will now be seen that each -'cell' of the compound protozoon feeds not only for itself, but for all -the members of its colony, since the nourishment imbibed by any one is -capable of diffusion into the surrounding chambers, the protoplasm of -the whole forming one continuous mass by means of the perforated -partitions of the complex skeleton. - - [Illustration: FIG. 59.--SECTION OF A NUMMULITE SHELL] - -Some of the simplest foraminifers possess only one hole in the shell, -and, consequently, are enabled to throw off pseudopods from one side of -the body only. In others, of a much more complex nature, the new -chambers form a spiral in such a manner that they overlap and entirely -conceal those previously built; and the development may proceed until a -comparatively large discoid shell is the result. This is the case with -_Nummulites_, so called on account of the fancied resemblance to coins. -Further, some species of foraminifera produce a skeleton that is horny -in character, instead of being calcareous, while others are protected -merely by grains of sand or particles of other solid matter that adhere -to the surface of their glutinous bodies. - - [Illustration: FIG. 60.--_Globigerina bulloides_, AS SEEN WHEN ALIVE, - MAGNIFIED] - -We have spoken of foraminifera as floating freely about in the sea -water, but while it is certain that many of them live at or near the -surface, some are known to thrive at considerable depths; and those who -desire to study the various forms of these interesting creatures should -search among dredgings whenever an opportunity occurs. Living specimens, -whenever obtained, should be examined in sea water, in order that the -motions of their pseudopods may be seen. - - [Illustration: FIG. 61.--SECTION OF A PIECE OF NUMMULITIC LIMESTONE] - -If we brush off fragments from the surface of a freshly broken piece of -chalk, and allow them to fall into a vessel of water, and then examine -the sediment under the microscope, we shall observe that this sediment -consists of minute shells, and fragments of shells, of foraminifers. In -fact, our chalk beds, as well as the beds of certain limestones, consist -mainly of vast deposits of the shells of extinct foraminifera that at -one time covered the floor of the sea. Such deposits are still being -formed, notably that which now covers a vast area of the bed of the -Atlantic Ocean at a depth varying from about 300 to 3,000 fathoms. This -deposit consists mainly of the shells of a foraminifer called -_Globigerina bulloides_, a figure of which is given on the opposite -page. - -The structure of chalk may be beautifully revealed by soaking a small -piece of the rock for some time in a solution of Canada balsam, allowing -it to become thoroughly dry, and then grinding it down till a very thin -section is obtained. Such a section, when viewed under the low power of -a compound microscope, will be seen to consist very largely of minute -shells; though, of course, the shells themselves will be seen in -section only. - -The extensive beds of nummulitic limestones found in various parts of -South Europe and North Africa are also composed largely of foraminifer -shells, the most conspicuous of which are those already referred to as -nummulites--disc-shaped shells of a spiral form, in which the older -chambers overlap and hide those that enclose the earlier portion of the -colony. - -Before concluding our brief account of these interesting marine -protozoons, it may be well to point out that, although the foraminifera -belong to the lowest class of the lowest sub-kingdom of animals, yet -there are some rhizopods--the _Monera_, which are even simpler in -structure. These are mere specks of undifferentiated protoplasm, not -protected by any shell, and not even possessing a nucleus, and are the -simplest of all animal beings. - -The second division of the Protozoa--the class _Protoplasta_--has -already received a small share of attention, inasmuch as the amoeba, -which was briefly described as a type of the whole sub-kingdom, belongs -to it. - -The study of the amoeba is usually pursued by means of specimens -obtained from fresh-water pools, and reference has been made to it in a -former work dealing particularly with the life of ponds and streams; but -it should be observed that the amoeba inhabits salt water also, and -will be frequently met with by those who search for the microscopic life -of the sea, especially when the water examined has been taken from those -sheltered nooks of a rocky coast that are protected from the direct -action of the waves, or from the little pools that are so far from the -reach of the tides as to be only occasionally disturbed. Here the -amoeba may be seen creeping slowly over the slender green threads of -the confervae that surround the margin of the pool. - -The third class--_Radiolaria_--is of great interest to the student of -marine life, on account of the great beauty of the shells; but, as with -the other members of this sub-kingdom, a compound microscope is -necessary for the study of them. - -The animals of this group resemble the foraminifers in that they throw -out fine thread-like pseudopods, but they are distinguished from them by -the possession of a membranous capsule in the centre of the body, -surrounding the nucleus, and perforated in order to preserve the -continuity of the deeper with the surrounding protoplasm. They have -often a central contractile cavity, and further show their claim to a -higher position in the animal scale than the preceding classes by the -possession of little masses of cells and a certain amount of fatty and -colouring matter. - - [Illustration: FIG. 62.--A GROUP OF RADIOLARIAN SHELLS, MAGNIFIED] - -Some of the radiolarians live at or near the surface of the ocean, while -others thrive only at the bottom. The former, in some cases, appear to -avoid the light, rising to the surface after sunset; and it is supposed -that the phosphorescence of the sea is due in part to the presence of -these animals. The latter may be obtained from all depths, down to -several thousand fathoms. - -The beauty of the radiolarians as a class lies in the wonderful shells -that protect the great majority of them. These shells are composed not -of carbonate of lime, as is the case with foraminifers, but of silex or -silica, a substance that is not acted on by the strongest mineral acids. -They are of the most exquisite shapes, and exhibit a great variety of -forms. Some resemble beautifully sculptured spheres, boxes, bells, cups, -&c.; while others may be likened to baskets of various ornamental -design. In every case the siliceous framework consists of a number of -clusters of radiating rods, all united by slender intertwining threads. - -It is not all the radiolarians, however, that produce these beautiful -siliceous shells. A few have no skeleton of any kind, while others are -supported by a framework composed of a horny material, but yet -transparent and glassy in appearance. - -The sizes of the shells vary from about one five-hundredth to one half -of an inch; but, of course, the larger shells are those of colonies of -radiolarians, and not of single individuals, just as we observed was the -case with the foraminifers. - -Those in search of radiolaria for examination and study should, whenever -possible, obtain small quantities of the dredgings from deep water. -Material brought up by the trawl will often afford specimens; but, -failing these sources of supply, the muddy deposit from deep niches -between the rocks at low-water mark will often provide a very -interesting variety. - -Place the mud in a glass vessel, and pour on it some nitric acid -(aqua-fortis). This will soon dissolve all calcareous matter present, -and also destroy any organic material. A process of very careful washing -is now necessary. Fill up the vessel with water, and allow some time for -sedimentary matter to settle. Now decant off the greater part of the -water, and repeat the process several times. By this means we get rid of -the greater part of the organic material, as well as of the mineral -matter that has been attacked by the acid; and if we examine the final -sediment under the microscope, preferably in a drop of water, and -covered with a cover-glass, any radiolarians present will soon reveal -themselves. - -It is often possible to obtain radiolarian shells, as well as other -siliceous skeletons, through the agency of certain marine animals. The -bivalve molluscs, for example, feed almost entirely on microscopic -organisms; and, by removing such animals from their shells, and then -destroying their bodies with aqua-fortis, we may frequently obtain a -sediment composed partly of the skeletons referred to. - -There remains one other class of protozoons to be considered, viz. the -_Infusorians_--the highest class of the sub-kingdom. In this group we -observe a distinct advance in organisation; for, in the first place, the -infusorians are enclosed in a firm cuticle or skin, which forms an -almost complete protective layer. Within this is a layer of moderately -firm protoplasm, containing one or more cavities that contract at -intervals like a heart. Then, in the interior, there is a mass of softer -material with cavities filled with fluid, two solid bodies, and numerous -granules. - - [Illustration: FIG. 63.--THREE INFUSORIANS MAGNIFIED] - -In these creatures we find, too, a distinct and permanent mouth, usually -funnel-shaped, leading to the soft, interior substance, in which the -food material becomes embedded while the process of digestion proceeds. -Here, then, for the first time, we meet with a special portion of the -body set apart for the performance of the work of a stomach; and, -further, the process of digestion being over, the indigestible matter is -ejected through a second permanent opening in the exterior cuticle. - -Again, the infusorian does not move by means of temporary pseudopods, as -is the case with the lower protozoons, but by means of minute hair-like -processes which permanently cover either the whole of the body, or are -restricted to certain portions only. These little processes, which are -called _cilia_, move to and fro with such rapidity that they are hardly -visible; and, by means of them the little infusorian is enabled to move -about in its watery home with considerable speed. - -In some species a few of the cilia are much larger than the others, and -formed of a firmer material. These often serve the purpose of feet, and -are also used as a means by which the little animal can anchor itself to -solid substances. - -As with the lower protozoons, the infusoria multiply by division; but, -in addition to this, the nucleus may sometimes be seen to divide up into -a number of minute egg-like bodies, each of which, when set free, is -capable of developing into a new animal. Should the water in which -infusorians have been living evaporate to dryness, the little bodies -just mentioned become so many dust particles that may be carried away by -air currents; but, although dry, they retain their vitality, and develop -almost immediately on being carried into a suitable environment. - -Infusorians are so called because they develop rapidly in infusions of -various vegetable substances; and those who desire to study their -structure and movements with the aid of a microscope cannot do much -better than make an infusion by pouring boiling water on fragments of -dried grass, and leaving it exposed for a few days to the warm summer -atmosphere. The numerous germs floating in the air will soon give rise -to abundance of life, including several different species of infusoria, -varying from 1/30 to 1/2000 of an inch in length. - -Fresh-water pools and marshes provide such an abundance of infusoria -that the animals are generally obtained for study from these sources, -and a few of the common and most interesting species inhabiting fresh -water have already been described in a former work. Nevertheless, the -sea is abundantly supplied with representatives of the class, and it is -certain that the beautiful phosphorescence sometimes observed in the sea -at night is in part due to the presence of luminous infusoria, some of -which appear to have an aversion to sunlight, retiring to a depth during -the day, but rising to the surface again after sunset. - - [Illustration: FIG. 64.--A PHOSPHORESCENT MARINE INFUSORIAN - (_Noctiluca_), MAGNIFIED] - - - - - CHAPTER VIII - - _BRITISH SPONGES_ - - -It seems to be the popular opinion that sponges are essentially natives -of the warmer seas, and it will probably be a surprise to many young -amateur naturalists to learn that there are about three hundred species -of this sub-kingdom of the animal world to be found on our own shores. -It must not be thought, however, that they are all comparable with the -well-known toilet sponges in regard to either size or general form and -structure, for some of them are very small objects, no larger than about -one-twentieth of an inch in diameter, and some form mere incrustations -of various dimensions on the surfaces of rocks and weeds, often of such -general appearance that they would hardly be regarded as animal -structures by those who have not studied the peculiarities of the group. - -Sponges are known collectively as the _Porifera_ or _Polystomata_, and -constitute a separate sub-kingdom of animals of such distinct features -that they are not readily confused with the creatures of any other -group. Their principal characteristic is expressed by both the group -names just given, the former of which signifies 'hole-bearing,' and the -latter 'many openings'; for in all the members of the sub-kingdom there -are a number of holes or pores providing a means of communication -between the body cavity or cavities and the surrounding water. Most of -these holes are very small, but there is always at least one opening of -a larger size at the anterior end. - -It will be seen from what we have just stated that sponges exhibit a -distinctly higher organisation than the _protozoa_ described in the last -chapter, inasmuch as they possess a permanent body-cavity that -communicates with the exterior; but in addition to this there are many -points of differentiation of structure that denote a superior position -in the scale of life. - -In order to ascertain the general features of a sponge we cannot do -better than select one of the simplest forms from our own shores. If we -place the live animal in a glass vessel of sea water, and examine it -with a suitable magnifying power, we observe a number of minute pores -scattered over its whole surface; and a much larger opening at the free -end. The animal is motionless, and exhibits no signs of life except that -it may contract slightly when touched. The water surrounding the sponge -also appears to be perfectly still, but if we introduce some fine -insoluble powder, such as precipitated chalk, or a drop of a soluble -dye, the motion of the suspended or soluble material will show that the -water is passing into the sponge through all the small pores, and that -it is ejected through the larger opening. - -On touching the sponge we observe that it is of a soft, gelatinous -consistence throughout, or if, as is often the case, the body is -supported by a skeleton of greater or less firmness, a gentle -application of the finger will still show that this framework is -surrounded by material of a jelly-like nature. This gelatinous -substance is the animal itself, and a microscopic examination will show -that its body-wall is made up of two distinct layers, the inner -consisting of cells, many of which possess a cilium or whip-like -filament that protrudes from a kind of collar, its free extremity -extending into the body-cavity. - - [Illustration: FIG. 65.--SECTION OF A SIMPLE SPONGE] - -These minute cilia are the means by which the water currents just -described are set up. By a constant lashing movement they urge the fluid -contained in the body-cavity towards the larger hole, thus causing the -water to flow in through the numerous small pores. This circulation of -sea water through the body-cavity of the sponge is the means by which -the animal is supplied with air and food. Air is, of course, absorbed -from the water by the soft material of the external layer of the body, -but the constant flow of fresh water through the body-cavity enables -this process of respiration to go on with equal freedom in the interior. -The mode of feeding of the sponge is very similar to that of the -_protozoa_. Organic particles that are carried into the body-cavity, on -coming in contact with the cells of the internal layer, are absorbed -into their protoplasm by which they are digested. Thus the sponge may be -compared to a mass of protozoon cells, all united into a common colony -by a more or less perfect coalescing of the cell-substance, some of the -units being modified in structure for the performance of definite -functions. The air and food absorbed by any one cell may pass readily -into the surrounding cells, and thus each one may be said to work for -the common weal. - - [Illustration: FIG. 66.--DIAGRAMMATIC SECTION OF A PORTION OF A - COMPLEX SPONGE] - -The description just given applies only to the simplest of the sponges, -and we have now to learn that in the higher members of the group the -structure is much more complicated. In these the surface-pores are the -extremities of very narrow tubes which perforate both layers of the -body-wall and then communicate with wider tubes or spaces within, some -of which are lined with the ciliated cells above described. These -spaces, which are sometimes nearly globular in form, and often arranged -in groups with a common cavity, communicate with wider tubes which join -together until, finally, they terminate in a large opening seen on the -exterior of the sponge. Hence it will be seen that the water entering -the minute pores of the surface has to circulate through a complicated -system of channels and spaces, some of which are lined with the ciliated -cells that urge the current onwards before it is expelled through the -large hole. Further, imagine a number of such structures as we have -described growing side by side, their masses coalescing into one whole, -their inner tubes and spaces united into one complex system by numerous -inter-communications, and having several large holes for the exit of the -circulating water, and you then have some idea of the general nature of -many of the more complex sponges to be found on our shores (see fig. -66). - - [Illustration: FIG. 67.--HORNY NETWORK OF A SPONGE, MAGNIFIED] - -But even this is not all, for as yet we have been regarding the sponges -as consisting of animal matter only, whereas nearly all of them possess -some kind of internal skeleton for the support of the soft, gelatinous -animal substance. The skeleton consists of matter secreted by certain -cells from material in the water and food, and is either horny, -calcareous, or siliceous. The horny skeleton is formed of a network of -fibres of a somewhat silky character, and often, as in the case of the -toilet sponges, highly elastic; but it is sometimes so brittle that the -sponge mass is easily broken when bent. The fibres of this framework -support not only the outer wall of the sponge, but also the walls of all -the internal tubes and spaces, which are often of so soft a nature that -they would collapse without its aid. - -The other forms of skeletons consist of minute bodies of carbonate of -lime or of silica, respectively, which assume certain definite shapes, -resembling stars, anchors, hooks, pins, spindles, &c., and are known as -_spicules_. Such spicules are usually present in those sponges that have -horny skeletons, but in others they form the entire skeleton. - -Sponges sometimes increase by division, a part being separated from the -parent mass and then developing into a complete colony; and they may be -reproduced artificially to almost any extent by this method, each piece -cut off, however small, producing a new sponge. They also increase by a -process of 'budding,' the buds produced sometimes remaining attached to -the original colony, thus increasing its size, but on other occasions -becoming detached for the formation of new colonies on a different site. -In addition to these methods of reproduction there are special cells in -a sponge that possess the function of producing eggs which are ejected -through the larger holes. The eggs are usually developed in the autumn, -and, after being ejected, swim about freely for a time, after which they -become fixed to rocks or weeds, and produce sponges in the following -year. The eggs may often be seen towards the end of the summer by -cutting through a sponge, or by carefully pulling it asunder. They are -little rounded or oval bodies, of a yellowish or brownish colour, -distinctly visible to the naked eye, occupying cavities in the interior. - -Sponges are classified according to the composition of the skeleton and -the forms of the spicules, the chief divisions being:-- - - 1. The CALCAREOUS Sponges (_Calcarea_). Skeleton consisting of - spicules of carbonate of lime in the form of needles and - three-or four-rayed stars. - - 2. The SIX-RAYED SPONGES (_Hexactinellida_). Skeleton of six-rayed - glassy spicules. - - 3. COMMON SPONGES (_Demospongia_). Skeleton horny, flinty, or - entirely absent. - -The first of these divisions contains about a dozen known British -species, which are to be found on the rockiest shores, attached to -stones, weeds, or shells, generally hidden in very secluded holes or -crevices, or sheltered from the light by the pendulous weeds. They -should be searched for at the lowest spring tide, particular attention -being given to the under surfaces of large stones, narrow, dark -crevices, and the roofs of small, sheltered caves. They may be readily -recognised as sponges by the numerous pores on the surface, though these -are often hardly visible without a lens, and the calcareous nature of -the skeleton may be proved by dropping a specimen into dilute -hydrochloric acid, when the carbonate of lime will speedily dissolve, -the action being accompanied by the evolution of bubbles of carbonic -acid gas. - -If calcareous sponges are to be preserved for future reference, they may -be placed in diluted spirit, in which case the animal matter, as well -as the mineral substance, will be preserved with but little alteration -in the natural appearance and structure. A specimen which has been -decalcified by means of acid, as above described, may also be preserved -in the same manner; and small portions of this will serve for the -microscopic study of the animal portion of the sponge. If the skeleton -only is required, the sponge is simply allowed to dry, when the soft -animal substance, on losing its contained water, will leave hardly any -residue; or, better, allow the calcareous sponge to macerate in water -for some days for the animal substance to decompose, and then, after a -few minutes in running water, set it aside to dry. - - [Illustration: FIG. 68.--_Grantia compressa_] - - [Illustration: FIG. 69.--SPICULES OF _Grantia_, MAGNIFIED] - -Small portions of the skeleton, examined under the microscope, will show -the nature of the calcareous spicules of which it is composed. These -consist of minute needles and stars, the latter having generally either -three or four rays. - -We give figures of three of the calcareous sponges of our shores, the -first of which (_Grantia compressa_) resembles little oval, flattened -bags, which hang pendulous from rocks and weeds, sometimes solitary, but -often in clusters. The smaller openings are thickly scattered over the -flat sides of the bag, and the larger ones, through which the water is -expelled, around the margin. When the sponge is out of the water and -inactive, the two opposite sides of the bag are practically in contact, -but, when active, the cavity is filled with water by means of the -whip-cells that line it, and the sides of the sponge are then more or -less convex. - - [Illustration: FIG. 70.--_Sycon ciliatum_] - -The ciliated sycon (_Sycon ciliatum_), fig. 70, though of a very -different appearance externally, is similar in structure to _Grantia_. -It is also found in similar situations, and is not uncommon on many -parts of the South Coast, from Weymouth westwards. The other example, -_Leucosolenia botryoides_, shown in fig. 71, is a branching calcareous -sponge, consisting of a number of tubes, all united to form one common -cavity which is lined throughout with whip-cells. It is usually found -attached to weeds. - - [Illustration: FIG. 71.--_Leucosolenia botryoides_, WITH PORTION - MAGNIFIED] - -Nearly all our British sponges belong to the group _Demospongia_--common -sponges; but the members of this group present a great variety of form -and structure. Most of them have a skeleton consisting of siliceous -spicules, but some have a horny skeleton, somewhat after the nature of -that of the toilet sponges; and others, again, have fleshy bodies -entirely, or almost entirely, unsupported by harder structures. They are -sometimes known collectively as the _Silicia_, for the greater number of -them have skeletons consisting exclusively of siliceous matter, while -the so-called horny sponges usually have spicules of silica -intermingled with the horny substance, and even those which are -described as having no skeleton at all sometimes contain scattered -spicules of silex. - - [Illustration: FIG. 72.--_Chalina oculata_] - -As the spicules of sponges are in themselves beautiful objects, and are -important to the naturalist, inasmuch as they form a basis for the -classification of sponges, it is well to know by what means they may be -separated from the animal for microscopic examination. The separation is -based on the fact that nitric acid (aqua-fortis) will destroy organic -matter while it has not the slightest action on silica. In some of our -common horny sponges the fibres are so transparent that, when teased out -and placed under the microscope, the siliceous spicules may be seen -embedded within them, but the spicules, both in these and the fleshy -sponges, may be separated completely from the animal matter by putting a -fragment of the sponge in a test-tube, covering it with nitric acid, and -boiling it for a short time. The tube should then be filled up with -water and allowed to stand undisturbed for a time, after which the -liquid is poured off gently from the sediment. If the sediment is then -put under the microscope on a slip of glass, it will be seen to consist -of grains of sand, of which there is always a considerable amount in the -pores and cavities of a sponge, and the siliceous spicules. - -Among the common objects of the sea shore is the horny skeleton of the -sponge _Chalina oculata_, which is frequently washed on the beach by -the waves, especially after storms. This sponge is not likely to be seen -between the tide-marks except at the lowest spring tide, when it may be -found suspended in a sheltered crevice or cave. The skeleton consists of -a fine network of horny fibres, in the centre of which lie the spicules, -imbedded in the horny material. The spicules are short and straight, -tapering at both ends. - - [Illustration: FIG. 73.--_Halichondria panicea_] - -The Bread-crumb sponge (_Halichondria panicea_) is even more common, for -it is to be found on every rocky coast, encrusting weeds and rocks, -often considerably above low-water mark. It is of a yellowish or pale -greenish colour, and forms an incrustation varying in thickness from -one-twentieth of an inch to half an inch or more; and, like most -sponges, should be looked for in narrow crevices, under heavy growths of -weeds, or in other situations where it is protected from the light. -Sometimes its free surface is unbroken, except, of course, by the minute -pores, and, here and there, the larger openings that serve for the -outgoing currents; but when it is found encrusting a rock in patches of -considerable size, the larger holes all occupy the summit of a little -cone resembling a miniature volcano with its crater. This sponge is -easily removed from the rock with the aid of a blunt broad-bladed knife, -and retains its natural appearance to perfection if preserved in -methylated spirit. Its horny skeleton is of a very compact nature, and -the spicules are minute siliceous needles pointed at both ends. - -Rambling on the sea beach we frequently meet with old oyster and other -shells perforated by a number of circular holes about the size of a -pin's head or less, and chalk and limestone rocks also are seen -similarly bored. On breaking into or grinding down the substance we find -that the openings are the ends of channels that form a network of canals -and chambers, some of which are so near the surface that they are -covered by an exceedingly thin layer of the calcareous substance. These -canals and chambers form the home of the Boring Sponge (_Cliona_), -which, although a very soft-bodied animal, has itself excavated them. - - [Illustration: FIG. 74.--SPICULES OF _Halichondria_, MAGNIFIED] - - [Illustration: FIG. 75.--AN OYSTER SHELL BORED BY _Cliona_] - -The manner in which the _Cliona_ excavates such a complicated system of -passages in so hard a material has naturally raised a considerable -amount of curiosity, and those who have studied the matter are divided -in opinion as to whether the work is done by chemical or by mechanical -action. - -Some of those who advocate the chemical theory suppose that an acid -fluid is secreted by the sponge, and that the carbonate of lime forming -the shell or stone is thereby dissolved; but such advocates have, as -yet, failed to detect the presence of any acid substance in the body of -the animal. Others ascribe the action to the solvent power of carbonic -acid gas. This gas certainly has the power of dissolving carbonate of -lime, as may be proved by a very simple experiment: Pour a little lime -water into a glass, and blow into it through a glass tube. The lime -water speedily becomes milky in appearance, the lime having been -converted into particles of chalk or carbonate of lime by union with the -carbonic acid gas from the lungs. Continue to blow into the liquid for -some time, and the carbonate of lime will slowly disappear, being -gradually dissolved by the excess of the gas--the gas over and above -that required for the formation of the carbonate. Thus, it has been -said, the carbonic acid gas evolved as a product of the respiration of -the sponge is the agent by which the channels are excavated. Whatever be -the acid to which this power is ascribed, whether it be the carbonic -acid or a special acid fluid secreted for the purpose, there is still -this difficulty in the way of accepting the theory, namely, that an -acid, though it has the power of dissolving the mineral matter of a -shell--the carbonate of lime--has no action on the laminae of animal -substance that form part of the structure. If we put the shell of a -mollusc in hydrochloric or _dilute_ nitric acid, we obtain, after the -complete solution of the carbonate of lime, a substantial residue of -animal matter which the acid does not touch, but in the case of _Cliona_ -both animal and mineral substances yield to its power. - - [Illustration: FIG. 76.--SPICULES OF _Cliona_] - -Those who favour the mechanical theory assert that the material is worn -away by siliceous particles developed by the sponge, and kept in -constant motion as long as the animal lives; and the theory is supported -by the statement that, in addition to the spicules of silica, which are -pin-shaped, and occupy the interior of the animal, there are little -siliceous granules scattered on the surface of the sponge which are kept -in constant motion resembling that of cilia; and the minute particles of -carbonate of lime that form a dusty deposit within the galleries are -supposed to be the product of the rasping or drilling action of these -granules. - -The pin-shaped spicules of _Cliona_ may be obtained for microscopic -examination by breaking any old oyster shell that has formed its home, -and brushing out the dust from the galleries; or, a part of the shell -may be dissolved in acid, and the sediment examined for spicules on a -slip of glass. - - - - - CHAPTER IX - - _THE COELENTERATES--JELLY-FISHES, ANEMONES, - AND THEIR ALLIES_ - - -One of the most interesting groups of marine life is that including -jelly-fishes and anemones. In it are the pretty little sea firs, so -often mistaken for sea-weeds by the youthful admirers of these plants, -who almost always include them in their collection of marine _algae_; the -transparent, bell-shaped jelly-fishes, which may often be seen in -thousands during the summer, carried by the tides, and swimming gently -by graceful contractions of their bells; and, most beautiful of all, the -lovely anemones--the 'sea flowers' of the older naturalists, by whom -they were regarded as forms of vegetable life. - - [Illustration: FIG. 77.--THREAD CELLS OF A COELENTERATE, MAGNIFIED - 1. Thread retracted 2. Thread protruded] - -The simplest animals of this group are minute jelly-like creatures, of a -more or less cylindrical form, usually fixed at one end, and having a -mouth at the other. The body is a simple hollow cylinder, the wall of -which is made up of two distinct layers, while the cavity within serves -the purpose of a stomach. The mouth is surrounded by a circle of arms or -tentacles by means of which the creature is enabled to capture its prey. -These arms are capable of free movement in every direction, and can be -readily retracted when the animal is disturbed. They are also armed with -minute oval, hollow cells, each of which has a slender filament coiled -up into a spiral within its cavity. Each filament is capable of being -suddenly protruded, thus becoming a free whip-like appendage, and these -are so numerous as to be very effectual in seizing and holding the -living beings on which the animal feeds. This would undoubtedly be the -case even if they were capable of mechanical action only, but, in many -instances at least, they seem to be aided by the presence of some -violent irritant, judging from the rapidity with which the struggling -prey is paralysed when seized, especially in the case of some of the -larger members of the group. - -The simple forms referred to increase by a process of budding, the buds -appearing first as simple swellings on the side of the parent creature, -and afterwards developing a mouth and tentacles, thus becoming exactly -like the adult form. Clusters of eggs also are developed in the outer -layer of the body-wall, and these are set free at intervals, and -produce new individuals. These animals possess no blood system of any -kind, and have no special organs for respiration, but the nutrient -matter absorbed from the body-cavity permeates the soft structures of -the flower-like body, and the oxygen required for respiratory purposes -is readily absorbed from the surrounding water. - - [Illustration: FIG. 78.--THE SQUIRREL'S-TAIL SEA FIR (_Sertularia - argentea_), WITH A PORTION ENLARGED] - -The higher coelenterates differ in certain particulars from the lower -forms just referred to. Thus, they frequently have a large number of -tentacles around the mouth, often arranged in several distinct whorls. -They have also a stomach separate from the general body-cavity, but -communicating with the latter below; and the body-cavity is divided into -compartments by a number of radiating partitions. Some, also, develop a -hard, stony skeleton by secreting carbonate of lime obtained from the -water in which they live. - - [Illustration: FIG. 79.--_Sertularia filicula_] - -We often see, when collecting on the beaches of rocky coasts, and -especially after storms, a number of vegetable-like growths, of a -greyish or brownish colour, each consisting of one or more main stalks -bearing a number of delicate branches. Some of them, by their peculiar -mode of growth, have suggested the name of sea firs, and a few of these, -together with other animals of the same group, may readily be recognised -by the accompanying illustrations. They are the objects already referred -to as being commonly included in collections of sea-weeds by young -naturalists, but they are in reality the horny skeletons of colonies of -coelenterates of the simplest type, belonging to the division -_Hydrozoa_. - - [Illustration: FIG. 80.--_Sertularia cupressina_] - -If we examine them with a lens we find that there are little cup-like -bodies projecting from each portion or branch of the stem-like -structure, and that the stem itself is hollow, with a communicating pore -at the base of each cup. This constitutes the skeleton only of the -colony--the dead matter, so to speak, which persists after the living -creatures have perished; but if the specimens collected have been -obtained fresh from the sea, placed in a glass of sea water, and then -examined with the aid of a lens, little jelly-like _hydroids_ or -_polypites_ will be seen to protrude from the cups, and extend their -short arms in search of food. - - [Illustration: FIG. 81.--THE HERRING-BONE POLYPE (_Halecium - halecinum_)] - -Each of the little creatures has a tubular stalk which passes through -the hole at the base of the cup, and is continuous with a tube of -gelatinous material in the interior of the horny stem, and thus each -member of the colony is directly connected with all the others, so that -any nutrient matter collected and digested by one member may be absorbed -into the central tube for the nourishment of the entire company of -little socialists, the activity of the one being thus made to compensate -for the laziness or incompetency of others. And this provision seems to -be absolutely necessary for the well-being of the colony as a whole, for -a close examination will often show that a kind of division of labour -has been established, since it includes two or three distinct kinds of -polypites, each adapted for the performance of a certain function. Thus, -in addition to the feeding or nutritive members of the community, there -are some mouthless individuals whose sole function seems to be the -production of eggs for the propagation of the species, while others, -also mouthless, develop an enormous number of stinging cells, probably -for the protection of the whole community against its enemies, and these -must therefore be provided, as we have seen they are, with a means by -which they may derive nourishment through the agency of the feeding -polypites. - - [Illustration: FIG. 82.--_Tubularia indivisa_] - - [Illustration: FIG. 83.--THE BOTTLE BRUSH (_Thuiaria thuja_)] - -When the eggs are liberated from what we may call the reproductive -members, they are carried away by the currents or tides, and soon -develop into little _larvae_ which are very unlike the parent, since they -are covered with minute vibratile cilia by means of which they can swim -freely. This they do for a period, and then settle down, lose their -cilia, become stalked, and thus constitute the foundation of a new -colony. A tubular stalk grows upward from its root, new members are -added as outgrowths or buds from their progenitor, and so the growth -proceeds until an extensive colony of hundreds of individuals has been -formed. - -We have spoken of the hydroid communities as being washed up on the -beaches of our rocky coasts, but the collector of these interesting -objects should not depend on such specimens for purposes of study. It is -undoubtedly true that splendid examples of the sea firs and their allies -are frequently washed up by the waves, including some species that -inhabit deep water, and which are, consequently, not to be found by the -ordinary collector in their proper habitat, and that these may often be -secured with the polypites still alive; but several species are to be -obtained between the tide-marks, especially at extreme low water, -growing on rocks, weeds, and shells; and we have often met with good -specimens, still alive, attached to the shells of whelks, scallops, &c., -in fishmongers' stores, even in inland towns. - - [Illustration: FIG. 84.--_Antennularia antennia_] - -Sometimes individual polypites become detached from a colony, and -develop into little umbrella-shaped jelly-fishes, about a fifth of an -inch in diameter; and these float about freely, keeping themselves near -the surface by rhythmic contractions of their 'bells,' the margins of -which are fringed by numerous fine tentacles. The mouth is situated -centrally on the under side, and is surrounded by a circular canal from -which proceed radiating tubes; and pigmented spots, supposed to be -rudimentary eyes, are formed round the edge. These little bodies are -called _Medusoids_, and may frequently be seen floating round our coasts -towards the end of the summer. In the water they are almost invisible on -account of the extreme transparency of their bodies; but if a muslin -net be drawn through the water from the stern of a boat, and the net -then gently turned inside out in a vessel of sea water, a number of -medusoids may be obtained for examination. These creatures produce eggs -which yield small ciliated larvae that swim about freely for a time, and -then settle down and establish stalked colonies as previously described. - -The larger jelly-fishes or _Medusae_ so frequently seen floating in -enormous numbers near the surface of the sea during the summer months -are allied to the medusoids. Their bodies are so soft that it is a -difficult matter to remove them from the water without injury, and when -removed their graceful forms are completely destroyed by the pressure of -their own weight. When left stranded on the beach, as is often the case, -they seem to dissolve almost completely away, so readily does the soft -animal tissue disintegrate in the large proportion of water, which forms -about 95 per cent. of the weight of the whole body. - -Those who desire to examine the nature and movements of the medusae will -find it necessary to observe them in water. The creatures may be lifted -out of the sea in a vessel placed below them, and then transferred to a -glass tank or a still rock pool by submerging the vessel and allowing -them to float out. It will then be observed that the mouth is situated -at the summit of a tube that projects from the middle of the under side -of the 'bell,' and is surrounded by lobed or frilled lips. Marginal -tentacles also generally fringe the edge of the bell, projecting -downwards into the water. Round the circumference of the body may be -seen a circular canal, from which several tubes converge towards, and -communicate with, the cavity of the stomach. - -When a medusa is inactive, its body gradually sinks to the bottom, being -usually slightly heavier than the water in which it lives; but it is -enabled to keep afloat by those rhythmic contractions of the bell with -which we are so familiar. It seems that the medusae are very sensitive to -various external conditions, for they frequently disappear -simultaneously from the surface water, and as suddenly reappear in -shoals when the conditions are more favourable; but it is difficult to -understand the causes which give rise to these remarkable movements. - -The medusae are often termed the _Acalephae_--a word which signifies -'nettles,' and they are popularly known as sea nettles. They all possess -stinging cells, which are distributed most thickly in the tentacles, and -some of the larger species are undoubtedly able to produce an -impression on the bodies of unwary bathers, while almost all have the -power of paralysing the living prey on which they feed. - -By far the commonest of the jelly-fishes of our seas is the beautiful -blue medusa--_Aurelia aurita_. This species appears in enormous shoals -during the summer, and large numbers are washed upon flat, sandy -beaches. They vary in size from two or three inches to nearly a foot in -diameter, and may be recognised from our illustration. The 'bell' is -umbrella-shaped, and is so transparent that the stomach with its -radiating canals may be seen through its substance. Around the margin -there are little pigment spots which are supposed to be rudimentary -eyes, and little cavities, containing a clear fluid, that are thought to -serve the purpose of ears. - - [Illustration: FIG. 85.--_Aurelia aurita_] - -On the under surface may be seen the square mouth, furnished with four -long and graceful frilled lips, which are richly supplied with stinging -cells; also the four ovaries or egg-producing organs, rendered -conspicuous by their violet colouring. - -The life history of _Aurelia_ is most interesting. The eggs are produced -in pouches that communicate directly with the stomach-cavity, and these -give rise to little ciliated larvae that are ejected through the mouth, -and then swim about freely in the water for a time. After this they -settle at the bottom, lose their cilia, and become little cylindrical -jelly-fishes, fixed by a short stalk-like foot to rocks or weeds. -Numerous tentacles develop as the creatures increase in size, and a -number of transverse furrows appear at the surface. The furrows -gradually increase in depth until, at last, the body is broken up into -several star-like discs, each of which floats away and develops into a -new medusa. - - [Illustration: FIG. 86.--THE EARLY STAGES OF _Aurelia_] - -Other jelly-fishes, some of which are considerably larger than -_Aurelia_, frequent our seas, and are often to be seen stranded on the -beach. Two of these--_Rhizostoma_ and _Chrysaora_--are figured. Although -they differ considerably in form from the blue aurelia, they closely -resemble it in general structure and habits. - - [Illustration: FIG. 87.--_Rhizostoma_] - - [Illustration: FIG. 88.--_Chrysaora_] - -When strolling on flat, sandy beaches, especially in the spring and -early summer, we commonly see what appear to be little balls of -exceedingly transparent and glassy jelly, no larger than an ordinary -marble. If picked up and examined, we observe that they are not quite -spherical, but oval in form, with a little tubercle at one end, and -eight equidistant bands running from this to the opposite end, like the -meridians on a globe. - -This extremely beautiful little creature is one of the coelenterates, -belonging to the division _Ctenophora_, or comb-bearing jelly-fishes, so -called because they possess comb-like ciliated plates, and is called the -Globular Beroe (_Cydippe pileus_). - -The ctenophores are very active creatures, swimming freely in the open -seas by means of their numerous cilia; and, although of such delicate -structure, are very predaceous, devouring small crustaceans and other -marine animals. They are usually globular in form, but some are like -long ribbons, and almost all are remarkable for their wonderful -transparency, which renders them nearly invisible when floating in -water. They have not the power of stinging or paralysing their prey, as -the medusae have, but their fringed arms are provided with adhesive cells -by which they hold their prey tenaciously. - - [Illustration: FIG. 89.--_Cydippe pileus_] - -In order to observe the form and habits of the Beroe we transfer it to a -vessel of sea water, when it immediately displays its regular spheroid -form, and its eight rows of comb-like plates which form the meridians -before alluded to. Its mouth is situated on the little tubercle at what -we may call the lower pole, for it is the habit of the Beroe to swim in -an inverted position, and the digestive cavity may be seen through its -glassy body. - -At first no appendages of any kind are visible, but soon the animal -protrudes two long and exceedingly slender arms, fringed with slender -gelatinous threads, from two cavities, at opposite sides of the body, -into which they can be withdrawn. A close examination will also reveal -the rapid movements of the cilia of its combs, and it is remarkable that -these do not always work together, the animal being able to move any of -its plates independently, and to reverse their motion when occasion -requires. It has no tentacles corresponding with those of jelly-fishes -and anemones, but is assisted in the capture of its prey by its two long -arms, the chief use of which, however, seems to be that of a rudder for -steering. - -If the Beroe is left out of water for some time, the water which forms -such a large proportion of its body evaporates, leaving an almost -imperceptible residue of solid matter; and if left in water after it is -dead, its substance rapidly dissolves away, leaving not the slightest -trace of its presence. There seems to be no satisfactory way of -preserving this beautiful form of animal life. If placed in strong -spirit the water is rapidly extracted from its body, and its animal -substance shrivelled to a minute, shapeless mass; while in weak spirit -and in other fluid preservatives it becomes more or less distorted, and -deprived of its beautiful transparency, or else it disappears -altogether. - -We now come to the great favourites among the coelenterates--the -beautiful anemones-the animated flowers of the ocean, remarkable not -only for their lovely flower-like forms, but also for the great variety -of colour and of habits which they display. These, together with the -corals, form the division of the coelenterates known as the -_Zoantharia_, characterised by the possession of simple tentacles, the -number of which is a multiple of either five or six. The latter differ -from the former mainly in the power of secreting a calcareous skeleton -which remains attached by its base after the animal substance has -decayed. - -The expanded anemone exhibits a more or less cylindrical body, attached -by a suctorial base to a rock or some other object, and a broad circular -disc above. In the centre of this disc is the mouth, surrounded by the -tentacles, often very numerous, and arranged in one or more whorls. When -the animal is inactive the tentacles are usually completely withdrawn, -and the body contracted into a semiglobular or pear-shaped mass which is -very firm to the touch. - -The general internal structure of an anemone may be made out by simple -dissections, and the examination conducted with the specimen submerged -in water. A longitudinal section will show that the body is a double -tube, the outer being formed by the body-wall, and the inner by the -wall of the stomach. Thus there is a body-cavity distinct from that of -the stomach, but the two will be seen to communicate below, since the -stomach-wall does not extend as far down as the base. It will be seen, -too, that the body-wall is made up of two distinct layers--an outer -one, that is continued inward at the mouth to form the inner wall of the -stomach, and an inner one that lines the whole of the body-cavity. The -latter contains the muscular elements that enable the anemone to -contract its body. - -When the animal is expanded, the whole interior is filled with sea -water, as are also the tentacles, which are hollow tubes, really -extensions of the body-cavity, and formed by prolongations of the same -two layers that constitute the body-wall. As it contracts this water is -expelled, partly through the mouth, and partly through small openings -that exist at the tips of the tentacles. - - [Illustration: FIG. 90.--SECTION OF AN ANEMONE - _t_, tentacles; _m_, mouth; _s_, stomach; _b c_, body-cavity - _p_, mesentery; _o_, egg-producing organ] - -The outer layer of the body-wall is provided with stinging cells which -serve not only to protect the anemone from its enemies, but also to aid -it in the capture of its prey, for which latter purpose they are -distributed in much greater abundance in the tentacles. - -The body-cavity is divided into a number of communicating compartments -by means of vertical partitions running from the body-wall and -converging towards the centre of the cavity. These are called -mesenteries, and are extensions of the inner layer of the body-wall. -Five or six of these are larger than the others, extending from disc to -base, and are called _primary mesenteries_. Between these are an equal -number of smaller _secondary mesenteries_; and, sometimes, a third set -of still smaller _tertiary mesenteries_. - -These internal partitions are best displayed in a transverse section of -the body, which shows the double tube formed by the walls of the body -and the stomach, together with the wheel-like arrangement of the -mesenteries. At one time all animals that had a radial symmetry--the -regular arrangement of parts round a common centre--were grouped -together under the title of _Radiata_; but it has since been recognised -that the creatures of this group exhibited such a great diversity of -structure that they have been re-classified into two main divisions, one -of which constitutes the coelenterates which we are at present -considering, and the other containing such creatures as star fishes and -sea urchins. - - [Illustration: FIG. 91.--STINGING CELLS OF ANEMONE, HIGHLY MAGNIFIED - _a_ and _c_, with thread protruded; _b_, with cell retracted] - - [Illustration: FIG. 92.--DIAGRAMMATIC TRANSVERSE SECTION OF AN ANEMONE - _S_, stomach; _bc_, body-cavity; _m'_, _m''_, _m'''_, primary, - secondary, and tertiary mesenteries] - - [Illustration: FIG. 93.--LARVA OF ANEMONE] - -On the surface of the mesenteries of the anemone may be seen the ovaries -or egg-producing organs. These discharge the ova into the general -body-cavity, after which they are ejected through the mouth. The embryos -are minute jelly-like creatures that have an active existence, swimming -about freely in the ocean by means of vibrating cilia, but after this -period of activity they settle down and fix themselves, gradually -assuming the adult form common to the species. - -The habits of sea anemones are particularly interesting, and it will -well repay anyone to make a study of these animals in their natural -haunts as well as in the aquarium. The gentle swinging of the tentacles -when searching for food, the capture and disposal of the prey, the -peculiar modes of locomotion, and the development of the young, are -among the chief points of interest. As regards locomotion, the usual -method of moving from place to place is by an exceedingly slow gliding -of the base or 'foot'; and while some anemones are almost constantly on -the move, others hardly ever stir from the secluded niche in which they -have taken up their abode. - -Sometimes an anemone will detach itself from the rock, and drag itself -along, but very slowly, by means of its tentacles, sometimes inverting -its body and walking on its head, as it were, and though one may never -have the opportunity of witnessing this manoeuvre on the shore, we have -found it far from an uncommon occurrence in the aquarium. - -The natural food of anemones consists of small crustaceans, such as -shrimps, and crabs, molluscs, small fishes, and in fact almost every -kind of animal diet, and there need never be any difficulty in finding -suitable viands for species kept in captivity. It is really astonishing -to see what large morsels they can dispose of with the assistance of -their extensile mouths and stomachs. It is not even necessary, indeed, -that the morsel be so small as to be entirely enclosed by the walls of -its digestive cavity, for the anemone will digest one portion while the -other remains projecting beyond its mouth. Further, it will even attack -bodies which it cannot swallow at all, by protruding its stomach so as -to partially envelope them, and then digesting the portion enclosed. -Indigestible portions of its food, such as the shells of small molluscs, -are ejected through the mouth after the process of digestion has been -completed. - -We have already referred to the reproduction of sea anemones by means of -eggs, but it is interesting to note that they may also increase by a -division of the body into two or more parts, and that this division may -be either natural or artificial. - -If an anemone be cut into halves longitudinally, each half will develop -into a complete animal. If cut transversely, the upper portion will -almost always develop a new suctorial disc, and produce a new individual -complete in every respect; and it has been stated that the basal portion -of the divided animal will also, occasionally, produce a new disc and -tentacles. - -The natural division of the anemone has frequently been spoken of as by -no means an uncommon occurrence, but, as far as our experience of -captive anemones go, this mode of multiplication does not seem to take -place except as the result of some mechanical force applied, or as a -means by which the animal may relieve itself of a solid body that it is -unable to eject. Thus, on one occasion, when a stone had slipped so that -its narrow edge rested across the middle of the disc of a large -_Mesembryanthemum_, the animal, apparently unable to free itself from -the burden, simply withdrew its tentacles and awaited results. In a few -days two individuals were to be seen, one on either side of the stone, -both undoubtedly produced as the result of the pressure applied. This -instance seems to be exactly akin to artificial division, for it is far -more likely that the animal was severed by the simple pressure of the -stone than that it divided itself to be relieved of its burden. - -On another occasion an anemone that had almost entirely surrounded a -mussel on which it had been feeding, gradually released itself of the -shell by a longitudinal division of its body; but here, again, it is -probable that the fission was the result of pressure applied rather than -of any power on the part of the animal. - -A few of the British sea anemones are shown on Plates II. and III., and -although the coloured illustrations will probably suffice for purposes -of identification, yet a short description of each one represented may -be acceptable. - -The most common and most widely distributed species is undoubtedly the -familiar Beadlet (_Actinia mesembryanthemum_--Plate II., figs. 1, 2, 3), -which is to be found on every bit of rocky coast around the British -Isles, and even on some stony beaches where there are no standing rocks -between the tide-marks. - -The colour of this species is exceedingly variable, but the most -abundant variety is of a liver-brown colour, with crimson disc and -tentacles, brilliant blue spots round the margin of the disc, and a line -of bright blue around the base. In others the prevailing colour is deep -crimson, orange, yellowish brown, or green. Fig. 1 represents a variety -commonly known as the Strawberry Beadlet (_Fragacea_), which is -distinguished by its superior size, and in which the dark-red ground is -often conspicuously spotted with green. - -Two members of the same genus are also shown on Plate III. One of -these--_A. glauca_ (fig. 3)--is of a bluish-green colour; while the -other--_A. chiococca_ (fig. 4)--is bright scarlet, with deep crimson -disc and white spots round the disc. - - [Illustration: PLATE II. - - SEA ANEMONES - - 1, 2, 3, Actinia mesembryanthemum. - 4. Caryophyllia Smithii. - 5. Tealia crassicornis. - 6. Sagartia bellis. - 7. Balanophyllia regia. - 8. Actinoloba dianthus.] - -The general form of this genus is that of an expanded flower on a -short column; the name Beadlet is applied on account of the little -bead-like projections on the margin of the disc. The tentacles number -nearly two hundred in a fully grown individual, and are arranged in -several rows; but when the animal is disturbed and the tentacles -retracted, its form is almost hemispherical. - -It is interesting to note that _A. mesembryanthemum_ not only exists in -varieties distinguished by distinct colours, but that the same -individual will sometimes change its tint, as may be observed when it is -kept in the aquarium; and it may be mentioned, by the way, that it is -very easily reared in captivity, either in the natural or the artificial -salt water, for not only may the same individuals be kept alive for -years with only a moderate amount of attention, but their offspring may -be reared without difficulty. - -On Plate II. (fig. 8) are two illustrations of the beautiful _Actinoloba -dianthus_, which grows to a length of five or six inches, and is easily -distinguished by its expanded and frilled disc, its very numerous short -and slender tentacles, and its tall, pillar-like body. Its colour is -somewhat variable, being either salmon, flesh-colour, cream, white, red, -orange, or brownish; but whatever be the tint of the body and tentacles, -the margin of the mouth is always red or orange. When young it may -easily be mistaken for another species, as its disc is not then frilled, -and the tentacles are much fewer in number. - -This pretty anemone usually inhabits deep water, and is frequently -brought in, attached to shells and stones, by trawlers, but it may be -commonly observed in the dark crevices of rocks, a little above -low-water mark, where it is usually seen contracted into a ball, or even -so much flattened that it looks like a mere pulpy incrustation of the -rock. It is very common on the rocky coasts of Dorset, Devon, and -Cornwall, as well as in many parts of Scotland and Ireland. - -Like the Beadlet, it is easily kept alive in the aquarium, where it -commonly multiplies by natural division; but as it does not generally -expand in full daylight, its beauty is often better observed at night by -artificial light. - -On Plate II. (fig. 5) we have an illustration of the beautiful Dahlia -Wartlet (_Tealia crassicornis_), which may be readily recognised by its -thick, banded, horn-like tentacles, and the numerous little adhesive -warts that almost cover the surface of its body. - -This species is as abundant as it is beautiful, for it is to be found in -plenty on almost every rocky coast, where it may be seen in the rock -pools and in the crevices of rocks near low-water mark. The diameter of -its cylindrical body often reaches two or three inches, while the -expanded tentacles embrace a circle of four or five inches. Specimens -even much larger than this are sometimes obtained by dredging in deep -water. - - [Illustration: FIG. 94.--THE TRUMPET ANEMONE (_Aiptasia Couchii_), - CORNWALL; DEEP WATER] - -The 'Dahlia' is not so frequently seen by sea-side collectors as its -abundance would lead one to expect, and this is principally due to the -fact that it not only conceals itself in narrow and out-of-the-way -crevices and angles of rocks, but also that, on the retreat of the tide, -it generally covers itself with small stones, fragments of shells, &c., -held fast to its body by means of its numerous suckers. In this manner -it conceals its beauty so well that the sense of touch, as well as that -of sight, is necessary in determining its whereabouts. As a rule, -however, it does not resort to this method of concealment when it -inhabits deep water, or even a permanent rock pool between the -tide-marks, and thus it is in the latter home where one may expect to -see this sea flower in all its glory, for when permanently covered with -water it will seldom hide its crown, except when alarmed, or when in the -act of swallowing its food. - - [Illustration: FIG. 95.--_Peachia hastata_, S. DEVON] - -It should be noted, too, that the rock pool is the right place in which -to study the habits of this anemone, for it is not nearly so easy to -rear in the artificial aquarium as the species previously described, -and, moreover, it requires a great deal of food. We have found it live -longest in running water, kept cool, and frequently renewed by supplies -fresh from the sea. It may be fed on almost any, if not every, form of -animal life inhabiting a rock pool. A small fish or a prawn is perfectly -helpless when once it is seized by the creature's tentacles. Mussels, -winkles, limpets, &c., are eagerly swallowed, and the indigestible -shells disgorged after the animal substance has been dissolved by the -digestive fluid. Even the active shore crab, armed as it is with a coat -of mail and powerful pincers, is no match for its powerfully adhesive -tentacles; nor do the sharp spines of the prickly urchin preserve it -from so voracious a creature. - -The rocky coasts of Devon and Cornwall are the chief haunts of the -pretty 'Daisy Anemone' (_Sagartia bellis_), and here it is very abundant -in places. This species lives in holes and crevices of the rocks, its -body usually entirely hidden from view, but its dark brown disc, -intersected by bright red radiating lines, and fringed with numerous -small tentacles, fully exposed to view as long as it is submerged. The -length of its body is always adapted to the depth of the hole or crevice -in which the animal lives, and may vary from half an inch to two or -three inches, the diameter of the columns being greatest where the -length is least. - - [Illustration: FIG. 96.--_Sagartia pallida_, DEVON AND CORNWALL] - -Sometimes the 'Daisy' may be seen living a solitary life, having settled -down in a hole just large enough to accommodate it, but more commonly it -is seen in company with several others of its species, occupying a -crevice in a rock pool, and often so closely packed together that the -tentacles of each individual are intermingled with those of its -neighbours, thus exhibiting a more or less continuous cluster or line of -'flowers,' each disc being from one to two or three inches in diameter -when fully expanded. - -On account of the peculiar positions selected by this species, it is not -easily removed without injury, and hammer and chisel are almost always -necessary for its removal; but if it is obtained without injury, and -transferred to the indoor aquarium, but little difficulty will be found -in keeping it alive and in health. It is also very prolific, and a -single specimen placed in the indoor tank will frequently produce a -large number of young. - -The colour of _S. bellis_, like that of many of our anemones, is very -variable, but the species may easily be recognised by the radiating -lines of the disc, and the numerous small tentacles. One variety, -however, deviates considerably in form, colour, and habit from the -normal. It (Plate II., fig. 6) is of a dull yellow colour, and has a -much less graceful form; and, instead of living in the holes and -crevices of rocky coasts, where it would be washed by fresh sea water at -every tide, it inhabits the muddy and foetid waters of narrow inlets of -the sea in the neighbourhood of Weymouth. - - [Illustration: FIG. 97.--_Sagartia nivea_, DEVON AND CORNWALL] - -Three other species of the same genus are represented on Plate III. The -first of these--_Sagartia troglodytes_, sometimes called the -Cave-dweller (fig. 1)--though very variable in colour, may be known by -its barred tentacles, each with a black B-like mark near its base. It -lives in sheltered, sandy, or muddy hollows between the rocks on most -rugged coasts, often with its body entirely buried beneath the sediment; -or, if only partially buried, the projecting portion of the column -concealed by particles that adhere to its suckers. - -The column is usually of an olive colour, striped longitudinally with a -paler tint, and sometimes reaches a length of two inches, while the -diameter of the expanded 'flower' may even exceed this length. - -This anemone is not a very conspicuous object of the shore, since the -exposed portion of its column is usually more or less covered by -sedimentary matter, and the tentacles are generally of a tint closely -resembling that of the surrounding surface. Thus the anemone is -protected from its enemies by its peculiar habit and colouring, while at -the same time the spreading tentacles constitute an unseen but deadly -snare for the unwary victims that come within their range. - - [Illustration: FIG. 98.--_Corynactus viridis_, DEVON AND CORNWALL] - -This species is often difficult to secure without injury on account of -its preference for narrow chinks in awkward situations, but we have -found that it is sometimes easily removed by first clearing away the -surrounding debris, and then gently pushing it from its hold by means of -the finger-nail. It seems, in fact, that its base is occasionally quite -free from the underlying rock, being simply imbedded in sand or mud. In -other cases hammer and chisel are necessary to remove it from its snug -hole. - -If placed in the aquarium it should be allowed to get a foot-hold in a -suitable hole or crevice, which should be afterwards partially filled -with sand. It is not difficult to keep, and although not a showy -species, and having a decided preference for shady places, yet its -habits will be found interesting. - -The Orange-disked Anemone (_Sagartia venusta_) is represented in fig. 2 -of the same plate. It may be easily distinguished by its brilliant -orange-coloured disc, surrounded by white tentacles, which, when fully -expanded, commands a circle of from one to one and a half inches. -South-west Wales is said to be the headquarters of this pretty sea -flower, but we have found it abundant on parts of the north Devon coast, -especially in places between Ilfracombe and Lynton. Like the last -species, it may be termed a cave-dweller, for it delights to hide in -corners and crevices that are so overhung with rocks and weeds that the -light is never strong. - -Yet another species of this genus (_S. rosea_) is depicted in Plate -III., fig. 8. It has been termed the Rosy Anemone, from the brilliant -rosy tint of its numerous tentacles. The column is generally of a dull -brown colour, with suckers scattered over the upper portion, and the -flower reaches a diameter of an inch or more. This anemone may be seen -at rest on overhanging rocks near low-water mark when the tide is out, -its disc only partially hidden, and the tips of its bright tentacles -just exposed. It may be seen on many parts of the Devon coast, and is, -or, at least, was, abundant in localities near Brixham and Shaldon. - -On the same plate is an illustration (fig. 7) of one of the most -abundant and most interesting of our anemones. It is commonly known as -the Opelet, and its scientific name is _Anthea cereus_. Almost everyone -who has done a little collecting on the rocky shores of the south-west -of England, or on the shores of Scotland or Ireland, must have seen this -species, easily distinguished by its long, slender, smooth tentacles, -all of about equal length, and presenting a waxy appearance. These -appendages are usually green and tipped with pink, but sometimes pale -yellow or red, and are of such a length that they cover a circle of five -or six inches. - -This species is decidedly of social disposition, for a number may -generally be seen in a cluster, crowded closely together; and when we -see them, as we often do, occupying a little tide pool that contains -scarcely sufficient water to enable them to give free play to their -tentacles, and exposed for hours to the full blaze of the summer sun, we -naturally form the opinion that they ought to require no special care in -the indoor aquarium. And this is actually the case, for they thrive well -with but little trouble. - -Perhaps the chief interest attached to this anemone is the deadly nature -of its grip. The numerous long tentacles have considerable clinging -power throughout their length, and their paralysing power is very -considerable compared with that of many other species of the same size. -Even the human skin is more or less affected by the irritating influence -of this species, a sensation approaching to a sting being sometimes -produced, and the skin showing visible signs of the injury done. The -grip, too, is so tenacious that tentacles are sometimes torn off when -the hand is quickly withdrawn from their hold. - -Our next example is the Red-specked Pimplet (_Bunodes Ballii_), shown in -fig. 5 of Plate III., which has received its popular name on account of -the numerous longitudinal rows of red-specked warts that run down its -short yellow column, and other red spots on the column itself, between -the rows. Its tentacles are usually pale yellow or white, but sometimes -grey or greenish, and often tinged with pink. - - [Illustration: FIG. 99.--_Bunodes thallia_, WEST COAST] - -This anemone is common on some parts of the coasts of Hampshire, Dorset, -Devon, and Cornwall, as well as on the south coast of the Isle of Wight, -and may be found in secluded crevices of the rocks, or under the large -stones that are scattered on the beach. - -The Gem Pimplet (_Bunodes gemmacea_) is shown on the same plate (fig. -6). It is easily distinguished by the six conspicuous longitudinal rows -of large white warts, between which are several other rows of smaller -ones. The column is pink or brownish, and the thick tentacles are -conspicuously marked by light-coloured roundish spots. It is not -uncommon on the south-west coast of England, where it may be seen in the -rock pools and on the surfaces of rocks between the tide-marks. Both of -the species of _Bunodes_ above mentioned may be kept in the aquarium -without much trouble. - - [Illustration: PLATE III. - - SEA ANEMONES - - 1. Sagartia troglodytes - 2. Sagartia venusta - 3. Actinia glauca - 4. Actinia chiococca - 5. Bunodes Ballii - 6. Bunodes gemmacea - 7. Anthea cereus - 8. Sagartia rosea] - -All the anemones so far briefly described are quite devoid of any kind -of skeleton, the whole body being of a pulpy or leathery consistence, -but some of our British species develop an internal calcareous skeleton, -consisting of a hollow cylinder of carbonate of lime secreted by the -body-wall, and attached to the rock by means of a similar deposit formed -in the base, and also, within the cylinder, of a number of thin plates -attached to the skeleton of the body-wall and projecting inwards towards -the axis, thus resembling, in fact, the skeletons of a number of the -tropical corals with which we are familiar. The animals in question are -often collectively spoken of as British corals. - - [Illustration: FIG. 100.--_Bunodes gemmacea_, WITH TENTACLES - RETRACTED] - -One of the finest of these corals is the Devon Cup-Coral (_Caryophyllia -Smithii_), figured on Plate II. It may be found in many parts of Devon -and Cornwall, attached to the rocks between the tide-marks, often in -very exposed places, but is much more abundant in deep water. - -Its skeleton is white or pale pink, and very hard, and is in itself a -beautiful object. The animal surrounding this stony structure is of a -pale fawn colour, with a white disc relieved by a deep brown circle -round the mouth. The tentacles are conical, almost colourless and -transparent, with the exception of the deep-brown warts scattered -irregularly over them, and are tipped by rounded white heads. - -Of course a hammer and chisel are necessary for the removal of these -corals, but they are hardy creatures, and may be kept for a considerable -time in captivity. Their habits, too, are particularly interesting, and -two or more may sometimes be found with skeletons attached, suggesting -that branched arrangement so common in many of the corals from warmer -seas. - -Another of these stony corals (_Balanophyllia regia_) is shown on the -same plate. It is much smaller than the last species, but exceedingly -pretty. It is also much less abundant, being confined almost exclusively -to the coast of North Devon, and is seldom seen far above the lowest ebb -of the tide. - - [Illustration: FIG. 101.--_Caryophyllia cyathus_] - -Our few brief descriptions of British anemones and corals have been -confined to those species which appear in our coloured plates, but we -have interspersed here and there between the text a few illustrations -which will assist in the identification of other species and also help -to show what a rich variety of form is exhibited by these beautiful -creatures. Some of these inhabit deep water only and are consequently -beyond the reach of most sea-side observers during the ordinary course -of their work; yet they may often be seen in fishing villages, -especially in the south-west, where they are frequently brought in among -the haul of the trawlers, attached either to shells or stones; and live -specimens of these deep-sea anemones may even be seen on the shells of -whelks and bivalve molluscs in the fishdealers' shops of London and -other large towns. - - [Illustration: FIG. 102.--_Sagartia parasitica_] - -One of the species in question--the Parasitic Anemone (_Sagartia -parasitica_) is generally found on the shell of the whelk or some other -univalve; and, if removed from its chosen spot, it will again transfer -itself to a similar shell when an opportunity occurs. This interesting -anemone is usually seen among the dredgings of the trawler, but may be -occasionally met with on the rocky coasts of the south-west, at extreme -low-water mark. Though sometimes seen attached to stones, shells may -undoubtedly be regarded as constituting the natural home of the species, -and many regard the former position as accidental or merely temporary, -and denoting that the animal had been disturbed and removed from its -favourite spot, or that circumstances had recently rendered a change of -lodgings necessary or desirable. Further, the shell selected by this -anemone is almost always one that is inhabited by a hermit crab; and -this is so generally the case that the occasional exceptions to the rule -probably point to instances in which the occupant of the shell had been -roughly ejected during the dredging operations. - - [Illustration: FIG. 103.--THE CLOAK ANEMONE (_Adamsia palliata_) ON A - WHELK SHELL, WITH HERMIT CRAB] - -The peculiar habit of the anemone just referred to makes it an -interesting pet for the aquarium, for if removed from its natural home, -and placed in the aquarium with a hermit crab, it will, sooner or later, -as the opportunity occurs, glide from its hole on the stone or rock, and -transfer itself to its favourite moving home. - -It may be difficult at first to see what advantage can accrue to the -anemone by the selection of such a situation; and, moreover, it becomes -an interesting question as to whether the advantage is a mutual one. -Close observations may, and already have, thrown some light on this -matter, though it is probable that there still remains something to be -learnt concerning the relations which exist between the inside and -outside occupants of the portable house. - -It may be noticed that the anemone almost invariably takes up a position -on the same portion of the shell, and that, when fully expanded, its -mouth is usually turned towards that of the crab. This seems to be a -very favourable position for the anemone, since it is one that will -enable it to catch the waste morsels from the crab's jaws by its -expanded tentacles. But it is, perhaps, not so easy to suggest a means -by which the anemone can make an adequate return for free board thus -obtained. It is well to remember, however, that crabs are regarded as -such delicate morsels by fishes that we have already spoken of the value -of these crustaceans as bait; while the fact that sea anemones remain -perfectly unmolested in rock pools inhabited by most voracious fishes, -coupled with the fisherman's experience as to the absolute worthlessness -of anemones as bait, is sufficient in itself to justify the conclusion -that these creatures are very distasteful to fishes. This being the -case, it is possible that the hermit crab is amply repaid by the anemone -for its liberal board not only by partially hiding the crab from the -view of its enemies, and thereby rendering it less conspicuous, but also -by associating its own distasteful substance with that which would -otherwise be eagerly devoured. - -When the hermit grows too large to live comfortably in its shell, a -change of home becomes necessary, and it is interesting to observe that -the anemone living on the outside of the shell transfers itself at the -same time; and this is a matter of vital importance to the crab, since -it usually changes its lodging at the moulting period, at which time its -body is covered by a soft skin, and is then even more acceptable as prey -to the fishes. Thus the anemone accompanies its host, affording it -continued protection during the period of its greatest danger. - -Before leaving the coelenterates we must refer to one other form which, -though not often having its habitat between the tide-marks, is -nevertheless a very common object in the neighbourhood of fishing -villages, where the refuse from the nets used in deep water has been -thrown on the beach. We refer to the peculiar animal known to fishermen -as 'Dead Men's Fingers,' and to the naturalist as the _Alcyonium_. - -When seen out of water it is not by any means an inviting object, but is -apparently a mass of gristly matter, of a dirty yellowish or brownish -colour, sometimes flattened and shapeless, and sometimes lobed in such a -manner as to suggest the popular name so commonly applied. It is always -attached to some hard object, such as a stone or a shell, and is so -frequently associated with oyster shells that it is by no means an -uncommon object in the fishmonger's shop, from which we have often -obtained live specimens for the aquarium. - -When placed in sea water it gradually imbibes the fluid surrounding it, -becoming much swollen. Then little star-like openings appear, the -circumference of each of which protrudes so as to form a little -projecting tube. Finally, a crown of eight little tentacles is -protruded, and the mass, so uninteresting at first sight, reveals itself -as a colony of pretty polyps. - -In general structure the Alcyonium resembles the sea anemone, but the -firm body-wall of the colony is supported and protected to some extent -by the presence of minute spicules of carbonate of lime; and it is -interesting to note that while the tentacles of anemones and corals make -up a number that is a multiple of either five or six, those of the -Alcyonaria and the allied 'Sea pens' are always in multiples of four. - - - - - CHAPTER X - - _STARFISHES, SEA URCHINS, ETC._ - - -Still passing up the scale of animal life, we now come to the -_Echinodermata_--the other sub-kingdom which we have already referred to -as forming, with the Coelenterates, the old division of Radiata. The -term _Echinoderm_ signifies 'hedgehog skin,' and is applied to the group -on account of the fact that the majority of its species possess a skin -that is either distinctly spiny, or exhibits numerous more or less -defined prominences. This skin is also supported and hardened by the -deposit of little plates or spicules of carbonate of lime, all joined -together so as to form a kind of scaffolding or 'test' for the -protection of the animal; and this secretion of carbonate of lime is not -always confined to the outer skin, for, in some cases, it occurs in the -walls of the internal organs as well. - -Most of the animals of this sub-kingdom display a regular radiate -symmetry; that is, the parts of their bodies are arranged regularly -round a common axis, and the arrangement is usually a five-fold one, as -may be observed in the case of the common Five-fingered Starfish of our -coasts (see Plate IV.), and it is worthy of note that this radiate -disposition of parts is not merely external, but that, as in the case of -anemones and jelly-fishes, it also obtains within, and determines the -arrangement of the internal organs. Further, although this radiate -symmetry characterises the adult animals of the group we are -considering, yet some show a tendency towards bilateral symmetry (parts -arranged equally on two opposite sides of a common axis), while this is -the rule, rather than the exception, with the early stages or _larvae_ of -these creatures. Observe, for instance, the larva of the common Brittle -Starfish, the adult of which species exhibits an almost perfect radiate -symmetry, and we see something more than a mere trace of a two-sided -disposition. - -We have not to look far into the structure of any typical echinoderm to -see that it is a distinct advance on the anemones in the matter of -organisation. To begin with its digestive system--this consists of a -tube having no communication with the general body-cavity, but remaining -quite distinct throughout its length, with both ends communicating -directly with the exterior. Its nervous system also is more highly -developed, for it has a well-formed ring of nerve matter round the -mouth, from which pass two or three systems of nerve fibres, each system -having its own special function to perform. The sense organs, however, -do not appear to be well developed, though there exist certain 'pigment -spots,' in which nerve fibres terminate, and which are supposed to serve -the purpose of eyes. - - [Illustration: FIG. 104.--LARVA OF THE BRITTLE STARFISH] - -One of the most interesting features in connection with the echinoderms -is undoubtedly the structure and function of the apparatus for -locomotion. Examine a live sea urchin, or the common five-rayed -starfish, in a rock pool or aquarium, and it will be seen to possess a -large number of soft, flexible, and protrusible processes, each of which -terminates in a little sucking-disc that enables the animal to obtain a -good 'foot-hold;' and, having fixed itself on one side by means of a -number of these little 'feet,' it is enabled, by the contraction of -certain muscles, to pull itself along. - -The little feet we are examining are really tubes filled with water, and -capable of being inflated by the injection of water into them from -within the body of the animal. Each one communicates with a water tube, -several of which (usually five) radiate from a circular canal of water -that surrounds the mouth. This circular canal does not communicate with -the mouth, but with a tube, known as the 'stone canal' because of the -carbonate of lime deposited within its walls, that opens at the surface -of the body on the opposite side, and is guarded at the orifice by one -or more perforated plates through which water gains admission. Thus the -animal can fill its 'water system' direct from the sea, and, by the -contraction of muscles that surround the main canals, force this water -into the little 'tube-feet,' causing them to protrude and present their -sucking-discs to any solid object over which it desires to creep. We may -observe, however, that some of the little protrusible tubes have no -sucking-discs, and probably serve the purpose of feelers only; also, -that while these tube-feet are the principal means of locomotion in -certain species, in others the movements of the body are performed -almost exclusively by the five or more rays that extend from the centre -of the animal, and which are readily curved into any desired position by -the action of well-developed muscles. - -All the echinoderms come within the domain of the marine naturalist, for -no members of the sub-kingdom are inhabitants of fresh water; and it is -interesting to observe that, unlike the animals previously described, -none of them live in colonies. - -A general examination of the various starfishes to be found in our seas -will show that they may be divided into three distinct groups. One of -these contains the pretty Feather Stars, which are distinguished by -their long and slender 'arms,' usually ten or more in number, each of -which bears a number of pinnules that give it quite a feathered -appearance. The second includes the Brittle Stars, possessing five -slender arms that are jointed to the small, flattened, central disc, and -which are so named on account of the readiness with which the animal -falls to pieces when alarmed or disturbed; and the third is formed by -the remaining five-rayed stars, the arms of which, instead of being -jointed to, are continuous with, the centre of the body. - -All these starfishes have a leathery skin, supported and hardened by a -framework of calcareous plates, and presenting a number of hard ridges -or spines. In addition to the system of water tubes already mentioned as -characteristic of the echinoderms, they also possess a second circular -vessel round the mouth, from which a number of vessels are distributed -to the walls of the digestive tube. These, however, are bloodvessels, -and are directly concerned with the nutrition of the body. Some, also, -have imperfectly developed eyes at the ends of the arms or rays. - -Contrary to what one would expect after watching the somewhat sluggish -movements of starfishes, they are really very voracious creatures, -attacking and devouring molluscs and small crustaceans, sometimes even -protruding their stomachs to surround their prey when too large to be -passed completely through the mouth; and they are also valuable as -scavengers, since they greedily devour dead fishes and other -decomposible animal matter. - - [Illustration: FIG. 105.--LARVA OF THE FEATHER STAR] - -Feather Stars differ from other starfishes in that they are stalked or -rooted during one portion of their early life. At first they are little -free-swimming creatures, feeding on foraminifers and other minute -organisms that float about in the sea. Then they settle down and become -rooted to the bottom, usually in deep water, at which stage they are -like little stalked flowers, and closely resemble the fossil encrinites -or stone lilies so common in some of our rock beds, and to which they -are, indeed, very closely allied. After a period of this sedentary -existence, during which they have to subsist on whatever food happens to -come within their reach, they become free again, lose their stalks, and -creep about by means of their arms to hunt for their prey. - - [Illustration: FIG. 106.--THE ROSY FEATHER STAR] - -The commonest British species of these starfishes is the Rosy Feather -Star (_Antedon rosaceus_); and as this creature may be kept alive in an -aquarium for some considerable time without much difficulty, it will -repay one to secure a specimen for the observation of its habits. It is -not often, however, that the Feather Star is to be found above low-water -mark, its home being the rugged bottom under a considerable depth of -water, where a number usually live in company; but there is no -difficulty in obtaining this and many other species of interesting -starfishes in fishing towns and villages where trawlers are stationed, -for they are being continually found among the contents of the net. - -Although the Feather Star can hardly be described as an active creature, -yet it will cover a considerable amount of ground in the course of a -day, creeping over rocks and weeds by means of its arms, which are -raised, extended, and again depressed in succession, each one thus in -turn serving the purpose of a foot. These arms are capable of being -moved freely in any direction, as are also the little more or less rigid -pinnules appended to them. The latter are bent backwards on an extended -arm that is being used to pull the animal along, so that they form so -many grappling hooks that hold on the bottom; and then the arm in -question is bent into a curve by the contraction of its muscles, thus -dragging the body forward. The arms on the opposite side of the body are -also used to assist the movement by pushing it in the same direction, -and this is accomplished by first bending the arms, and then, after -curving the pinnules in a direction from the body, again extending them. -Other movements of the feather star are equally interesting. Thus, the -manner in which it will suddenly extend its arms and apply its pinnules -to the surface on which it rests in order to obtain a good hold when -alarmed, and the way in which it apparently resents interference when -one of the arms is touched, are worthy of observation. The arms -themselves are readily broken, and will continue to move for some time -after being severed from the body, but the loss to the animal is only -temporary, for a new arm grows in the place of each one that has been -broken off. - -This tendency to break into pieces is much greater in the Brittle Stars, -as might be expected from their popular name; and is, in fact, such a -marked characteristic of the group that it is not by any means an easy -matter to obtain a collection of perfect specimens. They will often snap -off all their arms, as if by their own power of will, when disturbed or -alarmed, and even when removed from their hold without injury, they will -frequently break themselves into pieces if dropped into spirit or in any -way subjected to a sudden change of conditions. - -The tube-feet of Brittle Stars are very small and are not provided with -suckers, but are very sensitive, serving the purpose of feelers; also, -having thin, permeable walls, they probably play a large part in the -process of respiration. Both arms and disc are hardened by a dense -scaffolding of calcareous plates; and not only are the former attached -to the latter by a well-formed joint, but the arms themselves are -constructed of a number of segments that are held together by a kind of -'tongue and groove' joint. Round the mouth are a number of tentacles -that are kept in constant motion with the object of carrying the food -towards it, and of holding the larger morsels while the act of -swallowing is progressing. - - [Illustration: FIG. 107.--THE COMMON BRITTLE STAR] - -The various species of Brittle Stars live among the rocks and weeds, -chiefly in deep water, where they move about by means of the muscular -contraction of their arms, the disc being raised on the curved arms as -the animal proceeds. Some species are to be found between the -tide-marks, and especially abundant on the south-west coast are two -small species that live among the tufts of coralline weeds, sometimes so -crowded together that dozens may be taken from a little patch of -coralline only two or three inches square. These have such small discs, -and such slender arms, and are, moreover, so well concealed by their -colouring, which closely resembles that of the weed-tuft they inhabit, -that they are only to be detected by close inspection. - -The remaining division of the starfishes, sometimes distinguished by the -name of Common Stars, possess five arms or rays, which may be either -long or short, and which are not jointed with the central disc, but -continuous with it; that is, there is no sharp line of demarcation -between arm and disc. One or two species are well known to all -frequenters of the sea-side, but the majority of them inhabit deep -water, where they creep about over the rocks and weeds, obtaining their -food from the bed below them. - -If we examine the common five-finger star that is so often stranded on -the beach, and so frequently found in rock pools between the tide-marks, -we see that each arm has a large and conspicuous groove running along -its centre on the under side, and on each side of these are the rows of -tube-feet, arranged in such a manner that they have suggested the -appearance of an avenue of trees on each side of a garden walk, and have -consequently earned the name of _ambulacrum_. These tube-feet may be -protruded for some distance; and, being provided with suckers that -possess considerable clinging power, they form the principal means of -locomotion. - -Put the starfish in the aquarium, or in a tidepool by the sea, and you -will find it very interesting to observe how the animal progresses, -while some idea of the clinging power of the tube-feet may be -ascertained by allowing the animal to creep over the submerged hand. - -The movements of the tube-feet may also be seen to advantage when the -starfish is laid upside down in a pool, and, what is still more -interesting, the manner in which the animal turns itself over. To do -this it will first bend the tips of one or two of its arms so as to -bring the suckers against the ground; and then, aided by the pulling -action of these, it will gradually bring other suckers into a similar -position till, at last, the whole body has been turned over. Some of our -common starfishes have rays so short that they may be termed angles -rather than arms, and these are unable to turn their inverted bodies by -the gradual method just described. They generally raise their bodies on -the tips of three or four of the rays, assuming somewhat the form of a -three-or four-legged stool, and then, bending the remaining one or two -arms over the body, they alter the position of the centre of gravity -till eventually the body topples over to the desired position. - -Some of the common five-rayed stars have no suckers on their tube-feet, -and consequently have to creep by means of the muscular contractions of -their arms; and several of them are like the brittle stars in breaking -up their bodies when irritated or seized. This latter peculiarity will -account for the frequency with which we come across animals with one or -more rays smaller than the others, the smaller rays being new ones that -have been produced in the place of those lost. Again, we sometimes meet -with such monstrosities as a five-rayed star with six or more rays, some -smaller than others, the smaller ones representing two or more that have -grown in the place of one that has been lost; or a starfish with -branched or forked arm, illustrating the tendency to produce a new arm -even when the original one has been only partially severed. - -A close observation of a starfish in water may enable us to detect a -number of little transparent processes standing out between the -prominences of the rough skin of the upper surface. These are little -bags filled with fluid, formed of such thin walls that gases can readily -pass through them, and are undoubtedly connected with the process of -respiration. Also, on the upturned extremity of each arm a red spot may -be seen; and this from the nature of its structure, and from its -association with the nervous system, has been regarded as a rudimentary -eye. - -On the upper side of the disc one may also observe a more or less -conspicuous spot of variable colour, on one side of the centre. It is a -plate, finely perforated, covering the outer extremity of a short canal -which communicates with the system of water tubes that were described in -the earlier part of this chapter. It is, in fact, the entrance through -which water is admitted into the central ring round the mouth, and from -this into the radial water tubes that run through each arm of the -starfish to supply the tube-feet. The short tube referred to is always -filled with sand, and thus the water that enters into the water-vascular -system is filtered before it reaches the circular vessel. It is -interesting to note, in this connection, that here is one respect in -which the radiate symmetry of the starfish is broken, there being only -one entrance, and that not a central one, by which water is distributed -into the five rays. - -Of course, when the ray of a starfish has been broken off the water -vessel or vessels that it contained are destroyed, as is also the -prolongation of the stomach, in the form of a long, blind tube, that -extended into it. But no inconvenience attaches itself to this loss, for -the starfish has the power of reproducing even its lost viscera, as well -as any of the five rays of the body that may be broken off. - -We must briefly refer to one other feature of the common star, viz. the -possession of small prehensile organs around the mouth. These are little -spines, the extremities of which are movable, and take the form of -little pincers by means of which the animal can hold its prey. - -When it is desired to preserve starfishes for future study, immersion in -diluted spirit or a solution of formaldehyde will answer all purposes, -the soft parts being thus preserved as well as the harder structures; -but it is usual to preserve them in a dry state when they are required -merely for purposes of identification, as is usually the case with the -specimens in an ordinary museum collection. In the latter case it is -advisable to put the starfishes in strong spirit for a few days, -changing the spirit if several specimens are put together, and then -drying them as quickly as possible in the open air. - - [Illustration: FIG. 108.--SECTION OF THE SPINE OF A SEA URCHIN] - -We have now to consider the Sea Urchins or Sea Eggs, which are readily -known by the hedgehog-like covering of hard spines. Externally they -appear as globular or heart-shaped bodies, the surface entirely hidden -by spines except, perhaps, the mouth on the under side, which is -provided with an apparatus for mastication. If alive, and in the water, -one may notice that the animal creeps along the bottom, mouth downwards, -moving itself either by means of its moveable spines, or by soft -tube-feet resembling those of starfishes, that are protruded between the -spines, or by both combined; and the movements of its masticating organ -may be seen by observing the animal through the side or bottom of a -glass vessel of sea water. The last-named organ is surrounded by an area -of soft skin, and is not present in all species. - -A closer examination of the common globular urchin will show that it is -wonderfully constructed. Even the spines, which are in themselves -uninteresting objects to the naked eye, are most beautifully formed, a -transverse section revealing a radiate or reticulated structure when -viewed through the microscope. Each spine has a concave base which fits -on a little tubercle of the calcareous shell or test that covers the -body of the animal, forming a perfect ball-and-socket joint, and is -capable of being moved in any direction by means of small muscular -bands. - - [Illustration: FIG. 109.--SEA URCHIN WITH SPINES REMOVED ON ONE SIDE] - -On removing the spines the shell is seen to completely enclose the -animal with the exception of the mouth, with its masticatory apparatus, -and the small area around it which is covered by the uncalcified skin -just referred to. - -At the very top of the shell, exactly opposite the mouth, there is a -small plate perforated by the extremity of the digestive tube. Round -this are five angular plates, each perforated by the ducts of the -ovaries or egg-producing glands, but one of these is enlarged and -further perforated, that it may serve the second purpose of allowing -water to enter the system of water tubes that supply the tube-feet, and -thus corresponds exactly with the plate already noticed on the upper -surface of the starfish. Between these are five smaller plates, each -with a rudimentary eye that receives a fine nerve-thread. - - [Illustration: FIG. 110.--APEX OF SHELL OF SEA URCHIN] - -The remaining and greater portion of the shell of the urchin is composed -of ten radiating segments, each of which is made up of two rows of flat -angular plates united at their edges. Five of these segments, arranged -alternately with the others, are perforated by numerous holes, through -which the tube-feet of the urchin are protruded, while the remainder -are imperforate; and all ten plates bear the little hemispherical -processes to which the spines are jointed. - - [Illustration: FIG. 111.--SHELL OF SEA URCHIN WITH TEETH PROTRUDING] - -One of the most interesting features of this urchin is undoubtedly its -complex and wonderful masticating system. There are five teeth, -symmetrically arranged, and all pointing towards the centre of the -mouth. Each is attached to a wedge-shape jaw, made up of several -pieces, and the whole apparatus is attached by ligaments to loops in the -interior of the shell, and is moved by no less than thirty distinct -muscles. The complete system may be readily dissected out, and is well -worthy of study and preservation. (The harder portions of the system may -often be found in the interior of the empty shell of an urchin after the -softer structures of the body have decayed away.) - - [Illustration: FIG. 112.--INTERIOR OF SHELL OR SEA URCHIN] - - [Illustration: FIG. 113.--MASTICATORY APPARATUS OF SEA URCHIN] - -An interesting dissection of the globular urchin may also be made by -cutting completely round the shell with a pair of sharp-pointed -scissors midway between the mouth and the apex, and then separating the -upper and lower halves, as shown in fig. 114. In this way the whole of -the digestive tube, with its numerous curves, may be traced from the -mouth to the anus at the opposite pole. The water-vessels that supply -the tube-feet in the regions of the five perforated plates may also be -seen, as well as the ovaries or egg-producing organs and the bases of -the five jaws with their complicated system of muscles. - -A little acquaintance with the commonest of the British sea urchins will -show that they may be divided into two well-defined groups, one -containing the globular or subglobular forms, of which the common sea -urchin or sea egg (_Echinus sphaera_) above described, is a type, as well -as the pretty little Green Pea Urchin (_Echinocyamus pusillus_), and the -little Purple-tipped Urchin (_Echinus miliaris_), which is found -principally on the west coast of Scotland; while the second group is -formed by the less symmetrical Heart Urchins, which differ from the -others in several interesting particulars of structure and habit. - - [Illustration: FIG. 114.--SEA URCHIN DISSECTED, SHOWING THE DIGESTIVE - TUBE] - -These heart urchins (Plate IV., fig. 4) are covered with short, delicate -spines which are not much used for purposes of locomotion, the animals -moving from place to place almost entirely by means of their tube-feet, -while the globular urchins travel principally by their spines, which are -stouter and more freely moved on well-formed ball-and-socket joints. -Also, while in the globular species the perforated plates that admit of -the protrusion of the feet are arranged with a perfect radiate symmetry, -those of the heart urchins are confined to one side of the shell; and -the digestive tube, which in the former terminates in the pole opposite -the mouth, in the latter ends close to the mouth itself. Further, the -heart urchins do not possess any kind of dental apparatus. - - [Illustration: PLATE IV - - ECHINODERMS - - 1. Asterias rubens - 2. Goniaster equestris - 3. Ophiothrix fragilis - 4. Echinocardium cordatum - 5. Echinus miliaris - 6. Echinus esculentus] - -The habits of sea urchins are interesting, and may be watched in the -aquarium, where the movements of the spines and of the tube-feet may -be seen perfectly. Some species are very inactive, living in holes and -crevices, or under stones, and seldom move from their hiding-places, -while others travel considerable distances. The former have generally no -eyes, and, instead of seeking their food, simply depend for their -subsistence on the material carried to them by the movements of the -water; while the latter possess visual organs similar to those observed -in certain starfishes. Some species also protect themselves from their -enemies when in the open by covering their bodies with sand, small -stones, shells, or weeds, and thus so perfectly imitate their -surroundings that they are not easily detected. The feet that are used -for purposes of locomotion terminate in suckers resembling those of the -common five-fingered starfish, and have considerable clinging power, but -some have either very imperfectly developed suckers or none at all, and -are probably used as feelers only. - -Sea urchins, like their allies the starfishes, generally inhabit deep -water beyond low-water mark, where they often exist in enormous numbers, -feeding on both animal and vegetable substances; but some species are -often to be met with between the tide-marks, where they may be seen -under stones, and frequently half hidden in mud. The globular species -occur principally on rocky coasts, but the heart urchins are more -commonly dredged from banks of sand or mud that are always submerged. - -The life-history of urchins closely resembles that of starfishes, for -the young are free-swimming creatures of an easel-like form, and during -this early larval existence their bodies are supported by a calcareous -skeleton. - -We will conclude our short account of the British echinoderms with a -description of the peculiar Sea Cucumbers, which belong to the division -_Holothuroidea_. These creatures are so unlike starfishes and urchins in -general appearance that the uninitiated would hardly regard them as -close relatives. The body is, as the popular name implies, -cucumber-shaped, with the mouth at one end, and the general aspect is -wormlike. There is, however, a radiate symmetry--a five-fold arrangement -of parts, though not so regular as in most echinoderms. Running -lengthwise along the body are five rows of tube-feet, but only two of -these are well developed and terminate in functional suckers; and, as -might be expected, the animal crawls with these two rows beneath it. The -feet are outgrowths of a system of water tubes similar to that of the -urchin, there being a circular tube round the mouth, from which branch -five radial tubes, one for each row. - -The mouth of the sea cucumber is surrounded by plumed tentacles which -can be retracted at will, and which are used in capturing the smaller -living things that form its food. Like the earthworm, it will often -swallow large quantities of sand, from which it digests the organic -matter contained. - -The body-wall of the _Holothuroidea_ is strong and muscular, and is -strengthened by the presence of numerous spicules of carbonate of lime, -often in the form of little anchors, wheels, and crosses, while the -outer surface is rough and slimy, and often of a colour so closely -resembling the surroundings of these animals that they are not easily -observed. This feature is one of great value to the creatures, since -they have no means of defence from their enemies, and seem to owe their -safety entirely to their protective colouring. - - [Illustration: FIG. 115.--THE SEA CUCUMBER] - -There are several species of sea cucumbers on our coasts, but all -inhabit deep water and are seldom to be seen above low-water level. They -are, as a rule, easily obtained from fishermen, who will bring them in -when requested to do so. Live specimens may be kept for a considerable -time in the indoor aquarium, and seem to prefer a rocky bottom on which -they can hide under stones at times, and a bed of sand on which they -will occasionally crawl. They will readily devour small molluscs and -crustaceans, and will partake of dead organic matter in a partially -decomposed state. - -The following tabular summary of the classification of Echinoderms may -possibly be of use for reference:-- - - SUB-KINGDOM _ECHINODERMATA_ - +-------------------------------------------+-------------+-------------+ - |Body star-shaped. |Body glob- |Body | - +------------+------------------------------+ ular, sub- | elongated, | - |Body |Body not stalked. | globular, | and covered | - | stalked, |Tube-feet used for locomotion.| or heart- | with a | - | at least |=Class:= _Stelleridae._ | shaped, | soft skin | - | during +--------------+---------------+ and cov- | containing | - | early |Arms jointed |Arms contin- | ered with | calcareous | - | stage. | to disc, and | uous | a con- | spicules. | - | Feet not | not contain- | with disc, | tinuous | | - | used for | ing prolong- | and contain- | shell. |=Class:= | - | loco- | -tions of the| ing processes | | _Holothu- | - | motion. | internal | of the |=Class:= | roidea_ | - | | organs | viscera. | _Echinoidea_| (Sea | - |=Class:= | | | (Sea Ur- | Cucumbers).| - | _Crinoidea_|=Order:= |=Order:= | chins). | | - | (Feather | _Ophiuroidea_| _Asteroidea_ | | | - | Star). | (Brittle | (Common | | | - | | Stars). | Stars). | | | - +------------+--------------+---------------+-------------+-------------+ - - - - - CHAPTER XI - - _MARINE WORMS_ - - -Some groups of animals are so well defined that the individual species -contained in them can be assigned their proper place without any -difficulty, the main characteristics by which the group is distinguished -running with more or less precision throughout the series; but, -unfortunately this is not the case with the 'worms,' which constitute -the sub-kingdom _Vermes_. Here we have a most heterogeneous assemblage -of animals, collectively exhibiting exceedingly wide variations in both -form and structure. - -We have already referred to the sea cucumber as wormlike in form, and -this creature is only one of a large number of wormlike animals that are -not worms; and it is also a fact that a considerable number of the worms -are not wormlike. It appears as if the sub-kingdom Vermes were a kind of -receptacle into which we may throw almost any invertebrate animal that -does not readily fall in line with the general characteristics of the -other important groups; for in it we have such a varied assemblage of -creatures that, speaking of them collectively as worms, it becomes most -difficult, if not absolutely impossible, to say exactly what a worm is; -and it is a question whether the sub-kingdom ought not to be divided -into at least two or three groups of the same standing. - -This being the case we can hardly give a satisfactory summary of the -characteristics of the group, and therefore it must be understood that -in our attempt to do so we unavoidably exclude some forms that belong to -it according to our present system of classification. This being -remembered, we will define worms as soft-bodied and elongated animals, -exhibiting a bilateral symmetry (that is, having appendages and organs -arranged symmetrically on each side of a plane extending from the dorsal -to the ventral surface through the centre of the body), and with the -body usually divided into a succession of segments, each of which -resembles the one preceding and following it. Though many of the worms -are generally looked upon as uninteresting creatures, of such an -unattractive appearance and with such depraved habits that they are -beneath respect, yet a study of the sub-kingdom will prove that not only -does it include a number of wonderful forms with the most marvellous -life histories, but that some of them are very beautiful objects; and -this last remark refers more particularly to many of the marine worms, -which come directly within the scope of our work. - -Before passing on to the special study and classification of the marine -species, however, we must say a few words concerning the worms in -general, reminding the reader that all our statements regarding the -anatomy of the creatures may be readily verified by simple dissections -of one or two typical species, such as the common earthworm, the -fisherman's lugworm, the sea mouse, or the common horse-leech of our -fresh-water ponds. With this object in view, the animal may be killed by -immersion in spirit, then pinned out in the dissecting tray under water, -and the body-wall opened by means of a pair of sharp-pointed scissors. - -The digestive tube of a worm runs completely through the length of the -body, and though there is no distinct head, there is always a mouth, and -this is often provided with horny jaws, and sometimes also with horny -teeth, with which the animal is enabled to inflict wounds on its prey. - -Like the preceding sub-kingdom--the _Echinodermata_--worms possess a -system of water tubes; this system, however, is not in any way connected -with the function of locomotion, but is, in many cases at least, if not -in all, intimately associated with the process of respiration. It -consists of a series of tubes, arranged in pairs in the successive -segments, communicating with the body-cavity internally, and opening at -the exterior by means of pores in the cuticle. In some there is a highly -organised system of bloodvessels, containing blood that is usually -either colourless, red, or green, but the colour of the blood is never -due to the presence of corpuscles, as is the case with higher animals, -the tint being due to the plasma or fluid portion of the blood; and -though worms cannot be said to possess a true heart, yet they often have -one or more contractile bloodvessels which serve the purpose of -propelling the blood. - -Most worms possess a nervous system, and, where this is present, it -consists of a chain of ganglia, placed along the ventral side of the -body, beneath the digestive tube, all united by means of a nerve cord, -and distributing nerves in pairs to various parts of the body; and it -may be well to note here one very important point of distinction between -the general arrangement of the central portion of the nervous system in -the worms and higher invertebrates, as compared with that of the -corresponding structure in the vertebrates:--In the former the main axis -of the system, consisting, as we have seen, of a chain of ganglia -connected by a nerve cord, is invariably placed along the _ventral_ -portion of the body-cavity--the surface on which the animal crawls; -while in the vertebrates the axis of the nervous system lies along the -upper or dorsal part of the body; and, instead of lying in the general -body-cavity, in company with the organs of digestion and circulation, is -enclosed in the bony canal formed by the vertebral column. It will be -seen from this that when it is desired to examine the nervous system of -the invertebrate animal, the body-wall should be opened along the middle -of the ventral surface, while, in the vertebrate, the central axis -should be exposed from above. - -Many of the vermes are parasitic, either attaching themselves to the -exterior of other animals, and deriving nourishment by sucking their -blood, or they are internal parasites, living in the digestive canal of -their hosts and partaking of the digested food with which they are -almost perpetually surrounded, or burrowing into the tissues and -imbibing the nutritive fluids which they contain; and it is interesting -to study even these degraded members of the group, if only to observe -how their physical organisation degenerates in accordance with their -depraved mode of living. In them we find no digestive system with the -exception of the simplest sac from which the fluids they swallow may be -absorbed, for their food is taken in a condition ready for direct -assimilation; and the food so obtained being readily absorbed into all -parts of their soft bodies, and being sufficiently charged with oxygen -gas by the respiration of their hosts, they require no special organs -for circulation or respiration, nor, indeed, do we find any. Further, we -find that the nervous system is often undeveloped; for since the -parasites, and especially the internal ones, are so plentifully -surrounded with all the necessaries of existence, their bodies are so -simple in construction that no complex nervous system is required to -promote or control either locomotion or internal functions. Even the -general body-cavity often disappears in these degraded creatures, the -internal organisation being of such a low type that there is no -necessity for it; and all the abundant nourishment absorbed over and -above that required for the sustenance of their simple bodies is -utilised in the reproduction of the species; consequently we find, as a -rule, the reproductive organs well represented, and the species -concerned very prolific. - -It is an interesting fact, too, that these parasites, in their earliest -stage, possess organs which are present in the higher worms, but which -degenerate as they approach the adult form, thus indicating that they -have descended from more respectable members of the animal world, and -that the low physical development which they ultimately attain is the -natural result of their base mode of living. - -The young marine naturalist, working on our coasts, will not be brought -into intimate contact with parasitic worms to any large extent, yet we -have said this little on parasitism to show that these degenerate -creatures are not really devoid of interest, and that they will repay -study whenever they are found. They will be more frequently met with -during the examination of the animals--usually higher types--that become -their hosts, and thus they hardly come within the scope of this work. - - [Illustration: FIG. 116.--A TURBELLARIAN, MAGNIFIED - _a_, mouth; _b_, cavity of mouth; _c_, gullet; _d_, stomach; _e_, - branches of stomach; _f_, nerve ganglion; _g_ to _m_, reproductive - organs.] - -The simplest of the worms are those forming the class _Turbellaria_, so -designated on account of the commotion they produce in the water -surrounding them by means of the vibratile cilia that fringe their -bodies--a characteristic that is also expressed by their popular name of -Whirl Worms. They are usually small creatures, with soft, flattened, -unsegmented bodies, though some of the larger species are really -wormlike in form, and are more or less distinctly divided into a chain -of segments. Many of them are marine, and may be seen gliding over -stones left uncovered by the receding tide with a smooth slug-like -motion, and when disturbed in a rock pool, occasionally swimming with a -similar smooth motion by the aid of their cilia. They avoid bright -light, and are consequently generally found on the under surfaces of -stones, especially in rather muddy situations, and where the stones are -covered with a slimy deposit of low forms of life. In these -turbellarians the mouth is situated on the under surface, thus enabling -the animal to obtain its nourishment from the slimy surface over which -it moves, and it is also provided with an extensile proboscis that aids -it in the collection of its food. The digestive tube is generally very -complex in form, extending its branches into every part of the soft -body; and, there being no special organs of respiration, the animal -derives all the oxygen required by direct absorption from the water -through the soft integument. - -When searching for turbellarians on the sea shore one must be prepared -to meet with interesting examples of protective colouring that will -render a close examination of rocks and stones absolutely necessary. -Some of these worms are of a dull greyish or brownish colour, so closely -resembling that of the surface over which they glide that they are not -easily distinguished; and the thin bodies of others are so transparent -that the colour of the stone beneath is visible through them, thus -preventing them from being clearly observed. - -Overturned stones should be examined for their flattened bodies gliding -along rapidly in close contact with the surface. They may be removed -without injury by placing a wet frond of a sea weed close to the stone, -in front of one end of the body, and then urging them to glide on to it -by gently touching the opposite end. Sometimes, however, the -turbellarians remain perfectly still when exposed to the light, in which -case they are even more difficult to detect, but a little practice will -soon enable one to distinguish them with readiness. - -Allied to the turbellarians are the Spoon Worms or Squirt Worms, some -species of which inhabit deep water round our shores, where they burrow -into the sand or mud of the bed of the sea. These form the class -_Gephyrea_, and consist of creatures with sac-like or cylindrical and -elongated bodies, and a protrusible proboscis, which is often of great -length. Their bodies are not distinctly segmented, nor do they bear any -appendages. The skin is tough and horny, and the body-wall, which is -very thick and muscular, is often contracted when the animal is -disturbed, thus causing a jet of water to be forcibly ejected. - -All the most interesting of the marine worms belong to the _Annelida_ or -_Chaetopoda_, popularly known as the Bristle-footed worms, because their -locomotion is aided more or less by the presence of stiff bristles that -project beyond the surface of the skin. These are all highly organised -worms, mostly with very elongated bodies that are distinctly segmented -exteriorly by a number of transverse grooves, while the interior is -correspondingly divided into a number of compartments by means of a -series of _septa_. - -In addition to the bristles already mentioned, there are often numerous -appendages, but these must be distinguished from the more perfect -appendages of the arthropods, to be hereafter described; for while the -latter are distinctly jointed to the body, and are themselves made up of -parts that are jointed together, the former are mere outgrowths of the -body-wall. The digestive and circulatory systems are well developed, as -is also the system of water tubes that connect the body-cavity with the -exterior, while the body-cavity itself is full of fluid. - -This group of worms is subdivided into two divisions, the many bristled -(_Polychaeta_) and the sparsely bristled (_Oligochaeta_) worms. The latter -contain the common earthworms and some less known species, while the -former include a number of interesting and even beautiful worms, all of -which are marine, and many of them among the commonest objects of the -sea shore. - -These Polychaetes exhibit a great variety of habit as well as of -appearance. Some live in crevices of the rocks or under stones and -weeds, or make burrows in the sand or mud of the bed of the sea, and -roam about freely at times in search of food. They are continually -coming within the ken of the sea-side collector, being revealed by -almost every overturned stone near the low-water mark, and are often -seen crawling over the wet rocks just left uncovered by the receding -tide; while their burrows are often so numerous that hundreds may be -counted in every few square feet. But many are sedentary species, and -these are not so generally known to young sea-side naturalists, who -frequently observe, and even preserve, the interesting homes they -construct, while less attention is given to the architects that build -them. - -It is very interesting to observe some of the general differences -between the roving and the sedentary species--differences which -illustrate the principle of adaptation of structure to habit. The roving -species are provided with a lobe that overhangs the mouth, bearing -feelers and eyes, and are thus enabled to seek out any desired path and -to search for their food. They are provided with bristles and other -appendages by means of which they can travel freely over the surfaces of -solid objects, and are able to swim well either by undulations of the -body, or by fringed appendages, or both. The carnivorous species, too, -are provided with strong, horny jaws, and sharp, curved teeth, by means -of which they can capture and hold their prey. The sedentary species, on -the other hand, unable to move about in search of food, are supplied -with a number of appendages by means of which they can set up water -currents towards their mouths, and which also serve the purpose of -special breathing organs, and, having no means of pursuing and devouring -animals of any size, they do not possess the horny jaws and curved teeth -so common in the rovers. Their eyes, too, are less perfectly developed, -and the tactile proboscis of their free-moving relatives is absent. - - [Illustration: FIG. 117.--_Arenicola piscatorum_] - -Of the roving worms, perhaps, the Lugworm or Sandworm (_Arenicola -piscatorum_) is the best known. Its burrows may be seen on almost every -low sandy or muddy shore, and, being so highly valued as a bait, its -general appearance is well known to all professional and amateur sea -fishers. It reaches a length of eight inches or more, and varies in -colour according to the sand or mud in which it lives. The segments of -this worm are very different in structure in different parts of the -body. Those in the front of the body have a few tufts of bristles -arranged in pairs, while the middle portion of the body has large -brush-like tufts of filamentous gills placed rather close together; and -the hindmost part has no bristles or appendages of any kind, and is so -well filled with the sand or mud that it is quite hard and firm to the -touch. As is the case with our common earthworms, the sand or mud is -swallowed in enormous quantities, and this is not only the means by -which the lugworm derives its food, but also assists it considerably in -making its burrows; the extent to which this creature carries on its -work of excavation may be estimated by the thousands of little -contorted, worm-like heaps of sand that lie on the surface at every -period of low water. These little heaps are known as 'castings,' and -consist of the sand that passed through the worm's body as the burrowing -proceeded. - -The Ragworm is another species that is highly valued as bait. It burrows -into the odorous mud that is so commonly deposited in harbours and the -mouths of sluggish rivers. In this species the segments are similar -throughout the length of the body, and the numerous flattened appendages -give it the ragged appearance that has suggested its popular name. Quite -a number of marine worms closely allied to the common ragworm, and -resembling it in general form, are to be found on our shores. Many of -these may be seen by turning over stones that are left exposed at low -tide, while others hide themselves in snug little crevices of the rock, -or in the empty shells of the acorn barnacle and various molluscs; and -some species, including one of a bright-green colour, creep freely over -the wet rocks in search of food or home, often exposing themselves to -the rays of a fierce summer sun. - - [Illustration: FIG. 118.--THE SEA MOUSE] - -The Sea Mouse (_Aphrodita aculeata_) is certainly one of the most -interesting of the roving marine worms, and, though seldom seen above -low-water line, may often be obtained by the sea-side collector with the -aid of friendly fishermen, who sometimes find it plentifully among the -contents of their trawl nets. Failing such aid, it may be looked for -among the encrusted stones that are exposed only at the lowest spring -tides, especially in places where a certain amount of mud has been -deposited under the shelter of outlying rocks; and the chances of -success are much greater if the search is made immediately after a -storm, for at such times much of the life that exists in deep water will -have been driven shoreward by the force of the waves. - -At first sight the sea mouse would hardly be associated with the worms; -for, instead of having the elongated and cylindrical form that is -usually regarded as characteristic of these creatures, it is broad and -slug-like in shape, the under surface, on which it crawls, being flat, -while the upper side is convex. The segmentation of the body, too, is -not readily seen in the upper surface on account of the thick felt-like -covering of hairs, but is at once apparent when the creature has been -turned over to expose the ventral side. - -When seen for the first time in its natural haunt one naturally wonders -what the moving mass may be. Crawling sluggishly over incrusted stones, -or remaining perfectly still in a muddy puddle that has been exposed by -overturning a stone, it looks like a little mound of mud itself, about -four or five inches long, and its general colour and surface so closely -resembles that of its surroundings that an inexperienced collector may -never even suspect that the mass is a living animal form. But take the -creature and wash it in the nearest rock pool, and it will be recognised -as a broad segmental worm, thickly covered with fine hairs above, and -its sides adorned by bristles that display a most beautiful iridescence. -It is not easy to see the value of this gorgeous colouring to the -animal, and it is doubtful whether, on account of the muddy nature of -the creature's home, such colouring is often displayed to the view of -other inhabitants of the sea; but it is well known, on the other hand, -that sea mice are readily devoured by fishes, even though they possess -an armature of stiff and sharp spines, and that they must therefore be -often preserved from destruction by the close resemblance of the general -colour to that of their surroundings. - -The gills of the sea mouse are not prominent appendages, as with most -marine worms, but are soft fleshy structures situated beneath the -overlapping scales that lie hidden below the thick hair of the upper -surface. - -As it is most probable that the reader may desire to preserve a sea -mouse at some time or other, a few words concerning the best methods of -doing this may be of value. If it is to be preserved in fluid, it should -be thoroughly washed to remove all the mud that normally covers its -body, and then placed in spirit or formaldehyde, both of which fluids -have no destructive effects on the iridescent colouring of the bristles. -If, however, it is desired to keep the specimen in a dry state, it -should first be put into strong spirit containing a few grains of -corrosive sublimate, for a few days. It should then be put under -considerable pressure between several thicknesses of absorbent paper to -expel the fluid it contains, as well as all the softer internal -structures. By this means it will have been squeezed quite flat, so that -it presents anything but a natural appearance; but the skin may be blown -out to the normal shape by means of a glass tube inserted into the -mouth, and then set aside to dry. As the water it originally contained -has been extracted by the strong spirit, the drying takes place very -quickly; and the small amount of corrosive sublimate that has penetrated -into its substance will be sufficient to protect it from the invasion of -those pests that commonly attack our museum specimens. - -Passing now to the sedentary or fixed worms, we meet with some that are -very interesting and beautiful creatures, even when considered apart -from the wonderful homes they construct. The several species of the -genus _Terebella_ form a soft and flexible tube by binding together -particles of sand, shells, or mud with a sticky substance that exudes -from their own bodies. These tubes are to be found in abundance between -the tide-marks on almost every low, sandy shore, the nature of the tubes -varying, of course, with the character of the materials at the disposal -of the builder. - -In some cases the tubes are exposed throughout the greater part of their -length, but very frequently they are more or less buried in the sand or -other material of the beach, so that one has to dig to a moderate depth -in order to extricate them. In either case, however, the tube of -Terebella may be known by the free tufts of sandy threads that form a -deep fringe around its mouth. - -These worms almost invariably select a sheltered situation for their -abode, and should be searched for at the foot of rocks, or under stones, -and it is no easy matter to move the buried tube with its occupant -intact. - -When turning over the stones of a sandy or muddy beach one frequently -discovers the slender, thread-like tentacles of the Terebella, together -with the sandy filaments that surround the mouth of the tube, the -remainder of the tube and its occupant being beneath the surface, and -the ground is often so hard and stony that a strong tool is necessary -to dig it out; but the work entailed will be amply repaid if a perfect -specimen be obtained and placed for observation in the aquarium. - - [Illustration: FIG. 119.--TUBE-BUILDING WORMS: _Terebella_ (LEFT), - _Serpula_ (MIDDLE), _Sabella_ (RIGHT)] - -The reader may possibly be acquainted with the tubes or cases that are -constructed by the larvae of caddis flies in fresh-water ponds and -streams, and perhaps has noticed the ease with which these creatures may -be made to construct new homes after having been turned out of doors. -Similar experiments may be performed with Terebella; for when the worm -has been extricated from its tube without injury--a work that requires -great care on account of the soft and slender nature of the creature's -body--and placed in the aquarium with a bed of suitable material, it -will build itself a new dwelling. As with the caddis larvae, the -different species may be known by the materials they select to construct -their tubes, but in captivity they may be compelled to employ other than -their favourite substance for this purpose. It is unfortunate, however, -that Terebella is a nocturnal builder, and thus its movements are not so -easily observed. - -When removed from its tube its first movements suggest a resentment at -the untimely ejection. This being over, it seeks a sheltered situation -beneath the edge of a stone, and, at nightfall, commences the slow -process of the construction of a fresh home. The particles of material -at hand are seized by the tentacles, placed in position round the body, -where they are held together by the sticky secretion already mentioned. - - [Illustration: FIG. 120.--_Terebella_ REMOVED FROM ITS TUBE] - -The tentacles are employed in two distinct ways:--They may be flattened -into slender ribbon-like structures, which, by being folded -longitudinally at any point, may be made to grasp a particle of sand; -and, in addition to this, the tip of the tentacle may be converted into -a minute cup-shaped sucker by the withdrawal of the fluid it contains -into the body. - -Some species of Terebella build their tubes of ordinary sand, while -others select fragments of shells. Some employ mud only, and -occasionally we meet with tubes constructed of the silky secretion of -the body with hardly any foreign matter. - -We sometimes see edges of rocks, on low, sandy shores, covered with what -appears to be large masses of consolidated sand, full of holes a little -more than an eighth of an inch in diameter; and these masses are often -so extensive and so firm that they seem to form the greater part of the -rock itself. Such masses are particularly abundant on the south coasts -of Devon and Cornwall, but are more or less plentiful on most sandy -shores of Great Britain. They consist of the tubes of a species of the -marine worm _Sabella_, which have been built up much in the same manner -as those of Terebella, but usually exist in such numbers in the same -spot that, together with the sand that has been washed between them, -they form the dense masses just described. - -A cluster of some dozens of these tubes may be detached with the aid of -a hammer and chisel; or, in some instances, where the mass of tubes is -not held so firmly together, by the mere pressure of the hand; and it -will then be observed that each tube consists of a flexible membrane, of -a somewhat leathery nature, formed by a sticky secretion from the body -of the worm, with its outer surface covered with grains of sand. The -tubes may be easily opened, and the occupants extracted for examination, -when it will be observed that the front or upper portion of the worm is -short and thick, while the hindmost portion is much thinner, and is -doubled forwards in the tube. The body is also provided with numerous -bristles, by means of which the worm is enabled to grasp the membranous -lining of the tube, and thus secure a firm hold within its home. - -A cluster of these tubes should be placed in a rock pool, or in the -marine aquarium, when the worms may be seen to protrude gradually, and -expose a large number of feathered tentacles, which, by their incessant -motion, keep up the constant circulation of the water for the purpose of -respiration as well as to bring food particles towards the mouths of the -worms. - -It is possible to keep these worms alive for some time in the aquarium, -but special care is required for the reason that it is a very difficult -matter to secure a cluster of tubes without injury to a certain number -which are sure to be broken or otherwise damaged; and these, dying and -decomposing within their homes, speedily pollute the water. Hence it is -necessary to keep a sharp watch for dead specimens, which should, of -course, be removed at once. The presence of a putrefying worm may often -be detected by the appearance of a whitish fungoid growth round the -mouth of what appears to be an empty tube; and if, through neglect, the -water of the aquarium has been allowed to become contaminated by the -products of decomposition, it will often happen that some of the living -worms will come entirely out from their tubes, as if to seek a more -sanitary situation. Thus, the exit of worms from their homes may always -be looked upon as pointing to a suspicious condition of the water which, -if not corrected immediately, may lead to the death of all. - -The species we have briefly described is by far the commonest of the -genus Sabella, but there are several others to be found on our shores. -Some are of a solitary nature, and construct a sandy tube so much like -that of a certain species of Terebella that they may be mistaken for -that genus. Another solitary species builds a hard stony tube of -carbonate of lime that has been extracted from the sea water; and -although it is hardly possible to take the live worm from this -calcareous tube without injury, the animal may be obtained intact for -examination or preservation by dissolving away the tube in dilute -hydrochloric acid. - - [Illustration: FIG. 121.--A TUBE OF _Serpula_ ATTACHED TO A SHELL] - -While engaged in collecting specimens on the sea shore we are -continually meeting with stones and shells that are more or less covered -with white, limy tubes twisted into all manner of serpentine forms. -These are the tubes of other marine worms known as the _Serpulae_, which, -like the species previously mentioned, are interesting objects for the -aquarium. - -The tubes themselves are worthy of study and preservation, more -especially as they vary in form, and may, to some extent, provide a -means by which the different species may be identified. They are -composed of fine layers of calcareous matter secreted by the body of the -worm within, and lined by a thin leathery membrane which may be easily -exposed by dissolving away the mineral matter as just described. Some -are triangular in section, and often distinctly keeled, while others are -cylindrical, and flattened more or less on the lower side. The -triangular tubes are attached to stones or shells throughout their -length, but the cylindrical ones are often elevated above the surface in -the wider and newer part. - -If a cluster of these tubes, freshly gathered from between the -tide-marks, be placed in the aquarium, the worms will soon protrude the -foremost portion of their bodies, exposing beautiful fan-like gills, -often brilliantly coloured in shades of scarlet, blue, or purple, which -are kept in motion in such a manner as to convey water, and consequently -also food, towards the mouth. The gills are of course, richly supplied -with blood, for their main function is to aerate that liquid by exposing -it to the water in order to absorb oxygen gas. The body of the worm is -provided also with little cilia, which, by their constant vibratory -motion, keep up a circulation of water through the tube; and this not -only keeps the tubular home free from excrement and other sedimentary -matter, but also probably assists in the function of respiration by -bringing fresh supplies of water in contact with the animal's soft and -absorbent skin. - - [Illustration: FIG. 122.--_Serpula_ REMOVED FROM ITS TUBE] - -When the worms are disturbed they immediately withdraw themselves within -the tubes, this being done by the aid of the numerous minute hooklets on -the surface of the body that enable the worms to cling firmly to the -membranous linings of their homes; and it will then be observed that the -mouth of each tube is closed by a lid (_operculum_), which hangs as by a -hinge when not in use. These operculi vary much in character, and supply -another aid in the identification of the various species. They differ -much in shape, and may be either membranous, horny, or calcareous. - -Little calcareous tubes, somewhat similar to those of the _Serpulae_, but -always in the form of a spiral, may often be seen on stones and shells, -and the fronds of sea weeds, sometimes so closely packed together as to -almost entirely cover the surface. The average diameter of these spirals -is only about a sixteenth of an inch, and many are so small that a lens -is necessary to discern their shape. In general form they closely -resemble some of the small species of _Planorbis_ shells that are so -common in our ponds and streams, but these latter are the shells of -freely moving _molluscs_, and are generally of a brownish colour. - - [Illustration: FIG. 123.--THE SEA MAT (_Flustra_)] - -The minute worms that live within the tubes in question belong to the -genus _Spirorbis_, and are very similar to those of the _Serpulae_, and -their pretty plumed gills may be seen with a lens when a cluster of the -tubes is placed in a shallow vessel of sea water. A sharp tap on the -table on which the vessel rests will cause the little creatures to -suddenly retire into their homes, the entrances to which may then be -seen to be closed by an operculum. - -There is an interesting group of animals known collectively as the -_Bryozoa_ or _Polyzoa_, or, popularly, as the Moss Polyps, that are -often classed with the worms, though they are not, according to the -general idea, wormlike in appearance. They live in pretty colonies, many -of which are certainly familiar objects to all who ramble along the sea -shore. Some form pretty lacelike patches on the fronds of sea weeds, -while others are built up into flat, frond-like, branching objects that -are often mistaken for sea weeds by young collectors. Among the latter -is the Sea Mat (_Flustra_), that is so commonly washed up on the shore -in great abundance. An examination with a lens will show that, in both -instances, the mass consists of very many minute cells, with horny or -calcareous walls, the mouth of each cell being close by an operculum. - -On placing the colony in sea water, however, we find that each little -cell is the home of a small animal, that protrudes from the cell, -exposing a mouth that is surrounded by a crown of tentacles. A -moderately high magnifying power will also show that the tentacles are -covered with minute vibratile cilia, by means of which currents of water -are set in motion towards the mouth to supply the animal with food. -Some, too, have a lip by means of which the mouth may be closed. - - [Illustration: FIG. 124.--_Flustra_ IN ITS CELL, MAGNIFIED] - -In addition to the colonies just briefly described, there are other moss -polyps that build up little, branching, tree-like clusters which closely -resemble some of the sea firs, and many of these are to be found in the -sheltered crevices of rocks, or attached to the under sides of stones -between the tide-marks. - -While searching the surfaces of rocks and weeds at low tide, one's -fingers will be constantly coming in contact with fixed, soft-bodied -animals that suddenly eject a fine stream of water as they are touched. -These are the Sea Squirts, sometimes spoken of as the Tunicate Worms. -They are semi-transparent creatures of oval or elongated form, and -usually of a pale yellow, brown, or pink colour; and derive their -popular name from the fact that they are covered externally by a -continuous tunic or wall of tough structure. - -Although the tunicates resemble worms in many points of structure, it is -interesting to note that in their young or larval state the body -consists of two cavities, one of which contains the internal organs, -while in the other the central portion of the nervous system is -developed, in which respects they resemble the vertebrate or back-boned -animals--fishes, amphibians, reptiles, birds, and mammals. At this -stage, too, the creatures possess a tail that is supported by a rod of -gristle similar to that which gives place to the backbone in the -developing vertebrate. These features, though only transitory, are -regarded as a mark of relationship to the higher forms of animal life, -and thus the tunicates have been separated from the sub-kingdom Vermes -by some zoologists, and given an exalted place at the top of the -invertebrate scale, where they form a sub-kingdom of their own, and are -looked upon as a link connecting the invertebrates with the vertebrates. - - [Illustration: FIG. 125.--SEA SQUIRT] - -Before passing on to the next sub-kingdom, we should observe that the -interesting Rotifers or Wheel Animals also belong to the Vermes; but -although many of these minute creatures are to be found in sea water, -their principal home is the stagnant water of fresh-water ponds and -ditches, and thus we may be excused for neglecting them here. - - - - - CHAPTER XII - - _MARINE MOLLUSCS_ - - -The sub-kingdom _Mollusca_ includes a great variety of soft-bodied -animals which differ from the members of the last division in the fact -that they are never segmented, and in the possession of a thick outer -covering, of a leathery nature, which completely envelops the body, and -which usually secretes a calcareous shell of one or more parts. A -general idea of the extent of the group may be formed when we state that -it contains the Octopus and the Cuttlefish; all Snails and Slugs, and -animals of a similar nature; and all those numerous 'bivalves' which are -represented by the well-known Oysters, Mussels, Scallops, &c. - -By far the greater number of the molluscs are aquatic in habit; and of -these such a large proportion are marine that the group provides plenty -of occupation for the sea-side naturalist. This being the case, we shall -devote the present chapter to a description of the general -characteristics of these animals, and to the principles of their -classification, illustrating our remarks by a few selections from all -the chief divisions. - -Although, as we have already hinted, the body of a mollusc generally -bears but little resemblance to that of the typical elongated and -segmented worm, yet the study of the earliest stages of the former shows -that a certain relationship exists between the two sub-kingdoms, the -newly hatched mollusc being often a minute free-swimming creature with -expanded lobes fringed with cilia, and bearing a resemblance to certain -of the Rotifers, Moss Polyps, and other animals that are included among -the _Vermes_. But in the adult molluscs this resemblance is lost, these -creatures being generally easily distinguished from all others by -certain well-marked external features, as well as by internal characters -that are peculiar to them and fairly constant throughout the group. - -The external shell, where it exists, is usually composed of one or of -two parts, and therefore we speak of univalve and bivalve molluscs; and -no internal skeleton of any kind is to be found except in the division -containing the Cuttlefishes, the 'bone' of which is one of the common -objects washed up on our shores by the breakers. - -In all the molluscs there is a well-formed digestive tube, and often a -complex arrangement of small teeth which sever the food by a rasp-like -action. There is also a well-formed heart, consisting of two or more -cavities, by means of which the blood is forced through the body; but, -as a rule, blood vessels are either few or absent, the blood being -driven through spaces between the tissues that serve the same purpose. - - [Illustration: FIG. 126.--LARVAE OF MOLLUSCS - _v_, ciliated 'velum'; _f_, rudimental foot] - -The nervous system consists of a few masses of nerve substance -(_ganglia_), connected by nerve cords, and sending off fibres to various -parts of the body, the principal ganglion being one situated close to -the mouth, and often surrounding the first portion of the digestive -tube. - -The animals of this sub-kingdom are grouped into three principal and -well-marked divisions--the _Lamellibranchs_, or Plate-gilled molluscs, -the gills of which are composed of plate-like layers, and the headless -bodies enclosed in a bivalve shell; the _Cephalophora_, or head-bearing -molluscs, protected by a univalve shell; and the _Cephalopoda_, or -Head-footed molluscs, so called because the mouth is surrounded by -tentacles or arms by which the animal can cling to objects or seize its -prey. - -We shall deal with these three divisions in the above order, taking -first the bivalves, the shells of which are found in great variety along -our shores. - -The general nature of a lamellibranch is easily made out by the -examination of one of the common species that may be obtained alive on -any part of the coast, such as the Edible Mussel, the Cockle, or the -Oyster, and the reader will do well to secure a few specimens and -examine them with the aid of the following description of the principal -distinguishing features. - -The shell is formed of two valves, united by a hinge which is sometimes -of the simplest possible description, but which often exhibits a -beautiful arrangement of interlocking teeth. A _ligament_ of flexible -and elastic substance often holds the two valves together. - - [Illustration: FIG. 127.--SHELL OF THE PRICKLY COCKLE (_Cardium - aculeatum_) SHOWING UMBO AND HINGE; ALSO THE INTERIOR SHOWING THE - TEETH] - -The reader has probably observed that the valves of a dead lamellibranch -usually gape. This is due either to the pull exerted by a ligament that -is attached to the valves outside the hinge, or to the pressure of an -internal cartilage which unites the valves within, and which is -compressed when the shell is closed. When the animal is alive, it has -the power of closing its shell by the contraction of the adductor -muscles, to be presently described, and when the valves are brought -together by this means the external ligament is more or less stretched, -or the cartilage within, which is also an elastic material, is -compressed. - -Examining the shell from the exterior we observe that each valve has a -nucleus (the _umbo_) close to the hinge, round which are usually a -number of more or less distinct concentric lines, extending to the lower -or ventral margin. This nucleus represents the whole shell of the young -mollusc, and the lines are the lines of growth, each one marking the -extreme limit of the valve at a particular period of the animal's -existence. Further it will be observed that the lines of growth are -often wider apart in some directions than in others, thus denoting the -unequal rate of growth that determined the form of the adult shell. - - [Illustration: FIG. 128.--INTERIOR OF BIVALVE SHELL, SHOWING MUSCULAR - SCARS AND PALLIAL LINE] - -The shell of a bivalve is often made up of two very distinct layers, the -outer one called the prismatic layer because, when examined -microscopically, it is seen to consist of minute vertical prisms of -calcareous matter; and the inner one presenting a beautiful pearly -iridescence, due to the fact that it is made up of a number of extremely -thin and finely waved layers of calcareous substance that have the power -of decomposing light. This latter layer is secreted by the whole surface -of the mantle that lies in contact with it, while the outer, prismatic -portion of the shell is formed only by the free edge of the mantle; and -we often find a distinct line (the _pallial line_), some little distance -from the ventral margin that marks the junction of the muscle of the -mantle with the shell. The shape of this line is a very important -feature of the shell, since it is of great value in the determination of -relationships. - -Further, the inner surface of each valve is marked by the impressions or -scars of other muscles, the number and position of which vary -considerably in different species. They include the _adductor_ muscle or -muscles (one or two in number) that pull the valve together; the muscle -or muscles that withdraw the foot, called the _retractor pedis_, and the -_protractor pedis_ that pulls the foot out. Not only are these scars -often very distinct in themselves, but we may frequently observe lines -running tangentially from their circumferences towards the umbo, to -which they all converge. These lines enclose the areas previously -occupied by the muscular impressions; in other words, they show the -directions in which the muscles named above shifted their positions as -the animal grew. - - [Illustration: FIG. 129.--DIAGRAM OF THE ANATOMY OF A LAMELLIBRANCH - _f_, mouth, with labial palps; _g_, stomach; _i_, intestine, - surrounded by the liver; _a_, anus; _r_, posterior adductor muscle; - _e_, anterior adductor muscle; _c_, heart; _d_, nerve ganglion; - _m_, mantle (the right lobe has been removed); _s_, siphons; _h_, - gills; _ft_, foot] - -Now let us obtain a few species of live lamellibranchs, put them in a -vessel of sea water, and observe them after they have been left -undisturbed for a time. The shell will be seen to gape slightly, -exposing the edges of the two lobes of the mantle which lie closely on -the inner surface of the valves, thus completely enveloping the body of -the animal; and at one end, usually the narrower end in the case of -irregular shells, we shall observe two openings--the _siphons_, -sometimes enclosed within a tube formed by a prolongation of the united -mantle lobes, and protruding from between the valves, and sometimes -formed by the mere contact of the mantle lobes at two adjacent points. -If now we introduce a little carmine or other colouring matter by means -of a glass tube, setting it free near the lower siphon--the one more -remote from the umbo of the shell, we observe that it enters the body of -the mollusc through this opening, and reappears shortly afterwards -through the upper or dorsal siphon. Thus we see that water currents are -incessantly circulating in the body of the animal, entering by the -_inhalent_ or _ventral siphon_, and leaving by the _exhalent_ or _dorsal -siphon_. These currents are maintained by the vibratile action of -thousands of minute cilia belonging to cells that line the cavities of -the body, and serve to supply the animal with both air and food; for -lamellibranchs, being gill-breathers, derive the oxygen necessary for -respiration from the air held in solution by the water, and their food -consists entirely of the minute living creatures that always abound in -natural waters. - -Again, we shall find that some of our live bivalves have protruded a -thick, conical, fleshy mass--the _foot_, from the opposite end of the -body. This organ is the means of locomotion in the case of the burrowing -and other free-moving bivalves, but is developed to a less extent in -those species that lead a sedentary life. Thus, the common Edible Mussel -secretes a tuft of strong silky fibres (_byssus_) by means of which it -fixes itself to a rock or other body, and therefore does not need the -assistance of a muscular foot; and an examination of its body will show -that the foot is very small in proportion to the size of the animal, as -compared with that of the wandering and burrowing species. The same is -true of the oyster, which lies fixed on its side, the lower valve being -attached to the surface on which it rests. - - [Illustration: FIG. 130.--_Mytilus edulis_, WITH BYSSUS] - -We have made use of the terms _dorsal_ and _ventral_ in speaking of the -shell of a bivalve, and it is important that these and a few other -similar terms be well understood by those who are about to read the -descriptions of the animals, or who may desire to describe them -themselves. To do this, take a bivalve in your hand, and hold it before -you in such a position that the hinge is uppermost, and the siphons -turned towards you. The foot of the animal is now pointing in the -direction you are looking, and the mouth, situated at the base of the -foot, is also directed the same way. You have now placed the shell, and, -of course, also the animal, in such a position that its _dorsal_ side is -uppermost, the _ventral_ side below, the _anterior_ end turned from you, -the _posterior_ (often narrower) end towards you, the _right valve_ on -your right, and the _left valve_ on your left. Knowing the exact uses of -these few terms you are in a better position to understand the -descriptions of bivalves, and to locate the exact situations of the -various internal organs named in such descriptions. - -A great deal of the internal anatomy of a bivalve mollusc may be made -out by easy dissections, and although the structure of the different -species varies in several details, the general characteristics of the -group are practically the same in all and may be gathered by the -examination of a few specimens. - - [Illustration: FIG. 131.--A BIVALVE SHELL (_Tapes virgineana_) - _a_, anterior; _p_, posterior; _l_, left valve; _r_, right valve; - _u_, umbo, on dorsal side] - -For this purpose the shell should be prised open by means of some -flattened but blunt implement, such as the handle of a scalpel, and -then, after inserting a piece of cork to keep the valves apart, gently -remove the mantle lobe from the valve which is held uppermost with the -same implement, being careful to separate it from the shell without -doing any damage to the soft structures. Separating the mantle from the -shell in this way we meet with one or more hard masses of muscle that -are joined very firmly to the latter. These are the adductor muscles -that pass directly from valve to valve, and on cutting them through -close to the uppermost valve, the latter can be raised so as to expose -the body of the animal, mostly hidden by the overlying mantle lobe. - -Before raising the upper mantle lobe we observe the heart, on the dorsal -margin of the body, near the hinge of the shell, situated in a -transparent cavity (the _pericardium_) containing a colourless fluid. It -consists of at least two cavities--a thick-walled ventricle and a -thin-walled auricle, and its slow pulsations may be watched with or -without the use of a hand lens. On opening the pericardium the heart is -still better seen, and if we carefully cut into the thick-walled -ventricle we find a tube running completely through its cavity. This is -the _rectum_--the last part of the digestive tube, that commences at the -mouth, and terminates in a cavity at the posterior end communicating -with the exhalent siphon. - -After noting the nature and position of the one or two adductor muscles -previously cut through, we turn the upper mantle lobe upwards, laying -it back over the hinge of the shell, cutting it through at the bases of -the siphons if we find it is united with the opposite lobe at those -points; or, if not united, we observe two points at which the lobes -touch each other in order to form the siphonal openings. - -Several organs are now exposed to view. The lower mantle lobe is seen in -close contact with the valve below it, and if we touch its edge we shall -probably observe that it is retracted slightly by the contraction of its -own muscular fibres. The tip of the foot is also seen projecting towards -the anterior end, its base being hidden between the two sets of -plate-like gills that extend along the length of the body. On touching -the tip of the foot we find it retract by the contraction of the -muscular fibres of which it is composed, aided, perhaps, by the action -of one or more _retractor pedis muscles_ with which it is supplied. On -raising the upper gill-plates we may observe the dark colour of the -digestive gland (liver) at the base of the foot, and also see two or -more _tentacles_ or _labial palpi_ on the anterior side of the same. - -Between the labial palpi is the mouth, which leads into the stomach by a -short, wide tube, and then into a convoluted tube which finally passes -through the heart, and terminates near the exhalent siphon as above -described. The whole length of this tube may be followed by careful -dissection, its direction being determined at short intervals by probing -it with a bristle that has been tipped with a little melted sealing wax. -It will be seen to wind through the base of the foot, surrounded through -the greater part of its course by the digestive gland, from which a -digestive fluid enters it through small ducts. - -The diagram on p. 194 shows the general internal anatomy of a -lamellibranch, parts of which have been removed to reveal the underlying -structures. The animal lies in its left valve, the right valve, the -right mantle lobe, and the right set of gill-plates having been -completely dissected away. The whole course of the digestive tube has -also been exposed, and the positions of the three nerve ganglia, with -their connecting nerve cords, constituting the central portion of the -nervous system, are also indicated. - -It will be interesting, finally, to learn the direction taken by the -water currents which supply the animal with air and food in their course -through the system. Passing in through the inhalent siphon, the water -immediately enters a large cavity between the mantle lobes. This cavity -(the _branchial cavity_) contains gills, as we have already seen, and -also extends to the mouth. The water, urged on by the motion of myriads -of minute ciliated cells in the walls of the cavity, passes in part -through the digestive tube, and in part around, between, and through the -gill plates, which are perforated by numerous holes. After thus -completely bathing the gills, and supplying the oxygen necessary for -respiration, this latter current passes into a second cavity above the -gills, and thence into the exhalent siphon, where it mingles with the -fluid from the digestive tube as well as with other excretory matter. - -Lamellibranchs are, as a rule, exceedingly prolific, a single individual -of some species discharging more than a million ova in one season. The -larvae swim freely in the water, and are provided with eyes that enable -them to search for their food, but the eyes always disappear when the -young settle down to a more sedentary life. It is true that adult -bivalves sometimes possess visual organs, often in the form of -conspicuous coloured spots on the edge of the mantle, these, however, -are not the same that existed during the larval stage, but are of a more -recent development. - -Lamellibranchs are classified in various ways by different authorities, -the arrangement being based principally on the number and position of -the adductor muscles, or on the nature of the gills. For our present -purpose we shall look upon them as consisting of two main divisions--the -_Asiphonida_ and the _Siphonida_, the former including those species -which do not possess true tubular siphons, the inhalent and exhalent -openings being formed merely by the touching of the mantle lobes; and -the latter those in which the mantle lobes are more or less united and -tubular siphons formed. Each of these divisions contains a number of -families, most of which have representatives that inhabit the sea; and -we shall now note the principal characteristics by which the more -important families are distinguished, and take a few examples of each, -starting with the _Siphonida_. - -Examining the rocks that are left exposed at low tide we frequently find -them drilled with holes that run vertically from the surface, seldom -communicating with each other within, and varying in diameter from less -than a quarter of an inch to half an inch or more. Some of these holes -are the empty burrows of a boring mollusc, while others still contain -the living animal _in situ_. - -The molluscs in question belong to the family _Pholadidae_, which -contains a number of species that exhibit very remarkable features both -as regards structure and habit. The shell is very thin and fragile, but -yet composed of hard material, and its surface is relieved by a series -of prominent concentric ridges that bear a number of little rasp-like -teeth. It gapes at both ends, has neither true hinge nor ligament, and -is often strengthened externally by two or more extra or accessory -valves. The _hinge-plate_ is a very peculiar structure, for it is -reflected over the exterior of the umbones, above which they are -supported by about ten thin shelly plates, the whole thus forming a -series of chambers. The accessory valves are supported by these bridged -structures, and a long, straight, calcareous plate also fills the space -along the dorsal side of the shell in some species. The muscular scars -and the pallial line are distinctly seen on the inner surface, and a -peculiar curved shelly plate projects from under the umbo of each valve. - - [Illustration: FIG. 132.--_Pholas dactylus_ - 1, ventral aspect, with animal; 2, dorsal side of shell showing - accessory valves] - -The animal inhabiting the shell is somewhat wormlike in general form, -and the mantle lobes are united in front--that is at the lower end of -the shell as it lies in the burrow--except that an opening is left for -the protrusion of the short foot. The siphons are united and much -elongated, so that they protrude beyond the mouth of the burrow when the -animal is active; the gills are narrow, and extend into the exhalent -siphon; and the anterior adductor muscle, being very near the umbones, -serves the double purpose of adductor and ligament. - -Such are the general distinguishing features of this family, all the -species of which burrow into stone or other material. Those more -commonly met with on our coasts belong principally to the genus -_Pholas_, and are popularly known as Piddocks. - -It was long a puzzle as to how the fragile piddocks could excavate the -tubular burrows in which they live, and, since their shells are so thin -that it seemed almost impossible for hard stones to be ground away by -them, it was suggested that the rocks were excavated by the action of an -acid secretion. This, however, would not account for the formation of -holes in sandstone and other materials which are insoluble in acids; -and, as a matter of fact, no such acid secretion has ever been -discovered. The boring is undoubtedly done by the mechanical action of -the rasp-like shell, which is rotated backwards and forwards, somewhat -after the manner of a brad-awl, though very slowly, by the muscular -action of the foot of the animal. - -Piddocks are found principally in chalk and limestones, though, as -before hinted, they are to be seen in sandstones and other rocks, the -material in any case being, of course, softer than the shell that bores -it. The largest holes and the largest specimens are to be found in chalk -and other soft rocks; while the piddocks that burrow into harder -material are unable to excavate to the same extent and are, as a -consequence, more stunted in their growth. The burrowing is continued as -long as the animal grows, the hole being always kept at such a depth -that the shell is completely enclosed; and not only this, for when the -rock is soft, and the surface is worn down by the sea, the piddock has -to keep pace with this action, as well as to allow for its increase in -size. - -As a result of the rasping action of the pholas shell on the surrounding -rock the space hollowed out becomes more or less clogged with debris. -This is ejected at intervals by the sudden contraction of the foot of -the animal, which brings the shell quite to the bottom of the burrow, -thus causing the water with its sediment to shoot upwards, - -It is not usually an easy matter to obtain perfect specimens of the -pholas by simply pulling them from their burrows, the shells being so -thin and fragile, and the mouth of the burrow being often narrower than -the widest part of the shell. The best plan is to chip away the rock -with the aid of a mallet and chisel, or to break it into pieces with a -hammer, thus laying open the burrows so that the molluscs fall from -their places. - -The Common Piddock (_Pholas dactylus_) may be identified by the -illustrations, and the other members of the family may be recognised at -once by the similarity in structure and habit. The principal species are -the Little Piddock (_P. parva_), the shell of which is wider in -proportion to the length, with only one accessory valve; and the White -Piddock (_P. candida_), also with a single accessory. In all the above -the foot is remarkable for its ice-like transparency. - - [Illustration: FIG. 133.--_Pholas dactylus_, INTERIOR OF VALVE; AND - _Pholadidea_ WITH ANIMAL] - -There is another genus--the _Pholadidea_--the species of which are very -similar to _pholas_ both in structure and habit. The shells are, -however, more globular in form, and are marked by a transverse furrow. -The gape at the anterior (lower) end is also very wide, and covered over -with a hardened plate in the adult. Also, at the posterior (upper) end -of the shell is a horny cup through which the siphons protrude, and the -latter, which are combined throughout their length, terminate in a disc -that is surrounded by a fringe of little radiating appendages. - -In the same family are the molluscs popularly known as ship worms, which -are so destructive to the woodwork of piers and jetties, or which burrow -into masses of floating timber. Some of these, belonging to the genus -_Xylophaga_--a word that signifies 'wood eaters'--have globular shells -with a wide gape in front, and burrow into floating wood, nearly always -in a direction across the grain. The burrows are about an inch deep, and -are lined with a calcareous deposit. The siphons, combined except at the -ends, are slender and retractile; and the foot, which is thick, is -capable of considerable extension. - - [Illustration: FIG. 134.--THE SHIP WORM] - - [Illustration: FIG. 135.--1. _Teredo navalis._ 2. _Teredo norvegica_] - -Other ship worms belong to the genus _Teredo_, and are very similar in -general characters. The shell is small and globular, with a wide gape at -both ends, and consists of two three-lobed valves with concentric -furrows. It is so small in proportion to the size of the animal that it -encloses but a small portion of the body, and lies at the bottom of the -burrow, which is of considerable length--often from one to two feet. The -animal is very wormlike in form; and although the shell is so small, yet -all the internal organs are enclosed by it. The mantle lobes are united -in front, except where the sucker-like foot passes through them; the -gills are long and narrow, and extend into the siphonal tube; and the -two very long siphons are united almost throughout their length. It is -also interesting to note that in these animals the rectum does not pass -through the heart, as it does in nearly all molluscs, and that a pair of -horny or calcareous 'styles' or 'pallets' project from the place where -the two siphonal tubes begin to diverge. - -Several species of _Teredo_ are to be met with on our coasts, but they -are so similar in general structure that the above brief description -applies almost equally well to all. - -Other boring molluscs frequent the British shores, but they belong to -quite a distinct family called the _Gastrochaenidae_ because their shells -gape widely on the ventral side. Their valves are equal in size and very -thin, the hinge has no teeth and the pallial line is sinuated. The -margins of the mantle lobes are thickened and united except where a -small aperture is left for the protrusion of the finger-like foot. The -siphons are very long and retractile, and the gills extend into the -inhalent tube. These animals burrow into mud, shells, or stone, often -dwelling together in such numbers that their galleries cross one another -and form a most intricate network, and the different species are to be -found from low-water mark to a depth of a hundred fathoms or more. - - [Illustration: FIG. 136.--_Gastrochaena modiolina_ - 1, Animal in shell; 2, shell; 3, cell] - -The British species belong to two genera--the typical genus -_Gastrochaena_, and the _Saxicava_ or stone-borers. - -The former contains the Common Flask shell (_G. modiolina_) which -burrows into limestone and shells, in the latter case passing generally -through the shells into the ground below, and completing its home by -cementing together any fragments of hard material that come in its way -into a flask-shaped cell. The opening of the burrow is shaped like an -hour-glass, the two expansions serving for the protrusion of the -siphonal tubes, and the neck of the flask-shaped abode is usually -lined with a calcareous layer that projects slightly to afford further -protection to the extended siphons. Although this species is very common -on some parts of our coast, it is seldom obtained without the aid of a -dredge, for it usually lives at a depth of from five to ten fathoms; and -when found it is generally no easy matter to extricate them from their -holes, to the sides of which they often cement their shells. - -The genus _Saxicava_ contains a few species that drill holes, often -several inches deep, in shells and stone, and frequently do great damage -to breakwaters and other artificial structures. The foot is usually -provided with a byssus by which the animal fixes itself to a little -projection on the side of its burrow. The species are to be found from -low-water mark to a depth of one hundred fathoms or more. - -The next family, named _Anatinidae_, contains a number of molluscs that -burrow in mud or sand or live in seclusion in the crevices of rocks. -Their shells are thin, with a granulated outer surface, and the valves -are united by a thin external ligament. The inner surface is pearly, the -pallial line usually sinuated, and both valves are pitted for the -reception of the somewhat stout internal cartilage. The mantle lobes are -united, as are also the siphons to a greater or lesser extent; and there -is only one gill on each side. - - [Illustration: FIG. 137.--1. _Thracia phaseolina._ 2. _Thracia - pubescens_, SHOWING PALLIAL LINE] - -Some of the common species of this family are popularly known as Lantern -shells, and perhaps the most familiar of these is _Thracia phaseolina_, -the specific name of which is given on account of a fancied resemblance -of the shell to a bean. The shell is very fragile, and although large -numbers may often be seen stranded on sandy beaches, but few of them are -perfect specimens. - -The family _Myacidae_ may be recognised by the thick, strong, opaque -shells, usually gaping at the posterior end; the wrinkled epidermis -which covers the whole or part of the shell; and the united siphons, -which are more or less retractile. The mantle cavity is also closed with -the exception of a small hole left for the protrusion of the small foot. -The pallial line of the shell is sinuated. - - [Illustration: FIG. 138.--1. _Mya truncata._ 2. INTERIOR OF SHELL. - 3. _Mya arenaria._ 4. _Corbula nucleus_] - -In the above illustration we represent the Common Gaper (_Mya -arenaria_), which burrows to a considerable depth in the sand or mud, -especially in the estuaries of rivers, from between the tide-marks to a -depth of twenty fathoms or more. It may be readily distinguished, in -common with the other species of the same genus, by the characteristic -wrinkled, membranous tube that encloses its fringed siphons, the -membrane being a continuation of the epidermis that extends over the -shell. Another characteristic feature of the genus is the large, flat -process inside the left valve for the attachment of the internal -cartilage. An allied species, _Mya truncata_, is often found abundantly -in company with the above, and may be known by the abruptly squared -posterior end. - -Other species of the _Myacidae_ inhabit our shores, including the little -Basket shell (_Corbula nucleus_), the left valve of which is much -smaller than the right, which overlaps it. The latter, also, is covered -with epidermis, while the former, which is flat, is quite naked. - - [Illustration: FIG. 139.--_Solen siliqua_ - The valves have been separated and the mantle divided to expose the - large foot] - -We now come to the interesting family of Razor shells (_Solenidae_), -specimens of which are washed up on almost every sandy beach, while the -living molluscs may be dug out of their burrows at low-water mark. The -shells are elongated, gaping at both ends with an external ligament; and -the hinge has usually two teeth in one valve and three in the other. The -foot of the animal is cylindrical, large and powerful; and the siphons -are short and united in the long species, but longer and only partially -united in the shorter ones. The gills are long and narrow, and are -prolonged into the inhalent siphon. - -These molluscs lie vertically in their deep burrows at low-water mark, -the opening of the burrow having a form resembling that of a keyhole. -While covered with water they occupy the upper portion of their abode, -but sink to a depth of a foot or more when the tide goes out. As we walk -along the water's edge at extreme low tide we may observe jets of water -that are shot into the air before us. These are produced by the sudden -retreat of the 'Razor-fish' to the bottom of its burrow when alarmed by -the approaching footsteps. Owing to this wariness on the part of the -mollusc, and to the considerable depth of its burrow, specimens cannot -be obtained by digging without much labour; but if a little salt or some -other irritant be dropped into the hole, the animal will soon rise to -eject it, and may then be shut out from the lower part of the burrow by -sharply driving a spade below it. This is undoubtedly the best method of -securing perfect specimens for study or preservation, but fishermen -often obtain large numbers, either for food or for bait, by suddenly -thrusting a long hook down into the gaping shells, and then pulling them -out. This method always does injury to the soft body of the animal, and -often damages the shell, but answers the fisherman's purpose exactly. - -We give illustrations of two shells belonging to the typical genus -(_Solen_), including one on Plate V.; also a British representative of -each of two other genera of the family--_Cerati-solen_ and _Solecurtus_, -the latter of which, as the name implies, contains shorter species. - - [Illustration: FIG. 140.--1. _Solen ensis._ 2. _Cerati-solen legumen._ - 3. _Solecurtus candidus_] - -The next family--the _Tellinidae_--contains a number of well-known -molluscs that burrow into sand or mud, and are enclosed in shells that -are often very prettily marked; and although the family includes several -genera, all may be recognised by the following general features. The -shell is compressed, composed of two equal valves, with little or no -gape, and the ligament situated on the shortest side. The central or -_cardinal_ teeth never exceed two in number in each valve, and the -adductor impressions are round and polished. The mantle is quite open at -the anterior end, and its margins are fringed; the foot is flattened and -tongue-shaped; and the siphons, which are quite separate, are generally -long and slender. - -In the typical genus (_Tellina_), of which we represent two very common -British species, the ligament is very prominent, and the slender siphons -are often much longer than the shell. The members of this group move -very freely, travelling about by means of a broad, flattened foot. - - [Illustration: FIG. 141.--_Tellinidae_ - 1. _Psammobia ferroensis._ 2. _Donax anatinus._ 3. _Tellina - crassa._ 4. _Tellina tenuis._ 5. _Donax politus_] - -The shells of the genus _Psammobia_ are popularly known as Sunset -shells, being prettily marked with radiating bands of pink or other -tint, reminding one of the beams of the sun when setting in a cloudy -sky. In these, too, the ligament is very prominent, and the shell gapes -slightly at both ends. - -The same family contains the pretty little Wedge shells, which are so -called on account of their triangular form, and constitute the genus -_Donax_. These shells, which are seldom much over an inch long, are very -common on some of our sandy beaches, being washed up in considerable -numbers after the animals have died, but the specimens are seldom -perfect. The molluscs themselves are burrowers, and live in the sand, at -and just below low-water mark; and, as they usually burrow to a depth of -only a few inches, are easily obtained alive. - -The shells are rather thin, closed at both ends, blunt and rounded at -the anterior end, but straight and more pointed at the shorter -posterior end; and the margins of the valves are very finely grooved in -such a manner as to resemble the milling of a coin. Each valve has two -central hinge teeth, with one long lateral tooth on each side; and the -ligament is external and prominent. The lobes of the mantle are fringed; -the siphons are separate and diverging, but shorter and thicker than in -most of the other _Tellinidae_, and the foot is comparatively large, -flattened, and pointed. - -The genus contains many species, the commonest being, perhaps, _D. -anatinus_, the colour of which is yellowish, banded with brown, and -marked by a number of radiating white lines. This colour, however, is -due entirely to the thin, shining epidermis that completely covers the -valves; and if this is rubbed off the shell itself will exhibit a pale -pinkish tint. Another common species (_D. politus_) may be recognised by -the broad patch of white running from the hinge to the margin, on the -posterior side of the middle of each valve. - -The family _Mactridae_ contains some British shells popularly known as -Trough shells, and the family name itself is derived from the word -_mactra_, which signifies a kneading trough. In this group the shells -are all more or less triangular in form, with the valves equal, and are -either closed or very slightly gaping. The ligament, perhaps more -correctly designated the cartilage, is generally internal, and contained -in a deep triangular hollow; and the shell is covered with epidermis. -The mantle of the animal is open in front, and the siphonal tubes are -united and fringed. The foot is usually large and flattened. - -The typical genus, _Mactra_, contains some common molluscs that bury -themselves just beneath the surface of sandy beaches; and these are so -abundant in some parts of Great Britain that they are used largely for -feeding pigs. Some of the mactras are remarkable for the great power and -extensibility of the foot, which, in some cases, is used so vigorously -that the animal turns itself quickly over, or even leaps on the ground. - -Our example of this genus is _M. stultorum_, which is a very common -object of the shore. Its colour is very variable, usually some shade of -grey or brown, and marked by radiating white lines. - -The Otter shells (_Lutraria_), of which we figure one species, are much -like the _Mactrae_ in structure, and are usually included in the same -family, but in some respects they resemble the _Myacidae_ or Gapers. The -shell is oblong rather than triangular, and gapes at both ends; and the -animal buries itself deep in sand or mud, principally in the estuaries -of rivers, from low-water mark to a depth of about ten fathoms. The -shells are not very common objects of the shore, for they are found only -in muddy places, and those of the commonest species (_L. elliptica_) are -too large and heavy to be washed ashore in the sheltered estuaries where -they abound. - - [Illustration: FIG. 142.--1. _Lutraria elliptica._ - 2. PART OF THE HINGE OF _Lutraria_, SHOWING THE CARTILAGE PIT. - 3. _Macra stultorum._ 4. INTERIOR OF SAME SHOWING PALLIAL LINE] - -We now leave the burrowers, to consider a family of molluscs that move -about somewhat freely by means of a flattened tongue-shaped foot, and -which only rarely fix themselves in any way. The shells of the group are -popularly known as Venus shells, probably on account of the beauty of -some of the species, and the family in question as the _Veneridae_. - -The shells of the various species are usually of a graceful oval or -oblong form, frequently marked by chevron-shaped lines in pretty -colours, and distinctly grooved along the lines of growth. The ligament -is external, the hinge has usually three diverging teeth in each valve, -and the pallial line is sinuated. - -The principal genus is _Venus_, in which the shells are ovate in form, -thick, and smooth, and the margins of the valves are minutely -crenulated. The genus is a very large one, and contains several British -species, two of which we represent in the accompanying illustrations. - -Allied to these is the larger but pretty shell _Cytherea chione_, which -inhabits deep water off the southern coasts, to about one hundred and -fifty fathoms. It is much like the _Venus_ shells in form, but the -margins are not crenulated. - - [Illustration: FIG. 143.--_Veneridae_ - 1. _Venus fasciata._ 2. _Venus striatula._ 3. _Tapes virgineana._ - 4. _Tapes aurea_] - -The same family (_Veneridae_) contains the large genus _Tapes_, so called -because many of its shells are marked in such a manner as to recall the -patterns of tapestry. The general form of these shells is oblong, and -the margins are quite smooth. They are frequently washed up on the -beach, especially during storms, but the animals may be found alive at -low water, buried in sand, or hiding in the crevices of rocks or among -the roots of the larger sea weeds. The mantle is open at the anterior -end, and the siphons are either quite distinct or only partly united. - -Some of the shells are very prettily coloured. One (_T. aurea_) receives -its name from the yellow ground, which is variously marked by deeper -tints; another (_T. decussata_) is so called on account of the cross -grooves with which the shell is sculptured; and a third (_T. -virgineana_), which inhabits the muddy bottoms of deep water, is -prettily marked by radiating bands that run from the umbones to the -ventral margins. - -We now come to the family _Cyprinidae_, in which the shell is regular in -form, oval or elongated; and the valves, which are equal in size, are -thick and solid, and fit closely. The teeth are beautifully formed, the -central ones numbering from one to three in each valve, and the pallial -line is not sinuated. The mantle lobes are united on the posterior side -by means of a kind of curtain that is pierced by two siphonal openings. -There are two gills on each side, united posteriorly, and the foot is -tongue-shaped and thick. - -The typical genus--_Cyprina_--contains a large mollusc (_C. islandica_), -which is moderately common round our shores, especially in the north, -but is not often seen above low-water mark, except when washed up by -storms. The shell is oval and thick, with the umbones prominent and -turned towards the posterior side, and the ligament is strong and -prominent. It is entirely covered with a thick epidermis, of a rich -brown colour, often exhibiting a fine silky gloss, especially near the -margins. The interior of the shell is white, and the adductor -impressions oval and polished. - -The same family includes some smaller shells that inhabit deep water, -and are therefore not commonly seen on the beach. Among these are two -species of the genus _Astarte_, one of which is deeply furrowed in a -direction parallel with the margins; also _Circe minima_, which seldom -exceeds half an inch in length. Although so small compared with -_Cyprina_, these shells may be identified by their clothing of -epidermis, together with the family characteristics given above. - -The _Cyprinidae_ also contains the interesting Heart Cockle (_Isocardia -cor_), the form of which is so characteristic that identification is -easy. The heart-shaped shell is thick and strong, and is swollen out in -such a manner that the umbones are wide apart. These latter are also -curved into a spiral form, and the ligament between them is prominent. -The colour of the shell is variable, the epidermis being of any shade -from a yellow to a dark brown. The foot is small and pointed, and the -siphons fringed. - -The Heart Cockle burrows in sand by means of its foot, going down just -far enough to bury the whole of its shell, and always leaving its -siphons exposed at the surface. It inhabits deep water, and is not -likely to be obtained without the use of the dredge or trawl. - - [Illustration: FIG. 144.--_Cyprinidae_ - 1. _Cyprina islandica._ 2. _Teeth of Cyprina._ 3. _Astarte - compressa._ 4. _Circe minima._ 5. _Isocardia cor_] - -The molluscs of the family _Lucinidae_ are found principally in tropical -and sub-tropical seas, ranging from the shore to a very great depth, but -a few are moderately common in our own waters. They are closely allied -to the _Cyprinidae_, but the shell is round rather than oval, and is -obliquely grooved inside. The mantle lobes of the animal are not united -on the ventral side, but at the posterior end they are continuous, -except where they form one or two siphonal openings. The foot is long -and of almost the same thickness throughout when extended; and the -gills, numbering either one or two on each side, are large and thick. In -all the members of this family, as in the last, the pallial line of the -shell is simple. None of the shells are really common objects of our -shores, since the animals inhabit deep water, some of them moving about -freely on the bottom, while others moor themselves by means of a byssus. - -We shall take only one example of the family--_Galeomma Turtoni_--the -generic name of which means 'weasel eye.' This pretty little mollusc may -be found on our southern coasts, where it often moors itself to the -rocks or weeds by means of its silken byssus; or, having broken itself -away from its temporary place of rest, creeps freely on the bottom by a -long, flattened foot, applied closely to the surface over which it -travels, and used much in the same way as the broad foot of a snail or -whelk, its valves being all the time spread out nearly in the same -plane. - - [Illustration: FIG. 145.--_Galeomma Turtoni_] - -The shell itself is oval, with central umbones, and is covered with a -thick epidermis. The mantle lobes are united behind, where they form a -single siphonal opening; and the margins are double, with a row of -eye-like spots on the inner edge of each. - -The true Cockles, some few species of which are known to almost every -one, constitute the family _Cardiadae_, so called on account of the -cordate or heart-shaped form of the shell as viewed from the anterior or -posterior side. The shell is regular, or nearly so, and the valves, -which are equal, are ornamented with prominent rays that run from the -umbones to the margin. The ligament is short, strong and prominent, and -the valves fit closely by the interlocking of their crenulated margins, -or gape slightly on the posterior side. There are two central teeth in -each valve, and a long lateral tooth both on the anterior and posterior -sides. The mantle lobes are open in front, with the margins plaited, and -the siphons, which are usually short, are provided with a number of -little tentacles. The foot is large and powerful, and is usually curved -into the form of a sickle. - -Although the general nature of the common edible cockle (_Cardium -edule_) is so well known even to the inhabitants of inland towns that a -description may seem out of place here, yet it is possible that but few -of our readers have ever taken the trouble to place the animal in a -vessel of sea water, either obtained direct from the sea or artificially -prepared, for the purpose of studying its movements or other habits; -and it will be well to remember that this and several other species of -edible molluscs which reach our towns alive may be very conveniently -studied at home, and often at times and seasons when work at the -sea-side is undesirable or impossible. - - [Illustration: FIG. 146.--1. _Cardium pygmaeum._ 2. _Cardium fasciatum._ - 3. _Cardium rusticum_] - -The edible species referred to lives in banks of sand or mud, buried -just below the surface, and frequently in spots that are exposed for -several hours between the tides. They are usually obtained by means of a -rake similar to that used in our gardens. - - [Illustration: FIG. 147.--_Cardium aculeatum_] - -On the coasts of Devon and Cornwall we find a much larger species, also -valued as an article of diet, and known locally as the Prickly Cockle -(_C. aculeatum_). Its shell is beautifully formed, the rays being very -prominent, each bearing a number of calcareous spines arranged in a -single row. We give an illustration of this species, together with two -sketches to show the nature of the teeth of the shell. - -In addition to the two species named, we have the red-footed, _C. -rusticum_, which can suddenly turn itself over by the action of its -powerful pedal organ; the Banded Cockle (_C. fasciatum_), a very small -species distinguished by the brown bands of the shell; and a still -smaller one (_C. pygmaeum_), with a triangular shell, occurring on the -Dorset and Devon coasts (fig. 146). - -Passing now to the _Asiphonida_, we deal first with the family _Arcadae_. -These include a number of shells which, though very variable in general -form and appearance, may all be recognised by the long row of similar -comb-like teeth that form the hinge. The shells of this group are -regular in form, with equal valves, and are covered with epidermis. The -mantle of the animal is open, the gills are united by a membrane behind, -and the foot is large, curved, and grooved. - - [Illustration: FIG. 148.--_Pectunculus glycimeris_, WITH PORTION OF - VALVE SHOWING TEETH, AND _Arca tetragona_] - -One of the prettiest shells in the family is _Pectunculus glycimeris_, -which reaches a length of about two inches. The shell is grooved in the -direction of the lines of growth, and there are also very delicate -striations running radially from umbones to margin; and the ground -colour of white or pale yellowish is beautifully mottled with reddish -brown. We give a figure of this species, together with a drawing of the -peculiar and characteristic teeth, but a more typical shell of this -family may be seen in the Noah's Ark (_Arca tetragona_). This shell is -almost quadrate in form, swollen, and strongly ribbed. The hinge is -straight, with many comb-like teeth--increasing in number with the age -of the shell; and the umbones are separated by a diamond-shaped -ligament. The foot of the animal is heeled--that is, it has a creeping -surface that extends backwards as well as forwards; the mantle is -furnished with minute eyes (_ocelli_), and the animal has two distinct -hearts. We give a figure of this peculiar shell, and the other British -members of the same genus, though varying more or less in form, may be -recognised at once by the same general characteristics. - -In the same family we have the small nutshells (genus _Nucula_), which -are often dredged up from deep water in large numbers; and the elongated -shells of the genus _Leda_, also inhabitants of deep water; and, as -before stated, the affinities of all may be readily established by the -characteristic nature of the teeth. - -We now pass on to the family of Mussels (_Mytilidae_), of which the -common Edible Mussel (_Mytilus edulis_) is a typical species. In this -interesting group the shell is oval or elongated, with equal valves, and -is covered with a dark-coloured epidermis which is often distinctly -fibrous in structure. The umbones are at the anterior end of the shell, -which end is usually very narrow and pointed, while the posterior is -broad and rounded. The hinge has small teeth or none, and the ligament, -which is long, is internal. The shells of mussels consist of two -distinct layers; on the inner, which is often of a most beautiful pearly -lustre, may be traced the simple pallial line and the impressions of the -small anterior and the large posterior muscles. - -The mantle lobes of the animal are united only at a point between the -two siphonal openings. There are two elongated gills on either side, and -the foot is thick and more or less grooved. - - [Illustration: FIG. 149.--_Mytilus edulis_] - -Mussels inhabit salt, brackish, and fresh waters, generally attaching -themselves by means of a silken byssus, but sometimes concealing -themselves in ready-made holes, or in burrows of their own; and some -even hide themselves in a nest which they prepare by binding together -fragments of shells or sand. - -The edible mussel, which forms such an important article of diet, -especially among the poorer classes in our large towns, may be easily -distinguished from similar species of another genus by the very pointed -umbones, and the coarse and strong fibrous byssus by which it clings to -any solid object. It is found most abundantly on muddy coasts, and on -mud banks in the estuaries of rivers, generally in such situations as -are uncovered at low tide. The fry abound just below low-water level, -and grow so rapidly that they reach their full size in a single year. - -It is well known that a diet of mussels occasionally produces very -unpleasant and even dangerous symptoms in the consumer, and this result -has been attributed to the action of a particular organ of the animal -which has not been carefully removed before eating. This, however, is -not the case, as proved by the fact that the eating of these edibles is -usually perfectly safe when no such precautions have been taken. It is -highly probable that the deleterious character referred to is due to a -disease which sometimes attacks the mussels themselves, but the exact -nature of this has not been thoroughly made out. - - [Illustration: FIG. 150.--1. _Modiola modiolus._ 2. _Modiola tulipa._ - 3. _Crenella discors_] - -There is another genus (_Modiola_) containing several species commonly -known as Horse Mussels, and these may be distinguished from _Mytilus_ by -their habit of burrowing, or of constructing a nest by spinning together -various fragments. The shell, also, is more oblong in form, and much -swollen near the anterior end; and the umbones are not so pointed. The -epidermis covering the shell is of fibrous structure, and often extends -beyond the edges of the valves in the form of a fringe. - -Several species of Horse Mussels inhabit our shores, from low-water mark -to a depth of fifty fathoms, but none of them is used for food. The -commonest species is _Modiola modiolus_, which has a particularly strong -byssus, and its fibres generally bind together such a number of stones -&c. that the shell is completely hidden in the entangled mass. Other -British species include _M. barbata_, so called on account of the -peculiar fringed threads of the epidermis; _M. phaseolina_, in which -the epidermis threads are not fringed; and _M. tulipa_, named from the -streaks of crimson or purple that radiate from the umbones of the shell -and remind us of the colouring of the tulip flower. - -An allied sub-genus (_Crenella_) includes a few small British molluscs -the shells of which are crenulated on the dorsal margin behind the -ligament. The shells are short and swollen, and lined by a brilliant -pearly layer. One species (_C. discors_) is pale green, with radiating -lines from umbo to margin. It is common on many of our shores, but is -not easily found, as it hides at or below low water mark, in a nest -formed by binding together small stones. Other species, one of which is -black, are less abundant, and are not readily obtained except by the use -of the dredge. - -Before leaving this family we must refer to the remarkable _Dreissena -polymorpha_, sometimes called the Chambered Mussel, on account of the -chamber which is formed in the beak of the shell by means of a pearly -plate that stretches across it. This animal is not indigenous to -Britain, but was introduced from the East by trading vessels, either -attached by its silken byssus to timber that had been left floating in -water previous to being shipped, or to the bottoms of the ships. It -seems to thrive almost equally well in salt, brackish, and fresh waters, -and has spread very rapidly since its introduction. It is more commonly -found, however, in docks, canals, and rivers, and is on that account -usually described with the fresh-water species. - - [Illustration: FIG. 151.--_Dreissena polymorpha_] - -The form of the shell is very similar to that of _Mytilus_, but has no -internal pearly layer, and the valves are bluntly keeled. The mantle is -closed, the siphons short, and the foot small. - -Our next family--the _Aviculidae_--contains those shells that are -distinguished by peculiar flat processes on each side of the umbones, -one of which, the posterior, is generally wing-like in form. They are -popularly known as Wing Shells, and the family includes the so-called -Pearl Oysters. Most of the species are natives of tropical seas, but -several are common on our own shores. - - [Illustration: FIG. 152.--_Avicula_, AND _Pinna pectinata_] - -One species of the typical genus is sometimes found off the coasts of -Cornwall and Devon. The shell is very oblique, and the valves are -unequal, the right one, on which the animal rests, being somewhat -smaller than the left; and the epidermis is very scanty. The hinge is -long and straight, without teeth, and the cartilage is contained in -grooves. The interior of the shell is pearly. The posterior adductor -impression is large, and not far from the middle of the shell, while the -anterior, which is small, is close to the umbones. The mantle of the -animal is open, and the margins of the lobes fringed; and the small foot -spins a powerful byssus. - -Most of the British species of the family belong to the genus _Pinna_, -so called on account of the fins or wings on the dorsal side of the -shell. In this group the shell is more or less wedge-shaped, with equal -valves, and the umbones are quite at the anterior end, while it is -blunted and gaping at the other end. The hinge has no teeth. The margins -of the mantle are doubly fringed, and the byssus is extremely powerful. - -The Common Pinna (_P. pectinata_) is a very large mollusc, sometimes -measuring a foot in length, and is very abundant off the south-west -coast, where it moors itself vertically at the bottom of the water with -the pointed end buried, and the broad end gaping widely so as to expose -its body. It has been stated that fishes are frequently tempted to -intrude into the open shell for the purpose of devouring the animal -within, and that they are immediately crushed by the sudden closing of -the valves, which are pulled together by two large and powerful -adductors. - -We have already referred to the little Pea Crab that inherits the shell -of the Pinna, living permanently in the mantle cavity of the animal. - -The last family of the Lamellibranchs is the _Ostreidae_ or Oysters, of -which the edible oyster may be taken as a type. In this group the shells -are frequently unequal, and they lie on one side either free or adherent -to the surface below them; the hinge is usually without teeth. The -mantle is quite open, the gills number two on each side, and the foot is -either small or absent. - -The Edible Oyster is a type of the typical genus _Ostrea_, its -scientific name being _Ostrea edulis_; and as this mollusc may be -readily obtained at any time, it is a convenient species for the study -of the general characteristics of its family. Its shell is irregular in -form, and the animal always rests on its left valve, which is convex, -while the upper or right valve is either flat or concave. The lower -valve is also thicker and laminated in structure, and is attached to the -surface on which it rests. On examining the interior we find that the -shell is somewhat pearly in appearance, and that the edges of the mantle -lobes are finely fringed. The gills, too, are united with each other and -with the mantle on the posterior side, thus forming a distinct branchial -chamber. - -Oysters are found on banks at the depth of several fathoms, where they -spawn in early summer, and the fry or spats are collected in large -numbers and transferred to artificial beds or tanks, where they are kept -in very shallow water so as to be easily obtainable when required for -food. It is interesting to note, however, that their growth is slow on -these artificial grounds, the full size being attained in about seven -years, while, in the natural beds, they are full grown in a little more -than half that time. - -Native oysters--those that are reared on artificial beds--are of course -removed as soon as they are ready for the market, but those that live on -natural banks are often left undisturbed till their shells are thick -with age. The latter, too, are often destroyed in large numbers by the -boring sponge (p. 124), which so completely undermines the substance of -the shell that it finally breaks to pieces. - -In the genus _Anomia_ the lower valve is concave, and perforated with a -large oval hole very near the hinge, while the upper one is very convex, -but the shell is very variable in shape, since the animal sometimes -clings permanently to an object, and the shell, during its growth, -accommodates itself to the surface of that object. The use of the hole -is to allow of the protrusion of a set of muscles which proceed from the -upper valve, and give attachment to a plug or button, more or less -calcified, by which the animal clings. - - [Illustration: FIG. 153.--1. _Anomia ephippium._ 2. _Pecten tigris._ - 3. _Pecten_, - ANIMAL IN SHELL] - -One species (_A. ephippium_), known as the Saddle Oyster, is common on -some parts of our coast. It is seldom found on the beach at low water, -but the empty shells are often washed up by the waves. - -The same family includes the Scallops, which constitute the genus -_Pecten_. In these the shell is nearly round, with ears on each side of -the umbones, those on the anterior side being generally much more -prominent than the others, and both valves are ornamented by prominent -radiating ribs. The shell is often very prettily coloured, and the -animal rests on the right valve, which may be distinguished from the -left by its greater convexity, and by the presence of a notch under -the anterior ear. The hinge is straight, with a very narrow ligament, -and the internal cartilage is situated in a central pit. - - [Illustration: PLATE V. - - MOLLUSCS - - 1. Solen ensis - 2. Trivia Europaea - 3. Trochus umbilicatus - 4. Trochus magnus - 5. Littorina littorea - 6. Littorina rudis - 7. Haminea (Bulla) hydatis - 8. Tellina - 9. Capulus hungaricus - 10. Chrysodomus antiquus - 11. Buccinum undatum - 12 & 13 Scalaria communis - 14. Pecten opercularis - 15. Pecten varius - 16. Pecten maximus] - -The mantle of the animal is free, with double margins, the inner of -which forms a finely fringed curtain all round, and on this curtain are -a number of black eyes surrounded by very fine tentacles. The gills are -in the form of very thin crescents, and the foot is shaped like a -finger. - -Although the majority of scallops are inhabitants of tropical seas, -several species are to be found off our coasts, where they range from -depths of about four to forty fathoms, and the empty shells, often in -the most perfect condition, are frequently found on the beach. - -The Common Scallop (_P. maximus_) is largely used as food, and is -therefore a common object in the fishmonger's shop. Its colour is very -variable, and the shell has equal ears and about twenty radiating ribs. -The Quin (_P. opercularis_) is also an important article of diet in some -parts. - -Perhaps the prettiest of the British species is the Variable Scallop -(_P. varius_), so called on account of the very variable colour of the -shell, the ground tint of which may be almost anything between a very -pale yellow and a dark reddish brown, and this is irregularly patched -with some lighter colour. The chief distinguishing features of the -species are the spiny projections of the numerous ribs, most prominent -near the margin of the valves, and the presence of a permanent byssus, -which, in other species, occurs only in the young. Three of the species -named above are shown on Plate V. - -We may also mention the Tiger Scallop (_P. tigrinus_), the radiating -ribs of which are sometimes slightly formed, and which has only one ear -in each valve; and _P. pusio_, in which the adult shell is often greatly -altered in form. - -It may be noted, in conclusion, that all the species of this genus have -the power of swimming rapidly by flapping their valves--a mode of -locomotion very common among the bivalves especially during an early -stage of their existence. - -Before passing on to the univalve molluscs, we must refer briefly to a -group of animals that are enclosed in bivalve shells, and which were -once included with the Mollusca, but are now made to form quite a -distinct group by themselves. We refer to the Brachiopods, at one time -very abundant, as proved by the immense number of fossil shells embedded -in various stratified rocks, but now represented by only a few living -species. - -The shells of these animals are commonly known as Lamp Shells, on -account of their resemblance to an antique lamp; and although at first -sight they bear a general likeness to certain bivalve shells of -lamellibranchs, a close examination will show that not only the shell, -but also the animal residing within it, are both of a nature very -different from that of the molluscs with which they were at one time -supposed to be closely related. - - [Illustration: FIG. 154.--_Terebratulina._ THE UPPER FIGURE REPRESENTS - THE INTERIOR OF THE DORSAL VALVE] - -The valves of the shell are unequal, and are not placed respectively on -the right and left sides of the body of the animal, but rather on the -dorsal and ventral or upper and lower sides. The ventral shell is the -larger, and is produced into a beak which sometimes has a round hole -corresponding in position with the hole for the wick of an antique lamp, -and the dorsal or smaller valve is always imperforate. The hinge is a -perfect one, the junction of the two valves being so well secured by it -that it is impossible to separate them without injury. It is formed by -two curved teeth on the margin of the ventral valve that fit into -corresponding sockets on the dorsal. A few brachiopods, however, have no -hinge, the valves being secured by means of numerous muscles. The hole -in the shell serves for the protrusion of a pedicel or foot by means of -which the animal is enabled to attach itself. - -Two long arms, covered with vibratile cilia, and capable of being folded -or coiled, are attached at the sides of the mouth. They are practically -processes of the lips, mounted on muscular stalks, and attached to a -delicate calcareous loop on the dorsal valve; and serve not only to -produce water currents for the conveyance of food to the mouth, but also -answer the purpose of gills. - -The digestive system of a brachiopod includes an oesophagus that leads -into a simply formed stomach round which is a large digestive gland. The -heart has only one cavity, but the animal is provided with two smaller -and separate organs that assist in the propulsion of the blood, which -circulates through numerous blood spaces in the bristly mantle. - -About two thousand fossil species of brachiopods are known, extending -over a vast range of time; and the living species, numbering less than a -hundred, are found from shallow water to the greatest habitable depths. - -Since the reader is hardly likely to form any extensive acquaintance -with the Brachiopods, we shall illustrate our remarks by the -introduction of only one species--the Serpent's Head Terebratula -(_Terebratulina caput-serpentis_), which is found in deep water in the -North Sea. The interior of the dorsal valve, showing the calcareous loop -above referred to, is represented in fig. 154, as is also the exterior -of the shell, which is finely striated. The latter represents the dorsal -aspect of the shell in order to show the hole in the upturned beak of -the ventral valve. - - [Illustration: FIG. 155.--UNDER SIDE OF THE SHELL OF _Natica catena_, - SHOWING THE UMBILICUS; AND OUTLINE OF THE SHELL, - SHOWING THE RIGHT HANDED SPIRAL] - -We have now to consider the large group of head-bearing molluscs -(_Cephalophora_), the study of which forms a very important part of the -work of the sea-side naturalist; and while we deal with the general -characteristics of this group, the reader will do well to have before -him a few living typical species in order that he may be able to verify -as many as possible of the descriptions here given by actual -observation. These types may include such creatures as the whelk, -periwinkle, and limpet; or if marine species are not at hand at the -time, the garden snail, fresh-water snail, and slug will serve the -purpose fairly well. - -By far the large majority of Cephalopods are enclosed in a single shell, -though a few have a rudimentary shell or none at all. - -As is the case with the lamellibranchs, the shell is composed of both -animal and mineral substance, the latter being a calcareous deposit -secreted by the mantle of the animal. The shell is usually spiral in -form, as in the whelk, but sometimes conical (limpet) or tubular. - -Spiral shells are nearly always _dextral_ or right-handed; that is, if -we trace the direction of the spiral from the apex to the mouth, we -find that its turns or whorls run in the same direction as the hands of -a watch. A few, however, are _sinistral_, or left-handed, and -occasionally we meet with left-handed varieties of those species that -are normally of the right-handed type. The cavity of the shell is a -single spiral chamber which winds round a central pillar, and each whorl -of the shell generally overlaps the preceding one, the two being -separated externally by a spiral depression called the _suture_. - -Sometimes the coils of a shell are not close together internally, so -that the central column of the spiral is hollow, and opens to the -exterior at the base of the shell. In this case the shell is said to be -_umbilicated_, and the opening referred to is the _umbilicus_. In others -the spiral winds round a solid central pillar which is spoken of as the -_columella_. - - [Illustration: FIG. 156.--SECTION OF THE SHELL OF THE WHELK, SHOWING - THE COLUMELLA] - -The apex of the shell, sometimes called the _nucleus_, is the oldest -part, and represents what was once the whole. It is generally directed -backwards as the animal crawls, and in adult shells is often more or -less worn away by constant friction. We speak of the whorls as first, -second, third, &c., taking them in the order of their growth, and it -will generally be found that the last whorl is much larger than the -others, so much so that it contains the greater part of the body of the -animal; hence this one is commonly spoken of as the _body-whorl_, and -the others make up the _spire_ of the shell. - -The mouth of the shell is of different forms in different species, but -in the herbivorous kinds it is usually simple, while in the carnivorous -species it is notched or produced. The edge of the mouth (_peristome_) -is formed by an _outer lip_ which is usually sharp in young shells and -either thickened, reflected (turned outward), or inflected (turned -inward) in adults; also it may be considerably expanded, or ornamented -by a fringed margin. The _inner lip_ is that side of the peristome -adjacent to the central pillar of the shell. - -If we examine the external surface of several different shells, we find -that they are usually more or less distinctly furrowed or sculptured, -and that they are often marked by lines or bands of a colour different -from that of the ground tint. These furrows, lines, or bands sometimes -pass directly from the apex, across the various whorls, to the base of -the shell, in which case they are said to be _longitudinal_. If they -follow the course of the whorls, they are described as spiral; and if -parallel with the peristome, so that they mark the former positions of -the mouth of the shell, thus denoting the _lines of growth_, they are -said to be _transverse_. - -Most univalve shells are covered with epidermis, but in some instances -the animal, when extended, surrounds the exterior of the shell with its -mantle, as do the cowries, and then the outside of the shell is always -glazed. Other species keep their shells covered with the mantle, and in -these the shell is always colourless. - -The body of the head-bearing mollusc is attached to the shell internally -by one or more muscles, and if we examine the interior surface we are -generally able to distinguish the impressions or scars denoting the -points of attachment. - -The reader will have observed that the periwinkle, whelk, and other -univalves close their shells by a kind of lid when they retract their -bodies. This lid is called the _operculum_, and is constructed of a -horny material, often more or less calcified on the exterior, and is -attached to the hinder part of the foot. It sometimes fits accurately -into the mouth of the shell, but in some species it only partially -closes the aperture. The operculum, like the shell itself, often -exhibits distinct lines of growth which display the manner in which it -was built up. If these lines are concentric we know that the operculum -grew by additions on all sides; but if its nucleus is at one edge, and -the lines of growth widest apart at the opposite side, the growth must -have taken place on one side only. Some, even, are of a spiral form, -denoting that the additions were made continuously at one edge, and such -opercula may be right-handed or left-handed spirals. - -It will be noticed that in the above general description of univalve -shells we have introduced a number of technical terms which are printed -in italics, and this we have done advisedly, for the employment of these -terms is a very great convenience when giving descriptions of individual -shells, and we shall use them somewhat liberally in noting the -distinguishing characteristics of the families and genera; but before -entering into this portion of our work we must briefly note the general -features of the bodies of the _Cephalophora_. - - [Illustration: FIG. 157.--DIAGRAM OF THE ANATOMY OF THE WHELK, THE - SHELL BEING REMOVED - - _c_, stomach; _e_, end of intestine; _g_, gills; _h_, ventricle of - the heart; _a_, auricle; _f_, nerve ganglia; _b_, digestive gland; - _ft_, foot; _o_, operculum; _d_, liver] - -Sometimes these bodies are bilaterally symmetrical, as we have observed -is the case with the worms, but more commonly the organs on one side are -aborted, while the growth proceeds apace on the opposite side. Thus the -animal assumes a spiral form, being coiled towards the aborted side, -with the gills and other organs developed on that side only. As a rule -this curvature is such that the body takes the form of a right-handed or -dextral spiral, as we have already observed in the shells which cover -them, the mouth being thus thrown to the right, but sometimes it takes -the opposite direction. - -When one of these animals is extended and creeping, we observe that it -has a distinct head, furnished with a mouth below, and tentacles and -eyes above; also, if an aquatic species, the gills are more or less -prominent. Further, the exposed portion of the body is covered with a -leathery mantle, and the animal creeps on a broad, flattened surface -which is called the foot. - -The tentacles or feelers are usually retractile, and, when retracted, -are turned outside-in. Each one is provided with a muscle that runs from -the body internally to the tip; and, by the contraction of this muscle -the tentacle is involuted just in the same way as the finger of a glove -could be by pulling a string attached to the tip inside. In addition to -these tentacles, and the eyes and mouth previously mentioned, the head -is furnished with ear-sacs, which are little cavities, filled with fluid -containing solid particles, with nerve filaments distributed in the -walls. - -On the floor of the mouth there is a ribbon, supported on a base of -gristle, and covered with numerous minute teeth arranged regularly in -rows. The gristle is moved backwards and forwards by means of muscles in -such a manner that this 'lingual ribbon' acts like a rasp, and is -employed in scraping or tearing away portions of the substance on which -the animal is feeding. By this action the teeth are gradually worn away -in front, but this is of no consequence, for the lingual ribbon is -always growing forwards, the worn material being replaced by new growth -behind. - - [Illustration: FIG. 158.--A PORTION OF THE LINGUAL RIBBON OF THE WHELK, - MAGNIFIED; AND A SINGLE ROW OF TEETH ON A MUCH LARGER SCALE - _b_, medial teeth; _a_ and _c_, lateral teeth] - -The arrangement and form of the teeth are characteristic and important; -and since they afford one of the means by which we may trace the natural -affinities of similar species, they will be frequently referred to when -dealing with the principles of classification. For this reason the -student should be prepared to examine the lingual ribbons of molluscs -with the aid of a compound microscope as occasion requires. As a rule -the ribbon is easily stripped away from the floor of the mouth; and, if -placed in a drop of water and covered with a cover-glass, the teeth are -readily observed. Until a little experience has been gained the -observations may be confined to some of the larger species, in which the -ribbon is both large and easily obtained. In the common whelk, for -example, it often measures more than an inch in length. - -It is difficult to understand how the univalve mollusc manages to glide -along so rapidly and gracefully on its expanded foot when we observe it -from above, but the difficulty is cleared away when we see it creeping -on the side of a glass aquarium, or when we place it on a sheet of glass -and observe its movements from the other side. We then see that the foot -is in complete contact with the glass, and that a steady but rapid -undulatory movement is produced by the successive expansions and -contractions of the disc, brought about, of course, by the action of -muscular fibres. - -A few of the univalves are viviparous--that is, they produce their young -alive; but the majority lay eggs. The eggs are often enclosed in horny -cases, some of which may be commonly seen washed up on the beach, or -attached to rocks and weeds between the tide-marks. The larvae are always -enclosed in a shell, though they are sometimes wholly or partially -concealed by the mantle. The shell is usually closed by an operculum; -but as the animal advances in age the shell sometimes disappears -altogether, or is reduced to a mere shelly plate, as is the case with -the land and marine slugs and sea lemons. The young of the -water-breathers always swim about freely by means of a pair of ciliated -lobes or fins, but these remain only for a brief period, after which the -animal settles to the bottom for a more or less sedentary existence. - - [Illustration: FIG. 159.--EGG CASES OF THE WHELK] - -The Cephalophora fall naturally into two fairly well-defined groups, -which we may describe as the air-breathers and the water-breathers. The -former breathe air direct from the atmosphere through an aperture on the -right side of the body, the air passing into a pulmonary organ or lung, -in the walls of which the bloodvessels ramify, and they include all the -land snails and slugs. The latter breathe by gills which are more or -less prominent on the sides of the body, and include all the fresh-water -snails, as well as the marine species which fall within our special -province. - -We shall first consider the class _Pteropoda_ or Wing-footed Molluscs, -so called from the wing-like appendages that are attached to the side of -the mouth, or to the upper side of the foot, which is either very small -or altogether wanting. - -These Pteropods are in many respects lowly organised as compared with -the higher molluscs; and as they spend the whole of their existence in -the open sea, they can hardly be considered as falling within the scope -of the sea-side naturalist's work. Yet since their shells are -occasionally drifted on to the shore, and because a knowledge of them is -essential to the student of the mollusca, we shall briefly note their -principal characteristics. - -The pteropods are extremely abundant in some seas, occurring in such -vast numbers that they discolour the water for miles. They swim about by -flapping the pair of wings already referred to. They are known to form -an important article of the diet of the whale, and are also devoured in -enormous numbers by various sea birds; and they are themselves -carnivorous, feeding on various smaller creatures that inhabit the open -waters. - - [Illustration: FIG. 160.--PTEROPODS] - -In appearance they much resemble the young of higher species of -molluscs. The nervous system consists of a single ganglion situated -below the gullet, and the eyes and tentacles are either rudimentary or -absent. The digestive system includes a muscular gizzard provided with -teeth for the mastication of food, and a digestive gland or liver for -the preparation of a digestive fluid. The heart has two cavities, and -respiration is effected by a surface covered with minute cilia. This -surface is either quite external or is enclosed in a chamber through -which water freely circulates. - -The shell is very different from that of a typical head-bearing mollusc, -for it generally consists of two glassy, semitransparent plates, -situated dorsally and ventrally respectively on the body of the animal, -with an opening for the protrusion of the body, and others at the sides -for processes of the mantle; and it terminates behind in one or three -pointed processes. Sometimes, however, its form is conical or spiral, -with or without an operculum. We append illustrations of a few -pteropods, selecting for our purpose species that have been found in the -Atlantic. - -It will have been noticed from the above short description that the -pteropod is very unlike the typical Cephalophore as outlined in our -general remarks on the group, especially in the symmetrical form of both -body and shell and in the total or almost total absence of the foot; and -this distinction is so marked that the pteropods are often separated -from all the other _Cephalophora_ into a class by themselves, while all -the remainder are placed in a separate extensive class called the -_Gasteropoda_, because they creep on the ventral surface of the body, -the term signifying stomach-footed. - -These gasteropods are divided into four orders: the _Nucleobranchiata_, -in which the respiratory and digestive organs form a nucleus on the -posterior part of the back; the Opisthobranchiata, with gills more or -less exposed towards the rear of the body; the _Pulmonifera_, or -lung-breathing order; and the _Prosobranchiata_, in which the gills are -situated in advance of the heart. The third order includes all the land -snails and slugs, and does not therefore fall within the scope of our -work; but the remaining three consist either exclusively or principally -of marine species, and will be dealt with in the order in which they are -named. - -The Nucleobranchs are not really gasteropods in the strictest sense of -the term, for they do not creep along by means of their foot, but all -swim freely in the open ocean, always at the surface, and sometimes -adhere to floating weed by means of a sucker. In fact, the foot of these -creatures is greatly modified in accordance with their habits, one part -being often expanded into a ventral swimming fin, and provided with a -sucking-disc for adhesion, and another produced into a posterior fin for -locomotion. - -Like the pteropods, the nucleobranchs are purely pelagic, so that we can -hardly expect to meet with a specimen on or near the shore; and thus we -shall content ourselves with a brief notice of their general characters. - -The shell is very variable in size and form, and sometimes even entirely -absent. Large-bodied species often possess but a very small shell, while -some are able to entirely retract themselves and close the mouth of the -shell by an operculum. These animals are generally provided with a large -cylindrical proboscis, and the tongue has recurved teeth. The body is -usually very transparent, often so much so that the blood may be seen -circulating within it, and the nervous system is much more perfectly -developed than in the pteropods. The eyes, too, are perfectly formed. - -The presence of special breathing organs may seem to be superfluous in -such delicate and soft-bodied creatures as these, for it may be supposed -that all the oxygen required could be absorbed directly from the water -through their soft structures, as is really the case with many aquatic -creatures; and as a matter of fact some of the nucleobranchs possess no -gills, but others have these organs fully formed. - -Passing now to the true gasteropods, we shall first consider the -_Opisthobranchs_, which are commonly known as Sea Slugs and Sea Lemons. -Some of these have no shell at all, and even where one exists it is very -rudimentary, usually very small and thin, and concealed within the -mantle. The gills are either branched and tree-like, or are composed of -tufts or bundles of filaments; and, as the name of the order implies, -are situated towards the posterior part of the body. They are also -retractile, and when the animal is alarmed it will conceal its gills, -thus reducing its body to a shapeless, slimy mass, inviting neither to -sight nor to touch. - -The sea slugs are principally animal feeders, subsisting on small -crustaceans, other molluscs, &c.; the food being first reduced by the -rasping action of the teeth, and then masticated in a gizzard which is -provided internally with horny spines or hard, shelly plates. - -It will not be necessary to enumerate all the different families of this -order, especially as the species are mostly to be found beyond the -tide-marks, and are therefore obtained only with the aid of the dredge; -but we shall describe a few of the British species with a view of -showing the general characteristics of the animals. - -They are usually divided into two sections, those with exposed or naked -gills (_Nudibranchiata_) forming the first, and those in which the gills -are covered either by the shell or the mantle (_Tectibranchiata_) -comprising the second. - -In the Nudibranchs the shell exists only during the embryonic stage, and -the external gills are arranged on the back or along the sides. The -tentacles are not employed as organs of touch, but are probably -connected only with the sensation of smell, being provided with -filaments of the olfactory nerve; the eyes are small dark-coloured spots -embedded in the skin behind the tentacles. Various species are to be -found on all rocky coasts, where they range from low-water mark to a -depth of fifty or sixty fathoms, but a few are pelagic, living on the -surface of floating sea weeds. - -It is almost impossible to identify the species of nudibranchs from dead -specimens, for the classification of the section is based largely on the -arrangement of the gills, which are almost always retracted in the dead -animals. This is also the case even with living specimens when disturbed -or removed from the water; hence they should always be examined alive in -sea water, while the animals are extended and moving. - - [Illustration: FIG. 161.--NUDIBRANCHS - 1. _Doto coronata._ 2. _Elysia viridis._ 3. _Proctonotus - mucroniferus._ 4. _Embletonia pulchra_] - -It will be understood from the above statements that special methods -will be necessary when it is required to preserve specimens for future -study, the gills being always retracted when the animal is killed for -this purpose by any rapid process. We have found two methods, however, -that are fairly satisfactory in the majority of instances.--Place the -living animals in a suitable vessel of sea water, and leave them quite -undisturbed till they are fully extended, and then either _gradually_ -raise the temperature till they are dead, or introduce into the water, -cautiously, a solution of corrosive sublimate. In the latter case a much -larger proportion of the sublimate will be required than when used for a -similar purpose with freshwater molluscs. When the animals are dead it -will be found that their gills are more or less extended, sometimes -fully so, and they may then be transferred to diluted spirit or a two -per cent. solution of formaldehyde. - - [Illustration: FIG. 162.--NUDIBRANCHS - 1. _Dendronotus arborescens._ 2. _Tritonia plebeia._ 3. _Triopa - claviger._ 4. _AEgirus punctilucens_] - -In fig. 162 we represent four species. Two of these--_Triopa claviger_ -and _AEgirus punctilucens_--belong to the family _Doridae_, the members of -which are popularly known as Sea Lemons, and are distinguished by the -presence of plume-like gills situated on the middle of the back. Another -family (_Tritoniadae_), characterised by the arrangement of the gills -along the sides of the back, and by tentacles that can be retracted into -sheaths, is represented by _Tritonia plebeia_ and _Dendronotus -arborescens_ in the same figure, and by _Doto coronata_ in fig. 161. The -family _AEolidae_ also have their gills arranged along the sides of the -back, but they differ from the last in that their tentacles are not -retractile. They include the two species numbered 3 and 4 on fig. 161. -The remaining one on fig. 161--_Elysia viridis_--is a member of the -family _Phillirhoidae_, characterised by a pair of tentacles on the -dorsal side of the head and by the foot being either very narrow or -absent, the latter feature denoting that the animals are not adapted for -creeping on the bottom. In fact, several of the species of this family -swim freely by means of flattened tails. - -The Tectibranchs are similar in general structure, but are very -different in appearance, inasmuch as the gills, so prominent in the last -division, are here covered by the mantle, or by the shell, which is -often well developed. The latter is very variable in form, being of a -globular, twisted, spiral, or other shape, but is sometimes absent in -the adult. In fig. 163 we give a few examples of the shells of British -species; and one (_Bulla hydatis_) is shown on Plate V. - - [Illustration: FIG. 163.--SHELLS OF TECTIBRANCHS] - -We now pass on to the largest and last order of gasteropods--the -_Prosobranchiata_--so called because the gills are situated in front of -the heart. This group is an important one to the sea-side naturalist, -since it contains nearly all the univalve molluscs that are common -between the tide-marks of our shores, as well as some abundant species -that are protected by a shell of several distinct parts. In nearly all -of them the abdomen is well developed, and the shell is sufficiently -large to cover the whole animal when the latter is retracted; and the -gills, which are either pectinated (comb-shaped) or plumed, are lodged -in the chamber formed over the head of the animal by the mantle. - -The order is often divided into two sections--the _Holostomata_ or Sea -Snails, in which the margin of the aperture of the shell is entire, and -the _Siphonostomata_, in which the margin of the mantle is prolonged -into a siphon by which water passes into the gill chamber. This division -does not seem to be very satisfactory, as the sections are not separated -by very prominent natural characteristics, but it becomes convenient on -account of the great extent of the order. - -In the _Holostomata_ the shell is either spiral, conical, tubular, or -composed of several valves, and the spiral forms are usually closed by -a horny or shelly operculum of the spiral kind. The head is provided -with a proboscis that is generally non-retractile, and the gills usually -extend obliquely across the back, or are attached to the right side -behind the head. - -We shall first consider the lower forms, starting with the family -_Chitonidae_, the animals of which, as the name implies, are covered with -a shell that resembles a coat of mail. - -Some of these creatures are very common on our rocky coasts, and yet -their nature is such that they are liable to be overlooked by those who -are not acquainted with their appearance and habits. The shell is oval -or oblong, often so coloured as to closely resemble the rocks and stones -over which they crawl; and the animal is so inactive when left exposed -by the receding tide, and its flat under surface so closely applied to -that on which it rests, that it looks merely like a little convexity of -the rock. But after a few have been discovered the eye becomes -accustomed to their appearance, and large numbers may be obtained in a -short space of time. - -The shell will be seen to consist of eight transverse, curved plates, -overlapping each other at their edges, and all enclosed in a leathery -mantle, which also forms a projecting margin all round. The middle six -plates are different from the first and last in that they are grooved in -such a manner that each one displays a dorsal and two lateral areas. - -The animal holds on tightly to the rocks by its large creeping disc-like -foot, but may be removed without injury by forcing a knife-blade under -the margin of its shell. When examined it will be found that it has not -a well-formed head like the majority of the gasteropods, and both eyes -and tentacles are wanting. The gills form a series of lamellae round the -posterior end of the body, between the edge of the foot and the mantle; -and it is interesting to note that the Chitons further justify the low -position assigned to them among the gasteropods by their possession of a -simple, central, tubular heart, similar to that of worms. - -Perhaps the commonest of the British species is _Chiton cinereus_. Its -colour is a dull grey, but the ground is variously mottled, often in -such a manner as to give it a protective resemblance to its -surroundings. _C. ruber_ is the largest of our species: its shell is -variously mottled with shades of yellow and brown; _C. fascicularis_ is -bristled. Another rather common species (_C. laevis_) is distinguished by -the glossy appearance of the dorsal portion of the shell. - -It will have been observed that the chitons differ from the majority of -gasteropods in that their shells and bodies are both bilaterally -symmetrical, and the same is true of the next family--_Dentaliadae_, -which derive their name from the tooth-like form of their conical -shells. They are popularly known as the Tooth Shells, and although they -generally live beyond low-water level, they may sometimes be seen alive -on the beach, and the empty shells are often washed up by the waves. - -The shells (fig. 165) are curved, and open at both ends, the narrower -extremity being the posterior. The mouth is circular, and the outer -surface is quite smooth or grooved. - - [Illustration: FIG. 164.--CHITON SHELLS] - - [Illustration: FIG. 165.--SHELLS OF _Dentalium_] - -In these animals, too, the head is imperfectly formed, without eyes or -tentacles. The foot is conical and pointed, with two symmetrical side -lobes; and the gills, also two in number, are symmetrically disposed. -The margin of the mouth is fringed, and the animal is attached to the -shell near the posterior end. - -The _Dentaliadae_ are carnivorous, subsisting on minute molluscs, -foraminifera, &c., and generally live on sandy or muddy bottoms, in -which they sometimes bury themselves. - -Our next family includes the familiar Limpets, and is designated -_Patellidae_ on account of the resemblance of the conical shell to a -little dish. In these the apex of the cone is not central, but situated -more or less towards the anterior; and the muscular impression within is -shaped like a horseshoe, with its open end turned to the front. - -Unlike the members of the preceding families, the limpets have a -well-formed head furnished with both eyes and tentacles, the former -situated at the bases of the latter. They have a horny upper jaw, and -the tongue, which is very long, is supplied with numerous hooked teeth. -The foot is a very large disc, as large as the shell, and the gills -consist either of one or two branched plumes, or of a series of lamellae -almost or entirely surrounding the animal between the shell and the -margin of the mantle. - -The reader has probably experienced the difficulty of detaching a limpet -from its hold on the rocks. The tenacity of the grip is not due to the -mere adhesive power of the foot itself, but to atmospheric pressure, the -effect of which is complete on account of the total exclusion of air -from under the disc of the foot; and when we remember that this pressure -amounts to fifteen pounds on every square inch of surface, we can -readily understand the force required to raise a large limpet from its -position. - - [Illustration: FIG. 166.--_Patellidae_ - 1. _Patella vulgata._ 2. _P. pellucida._ 3. _P. athletica._ - 4. _Acmaea testudinalis_] - -The Common Limpet (_Patella vulgata_) is found on all our rocky coasts -between the tide-marks, often at such a level that it is left exposed to -the air for eight or nine hours at a time. The apex of the shell of this -species is nearly central, and the exterior is sometimes nearly smooth, -but more commonly relieved by radiating ribs. - -Although the shell itself is not a particularly pretty object, it is -often rendered very beautiful and interesting by the various animal and -vegetable organisms that settle on it. Those shells that are left dry -for hours together are commonly adorned with clusters of small acorn -barnacles, while the limpets that have found a home in a rock pool and -are perpetually covered with water, often resemble little moving gardens -in which grow beautiful tufts of corallines or other weeds, as well as -polyzoa and other animal forms. - -It appears that limpets are not great travellers, the appearance of the -rock from which they have been removed being such as to point to a very -long period of rest. Those on hard rocks are generally situated on a -smooth surface just the size of the shell and generally worn slightly -below the surrounding level by the constant friction of the shell; while -others that have settled on very rugged spots have their cones adapted -to the irregular surface. It has been suggested that the animals make -occasional short excursions from their chosen spot, but return again to -it; and whether or not this is the case, it is evident that they -frequently keep to one small spot for a considerable length of time. - -Limpets on chalk and other soft rocks are sometimes in circular pits so -deep that even the apex of the shell is below the general level around; -and though it is possible that the abrasion is produced entirely by the -friction of the shell as the animal turns, yet, in the case of chalk, -the action may be partly due to the carbonic acid gas given off by the -animal as a product of respiration, for it is a well-known chemical fact -that this gas, in solution, has the power of dissolving calcareous -material. - -The other British Limpets include _P. pellucida_, which lives on the -fronds and stalks of the tangle, the form of the shell varying according -to that of the surface on which it rests; also the Horse Limpet (_P. -athletica_), the bold radiating ribs of which are irregularly notched; -and _Acmaea testudinalis_--the Tortoiseshell Limpet, with reddish-brown -mottlings on the exterior, and a dark-brown patch at the apex within. -The last-named species lives principally on sea weeds, and has a single -pectinated gill in the cavity between foot and mantle, which is -protruded on the right side when the animal is extended. This latter -feature is interesting since it shows a tendency to that one-sided -development already referred to as characteristic of the typical -gasteropod, resulting in the spiral form of the adult. - -In the limpets the lingual ribbon is proportionately long, and is easily -removed for examination. In _P. vulgata_ it may exceed an inch in -length, and the teeth are arranged in rows each of which contains four -central, with laterals on either side, while in _Acmaea_ there are only -three laterals on each side of the central line. - -Other so-called limpets belong to separate families. Thus we have the -Cup-and-Saucer Limpet and the Bonnet Limpet in the _Calyptraeidae_. Both -these differ from Patella in that the apices of their shells show a -tendency to assume a spiral form, thus denoting a somewhat closer -relationship to the more advanced univalves. They have distinct heads, -with prolonged muzzles, and well-formed antennae and eyes. The teeth of -the lingual ribbon are single, with dentated laterals on either side. - -The Cup-and-saucer Limpet (_Calyptraea sinensis_) is so called on account -of a curved plate that projects from the interior of the shell, at the -apex; and though this plate takes the form of a half-cup rather than of -a cup, the whole shell has suggested the popular name, while the generic -name is derived from _calyptra_, which signifies a cap. This mollusc is -occasionally found among stones at low tide, but usually lives beyond -this line, thus necessitating the use of a dredge. The Bonnet Limpet -(_Pileopsis hungaricus_) is of similar structure and habit, but the -nucleus of the shell is a more decided spiral (see Plate V.). Both these -animals adhere to stones and rocks, and, like the common limpet, seldom -or never move from their selected sites; hence their shells are variable -in form, being adapted to the rock below, and the movements of the shell -often cause a little hollow to be scooped out of the softer materials. - - [Illustration: FIG. 167.--_Calyptraea sinensis_] - -Yet other limpets belong to the next family _Fissurellidae_, which is -characterised by a perforation or a notch in the shell. In these, too, -the shell is conical, with a tendency to assume the spiral form, but the -curve of the nucleus, which is always apparent in the young shell, -frequently disappears as the growth proceeds. - - [Illustration: FIG. 168.--_Fissurellidae_ - 1. _Puncturella noachina._ 2. _Emarginula reticulata._ - 3. _Fissurella reticulata_] - -In the Keyhole Limpet (_Fissurella reticulata_) which is found chiefly -on our southern shores, the perforation is at the summit of the shell; -but as the animal grows the hole increases in size, encroaching on the -curved nucleus until the latter quite disappears. In the genus -_Puncturella_ the perforation is just in front of the recurved apex, and -is surrounded by a rim internally; while in the Notched Limpets (genus -_Emarginula_) it is represented by a fissure on the anterior _margin_ of -the cone. In all, however, the hole or notch serves the same purpose, -for it is the means by which water enters the siphon. - -It is doubtful whether we ought to claim the beautiful Ear shell -(_Haliotis tuberculata_) as one of our own, but it is generally included -among the British molluscs on the ground that it is abundant on the -coast of the Channel Islands, where it is called the Omar; and it is -certainly too beautiful an object to be excluded from the British -species without ample cause. - - [Illustration: FIG. 169.--_Haliotis_] - -It belongs to the family _Haliotidae_, and our illustration will show -that the shell is less elevated than that of limpets, and that the -spire, though not prominent, is a fairly well-formed spiral. All along -the outer lip of the very large aperture is a series of perforations, -occupying the summit of a prominent, spiral ridge, and becoming -gradually smaller and smaller towards the spire. The whole shell is -pearly in structure, and displays a great variety of rich colouring. It -is used largely for inlaying and other ornamental purposes, and for -making the so-called pearl buttons. The animal is used largely as an -article of food in the Channel Islands, but it is of so tough a nature -that it requires a vigorous beating previously to being cooked. - - [Illustration: FIG. 170.--_Ianthina fragilis_] - -The same family contains the beautiful violet _Ianthina_, which also is -not a British species, but a free-swimming oceanic snail. It is, -however, occasionally drifted to our shores, though generally in an -imperfect condition. In the Atlantic and the Mediterranean it sometimes -abounds in such multitudes as to distinctly colour the surface of the -sea. - -It will be seen that the shell is round, with a well-formed spiral. The -spire is white, but the base is of a deep violet colour. The animal is -very remarkable in some respects. In the first place, though it has -pedicels similar to those on which the eyes of the higher univalves are -placed, yet it has no eyes. Then the foot, which is in itself small, -secretes a float or raft so large that it cannot be retracted into the -shell, with numerous air vesicles to render it light, and the -egg-capsules of the animal are attached to the underside of this. The -animal has no power of sinking, but lives exclusively at the surface; -and, when disturbed, it exudes a violet fluid that colours the -surrounding water. It is apparently the only gasteropod that lives in -the open sea and has a large and well-formed spiral shell. - -Passing now to the family _Turbinidae_ we meet with turbinated or -pyramidal shells that are of a brilliant pearly lustre within, and -frequently without also when the epidermis is removed. The animals -inhabiting them have well-formed heads with a short muzzle, long and -slender tentacles, and eyes mounted on peduncles. The sides are -ornamented with fringed lobes and several tentacle-like filaments, and -the aperture of the shell is closed, when the animal is retracted, by a -spiral operculum. They are all vegetable feeders; and, as is usual with -the plant-eating molluscs, the teeth on the lateral portions of the -lingual ribbon are very numerous. - -We have a few common species belonging to this group, mostly members of -the typical genus _Trochus_ and commonly known as Top Shells. In these -the shell is a pyramid formed of numerous flat whorls, with an oblique -and rhomboidal aperture. Of the three species figured (including two on -Plate V.) _T. umbilicatus_ and the Large Top (_T. magnus_) are -umbilicated, the umbilicus being very large in the latter; and the -former is characterised by the zigzag greyish or reddish markings that -run radially across the whorls. The other (_T. zizyphinus_) is usually -of a yellowish or pink colour and has no umbilicus. - -The same family contains the pretty little Pheasant Shell (_Phasianella -pullas_), which is richly coloured with red, brown, and yellow on a -light ground; and _Adeorbis subcarinatus_, shown in the same group. - -The well-known Periwinkle (_Littorina littorea_) and the species to the -right of it on Plate V., belong to the family _Littorinidae_, the -members of which are similar in structure and habit to _Trochus_, but -the shell is usually more depressed, and is never pearly. The shell of -the Periwinkle is thick, having but few whorls, and is not umbilicated; -and the lingual ribbon, which is coiled up on the gullet, contains no -less than about five hundred rows of teeth; but only a little more than -twenty of these rows are in action at any one time, the remainder being -a reserve stock to come into active service as the ribbon grows forward. -In the genus _Lacuna_ there is a narrow umbilicus, and the aperture of -the shell is semilunar in form; and the species of _Rissoa_ are very -small, with white or horny shells, much more pointed and having more -whorls than those of the _Littorina_. - - [Illustration: FIG. 171.--1. _Trochus zizyphinus._ 2. UNDER SIDE OF - SHELL. 3. _Trochus magnus._ 4. _Adeorbis subcarinatus_] - - [Illustration: FIG. 172.--_Rissoa labiosa_ AND _Lacuna pallidula_] - -Our next illustration shows three shells of the family _Turritellidae_, -so named from the resemblance of the shells to a tower or spire. The -form indeed is so characteristic that they can hardly be mistaken. It -will be seen that _Turritella communis_ is striated spirally, while the -surface of _Scalaria communis_ (Plate V.) is relieved by strongly marked -transverse ribs. Both these species are very common, and the latter is -peculiar for its power of ejecting a dark purple fluid when molested. -The other representative of the family--_Caecum trachea_--has a shell -something like that of _Dentalium_ (p. 238), being cylindrical and -tubular, but it differs in being closed at one end. - - [Illustration: FIG. 173.--SECTION OF SHELL OF _Turritella_] - - [Illustration: FIG. 174.--_Turritella communis_ AND _Caecum trachea_] - -In the succeeding shells, of the family _Cerithiadae_, the spire is also -considerably produced, so much so that some of the species closely -resemble the Turret shells, but they are distinguished by usually having -an expanded lip, at least in the adult form; and the mouth is channelled -in front, and sometimes also behind. The animals of the group have short -muzzles that are not retractile, the tentacles are wide apart, and the -eyes are mounted on short pedicels. The median teeth are arranged in a -single row, with three laterals on either side of each. - - [Illustration: FIG. 175.--_Cerithium reticulatum_ AND _Aporrhais - pes-pelicani_] - -_Cerithium reticulatum_ receives its generic name from its appearance to -a small horn, and the specific name refers to the netted appearance of -its surface due to the presence of numerous little tubercles arranged in -rows--a feature that serves to distinguish it from the small Turret -shells. It is a common shell, as is also the other representative of the -family illustrated, but the latter is rendered conspicuous by the -enormously expanded lip that has earned for it the popular name of Spout -Shell. Its scientific name is _Aporrhais pes-pelicani_, and the -application of the specific term will be understood when the shell is -viewed from above, for the expanded lip is drawn out into long -finger-like lobes that suggest the foot of a bird. This is a very solid -shell, sometimes reaching a length of two inches; and the animal -inhabiting it is carnivorous. - - [Illustration: FIG. 176.--_Aporrhais pes-pelicani_, SHOWING BOTH SHELL - AND ANIMAL] - -We have yet some turreted shells to deal with, belonging to the family -_Pyramidellidae_, but they need not be confused with the preceding groups -if carefully examined. In the first place, the aperture of the shell is -very small; and the operculum, instead of being spiral, as in the -turreted shells before mentioned, is imbricated or made up of parallel -layers denoting that the growth took place on one side only. Another -distinguishing feature is seen in the nucleus--that small portion of the -spire that was developed within the egg--which is sinistral or -left-handed. In addition to this, the animal has broad, ear-like -tentacles, a retractile proboscis, and a lingual ribbon without teeth. - -The British species of this family belong principally to the genera -_Odostomia_, characterised by a tooth-like fold of the columella; -_Eulima_, containing small, white, polished shells with numerous level -whorls; and _Aclis_, with little polished shells not unlike -_Turritella_. - - [Illustration: FIG. 177.--1. _Odostomia plicata._2. _Eulima polita._ - 3. _Aclis supranitida_] - -The last family of the _Holostomata_ is the _Naticidae_, the shells of -which are almost globular, with only a few whorls, and a small, blunt -spire. The mouth is semilunar in form, and the lip sharp. The proboscis -of the animal is long and retractile, and the foot large; but perhaps -the most characteristic feature is the presence of large mantle lobes -which hide some of the shell when the animal is crawling. In _Natica_ -(fig. 155), the typical genus, the shells are somewhat thick and smooth, -with a large umbilicus. As the animal crawls a large fold of the mantle -is reflected back over the head, completely covering it, and apparently -obstructing its view; but this is not the case, for the creature has no -eyes. _Natica_ is very abundant on some sandy beaches, where it devours -small bivalves and other animals; and it is frequently washed up alive -by the waves. Its shell is also a favourite one with hermit crabs. Its -eggs, all connected together in a spiral band, may often be seen -stranded on sandy coasts. Several species of Natica are found on our -shores. An allied mollusc--_Velutina laevigata_, so called on account of -the velvety epidermis that clothes the shell, completely surrounds the -shell by its mantle folds when creeping. - -The _Siphonostomata_ form a much smaller section than the last, and its -members are distinguished mainly by the presence of a true siphon, -formed by the prolongation of the mantle margin, and serving to convey -water into the gill chamber. In all these the shell is spiral, usually -without an umbilical opening, and the margin of the mouth is prolonged -into a canal or distinctly notched. The operculum is horny, and lamellar -or imbricated. The animal has a retractile proboscis, and the eyes or -eye-pedicels are joined to the tentacles. All the species of this -division are marine. - - [Illustration: FIG. 178.--_Cypraea (Trivia) europaea_] - -We will first take the family _Cypraeidae_, which contains the familiar -Cowries, these forming the lowest group of the division. An examination -of the shells may at first seem rather puzzling, for the spire is -concealed, and the whole is convoluted in such a manner as to make the -mouth long and narrow, with a channel at either end. The outer lip is -also thickened and bent inward, and there is no operculum. - -The animal itself is particularly interesting, for, as it creeps along -on its broad foot, abruptly shortened in the front, the mantle lobes -bend over the top, meeting along the middle line, where they are usually -fringed with little tentacle-like processes; and, as a result, the whole -shell is beautifully enamelled on the outer surface. In all the Cowries -the central teeth are single, and the laterals are arranged either in -twos or threes. - -Perhaps the commonest representative of this family is the pretty little -_Cypraea_ (_Trivia_) _europaea_ (Plate V.), the shells of which are -sometimes washed up in large numbers on sandy beaches. The animal lives -mainly below low-water level, but it may often be found in the larger -rock pools, creeping rapidly over the tangles, and may be easily secured -with the aid of a net. - -In the same family we have the little _Erato_ (_Marginella_) _laevis_, -the white shell of which is minutely furrowed along the lips; and also -_Ovulum patulum_ (_Calpurna patula_), so called on account of its -fancied resemblance to a poached egg. - -We have also several species of Cone shells (family _Conidae_) on our -coasts, readily recognised by their form, which is a cone, with a long, -narrow aperture, partially closed by a minute operculum. As in the last -family, the foot is abruptly shortened in front. The head is very -prominent, with eyes situated on the tentacles. There are two gills, and -the teeth are arranged in pairs. - - [Illustration: FIG. 179.--1. _Ovulum patulum._ 2. _Erato laevis_] - - [Illustration: FIG. 180.--_Mangelia septangularis_ AND _Mangelia - turricula_] - -The Conidae are principally inhabitants of tropical seas, where some very -large species exist. Two of the British representatives, both common -shells, are shown in fig. 180. - -Our next family (_Buccinidae_) is so well distributed on our coasts, that -it would be difficult, we imagine, to find a spot quite free from its -familiar forms. It contains all those creatures commonly known as -Whelks, Dog Whelks, and Dog Winkles, ranging from deep water almost to -high-water mark. - -In all these the shell is notched in front, or the canal is turned -abruptly upward. The foot of the animal is broad, the eyes are situated -either on the tentacles or at their bases, and there are two gill -plumes. - -All the species are carnivorous, and some are said to be very -destructive to mussels and young oysters. - -The Common Whelk (_Buccinum undatum_, Plate V.) lives in deep water, -whence it is dredged up largely for the market. Its clusters of egg -cases are washed up in large numbers on the beach, where they form one -of the commonest materials among the refuse at high-water mark. It is -not uncommon, also, especially after storms, to find the unhatched eggs -stranded by the waves, and these are so transparent that the embryos, -several in each capsule, may be seen within. The hole through which the -young escape may also be seen on the inner side. - - [Illustration: FIG. 181.--1. _Purpura lapillus._ 2. EGG CASES OF - _Purpura_. 3. _Nassa reticulata_] - -The Dog Periwinkle (_Purpura lapillus_) abounds on all our coasts and is -remarkable for the production of a dull crimson or purple fluid that may -be obtained from it by pressing on the operculum. This fluid turns to a -brighter colour on exposure to air, and is said to have been used -largely in former times as a dye. It will be seen from our figure that -the spire of this shell is shorter in proportion than that of -_Buccinum_; but both are alike in that the operculum is made up of -layers with a nucleus on the external edge. - -The other species figured is _Nassa reticulata_, popularly known as the -Dog Whelk, and characterised by a tooth-like projection of the inner lip -close to the anterior canal. It is very common near low-water mark, -where it may be seen crawling over the rocks on its broad foot, from -which project two hornlike appendages in front and two narrow tails -behind. - - [Illustration: FIG. 182.--_Murex erinaceus_] - -From the last family of the gasteropods (the _Muricidae_) we select two -common species--_Murex erinaceus_ and _Fusus antiquus_ (Plate V.). In -both these the anterior canal of the shell is straight and the posterior -wanting. The eyes are on the tentacles, and there are two plumed gills. -Both are carnivorous species, feeding on other molluscs; and the former -is said to bore through the shells of its prey with the prominent beak -of its shell. - -_Murex_ may be readily distinguished by the prominent longitudinal -ridges of the thick shell, its rounded aperture, and by the partly -closed canal running through the beak. It is known to fishermen as the -Sting Winkle; the other species is called the Red Whelk in some parts, -and in Scotland is known as the Buckie. Like the common whelk, it is -dredged largely for the market, and is said to be far more esteemed than -the former, from which it may be distinguished by the fusiform shape of -the shell and the long straight canal. - -We now pass to the last and highest class of the mollusca, called the -_Cephalopoda_ because they have a number of arms attached to the head, -round the mouth. Unlike the majority of molluscs they are bilaterally -symmetrical: and are much more highly organised, in some respects even -making an approach to the vertebrates. Thus they generally have an -internal hard structure, either horny or calcareous in structure, -representing the vertebral column, and the circulatory system consists -of arteries and veins, connected by minute capillaries. The corpuscles -of the blood are also similar in form to those of the vertebrates. -Externally they are all naked, with the exception of the nautilus and -argonaut of the warmer seas. - -The arms, so characteristic of the class, are eight or ten in number, -long and muscular, and provided with numerous suckers by which the -animal can cling with remarkable tenacity. These suckers are situated on -the inner surface of the arms, and the disc of each one displays a -series of muscular fibres, all converging from the circumference towards -the centre, which is occupied by a softer structure that works inwards -and outwards like the piston of a pump. Thus the suckers form a system -of exhausting air-pumps by which a vacuum can be produced, and the -tenacity of the grip, maintained by atmospheric pressure, is so great -that the arms, strong as they are, may be torn asunder by attempting to -pull them from their hold; and yet the animal can release its grip with -the greatest of ease by simply releasing the pistons of its pumps. - -The cephalopods are further distinguished by their very large, glaring -eyes, situated on the sides of the well-formed head, and by powerful -jaws that work in a vertical plane, like those of the vertebrates, but -somewhat resembling the beaks of certain birds. The tongue is also very -large and fleshy, and in part armed with numerous hooked spines or -teeth. - -The class is usually divided into two orders, one characterised by the -possession of two gills, and the other of four; but the British species -belong to the former, known technically as the _Dibranchiata_. This -order is subdivided into two sections according to the number of arms; -and the divisions are called the _Octopoda_ and _Decapoda_ respectively. - - [Illustration: FIG. 183.--OCTOPUS] - -The former section includes the Octopods, of which some species inhabit -our seas. They all have eight arms, of unequal size, with the suckers -arranged in two rows, and their round or oval bodies seldom have any -fins, locomotion being effected by means of the arms, and by the sudden -expulsion of water from the siphon. The shell is rudimentary, being -represented merely by two short 'styles' within the mantle. The species -vary considerably in size, some being only about an inch long when fully -grown, while others measure two feet or more, and are looked upon as -formidable creatures by man. Sometimes they are washed up on our -beaches, but the best way to make their acquaintance is to examine the -contents of the fishermen's drag nets as they are hauled on the beach. - -In the same manner we may secure various species of the Decapods or -Ten-footed Cephalopods, which comprise the Calamaries, Squids, and -Cuttlefishes. These, too, properly speaking, have but eight arms, the -other two appendages being really tentacles, which are usually longer -than the arms, and more or less retractile; they are also expanded at -the ends. The decapods are also to be distinguished from the octopods -by their elongated bodies, and a flattened, fin-like appendage on either -side. Their eyes, also, are capable of being rotated within the orbits, -while those of the octopods are fixed; and the shell consists of one or -more horny 'pens,' or of a calcareous 'bone,' contained in a cavity so -loosely that it drops out of its place when the cavity is opened. - - [Illustration: FIG. 184.--_Loligo vulgaris_ AND ITS PEN] - - [Illustration: FIG. 185.--_Sepiola atlantica_] - -The Common Calamary (_Loligo vulgaris_) may be recognised by the -accompanying illustration, from which it will be observed that the body -tapers behind, bearing two rhomboidal fins in the rear. The suckers are -arranged in two rows on the arms, but in fours on the expanded tips of -the tentacles. The animal is a good swimmer, and sometimes crawls, head -downwards, on the disc surrounding the mouth, pulling itself along by -means of its arms. Its shell is a horny pen, lanceolate in form, but it -divides as the age of the animal advances, so that two or more may be -found in the same specimen. - -Belonging to the same family we have the Common Squid (_Sepiola -atlantica_), also a very abundant species. Here the body is shorter and -purse-like, and the fins are dorsal and rounded. It seldom exceeds four -or five inches in length, and, like the Calamary, is used largely as a -bait by fishermen. - -Another family--the _Sepiadae_--contains the Cuttlefish (_Sepia -officinalis_), the 'bone' of which is such a common object on the beach. -This latter is a broad, curved plate of carbonate of lime, made up of a -number of regular layers, and having a cavity hollowed out at the -posterior end. It is exceedingly light and porous in structure, and at -one time was used largely as an antacid as well as a dentifrice. It is -also proportionately large, being both as long and as broad as the body -of the animal. - - [Illustration: FIG. 186.--_Sepia officinalis_ AND ITS 'BONE'] - -Cuttlefishes live principally in the shallow water close to shore, where -they swim backwards by the sudden propulsion of water from their -siphons; and their eggs, which look like clusters of black grapes, are -frequently thrown up on the beach, generally attached to the stems and -fronds of sea weeds. - -As a rule the cephalopods swim slowly by the aid of their fins or by a -rhythmic contraction by which water is expelled from their siphons, but -when in danger the muscular contraction is so violent that they dart -through the water with great speed, and even leap into the air to avoid -their enemies. But they have another and much more remarkable way of -escaping from their foes:--They possess a gland, the duct of which opens -into the base of the funnel or siphon, that prepares an inky fluid; and -when the animal is disturbed it suddenly ejects this fluid, rendering -the surrounding water so cloudy that it is often enabled to retreat -unobserved. The 'ink' of the _Sepia_ was used for writing in former -times, and is still employed in the preparation of the artist's pigment -that bears the same name. Fishermen are well acquainted with this -peculiar characteristic of the animal, for they are frequently -bespattered with the contents of the ink bag of the _Sepia_ when the -creature is included in the contents of their draw-nets, and have learnt -to handle it cautiously until the objectionable fluid has been all -discharged. - - [Illustration: FIG. 187.--EGGS OF _Sepia_] - -We will conclude this chapter by giving a tabular summary of the -classification of the molluscs which will probably be useful to the -collector of marine objects. - - - CLASSIFICATION OF THE MOLLUSCA - - Class =LAMELLIBRANCHIATA=--Plate-gilled. Headless, usually enclosed - in bivalve shell. - Section =SIPHONIDA=--Mantle lobes more or less united to form - tubular siphons. - Families--_Pholadidae_, _Gastrochaenidae_, _Anatinidae_, - _Myacidae_, _Solenidae_, _Tellinidae_, _Mactridae_, - _Veneridae_, _Cyprinidae_, _Lucinidae_, _Cardiadae_, &c. - Section =ASIPHONIDA=--Mantle lobes free or nearly so. No true - siphons. - Families--_Arcadae_, _Mytilidae_, _Aviculidae_, _Ostreidae_, - &c. - - Class =CEPHALOPHORA=--Head-bearing. Usually enclosed in a univalve - shell. - Section =PTEROPODA=--Wing-footed molluscs. - Section =GASTEROPODA=--Stomach-footed molluscs. - Order =Nucleobranchiata=--Viscera form a nucleus on the back. - Order =Opisthobranchiata=--Shell generally absent. Gills more - or less exposed. - Section NUDIBRANCHIATA--Naked gills. - Section TECTIBRANCHIATA--Gills covered by shell or mantle. - Order =Pulmonifera=--Lung-breathers. Terrestrial. - Order =Prosobranchiata=. - Section HOLOSTOMATA--Aperture of shell entire (sea snails). - Families--_Chitonidae_, _Dentaliadae_, _Patellidae_, - _Calyptraeidae_, _Fissurellidae_, _Haliotidae_, - _Turbinidae_, _Littorinidae_, _Turritellidae_, - _Cerithiadae_, _Pyramidellidae_, _Naticidae_, &c. - Section SIPHONOSTOMATA--Possess a true siphon. Carnivorous. - Families--_Cypraeidae_, _Conidae_, _Buccinidae_, _Muricidae_, - &c. - - Class =CEPHALOPODA=--Sucker-bearing arms round the mouth. - Order =Dibranchiata=--Two gills. - Section OCTOPODA--Eight arms. - Families--_Argonautidae_, _Octopodidae_. - Section DECAPODA. - Families--_Teuthidae_ (Calamaries, Squids), _Sepiadae_, &c. - Order =Tetrabranchiata=--Four gills (containing _Nautilidae_). - - - - - CHAPTER XIII - - _MARINE ARTHROPODS_ - - -The sub-kingdom _Arthropoda_ contains a vast assemblage of animals, all -of which, as the name implies, possess jointed appendages. Their bodies -are covered with a skin that is hardened by a horny substance -(_chitin_), and frequently, also, by the deposit of carbonate of lime. - -The body of Arthropods is made up of a chain of segments, all of which -are built up on one common pattern, and each one is surrounded by a ring -of the hardened skin or exo-skeleton that gives attachment to a pair of -appendages. Commonly, however, two or more of the segments become fused -together, being covered by a continuous plate or shield, in which the -boundaries of the rings are almost or completely obliterated; but in -such cases the appendages they bear always remain distinct, so that the -true number of segments is always apparent. The skin between those -segments that are not so fused together remains soft and flexible, thus -allowing the body to be freely bent. - -The appendages exhibit a great variety of structure, and are as varied -in their functions. Some are used as feelers, and others as jaws for -seizing or masticating food. Some are developed into powerful seizing -organs for purposes of defence or attack, some into paddles for -swimming, while others are legs adapted for walking. - -All these appendages are made up of segments, each of which, like those -of the body itself, is surrounded by a ring of hardened skin, and -connected with its neighbours by a flexible integument that allows -perfect freedom of movement; while within are the muscles, often very -powerful, by which the appendage is moved. - -In the arthropods we have a sub-kingdom of highly organised animals, -with distinct, and often very complicated, systems of organs for -digestion, circulation, and respiration; and the nervous system consists -of a well-developed chain of ganglia, connected by nerve cords, and from -which nerve fibres are distributed to the various parts of the body. It -should be noted, however, that some members of the group have -degenerated into parasites, and in these, as with all such degraded -creatures, many of the organs have retrogressed to such an extent that -they are quite functionless, or have even disappeared entirely. These -parasitic forms, when very young, are really highly organised creatures, -not unlike the young of their industrious and more noble relatives; but, -as the natural result of their degraded mode of living, in which they -find no use for their organs of locomotion, digestion, circulation and -respiration, these eventually disappear, with the result that the organs -of reproduction predominate to such an extent that they often fill the -greater part of the cavity of the body. - -It should be noted, too, that the sense organs of arthropods are well -developed, most of them being supplied with complex eyes, hearing -organs, and highly sensitive feelers. - -This sub-kingdom consists of four classes--the _Crustacea_, including -lobsters, crabs, shrimps, prawns, &c.; _Arachnoidea_, containing -spiders, mites, and scorpions; _Myriopoda_--centipedes and millepedes; -and _Insecta_. - - [Illustration: FIG. 188.--THE NERVE-CHAIN OF AN ARTHROPOD (LOBSTER) - _o_, optic nerve; _c_, cerebral ganglion; _i_, large ganglion - behind the oesophagus; _th_, ganglia of the thorax; _ab_, ganglia - of the abdomen] - -The first of these classes consists mainly of marine animals, and will -therefore occupy much of our attention, but the members of the other -three are mostly terrestrial and aerial creatures that do not fall -within the scope of this work, except in the case of a few species that -are more or less decidedly marine in their tendencies. The aquatic -members are generally provided with well-formed gills by means of which -they are enabled to extract the dissolved oxygen from the water in which -they live, while those of terrestrial and aerial habits breathe by means -of a system of tracheae or air-tubes that are open to the air and supply -branches to all parts of the body. - -The _Crustaceans_ are mostly gill-breathers, though some of the aquatic -species have no special organs for respiration, but obtain the oxygen -necessary for respiration by absorption through their thin, soft skin, -while the terrestrial species breathe by means of tracheae, as we have -just observed. - -Most of them are covered with a calcified skin, as in the case of crabs -and lobsters; but many are protected with a chitinous or horny covering -such as we observe in shrimps and prawns. In either instance the -hardened integument constitutes what is known as the _exo-skeleton_. -None of the crustaceans have an internal skeleton of any kind, though -some of the inner parts are supported by extensions of the hard skin -that penetrate into the body. - -It will be readily understood from the nature of the exo-skeleton of the -crustacean, and especially of the more or less rigid calcareous covering -of the crab and the lobster, that a uniform growth of the body is -absolutely impossible, and, in fact, that an increase in size cannot -take place without an occasional casting of the hard coat of mail. Hence -we find most crustaceans throwing off their coverings at intervals, and -growing by fits and starts during the periods between the 'moultings' -and the hardening of the newly exposed skin. - -When a crab or a lobster is about to undergo the process of moulting, it -retires to a secluded niche in the rock, where it is not so easily found -by its numerous enemies--a necessary precaution, since the creature in -its soft or unarmoured condition is eagerly devoured by fishes and other -marine animals--and there awaits the first stage of the ordeal. -Presently the skin splits; and, after a time, the crustacean succeeds in -extricating itself from its shell, which is cast off in a perfect -condition, every joint being entire, even to the coverings of the -antennae, the stalked eyes, and other delicate appendages. And not only -this, for the portions of the shell that penetrate inward into the body -are also discarded, as well as the linings of the stomach and the gills; -and these cast-off coats of crabs and lobsters--especially the -former--may often be found in the most perfect condition on the sea -shore, being washed up without injury on the sandy beach, or found in -the very niche in which the creature changed its attire. - -If one examines the powerful pincers of a crab or lobster, a thin plate -of considerable size will be seen to extend within from the movable -'jaw' to give attachment to the muscles by which it is moved, and it -seems impossible that this can be removed with the cast skin without -considerable injury to the new claw that is already formed, though as -yet in a soft condition, within the old and hard one. But it has been -observed that this plate actually cuts through the new claw, and that -the claw thus divided almost immediately closes up and unites again. - -The moulting process being over, the crustacean's body extends itself -within the new, yielding skin; and, the latter becoming gradually hard -by the deposition of carbonate of lime, the creature is able, after a -period of rest, to roam at large again, without much fear of injury, -until the time for the next moulting has arrived. - -Those who have made but a slight acquaintance with the common -crustaceans of our shores must have noted the frequency with which -imperfect specimens occur--specimens with missing appendages, or with a -well-formed limb on one side of the body opposed to a puny and almost -useless fellow on the opposite side. As to the loss of appendages, this -matter will be readily understood by those who have watched crustaceans, -and especially crabs and lobsters, in their native element, so often do -these pugnacious creatures become engaged in furious broils with their -neighbours. And, when we are at work at the collection of various -species on the sea shore, how often do we find that a creature escapes -from our grip by leaving us in possession of a severed limb, while the -owner retreats rapidly among the stones and weeds apparently none the -worse for its trifling loss! This is, in fact, a very common method of -securing its escape from an enemy; and it appears that many crustaceans -have the power of thus rendering a seized limb so brittle that it may be -snapped off with the greatest of ease. - -We have spoken of the loss thus sustained as a trifling one; and so it -is, for crustaceans have the faculty of reproducing lost appendages; and -though the loss may be one of considerable inconvenience at first, a new -limb eventually appears in the place of each one so willingly discarded. - -When such mutilations occur, it will be observed that the severed limb -invariably breaks away at the end of the first or basal joint--a point -where the bloodvessels are so narrow and contractile that but little -loss of blood takes place when the rupture is made--and it has been said -that the animal would soon bleed to death if the fracture were to take -place at any other point. As it is, the wound soon heals, but no trace -of a new limb is to be seen, at least without dissection, until the time -of the next moult. The part is developing, however, beneath the cover of -the basal joint; and when the moulting period arrives, the new limb, -still very small, is exposed to view. It then rapidly enlarges, though -not to anything like its proper size, and its surrounding skin becomes -hardened by the deposit of the calcareous secretion simultaneously with -that of the rest of the body. Further enlargements of the new appendage -take place at subsequent moults, with the final result that it is but -slightly inferior to its fellow either in size or in power. - -The eye of a crustacean is a very complicated structure, commonly -described as a compound eye. It consists of a large number of conical, -radiating, crystalline rods, collected together into a mass that -presents a convex outer surface. This surface is covered with a -transparent layer of chitin which naturally presents a more or less -distinct netted appearance, the bases of the rods being in contact with -its inner surface, and visible through it. Each rod is surrounded by a -layer of pigment that prevents light from passing from one to another, -and the optic nerve passing into the base of the compound structure -sends a sensitive filament into each one. - - [Illustration: FIG. 189.--SECTION THROUGH THE COMPOUND EYE OF AN - ARTHROPOD] - -In many crustaceans this compound eye is situated on the end of a -movable stalk that generally allows it to be protruded or drawn under -cover as occasion requires, but in others the organ does not project -beyond the general surface of the body. Thus we hear of the animals of -this class being divided into the _stalk-eyed_ and the _sessile-eyed_ -groups; the former being represented by crabs, lobsters, shrimps, &c.; -and the latter by sandhoppers and sandborers. - -Crustaceans undergo metamorphoses while very young, the body being -altered considerably in form at several successive moults. Some, in -their earliest stage, consist of a little oval body that shows no signs -of a division into segments. It swims about by means of three pairs of -appendages, and has only one eye. Others start life with four pairs of -limbs, attached to the front portion of the body, a segmented abdomen, -as yet perfectly limbless, and a pair of compound eyes. Then as the -successive moultings take place, new segments and new appendages are -developed, until, at last, the form of the adult is assumed. The -accompanying illustration shows four stages in the development of the -Common Shore Crab. - - [Illustration: FIG. 190.--FOUR STAGES IN THE DEVELOPMENT OF THE COMMON - SHORE CRAB] - -The lowest division of the crustaceans contains the _Cirripedia_ or -Curl-footed crustaceans, which includes the Barnacles that are so -frequently seen attached to the bottom of ships and of floating timber, -and the Acorn Barnacles, the conical shells of which often completely -cover large masses of rock on our shores. - - [Illustration: FIG. 191. THE BARNACLE] - -For some time naturalists could not agree as to the proper place of -these animals in the scale of life, but the matter was finally settled -when some minute creatures only about a twelfth of an inch in length, -and closely resembling the early stages of certain crustaceans, were -seen to undergo metamorphoses, and finally develop into acorn barnacles. -Their position in the animal kingdom was thus determined by their early -stages; but these, instead of changing into a segmented and highly -organised creature like the typical crustacean, lose some of their -appendages, cease to be free-moving animals, and attach themselves to -floating bodies by which they are carried about. Thus they are enabled -to find the food they can no longer seek without such aid. In their -young state they possess not only the means of freely moving in search -of their food, but have organs of vision to aid them in the capture of -their prey. As they grow, however, the foremost appendages are -transformed into a sucking-disc, and the eyes, no longer necessary, -disappear. It will thus be seen that the degenerated adult--the product -of a _retrograde development_--is attached by what was originally the -front of its body, while the abdomen is undeveloped, and the thorax, -with its appendages, forms the summit of the free extremity. - - [Illustration: FIG. 192.--FOUR STAGES IN THE DEVELOPMENT OF THE ACORN - BARNACLE - A, newly hatched larva; B, larva after second moult; C, side view - of same; D, stage immediately preceding loss of activity; - _a_, stomach; _b_, base of future attachment. All magnified] - -Some of the Cirripedes attach themselves to the bodies of whales and -other marine animals. The majority of these are -pseudo-parasites--creatures that live on the bodies of other animals, -but do not derive their food at the expense of their hosts; others, -however, are true parasites, subsisting on the nourishing juices they -extract from the animals to which they are attached. - - [Illustration: FIG. 193.--A CLUSTER OF ACORN SHELLS] - -The Acorn Barnacles, so numerous on our shores, are good types of the -_Cirripedia_, and they are so easily kept alive in the indoor aquarium -that their interesting movements may be well observed. A cluster of -these animals may be obtained by chipping off a piece of the rock on -which they grow; or, instead of this, a few minutes' searching on a -rocky coast at low tide will certainly provide us with a stone of -suitable size, or the shell of a mollusc, on which the creatures have -found a home. - - [Illustration: FIG. 194.--SHELL OF ACORN BARNACLE (_Balanus_)] - -Place them in the indoor aquarium, or in any shallow vessel containing -just sufficient sea-water to cover them, and carry out your -observations with the aid of a hand lens. They will soon open the inner -cone of their many-valved shell, and slowly protrude six pairs of -gracefully curved and delicately-feathered appendages which, as -previously stated, are attached to the thoracic portion of the body. -Then, with a much more rapid movement, the appendages will be withdrawn, -and the shell closed. These alternate movements are continued -incessantly, and are the means by which the animals provide themselves -with both food and air. The reader should also obtain some specimens of -the larger species for the examination of the shell, the structure of -which is interesting and, of course, peculiar to this order. - - [Illustration: FIG. 195.--THE ACORN BARNACLE (_Balanus porcatus_) WITH - APPENDAGES PROTRUDED] - -In general structure and habits Barnacles are very similar to the acorn -barnacles, except that the body is supported on a tough stalk, which, as -we have already stated, is the modified anterior portion of the animal. -These animals also may be easily kept alive and examined in the indoor -aquarium. They are not creatures of the sea shore, but may often be -obtained on masses of timber that have been washed ashore, or from the -bottoms of ships that have been placed in the dry dock for repairs. - -Another order of the crustaceans--the _Copepoda_, or oar-footed -group--is so called on account of the bristled feet that are employed -after the manner of oars when the creatures are swimming. - -These Copepods are small animals, so small indeed that the compound -microscope is generally necessary merely for the examination of their -external characters. Many species inhabit fresh water, and the study of -the group is more commonly pursued by the investigator of fresh-water -pond life than by the sea-side naturalist. However, marine species are -abundant, and may be captured in the open water or in rock pools by -means of a muslin net. As with the last order, some degenerate from the -comparatively complicated free-swimming and eyed larval state to blind -and limbless parasites that feed on the bodies of fishes and are known -as fish lice. - -The body of the typical copepod is distinctly segmented, and the head -and thorax are both enclosed in a hardened buckler. It has two pairs of -antennae, two pairs of foot jaws by which it captures its prey, and four -or five pairs of bristled feet for swimming. The jointed abdomen has -also a tuft of bristles at its extremity. The annexed illustration -represents some marine species, and will serve to show the general -features of the order. - - [Illustration: FIG. 196.--A GROUP OF MARINE COPEPODS, MAGNIFIED] - -The sea-side naturalist, intent on the collection of small life, may -possibly meet with representatives of two other orders of -crustaceans--the _Ostracoda_ or shelled crustaceans, the bodies of which -are enclosed in a bivalve, hinged shell; and the _Branchiopoda_, so -called because the branchiae or gills are attached to the feet. - - [Illustration: FIG. 197.--A GROUP OF OSTRACODE SHELLS] - -The Ostracodes have two or three pairs of feet which subserve -locomotion, but are not adapted for swimming; and two pairs of antennae, -one of which assists in locomotion. The mouth is provided with organs of -mastication, the branchiae are attached to the hind jaws, and the -animals have but one eye. Some of these crustaceans inhabit deep water -only, while others live in sand between the tide-marks; but several -species, belonging chiefly to the genus _Cythere_, abound in rock pools, -where they may be readily obtained by scraping the confervae and -corallines with a small muslin net. - -The branchiopods are free swimmers, and are protected by a buckler-like -envelope. Most of them are inhabitants of fresh water, and are popularly -known as water fleas. We have figured one marine species, belonging to -the genus _Evadne_, which has a colourless body, and a single -conspicuous black eye, and is interesting as being the food of the -herring. - - [Illustration: FIG. 198.--_Evadne_] - -The four orders of crustaceans that have been briefly described belong -to the division _Entomostraca_, which signifies 'shelled insects.' This -term is not a happy one when judged from the standpoint of our present -knowledge of animal life, but it must be remembered that, at the time it -was applied (1785), spiders and crustaceans were all included in the -same class as the insects; and this is hardly surprising when we observe -the close relationship of these animals, as shown in their segmented -bodies and jointed appendages; for, as we have already shown, the lowly -organised parasitic crustaceans which, in the adult state, lose most of -their appendages and cease to be distinctly segmented, are more or less -insect-like in their larval and free-swimming stage. - -All the other crustaceans are included under the term _Malacostraca_, or -soft shelled, since, although many of them are protected by an -exo-skeleton that is hardened by the deposit of carbonate of lime, yet, -generally speaking, their coverings are softer than those of the -molluscs; and therefore the term _Malacostraca_ was originally applied -by Aristotle in order to distinguish them from the animals that are -covered by harder and thicker shells. - -This division of the crustaceans contains wood lice, sandhoppers, -lobsters, shrimps, crabs, &c., and consists of two main groups--the -Sessile-eyed (_Edriophthalmata_) and the Stalk-eyed (_Podophthalmata_) -crustaceans. - -We shall now consider the Sessile-eyed group, dealing first with the -order _Isopoda_ or equal legged, and then the _Amphipoda_, which have -appendages adapted both for walking and swimming. - -The general nature of an Isopod may be readily understood by the -examination of the common woodlouse that abounds in gardens and damp -places almost everywhere, and the reader will probably remember having -seen similar creatures crawling over the rocks on the sea shore. - -The body is generally depressed or flattened, but convex above, and is -composed of seven segments, each segment bearing a pair of legs which -terminate in a pointed claw, while the posterior appendages are modified -into flat, leaf-like organs of respiration. - - [Illustration: FIG. 199.--MARINE ISOPOD - 1. _Sphaeroma serratum._ 2. _Limnoria lignorum._ 3. _Ligia - oceanica._ 4. _Nesaea bidentata._ 5. _Oniscoda maculosa_] - -When engaged in 'shrimping' one frequently meets with shrimps or prawns -that are disfigured by a tumourous swelling on the side of the body, and -if the swelling be opened a little parasite will be dislodged. This -parasite is an Isopod (_Bopyrus_), the appendages of which are -imperfectly developed. The female is very much larger than the male, -and, as is usual with parasitic creatures, the greater part of the -body-cavity is occupied by the well-developed organs of reproduction. - -There are several other parasitic isopods, some of which live on the -bodies of fishes, and are popularly known as fish-lice, but these are -not so likely to come in the way of the sea-side naturalist as the more -typical forms that crawl about on the rocks and among the weeds of the -coast. A few of the latter are shown in the accompanying illustration, -including the Sea Pill-ball (_Nesaea bidentata_), common on the rocky -coasts of the south-west, and distinguished by the two sharp -projections on the last segment; the Serrated Pill-ball (_Sphaeroma -serratum_), very common on most rocky shores, and characterised by the -fine sawlike teeth on the outer edge of the outer plates of the 'tail'; -the Great Sea-slater (_Ligia oceanica_), also an abundant species; the -Spotted Hog Louse (_Oniscoda maculosa_) that lives among the tufted sea -weeds; and the Boring Pill-ball (_Limnoria lignorum_) that bores into -the woodwork of piers and jetties, often doing considerable damage. - - [Illustration: FIG. 200.--MARINE AMPHIPODS - 1. The spined sea screw (_Dexamine spinosa_). 2. _Westwoodia - coecula._ 3. _Tetromatus typicus._ 4. The sandhopper (_Orchestia - littorea_). 5. _Montagua monoculoides._ 6. _Iphimedia obesa._ All - enlarged] - -The above and other isopods feed on various animal and vegetable -substances, some species being quite omnivorous in habit. Most of them -are eagerly devoured by birds and fishes. - -The Amphipods, six species of which are shown in the above illustration, -include the Sandhoppers or Beach Fleas, so numerous on our coasts that -it is almost impossible to go any distance without making their -acquaintance. They are invaluable as scavengers, as they rapidly devour -decaying sea weeds, and will speedily reduce the body of any animal -washed on the beach to a clean skeleton. Although they are all small -creatures, they make up in numbers for any deficiency in size; and -though devoured in enormous quantities by the various shore birds, they -multiply so prodigiously that they are never lacking wherever there is -decomposing organic matter to be consumed. - -The bodies of these animals are usually flattened from side to side, -very distinctly segmented, and have a well-developed abdomen. The head -is furnished with two pairs of antennae and a pair of sessile eyes, -though some species possess only one pair of antennae, while others have -four eyes. The limbs of the thorax are used either for walking or for -swimming, and give attachment to the gills. The abdomen has generally -six pairs of appendages, the foremost three pairs of which are usually -small, and employed in swimming, while the others are stronger and -directed backwards, and are often adapted for jumping. - -It is very interesting to observe the habits of the Sandhoppers and -other Amphipods both on the sandy beach and in the water, and the -student will find that certain species burrow into the sand with -considerable agility, and live principally at the extreme high-water -mark, where they feed on the organic matter washed in by the breakers at -each high tide, while others dwell almost exclusively in the water, -among weeds and stones, and should be searched for at low water. The -latter may be kept alive for some time in the aquarium providing they -are the only occupants, but a little experience will show that these and -all other Amphipods are readily devoured by many marine creatures, and -consequently they are of real value to the aquarium keeper as food for -other animals. - -We now come to the Stalk-eyed Crustaceans (_Podophthalmata_), which -contain those members of the class most generally known, such as crabs, -lobsters, shrimps, and prawns. In these the eyes are mounted on movable -pedicels, the head and thorax are generally covered by a large shield -called the carapace, and the appendages are adapted partly for seizing -and masticating, and partly for locomotion. - -The group includes two orders--the _Stomapoda_ or Mouth-footed -crustaceans, so called because some of the limbs are crowded round the -region of the mouth; and the _Decapoda_, or Ten-footed crustaceans. - -The Stomapods, though very abundant in tropical seas, are not often met -with on our own shores. However, since a few interesting species are -inhabitants of our seas we will briefly describe the distinguishing -characteristics of the group. - -We have just mentioned the fact that the head and thorax of a decapod is -usually covered by a large shield--the carapace. Now, the general -character of this carapace may be seen at once in either the shrimp or -the lobster. In these animals the segments that form the head and the -thorax are all fused together, and are completely covered by the -protective buckler of hardened skin; but in the Stomapoda the carapace -is much smaller in proportion, and a few of the segments of the thorax, -instead of being fused into the general mass of the _cephalo-thorax_, -are quite distinct from it. The abdomen, also, is large and strongly -formed in these animals. Five pairs of the thoracic limbs are directed -forwards, and are adapted both for catching food and for climbing, while -others are used in walking. The limbs of the abdomen generally number -six pairs, of which the first five bear feathery gills. - - [Illustration: FIG. 201.--THE MANTIS SHRIMP (_Squilla Mantis_)] - -Two species of Mantis Shrimps, one of which is represented in fig. 201, -have been found off the south and south-west coasts, but these are not -likely to be seen on the shore, since they inhabit deep water. Allied to -these, and sometimes included with the Stomapods, are the Opossum -shrimps, so called because the females of some species carry their eggs -in a kind of pouch, thus reminding us of the marsupial quadrupeds of the -same name. They are of very slender build compared with the mantis -shrimps, and differ from them in that the carapace completely covers the -thorax; but though this is the case, the fusion of the thoracic segments -is not complete, since the posterior ones have still a certain amount of -freedom of movement. Some species of opossum shrimps are abundant in the -rock pools of our coasts, particularly in the south-west, but their -bodies being often so transparent as to be almost invisible, they are -consequently easily overlooked. Their general appearance may be -gathered from our illustration of _Mysis chamaeleon_, which is probably -the most common species inhabiting our coast. - -The highest crustaceans--the Decapods--are divided into two -sub-orders--the _Macrura_, or Great-tailed, including lobsters, shrimps, -&c.; and the _Brachyura_ (Short-tailed), containing the crabs; but the -number of British species is so large that it is impossible to give, in -our limited space, a detailed description of all the commonest even. All -we can do is to note a few of the more interesting features of certain -species, to introduce such illustrations as will enable the young -naturalist to identify a number of the commoner ones, and to give the -general characteristics of the main divisions so that the student may be -able to classify his specimens intelligently. - - [Illustration: FIG. 202.--THE OPOSSUM SHRIMP (_Mysis chamaeleon_)] - -In the _Macrura_, as with other divisions of the crustaceans, we meet -with very interesting modifications of the appendages, adapted to quite -a variety of uses; and if the reader is unacquainted with these -adaptations of structure to habit he cannot do better than secure a -lobster or crayfish for study. It will be observed that the body may be -divided into two main portions--the _cephalothorax_, consisting of head -and thorax combined, and the _abdomen_. The former is composed of -fourteen segments, so thoroughly fused together that they are denoted -only by the fourteen pairs of appendages to which they give attachment, -while the calcified skin forms one continuous shield surrounding the -whole. The abdomen, on the other hand, consists of six distinct -segments, each of which is surrounded by its own ring of the hardened -integument, and is connected with its neighbours by means of a portion -of uncalcified skin that renders the whole very flexible. A groove in -the front portion of the great shield (_carapace_) marks the division -between the head and the thorax, the former composed of six, and the -latter of eight united segments. - - [Illustration: FIG. 203.--PARTS OF LOBSTER'S SHELL, SEPARATED, AND - VIEWED FROM ABOVE] - -The calcareous covering of each segment consists of an upper portion, -called the _tergum_, and a lower, named the _sternum_, united at the -sides; the sternal portion of the cephalothorax, which gives attachment -to the walking limbs, is a most complicated and beautifully formed -structure. - - [Illustration: FIG. 204.--A SEGMENT OF THE ABDOMEN OF A LOBSTER - _t_, tergum; _s_, sternum, bearing a pair of swimmerets; _h_, - bloodvessel; _d_, digestive tube; _n_, nerve chain] - -The six pairs of appendages belonging to the head are easily made out -with a little care. The first are the jointed _eye-stalks_ that bear the -compound eyes previously described; and these are followed by two pairs -of _antennae_, or feelers, the first being shorter and double, while the -second are very long. The former contain the organs of hearing. Then, in -front of the mouth, and completely hiding it, are a pair of strong -_mandibles_ or jaws that move horizontally, and the two pairs of -_maxillae_ that are also employed in reducing the food. - -Following these, but belonging to the thorax, are three pairs of -appendages that are known as foot-jaws; for, although they assist the -preceding organs in breaking up the food, they bear a resemblance in -some respects to the longer limbs behind them. Of the latter there are -five pairs (hence the term _decapoda_), the first being a very powerful -pair of seizers or pincers, and the remaining four, which are well -adapted for walking, terminating in either double or single claws. - -All the appendages above mentioned are not only attached to the body by -movable joints, but are themselves made up of jointed parts, sometimes a -considerable number, each of which, like the segments of the body -itself, is surrounded by a ring of hardened skin, and connected with -those above and below it by a portion of soft and flexible skin. - - [Illustration: FIG. 205.--APPENDAGES OF A LOBSTER - 1. Second maxilla. 2. Third foot-jaw. 3. Third walking leg. - 4. Fifth walking leg] - -Lastly, beneath the abdomen, are paired limbs called _swimmerets_, which -are used as paddles, and probably assist the animal more or less in its -progress through the water; but the principal organ of locomotion in the -_macrura_ is undoubtedly the powerful muscular abdomen, aided by the -broad and fanlike tail formed by the appendages of the last segment. To -demonstrate this fact, put a live lobster, or even a shrimp, in a still -rock pool, and threaten it from before, when it will rapidly retreat -backwards by a series of powerful jerks, produced by suddenly doubling -its abdomen forwards beneath its body. - -In addition to the external characters above mentioned, there are many -interesting features connected with the internal structure of the -lobster that may be studied on making easy dissections. Thus, the gills, -which are attached to the bases of the thoracic limbs, may be exposed by -cutting away the side of the carapace, and at the same time we may -discover the bailing organ by means of which a current of water is kept -flowing forwards through the gill-cavity to keep up the necessary supply -of oxygen for respiration. The removal of the upper portion of the -carapace will expose the heart and some of the principal bloodvessels, -and also the stomach with its powerful and complicated 'gastric mill,' -formed by the hardening of portions of the wall of the latter organ for -the purpose of crushing and masticating the food. Then, if these organs -be carefully removed from above, together with the others we have not -space to describe, and the powerful muscles that fill up the segments of -the abdomen, the chain of ganglia and their connecting nerve cords that -form the central part of the nervous system may be seen extending along -the central portion of the body. - - [Illustration: FIG. 206.--LONGITUDINAL SECTION OF THE LOBSTER - _a_, antenna; _r_, rostrum or beak; _o_, eye; _m_, mouth; _s_, - stomach; _in_, intestine; _l_, liver; _gl_, gills; _h_, heart; - _g_, genital organ; _ar_, artery; _n_, nerve ganglia] - -Several species of lobsters inhabit our seas, but they are generally to -be found beyond the tide-marks, and are, therefore, not often caught by -sea-side collectors without the aid of some kind of trap or the -assistance of fishermen. The common lobster (_Homarus vulgaris_), -however, is often left behind by the receding tide on our rocky coasts, -and may be seen and caught if one knows where to look and how to -capture. - -On cautiously approaching a deep rock pool one may often see a lobster -rapidly retreat in its usual backward fashion, and snugly house itself -in a narrow chink from which it is impossible to remove it. And, when -once surprised, it is not likely to show itself again as long as the -intruder is in view. - -If one remains perfectly still for a time, a pair of waving antennae may -be seen gradually protruding from the safe retreat; but, as soon as the -stalked eyes have advanced sufficiently to detect the figure of a -stranger, the lobster silently withdraws itself till quite out of sight. - -Lobsters, usually of rather small size, may often be seen quite out of -the water at low tide, in the narrow chinks of the rock, or under large -stones, but it is no easy matter, as a rule, to get them out. It is of -little use poking a stick into the entrance of their hiding-places, -though occasionally they will grasp the stick so tenaciously with their -forceps that they may be pulled within reach. You _may_ be able to haul -them out by their long antennae, but if you can find a second way into -their home such that you can disturb them from behind you are pretty -sure of your victim. - - [Illustration: FIG. 207.--THE SPINY LOBSTER (_Palinurus vulgaris_)] - -It will be unnecessary to describe other species of lobsters -individually, but we have introduced figures of a few for -identification. The Norway Lobster (_Nephrops norvegicus_) is often -landed in large numbers by the fishermen of the east and south-east -coasts and sold at a shilling or so a dozen under the name of Norway -Prawns. They are pretty and interesting creatures, and may be easily -kept alive in the indoor aquarium, where they may be fed on any kind of -fish. - - [Illustration: FIG. 208.--THE NORWAY LOBSTER (_Nephrops norvegicus_)] - -Fig. 209 represents the two allied creatures that may sometimes be dug -out of the sandy beach, or from the mud in the estuary of a river. The -one on the left is the mud-borer (_Gebia stellata_), which is of a dull -yellowish colour, marked more or less distinctly by pinkish starlike -spots--a feature that has suggested the specific name. The beak in front -of the carapace is very prominent and spiny, and the long abdomen is -narrower in front than in the middle. This creature hides in the holes -that have been excavated by boring molluscs, and seems also to extend -the cavities it inhabits by its own labours. - -The other is very similar in general form, but has no spiny beak and the -abdomen is much broader in the middle than at the base. It is also to be -distinguished by the very unequal size of its front legs, one of which -is much more developed than the other. - -It is known as the mud-burrower (_Callianassa subterranea_), and is said -to burrow very deeply into mud-banks, scooping out its retreat -principally by means of the second and third pairs of legs. Although -found at times between the tide-marks, its principal habitat is probably -in the mud that is covered by deep water, for it is not uncommonly to be -found in the stomachs of fishes that habitually feed in such localities. - - [Illustration: FIG. 209.--THE MUD-BORER (_Gebia stellata_) (1) AND THE - MUD-BURROWER (_Callianassa subterranea_) (2)] - -Lobsters of all kinds, and, indeed, the marine crustaceans generally, -are essentially the scavengers of the sea, for they are carrion-feeders, -greedily devouring flesh in all stages of decomposition. Hence the value -of their work on the sea shore is very considerable. - -An examination of shrimps and prawns will at once show their close -relationship with lobsters. The general build of their bodies is -practically the same, and their appendages, though often different in -form from the corresponding limbs of the lobster, will be seen to -resemble them closely in arrangement and structure. The exo-skeletons -of these creatures are, however, generally hardened by a horny substance -(_chitin_) instead of a stony deposit of carbonate of lime. - -The shrimps and prawns sold for food in our markets are very similar in -appearance when alive, the leading distinguishing feature being, -perhaps, the presence of a sharp, serrated beak projecting forward from -the front portion of the carapace of the latter. - -The reader is probably acquainted with the fact that the shrimps and -prawns used as food have quite a different appearance when alive and in -their native element to that displayed by the corresponding wares in the -fishmonger's shop--a fact that applies equally well to the edible crabs -and lobsters. Most crustaceans change to a bright red colour when -boiled, and, as stated in a previous chapter, the same result is -produced by the action of strong spirit. - - [Illustration: FIG. 210.--THE COMMON SHRIMP (_Crangon vulgaris_)] - -The Common Shrimp (_Crangon vulgaris_) is an exception, however, for it -may be distinguished when boiled by its dull greyish brown colour. When -alive this species is of a very pale greenish or greyish tint, lightly -spotted with brown; and its habits are so interesting that it will well -repay one to watch it either in the aquarium or in a rock pool. It -frequents sandy coasts, and can hide itself very quickly by burying its -body in the sand, using for this purpose both its legs and its antennae. - -The Prawn frequents rocky coasts, where it may often be obtained in -large numbers by sweeping with a suitable net under the cover of weeds -and stones. Its body is of an exceedingly pale greenish colour, and so -transparent that it is quite inconspicuous when in the water. Prawns are -turned to a rose-red colour by boiling, and they are captured in large -numbers when young and sold as 'red shrimps.' - - [Illustration: FIG. 211.--THE PRAWN (_Palaemon serratus_)] - -In addition to the common species mentioned there are quite a number of -shrimps and prawns to be found in our seas, but some of them inhabit -deep water and are rarely to be found between the tide-marks. All, -however, are eagerly devoured by fishes, and, on that account, are often -to be obtained in good condition by examining the contents of the -stomachs of freshly caught fishes. In fact, this mode of search for the -smaller species of deep-sea life is not to be despised, for it is a -means by which we can obtain specimens that are not often secured by the -methods coming within the ordinary range of the amateur's work. - -It will be remembered that we spoke of the Decapods as consisting of two -main groups--the Great-tailed (_Macrura_) and the Short-tailed -(_Brachyura_). Frequently, however, we find the order divided into three -sub-orders as follows:-- - - 1. _Macrura_ (Great-tailed), 2. _Anomura_ (Peculiar-tailed), - 3. _Brachyura_ (Short-tailed); - -the first containing lobsters, shrimps, &c.; the third the typical -crabs, such as the shore crab and the edible crab; while in the second -are placed those species of crabs which have been regarded as -intermediate in character. Thus, in the _Anomura_ we find decapods in -which the abdomen, though not so well developed as in the _Macrura_, is -either permanently extended or is capable of being extended and used for -swimming as occasion requires. The hindmost legs, also, are not well -developed and adapted for walking, but are employed only as organs of -prehension; and, as is the case with the first sub-order, there are -often two pairs of well-developed antennae. - -In this sub-order of 'queer tails' we find the Soldier or Hermit Crabs, -and those flat-bodied crabs that live almost exclusively on the surface -of stones, and are hence known as Stone Crabs; but as opinion now seems -inclined against the formation of a special suborder for these -creatures, we shall briefly deal with them as a first section of the -_Brachyura_. - -The Stone Crabs are extremely interesting creatures, and the observation -of their habits, both in and out of the water, is particularly -entertaining and instructive. One species--the Broad-Clawed Porcelain -Crab (_Porcellana platycheles_), shown on Plate VI.--is very abundant on -all our rocky coasts, and may be found in immense numbers near low-water -mark. - -Turn over some of the large encrusted stones that strew the beach among -the rocks, and you are almost sure to find numbers of these little crabs -clinging to the freshly exposed surface. A few of them may remain -perfectly still, and exhibit no sign of surprise on their untimely -exposure to the light; and these, on account of their small size, the -closeness with which they apply their flattened bodies to the encrusted -stone, and more than all to the protective colouring of their dingy -bodies, which so closely resembles that of the surface to which they -cling, may well be overlooked by the inexperienced collector. But the -majority of them will immediately scamper away in their own peculiar -fashion towards the edge of the stone, and rapidly make their way to -what is now the under side. As they progress with a hasty, sliding -movement they never for one moment loosen their firm hold on the rough -surface of the stone, but keep both body and limbs in close contact with -it, clinging hard by means of their pointed claws as well as by the -numerous hairs and bristles with which their appendages are liberally -fringed. - -Attempt to pull one from its hold, or even take other than the gentlest -means to arrest its progress, and you will probably find that it -suddenly parts company with one of its broad claws in its endeavour to -escape; and, unless some special precautions be taken to remove these -crabs, it is possible that quite half the specimens taken will have been -damaged in this way during their struggles to escape. If, however, you -gently thrust the point of a penknife beneath the body, and then apply -the thumb above, you may lift them from a stone without injury. Another -plan is to press a frond of smooth sea weed as closely as possible to -the surface of the stone in the front of the crabs, and then allow them -to crawl on to it, or cause them to do so if necessary. The piece of -weed, with crab or crabs attached, may then be bagged for future -examination. - -On turning over the Broad-clawed Crab its under surface will be seen to -be perfectly smooth, with an appearance closely resembling that of white -porcelain. Its foot-jaws, also, are proportionately large, and closely -fringed with hairs; and the last pair of legs, which are very slender in -build, are folded closely beneath the body. Further, the abdomen is -wide, composed of six distinct movable segments, and terminating in a -tail-fin composed of five fringed plates. - -Drop the crab into water, and it will immediately extend its abdomen, -which it will flap sharply under its body somewhat after the manner of -lobsters and shrimps, and thus swim backward by a series of jerks as it -sinks to the bottom. On reaching the bottom it instantly grasps the -solid material, applies itself closely to the surface, and glides away -into the nearest chink it can find. - -As one observes the nature and movements of these interesting little -crabs one cannot fail to see how beautifully their form and structure -are adapted to their habits. They are peculiarly constructed for abode -in narrow chinks and crannies, and for feeding on the small forms of -life that inhabit such sheltered places. Their legs move in the plane of -their flattened bodies, and as they glide among the confervae and other -low forms of life that encrust the stones of the beach they feel their -way by, and are possibly also guided by the sense of smell located in, -their long outer antennae, while the close fringes of their claws and -foot-jaws form admirable sweep-nets by means of which the little animals -that form their food are swept towards the mouth. - -We have other species of stone crabs, one or two of which resemble the -last species, and belong to the same genus, but the others are very -different in general appearance. The Northern Stone Crab (_Lithodes_), -found principally on and off the coasts of Scotland and Ireland, has a -spiny covering with a long beak. Another species--_Dromia vulgaris_--is -somewhat similar in habit, though it can hardly be termed a stone crab, -since it inhabits deep water, and apparently lives among the sponges, -sea firs, and weeds that cover the bottom. - - [Illustration: FIG. 212.--_Dromia vulgaris_] - - [Illustration: FIG. 213.--THE HERMIT CRAB IN A WHELK SHELL] - -The remainder of the Peculiar-tailed Decapods belong to the Soldier or -Hermit Crabs, and constitute the genus _Pagurus_. - -Every one who has searched a few rock pools will have seen the familiar -Hermits, and will probably have been interested in their varied antics. -First you observe the shell of a mollusc--a Trochus, Periwinkle, or a -Whelk--travelling at an abnormal rate for a member of its class. You -approach closely to make an inquiry into the matter, when the motion -suddenly ceases, and the shell instantly drops into position with its -mouth close to the surface below. If left undisturbed for only a short -time, the rapid and somewhat jerky motion is resumed, only to cease as -suddenly as before as soon as the inhabitant is again threatened. - -On examining the shell we find that it is the home of a species of crab, -and that the animal within it is completely hidden with the exception of -its head, stalked eyes and long, slender antennae, one very large claw, -and a few walking legs. - -To remove the creature from its home is no easy matter as a rule. To -pull it out by means of its legs or its antennae would probably be to -sever some portion of its body; but if you thrust the creature, shell -and all, among the spreading tentacles of a large anemone, it will at -once grasp the peril of the situation; and, if the shell has already -been secured by the clinging petals of this dangerous marine flower, the -hermit will speedily quit its home and endeavour to rush from the many -snares in order to secure its freedom. Or, it not infrequently happens -that the occupied shell is one that has withstood many a storm, but not -without the loss of the apex of its cone. In this case the insertion of -a very flexible fibre into the opening thus made will cause the hermit -to leave its home in the possession of the enemy. - -Having, by some means or other, managed to drive the crab from its -shell, we place it in a shallow rock pool, or in a vessel of sea water, -and observe the chief features of its structure. - -The first thing that strikes one is the absence of a calcified skin on -the extended abdomen, which is so soft that, remembering with what -eagerness fishes will attack and devour crabs of all kinds, we can at -once understand the necessity of such a home as the creature selects. -Again, we observe the presence of appendages at the tip of the abdomen -by means of which the crab is enabled to hold itself securely in the -shell. Also, when we note the general form of the armoured portion of -the body, and the position of the soft-skinned abdomen, we can see how -well adapted the whole is to fit snugly into the spiral shell of a whelk -or winkle. - -We also observe that one of the pincers is much larger than the other, -and the value of such an arrangement may be estimated when we see the -animal at home. The smaller claw, together with the other appendages -used for walking or prehension, can be retracted within the shell, but -the large claw, which constitutes a formidable weapon of attack and -defence, is not only in such a position as to be ready for immediate -use; but, lying as it does in front of the body, with other portions -hidden more or less behind it, it serves the purpose of a shield when -the animal retires. - -If we place a homeless hermit crab in a rock pool, the behaviour of the -creature immediately suggests a feeling of uneasiness--a sense of -danger--for it moves about in a very erratic fashion that is quite -different from the straightforward and deliberate action of the same -animal when properly protected; and very amusing results may be obtained -by making it the subject of a few harmless experiments. For instance, -drop down before it an empty whelk-shell that is much too large to -properly accommodate its body. It will immediately approach the -untenanted house, search and probe it well with its antennae and other -appendages, and then, finding it uninhabited, and having no apartment of -more suitable size at hand, will abruptly gives its body a turn and -hastily thrust itself backwards into it. - -If at the time of this experiment the advancing tide disturbs the water -of the pool, the result is somewhat ludicrous, for the shell, too -cumbersome to be controlled by the creature within, is, regardless of -its attempts to maintain a normal position, turned over and over as each -wave advances and retreats. - -Again, supposing the shell supplied to be too small for the intended -occupant, it will, after the usual examination of the interior, thrust -its soft abdomen as far in as possible, and make the best of the -unsatisfactory circumstances until a more suitable home can be found. -And if, at this distressing period, we drop before it a shell of just -the right size--the one from which the creature was originally expelled -for instance, it is astonishing how quickly the change of houses will be -accomplished. After a brief examination of the shell with the object of -determining whether all is right within, during which the crab continues -to avail itself of the imperfect accommodation afforded by the previous -shell, it rapidly extracts its body from the one and thrusts itself -backwards into the other. Its normal habits are at once resumed, all its -movements being now suggestive of confidence and contentment. - -We have already referred (p. 153) to the fact that a large anemone -(_Sagartia parasitica_) is commonly found attached to a whelk shell, -which at the same time forms the home of the hermit crab, and (p. 44) -that a marine worm (_Nereis_) is also a common associate of the hermit, -taking up its abode in the interior of the same shell; and we also -briefly discussed the mutual advantage of such an arrangement to the -parties concerned. These triple combinations are not so frequently met -with on the shore between the tide-marks, but are dredged in -considerable numbers by the trawler; and the reader will find it repay -him to secure one in order that he may be able to watch the interesting -habits of the associates. The movements of the hermit crab are always -pleasing, particularly the manner in which it seizes and manipulates its -food; and still more so is the occasional appearance of the head of the -worm, always in exactly the same place, for the purpose of deliberately -stealing the food from the very jaws of the crab. - -Hermit crabs are easily kept in captivity, and may be fed on any kind of -animal food, but care should be taken not to allow an excess of food to -remain in the water and render it putrid by decomposition. As long as -the crabs are active and remain within their shells you may assume that -the conditions are favourable; but when they become sluggish in their -movements, and leave their homes, the sanitary condition of the -aquarium should be regarded with suspicion; for hermit crabs, like many -of the marine tube worms, generally quit their homes when the conditions -are unfavourable, as if they preferred to die outside. - -The Common Hermit Crab (_Pagurus Bernhardus_), also known as the Soldier -Crab, on account of its very pugnacious habits, is common almost -everywhere on our coasts, and may be distinguished by the numerous -little tubercles on the claws and on the upper edge of the front legs; -and there are several other species, belonging to the same genus, -distributed more or less locally on the various shores. All are similar -in general structure and habits, the various species being identified -principally by means of their colour, the variations in the form of the -appendages, and the general character--smooth, tubercular, spiny, -&c.--of the exo-skeleton. One species, found in the sandy bays of -Cornwall, burrows rapidly in the sand. - -Coming now to the true crabs--the _Brachyura_, or Short-tailed -crustaceans, as sometimes distinguished from the _Anomura_--we find -quite a variety of interesting creatures, many species of which are -always within the reach of the collector at work between the tide-marks. -In all these the abdomen is only slightly developed, and is never used -in swimming, being permanently folded beneath the thorax. This portion -of the body, however, is usually very distinctly segmented, and if it be -lifted from its position it will be found that some of the segments bear -appendages corresponding with the swimmerets of the lobster. It is also -wider in the female than in the male, and crabs of the former sex may -often be found during the summer with the abdomen more or less -depressed, and the space beneath it quite filled with eggs. - -The upper surface of the carapace of crabs is often very distinctly -grooved, and it is interesting to note that these features of the -exo-skeleton are not merely of external significance, for they usually -correspond in position with various internal structures, some of them -denoting the areas of the insertions of important muscles, and others -enclosing the regions of certain of the internal organs. - -It will be noticed, too, that the carapace, which in lobsters is often -less than half the length of the body, covers the entire body of the -crab, except, perhaps, a very small linear portion between the bases of -the last pair of legs, where the first part of the segmented abdomen is -visible from above. - -The true crabs of our seas may be divided into four groups, as follow: - - 1. _Oxystomata_, or Pointed-mouthed Crabs; - 2. _Oxyrhyncha_, or Pointed-beaked Crabs; - 3. _Catometopa_, with forehead turned downwards; and - 4. _Cyclometopa_, or Round-headed Crabs; - -and we shall briefly observe some of the more conspicuous and -interesting species in the order of the tribes as just given. - -The first division is not well represented in our seas, the principal -species being the Nut Crabs and the Long-armed Crab, all of which may be -distinguished by the peculiar arrangement of the foot-jaws, which, when -closed, form a triangle with an acute angle turned towards the front. -The Nut Crabs are mostly small; and, since they generally inhabit deep -water, are not commonly seen on the shore; but perfect specimens may -sometimes be found among the contents of fishes' stomachs. They derive -their name from the nature of the carapace, which is of a rounded form -and very hard and strong. - -Pennant's Long-armed Crab (_Corystes Cassivelaunus_) may commonly be -seen entangled among fishermen's nets, but is not often seen on the -shore at low tide. Its carapace is very convex above, with three sharp -spines on each side, and the grooves are so arranged as to suggest the -appearance of a face. Our illustration represents the female, but the -'arms' of the male are very much longer than those of this sex. - -The Sharp-beaked Crabs (_Oxyrhyncha_) include all those long-legged -creatures that are known collectively as the Spider Crabs; and here, -again, we have to do with species that almost exclusively inhabit deep -water. Although this is the case, but little difficulty is experienced, -as a rule, in obtaining specimens. If you are unable to take a trip in a -trawler for the purpose of examining the 'rubbish' that is dredged from -deep water, simply obtain permission to search the nets and the boats as -they arrive in port. In the latter case you are almost certain to find -the crabs you require, though it is probable that some of the species -will have been damaged by the hauling and shaking of the nets. - - [Illustration: FIG. 214.--THE LONG-ARMED CRAB (_Corystes - Cassivelaunus_)] - -These interesting crabs have been spoken of as the monkeys of the sea, -and the comparison will certainly be tolerated by anyone who has watched -the creatures as they climb among the corallines and sea firs in an -aquarium. Among such growths they are quite at home; and although their -movements do not often suggest the extreme agility of the monkey tribe, -yet the ease with which they seize the branches of the submarine forest -with their long 'arms' and pull their bodies from one tree-like -structure to another is decidedly monkey-like. Their comparison with the -long-legged spiders is also a happy one as far as their general form and -movements are concerned, but it must be remembered that they have not -the same reputation for cruel, predaceous habits, for they are more -truly the scavengers of the deep, subsisting mainly on the decomposing -bodies of their dead associates. The movements of most spider crabs are -so slow and deliberate that one can hardly imagine them capable of -anything of the nature of violent action; yet, when occasion requires -it, they will sometimes strike at the object of their wrath with a most -vigorous snap of their claws. - - [Illustration: FIG. 215.--SPIDER CRABS AT HOME] - -In these crabs, too, we find most interesting instances of protective -resemblance to their surroundings. Some of the small, slender-legged -species are not to be recognised without a careful search when they are -at rest among clusters of sea firs, their thin appendages and small -bodies being hardly discernible in the midst of the slender, encrusted -branches, and their peculiar forms are still more concealed by their -colouring, which generally closely resembles that of the growths among -which they live. Further, the carapace of spider crabs is in itself a -garden on which thrive low forms of both animal and vegetable life. -Minute _Algae_, and occasionally some of moderate size, are rooted to the -shell, often securely held by the aid of the rough hairs and tubercles -that are so characteristic of the exo-skeletons of these creatures; and -patches and tufts of animal colonies that have found a convenient -settlement on the moving bed still further serve to obscure the nature -of the living mass below--a mass that is always in danger of becoming -the prey of the fishes which inhabit deep water. It is probable, -therefore, that this association is one that is beneficial to both -sides as far as the animal life is concerned, the lower species serving -to disguise the true nature of the crab, thus protecting it from its -numerous enemies, while they in return are conveyed, carriage paid, to -the feeding-grounds, where they can freely partake of the fragments that -become diffused in the surrounding water. - -Our illustration on p. 288 shows three species of spider crabs, all of -which are common on parts of our shores. The Scorpion Spider Crab -(_Inachus dorsetensis_) derives its specific name from the fact that it -was first found off the coast of Dorset; but it is abundant off many of -our shores, both in the south and north, and may frequently be seen -entangled among the fishermen's nets. It may be distinguished from other -and similar species by the four spines arranged in a line across the -front portion of the carapace, and the five large, pointed tubercles -behind them. This species is undoubtedly a favourite food of the cod, -for several specimens may often be taken from the stomach of a single -fish. - -The next species--The Slender-beaked Spider Crab (_Stenorhynchus -tenuirostris_)--is seldom missing from the dredgings hauled in off the -south-west coast, and is fairly common in other parts. Its legs are -extremely slender, and bear spines on the inner side, and its body, -where free from the incrustations so often covering the carapace of -spider crabs, is of a fresh pink colour. - -The other one shown in the same illustration is _Arctopsis lanata_, -sometimes known as Gibb's Crab, the carapace of which is pointed behind, -bears a large pointed tubercle on each side, and is completely covered -with a thick clothing of stiff hairs. It is also common on many parts of -our coasts, more especially the coasts of Devon and Cornwall. - -Closely allied to the last-named, and belonging to the same family, is -the well-known Thornback Crab (_Maia Squinado_), also a very common -crab, of which we give a separate illustration. - -The tribe _Catametopa_ does not contain many British species, the -principal being the Pea Crabs; the Floating Crab, which is occasionally -washed on the south-west coast; and the beautiful Angular Crab. In these -the front of the carapace is turned downwards--a feature that has -suggested the name of the tribe. - -The pea crabs are all small, and they are parasites, living within the -shells of bivalve molluscs. One species--the Common Pea Crab -(_Pinnotheres pisum_) is frequently found in the Edible Mussel; the -female, which is much larger than the male, being much more commonly -found. Another species--the Pinna Pea Crab (_P. veterum_), infests the -Pinna and Modiolus. - - [Illustration: FIG. 216.--THE THORNBACK CRAB (_Maia Squinado_)] - - [Illustration: FIG. 217.--THE PEA CRAB (_Pinnotheres pisum_)] - -On Plate VI. is a drawing of the Angular Crab (_Gonoplax angulata_) -mentioned above, the striking form and delicate colouring of which can -never be mistaken. We would, however, call particular attention to the -broad and square front of the cephalothorax, with its two sharp spines, -and to the length of the eye-stalks. Unfortunately for the amateur, this -pretty crab is only to be found in deep water, off the coasts of Devon -and Cornwall, so that here, again, the aid of the fisherman is valuable; -but, as observed in the case of other deep-sea dwellers, may also be -looked for in the stomachs of cod and other bottom fishes. The sex -figured is the male, in which, when fully grown, the front legs are much -longer than in the female. - - [Illustration: PLATE VI. - - CRUSTACEA - - 1. Gonoplax angulata - 2. Xantho florida - 3. Portunus puber - 4. Polybius Henslowii - 5. Porcellana platycheles] - -The remaining division of the crabs--the _Cyclometopa_ or Round-fronted -Crabs, contains the larger number of species that may truly be described -as common objects of the shore, for while some of them are well adapted -for swimming, and live in the open water, the majority inhabit the -shore, either between or just beyond the tide-marks, roaming about more -or less freely when in the water, but usually hiding under stones or -weeds, or burrowing into the sand, when left behind by the receding -tide. - - [Illustration: FIG. 218.--THE COMMON SHORE CRAB (_Carcinus maenas_)] - -The members of this tribe may be known at sight by the form of the -carapace, which is wide and rounded in front, and narrowed behind. - -The accompanying illustration represents the commonest of the group--the -Common Shore Crab (_Carcinus maenas_), which is found plentifully on all -our coasts, and even in brackish water far up the estuaries of rivers. -It is a very voracious and pugnacious creature, probably the most active -of all our crabs, and its movements, whether connected with its feeding, -its sports, or its warfare, are always very interesting when observed -through clear water. This crab varies considerably in colour, but is -usually of the greenish tinge shown in the frontispiece. - -Another abundant and well-known species is the Edible Crab (_Cancer -pagurus_), which is as familiar an object in town as on the sea coast. -Unlike the common lobster, its natural colour is not considerably -changed by boiling, being only turned from a dull to a brighter red. - -The finest specimens of this crab are to be caught beyond low-water -mark, the usual snare being the basket or pot, baited with fish refuse, -but large numbers live among the stones and rocks left exposed at low -tide, and sometimes include specimens of considerable size. They should -be looked for under large stones that are loosely piled together, or in -the narrow chinks of rocks. - -It is very interesting to compare the habits of the two common crabs -just mentioned. The former, when molested, will run off in great haste, -but always retreat with its front to the enemy, and its sharp and -powerful pincers far apart and wide open, ready for immediate use in its -own defence if necessary. The latter species, on the other hand, though -strongly built and provided with formidable claws, seldom runs far, and -hardly ever attacks one in the act of pulling it out of its -hiding-place; but, on the contrary, doubles all its ten legs under its -body as if endeavouring to approach, as nearly as possible, the form of -a ball, and will allow itself to be rolled about without showing any -signs of life. - -The genus _Xantho_ contains two or three species that are common on the -Cornish and Devon coasts, and which may be known by their depressed and -deeply-grooved carapace and the presence of three or four prominent -tubercles on the latero-anterior margins. The abdomen of the female has -seven joints, while that of the male has only five. One of these -(_Xantho florida_), shown on Plate VI., is a powerfully built crab, as -may be seen when, after being disturbed, it pushes its way among the -loose stones of the beach, often lifting masses many times its own -weight. - -On the same plate is also a figure of the pretty Velvet Crab (_Portunus -puber_), also known as the Lady Crab and the Violet Fiddler. The first -of these popular names has its origin in the dense covering of close -hairs that clothe the carapace, and the last refers to the beautiful -violet colouring of parts of the front legs, and, to a lesser extent, of -the remaining legs. This is, perhaps, the most ferocious of all our -shore crabs, and its attacks, when disturbed, are of such a determined -nature that the catching of the larger specimens is quite a lively -sport. Though it can hardly be described as an abundant species, yet it -sometimes occurs locally in such numbers that it may be found under -nearly every stone of any size. In fact, we have searched two or three -localities on the south-west coast where this crab is not only -extremely numerous, but is at the same time almost the only species to -be found; and it seems not unlikely that the pugnacious Lady has been -the means of driving the less formidable species from its favourite -haunts. - -When you disturb a Velvet Crab it will immediately raise itself in a -menacing attitude, stretching its brightly coloured pincers as wide -apart as possible, and then it will either retreat backwards, or even -make a firm stand, ready to strike as soon as it is threatened with an -attempted touch. Try to grasp it, and its two powerful weapons of -defence are brought together with lightning-like rapidity giving one a -decidedly smart blow, possibly followed by a grip of great tenacity for -a creature of its size; but, should it miss its aim, its pincers strike -together with a sharp click, only, however, to extend at once in -preparation for the next attempt. - -It will be observed that the walking legs of this crab are all -flattened, and that while the first three pairs terminate in sharp, -lance-like claws, the last pair are broad and fringed with hairs, thus -showing their close relationship to the swimming crabs. In fact, the -same genus contains British species which are popularly known as -Swimming Crabs. - -One of the swimmers is represented in fig. 4 of Plate VI. It is -generally known as Henslow's Swimming Crab or the Nipper, the scientific -name being _Polybius Henslowii_. The carapace of this species is quite -smooth, thus enabling the crab to move through the water with less -resistance, and the walking legs, particularly the last pair, are -flattened and fringed for use as paddles. It is said that this crab can -raise itself from the bottom to the surface of moderately deep water by -means of the swimming feet, and that it preys on fishes which it pursues -with some vigour. - -Other crabs than those briefly described will reveal themselves to the -sea-side collector, but we have not the space to introduce them here. -Sufficient information has been given, however, to enable the reader to -broadly classify his specimens--a matter of more importance to the young -naturalist than the mere naming of species. - -Leaving the crustaceans now, and passing for a moment to the -_Arachnoidea_--the second great division of the arthropods--we shall -briefly describe the Shore Spider (_Pycnogonum littorale_), which is the -only representative of the class likely to be met with by the sea-shore -collector. - -It will be seen by our illustration that this creature by no means -resembles a typical spider. The powerful jaws, really modified antennae, -that are such formidable weapons in the latter, together with other -appendages of the head, are undeveloped in the shore spider, and the -head is prolonged forward to form a rigid beak with the mouth at the -summit, and the head and thorax together form a cephalothorax of four -distinct segments, each of which bears a pair of legs. Further, the -cephalothorax forms almost the whole of the body, for the abdomen, -usually so large in spiders, is here represented by a mere tubercle. The -shore spider is unable to swim, but crawls about among the weeds and -stones of the bottom, clinging firmly by means of the curved claws of -its eight thick legs, and is protected by its dull grey colour which -closely resembles that of the encrusted stones among which it spends the -greater portion of its existence. It may sometimes be found hiding under -stones near low-water mark, but is far more commonly seen among the -'rubbish' hauled in by the trawl. - - [Illustration: FIG. 219.--THE SHORE SPIDER] - -We shall conclude our brief survey of the marine arthropods by a short -account of the insect life of the sea shore, referring to a few of the -more prominent forms and observing some of their habits; but since it is -probable that some of our readers are not well acquainted with the -general characters of this interesting class of animal life, it will be -advisable to precede our remarks by a short summary of their principal -distinguishing features, more particularly those in which they differ -from the other arthropods. - -Insects, then, may be defined as those arthropods in which the body is -divided into three distinct parts--the _head_, composed of from four to -six fused segments, and bearing as many pairs of appendages; the -_thorax_, formed of three segments, each of which gives attachment to a -pair of legs; and the _abdomen_, composed of eight segments that bear no -appendages. - -The head of an insect is furnished with a pair of compound eyes, very -similar in structure to those of a crustacean, and often, in addition, a -cluster of simple eyes; also a pair of antennae, usually composed of many -joints. These antennae are important organs of touch, and are employed, -at least by many forms, as a means of communication between one insect -and another. In them are also located the organs of hearing, and, -possibly, those of other senses. - -The mouth varies very considerably in different insects, but is often -supplied with a pair of mandibles or biting jaws, and, below them, a -pair of maxillae or chewing jaws, both pairs being jointed to the head in -such a manner as to be capable only of horizontal movements. Above and -below these jaws are, respectively, the upper lip or labrum, and the -lower lip or labium, the latter having appended to it a pair of jointed -feelers called the labial palpi, and an additional pair of palpi are -also frequently attached to the maxillae, and therefore called the -maxillary palpi. - -These organs of the mouth of an insect are modified in various ways -according to the functions they are called upon to perform. Thus, in -bees, the upper lip, as well as the mandibles, are adapted for chewing, -while the maxillae and the labium are grooved in such a manner that when -brought together they form a tube through which fluids may be sucked -into the mouth. Also, in the butterfly and the moth, the maxillae are not -constructed for chewing, but consist of two channelled rods which, when -approximated, form a long tube or proboscis employed for suction; and in -these insects the labial palps are large for the protection of the -proboscis, which is retracted and closely coiled between them when not -in use. Further, in the bugs, the labium is long and tubular, while the -mandibles and maxillae are often modified into sharp, stiff bristles that -work within the tube, the whole thus forming a combined piercing and -sucking arrangement. - - [Illustration: FIG. 220.--THE LEG OF AN INSECT] - -The leg of an insect is built up much in the same manner as that of the -typical crustacean. It consists of a basal hip joint or coxa, a ring -segment or _trochanter_, a thigh (_femur_), a shin (_tibia_), and the -tarsus or foot of several joints which terminates in a claw or claws, -and is often provided with sucking-pads. The wings, when present, are -attached to the second and third segments of the thorax, if two pairs, -but if, as in the case of the house fly, the insect has only one pair of -wings, these are always appended to the second segment. - -Insects are developed from eggs, but in their young state they are -segmented larvae, with strong jaws, antennae, simple eyes, and usually -three pairs of legs attached to the first three segments next to the -head. - -As regards internal structure, we need only mention here that the body -is traversed by numerous branching tubes (_tracheae_) that open at the -exterior and constitute the respiratory apparatus; that the insect is -provided with a contractile, tubular heart by means of which the blood -is propelled through a system of blood-vessels; that the nervous system -consists of a chain of ganglia, connected by a nerve cord, sending nerve -filaments to all parts of the body; and that the digestive tube is often -a complicated structure, especially in the case of those insects that -feed on herbivorous matter. - - [Illustration: FIG. 221.--TRACHEA OF AN INSECT, MAGNIFIED] - -The above outline will be sufficient to show that insects are not very -unlike the crustaceans in their general characteristics; and, indeed, -when we examine certain forms, noting the distinct segmentation of the -body, the hardened exo-skeleton of chitinous material, and the -unhardened skin between the segments to admit of freedom of movement, we -see a striking resemblance in external appearance to some of the typical -crustaceans. - -Insects are divided into several orders, and some of these are fairly -well represented on the sea coasts, though it must be understood that -but few species are strictly aquatic and marine in their habits. -Fresh-water pools and streams teem with insect life, and quite a large -number of the insects that live in these situations are peculiarly -adapted for a life of submersion, their general form being often such as -to allow of rapid progress through the water, their appendages modified -into admirable swimming organs, and, in many cases, their breathing -apparatus adapted for the direct absorption of oxygen dissolved in the -water. - -However, one would hardly expect to find similar forms of life abundant -in the water that washes our shores, the disturbing action of the waves, -even in calm weather, being more than such fragile creatures could -withstand. And this is really the case, for there are but few insects -that may be described as marine in the strictest sense of the word; and -of these the species that have been observed are mostly inhabitants of -warmer seas. - -It is noteworthy that all the insects which exhibit marine tendencies -are small, and they seldom, if ever, live permanently below the surface. -But few of them can swim. A few run on the surface of the water, -supporting themselves on the surface film after the manner of -water-gnats, whirligig beetles, &c., without ever being wetted; and -these are said to feed on different kinds of floating matter, and -occasionally to dive below the surface. - -A rambler on the sea shore in the summer time will always meet with -plenty of insect life, but the number of species observed may not be -large: and omitting all those which show no decided preference for the -coast, but are found in inland districts as well, we find that by far -the larger proportion live at or near the high-water mark, where they -feed on the refuse washed up by the waves. Some species, however, live -among the stones, or burrow into the sand, between the tide-marks; and -these, as a rule, are not driven inland by each advancing tide, but -allow the sea to wash over them, having at first protected themselves -from disturbance by burrowing or seeking other suitable shelter. - -These latter, like many of the insects that inhabit fresh water, are -well adapted to withstand prolonged immersion. Their bodies are not -capable of being wetted, a covering of short hairs effectually -preventing the water from coming into actual contact with the body. The -openings of the breathing tubes (spiracles) are also guarded by closely -set hairs which prevent the water from entering; and, in some cases, the -creatures are provided with special air-sacs in which a supply of air is -stored for use while the insect is shut off from the external -atmosphere. - -The lowest order of insects includes the so-called Bugs (_Rhynchota_), -which are parasitic on plants or animals. Quite a number of these are to -be found inhabiting fresh water, but only one is truly marine in its -tendencies. This one is a small insect, only about an eighth of an inch -in length, and named _AEpophilus_ (fig. 222). It has never been seen -except between the tide-marks, and occurs so near low-water level that -it is submerged during the greater part of its existence. But little is -known of this peculiar creature. Even its food has not been ascertained. -As with the other Rhynchota, but little change of form takes place -during growth, the young being very much like the adult in appearance. -It has been observed that the larvae live crowded together under the -protection of stones. - -The reader is probably acquainted with those fresh-water bugs that are -popularly known as 'boatmen' on account of the oar-like action of their -long, fringed hind legs; and although none of these may be described as -marine, yet certain species may often be seen in salt and brackish -water, living in company with creatures that are decidedly inhabitants -of the sea. - - [Illustration: FIG. 222.--SEA SHORE INSECTS - 1. _AEpophilus._ 2. _Machilis maritima._ 3. _Isotoma maritima._ - 4. _Coelopa_] - -We frequently meet with a pretty, slender-bodied insect, measuring about -half an inch in length without appendages, creeping over the rocks in -the sunshine, generally very near the crevices in which they hide, and -leaping from place to place when disturbed. These are the Bristle-tails -(_Machilis_), belonging to the order _Thysanura_, the members of which, -like the bugs, scarcely undergo any metamorphoses. This insect (fig. -222) has long antennae, and also a long, stiff, and elastic bristle -extending backwards from the tip of the abdomen; and this bristle is the -means by which the creature leaps. Occasionally the machilis may be -found resting on the surface of the still water of a rock pool, in which -case its body is not wetted, its weight not being sufficient to break -the surface film of the water; and, in fact, the film is even -sufficiently firm to enable the insect to leap on the surface just as it -would on a solid body. - -Allied to the bristle-tails, and usually grouped with them in the same -order, are the little Spring-tails, some species of which may often be -seen huddled together on the surface of the water of a rock pool. They -are so small that, unless closely examined, they may be mistaken for -particles of floating inorganic matter which have been blown into a -sheltered corner of the pool, and this idea may be strengthened by the -fact that these minute creatures _are_ driven by the wind into such -sheltered spots. But when we disturb them their true nature immediately -becomes apparent, for they may then be seen to move about on the surface -of the water, sometimes creeping on the surface film, and clambering on -the adjacent rock or weed, or leaping more or less vigorously, in which -latter case their bodies do not become wetted, the surface film -remaining unbroken by their exertions. And even when the rising tide -drives the spring-tails into crevices where they remain submerged, -perhaps for hours together, their bodies still remain dry, the water -being kept off by numerous short bristles and prominences with which -they are furnished. - -When we examine a spring-tail by means of a lens we observe that it has -no traces of wings, but that each of the three segments representing the -thorax bears a pair of short legs, and that the abdomen consists of only -five or six segments. The head is furnished with a pair of jaws, and the -antennae, which are short and thick, are composed of but few -joints--never more than six in number. - -Some spring-tails live among the refuse washed up on the beach, where -they may be seen jumping about in company with the sandhoppers when the -material is disturbed. Such is the case with _Isotoma maritima_, the -illustration of which shows the forked tail that enables the little -animal to jump about so vigorously. But some of the marine spring-tails -are not so true to their name, since they are not provided with this -characteristic jumping organ, and have to content themselves by creeping -about slowly with the aid of their short legs. One of these springless -spring-tails (_Anurida maritima_) is one of the commonest of the group, -and is distributed over almost every part of our coast. - -Passing over several orders of insects which do not seem to have any -marine representatives, we come to the _Diptera_ or two-winged insects, -of which the familiar house-fly is a type, and here we have to deal with -those troublesome creatures that literally swarm in the neighbourhood of -the matter washed up to the highest level of the tide during the whole -of the summer months. But although these insects are so very numerous, -we do not find among them a particularly large number of species, their -abundance being due more to the extreme prolificacy of those that -occur. - -In this order, which includes all gnat-like creatures, as well as those -insects that are generally known as flies, the first pair of wings are -well developed, while the second pair are rudimentary, and represented -merely by a pair of scales, or by two little pin-like bodies called the -balancers or _halteres_. Some are provided with piercing organs by means -of which they can inflict a small wound and then extract the juices of -their victim, as does the female gnat, but the majority have a proboscis -adapted for suction only. The larvae of the _Diptera_ are generally -limbless maggots, gifted with a pair of jaws, and they are usually very -voracious feeders, devouring decomposing animal or vegetable matter in -enormous quantities. - -If we turn over a fermenting mass of the miscellaneous matter thrown up -on the beach quite beyond the reach of the tides, we may observe a -multitude of little maggots which feed on the moist, odorous portion -that was protected from the direct rays of the sun, together with a -number of dark-coloured pupae that lie at the very bottom of the heap or -buried in the sand below. These are two stages of the black fly -(_Coelopa frigida_) that is so attentive to us when we rest on the dry -sand above high-water mark. This fly is very like the common house-fly -in general appearance, though its body is rather smaller. Other species -of the same genus often accompany them, all being very similar in -general appearance and habits, and none of the larvae seem adapted to a -life in the water. They are always found beyond the reach of the tide, -and are drowned if submerged for any length of time. - -Another species belonging to the genus _Actora_ will often be seen in -the same company, and this is readily distinguished by their lighter -greyish colour and its superior size. Also, along the water-line, we -often meet with species of the family _Dolichopodidae_, so called on -account of the length of their legs, and noted for the beautiful -metallic colours which adorn their bodies. These flies are carnivorous -in habit, deriving their food from living as well as from freshly killed -animals, and their short, fleshy proboscis contains a piercing bristle -by which they can puncture the skins of the animals that provide them -with food. Most of the flies of this group live on trees, walls, fences, -&c., where they pursue and attack their prey, but certain species follow -the line of breakers on the sea shore, as before indicated, and obtain -their food from the various marine animals that are stranded on the -beach. A peculiar feature of the family is the nature of the abdomen of -the males, which is bent under the body and furnished with a number of -appendages. - -Another marine dipterous insect is a gnat-like fly closely allied to -_Chironomus_, which we have described in a former work[A] of this series -dealing with fresh-water life; and it will be sufficient to mention here -that _Chironomus_ is commonly known as the window-gnat on account of the -frequency with which it may be seen flying on the windows of our -dwellings; also that the larva, known popularly as the bloodworm, is -truly aquatic in habit, being able to swim by rapidly looping its body -in opposite directions, and being provided with a breathing apparatus -adapted for the absorption of the oxygen gas contained in solution in -water. The larva of the marine species referred to above may sometimes -be seen in rock pools, where it shelters itself among the sediment at -the bottom. It is much like the bloodworm in appearance and structure, -but its body is greenish instead of red. - -The last order of insects calling for notice here is the _Coleoptera_ or -sheath-winged insects, popularly known as beetles, and characterised by -the hard and horny nature of the front pair of wings (elytra), which are -modified into sheaths and serve to protect the second pair; the latter -are thin and membranous, usually adapted for flight, and lie folded -beneath the former when not in use. - -One large section of beetles is known as the _Geodephaga_ or Ground -Beetles--a group of very predaceous insects that burrow into the soil -and attack almost every living thing that comes in their way, and well -represented by numerous species that may be found in our gardens, and, -in fact, almost everywhere. - -A considerable number of these insects show a decided preference for -salt marshes and the sea shore, where they hide under stones, or burrow -into the sand or mud in search of their prey. They are not marine in the -strictest sense of the word, for they are not adapted for a life of -submersion in water, either in the larval or in the perfect condition; -yet they are often found below high-water level, and some species burrow -into the sand of the beach as the tide advances, allowing the water to -cover them for hours together. - -One interesting family of the ground beetles (the _Bembidiidae_) includes -several small species, all of which frequent salt and wet places, such -as salt marshes, the mouths of rivers, and the sea shore. We give -enlarged illustrations of a few of these, the actual size being denoted -at the side of each. - -[Footnote A: _Life in Ponds and Streams._] - - [Illustration: FIG. 223.--MARINE BEETLES OF THE GENUS _Bembidium_ - 1. _B. biguttatum._ 2. _B. pallidipenne._ 3. _B. fumigatum._ - 4. _B. quadriguttatum_] - -_Bembidium biguttatum_ may be identified by its brilliant bronze-green -colour, and the two distinct impressions on the elytra which have -suggested the specific name. _B. pallidipenne_ is, as its name implies, -a pale-winged species, the elytra being of a light yellowish colour. _B. -fumigatum_ is so called on account of the smoky tint of the elytra; and -the last species of the same genus figured (_B. quadriguttatum_) may be -known by the four conspicuous spots on the deep violet-coloured outer -wings. - -The same family contains an interesting little beetle--_Cillenium -laterale_--only about one-sixth of an inch in length, that lives among -the refuse washed on the beach, where it feeds on the sandhoppers; and -although the latter are so much superior in size, the beetle has no -difficulty in holding and killing its prey, always seizing it on the -ventral side of the body, which is less protected by the hardened skin. -This species, which is of a copper colour, does not confine its ravages -to that portion of the beach which is above high-water mark, but often -allows itself to be covered by the advancing tide, remaining submerged -for a considerable time. Another species--_Aepus (AEpys) marinus_--is -even more aquatic in its habits, for it searches out its prey among -stones, chiefly at the mouths of rivers, below high-water level, and is -often submerged for hours together. It is even provided with air-sacs to -enable it to withstand such prolonged submersions. - - [Illustration: FIG. 224.--MARINE BEETLES - 1. _AEpys marinus._ 2. _Micralymma brevipenne_] - -There is another section of beetles which has elytra so short that they -cover only a small portion of the abdomen; but although so short, these -elytra completely cover the long membranous wings, which are folded up -beneath them in a wonderfully compact manner. The section referred to is -termed _Brachelytra_, from the feature just mentioned, and includes a -few species that are more or less marine in their habits. One of -them--_Micralymma brevipenne_--lives under stones below high-water -level, and apparently passes through all its stages within reach of the -waves. Another of the _Brachelytra_ (_Bledius_) burrows into the sand or -mud near high-water mark, throwing up the debris as it proceeds. Both -these beetles are carnivorous, and the latter is in turn preyed upon by -a ground beetle of the genus _Dyschirius_, which hunts and devours it -within its own home. - -The reader will have observed that the sub-kingdom _Arthropoda_ is not -only a very extensive one in the sense that it contains a vast number of -animal forms, but also that its members exhibit a very great variety of -form and structure; and the beginner will probably find no little -difficulty in locating his specimens in their correct position in the -scale of life. The following table, however, will serve to show the -general classification of the group at a glance, and thus form a basis -for a more detailed study at any future time:-- - - - - - SUB-KINGDOM ARTHROPODA - - CLASSIFICATION - - - Class =CRUSTACEA=. - Sub-class =ENTOMOSTRACA=. - Order =Astracoda=--Free. Body enclosed in a bivalve shell. - Order =Copepoda=--Free. Five pairs of feet adapted for swimming. - Order =Cirripedia=--Sessile. Enclosed in a shell of many valves. - Order =Branchiopoda=--Free. Gills attached to feet. - Sub-class =MALACOSTRACA=. - Division =EDRIOPHTHALMATA=, or Sessile-eyed Crustaceans. - Order =Isopoda=--Body flattened. Seven pairs of legs--equal. - Order =Amphipoda=--Body flattened laterally. Legs adapted for - both walking and swimming. - Division =PODOPHTHALMATA=, or Stalk-eyed Crustaceans. - Order =Stomapoda=--Anterior appendages directed towards the - mouth. - Order =Schizopoda=--Cleft-footed Crustaceans. - Order =Decapoda=--Ten-footed Crustaceans. - Sub-order =Macrura=--Great-tailed. Lobsters, &c. - Sub-order =Brachyura=--Short-tailed. Crabs. - - Class =ARACHNOIDEA=. - Order =Scorpionidae=--Scorpions. - Order =Araneidae=--Spiders. - Order =Acarina=--Mites. - - Class =MYRIOPODA=. - Order =Chilopoda=--Centipedes. - Order =Chilognatha=--Millepedes. - - Class =INSECTA=. - Order =Rhynchota=--Imperfect metamorphoses, suctorial mouth. - Bugs. - Order =Thysanura=--Imperfect metamorphoses. No wings. - Divided tail. Spring-tails. - Order =Euplexoptera=--Abdomen with terminal forceps. Earwigs. - Order =Thysanoptera=--Four equal membranous wings. Thrips. - Order =Orthoptera=--Anterior wings usually shorter and firmer. - Grasshoppers, &c. - Order =Neuroptera=--Two pairs of glassy wings--equal. - Order =Trichoptera=--Wings unequal, clad with hairs or scales. - Caddis flies. - Order =Aphaniptera=--No wings, no compound eyes. Fleas. - Order =Diptera=--Two membranous wings. Flies. - Order =Lepidoptera=--Wings clad with scales. Butterflies and - Moths. - Order =Coleoptera=--Fore wings hard and horny. Beetles. - Order =Hymenoptera=--Four membranous wings. Larvae, footless - grubs. Ants, Bees, &c. - - - - - CHAPTER XIV - - _MARINE VERTEBRATES_ - - -The vertebrates form the highest sub-kingdom of animal life--the -sub-kingdom to which we ourselves belong, the chief distinguishing -characteristic of the group being the presence of an internal skeleton, -the principal part of which consists of a rod or column of cartilaginous -or bony material running along the dorsal side of the body, known as the -_vertebral column_. - - [Illustration: FIG. 225.--TRANSVERSE SECTION THROUGH THE BONY - FRAMEWORK OF A TYPICAL VERTEBRATE ANIMAL - 1. Spinous process of the vertebra. 2. Neural arch. 3. Transverse - process. 5. Body of the vertebra. 6. Breast-bone. 7. Rib. The space - between 2 and 5 is the neural cavity; and that between 5 and 6 is - the visceral cavity] - -This column is usually composed of a number of elements called vertebrae, -each of which gives off two processes that unite and form an arch on its -dorsal side, while all the arches form a tube through which passes the -central portion of the nervous system. - -Below, or on the ventral side of the column, is the body-cavity -containing the organs of digestion and circulation; so that if we make a -transverse section of a vertebrate animal we find that there are two -distinct tubes or cavities--a _neural_ or _cerebro-spinal cavity_ on -the dorsal side of the vertebral column, formed by extensions from the -substance of the latter, and enclosing the chief portion of the nervous -system; and a _body-cavity_ on the ventral side containing the viscera -or internal organs. - -The above features are highly important, and will always prove quite -sufficient to enable us to decide whether any particular animal is a -vertebrate or an invertebrate, for it will be remembered that the body -of the latter has only one cavity, containing the nervous system as well -as the viscera, and that the nervous system is commonly placed along the -ventral side, but never along the dorsal. In addition to this the -vertebrates never have more than two pairs of limbs, and these are -always directed _from_ the nervous system; and the jaws, which are -appendages that move in the horizontal plane in invertebrates, are, in -the higher animals, portions of the framework of the head and move -vertically. In vertebrates, too, there is always a complete blood -system, consisting of a heart with two, three, or four cavities, a -system of arteries to convey the blood to the different parts of the -body, veins to return the blood to the heart, and networks of fine -capillaries connecting the former with the latter. - -All vertebrates, at an early stage of their existence, have a -cartilaginous rod running through the dorsal portion of the body, called -the _notocord_. In some of the lowest animals of the division this rod -persists without any important alterations in structure, while in the -higher forms it gives place to the series of cartilaginous or bony -elements above referred to as the vertebrae; and the arrangement of the -vertebrates into their relative positions in the scale of life is based -largely on the degree of development of the vertebral column from the -notocord. Another interesting feature in the development of a vertebrate -is the formation of five or more transverse, archlike thickenings on -each side of the digestive tube, just behind the head; and, in the -spaces between them, of a series of slits forming a communication -between the pharynx and the exterior. These arches and clefts have but a -brief existence in many vertebrates, while in others they persist -throughout life; and, like other points referred to, they assist us in -recognising the relations of the vertebrates to one another. - -The vertebrates are divided into the following classes:-- - - 1. _Cyclostomata_--Lampreys. - 2. _Pisces_--Fishes. - 3. _Amphibia_--Frogs, Toads, Newts, &c. - 4. _Reptilia_--Snakes, Lizards, Tortoises, &c. - 5. _Aves_--Birds. - 6. _Mammalia_--Mammals. - -The first of these includes only a few species, one of which is found in -our seas, and will receive a short notice here. The fishes will, of -course, demand a fair share of our attention. Amphibians and reptiles -have no British marine representatives, and are therefore quite excluded -from this work. As to the birds, although there are so many that live -entirely on the sea and in its immediate neighbourhood, these have been -so ably dealt with by Mr. Hudson in one of the books of this series that -it would be superfluous to mention them. The mammals include a -considerable number of marine species, but as only one of these--the -Porpoise--is really commonly observed round our coasts, it alone will be -selected for description. - -Lampreys and their few allies were formerly classified with fishes, but -are now made to form a small class by themselves; and there is abundant -reason for the separation. It will be remembered that vertebrates, in -the early stages of their development, are characterised by a -cartilaginous rod running through the dorsal region of the body, below -the central cord of the nervous system, and that they possess a series -of slits opening into the sides of the pharynx. Now, while these -characteristics are usually only transitory in the vertebrates, the -Lampreys and their relatives are the only animals in which they persist -throughout life, and it is for this reason that they are exalted to the -dignity of a class under the title _Cyclostomata_. - -This name signifies 'round-mouthed,' while the Lampreys themselves form -the still smaller division _Marsipobranchii_, which means -'pouch-gilled,' these two being among the most evident characters of the -creatures concerned. They have no true jaws, the circular mouth being -supported by a ring of cartilage, and provided with a rasp-like tongue -that enables them to divide their food. They have no true bone in their -bodies, the simple skeleton, without limbs and ribs, being entirely -cartilaginous, and the rudimentary skull is not movable on the dorsal -cartilage. Their bodies are elongated and eel-like, with a single medial -fin, supported by fine cartilaginous rays, and with seven little slits -on each side of the neck, communicating with as many gills in the form -of little pouches. The mouth is suctorial, presenting, when open, a -circular adhesive disc, by which the animals can attach themselves to -any solid object, but assumes the form of a mere slit when closed. The -young differ from the adult in a few points of structure. Thus they have -no eyes, and the long fin, divided in the adult, is continuous. With the -above characteristics in mind, there will be no danger of confusing the -lampreys with the eels and other similar fishes. - -There are three or four British lampreys, two or three of which inhabit -fresh water. Their habits do not seem to be well understood, but it -appears certain that the Sea Lamprey (_Petromyzum marinus_), which -reaches a length of from one to two feet, ascends rivers to spawn, while -the smaller River Lamprey (_P. fluviatilis_) has been caught in the sea; -and it is probable that the migrations of both, together with the -sojourn of the young of the former for a longer or shorter period in -fresh waters, have been the cause of the widespread confusion between -species. - -Lampreys are carnivorous creatures, and attach themselves to fishes by -their suctorial mouths, and rasp away the flesh. They have also been -known to attack bathers. - - [Illustration: FIG. 226.--THE SEA LAMPREY] - -Passing now to the true fishes, we must first study the general features -of the group by which they are to be distinguished from other animals. -Since there are so many creatures outside this class that are more or -less fishlike in some respects, it becomes no easy matter to give a -concise definition of a fish, and the shortest satisfactory description -must necessarily include several points of structure. Thus, we may -define a fish as a cold-blooded vertebrate that does not undergo -metamorphoses, with limbs modified into fins, possessing also median -fins on the dorsal and ventral surfaces, having distinct jaws, a heart -with two chambers, and breathing by gills. To this we may add that the -young are generally produced from eggs, and that the skin is covered -with scales or bony plates, or is naked. - -But let us now look more closely into the structure of fishes, so that -we may be enabled to see how marvellously they are adapted to their -aquatic life, and in order that we may become acquainted with the few -technical terms which will, as a matter of convenience, be used in the -descriptions of species. - -Taking first the external features, we note that the body is generally -covered with scales, sometimes very large and distinct, but often so -small and closely set that they are not visible without careful -examination; indeed they are often so small, and so thoroughly embedded -in the slimy skin as not to be discovered without the aid of a -microscope. When the scales have unbroken edges and overlap one another -they are said to be _cycloid_, but when the projecting edges are toothed -or serrated, giving a roughness to the touch, they are described as -_ctenoid_. Sometimes the scales are modified into bony plates or little -isolated bony granules, and in either case they are practically -identical in structure with teeth, consisting as they do of dentine, -capped with a little harder substance resembling enamel. - - [Illustration: FIG. 227.--THE PILCHARD - 1. Dorsal fin. 2. Pectoral fin. 3. Pelvic fin. 4. Ventral or anal - fin. 5. Caudal fin.] - -We often observe a row of scales, of a different nature from those -covering the body generally, running along each side of a fish from near -the eye to the end of the tail; and these constitute what is called the -_lateral line_. If we examine these scales closely, we observe that each -one is pierced by a hole that communicates with a little sac beneath -containing a gelatinous material, and in which a nerve tendril -terminates. The presence of the nerve filament evidently denotes that -the scales in question, with the little sacs beneath them, are organs -connected with sensation, and it is also believed that they have -something to do with the secretion of the slimy mucus that covers the -scales of the body. - -The mouth of a fish is generally situated on the extreme front of the -head, but occasionally, as in the sharks and rays, quite on the under -side. If it contains a tongue at all, this organ is of small size and -simple structure; thus it is highly probable that the sense of taste is -very feeble in these animals, and this is just what one might expect -when one remembers that fishes never retain their food in the mouth for -any length of time, but simply bolt it without any attempt at -mastication. - -The arrangement and nature of the teeth are very variable. Often they -are developed on the membrane of the mouth only, in which case they are -generally renewed as fast as they are worn down, but sometimes they are -persistent structures more or less embedded in the bone of the jaws. In -some cases teeth are altogether wanting, but in others they are situated -not only on the jaws, but also on the tongue, the roof of the mouth, and -even on the bony arches that support the gills. - -A glance at the fins of a typical fish will suffice to show that they -may be divided into two groups--the paired fins, representing the two -pairs of limbs in most of the higher animals, and the median fins -occupying the middle line of the body. The former comprise the two -_pectoral fins_ that correspond with our arms, and are attached to the -bones of the pectoral or shoulder girdle; and the _pelvic fins_, -corresponding with the lower extremities. The pectorals, too, are -present in nearly all fishes, while the pelvic pair are rather more -frequently absent than the pectorals. - -The medial fins comprise the _dorsal_, the _ventral_, and the _caudal_ -or tail-fin, and are not to be regarded as limbs, but rather mere -outgrowths of the skin. They are not directly connected with any part of -the main bony framework of the body, though they are generally jointed -with a series of bones (interspinal bones) that run between processes of -the vertebral column. The dorsal and ventral fins are often divided into -two or more parts, and the tail fin is commonly distinctly forked. - -Although the seven fins above mentioned differ considerably in general -form, some being fanlike, while others form fringe-like expansions, yet -they generally agree in that they consist of bony or cartilaginous rays, -between which is a soft membrane. The rays, however, vary much in -character, being sometimes developed into very hard and sharp spines, -and sometimes quite soft and flexible. The fins also differ in function, -as will be seen when we observe the movements of a fish as it swims. It -will then be noticed that the caudal fin, which is spread in the -vertical plane and moved sharply from side to side by the powerful -muscles of the tail, is the chief propelling organ, while the others are -concerned principally in maintaining the balance of the body. This -latter point becomes much more evident when we observe the movements of -a fish in which one or more of the fins have been injured or lost, as we -shall see presently. - -It is true that the pectoral fins are sometimes used to propel, but -forward movement is brought about almost entirely by the caudal fin, -which acts much in the same way as the blade of the propelling 'screw' -of a steam-vessel, the pectorals being used at the same time for -steering. Occasionally, too, the latter are both spread out at right -angles to the body when the fish desires to stop suddenly, and are even -employed at times in swimming backwards. - -When a fish wants to turn to one side, it will be seen to give the tail -a sharp motion to the opposite side. The pectoral of the latter side is -also brought into play, while the other is kept close against the body. - -If the pectoral or pelvic fin of one side is injured, the body of the -fish will incline to the opposite side; and if all the paired fins are -functionless the fish swims with its head inclined downwards. -Observations of fishes in which the dorsal or ventral fins are injured -will also show that these organs are necessary to maintain a steady -motion in the water. - -In addition to the above facts, it may be mentioned here that the paired -fins are often modified into long finger-like processes that serve as -organs of touch, and even as means by which the fish can creep along the -bottom. This is notably the case with gurnards and a few of the other -fishes that spend their time almost exclusively on the bed of the sea. - -Fishes are essentially gill-breathers, the gills being generally -fringe-like organs, supported on bony arches (the gill arches), -numbering four on each side, the cavity containing them being covered by -a gill-cover (_operculum_) that opens behind. Water is taken in at the -mouth, whence it passes into the gill-chamber; and after passing between -and around the gills, it escapes under the opercula. The gills -themselves are richly supplied with bloodvessels that are distributed -close to the surface, and an exchange of gases takes place through their -exceedingly thin walls, carbonic acid gas passing from the blood to the -surrounding water, and oxygen, held in solution in the water, passing -from the water to the blood. - -When fishes are in foul water, containing but little oxygen in solution, -they rise to the surface in order to make up the deficiency by taking -oxygen direct from the air. This, however, is an unnatural proceeding -with the majority of fishes; but there are some that are provided with -accessory breathing organs specially adapted to the extraction of oxygen -direct from the air, and these are so dependent on the supply from this -source that they are suffocated if prevented from reaching the surface. - -In other fishes, such as the sharks and rays, the gills are of an -entirely different character from those described above, for they are -pouch-like and five in number on each side, each pouch communicating -with the pharynx as well as with the exterior by a slit-like opening. - -Before leaving the external characters of fishes we must say a word or -two about their forms and colours. As regards the former, it is well -known that fishes are well adapted for rapid progression through water, -but there are many exceptions to this rule. These exceptions, however, -apply principally to those species that have no need to swim rapidly, -and a study of their habits will show that their form is just as -perfectly adapted to their mode of life. They are often species that -live on the bottom, or hide in the crevices and holes of rocks, and -examples will be given in our future descriptions. - -Variations in colour are even more interesting, especially as they are -so commonly connected with the nature of the surroundings and the -protection of the animals. In nearly all cases the colour is darker on -the upper surface than on the lower, thus making it appear that the -influence of light has something to do with the formation of the -pigments of the skin, and experiment proves that this is, at least to a -certain extent, the case; for when fishes have been kept for some time -in an aquarium into which light is admitted through the bottom only, -pigment spots have formed in the skin on the lower surface. - -Fishes that swim at the surface are generally tinted on the dorsal side -with some shade that closely resembles the colour of the water as viewed -from above, and are white and silvery below. Such colouring is of course -highly protective, for they are not readily distinguished by the sea -birds and other enemies that would pounce on them from above, and are -almost invisible against the sky to eyes below. This form of protective -resemblance is beautifully illustrated in the mackerel, which is barred -on the back with black and green, closely imitating the ripples on the -surface of the deep green sea, while the under side is of a silvery -whiteness that is hardly visible from below with the bright sky as a -background. - -The flat fish afford other interesting examples, for these live on the -bottom, and are coloured above so as to resemble the bed on which they -live; the tints being those of mud, sand, or gravel. - -But what are we to say of the gaudy colours of the gurnards, rock -fishes, &c.? These are certainly not protective in all cases, for we -sometimes find brightly coloured species conspicuous among duller -surroundings. Such instances, however, are comparatively rare, the gaudy -species living principally among the variously coloured rocks, weeds, -and corals; and when they do occur it is probable that they serve -principally as a means by which the brightly coloured sex--usually the -male--attracts its mate. We say 'usually the male,' but why so? Because -the female requires the protection of a more sombre colour in order that -she may with safety deposit her spawn for the perpetuation of her -species. Again, the male referred to needs the assistance of his gaudy -coat only during the breeding season, hence we find that he assumes the -bright colours as a wedding garment, to be cast off when the breeding -season is over. - -This leads us to the subject of changeability of colours in the same -individual. That such changes do occur is well known, and it is still -more remarkable that they are produced in rapid succession, apparently -at the will of the fish concerned; for its tints will vary as it moves -from place to place so as to always harmonise with the surroundings, and -also in response to other conditions. The mechanism by which such -variations are produced has also been studied and explained:--The -colouring matter is held in little vesicles beneath the skin, and these -vesicles are capable of being compressed by muscles quite under the -control of the fish. When they are globular in form the contained -pigment appears dark, but when they are flattened by muscular -compression, the pigment is spread over a much larger area, and thus -greatly reduced in depth of tint. - -As with all vertebrates, the central axis of the internal skeleton of a -fish consists of the backbone and the skull. The structure of the latter -is so complicated, and its description so full of technicalities, that -we deem it advisable to pass it over in a work like this where the scope -is so large in proportion to the space available; and this we do with -reluctance, because the detailed study of the skull is of real -importance to those who would thoroughly understand the principles of -classification. - -The backbone consists of a variable number of cylindrical vertebrae, -united end to end to form a continuous column, both the anterior and -posterior faces of each being concave. On the dorsal surface of each -vertebra there is a V-shaped arch, surmounted by a spine, the former -serving to protect the spinal cord, and the latter giving attachment to -the muscles of the back. Some of the vertebrae are also provided with -processes for the attachment of the ribs, and those of the tail possess -an arch and a spine on the ventral as well as on the dorsal side. - -It has already been shown that the pectoral fins are jointed to a -girdle. This girdle corresponds with the shoulder-blade of higher -animals, and gives direct attachment to the rays of the fin, which may -be regarded as the equivalent of the fingers, and thus there is no part -of the limb corresponding with the arm. The pelvic fins also are -frequently jointed to a pelvic girdle or hip, but this is a very -rudimental structure, or is even entirely absent in some species. - -The rays of the caudal fin articulate with the extremity of the -backbone, but this portion of the fish's anatomy undergoes such -remarkable changes that we must devote a few words to it. It is probably -well known to our readers that the tails of fishes exhibit three -distinct forms. The first of these is a simple fringe formed by the -union of unaltered dorsal and ventral fins; the second is the -unsymmetrical or unequally lobed tail so characteristic of sharks, -dogfishes, and rays; and the third is the broad symmetrical tail fin, -often distinctly forked or bi-lobed, such as we meet with in the -majority of our bony fishes. These three kinds are known respectively as -the _diphycercal_, _heterocercal_, and the _homocercal_ tails. - - [Illustration: FIG. 228.--THE SKELETON OF A FISH (PERCH) - _d_, dorsal fin; _p_, pectoral fin; _v_, pelvic fin; _t_, tail fin; - _a_, anal fin] - -Now, it is an interesting fact that the most ancient fishes of our globe -possessed tails of the first type; and that these gradually gave place -to the heterocercal form; while the higher fishes of the present day -nearly all possess the homocercal tail. Thus as time advanced the -heterocercal tail was gradually evolved from the diphycercal, and the -homocercal from the heterocercal. - -Further, if we watch the development of one of the highest fishes of the -present day from its embryo, we find that similar changes take place in -the individual. At first its tail is a simple fringe round the extremity -of the backbone, the latter being straight, or nearly so, to the end, so -that the embryo fish, as yet still in the egg, reflects a characteristic -of its very early ancestors. Then the end of the vertebral column turns -upward, and strong fin-rays are developed on its ventral side, so that -the tail becomes a heterocercal one like that of the less remote -ancestors of a later geological period. Next, the upward-bending portion -of the vertebral column is slowly absorbed, till nothing of it remains -except a small upturned bony spine, while, at the same time, the ventral -lobe expands on the upper side until the tail fin is once more of a -symmetrical form. - - [Illustration: FIG. 229.--THE INTERNAL ORGANS OF THE HERRING - _a_, oesophagus; _bc_, stomach; _e_, intestine; _l_, duct of - swimming bladder; _k_, air-bladder; _h_, ovary] - -Following these interesting changes, it becomes evident that the -symmetry of the tail fin of the bony fishes is really a false one, the -whole of it having been formed from the ventral lobe of a heterocercal -tail; and although the backbone seems to terminate abruptly exactly -opposite the middle of the fin, it still contains the remnant of the -raised extremity of the backbone that ran to the tip of the dorsal lobe -when the tail was of the heterocercal type. - -The flesh or muscle of fishes is usually white, but it often assumes a -pink colour in the case of those fishes that feed largely on -crustaceans. This is due to the presence of a substance in the horny or -calcareous skins of the crustaceans that is turned red by the action of -the digestive fluids--the same substance that is turned red when the -crustaceans are boiled. This is notably the case with the salmon; but -the red pigment thus derived originally from the crustaceans frequently -shows itself more in the skin of the fish than in the flesh, as -observed in the common red gurnard. - -Most fishes possess a membranous bag containing air, situated just below -the backbone, and known as the air-bladder; but this organ does not -exist in sharks and rays and in some of the heavier bony fishes that -live on the bottom. The air-bladder is capable of being compressed by -the action of certain muscles, and its principal use seems to be the -adjustment of the specific gravity of the fish to that of the -surrounding water; but it is interesting to note that the development of -this air-bladder is precisely the same as that of the lungs of -air-breathing animals, and that in some fishes which live in foul muddy -waters it is really a functional lung by means of which the fishes can -breathe direct from the atmosphere. - -We can find space to refer only to one other internal structure of the -fish, namely, the roe of the female. This usually consists of a very -large number of eggs of small size, sometimes numbering many thousands, -and even millions, in a single individual. So numerous, indeed, are the -eggs, that were it not for the multitudes of carnivorous animals that -devour both eggs and fry, the sea and fresh-water lakes and rivers would -soon become so thickly populated that the fish would die in millions for -lack of food and air. - -In some cases, however, the eggs are much larger and fewer in number, -but these are generally protected from the ravages of predaceous species -by a hard covering, as we shall observe in the sharks and rays. - -Finally, a word or two must be said about the distribution of fishes. We -have already referred briefly to species that live principally at the -surface, and others that make the bottom their home: but some of the -former go to the bottom for food or to deposit their spawn, while some -of the latter occasionally rise to the surface and swim in shoals. We -have noticed, too, that the paired fins of bottom fishes are sometimes -modified into feelers, or into fingerlike processes adapted for -creeping. Similar organs, employed undoubtedly as organs of touch, and -called barbels or barbules, are often developed on the chins or jaws of -these fishes. - -Although we have to deal principally with the species that belong more -or less to the shore--the _littoral_ fishes--we should like to refer -briefly to one or two interesting features of those that live at great -depths. It will be readily understood that much light is lost as the -rays penetrate into deep water, so that the bottoms of deep seas must -be more or less darkened. To allow for this loss, we find that the -species living at moderate depths are provided with larger eyes to -enable them to see their prey and their mates; but at still greater -depths, where the sun's light cannot penetrate, the fishes are either -blind, or are possessed of luminous organs which enable them to see -their way. Again, as the sea is so thinly populated at such great -depths, the carnivorous species do not find abundant food always at -hand, hence they are often provided with such mouths and stomachs as -will allow them to make the best of favourable opportunities, some being -capable of swallowing a fish quite as large as themselves. - -We often find fishes roughly classified into fresh-water and salt-water -species, and although such a division is at times convenient, it must be -remembered that some of the former migrate into brackish and even into -salt water, while some of the latter ascend estuaries and rivers either -for the purpose of obtaining suitable food, or for the deposition of -their eggs. - -The fishes that frequent our coasts may be classified into two main -groups, those with cartilaginous skeletons (_Elasmobranchii_), and the -bony fishes (_Teleostomi_). Both these are divided into family groups, -and we shall deal more or less briefly with all the important families -that include common British marine fishes, but giving more attention to -those species that are truly littoral in habit--species that may be -found in the rock pools or under stones at low tide, and which may be -obtained by the amateur angler working from rocks, piers, &c. - -The cartilaginous fishes include the Sharks, Dogfishes, and Rays. They -have pouchlike gills, five or more on each side, each one opening to the -exterior by a separate slit. The skin generally contains bony elements -that are toothlike in structure and often in form; the mouth is usually -on the under side of the head, and the tail is nearly always of the -heterocercal kind. They are all carnivorous creatures, and often -exceedingly voracious; and are represented in our seas by the Rays and -Dogfishes. - -Rays or Skates (family _Raiidae_), of which there are six or seven -British species, are readily known by their broad flattened rhomboidal -bodies, with the mouth on the under side of the head, a longitudinal -fold on each side of the tail, and pectoral fins extending quite or -nearly to the front point of the head. - -Two of these fishes are very common in our markets, one being the -Thornback Skate (_Raia clavata_), distinguished by the clawlike spines -down the middle of the back as well as on other parts of the body; and -the Common Skate (_R. vulgaris_), a very voracious species, from two to -four feet long, with a very sharp muzzle. - -All the members of this family are bottom fish, without air-bladders; -and their eggs, which are large and detached, are enclosed in horn -capsules which are so commonly washed up on the beach that they are well -known to frequenters of the sea-side, who call them Skates' Barrows or -Shepherds' Purses. These cases are oblong in form, with a process at -each corner, and the material of which they are composed looks very much -like that of some of the coarser sea weeds after they have been dried in -the sun. As a rule only the empty cases are cast ashore by the waves, -open at the end where the little skate made its escape; but occasionally -we meet with the complete egg, and the case, while still wet, is -sometimes sufficiently transparent to show the form of the embryo -within. - - [Illustration: FIG. 230.--THE EGG-CASE OF DOGFISH] - -Dogfishes are also fairly well known to sea-side ramblers, for not only -are some species used as food in many places, but they are also -frequently to be seen cast aside with the refuse from the fishermen's -nets. The common Spiny Dogfish (_Acanthias vulgaris_), belonging to the -family _Spinacidae_, frequents all parts of our coasts. It reaches a -length of three or four feet, and is of a slate-blue colour above and -very pale yellow below. The pectoral fins are very large, the ventral -fin absent, and there is a very sharp spine in front of each dorsal. The -creature is ovo-viviparous; that is, the eggs are hatched while still -within the body of the parent. - -Another family (_Scylliidae_) contains two British species without -spines, and is also characterised by having the first dorsal fin far -behind. They are the Larger Spotted Dogfish (_Scyllium canicula_) also -known as the Nurse Dog and the Bull Huss; and the Lesser Spotted -Dogfish (_S. catulus_), called also the Huss and the Rough Hound. The -egg capsules of both these are occasionally washed on the beach, and -those of the latter species may be known by the yellowish colour and the -long tendrils by which they are anchored to sea weeds. - -In addition to these we may briefly refer to two of the Blue Sharks -(family _Carchariidae_) that frequent our shores, distinguished by their -long and prominent muzzle, and the crescent-shaped mouth. They may be -regarded as higher in the scale of fish life, as compared with the -sharks and rays previously named, because the vertebrae are more or less -hardened by the deposit of calcareous matter, and, therefore, make a -nearer approach to the character of true bone. The species referred to -are the Common Blue Shark (_Carcharius glaucus_), and the Smooth Hound -(_Mustelus laevis_). The former often exceeds twelve feet in length, and -is commonly seen off our south and west coasts during the summer months. -It is a nocturnal marauder, and is said to sleep at the surface by day -with its tail exposed above the water. The Smooth Hound is a bottom -feeder, subsisting on molluscs and crustaceans, the shells of which are -easily crushed by its flat and blunt teeth. It is a small shark, -measuring only three or four feet in length, and brings forth its young -alive. - - [Illustration: FIG. 231.--THE SMOOTH HOUND] - -The next division (_Teleostomi_) contains all the bony fishes, which may -be distinguished generally from the cartilaginous group by the following -features:--The skeleton is more or less hardened by the deposit of -calcareous matter, and the tail is generally not of the heterocercal -type. The paired fins are fan-like, and the pectoral girdle is attached -to the hinder part of the skull. These fishes generally have an -air-bladder, and the gills lie close together in a cavity covered by an -operculum. The eggs, too, are generally very small and numerous, and -massed together. - -Of these we will take first the family _Salmonidae_, of which the Salmon -(_Salmo salar_), and the Smelt (_Osmerus eperlanus_) are well-known -examples. Several species of the family are remarkable for their -periodical migrations from fresh to salt water or _vice versa_, and we -cannot do better than briefly relate the interesting life-history of the -salmon as a striking instance of these peculiar wanderings. This fish -quits the sea at the close of the summer, and ascends the rivers for the -purpose of depositing its spawn, the colder water of the rivers being -necessary for the development of the young. Its upward journey is beset -with many difficulties, for it has to shoot the various rapids and leap -the cascades, the latter often demanding the most prodigious efforts on -the part of the fish, which frequently leaps several feet out of the -water, and even then has sometimes to renew its attempts over and over -again before it finally succeeds. Indeed, the difficulties to be -overcome are so numerous that the fish often reaches the goal in such an -exhausted condition that it would hardly be recognised as the salmon by -those who have only seen it in the prime condition in which it is -captured during its return to the sea in the following spring or summer. -The male, at this period called the _kipper_, is of a dull red colour, -irregularly blotched with yellow and light brown, and its skin is -covered with a slimy secretion. Its body is lean, and the head, now -large and out of all proportion, is rendered still more unsightly by the -protrusion of the lower jaw, which at this season, when the males are -particularly pugnacious, becomes a formidable weapon of offence. The -condition of the female, now called the _baggit_, is equally poor, and -the skin has changed its bright silvery colour for dark and dingy -shades. - -The female digs a nest in the form of a deep trench by wriggling her -body in the gravel of the bed of the stream, and there deposits her -eggs, many thousands in number, small quantities at a time. As each -batch is deposited the eggs are fecundated by the kipper, and then -covered over lightly with gravel by the baggit; and this work having -been accomplished, both male and female rest and feed, with the result -that their condition is rapidly improved. - -After about eighteen weeks the eggs begin to hatch, and the fry wriggle -out of the nest and seek shelter under stones in the immediate -neighbourhood. They are now peculiar little creatures, as much like -tadpoles as fishes, with big heads and narrow bodies, and a bag of -albuminous yolk-matter attached to the ventral side. The young subsist -on this store of food for from twelve to twenty days, during the whole -of which time they remain under shelter, having, of course, no need to -expose themselves to the numerous enemies with which they are -surrounded, and they then leave their hiding-place in search of food, -being now about an inch in length. They feed on aquatic and other -insects, which are now becoming plentiful on the approach of the warm -weather; and, growing rapidly, reach a length of four inches in a month -or two. They are now called _parr_, and are distinguished by the dark -bars that cross their bodies transversely--a feature that persists for a -year or more from this time. - -Towards the end of May the parr migrate seawards, accompanied by the -adult salmon, but as their enemies include the voracious fishes, wading -birds, and even the adults of their own species, it is probable that -only a small proportion of the original number ever enter salt water. - -In the sea they feed on crustaceans, molluscs, and small fishes, the -young still growing rapidly, and attaining a weight of about five pounds -in the following autumn, when both young (now called _grilse_) and old -again ascend the rivers to spend the colder half of the year; the former -will have reached a weight of ten pounds or more on their return to the -sea in the following year. - -The Smelt may be seen in thousands in our estuaries during the spring, -for at that time they come up to spawn in the brackish water. In the -summer they swim about in shoals along the coast, and are caught largely -in nets for the market. In some parts they are taken in large shallow -circular nets suspended on a line. This is lowered into the water, and -hauled up when the fish are seen swimming above it. Many amateurs secure -numbers of smelt by means of rod and line, fishing from piers, jetties, -&c. They bite freely at almost any kind of bait, and will snap at an -almost bare hook, with the tiniest fragment of the bait at its point. - -The Herring family (_Clupeidae_) contains some well-known food-fishes to -which we need only casually refer. They are mostly littoral species, -none inhabiting deep water, and none straying into the open ocean. Their -bodies are covered with silvery scales, and are laterally compressed, so -much so on the ventral side that there is a moderately sharp ridge along -the middle line. The principal fishes of the family are the Herring -(_Clupea harengus_), the Sprat (_C. sprattus_), and the Pilchard (_C. -pilchardus_). - -These fishes are particularly interesting on account of their gregarious -habits and the enormous size of the shoals they form, a single shoal -often containing millions of individuals; and they are often captured in -such quantities that large numbers are sold to farmers as manure to -enrich the soil. The shoals are followed closely by many larger -carnivorous species that devour them in great numbers, as well as by -flocks of sea birds that prey on them, and yet their numbers are not -appreciably reduced by such ravages. They spawn in shallow waters near -the coast, and feed principally on the crustaceans and worms of the -littoral zone. - -Sprats were once considered to be the young of the Herring, but it is -now universally acknowledged that they are a distinct species, and quite -a number of characteristics have been given as a means of distinguishing -between the two. The young of the herring are, however, used largely as -food, for that miscellaneous mixture of fry and small species known as -Whitebait consists largely of these and the young of the sprat. - - [Illustration: FIG. 232.--THE COMMON EEL] - -Herrings are captured principally off the north and east coasts, but the -pilchards, which are often confused with them, and even at times sold -under the same name, are caught chiefly off the coast of Cornwall. - -Although the Eels (_Anguillidae_) are so readily distinguished by their -general form and appearance, yet it may be advisable to call attention -to one or two of the leading characters that would possibly be -overlooked by an ordinary observer, and in doing this we ask the reader -to note that our remarks apply to the true eels only, and not to the -sand eels and other fish that may be confused with them. - -The elongated bodies of the _Anguillidae_ are covered with a slimy skin -that is apparently scaleless, but an examination with the microscope -will show that there are small scales embedded in it. The dorsal and -ventral fins extend to the tail, and the pelvics are absent; the -gill-slits, which are very narrow, are at the base of the pectorals. - -It might well be expected that eels would be possessed of some form of -accessory breathing apparatus, seeing that they can live so long out of -water, but this is not the case. They have, however, a pouch-like -gill-cavity which can be inflated and filled with water by the fish, -thus keeping the gills moist and functional. In most other fishes the -gill-chamber is not capable of holding water, and thus the gills soon -become dry and sticky, so that they adhere together and fail to absorb -the necessary oxygen when the fish is out of water. - -Thus the Eel (_Anguilla vulgaris_), in the remarkable migrations for -which it is noted, is capable of travelling over dry land for -considerable distances in search of suitable homes. - -If an eel be taken out of the water, these gill-pouches will be seen to -swell out almost immediately, and remain filled with water as long as -the fish is kept on land; but when it is returned to its natural -element, it will at once discharge the water that kept its gills moist, -and which has become foul with the products of respiration, and, with a -few vigorous gulps, renew the supply. - -Eels spend their breeding season, which extends from July to September, -in salt or brackish waters; and early in the following summer, the -young, which are now called _elvers_, and measure from three to five -inches in length, ascend the rivers, travelling enormous distances and -overcoming obstacles that we might well expect to be insurmountable. -Thus they perform two migrations annually, though it is thought by some -observers that the adult never returns to the sea, but dies soon after -it has deposited its spawn. - -The family of Flat-fishes (_Pleuronectidae_) present many interesting -points of structure and habit in which they stand alone, the variations -in structure as compared with other fishes being due, of course, to the -habits which they have acquired. - -One of the first features that strike the observer on looking at a -flat-fish is the unsymmetrical form of the body. It is very much -compressed, and the fish having acquired the habit of lying on the bed -of the sea, sometimes on the left and sometimes on the right side, the -lower surface has become flattened more, and is of an almost pure white -colour, while the upper convex side is more or less coloured with -pigment produced by exposure to light. The dorsal and ventral fins are -both very long; and, as is usual with bottom fishes, the swimming or air -bladder is absent. - -Young flat-fish are at first perfectly symmetrical in form, with one eye -on each side of the head, and they swim freely in the water with their -bodies in a vertical plane; but they very soon acquire the habit of -swimming on one side, and the eye of that side slowly passes round to -the other side of the skull, rotating in its orbit as it moves, till at -last both are on the uppermost surface. This, of course, is accompanied -by a considerable distortion of the bones of the skull, which is very -evident in the skeleton of the adult. The young fish then takes to the -bottom, with the result that its under-surface is flattened, while the -upper becomes strongly pigmented. - -These fish spend almost the whole of their time on the bottom, only -occasionally rising for short intervals, when they swim by undulatory -movements of their bodies and fins; their food consists of crustaceans, -worms, and other small marine animals. - -They furnish very interesting illustrations of protective colouring, the -upper surface always closely resembling the ground on which they rest -and feed; and thus they are not only protected from their own enemies, -but are enabled to lie unseen by the animals that form their prey. Those -which live on sandy shores are finely spotted with colours that closely -imitate the sand, while those that lie on mud are of dark and dingy -hues. Others, again, are irregularly marked with spots of various sizes -and colours that resemble a gravelly bottom; and most species are still -further protected by their habit of throwing sand or mud on the top of -their bodies by means of their dorsal and ventral fins. - -Small flat-fishes, especially young Plaice and Flounders, live so close -to the shore that they are often left behind in rock pools and sandy -hollows by the receding tide, and it is very interesting to observe the -habits of these in their natural conditions. It will generally be -noticed that it is most difficult to detect them while they are at rest; -and when disturbed, they usually swim but a short distance, settling -down very abruptly, and immediately throwing a little sand over their -bodies by a few vibrations of their fins. - -Another peculiarity of some of the flat-fishes is their indifference to -the nature of the water in which they live. Flounders may not only be -caught in the estuaries of our rivers, but they even ascend to, and -apparently live perpetually in, perfectly fresh water. In many -instances they may be seen miles from the sea, and even flourishing in -little fresh-water streams only a few feet in width. Thus they may be -found in numbers in the upper waters of the small rivers of the Isle of -Wight and of many streams of the mainland. - -The principal British flat-fishes are the Plaice (_Pleuronectes -platessa_) and Flounder (_P. flexus_) above mentioned, and also the Sole -(_Solea vulgaris_), the Lemon Sole (_S. aurantiaca_), the Turbot -(_Rhombus maximus_), and the Halibut (_Hippoglossus vulgaris_); and as -all these are well-known food-fishes it is hardly necessary to describe -them. - - [Illustration: FIG. 233.--THE LESSER SAND EEL] - -Sand Eels (family _Ophidiidae_) resemble the true eels in the general -form of their elongated bodies, but may be readily distinguished by -their bright silvery colour, the large gill-openings, and the more -strongly developed dorsal and ventral fins, the former of which extends -almost along the whole length of the back. The lower jaw is also longer -than the upper. - -Two species are to be found on our shores--the Lesser Sand Eel -(_Ammodytes tobianus_), and the Greater Sand Eel (_A. lanceolatus_), the -former attaining a length of six or seven inches, and the latter nearly -three times this size. They may be seen off the south coast, swimming in -shoals over sandy bottoms, and when disturbed they descend and burrow -into the sand with remarkable agility. They approach the shore so -closely that they are often washed up by the waves, but immediately -disappear into the sand; and large numbers commonly remain behind as -the tide recedes, burying themselves to the depth of a few inches, and -are dug out by fishermen for bait. - -The smaller species is by far the more common, and is taken in large -numbers by means of the draw net to be sold as food. It is particularly -abundant at Teignmouth, where it is known as the Sand Sprat, and forms -an important article of diet. - -Quite a number of our important food-fishes belong to the Cod family -(_Gadiadae_), and although some of these are caught almost entirely in -deep water some distance from shore, others give employment to the -angler fishing from rocks, piers, and jetties. - -In all, the gill-openings are very wide, and the body is covered with -small overlapping scales. The caudal fin is quite free, the dorsal is -generally divided into three distinct parts which extend over the -greater part of the back, and the ventral fin is also frequently -divided. - - [Illustration: FIG. 234.--THE THREE-BEARDED ROCKLING] - -The typical species--the Cod (_Gadus morrhua_)--is too well known to -need a description, and although it is a large fish, often measuring -four feet and more, it approaches so close to the shore that it may be -caught with a hand line thrown out from rocks or piers. The barbel -projecting from the chin denotes that it is a bottom feeder. - -On the rocky coast of the south the Pollack or Pollock (_G. pollachius_) -is very abundant, and may be taken with rod and line from the shore. It -also enters estuaries in large numbers, and may be caught close to quays -and jetties. This species is a very free biter, and will take almost any -of the baits used for sea fishing. It has no barbel. - -The same genus includes the Whiting (_G. merlangus_), distinguished by a -black spot at the base of the pectoral fin and the absence of barbels; -the Whiting Pout (_G. luscus_), with a similar black spot at the base of -the pectorals, also dark, transverse bands, and a barbel; and the -Haddock (_G. aeglefinus_), with a black patch on either side above the -pectorals, and a dark lateral line. The family also includes the Ling -(_Molva vulgaris_) and the Hake (_Merluccius vulgaris_), both of which -are caught in deep water; and the Rocklings (genus _Motella_), three -species of which frequent our rocky shores. - - [Illustration: FIG. 235.--THE SNAKE PIPE-FISH] - -The last mentioned are interesting little fishes that may be found on -stony beaches at low tide, for they often remain under cover between the -tide-marks, and may be seen on turning over stones and weeds. Perhaps -the commonest of them is the Five-bearded Rockling (_M. mustela_), which -has four barbels on the upper lip and one on the lower. It is of a -dark-brown colour above, and light below, and makes nests of corallines -in rock cavities. The Three-bearded Rockling (_M. tricirrhata_), known -also as the Sea Loach and the Whistle-fish, is a larger species, -sometimes reaching a length of a foot or more. Its colour is light -brown, marked with darker spots, and, like the other species, it lives -in the shallow water of rocky and weedy places. Another species--the -Four-bearded Rockling (_M. cimbria_), known by the three barbels on the -upper lip and one on the lower, is about eight inches long when full -grown, and is found principally on the northern shores. - -Our next family (_Syngnathidae_) contains some peculiar creatures called -Pipe-fishes because their jaws are united into a tube. They have long -and slender bodies that are covered with bony plates which form a kind -of coat of mail and give them an angular form. They have very small -gill-openings, a single dorsal fin, and no pelvics. - -Pipe-fishes are very sluggish in habit, swimming but little, and living -in the shelter of weeds and stones on rocky coasts. In fact, they are -not adapted for swimming, and their attempts at this mode of locomotion -are awkward in the extreme, for their bodies are rigid and the tail very -small. When removed from their hiding-places they move but little, and -look as much like pieces of brown or greenish wood as fishes; and their -rigid bodies are so completely encased in the bony plates that they -alter but little in appearance when dried, and consequently the dried -specimens are often seen in museum collections. - -All the British species, four in number, are small fishes, inhabiting -the shallow water of rocky shores, and are often found hiding under -stones near low-water mark. The largest is the great Pipe-fish or -Needle-fish (_Syngnathus acus_), which grows to a length of about -fifteen inches; and the smallest is the Worm Pipe-fish (_S. -lumbriciformis_), which is of an olive-green colour, and has a short, -upturned snout. The Lesser Pipe-fish (_S. typhle_), also known as the -Deep-nosed Pipe-fish, is very abundant on nearly all rocky coasts, and -may be distinguished from the others by having the ridge on the tail -continuous with the lateral line and not with the dorsal angle. The -other species is the Slender-nosed Pipe-fish or Snake Pipe-fish -(_Nerophis ophidium_), the body of which is extremely slender, and the -tail long and narrow. The male is provided with a series of small, -cup-like cells, in each of which he carries an egg. - -In all the bony fishes previously mentioned the fin rays are soft and -flexible, and in this respect they differ from those that are to follow, -for the remaining families are all characterised by the presence of one -or more sharp rigid spines on the dorsal fin, and often by similar -spines on other fins. They constitute the group of Spiny-finned fishes. - -Of these we shall first take the prettily coloured Wrasses (family -_Labridae_), which live in the holes of rocks and under the cover of -weeds on rugged coasts. These fishes are very voracious in habit, and -the sea angler will find that they are ready to seize almost any bait -that may be offered them, and even to attack almost everything that -moves within sight; but they are likely to give much trouble since they -will rush into the crevices of rocks or among large weeds when hooked, -and thus frequently lead to the breaking of the line. - -Wrasses feed principally on molluscs and crustaceans, and are provided -with extensile telescopic lips that enable them to pull the former from -the rocks on which they creep, and the latter from their hiding-places -among the rocks. They have also strong teeth in the gullet, by which -they can crush the shells of their prey. - -There are several British species of Wrasses, one of which is shown in -the accompanying illustration. The commoner ones are known to fishermen -and juvenile anglers by quite a variety of local names. - - [Illustration: FIG. 236.--THE RAINBOW WRASS (_Labrus julis_)] - -The family _Gobioesocidae_ contains some small and very prettily coloured -fishes of very peculiar habits, known popularly as Sucker-fishes. They -have one or two adhesive suckers between the pelvic fins by which they -attach themselves to rocks, stones, and shells. Some are littoral -species, and may be searched for at low tide; but others inhabit deeper -water, and are seldom obtained without a dredge. - - [Illustration: FIG. 237.--THE CORNISH SUCKER] - -One of the former is the Cornish Sucker (_Lepadogaster cornubiensis_), -which may sometimes be taken in a hand net by scraping the rocks and -weeds at low tide on the south-west coast. It has two suckers, each -circular in form, surrounded by a firm margin, within which is a soft -retractile centre. This central portion is attached to muscles by which -it can be withdrawn; and a vacuum is thus produced, so that the sucker -adheres by atmospheric pressure. The structure of the sucking organs can -be seen to perfection when the fish attaches itself to the side of a -glass aquarium, and if it be taken in the hand it will cling quite -firmly to the skin. - -This peculiar little fish is only about three inches long, and its broad -head is marked with two conspicuous purple spots, with a blue dot in the -centre, and surrounded by a yellowish ring. - -The allied species include the very small Two-spotted Sucker (_L. -bimaculatus_), which is of a bright red colour, and adheres to stones -and shells in deep water; the Sea Snail (_Cyclopterus liparis_), about -four or five inches long, with a soft and slimy semi-transparent body; -and Montagu's sucker (_C. Montagui_), which is usually under three -inches in length, and may be distinguished by its peculiar habit of -curling the body laterally when at rest. - -Equally interesting are the little Sticklebacks (family _Gastrosteidae_), -the fresh-water representatives of which are known to almost everyone. -Their pugnacious habits, the bright colours assumed during the breeding -season, and the wonderful nests which they build for the protection of -their eggs and young, have all served to make them popular with those -who take interest in the forms and ways of animals. They are, moreover, -such hardy creatures that they may be kept alive for a considerable time -in any well-managed aquarium. - - [Illustration: FIG. 238.--THE FIFTEEN-SPINED STICKLEBACK AND NEST] - -In this family the hindmost portion of the dorsal fin is soft-rayed, but -the front portion is represented by a row of strong, sharp, erectile -spines, which constitute a formidable weapon of offence and defence. -Most of the species live in fresh water, but all the members of the -family seem to be able to live almost equally well in both salt and -fresh water. - -We have one marine species--the Sea Stickleback or Fifteen-spined -Stickleback (_Gastrosteus spinachia_), which may be caught on rocky and -weedy coasts. It derives one of its popular names from the presence of -fifteen spines along the middle of the back. Its tail is long and -narrow, and its snout elongated, with the under jaw projecting beyond -the upper. - -The nest of this species is a pear-shaped mass of soft sea weeds and -corallines, all bound together by a silky secretion, and suspended to -the rock in a sheltered spot. Within this the female deposits her eggs -in little clusters, all of which are bound together and to the nest -itself by the silk. If the nest is damaged while occupied, it is -immediately repaired, the male, it is said, taking upon himself the -responsibility of this task. - -Sand Smelts (family _Atherinidae_) resemble the true smelts previously -described, but may be readily distinguished by the anterior dorsal fin, -which is small and spinous. We have two species of this family, of which -_Atherina presbyter_ is by far the more common. It is a very pretty -fish, about five inches long, with a broad silvery stripe along each -side. It is very common on the sandy coasts of the south, where it also -enters the brackish waters of estuaries. Young anglers catch them in -considerable numbers by means of rod and line; but the professional -fisherman, taking advantage of the fact that sand smelts swim in shoals, -captures them in large, round, shallow nets. The net is baited with -bread, crushed mussels, or offal of almost any kind, and is then lowered -several feet below the surface by means of a long pole, to the end of -which it is suspended. It is raised to the surface at short intervals, -and will often enclose dozens of fish in a single haul. - -The shallow waters of our southern coasts, including the estuaries and -harbours, are also frequented by the Grey Mullet (_Mugil capito_), of -the family _Mugilidae_. This fish may be distinguished from other similar -species by the four stiff spines of the front dorsal fin, and by the -absence of a lateral line. The mouth is small, and without teeth, and -the mode of feeding is somewhat peculiar. The food consists of worms, -molluscs, and various organic matter contained in the sand or mud of the -bottom. It is sucked into the mouth, together with more or less of the -mud and sand, and the former is strained through a special straining -apparatus situated in the pharynx. - -The Grey Mullet may be taken with rod and line, and bites freely when -the rag-worm is employed as bait. It is often taken in the fisherman's -drag net; but, being a splendid jumper, it frequently makes its escape -as the net is drawn on the beach. - -Few of our littoral fishes are so well known as the Little Blennies -(family _Blenniidae_), which are to be found hiding amongst the weeds in -almost every rock pool, and under stones as they await the return of -the tide. Their bodies are generally cylindrical, and are either naked -or covered with very minute scales. The dorsal fin runs along the whole -length of the back, and each pelvic has one spine and two soft rays. -When taken out of the water the gill-cavities widen considerably, and -the eyeballs will be seen to move independently of each other, like -those of the chamaeleon. - -Most of the blennies are very active and voracious fishes, often giving -considerable trouble to the angler when fishing with a rod among the -rocks. They will bite at almost anything that moves, and, completely -swallowing the angler's hook, will immediately rush into a crevice from -which it is often difficult to remove them. - -Most of them have tentacles on the head by which they assist their -movements among the rocks and stones; and some actually creep up the -rugged surfaces of rocks by means of their ventral fins. They can all -live for a long time out of the water, being able to retain a supply of -water in their expanded gill-chambers to keep the gills moist. - - [Illustration: FIG. 239.--THE SMOOTH BLENNY] - -The Smooth Blenny or Shanny (_Blennius pholis_) is one of the commonest -species. It reaches a length of four or five inches, and has no -tentacles on the head. The Eyed Blenny or Butterfly Blenny (_B. -ocellatus_) may be distinguished by the conspicuous spot on the spinous -portion of the dorsal fin. The Large Blenny (_B. gattorugine_) inhabits -deeper water, chiefly off the south-west coast, and reaches a length of -a foot or more. The Crested Blenny (_B. cristatus_) is named from the -small crest on the head which can be raised and depressed; and the -Viviparous Blenny (_Zoarces viviparus_), as its name implies, brings -forth its young alive. The last species often exceeds a foot in length, -and is found principally on the north and east coasts. The newly-born -young are so transparent that the circulation of the blood within the -body may be seen under the microscope quite as easily as in the web of -the frog's foot and in the tail of the tadpole. - -One very common species of the _Blenniidae_ differs considerably in -general form from the others, its body being elongated and eel-like, but -much compressed laterally. We refer to the Butterfish or Butter Gunnel -(_Blennius gunellus_), which is often mistaken for a small eel by young -sea-side naturalists. It is exceedingly common under stones at low tide, -and may be recognised at once by the light rectangular spots along the -flattened sides of the body. It is quite as slippery and as difficult to -hold as the eel itself. - -It will be interesting to note that the ugly Sea Cat or Wolf-fish -(_Anarrhichas lupus_), which is sometimes sold for food in our large -towns, is also a member of the blenny family. It is a powerful, -rapacious fish--a veritable wolf of the sea, always ready to attack -anything. It feeds on molluscs and crustaceans, the shells of which are -easily reduced between the powerful crushing teeth that line the jaws -behind the formidable canines. - - [Illustration: FIG. 240.--THE BUTTERFISH] - -The Gobies (_Gobiidae_) form another interesting family of small littoral -fishes, easily distinguished by the fact that the ventral fins are -united in such a manner that they enclose a conical cavity. The first -portion of the dorsal fin has also six flexible spines. The Spotted Goby -(_Gobius minutus_) is commonly to be found on sand-banks, where it is -well protected by the colouring of its upper surface, which closely -resembles that of the sand on which it rests. It is said to make a nest -by cementing fragments together round some little natural hollow, or to -utilise an empty shell for a similar purpose, fixing the shell to the -surrounding bed, and constructing a tunnel by which it can enter or -leave. The eggs are deposited in this nest, and the male keeps guard -over the home. The Black or Rock Goby (_G. niger_) inhabits rocky -coasts, clinging to the rocks by means of a sucker formed of the -modified pelvic fins. - -A brightly coloured fish known as the Dragonet (_Callionymus lyra_) is -sometimes classed with the Gobies, though its pelvic fins are not -united. It is not a well-known species, and is seldom obtained except -with the dredge, as it inhabits deep water. - - [Illustration: FIG. 241.--THE BLACK GOBY] - -A peculiar little fish called the Pogge or Hook-nose (_Agonus -cataphractus_), also known as the Armed Bull-head, is commonly taken in -shrimpers' nets on the south and east coasts. Its head and body are very -angular, and are covered with an armour of keeled scales. It seldom -exceeds six inches in length, and is classed with the Flying Gurnards in -the family _Dactylopteridae_. - - [Illustration: FIG. 242.--THE FATHER LASHER] - -The true Gurnards and the Sea Bullheads form the family _Cottidae_. -Several species of the former are included among our food-fishes, and -are therefore more or less familiar to our readers. They are -characterised by their large, square, bony heads, and by the finger-like -rays of the pectoral fins which are used as organs of touch and for -creeping along the bottom of the sea. The Bullheads are represented by -the peculiar Father Lasher or Sting Fish (_Cottus bubalis_), which is -very common on our rocky coasts and is frequently captured in shrimp -nets. Its head and cheeks are armed with sharp spines which constitute -formidable weapons of offence. When taken out of the water it distends -its gills enormously; and, unless very cautiously handled, its sharp -spines may be thrust deeply into the flesh. Young specimens, with -imperfectly developed spines, may be seen in almost every rock pool, and -the full-grown fish is easily taken with rod and line by fishing in the -deep gulleys between the rocks. - -The remarkable Angler Fish (_Lophius piscatorius_), known also as the -Fishing Frog and the Sea Devil (family _Lophiidae_) is sometimes taken -off the coasts of Devon and Cornwall; and although it cannot be truly -described as a littoral species, its structure and habits are so -peculiar that it deserves a passing notice. It is an ugly fish, with an -enormous head, a short naked body, and a comparatively slender tail. The -mouth is very capacious, sometimes measuring over a foot from angle to -angle, and is directed upwards. The scaleless body is furnished with -numerous slender filaments that resemble certain filamentous sea weeds, -and these together with the dull colouring of the body generally enable -the fish to rest unobserved on the bottom. The front portion of the -dorsal fin is on the head and fore part of the body, and consists of a -series of six tentacles, three long ones on the top of the head and -three shorter just behind them; and the foremost of these, which is the -longest, terminates in a little expansion which is kept in constant -movement by the fish. The mouth is armed with rasplike teeth which can -be raised or depressed at will, and when raised they are always directed -backward; the eyes are directed upward, and the gill-openings are very -small. - -This strange creature habitually rests on the bottom of the sea, -disguised by its filamentous appendages and adaptive colouring, dangling -the expanded extremity of its first dorsal filament just over its -upturned cavernous mouth. It does not swim much, indeed it is at the -best but a bad swimmer; and when it moves it simply shuffles its heavy -body along the bottom, gliding between the stones and rocks, where it -may remain unobserved, its movements being produced by the action of the -tail, and of the paired fins, which are better adapted for walking than -for swimming. Unwary fishes, attracted by the dangling of the angler's -bait, approach the watchful monster, and while speculating on the nature -of the bait, are suddenly engulfed in the capacious mouth, from which -there is no escape on account of the backward direction of the teeth. - -The family _Trachinidae_ contains the fishes known popularly as the -Stargazers and the Weavers. These are small, carnivorous species, with -rather elongated bodies, terminating in tail fins that are not forked. -The first dorsal fin is distinct and spinous, and the spines, as well as -others that are developed on the gill-covers, are grooved for the -passage of a poisonous fluid that is secreted at their bases. - -Our littoral species include two well-known fishes (the Greater and -Lesser Weavers) that are dreaded by fishermen on account of the very -painful wounds they are capable of inflicting, and the smaller of the -two is also a considerable annoyance to bathers on certain sandy coasts. - - [Illustration: FIG. 243.--THE LESSER WEAVER] - -The Greater Weaver (_Trachinus draco_) lives at the bottom of deep -water, and is often dredged up in the trawl. Some fishermen call it the -Sting Bull, and always take the precaution of cutting off the poisonous -spines before disposing of the fish. It lives on the bottom with its -mouth and eyes directed upward, always in readiness to seize its unwary -prey, and the sharp spines of the dorsal fins are kept erect for the -purpose of promptly attacking approaching foes. Its mouth and palate are -armed with sharp teeth which render the escape of its prey almost -impossible. The smaller species (_T. vipera_) seldom exceeds six inches -in length. It lives in shallow water on sandy coasts, with dorsal spines -erect; and the wounds it produces on the unprotected feet of bathers are -often exceedingly painful on account of the injected poison, which also -causes the part to swell and turn to a dark purple colour. - -The remaining important families, although they contain well-known -British food-fishes, do not include littoral species, and for this -reason we shall pass them over with but brief notice. - -The Mackerel (_Scomber vernalis_) belongs to the family _Scomberidae_, -and is so well known that no description need be given for the purposes -of identification. We have already referred to it as a beautiful -illustration of protective colouring, its upper surface resembling the -ripples of a deep green sea and the lower the brightness of the sky. -Mackerel swim in shoals in the open sea, pursuing and devouring the fry -of herrings and other fish; and in order that they may be enabled to -cover enormous distances their muscles are richly supplied with blood. -This not only gives a pinkish colour to the flesh, but results in a -greater amount of oxidation and the maintenance thereby of a body -temperature several degrees higher than that of the surrounding water. -We would also call attention to the five or six small fins behind the -dorsal and anal fins as characteristic of the _Scomberidae_. - -Our next family (the _Cyttidae_) contains the John Dory (_Zeus-faber_), -concerning which some superstitions are still prevalent in parts. It is -brightly coloured, but not graceful in form, and is often caught in -large numbers off the coasts of Devon and Cornwall. Some fishermen call -it the Cock, on account of the crest on the back; while others know it -as St. Peter's Fish, and will point out the impression of the Apostle's -finger on each side--a black spot surrounded by a light ring. - -The Horse Mackerel (_Caranx trachurus_) is found principally in the same -parts, where it devours the fry of other fishes. It is not a very close -relative of the common mackerel, but belongs to a distinct family -(_Carangidae_), of which it is the only British representative. It is a -carnivorous fish, easily distinguished from _Scomber_ by its conical -teeth, as well as by the bony plates of the lateral line, the posterior -of which are keeled or spined. - -While the last-mentioned families contain only fishes of truly pelagic -habits, the next (_Sparidae_), formed by the Sea Breams, generally keep -near the coast, and often enter fresh waters. In these the body is much -compressed laterally, and is covered with large scales; the first half -of the dorsal fin is also spinous. The Common Sea Bream (_Sparus -auratus_), characterised by its red colour with brilliant golden -reflections, and by a dark spot on the shoulder, may often be angled -from rocks and piers. The young, in which the dark spots have not yet -appeared, are known as Chads, and are often regarded as a distinct -species. The Black Bream (_Cantharus lineatus_) is an omnivorous feeder, -and will take both animal and vegetable baits. - -The Red Mullets (family _Mullidae_) may be distinguished from the grey -mullets previously described by the two long erectile barbules on the -lower jaw. The scales are large and thin, with serrated edges, and the -front portion of the dorsal fin has weak spines. The common British -species (_Mullus barbatus_) frequents our south and east coasts, being -specially abundant round Devon and Cornwall, where they often occur in -vast shoals, and the young are often to be caught in estuaries and -harbours. - -Our last example is the Common Bass or Sea Perch (_Morone abrax_), of -the family _Serranidae_. It is also known locally as the White Salmon -and the Salmon Dace. This fish may be taken with rod and line on rocky -coasts and at the mouths of rivers. The sand-eel, or an artificial -imitation of it, is commonly used as bait, but the Cornish fishermen -more frequently employ a piece of herring or pilchard for the purpose. -The first dorsal fin of this fish has very strong spines which may -inflict severe wounds when the live creature is carelessly handled. - - * * * * * - -Omitting all mention of sea birds, for the reason previously given, we -now pass to the highest division of vertebrates--the Mammals--of which -we shall describe but one species--the Common Porpoise, this being the -only marine mammal that can be regarded as a frequent visitor to the -British coasts in general. - -It may be well at the outset to understand exactly why the porpoise is -classed with the mammals and not with the fishes--to see how its -structure and functions correspond with those of our own bodies rather -than with those of the animals dealt with in the preceding portion of -the present chapter. - -First, then, while the young of fishes are almost invariably produced -from eggs and are not nourished by the parents, the young of the -porpoise are produced alive, and are nourished with milk secreted by the -mammary glands of the mother. This is an all-important feature, and is -the one implied in the term _mammal_. The porpoise also differs from -nearly all fishes in that it breathes by lungs instead of gills, -obtaining its air direct from the atmosphere, and not from the water. -Hence we find it coming to the surface at frequent intervals to -discharge its vitiated air and to inhale a fresh supply. The body-cavity -of a mammal is divided into two parts by a muscular diaphragm, the -foremost division, called the thorax, containing the heart and lungs, -and the other (the abdomen) the remainder of the internal organs, while -the diaphragm itself plays an important part in the respiratory movement -by which air is drawn into the lungs. The body of the porpoise is so -divided, but no such division ever occurs in any of the fishes. Lastly, -the heart of the porpoise, in common with the rest of the mammals, is -divided into four cavities, and the blood is warm, while the heart of a -fish has generally only two divisions, and the blood propelled by it is -of about the same temperature as that of the surrounding medium. Several -other important differences between the porpoise and the fish might be -given, but the above will be quite sufficient to show why they are -placed in different classes. - -Mammals are divided into several classes, and one of these (_Cetacea_) -includes the fish-like Whales, Porpoises, and Dolphins, all of which are -peculiarly adapted to a purely aquatic life. Like most of the fishes, -their upper surfaces are of a dark colour, and the lower very light. -Their fore limbs are constructed on the same plan as those of the higher -mammals, the bones of the arm being attached to a large shoulder-blade, -and the hand formed of four or five well-developed fingers which are -enclosed in skin, so that they constitute a paddle or flipper well -adapted for propulsion through water. There is no collar-bone, however, -and the fingers have no nails or claws. There are no hind limbs visible -externally, but a rudimentary pelvic girdle forms a part of the internal -skeleton. A dorsal fin exists, but this is merely an extension of the -skin of the back, and is not supported by either bones or rays. The skin -itself has no scales, like that of most fishes, but is smooth and naked; -and below it lies a large amount of fat, which, being a very bad -conductor of heat, serves to prevent the escape of heat from the body. - -The tails of cetaceans are also mere folds of the skin, supported in the -centre by the extremity of the vertebral column; but unlike the tail -fins of fishes, they are expanded horizontally instead of in the -vertical plane. This latter is an important adaptive feature of the -cetaceans, since the vertical movement of a tail so disposed is exactly -what is required to assist the animals as they alternately rise to the -surface for air and again descend into the sea in search of their food. - -Among the other external characters of the cetacean we may note the -nostrils, which are always situated on the highest point of the head, -and are thus the first part exposed when the creature rises to renew its -supply of air; also the ears, which are two small apertures behind the -eye, without any form of external appendages. - -The skeleton of the cetacean is formed of light spongy bones, saturated -with oily matter; and although the animal has no true neck, visible as -such externally, it is interesting to note that, in common with all -other mammals, even with the long-necked giraffe, it possesses its seven -cervical or neck vertebrae. - -Porpoises and Dolphins together form the family _Delphinidae_, -characterised by having the blow-hole in the form of a crescent with its -convexity turned towards the front, and of these the Porpoises -constitute the genus _Phocaena_. - -The Common Porpoise (_P. communis_) is the species that is so often -seen close to our shores and in the harbours and estuaries, swimming in -shoals with a graceful undulatory movement. Porpoises move forward -entirely by the vertical action of their powerful horizontal tails, and -extend their flippers only to change their course or to arrest their -progress. At short intervals they rise to the surface, exposing their -slate-coloured backs and dorsal fins for a moment, and then immediately -dive downwards in such a manner as to appear to turn a series of -somersaults. Occasionally they will leap quite out of the water, -exhibiting their white under surfaces, which shine with a sudden flash -when illuminated by the rays of a bright sun. The blow-hole is the first -part exposed, and if one is sufficiently near the shoal a fountain of -spray may be seen to shoot into the air, and the outrush of the expired -air may be heard as each one makes its appearance. - - [Illustration: FIG. 244.--THE COMMON PORPOISE] - -The true nature of the spouting of a cetacean seems to be very generally -misunderstood, the fountain of spray produced at each exhalation giving -the idea that the animal is expelling a quantity of water from its -nostrils. This, of course, is not the case; for the cetacean, being an -air-breather, has no need to take in a supply of water, as the -gill-breathing fishes have. Air only is expelled through the nostrils; -but as the expiration sometimes commences before these apertures are -brought quite to the surface, a certain amount of water is shot upwards -with the expired air; and even if the expiration commences after the -nostrils are exposed, the small quantity of water they contain is blown -into a jet of spray; and in a cool atmosphere, the density of this is -increased by the condensation of vapour contained in the warm and -saturated air from the lungs of the animal. It will be noticed, too, -that the creature does not check its course in the least for the purpose -of respiration, the foul air being expelled and a fresh supply taken in -exchange during the short time that the blow-hole remains above the -surface of the water. - -The Common Porpoise measures five or six feet in length, and subsists on -pilchards, herrings, mackerel, and other fish, the shoals or 'schools' -of which it pursues so closely that it is often taken in the fishermen's -nets. Its flesh was formerly eaten in our own country, but it is now -seldom hunted except for its oil and its hide. About three or four -gallons of the former may be obtained from each animal; and the latter -is highly valued on account of its durability, though it should be known -that much of the so-called porpoise-hide manufactured is really the -product of the White Whale. - - - - - CHAPTER XV - - _SEA WEEDS_ - - -We now pass from the animal to the vegetable kingdom, our object being -to give a general outline of the nature and distribution of the -principal marine algae or sea weeds that grow on our shores; and to -supply a brief account of those flowering plants that either exhibit a -partiality for the neighbourhood of the sea, or that grow exclusively on -the rocks and cliffs of the coast. The present chapter will be devoted -to the sea weeds themselves, but we consider it advisable to precede our -account of these beautiful and interesting plants by a brief outline of -the general classification of plant-life, in order that the reader may -be able to understand the true position of both these and the flowering -plants in the scale of vegetable life. - -Plants are divided into two great groups, the _Cryptogams_ or Flowerless -Plants and the _Phanerogams_ or Flowering Plants. In the former the -reproductive organs are not true seeds containing an embryo of the -future plant, but mere cells or _spores_, which give rise directly to a -thread or mass of threads, to a cellular membrane, or to a cellular body -of more or less complexity of form from which the flowerless plant is -afterwards developed; while in the latter the reproductive organs are -flowers that give rise to true seeds, each of which contains the embryo -plant. - -The _Cryptogams_ are subdivided into four groups--the _Thallophytes_, -the _Charales_, the _Muscineae_, and the _Vascular Cryptogams_. - -The first of these includes all the very low forms of vegetable life, -the simplest of which (_Protophyta_) are minute plants, each consisting -of a single microscopic cell that multiplies by a process of budding, no -sexual organs of any kind being produced. Some of these minute -unicellular organisms contain chlorophyll--the green colouring matter of -plants, by the action of which, under the influence of light, the plant -is enabled to decompose the carbonic acid gas of the atmosphere, using -the carbon for the purpose of building up its own substance, and setting -free the oxygen into the air again. Others contain no chlorophyll; and -these, having no power of feeding on carbonic acid gas, are more or less -dependent on organic matter for their supplies of carbon. - -Only very slightly removed from these minute plants are the _Algae_ of -fresh and salt water, varying in size from microscopic dimensions to -enormous plants, the lengths of which may reach many yards and the -weight several stone. They contain chlorophyll, and can therefore avail -themselves of inorganic food material; and although some multiply only -by repeated subdivision of their cells, others develop sexual organs by -the union of which fertilised spores are formed. The nature of these -Algae will be more fully described presently; and we will go no further -now than to justify the location of such large and conspicuous plants -(as many are) so low in the scale of vegetable life by stating that they -are entirely cellular in structure, never producing true vessels such as -we see in higher plants; and that though some of them develop parts -which more or less resemble the leaves and roots of higher forms, the -former are far more simple in structure and function than true leaves -and the latter are never engaged in the absorption of food from the soil -to which they are fixed. - -Another important group of the _Thallophytes_ is formed by the _Fungi_, -which include the familiar mushrooms, toadstools, and the sap-balls so -commonly seen on decaying trees; also the smaller forms known as moulds, -mildew, and smut. These, also, are entirely cellular in structure; and, -since they develop no chlorophyll, are compelled to live as parasites on -living beings or to derive their food from decaying organic matter. Thus -they are the creatures of corruption, their presence always denoting the -breaking down of living matter or of matter that has previously lived. - -Now leaving the _Thallophytes_, and passing over the small group of -aquatic plants known as the _Charales_, we come to the _Muscineae_, which -contains the Liverworts (_Hepaticae_) and the Mosses (_Musci_). - -The plants of both these groups require much moisture, and are found -principally in damp, shady situations. Like the preceding groups they -are cellular in structure, never producing true vascular bundles such as -the higher plants possess; and their life histories are rendered -interesting by the 'alternation of generations' which they exhibit. The -first generation is a sexual one produced from the spores, and consists -either of a mass of delicate threads from which a plant with a leafy -axis is developed by a process of budding, or of a little green frond -(the _thallus_). These bear the male and female elements, called -respectively the _antheridia_ and the _archegonia_; and when the central -cells of the latter are fertilised by the former, they give rise to a -case, with or without a stalk, containing a number of spores. When the -case is ripe, it opens horizontally by means of a lid, thus liberating -the spores. - -Following these in the ascending scale are the _Vascular Cryptogams_, in -which some of the cells become modified into true vessels. Here, too, -the plants exhibit a distinct alternation of generations, the spore -first giving rise to a small, leafless body, the _prothallium_, which -bears the sexual organs; and then the female elements, after -fertilisation, produce the spore-bearing plant. - -This group contains quite a variety of beautiful and interesting plants, -including the Ferns (_Filicales_), Horsetails (_Equisetales_), -Club-mosses (_Lycopodiales_), Water Ferns (_Rhizocarpeae_), and -_Selaginellales_. - -Ferns usually produce their little green prothallia above ground, and -the perfect plant generally has a creeping rhizome or underground stem. -Some, however, have strong, erect, woody stems, such as we see in the -tree ferns of tropical and sub-tropical countries. The horsetails and -the club-mosses are also produced from prothallia that are formed above -ground. The perfect plants of the former have branching underground -stems which give off numerous roots, and send up annually green, -jointed, aerial stems that bear whorls of fine leaves, each whorl -forming a toothed, ring-like sheath. The fertile shoots terminate in -cones, on the modified leaves of which the sporangia are produced. The -stems of the club-mosses are clothed with small overlapping leaves, in -the axes of which the sporangia are produced; and the spores, which are -formed in abundance, constitute the lycopodium powder with which -druggists often coat their pills. - -Water ferns either float on the surface of water or creep along the -bottom, and produce their fruit either at the bases of the leaves or -between the fibres of submerged leaves. The Selaginellas are -characterised by a procumbent stem that branches in one plane only, -producing small, sessile leaves, with a single central vein. A number of -roots grow downward from the under side of the stem, and the fruit is -developed in the axils of the leaves that form the terminal cones of the -fertile branches. - -The above are all the principal divisions of the flowerless plants, and -we have now to note the general characteristics of the _Phanerogams_. -The chief of these is, of course, the possession of flowers as -reproductive organs; and although it is not convenient to give a full -description of the flower at the present time, it will be necessary to -say a little concerning it in order that we may be able to grasp the -broad principles of classification. - -A flower, in its most complex form, consists of parts arranged in four -whorls arranged concentrically. The first and second whorls, commencing -from the outside, usually consist of leaf-like bodies, united or -distinct, and are called respectively the _calyx_ and the _corolla_. The -third whorl consists of _stamens_, which are the male reproductive -organs of the plant, and each stamen consists essentially of a case--the -_anther_--in which are formed a number of little _pollen cells_. When -the anther is ripe it opens, thus liberating the pollen, so that it may -be dispersed by insects, by the wind, or by other mechanical means. The -remaining whorl constitutes the _pistil_, which is generally made up of -parts (_carpels_) arranged round a common centre, and each surmounted by -a _stigma_ adapted for the reception of the pollen cells. This portion -of the flower contains the _ovules_, enclosed in a case called the -_ovary_, and is, therefore, the female organ of the plant. When the -ovules have been fertilised by the pollen, they develop into seeds, each -one of which contains an embryo plant; and the ovary itself, ripening at -the same time, develops into the _fruit_. - -Such is the general description of a flower in its most complex form, -but it must be remembered that one or more of the whorls named above may -often be absent. Thus, calyx or corolla, or both, may not exist; and the -male and female organs may be developed on separate flowers of the same -plant, or even, as is frequently the case, on different plants of the -same species. In the latter instance the flowers are spoken of as -unisexual, those bearing the stamens being the staminate or male -flowers, and those bearing the pistil the pistillate or female flowers. - -The _Phanerogams_ are divided into two main groups, the _Gymnosperms_ -and the _Angiosperms_. In the former the ovules are naked, no ovary or -seed-case being developed. The pollen, carried by the wind, falls -directly on the ovule, and then develops a tube which penetrates to the -nucleus of the ovule, thus fertilising it. In the Angiosperms the -ovules are always enclosed in an ovary, and the pollen grains, alighting -on the stigma, are held by a gummy secretion. The tubes they produce -then penetrate through the underlying tissues, and thus come into -contact with the ovules. - -The _Gymnosperms_ include a group of small palm-like trees and shrubs -(the _Cycadeae_), of which the so-called Sago Palm is a representative; -and the _Coniferae_ or cone-bearing shrubs and trees, which may be spoken -of collectively as the Pines. In the latter the leaves are either stiff, -linear, and needle-like, or short and scale-like, or are divided into -narrow lobes; and the plants are noted for their resinous secretions. -The flowers are always unisexual, and are generally arranged in -cylindrical or short catkins, where they are protected by closely packed -scales; but the female flowers may be solitary. There is no calyx or -corolla, but the naked ovules and seeds are sometimes more or less -enclosed in the scales (_bracts_) or in a fleshy disc. - -The _Angiosperms_ form the highest division of the flowering plants; and -are subdivided into two extensive groups--the _Monocotyledons_ and the -_Dicotyledons_. The chief distinguishing feature of these is that -implied in the above names, the embryo of the former containing but one -rudimentary leaf (_cotyledon_), while that of the latter contains two. -The Monocotyledons are also characterised by having the bundles of -vessels (_vascular bundles_) of the stems dispersed; the veins of the -leaves are also usually parallel, and the parts of the flower are -arranged in whorls of three or six. In the Dicotyledons the vascular -bundles of the stem are united into a ring which surrounds a central -pith; the veins of the leaves form a network, and the parts of the -flower are arranged in whorls of four or five. - -We are now enabled to understand the relative positions of the principal -groups of plants in the scale of vegetable life, and to locate -approximately the forms with which we have to deal; and to aid the -reader in this portion of his work we present a brief summary of the -classification of plants in the form of a table for reference:-- - - - THE CLASSIFICATION OF PLANTS - - I. =CRYPTOGAMIA=--Flowerless plants. - - (_a_) =THALLOPHYTES=--Leafless, cellular plants. - 1. =Protophyta=--Unicellular plants. - 2. =Algae=--Sea weeds, &c. - 3. =Fungi=--Mushrooms, &c. - (_b_) =CHARALES.= - (_c_) =MUSCINEAE.= - 1. =Hepaticae=--Liverworts. - 2. =Musci=--Mosses. - (_d_) =VASCULAR CRYPTOGAMS.= - 1. =Filicales=--Ferns. - 2. =Equisetales=--Horsetails. - 3. =Lycopodiales=--Club-mosses. - 4. =Rhizocarpeae=--Water ferns. - 5. =Selaginellales.= - - II. =PHANEROGAMIA.= - - (_a_) =GYMNOSPERMIA.= - 1. =Cycadeae=--Cycads. - 2. =Coniferae=--Cone-bearing trees. - (_b_) =ANGIOSPERMS.= - 1. =Monocotyledons.= - 2. =Dicotyledons.= - -We have now to deal more particularly with those marine _Algae_ that are -commonly known as Sea Weeds, and which add so much to the beauty of our -rocky coasts. These exhibit such a variety of graceful forms, and such -charming colours, that they are admired and treasured by thousands of -sea-side ramblers, who are attracted by them merely on account of their -pleasing general appearance; but the naturalist has all this and a great -deal more to interest and instruct him, for the sea weeds possess quite -a number of peculiar and characteristic features that render them well -worthy of a detailed study, especially when they are compared and -contrasted with the better-known flowering plants of our fields, woods, -and hedgerows. - -It has already been observed that sea weeds differ from the majority of -flowering plants in that they have no true roots or leaves, though they -are often attached to rocks and other substances by a root-like disc, -and sometimes have leaf-like expansions that are supported by stem-like -rods. The root-like structures, however, serve simply for the attachment -of the plant, and are never concerned in the absorption of nourishment -like the true roots of higher plants; and the leaf-like expansions, -though they are sometimes symmetrical in form, never exhibit the spiral -arrangement that obtains in the leaves of higher plants, from which they -also differ in function. - -The plant-body of a sea weed is called a _thallus_, and differs -considerably in the various species. Sometimes it has no expanded -portion whatever, but is more or less cylindrical in all parts, and may -be either branched or simple; and in some species it forms a simple -crust or a soft jelly-like covering on a rock. - -All portions of a sea weed are made up of cells, and these are never -modified into vessels such as we see in the stems, leaves, and roots of -higher forms of vegetable life; and one who is commencing the study of -the algae will find much interesting work in the examination of their -microscopic structure. Thin sections of various parts of the larger -weeds, cut with a sharp knife or a razor, and examined in a drop of -water under a cover-glass, will show the cellular structure perfectly; -while minute fragments of the small and slender species are sufficiently -thin and transparent to display the form and arrangement of their cells -without any previous preparation. - -One of the principal charms of the marine algae lies in the great variety -of colour that they display. They all contain chlorophyll--that -remarkable green colouring matter which enables a plant, under the -influence of light, to feed on the carbonic acid gas existing in the -atmosphere, or held in solution in water; and with its aid the sea weeds -can utilise this product of decay and animal respiration that would -otherwise accumulate in the water of the sea. But, in addition to this -bright green chlorophyll, many of the sea weeds contain a second -colouring substance, and in these the great variety of tint is dependent -on the nature of the latter and on the proportion in which it is present -as compared with the chlorophyll itself. - -The different means by which the algae reproduce their kind forms a most -engrossing subject, and to the botanist a most important one, for it has -much to do with the classification of the species. The affinities of -plants may be better determined by the nature of their reproductive -processes than by any other features, but unfortunately this is not so -well understood with regard to the algae generally as compared with many -other divisions of the vegetable kingdom; and, as a consequence, there -is still a considerable difference of opinion, not only as to the extent -of the whole group, but also as to its divisions and subdivisions. The -reason for this is clear; for while it is quite an easy matter to trace -a flowering plant through its complete cycle from seed to seed, it -requires a much more careful examination, combined with much microscopic -work, to trace a lowly organised plant from spore to spore. - -Some of the algae may be reproduced without the agency of any sexual -elements; that is, without the aid of parts that correspond with the -ovules and the fertilising pollen of a flowering plant. Some of these -are reproduced by a repeated subdivision, or by the separation of a -portion of the plant that is capable of independent growth; while others -produce spores that do not result from the fusion of two different -cells. In most, however, sexual differences are to be observed, some -cells being modified into female organs, containing one or two more -minute bodies that are capable of developing into new plants after they -have been fertilised, and other cells produce the male elements by means -of which the fertilisation is accomplished. The fertilised cells are -spores, but are named differently according to the nature of their -development. They all differ from true seeds in that they never contain -an embryo plant, but germinate by the elongation of some particular -part, which subsequently grows by a continuous process of cell-division; -or the cell-division may originate directly in the spore without any -previous elongation or expansion. - -The sea weeds are usually classified according to the colour of their -spores; but, since this colour generally corresponds with that of the -plant itself, we may almost say that they are grouped according to their -general tints. There are three main divisions:-- - - The _Chlorospermeae_, or Green-spored; - The _Rhodospermeae_, or Red-spored; and - The _Melanospermeae_, or Brown-spored. - -The _Chlorospermeae_ contain no colouring matter other than the -chlorophyll. They are mostly small weeds, of a delicate green colour; -and, although they are not particularly conspicuous on our shores, they -contribute very considerably to the beauty of the rock pools, where -their delicate green fronds contrast richly with the olive -_Melanosperms_ and the pink and white corallines. The thallus or -plant-body is very varied in form, sometimes consisting of a broad -membrane, but more commonly of tufts of slender green filaments or of -narrow, flattened fronds. - -These weeds are most beautiful objects for the microscope, and they are -generally so thin and transparent that no section-cutting is necessary, -nothing being required except to mount very small portions in a drop of -water. In this simple manner we may study the beautiful arrangement and -the various forms of the cells of which they are composed. The more -delicate species will be found to consist of a single layer of cells -only, while in the larger forms--the _Ulvaceae_, for example--the thallus -may be formed of two or three distinct layers, and some of the cells may -be elongated into tubes. - -A remarkable feature of the green-spored weeds is the large size of the -chlorophyll granules as compared with those of the other groups, and -also the great variety of forms which these granules assume. They may be -easily seen under a low power, and the examination of the weeds will -show that the thalli are not uniformly green, but that the colour of the -plants is due entirely to the chlorophyll granules, the remainder of the -plant substance being quite colourless. - -If a green sea weed be placed in alcohol for a short time, it will be -found that the liquid assumes a green colour, while the plant itself -becomes colourless. The explanation is, of course, that chlorophyll is -soluble in alcohol. The presence of starch also in the weed may be -proved in a very simple manner, as follows:--Mount a small piece in -water, and then put a drop of iodine solution by the edge of the -cover-glass. The solution will gradually diffuse itself around the -object, turning the starch-grains to a deep blue colour, and so -rendering them very conspicuous under a moderately high power. - -The manner in which the green weeds are reproduced is very interesting -also. In some cases the fragments of a thallus that have been detached -by storms or other mechanical means possess the power of independent -growth, and develop into plants; and this mode of reproduction may often -be watched in the indoor aquarium. Another method is by the agency of -little spores (_zoospores_) that are produced at the edges or -extremities of the thallus. Certain of the cells become modified into -what are called _zoosporangia_, and the minute zoospores are formed -within them. The walls of the cells either gradually degenerate, or are -fractured, and the zoospores are thus set free. The latter are provided -with little vibratile cilia, by which they move about freely in the -water. Some eventually settle down and germinate without any further -aid, but others are unable to develop until they have been fertilised by -fusion with another cell. The former is therefore an _asexual_ -development, while the latter is _sexual_. - -Some of the delicate, filamentous green algae are reproduced by another -process termed _conjugation_. In this case two adjacent threads that lie -close together become lightly united by a covering of gelatinous -substance, and a cell of each throws out a process. The processes are -directed towards each other, and unite to form a tube in which the -contents of the two cells become fused together, with the result that -zoospores are produced. - -Among the lowest of the green sea weeds are the plants known -collectively as the _Confervaceae_, which consist of delicate green -filaments, usually attached to rocks in dense masses, but often found -floating freely in the rock pools. The filaments are composed of cells -joined together at their ends, and are always unbranched. - -Confervae are found principally in the tide pools, especially near -high-water mark, and often abound in hollows in the rock even above -high-water mark, where the spray of the waves is mingled with rain-water -or the drainage from the land. They exist in both fresh and salt water, -and some species seem capable of thriving in brackish water of any -degree of salinity. - -Allied to the confervae is a group of marine algae called _Cladophora_, -very similar to the former in general appearance, and found in similar -situations, but readily distinguished by the branching of their jointed -filaments. The various species of this group are very beautiful weeds, -their delicate filaments looking very pretty as they float and sway in -the water of the pools. They are also exquisite objects for the -microscope; but, unfortunately, often lose their natural colour when -preserved dry. They vary in colour, some few being of a dull green tint, -while others are bright green, sometimes with a beautiful silky gloss. - -One species (_C. pellucida_) is more rigid than most of the others; its -fronds stand out erect and firm, and are repeatedly forked near the -tips. It is a moderately common weed, found in the lower rock pools, and -may be readily recognised by the long one-celled joints, from the tops -of which the branches proceed. Another species (_C. diffusa_) is also -very firm in structure, so much so that its bristly tufts retain their -form when removed from the water, instead of becoming matted together in -a shapeless mass. Its branches are rather long, and bear a few simple -branchlets towards their extremities. It is found in rock pools between -the tide-marks. _C. lanosa_ is a very pretty little weed, growing in -dense globular woolly tufts, an inch or more in diameter, on the olive -tangles between the tide-marks. It is of a pale yellowish-green colour, -which becomes much paler, or is even altogether lost, when the plant is -preserved in a dry state, and, at the same time its fine glossy -appearance is lost. Its fronds have straight branches, all making very -acute angles, and they have also small root-like filaments. It much -resembles another species (_C. arcta_), which grows in dense tufts on -rocks, but the latter is larger, not so slender, and more freely -branched. The cells, too, of _C. arcta_ are longer, being about ten -times the length of the diameter, and the fronds are silvery at the -tips. - -Nearly thirty species of _Cladophora_ have been described, but it is -impossible to give here a detailed description of all. We add, however, -a brief summary of the distinguishing features of a few other species -that are common on our coasts. - -_C. rupestris_ is common everywhere, and easily recognised by its rigid, -branching, tufted fronds, of a dark greyish-green colour; its branches, -which are opposite, bear awl-shaped branchlets. It is found in rock -pools from half-tide downwards, and in deep water beyond the tide-marks, -the plants growing in the latter situations being generally of a fine -dark-green colour. - -_C. laetevirens_ is also very common on rocks between the tide-marks. Its -fronds are tufted and freely branched, of a pale-green colour and soft -flexible texture, and about six inches long. The branchlets are usually -slightly curved. - -_C. gracilis_ is a beautiful plant that grows on large weeds, especially -the Sea Grass (_Zostera_) in deep water; and although not very common, -it is sometimes found on the beach after storms. It is characterised by -its slender silky fronds, from a few inches to a foot in length, of a -yellowish-green colour. It may always be known by the comb-like -branchlets growing only on one side of each branch. - -_C. refracta_ grows in dense tufts, two or three inches long, in rock -pools near low-water mark. Its fronds consist of rigid stems in -rope-like bundles that are very freely branched, the whole tuft being of -a yellow-green colour and silky texture. _C. albida_ closely resembles -it in structure and habit, but may be distinguished by its paler colour, -which disappears when the weed is dried, and by its longer and more -delicate branches. - -In another order of the green-spored algae (the _Siphoneae_ or -_Siphonaceae_) the frond is formed of single branching cells, and many of -these are often interwoven into a spongy mass, and sometimes coated with -a deposit of calcareous matter. - -In the genus _Codium_ the fronds are of a sponge-like texture, composed -of interwoven branching fibres, and are of a globular, cylindrical, or -flattened form. The commonest species is _C. tomentosum_ (Plate VII.), -which consists of sponge-like, dark-green cylindrical fronds, which are -forked and covered with short hairs that give it a woolly appearance -when in the water. Each frond is composed of slender interwoven fibres -with club-shaped filaments passing vertically to the surface. It grows -on rocks in the pools between the tide-marks, and is abundant on nearly -all our coasts. - -The Purse Codium (_C. bursa_) has spongy hollow fronds of a globular -form, varying from a quarter of an inch to five or six inches in -diameter. It is a rare species, being found only at a few places on the -south coast. Another species (_C. adhaerens_) adheres to rocks, over -which the fronds spread in irregular soft patches, the club-shaped -vertical filaments of its interwoven fibres giving it the appearance of -rich green velvet. - -An allied weed (_Bryopsis_), named from its moss-like appearance, grows -in erect tufts, each frond consisting of a branched one-celled filament. -There are two species of the genus, one (_B. plumosa_) characterised by -the light feathery nature of its fronds, the stems of which are branched -only near the top. It is found in rock pools on most of our coasts. The -other (_B. hypnoides_) is more freely branched, and the branches are -long, and issue from all sides of the stem. Like the last species, it -has branches on the outer part of the stem only, but it is of a softer -texture. - -The best known of the green-spored weeds are certainly those belonging -to the _Ulvaceae_, characterised by their flat or tubular fronds, -sometimes of a purplish colour, the cells of which multiply both -horizontally and vertically as the plants grow. In the typical genus, -_Ulva_, the frond is sometimes in two distinct layers, and becomes more -or less inflated by the accumulation of either water or oxygen between -them. The commonest species are _U. lactuca_ and _U. latissima_, both of -which are eaten by the dwellers on some of our coasts. The former, -commonly known as the Lettuce Ulva, has a frond of a single layer of -cells, and grows on rocks and weeds between the tide-marks. It is common -on many oyster beds, and is employed by the fishermen to cover the -oysters when sent to market; they call it 'oyster green.' This species -is shown on Plate VIII. _U. latissima_ or the Broad Ulva sometimes -reaches a length of two feet, and a breadth of nearly a foot. The fronds -are composed of two layers of cells, are of an irregular shape, with a -very wavy, broken margin, and of a bluish-green colour, It is known -as the Green Laver, and is used as food in districts where the true -laver (_Porphyra_) is not to be obtained. A third species--the Narrow -Ulva (_U. Linza_)--has smaller and narrower fronds, of a more regular -shape and of a bright-green colour. The fronds are composed of two -layers of cells. - - [Illustration: Plate VII. - - SEA-WEEDS - - 1. Fucus nodosus - 2. Nitophyllum laceratum - 3. Codium tomentosum - 4. Padina pavonia - 5. Porphyra laciniata] - -The _Ulvae_ retain their colour perfectly when dried, and, with the -exception of _U. latissima_, are of a mucilaginous nature, and adhere -well to paper, but, unfortunately, the graceful wavy outline of the -fronds is lost in pressed specimens. - -The 'true laver' mentioned above, which is also popularly known as -Sloke, is closely allied to _Ulva_, but may be distinguished from it by -the colour of its membranous fronds, which vary from a light rose to a -deep purple or violet, occasionally inclining to olive, but never green. -Its scientific name is _Porphyra laciniata_ (Plate VII.), and it differs -from the majority of the _chlorospermeae_ in having dark-purple spores, -which are arranged in groups of four in all parts of the frond. The -fronds are very variable in form and size, being sometimes ribbon-like, -and sometimes spreading into an irregular sheet of deeply-divided -segments; and the remarkable variety of form and colour has led to a -division into several species. These, however, merge into one another so -gradually that the separation seems to be hardly necessary. - -The same remark concerning the multiplicity of species applies to -another allied genus called _Enteromorpha_, in which the fronds are -green and tubular, and often more or less branched. In these the colour -varies from a pale to a dark green, and the cells are arranged in such a -manner as to give a reticulated appearance. The commonest and -best-defined species are _E. intestinalis_, the tubular fronds of which -are constricted at intervals in such a manner as to resemble the -intestines of an animal, and _E. compressa_, with branched fronds of -variable form and size. The former is common on all our coasts, and may -even be found in rivers and ditches some distance from the sea. It -thrives equally well in fresh and salt water, and appears to grow most -luxuriantly in the brackish waters of tidal rivers. The latter species -also thrives best in similar situations. - -Coming now to the red-spored sea weeds (_Rhodospermeae_), we have to deal -with some of the most charming of the marine algae that invariably -attract the sea-side rambler, and provide many of the most delightful -objects in the album of the young collector. Their brilliant colours, -varying from a light red to dark purple and violet, are sufficient in -themselves to render them popular with the collector, but in addition to -this striking feature they are characterised by extreme elegance of form -and delicacy of texture. They are to be found in most rock pools, from -near high-water mark downwards, the smaller and more delicate forms -adding much to the beauty of these miniature seas; but the largest and -many of the prettiest species exist only at or beyond the lowest ebb of -the tide, and hence the algologist, in quest of these beautiful plants, -will find it necessary to work at the very lowest spring tides, with the -occasional aid of a small boat drifted into the narrow channels among -outlying rocks, and a long hook with which to haul up submerged -specimens; and it will also be advisable to search the line of debris at -high-water mark after stormy weather for rare weeds that may have been -detached and washed ashore by the angry waves. - -While engaged in the former of these employments--the searching of -outlying rocks with the boat--and also when examining the outer rock -pools which are disturbed by the waves that wash over their banks, the -simple instrument known as the water-telescope will prove invaluable. -Everyone must have noticed how difficult it is to observe objects in -water, the surface of which is disturbed by the wind or some other -cause; but the simple appliance named, consisting only of a long tube of -metal, a few inches in diameter, and painted a dead black inside, will -enable the observer to see all submerged objects with the greatest of -ease when the water is itself clear. The principle of the -water-telescope is as simple as its construction; for the tube, -protecting the surface of the water within it from the disturbances -outside, prevents the light from being refracted successively in -different directions, while the dead-black surface of the interior -prevents those internal reflections that would otherwise cause the -vision to be indistinct. - -A few hours spent with the rhodosperms at the sea-side will be -sufficient to show not only the great variety of their form and -colouring, but also that the same species may vary according to the -position in which it grows. Most of the smaller forms are delicate and -filamentous, but others have expanded fronds which are very leaf-like. -The brightest colours are usually to be found at or beyond low-water -mark, where the weeds are covered with a considerable height of water -for hours together, and also in shady situations at higher levels, while -some of the species that grow in the upper rock pools are often of such -a deep colour, with so much admixture of brown, that they may be easily -mistaken for the olive melanospores to be presently described. - -Most of the rhodosperms are attached directly to the rocks, and the -larger species have often a root-like disc by which they are very firmly -held; but some of the smaller species grow attached to larger weeds, -into the substance of which they frequently penetrate; and it is -possible that these derive some amount of nourishment from the sap of -their supporters. Some are of a recumbent nature, being attached to the -rock throughout their whole length, while others are so incrusted with -carbonate of lime which has been extracted from the water that they -resemble corals rather than forms of vegetable life. Nearly all of them -contain a bright-red colouring matter in addition to the chlorophyll by -which they are enabled to feed on carbonic acid gas. - -None of the rhodosperms are of really microscopic dimensions, and they -all grow by the repeated division of the cells of the apex, while the -branches are derived by the similar division of new cells at the sides. - -All plants are particularly interesting during the period of fruiting, -and this is remarkably the case with many of our red-spored sea weeds, -which are brighter and prettier while laden with their spore-producing -cells; and the collector of marine algae should always endeavour to -obtain as many species as possible in fruit, not only on account of the -brighter appearance that may characterise them at this time, but mainly -because the opportunity of studying the mode of reproduction should not -be missed. - -In the rhodosperms the reproduction may be either asexual or sexual. In -the former case fertile spores are produced without the necessity for -any outside fertilising element, and four are usually produced in each -one of the sporangia, hence they are generally known as _tetraspores_. -Where the reproduction is of the sexual type, the male cells are -produced singly in the terminal cells of the fronds, and since they are -usually crowded together in considerable numbers, and contain none of -the red colouring matter that exists in the other parts of the plant, -their presence is easily observed. - -The female cells (_carpogonia_) are also produced on the tips of the -branches, and when the male elements escape from their cells, they are -conveyed passively by the movements of the water, for they have no -vibratile cilia by which they are propelled, and on coming into contact -with the female cell they adhere closely. An opening is then formed in -the latter, and the male element enters the carpogonium, which -germinates, deriving its nourishment from the parent plant, and the -spores are thus formed. Lastly, it is interesting to note that the -asexual spores, the male cells, and the female cells are generally -produced on different plants of the same species. - -We will now proceed to examine some of the best known and most -interesting of the rhodosperms, beginning with the order _Ceramiaceae_, -which contains a number of red or reddish-brown weeds with jointed, -thread-like fronds that enclose a single tube, and which are generally -surrounded by a cuticle of polygonal cells. The spores are contained in -transparent berry-like sacs which are naked; and the four-parted spores -(_tetraspores_) are formed in the cells of the cuticle or at the tips of -the fronds. - -Over twenty British species belong to the genus _Callithamnion_, and -nearly all of them are pretty red or rose-coloured, feathery plants that -are conspicuous for their beauty. Nearly all are of small size, the -largest measuring only seven or eight inches, while some are so small -that they would scarcely be noticed except by those who search -diligently for them. The principal features of the genus are, in -addition to those mentioned above as common to the order, that the -spores are angular, and clustered within a transparent sac, and the -tetraspores are naked and distributed on the branches. - -In some species the fronds have no stem, and these are very small, -generally only about a quarter of an inch in height or less, and they -grow on rocks or weeds, sometimes clothing the surfaces with a -velvet-like covering. _C. floridulum_ forms a kind of reddish down on -the rocks, sometimes in little rounded patches, but sometimes completely -covering the surface. It occurs on several parts of the English coast, -but is so abundant on the west coast of Ireland that the beach is strewn -with it after stormy weather. Other allied species grow in minute tufts -on rocks, or are parasitic on other weeds, and are so inconspicuous that -they are but little known. - -Another section of the genus is characterised by pinnate fronds with -opposite segments, and the species are very pretty plants with fronds -generally a few inches in length. One of the commonest of these is the -Feathered Callithamnion (_C. plumula_), a great favourite with -collectors of sea weeds, and a most interesting object for the -microscope. Its soft and flexible fronds grow in tufts from two to five -inches long. The branches are regularly arranged, and the comb-like -branchlets bear the tetraspores on the tips of the plumules. This -beautiful weed grows near low-water mark, and in deep water, and is -often very abundant on the beach after storms. _C. Turneri_ is another -common species, easily known by its creeping fibres, attached by little -discs to some larger weed, and from which the tufts of branched fronds -stand out erect. On the west and south-west coasts of Britain we may -often meet with the allied Crossed Callithamnion (_C. cruciatum_), which -grows on rocks, close to low-water mark, that are covered with a muddy -deposit. It grows in tufts, somewhat resembling those of _C. plumula_, -but its plumules are arranged two, three, or four at a level, and are -very crowded at the tips of the branches. - - [Illustration: FIG. 245.--_Callithamnion roseum_] - - [Illustration: FIG. 246.--_Callithamnion tetricum_] - -Still another section of this large genus contains weeds of a more -shrubby growth, with veined stem and branches jointed obscurely. Of -these the Rosy Callithamnion (_C. roseum_) is not uncommonly found on -muddy shores, and especially in and near the estuaries of rivers. It -grows in dense dark-coloured tufts, two or three inches long, with -alternate branches much divided. The tetraspores occur singly, one at -the top of each of the lower joints of the pinnules of the plumes. _C. -byssoideum_ grows on larger weeds in the rock pools, and especially on -_Codium tomentosum_ (p. 353), in dense tufts of exceedingly fine -filaments, jointed, and branched irregularly. The upper branches are -plumed, and their tips bear very fine colourless filaments. The -spore-clusters are arranged in pairs, and the tetraspores are thinly -scattered on the pinnules of the plumes. This species is so very -delicate in structure that a lens is absolutely necessary to make out -its structure. It is, in fact, impossible to distinguish between the -various species of Callithamnion without such aid; and many of them, -particularly the species last described, require the low power of a -compound microscope. - -Among the other common species, belonging to the same section, we may -mention _C. corymbosum_, distinguished by its very slender, rosy, -jointed fronds, with the ultimate divisions of the branches disposed in -a level-topped (_corymbose_) manner, growing on rocks and weeds near -low-water mark; _C. polyspermum_, growing in globular tufts on _Fucus -serratus_ and _F. vesiculosus_, with short awl-shaped pinnules, and -closely-packed clusters of spores; _C. Hookeri_, with opaque stem and -branches, and spreading branchlets that are themselves branched, and -bear spreading plumules at their tips; and _C. arbuscula_, found on the -west coasts, with a stout stem, naked below, and having a very bushy -habit. - -It is often by no means an easy matter to distinguish between the -different species in such a large genus as _Callithamnion_, and we -strongly recommend the beginner to first study the characteristics on -which the classification of the _Algae_ is based, and to arrange his -specimens according to the orders and genera to which they belong; and -then, after mastering the principles of classification, he should refer -to one of those larger works in which all known British species are -described, and make himself acquainted with the features of each -individual species in his collection. - -Before leaving the present genus we ought also to mention the fact that -many of the species lose their natural colour rapidly when placed in -fresh water; hence when they are being cleansed for mounting salt water -should be employed. Further, even after they have been satisfactorily -mounted, they are liable to be spoiled if left exposed to moist air. The -salt water used need not be the natural sea water; a solution of common -table salt, made up to approximately the same strength as sea water, -will answer the purpose just as well. - -The genus _Griffithsia_ includes some very beautiful weeds of delicate -threadlike structure and of a fine rose colour. The frond contains a -single tube, and is jointed and forked, the joints being usually -transparent. The spore clusters are enclosed in a gelatinous sac -surrounded by a whorl of little branchlets, the spores themselves being -minute and angular. The tetraspores are attached to the inner side of -whorled branchlets. - -The commonest species is _G. setacea_, which is of a bright-red colour -and slightly branched. It is also of a somewhat firm structure, but soon -loses both firmness and colour when removed from salt water; and, like -_Callithamnion_, rapidly fades if put into fresh water, which is -readily absorbed through its membranes, causing them to burst and -discharge their colouring matter. It receives its specific name from its -bristle-like forked fronds. _G. secundiflora_ is somewhat like -_Setacea_, but is larger, and the tips of its branches are obtuse. Its -fronds grow in fan-shaped tufts five or six inches long. It is not a -common weed, but may often be met with on the coast of Devon and -Cornwall. - - [Illustration: FIG. 247.--_Griffithsia corallina_] - -_G. barbata_, or the Bearded Griffithsia, receives its name from its -very delicate fibres, which bear spherical, pink tetraspores. It seems -to occur only on the south and south-west coasts, where it grows on -stones or attached to other weeds. Our last example of the genus is _G. -corallina_, which is of a deep-crimson colour, and is so jointed as to -have the appearance of a coralline. Its fronds are from three to eight -inches long, regularly forked, and of a gelatinous nature. The joints -are somewhat pear-shaped, and the spore clusters are attached to their -upper ends. It soon fades, and even if its colour is satisfactorily -preserved, the pressure of the drying press destroys the beautiful -rounded form of its bead-like joints. It forms a lovely permanent -specimen, however, when preserved in a bottle of salt water, with the -addition of a single grain of corrosive sublimate. - - [Illustration: FIG. 248.--_Halurus equisetifolius_] - - [Illustration: FIG. 249.--_Pilota plumosa_] - -Our next genus (_Halurus_) contains a common weed of the south coast -which was once included in _Griffithsia_. It is the Equisetum-leaved -Halurus (_H. equisetifolius_), so called because its branches are -regularly whorled round the nodes of the jointed branches, thus -resembling the semi-aquatic Mare's Tail. Its frond is tubular, and the -spore-clusters are situated on the tips of the branches, surrounded by a -whorl of small branchlets. - -The genus _Pilota_ has a slightly flattened cartilaginous frond, divided -pinnately, and the axis surrounded by a cuticle of two layers of cells. -The spore-clusters, at the tips of the branches, are surrounded by a -whorl of branchlets. It contains only two British species, one of which -(_P. plumosa_) is a very feathery species, with comb-like branchlets, -growing on the stems and fronds of other weeds found on our northern -shores. The other (_P. elegans_), with narrower fronds, in long flaccid -tufts, is found all round our coasts. - -Our last genus of the _Ceramiaceae_ is the large and typical one -_Ceramium_, which contains about a dozen British species in which the -frond is threadlike, jointed, branched or forked repeatedly, with the -tips of the branchlets usually curled. The spore-clusters are enclosed -in transparent sessile sacs, surrounded by a whorl of very short -branchlets; and the tetraspores are embedded in the cortex, but -distinctly visible. As a rule the fronds are very symmetrical, and the -branches radiate in a regular fan-like manner. - -In one species of the genus the frond is completely covered with cortex -cells, and at each node of the frond there is a single spine which, -although so small as to be invisible without a lens, so effectually -locks the threads together that they form an entangled mass that is not -easily arranged to the satisfaction of the collector. The species -referred to is _C. flabelligerum_--the Fan-bearing Ceramium--and is very -rare except in the Channel Islands. - -Other species are armed with one or more spines at the nodes, but the -nodes only are covered with cortex cells, which render them opaque, -while the internodes or joints are transparent. In this group we have -_C. ciliatum_--the Hairy Ceramium, with reddish-purple segments, and a -regular whorl of hairs, directed upwards, round each node; each hair or -spine consists of three segments. This plant is common during the summer -and autumn, and may be found in the tide pools at all levels, either -attached to the rocks or parasitic on other weeds. The same section -contains _C. echinotum_, with rigid, forked fronds, and -irregularly-scattered one-jointed spines; it is common on the south -coast, where it may be found on the rocks and weeds of the upper tide -pools; and _C. acanthonotum_, also common in the rock pools, with a -single strong three-jointed spine on the outer side of each filament. -The last-named weed is found principally on the northern shores, -especially on rocks covered with the fry of the common mussel. - -Other species are characterised by transparent internodes as above -described, but have no spines at the joints, and may thus be easily -floated on to a sheet of paper without the troublesome matting of their -fronds. These include the Straight Ceramium (_C. strictum_), with erect -and straight branches growing in dense tufts, and conspicuous -tetraspores arranged round the nodes of the upper branchlets, _C. -gracillimum_, of the lower rock pools, with very slender gelatinous -fronds, swollen nodes and small fan-shaped branchlets; _C. tenuissimum_, -closely resembling _C. strictum_ in general appearance, but -distinguished by having its tetraspores only on the outer side of the -nodes; and the Transparent Ceramium (_C. diaphanum_), which may be found -throughout the year on rocks and weeds in the rock pools. The last -species is the largest and most beautiful of the genus, and may be -readily recognised by its light-coloured, transparent stem with swollen -purple nodes, and its conspicuous spore-clusters near the tips of the -filaments. - - [Illustration: FIG. 250.--_Ceramium diaphanum_] - -Our last example of the genus is the Common Red Ceramium (_C. rubrum_), -which may be found in the rock pools at all levels. It is very variable -in form, but may be known by its contracted nodes, in which the red -tetraspores are lodged, and its spore-clusters surrounded by three or -four short branchlets. It differs from most of the other species in -having both nodes and internodes covered with cortex-cells, and hence -the latter are not transparent. - -The order _Spyridiaceae_ has a single British representative which may be -found in various localities on the south coast. It is _Spyridia -filamentosa_, a dull-red weed with thread-like, tubular, jointed fronds, -from four inches to a foot in length. The main stem is forked, and -densely clothed with short and slender branchlets. The frond is covered -with a cortex of small cells. The spore-clusters are grouped together, -several being enclosed in a membranous cell in conceptacles, or external -sacs, at the ends of the branchlets; and the tetraspores are arranged -singly along the jointed branchlets. - -The next family (_Cryptonemiaceae_) is an extensive one, containing -nearly twenty British genera of red or purple weeds, with unjointed, -cartilaginous, gelatinous, and sometimes membranous fronds. The spores -are irregularly distributed, and are contained either in sunken cells or -in conceptacles. The tetraspores are either in cells at the edges of the -frond or collected together in compact groups. - -Of the genus _Dumontia_ we have only one species (_D. filiformis_), the -frond of which is a simple or branched tube, from an inch to more than a -foot in length, containing a loose network of filaments when young, and -only a gelatinous fluid when the plant is mature. The spores exist in -rounded clusters among the cells of the tube, and the tetraspores are -similarly situated. A variety with wide wavy fronds is sometimes found -in the brackish water near the mouths of rivers. - -_Gloiosiphonia capillaris_ is a very delicate and beautiful weed found -in the lowest tide pools of the south coast. Its frond is a very slender -branched tube, filled with a gelatinous fluid, and composed of delicate -filaments embedded in transparent gelatine. It is a beautiful object for -the microscope. - -_Schizymenia_ (_Iridaea_) _edulis_ has flat, oval, dark-red fronds that -grow in clusters; and, being eaten by various marine animals, is often -found imperfect and full of holes. The fronds are sometimes a foot or -more in length, and five or six inches wide. They are thick and -leathery, and each is supported on a short, cylindrical stem. - -In the lower tide pools we commonly meet with _Furcellaria fastigiata_, -with brownish-red, cylindrical fronds, solid, forked, and densely -tufted. The branches are all of the same height, with sharp tips; and -the spore-clusters are contained in terminal lanceolate pods. This weed -is very much like _Polyides_, of another order, but may be distinguished -by its fibrous, creeping root, while that of _Polyides_ is a disc. - -The genus _Chylocladia_ is characterised by a tubular rounded frond -composed of two layers, the inner consisting of branching filaments, and -the outer cellular. The spores are contained in external cones with a -pore at the apex, and the tetraspores are among the superficial cells of -the branches. There are two common British species of the genus, one of -them--_C. articulata_--with long, tubular fronds, constricted at -intervals, the lower branches forked and the upper whorled and tufted; -and _C. clavellosa_, with freely branched fronds bearing short -spindle-shaped branchlets. - -One of the best-known algae of the present family is the Irish Moss or -Carrageen (_Chondrus crispus_), which will be at once recognised by its -representation on Plate VIII. Its fronds are cartilaginous, forked and -fan-shaped; and, when growing in deep, sheltered pools, its branches are -often broad and much curled. This weed is an important article of -commerce, being still used as a food for invalids. When boiled it -yields a colourless gelatine. - -In the genus _Gigartina_ the frond is cartilaginous, flat, or -threadlike, irregularly branched, and of a purplish-red colour. The -spores are contained in external tubercles, and the tetraspores are -arranged in masses beneath the surface. The only common species is _G. -mamillosa_, which has a linear, furrowed stem, with fan-shaped, -deeply-cleft fronds. The spores are contained in mamilliform tubercles -scattered over the surface of the frond. - -_Callophyllis_ (_Rhodymenia_) _laciniata_ is found on most rocky coasts. -It has bright-red, fleshy fronds that are deeply cleft into wedge-shaped -segments, the fertile specimens with waved edges and small marginal -leaflets. It is found on rocks and Laminaria stems beyond the -tide-marks, but is commonly washed up on the beach during storms. It is -a beautiful weed, and retains its colour well when dried. - -_Cystoclonium_ (_Hypnaea_) _purpurascens_ is a very common weed, growing -on other algae between the tide-marks, and sometimes reaching a length of -two feet. Its cartilaginous, purple fronds are much branched, and become -almost black when dried. The spores are embedded in the smallest -branches, and the tetraspores are arranged among the superficial cells. - -The genus _Phyllophora_ contains a few British weeds with a stiff, -membranous frond, bearing leaf-like appendages, and supported on a -stalk. The tetraspores are contained in external wart-like swellings. -The commonest species is _P. membranifolia_, the fronds of which are -divided into wedge-shaped segments, and grow in tufts from an expanding -root. The spores are contained in stalked sporangia, and the tetraspores -are near the centres of the segments. Another species--_P. rubens_--has -a shorter stem, and grows in deep and shady rock pools. Its fronds are -densely tufted; and, as the plant grows, new series of segments are -formed at the tips of the older ones. A third species (_P. -palmettoides_) has a very bright-red frond and an expanded root. - -The order _Rhodymeniaceae_ includes a number of red or purple sea weeds -with flat or thread-like unjointed, cellular fronds, the surface cells -forming a continuous coating. The spores are lodged in external -conceptacles, and are at first arranged in beaded threads. The -tetraspores are either distributed among the surface cells, collected in -clusters, or situated in special leaflets. - -The typical genus (_Rhodymenia_) contains two red, membranous weeds, -the commoner of which is _R. palmata_ (Plate VIII.), so common on the -Scottish and Irish coasts, where it forms an important article of diet, -and is known as the Dulse or Dillisk. It is also widely distributed over -the English coasts. Its broad, fleshy fronds are divided into -finger-like lobes, and are either sessile or supported on a stalk that -proceeds from a small discoid root. The frond is very variable in form, -being sometimes divided into very narrow segments, and sometimes quite -undivided. One variety has a number of small stalked leaflets on its -margin (see Plate VIII.); and another is very narrow, with wedge-shaped -irregular lobes. _R. palmetta_ is a smaller and less common species that -grows on rocks and large weeds in deep water. The tetraspores form -crimson patches on the tips of the lobes. - -_Maugeria_ (_Delesseria_) _sanguinea_ (Plate VIII.) is a large and -beautiful weed, of a blood-red colour, that grows in the lower rock -pools or beyond low-water mark, under the shade of high rocks or hidden -by the olive tangles. Its frond is thin and membranous, with a -well-defined midrib. The spores are contained in globular stalked -conceptacles, usually on one side of the midrib; and the tetraspores may -be seen in pod-like leaflets attached to the bare midrib during the -winter. - -Passing over some of the rarer membranaceous _Rhodymeniaceae_, we come to -the beautiful _Plocamium_, distinguished by its linear compressed -crimson fronds, which are pinnate, with comb-like teeth, the branchlets -being alternately arranged on either side in threes and fours. The -spores are on radiating threads, in globular conceptacles; and the -tetraspores are in the outer divisions of the frond. We have only one -species of this beautiful genus, and that is _P. coccineum_, which is of -such a brilliant colour that it is always a favourite with collectors. - - [Illustration: FIG 251..--_Plocamium_] - -Our last example of the order is _Cordylecladia_ (_Gracilaria_) -_erecta_, with threadlike, cartilaginous frond, irregularly branched and -cellular in structure. The fronds arise from a disc-like root; and bear -spores in thickly-clustered spherical conceptacles, and tetraspores in -lanceolate pods at the tips of the branches, both in the winter. It is a -small weed, and grows principally on sand-covered rocks near low-water -mark. - -The order _Sphaerococcoideae_ contains red or purple sea weeds with -unjointed cartilaginous or membranaceous fronds, composed of many-sided, -elongated cells, with spores in necklace-like strings, lodged in -external conceptacles. The typical genus (_Sphaerococcus_) contains the -Buck's-horn sea weed which grows at and beyond low-water mark on the -south and west coasts, where it is sometimes washed up on the beach -during storms. Its fronds are flattened and two-edged, freely branched, -and the upper branches are repeatedly forked, and terminate in -fan-shaped, cleft branchlets. Both branches and branchlets are fringed -with slender cilia, in which the spores are embedded. It is a handsome -weed, of a bright-red colour and a somewhat coral-like form. - -Allied to this is _Gelidium corneum_, with flattened, horny fronds, -repeatedly pinnate, with the smallest branchlets obtuse and narrower at -the base. The spores are contained in conceptacles near the extremities -of the branchlets, and the tetraspores are imbedded in club-shaped -branchlets. There are a large number of varieties of this species, -differing in form, size, and the mode of branching of the fronds. The -size varies from one to five or six inches, and the colour is red or -reddish green. - -In the genus _Gracilaria_ the frond is thick and horny, and the surface -cells are very small, while the central ones are large. The spores, -formed on necklace-like threads, are enclosed in sessile conceptacles -along the branches, and the tetraspores are imbedded among the surface -cells of the fronds. The only common species is _G. confervoides_, with -cylindrical cartilaginous fronds bearing long thread-like branches, -sometimes reaching a length of two feet. The spore conceptacles are -situated on the slender branches, giving them a knotted or beaded -appearance. The colour is a dark purple, which rapidly fades when the -weed is placed in fresh water or left exposed to the air. Two other -species--_G. multipartita_ and _G. compressa_--are rare. - -_Calliblepharis ciliata_, perhaps more commonly known as _Rhodymenia -ciliata_, has a branching root, short round stem, and a broad, crisp -frond that is generally ciliated. Sometimes the frond is simple and -lanceolate, with small leaf-like appendages on its edge; and sometimes -it is deeply cleft. The spores are arranged in beaded threads in sessile -conceptacles on the marginal leaflets. Another species of the same genus -(_C. jubata_) is very similar in structure, but is of a duller-red -colour, gradually changing to olive green at the tips; and it has its -tetraspores in the cilia only, while in _C. ciliata_ they are collected -in patches in all parts of the frond. Both species grow in deep water, -and are frequently washed up during storms. - -The large genus _Nitophyllum_ contains some beautiful rose-red sea -weeds, with irregularly cleft membranaceous fronds, either veinless, or -with a few indistinctly visible veins only at the base. The spores are -in rounded sessile conceptacles scattered on the surface of the frond; -and the tetraspores occur in clusters similarly scattered. - -One of the species--_N. laceratum_--so called from the torn and jagged -appearance of the frond, is represented on Plate VII. The fronds are -attached to a disc-like root, and are very variable in form, being -sometimes so narrow as to appear almost threadlike. The plant grows on -rocks and large weeds in the lower rock pools and in deep water. In the -same genus we have _N. punctatum_, with broad pink fronds, dotted all -over with spore-conceptacles and dark-red clusters of tetraspores; also -a few other less common species that are seldom seen except after -storms, as they grow almost exclusively in deep water. - -The genus _Delesseria_ contains some beautiful rose-coloured and -reddish-brown weeds with delicate, leaf-like, symmetrical fronds, each -of which has a darker midrib from which issue transverse veins. The -spores are arranged like minute necklaces, and are contained in sessile -conceptacles either on the midrib of the frond or on leaflets that grow -from the midrib. The tetraspores are in clusters which are scattered -over the frond or on its leaflets. The algae of this genus are seldom -found growing between the tide-marks, as they generally thrive in deep -water, but splendid specimens are often washed up on the beach during -storms, especially on the south and south-west coasts. - - [Illustration: FIG. 252.--_Delesseria alata_] - - [Illustration: FIG. 253.--_Delesseria hypoglossum_] - -Among these we may specially mention _D. alata_, known popularly as the -Winged Delesseria, with a dark-red, forked frond, consisting of a -strong midrib, bordered by a wing-like lamina of very variable width, -supported by opposite veins. In this species the clusters of tetraspores -are arranged on each side of the midrib or special leaflets near the -tips of the frond. _D. sinuosa_ is a less common weed, with a disc-like -root and an oblong, cleft and toothed frond, and tetraspores in leaflets -growing from its margin. Another species--_D. hypoglossum_--is -characterised by the leaflets of the midrib bearing still smaller -leaflets in the same manner. - -We have already referred (p. 366) to a sea weed commonly known as the -Dock-leaved Delesseria, the scientific name of which is _Maugeria_ -(_Delesseria_) _sanguinea_. This plant was once included in the present -order, but has been removed on account of the different structure of its -fruit. - -Our next order is the interesting one containing the coral-like weeds, -some of which are so common and so conspicuous in the rock pools. The -order is known as the _Corallinaceae_, and all its species secrete -carbonate of lime, which hides their vegetable structure and gives them -more the appearance of stony corals. - -The typical genus (_Corallina_) includes two weeds with jointed pinnate -fronds, and spore-conceptacles at the tips of the branches with a -terminal pore. - -These and the allied sea weeds are very unlike plants in their general -nature, their stony covering of carbonate of lime hiding all traces of -the delicate cellular structure so characteristic of the various forms -of vegetable life, and especially those of aquatic or marine habit. If, -however, the weed is put into dilute hydrochloric (muriatic) acid the -calcareous matter will be completely dissolved in a minute or two, with -evolution of bubbles of carbonic acid gas; and if a portion of the frond -be then examined in a drop of water under the microscope, the cellular -structure referred to will be seen as well as in any other weed. Another -characteristic of the plant, or rather of the carbonate of lime which it -secretes, is its property of becoming intensely luminous when held in a -very hot flame. Thus if a tuft of coralline be held in the flame of a -Bunsen burner, it will glow so brilliantly as to remind us of the lime -light. Further, if we examine the plant in its natural state, we find -that the carbonate of lime is not secreted uniformly in all parts, but -that the nodes of the jointed frond are free from the stony deposit, and -are therefore flexible. - -Our commonest species--_C. officinalis_--may be found in almost every -rock pool between the tide-marks, growing on rocks, shells, and other -weeds. The joints of the stem and branches are cylindrical or somewhat -wedge-shaped, while those of the branchlets are linear; and the colour -varies from a dark purple to white, the former prevailing in the deep -and shady pools and the depth of tint decreasing according to the amount -of exposure to the bleaching action of the sun. - -A second species (_C. squamata_) is very similar in growth and habit, -but is much less common, and is confined to the neighbourhood of -low-water mark. It may be distinguished from the last by the form of the -segments, which are short and globose in the lower portions of the stem, -and become broader and more flattened towards the tips of the branches. - -Another genus--_Jania_--contains a few coralline weeds that are somewhat -like _Corallina_, but are of a more slender habit and smaller, and have -a moss-like appearance. They may be distinguished by the _forked_ -branching of the slender frond, and by the position of the conceptacles -in the axils of the branches, and not at the tips. _J. rubens_ is a very -common red species that grows in tufts on other weeds. It has -cylindrical segments, longer towards the tips of the branches; while -another and less common one (_J. corniculata_), found principally on the -south coasts, has flattened segments except in the branchlets. - -A third genus of the order--_Melobesia_--contains a very peculiar group -of algae that would certainly never be regarded as plants by those who -did not know them. They are apparently mere solid incrustations of -calcareous matter, without any jointed structure, and often of very -irregular form, covering the surfaces of rocks, shells, or weeds. They -are of varying colours, some prevailing tints being dark purple, lilac, -rose, and yellow; and they are equally variable in form, some being -decidedly lichen-like, some resembling fungoid masses, and others -consisting of superimposed leaf-like layers. They are not weeds to be -pressed for the collector's album, but require storing in boxes or trays -like sea shells. As in the case of the branched corallines, the hidden -vegetable structure may be revealed by dissolving away the carbonate of -lime; and the spore-conceptacles, with terminal pores, may be seen -scattered irregularly over the surface. - -The order _Laurenciaceae_ contains some beautiful pink, red, and purple -weeds with round or flattened branching fronds. They may be known by the -disposition of the tetraspores, which are irregularly scattered over the -branches; and by the pear-shaped spores in rounded capsules. The -typical genus (_Laurencia_) includes an abundant weed (_L. pinnatifida_) -which was formerly eaten in parts of Scotland, where it is known as the -Pepper Dulse on account of its peppery taste. It is found in the tide -pools on many parts of the coast, and varies much in size, form, and -colour according to the situation in which it grows. The plants which -are exposed to the air at low tide are usually small, and of a pale -brown colour, while those found in the permanent rock pools at or near -low-water mark are larger and dark brown or purple. The fronds are flat -and cartilaginous, with stout branches bearing alternate divided -branchlets, which are blunt at the tips. The stem itself is unbranched. -The spores are pear-shaped, in oval cells; and the tetraspores are -irregularly distributed near the tips of the branches. - -Another common species, known as the Tufted Laurencia (_L. caespitosa_), -is very similar to the last mentioned, and is not easily distinguished -from it. It is, however, of a bushy habit, while _L. pinnatifida_ is -flat, and its fronds are less firm. This species grows on rocks and -stones between the tide-marks, and is variegated in colour from a pale -green to a purple. - - [Illustration: FIG. 254.--_Laurencia pinnatifida_] - - [Illustration: FIG. 255.--_Laurencia obtusa_] - -A third species--the Obtuse Laurencia (_L. obtusa_)--is widely -distributed on our coasts, and may be known by its thread-like bipinnate -fronds with short blunt branchlets, cup-shaped at the tips. It is -parasitic on various other weeds. - -The genus _Lomentaria_ includes a few weeds with tubular fronds that are -constricted at intervals, and divided internally by transverse -membranous septa. The spores are pear-shaped and lodged in spherical -cells; and the tetraspores are scattered on the surface of the branches. -One species called the salt-wort (_L. kaliformis_) is widely -distributed. Its colour is pink, sometimes yellowish, and it grows on -rocks or stones, and sometimes on other weeds. It may always be known by -its spherical fruit, without any visible opening, containing crimson -pear-shaped spores. Another species (_L. ovalis_), found on the coasts -of Devon and Cornwall, may be recognised by its _solid_ branched frond -and little oval leaf-like branchlets, which are hollow, jointed, and -divided by partitions internally. - -The one remaining order of the red-spored sea weeds is the -_Rhodomelaceae_, which has either a jointed or a many-tubed axis, and the -surface divided up into little definite areas. The fronds are either -leafy or thread-like, and the prevailing colours are red, reddish brown, -and purple. The spores are pear-shaped, and occupy the terminal cells of -tufted threads in external, globular, or rounded conceptacles; and the -tetraspores are lodged in special receptacles, or in special modified -branchlets. The order contains some of our most beautiful weeds, while -some of its members are of a very dark colour and unattractive form. - -The typical genus--_Rhodomela_--contains two British species with -dark-red, cartilaginous fronds, cylindrical, unjointed, and irregularly -branched; and the tetraspores imbedded in the tips of the slender -branchlets. The name of the genus signifies 'red-black,' and is applied -on account of the tendency of the dark-red fronds to turn black when -dried. - -_R. subfusca_ is very common on all our coasts. It has rigid fronds, -irregularly branched; and is in its best condition during the summer. -The other species--_R. lycopodioides_--has long undivided branches with -thickly-set and freely-divided branchlets. - -When turning over the fronds of different species of the larger olive -weeds we commonly find them more or less clothed with tufts of -filamentous plants, sometimes small and delicate, and sometimes larger -and of more robust growth, varying in colour from a purplish brown to a -dark violet, and the articulated filaments more or less distinctly -striated with parallel lines. These weeds belong to the genus -_Polysiphonia_, and derive their generic name from the fact that the -threadlike fronds are composed of several parallel tubes. The surface -cells are also arranged in regular _transverse_ rows, and it is this -which gives rise to the striated appearance above referred to. - -Over twenty species of _Polysiphonia_ are to be found on our shores, -where they exist at all levels between the tide-marks. They are -distinguished from one another partly by their general form and mode of -growth, and also by the number of tubes in their threadlike fronds. - -Although they would not always be considered as lovely weeds and are -often anything but beautiful when dried and mounted, yet in their fresh -condition they are generally pretty objects, and their microscopic -structure is particularly interesting on account of the beautiful and -symmetrical arrangement of their siphons and tubes. - -If the reader is the fortunate possessor of a compound microscope, it -will amply repay him to make transverse sections of the fronds for -examination. A short length of the frond should be inserted into a slit -cut in a piece of carrot or elder pith; and, while thus supported, very -thin transverse sections may be easily cut with a sharp razor, care -being taken to keep both razor and object very wet during the process. -Allow the sections to fall into a vessel of water as they are cut, and -then select the thinnest for examination, mounting them in a drop of -water in the usual way. - -Specimens in fruit should always be obtained when possible, so that the -nature of the fructification may be observed. Two kinds of spores may be -seen in each species, but, as is usually the case with the red sea -weeds, on different plants. Some are small pear-shaped bodies, enclosed -in oval cells at the tips of the fronds; and the others are arranged in -clusters of four in swollen parts of the threads. - -The commonest species is _P. fastigiata_, which may be found in -abundance as bushy brownish tufts on the fronds of _Fucus nodosus_ (p. -386). A transverse section of this weed is a very beautiful microscopic -object. It resembles a wheel, with a dark centre to the nave, and -several spokes enclosing about sixteen regularly arranged tubes. The -swollen tips of fronds should also be examined for the urn-shaped cells -containing the spores; and if a gentle pressure be applied to the -cover-glass with a needle, the little pear-shaped spores may be -expelled. The other kind of spores may be found near the bases of the -branches on different plants. - - [Illustration: FIG. 256.--_Polysiphonia fastigiata_] - -Among other species we may briefly mention--_P. parasitica_, sometimes -found near low-water mark, growing in little feathery tufts of a -bright-red colour, on the lichen-like _Melobesia_ or on corallines. It -has seven or eight parallel siphons in its fronds, all regularly -arranged round a small central space. - -_P. Brodiaei_ is moderately common on our coasts. This is a large brown -species, with seven siphons surrounded by a thick cellular layer which -conceals the articulations and is too opaque to allow the siphons to be -seen without dissection. Its branches, which are alternate, bear short -tufts of delicate branchlets. - - [Illustration: FIG. 257.--_Polysiphonia parasitica_] - - [Illustration: FIG. 258.--_Polysiphonia Brodiaei_] - -_P. byssoides_, so called on account of the pink filaments that fringe -the fronds, has also seven siphons. It is a large and beautiful weed, -moderately common on our coasts, of a bright-red colour, with -conspicuous fructification. The branches are alternate, and the -branchlets are clothed with the byssoid filaments above referred to. - -_P. violacea_ is of a reddish-brown colour, with long silky alternate -branches, and four siphons. It receives its specific name from the fact -that it turns to a violet colour when dried. - -_P. nigrescens_ has, as the specific name implies, blackish fronds, and -these are freely branched. The tubes, about twenty in number, are flat, -and are arranged round a large central space. - - [Illustration: FIG. 259.--_Polysiphonia nigrescens_] - -Our last example--_P. atro-rubescens_--is of a dark reddish-brown -colour, with rigid and densely-tufted fronds. It has twelve tubes, -arranged _spirally_ round a central cavity. It is common in the lower -rock pools of some coasts. - -In the same order we have the genus _Chondria_, so called on account of -the cartilaginous nature of its thread-like fronds. These are pinnately -branched, and the club-shaped branchlets taper below. The main stem is -jointed and contains many siphons. The genus includes a common species -(_C. dasyphylla_), with thick fronds, that is found in shallow sandy -pools, where it grows on pebbles, shells, or on other weeds, the colour -varying from pink to a dark purple. _C. tenuissima_ is a very similar -weed, but may be distinguished by its more slender growth, and by its -long, rod-like simple branches, clothed with slender, bristle-like -branchlets that taper from the middle towards both ends. - -On the northern coasts of Britain we may meet with _Odonthalia dentata_, -the blood-red fronds of which are tufted, and arise from a hard, -disc-like root. Each frond projects from the axil of a tooth-like -projection of the main stem, and is deeply pinnatifid, with a distinct -midrib in the lower part, and thin and membranaceous towards the tip. -The pinna are dentate, and the spores are in stalked, oval conceptacles -in the axils of the pinnae. The tetraspores are similarly situated in -stalked, lanceolate leaflets. - -The weeds of the genus _Rytiphlaea_ are very similar to some of the -_Polysiphonia_, the axis of the frond being jointed and transversely -striped, but the nodes are less distinct and are not constricted. They -are shrub-like weeds, with tufted spores in oval, sessile conceptacles; -and tetraspores in spindle-shaped branchlets or in little pod-like -leaflets. The principal British species are:-- - -_R. pinastroides_, a much-branched and shrub-like weed, of a dull-red -colour, which turns black when the plant is dried. The branches have -rigid, hooked branchlets arranged in such a manner as to give a combed -appearance. This species occurs on the south coast, and is in its prime -in very early spring. It is often rendered peculiarly interesting by the -colonies of zoophytes and the patches of _Melobesia_ with which it is -more or less covered. - -_R. fruticulosa_ is another shrubby species, with irregularly branched, -interlacing stems. It is to be found in the rock pools of the south and -west coasts, and is of a deep-purple colour in the deeper shady pools, -but varying to a yellowish tint where exposed to the full light of the -sun. The whole of the frond is covered with hooked branchlets, and the -weed is peculiar for the fact that, when removed from the rock pool, -little glistening beads of water remain attached to the tips of the -terminal branches. The tetraspores are situated in distorted branchlets. - -_R. thuyoides_ has creeping, fibrous roots, from which arise the erect -stems of purple-brown, branched fronds with short spine-like branchlets. -It occurs in the shallower rock pools, where it grows attached to rocks -or to other weeds. It is in its best condition during the summer, when -we may see its oval spore-conceptacles and the tetraspores in distorted -branchlets. - -The last genus of the _Rhodomelaceae_ is _Dasya_, which contains some -very graceful and brightly-coloured weeds that are found principally on -our south and west coasts. In these the fronds are thread-like or -flattened, branched, and without visible joints. The main stem contains -many tubes, but the tubular structure is hidden by the outer layer of -cells; and the branchlets, which are slender, one-tubed, and jointed, -bear little lanceolate pods that contain the tetraspores. - -_D. ocellata_ has small tufted fronds, about two or three inches long, -attached to a small discoid root. The main stems are densely covered -with slender, forked branchlets, those at the tips being clustered in -such a manner as to recall the eye-like marks of the peacock's tail. It -grows principally on the mud-covered rocks beyond low-water mark, and is -not by any means a common weed. Another species--_D. arbuscula_--is -somewhat plentiful on parts of the Scottish and Irish coasts, but -comparatively rare in South Britain. It has a small disc-like root, and -stems thickly clothed with short branchlets. The spore-conceptacles are -tapering, on short stalks, and the tetraspores are contained in pointed -pods on the branchlets. The scarlet Dasya (_D. coccinea_) may be -commonly seen at and beyond low-water mark during late summer, at which -time splendid specimens may also be found on the beach after storms. Its -stem is thick, proceeding from a discoid root, and is clothed with -hair-like filaments; and the branches bear short, slender branchlets -that give them a feathery appearance. The tetraspores are contained in -elongated, pointed, and stalked pods. There are three other species on -the British list, but they are not common weeds. - -The last of the three great groups into which the sea weeds are divided -is the _Melanospermeae_, or olive-spored algae, the different species of -which are generally very readily distinguished by their olive-green or -olive-brown colour, for the whole plant, as well as the spores, contains -a dark olive colouring matter, in addition to the chlorophyll which is -always present. - -These weeds are often very large, frequently attaining a length of -twenty feet or more in our seas, and from eighty to a hundred feet in -warmer parts; and, being also extremely abundant almost everywhere, they -form a most conspicuous feature of the shore. They usually grow on rocks -and stones, from high-water mark to moderately deep water, but some of -the smaller species are pseudo-parasitic on other algae. - -Their form is most varied. Some are minute filamentous plants, -consisting only of slender jointed threads, and others are mere -shapeless masses; but many of the larger species exhibit a great -differentiation of form, having root-like and stem-like structures, and -expansions that resemble leaves. The latter, too, often have large -vesicles that contain air, sometimes arranged singly along the median -line of the frond, or in lateral pairs, or a single vesicle at the base -of each segment of the thallus. - -The air vesicles, of course, serve to buoy up the plant when it is -submerged, thus enabling the light to penetrate between its fronds to -lower portions; and when the plants have been wrenched from their -moorings by the force of the waves, they immediately rise to the surface -and are drifted on to the shore or accumulate in the eddies of the -surface currents. In this way immense masses of floating weeds are -formed, the most remarkable being that of the Sargasso Sea in the North -Atlantic. - -Like other algae, the melanospores grow by a continued process of -cell-division, and when portions of the thallus are worn away during -stormy weather, they are renewed by the same process. - -The cell-walls of many species are very mucilaginous, the gelatinous -covering being either the result of the degeneration of the cell-walls -themselves, or the secretion of special glands. - -As with the last division, the reproduction of the melanospores may be -asexual or sexual. The asexual spores, which are not motile, are formed -in some of the surface cells of the thallus. The male and female sexual -organs, called respectively the _antheridia_ and the _oogonia_, are -produced in cavities on special portions of the thallus, both kinds -being often formed in the same cavity or depression. The latter contains -from one to eight little bodies called _oospheres_. These escape and -float passively away when the wall of the oogonia ruptures. The -antheridia are also discharged whole, but the minute fertilising -elements (_antherozoids_), which are eventually set free from them, -swarm round the oospheres, being attracted by the latter. Soon one of -the antherozoids enters the oosphere, and from that moment all -attraction ceases, the remainder of the antherozoids floating passively -away; and the oosphere, previously naked and barren, now develops a -cell-wall, and becomes the fertile progenitor of a new plant. - -Starting with the lowest of the melanospores, we first deal with the -order _Ectocarpaceae_, which is characterised by olive, thread-like, -jointed fronds, with spores on the branchlets or embedded in their -substance; two kinds of spores often existing in the same plant. - -The typical genus (_Ectocarpus_) contains many British species, though -several of them are rare. They are soft and flexible weeds, generally of -a dull olive colour, with slimy, tubular fronds, and grow in tufts on -other weeds or on mud-covered rocks. Spores of various shapes are -scattered over the fronds, and are also contained in pod-like bodies -formed of the branchlets. This latter feature is, perhaps, the best -distinguishing characteristic of the genus, but it is not an easy matter -to identify the several species it contains. - -_E. tomentosus_ is very commonly found on _Fucus_ and other weeds, where -it forms matted tufts of slender threads of a yellowish-brown colour. -The threads are clothed with transparent cilia, and together form a -dense, spongy mass. The spores are contained in narrow pods supported on -short stalks. _E. littoralis_ is another common species, of a very -unattractive appearance. It grows in matted tufts on other weeds, on -rocks, mud, or any submerged object, and its spores are contained in -linear swellings of the branches. This species thrives well in brackish -water, and may be seen far up certain tidal rivers. - - [Illustration: FIG. 260.--_Ectocarpus granulosus_] - - [Illustration: FIG. 261.--_Ectocarpus siliculosus_] - - [Illustration: FIG. 262.--_Ectocarpus Mertensii_] - -Among the other species we may briefly mention _E. granulosus_, an -abundant and beautiful weed that grows in feathery tufts on rocks and -weeds, with elliptical, stalkless pods, quite visible to the naked eye, -freely distributed over the opposite branchlets; _E. siliculosus_, a -pale olive, parasitic species with lanceolate stalked pods, pointed and -striped; _E. sphaerophorus_, a small, soft, brownish-yellow species, with -dense matted branches and spherical pods arranged either opposite to one -another or to a branchlet; and _E. Mertensii_, a pretty species that -grows on muddy rocks, freely branched but not matted, and having pods -enclosed by the branchlets. The last species is rare, but may be found -in Cawsand Bay and a few other localities about Plymouth Sound. The -genus includes several other species, but all these are more or less -rare. - -In the genus _Myriotrichia_ we have two parasitic species with fragile, -hair-like, jointed fronds bearing simple straight branches that are -covered with transparent fibres. In these the spore-cases are rounded -and transparent, and arranged along the main threads; and the dark olive -spores are readily visible within. In _M. filiformis_ the branchlets are -short, and clustered at intervals, thus giving a somewhat knotted -appearance to the threads, and both branches and branchlets are covered -with long fibres. The other species--_M. clavaeformis_--is very similar, -but may be distinguished by the arrangement of the branchlets, which are -not clustered at intervals, but are distributed regularly, and are -longer towards the tip of the frond, giving the appearance of minute -fox-brushes. - - [Illustration: FIG. 263.--_Sphacelaria cirrhosa_] - - [Illustration: FIG. 264.--_Sphacelaria plumosa_] - -The genus _Sphacelaria_ contains several British weeds with rigid -branched and jointed fronds, most easily distinguished by the tips of -the branches, which are flattened, contain a granular mass, and have a -withered appearance. _S. cirrhosa_ forms hair-like tufts of slender -fibres with closely-set branches on small weeds, the tufts varying from -a quarter of an inch to over an inch in length. The fronds are naked at -the base, and the spore-cases, which are globular, are arranged on the -branches. _S. filicina_ is, as its name implies, of a fern-like -appearance, but is very variable in form. Its fronds vary from one to -three inches in length, and the spores are arranged singly in the axils -of the branchlets. Excluding some rarer species we mention one other -example--the broom-like _S. scoparia_, the frond of which is coarse and -very rigid, of a dark-brown colour, two or three inches long, with the -lower portion clothed by woolly fibres. Its spores are arranged in -clusters in the axils of the branchlets. - - [Illustration: FIG. 265.--_Sphacelaria radicans_] - -The last genus of the _Ectocarpaceae_ is _Cladostephus_, which grows in -dark-green tufts, usually five or six inches long, in the deeper tide -pools. The fronds are cylindrical, branched, inarticulate, and rigid; -and the branchlets, which are short and jointed, are arranged in whorls. -The spores are situated in short accessory branchlets, or in masses at -the tips of the ordinary branchlets. _C. verticillatus_ is a very common -species, the whorled branchlets of which are deciduous in winter, when -the accessory branchlets that bear spores begin to develop. _C. -spongiosus_ is densely clothed with branchlets, and is of a bushy habit, -with a very spongy feeling. It is by some regarded as a variety of _C. -verticillatus_. - - [Illustration: FIG. 266.--_Cladostephus spongiosus_] - - [Illustration: FIG. 267.--_Chordaria flagelliformis_] - -The order _Chordariaceae_ is characterised by a compound gelatinous or -cartilaginous frond, consisting of interlacing horizontal and vertical -threads. The spores are not external as in the _Ectocarpaceae_, but -contained in cells in the substance of the frond. In the typical genus -the frond has a cylindrical, branched, cartilaginous axis, surrounded by -whorls of club-shaped threads and slender gelatinous fibres. We have -only one common species--_Chordaria flagelliformis,_ the fronds of which -are from four to twenty inches long, of uniform thickness throughout, -with long, glistening, soft and slimy branches among which the spores -are disposed. It may be found in rock pools at almost all levels. - -In the genus _Elachista_ there are some very small and peculiar weeds -that are almost sure to be overlooked by inexperienced collectors. They -are parasitic, and are composed of two kinds of jointed threads, the -inner of which are forked and combined into a tubercle, while the outer -are simple and radiate from the tubercle. The spores are attached to the -inner threads. The largest species (_E. fucicola_) is parasitic on -_Fucus_, growing in brush-like tufts about an inch long. Some of the -smaller ones are mere star-like tufts of no attractive appearance, and -would be disregarded as troublesome parasites by most young collectors, -but all of them are very interesting objects for the microscope. - -The members of the genus _Myrionema_ are similarly liable to be -neglected, for they are minute parasites appearing only as decaying -spots on larger weeds, but nevertheless form interesting studies for the -microscope. Like the last group, they have two sets of jointed fibres, -the inner being branched, and spread over the surface of the plant on -which it grows, while the outer are simple and stand out at right -angles, but all are united into a rounded mass by a gelatinous -substance. Perhaps the best known is _M. strangulans_, which infests -_Ulva_ and _Enteromorpha_, producing the appearance of small decaying -spots. - -In the genus _Leathesia_ we have other unattractive weeds, the jointed -and forked threads of which are all united together into tuber-like -fronds that are common on rocks and weeds between the tide-marks. There -are three or four species, all similar in general appearance, with the -spores distributed among the outer threads. These weeds cannot be -satisfactorily pressed and dried in the usual way, and should be -preserved in formaldehyde or dilute spirit, when they will always be -available for microscopic examination. - -The last genus of the _Chordariaceae_ is _Mesogloia_, so called because -the central axis of loosely-packed, interlacing threads is covered with -gelatinous substance. Around this axis there are radiating, forked -threads which are tipped with clubbed and beaded fibres among which the -spores are distributed. One species (_M. vermicularis_), common in most -rock pools, is of a wormlike form, of a dirty olive or yellow colour, -with soft, elastic fronds growing in tufts from one to two feet long. -_M. virescens_, also a common species, is of a pale greenish or olive -colour, and very soft and slimy. Its stem is round and slender, freely -branched, with short, simple branchlets. - -The order _Dictyotaceae_ contains the olive weeds with inarticulate -fronds, and superficial spores disposed in definite lines or spots. In -the typical genus (_Dictyota_) the frond is flat and forked, somewhat -ulva-like and ribless, and the spores are produced in little superficial -discs just beneath the cuticle. There is only one British species--_D. -dichotoma_--but that is a very common one, and it assumes a great -variety of forms as regards the shape and division of its fronds -according to the situation in which it grows, the fronds being broadest -and strongest in the deepest water. The root is covered with woolly -fibres, and the frond is regularly forked. - -One of the most interesting algae of this order is the Turkey-feather -Laver (_Padina pavonia_), which is the only British representative of -its genus (see Plate VII.). Its very pretty fan-shaped fronds are of a -leathery nature, curved, fringed along the upper margin, and marked with -concentric lines. They often bear small leaflets, and are partially -covered with a powdery substance which renders them beautifully -iridescent when in the water. The root has woolly fibres, and the spores -are arranged in lines along the upper margin. This weed seems to be -confined to the south coast, where it may often be seen in the deeper -tide pools; though in some of the sandy bays of the Isle of Wight it may -be seen in shallow pools, and even in places left exposed to the air at -low tide. - -The genus _Zonaria_ contains a British species (_Z. parvula_) that -covers the rocks in round patches; and though moderately common is not -very frequently seen by collectors on account of the fact that it grows -in the deep crevices of rocks at or near low-water mark. Its frond is -flat and membranaceous, more or less divided into lobes, without veins, -and rather obscurely divided into concentric zones. It is attached to -the rock by fibres that proceed from the under surface of the frond, and -the spores are arranged in clusters beneath the superficial cells. - -_Cutleria multifida_, though not very abundant, is to be found on most -of our coasts; but since it grows almost exclusively beyond low-water -mark, it should be looked for on the beach after storms, or in the -fishermen's nets. The frond is olive-green, fan-shaped, rather thick, -and irregularly divided into forked branches; and it has a beautifully -netted surface. The spore-cases may be seen scattered over the surface -of the frond as so many black dots, and the antheridia are elongated, -cylindrical bodies attached to tufted filaments on all parts of the -frond. - -In the genus _Stilophora_ the root is discoid; the frond cylindrical, -hollow, and branched; and the spores arranged in clusters over the -surface. One species (_S. rhizodes_) is occasionally to be seen on the -south coast. It is of a yellowish colour, from six to twenty inches -long, and may be known by its long thread-like branches, with scattered, -forked branchlets, and by the wart-like projections of the stem which -contain the spores. This weed is often the source of some disappointment -to the collector, for it soon turns to a jelly-like mass when removed -from the water, and should therefore be mounted as soon as possible -after it has been collected. - -The fennel-like _Dictyosiphon foeniculaceus_ is abundant in tide pools, -where it may be seen in its best condition during spring and early -summer. Its root is a small disc, the frond is tubular, thread-like and -branched, and the branches bear hooked branchlets. The spores are naked, -and distributed either singly or in clusters over the surface of the -frond. - -Our next genus--_Punctaria_--contains a few British species with a -shield-shaped root, and a flat, membranous, undivided frond, without a -midrib, and having the spores disposed as minute dots over the surface. -A plantain-like species (_P. plantaginea_) has broad, leathery, -lanceolate fronds, of a dark olive-brown colour, usually from six inches -to a foot in length. Two other weeds--the broad-leaved _P. latifolia_ of -the tide pools, and the slender, tufted _P. tenuissima_, which is -parasitic on _Zostera_ and soe algae, are sometimes regarded as mere -varieties of _P. plantaginea_. - -In the genus _Asperococcus_ the root is shield-shaped, and the frond is -a membranous tubular sac of two distinct layers. The colour is pale -green, and the general appearance very similar to that of _Ulva_. The -spores are arranged in small oblong clusters which appear as dark dots -on the surface of the frond. _A. compressus_ has slightly swollen flat -fronds of a linear lanceolate form, tapering below. It grows in deep -water, but is often washed up during storms. A second species--_A. -Turneri_--has large, puffy, green fronds, contracted at intervals, and -grows in tufts on rocks between the tide-marks, being specially partial -to muddy shores. The genus also includes the prickly _A. echinatus_, the -long, thin fronds of which grow in dense tufts in deep water. - -The last genus of the order is _Litosiphon_, a parasitic group -characterised by a cylindrical, cartilaginous, unbranched frond, with -scattered, naked spores. A very small species (_L. pusillus_) with -tufted green fronds grows parasitic on the fronds of _Chorda_ and the -stems of _Laminaria_. It is only two or three inches long, has a -reticulated surface, and is covered with minute jointed fibres. A still -smaller species (_L. laminariae_), seldom exceeding half an inch in -length, forms brown tufts on _Alaria_, and the rounded apex of its frond -is covered with minute fibres. - -The order _Laminariaceae_ contains olive, inarticulate algae, mostly of -large size, and generally growing in deep water beyond the tide-marks. -Their spores are superficial, either covering the whole surface of the -frond or collected into indefinite cloudy patches. - - [Illustration: FIG. 268.--_Laminaria bulbosa_] - - [Illustration: FIG. 269.--_Laminaria saccharina_] - -The typical genus (_Laminaria_) is characterised by flat leathery, -ribless fronds, either simple or cleft, and supported on a stem which is -often very thick and strong. The old laminae fall off every year, and are -replaced by new fronds. The well-known Tangle or Sea Girdle (_L. -digitata_), is a very common species on the rocks just beyond low-water -mark. It has a very thick, solid, cylindrical stem, and an oblong -leathery frond which is entire when young but deeply cleft later. Small -specimens may be found just above low-water mark, but fine large ones -are commonly washed up on the beach. Although this weed may not be -regarded as an acquisition from the collector's point of view, it will -generally repay a careful examination, as it frequently bears rare -parasitic species. The other common species are the Furbelows (_L. -bulbosa_), known by its flat stem with waved margin, oblong frond cleft -into narrow strips, and the hollow bulb or tuber just above the root; -and the Sugared Laminaria (_L. saccharina_) characterised by a round -solid stem, and a lanceolate, entire, membranous frond. The last species -is the one most commonly used by the sea-side cottager as a weather -indicator. - - [Illustration: PLATE VIII. - - SEA-WEEDS - - 1. Chorda filum - 2. Fucus vesiculosus - 3. Fucus canaliculatus - 4. Delesseria (Maugeria) sanguinea - 5. Rhodymenia palmata - 6. Chondrus crispus - 7. Ulva lactuca] - - [Illustration: FIG. 270.--_Alaria esculenta_] - -_Alaria esculenta_ is an edible species known as the Badderlocks in -Scotland, and also locally as the Henware, Honeyware, and the Murlins. -It has a fibrous root, and a stalked, lanceolate, entire frond with a -distinct midrib throughout. The stem is winged with finger-like -leaflets, in which the spores are arranged in oblong clusters. - -In the genus _Chorda_ the frond is a simple, cylindrical tube, divided -internally by numerous transverse membranes, and the spores are -distributed over the surface. The commonest species is _C. filum_ (see -Plate VIII.), the frond of which is very slimy, and often from ten to -twenty feet in length. In its young state it is covered with gelatinous -hairs, but these are worn off as the plant develops. A smaller species -(_C. lomentaria_) is sometimes found on our shores. Its fronds are -constricted at intervals, taper at the tip, and grow in tufts. It is -seldom more than a foot long, and is not of a slimy nature. - - [Illustration: FIG. 271.--_Sporochnus pedunculatus_] - -The _Sporochnaceae_ have inarticulate, thread-like fronds, and the spores -are contained in oblong, stalked receptacles, each of which is crowned -with a tuft of slender jointed filaments. The typical genus contains -only one British species--_Sporochnus pedunculatus_--and even that is by -no means common. It is, however, a very pretty weed of a delicate -texture and pale olive-green colour. Its stem is long and slender, -pinnately branched, and the branches bear numerous small thread-like -tufts. - -The same order contains the genus _Desmarestia_, in which the frond is -long and narrow, thread-like or flattened, with a tubular jointed -thread running through it. Young specimens have marginal tufts of -branching filaments. The species decay very rapidly after removal from -the water, and should therefore be dried and mounted as quickly as -possible. _D. ligulata_, so named from the flat, strap-like frond, is -common on all our coasts. It is pinnately branched, and all the branches -and branchlets taper towards both ends. _D. viridis_ has a cylindrical, -thread-like and freely-divided frond, with opposite branches and -branchlets. It occurs more commonly on the northern shores. - - [Illustration: FIG. 272.--_Desmarestia ligulata_] - -The last order of olive-spored weeds is the _Fucaceae_, some species of -which are so abundant between the tide-marks, from high-water to -low-water levels, that they form a very important characteristic of our -shores. They are mostly large, tough, and leathery weeds, without -joints, and the spores are contained in spherical receptacles embedded -in the substance of the frond. - -In the typical genus--_Fucus_--the root is a conical disc, and the frond -flat or compressed and forked. Most of the species are furnished with -one-celled air-vessels in the substance of the frond, and these serve to -buoy up the plants and keep them more or less erect when submerged. The -spore-receptacles are usually embedded near the tips of the branches, -but are sometimes borne on special branches or shoots. They are filled -with a slimy mucus and contain a network of jointed filaments. The weeds -are very hardy, capable of withstanding long exposures to air and sun, -and are sometimes to be found _above_ high-water mark, where they are -watered only by the spray of the waves for a brief period at intervals -of about twelve hours. Although they are not usually looked upon as -ornaments in the collector's herbarium, they will repay examination for -the tufts of smaller and more beautiful weeds to which they often give -attachment and shelter. - -Four species are common on our coasts, and these may be readily -distinguished by the most cursory examination. The Serrated Wrack (_F. -serratus_) has a flat, forked frond with toothed edges and a strong -midrib, ranging from one to four feet long, and no air-vessels. The -Knotted Wrack (_F. nodosus_--Plate VII.) may be known by its flattened, -thick and narrow frond, without a distinct rib, from one to five feet -long. The branches are narrow at the base, pointed at the tip, and are -jointed to short projections on the main stem; and both these and the -main stem have very large oval air-vessels. The spore-receptacles are -mounted on slender stalks which arise from projections on the branches, -and are of a bright yellow colour when mature. This species does not -grow so near to high-water mark as do the others. Another species, the -Twin-Bladder Wrack (_F. vesiculosus_--Plate VIII.)--is abundant -everywhere along the coast, and is largely used by agriculturists both -as manure and as fodder for cattle. The frond is flat, with a distinct -midrib, and a non-serrated edge. Air-vessels are not always present, but -when they are they usually occur in pairs, one on each side of the -midrib, and are globular in form. The spore-receptacles are situated at -the tips of the branches, are full of mucus, and are frequently forked. -The last of the common species is the Channelled Wrack (_F. -canaliculatus_--Plate VIII.), distinguished by a narrow frond, rounded -on one side and channelled on the other. It has no midrib or -air-vessels, and the fruit is contained in forked receptacles at the -tips of the branches. This is the smallest of the genus, and may be -found at all levels between the tide-marks. Stunted specimens may also -be seen in situations where they are never submerged, but watered only -by the spray of the highest tides. - - [Illustration: FIG. 273.--_Himanthalia lorea_] - -The genus _Himanthalia_ provides us with a single species (_H. lorea_) -which is very peculiar on account of the small size of the frond as -compared with the enormous dimensions of the spore-receptacles. The -young frond is a pear-shaped sac which soon becomes flattened into a -hollow disc. This disc then becomes solid, and concave above, and from -its centre there arises a bi-forked, strap-like receptacle that often -reaches a length of three or four feet, and may be mistaken for the -frond of the weed by those who do not take the trouble to examine it. -This weed is commonly known as the Sea Thong. - -Belonging to the genus _Cystoseira_ we have a few well-known weeds with -conical disc-roots, and shrubby fronds with woody stem and alternate -branches. The air-cells are in the substance of the frond, and the -spore-receptacles at the tips of the branches. One of the species (_C. -ericoides_) is of a heath-like habit, with a short, woody stem, and -slender branches bearing hooked, leaf-like branchlets. Its air-cells are -small, and are arranged singly near the tips of the branches; and the -spore-receptacles are cylindrical, with hooked points. This weed is -common on the south and west coasts, and may be readily distinguished by -the beautiful iridescence it displays when in the water. _C. fibrosa_ is -very similar in general form, but is larger, and the air-vesicles are -more conspicuous. It is not iridescent when in the water. A third -species is named _C. granulata_ from the rough and knobby appearance of -the stem, due to numerous oval projections, from some of which spring -the slender, much-divided branches. The air-vesicles are arranged in -groups of two or three, and the spore-receptacles are at the ends of the -branchlets. Our last example is _C. foeniculacea_, found on the south -coast only, and readily distinguished by the numerous blunt spines that -cover its long branches. The air-vesicles are narrow and pointed, and -situated just below the forkings of the branchlets. - - [Illustration: FIG. 274.--_Cystoseira ericoides_] - -We conclude our _resume_ of the British sea weeds with a short -description of the Podded Sea Oak (_Halidrys siliquosa_), which grows in -the tide pools from high-water to low-water mark, the specimens -inhabiting the shallow pools being only a few inches long, while those -that grow in deep water often reach a length of three or four feet. It -is an olive, shrub-like weed, with a conical, disc-like root that -adheres very firmly to the rock, and a pinnately-branched frond with -leaf-like branchlets. The air-vesicles are cylindrical and pod-like, -divided internally into about ten cells, and the spores are contained in -globular receptacles at the tips of the branchlets. - -The young algologist will probably meet with many difficulties in his -attempts to classify his sea weeds and name the various species in his -collection. In dealing with an unknown weed we strongly recommend him to -first determine the order to which it belongs. The genus should next be -settled; and then, if possible, the species. It must be remembered, -however, that he who has made himself acquainted with the principles of -classification has done good work, and that it is far better to be able -to arrange the weeds into properly-classified groups than to merely -learn the names of the different species without regard to the relations -which they bear to one another. The following table will probably assist -the reader in the determination of the orders, but it must be remembered -that a microscope will often be necessary for the examination of the -spores and the minute structure of fronds. - - - CLASSIFICATION OF SEA WEEDS - - =A.= =Chlorospermeae=--Green-spored weeds. Fronds usually - grass-green, and filamentous or membranous. - - 1. _Confervaceae_--Frond thread-like, composed of cylindrical - cells placed end to end. Spores very minute, formed - within the cells. - - 2. _Ulvaceae_--Frond grass-green or purple, flat or tubular. - Spores minute, ciliated, formed in the cells of the - frond. - - 3. _Siphonaceae_--Frond a single, thread-like, branching cell, - or a spongy mass of many such cells. - - =B.= =Rhodospermeae=--Red-spored weeds. Spores in globular - conceptacles. Tetraspores (four-clustered spores) in - globular or cylindrical cells. Frond red, reddish - brown, or purple. - - 4. _Ceramiaceae_--Frond thread-like, jointed, one-siphoned, and - more or less covered with a layer of cortical cells. - Spores grouped in transparent, membranous sacs, - sometimes surrounded by a whorl of short branchlets. - - 5. _Spyridiaceae_--Frond thread-like, jointed, one-siphoned, - more or less covered with small cells. Spores formed in - the upper cells of branched, jointed, radiating - threads, enclosed in a cellular membrane in external - conceptacles. - - 6. _Cryptonemiaceae_--Frond more or less cartilaginous, composed - of numerous jointed threads compacted by gelatine. - Spores grouped without order in internal cells or in - external conceptacles. - - 7. _Rhodymeniaceae_--Frond inarticulate, membranaceous, composed - of polygonal cells, the surface cells forming a - continuous layer. Spores in beaded threads in external - conceptacles. - - 8. _Wrangeliaceae_--Frond inarticulate, thread-like, traversed - by a jointed tubular axis. Spores formed in the - terminal cells of clustered, branching, naked threads. - - 9. _Helminthocladiae_--Frond cylindrical, gelatinous, composed - of filaments imbedded in gelatine. Spores formed on - branching, radiating threads that are enclosed in the - frond without conceptacles. - - 10. _Squamariae_--Frond lichen-like, rooted by under surface, - composed of _vertical_ filaments imbedded in firm - gelatine. Spores in beaded threads in wart-like - projections. - - 11. _Spongiocarpeae_--Frond cylindrical, branching, - cartilaginous, composed of netted filaments imbedded in - firm gelatine. Spores large, in radiating clusters in - wart-like excrescences. - - 12. _Gelidiaceae_--Frond cartilaginous, inarticulate, composed - of hair-like filaments. Spores attached to slender - threads in internal conceptacles. - - 13. _Sphaerococcoideae_--Frond leaf-like or thread-like, - inarticulate, cellular. Spores formed in beaded threads - in external conceptacles. - - 14. _Hapalidiaceae_--Frond minute, calcareous, composed of a - single layer of cells. - - 15. _Corallinaceae_--Frond calcareous. Spores in tufted threads - at the bases of the conceptacles. - - 16. _Laurenciaceae_--Frond rounded or flattened, branching, - inarticulate, cellular. Spores in external oval or - globular conceptacles. Tetraspores irregularly - scattered over the branches. - - 17. _Rhodomelaceae_--Frond leafy, thread-like, or jointed, - composed of polygonal cells. Spores in external - conceptacles. Tetraspores in distorted branchlets or in - receptacles. - - =C.= =Melanospermeae=--Olive-spored weeds. Frond tough, leathery. - Spores in globular cavities in substance of frond. - - 18. _Ectocarpaceae_--Frond jointed, thread-like. Spores attached to - or imbedded in branchlets. - - 19. _Chordariaceae_--Frond gelatinous or cartilaginous, composed of - interlacing vertical and horizontal filaments. Spores - internal, attached to the filaments. - - 20. _Dictyotaceae_--Frond inarticulate. Spores superficial, arranged - in definite spots or lines. - - 21. _Laminariaceae_--Frond inarticulate. Spores covering the whole - frond or in cloud-like patches. - - 22. _Sporochnaceae_--Frond inarticulate. Spores attached to jointed - filaments which are either free or compacted. - - 23. _Fucaceae_--Frond inarticulate, large and tough. Spores in - globular cavities. - - - - - CHAPTER XVI - - _THE FLOWERING PLANTS OF THE SEA-SIDE_ - - -A considerable number of our flowering plants exhibit a decided -partiality for the neighbourhood of the sea, and many are to be found -only on the sea cliffs or in salt marshes not far from the shore. The -principal of these will be now briefly described, dealing first with the -monocotyledons, and then with the more highly organised dicotyledons. - -The chief distinguishing features of these two groups have already been -referred to, but it will be advisable here to give them in somewhat -fuller detail. - - [Illustration: FIG. 275.--TRANSVERSE SECTION OF THE STEM OF A - MONOCOTYLEDON] - -The _monocotyledonous plants_, then, are those in which the stem is more -or less woody and cylindrical, without either true bark or pith; and the -woody tissue is not arranged in concentric rings, but in isolated -bundles, which first bend inwards, as they rise, towards the centre of -the stem, and then curve outwards towards the surface, which is hardened -by the formation of a layer of hard woody matter. As a rule the stem is -unbranched, and its growth takes place by a single bud at the summit. In -nearly all of them the leaves are long and narrow, with veins running -parallel throughout their length; and the parts of the flower are -arranged in whorls of three or six. The outer whorl of the flower is -often a conspicuous white or coloured _perianth_ (that portion of the -flower which lies outside the anthers), but in some the perianth is -absent, the flower being protected by scaly bracts. The seeds are -produced in a case called the ovary, and are fertilised by pollen grains -which are developed in the anthers. When the pollen grains are set free -they alight on the adhesive stigma, and grow, sending their tubes down -into the ovary. The term monocotyledon is applied to these plants -because the embryo has only one cotyledon or seed-leaf. - - [Illustration: FIG. 276.--LEAF OF A MONOCOTYLEDON] - -The principal divisions of this group are the _Glumaceous -Monocotyledons_, in which the flower has no perianth, but is enclosed in -scaly bracts or husks called glumes; and the _Petaloid Monocotyledons_, -distinguished generally by the presence of a more or less conspicuous -white or coloured perianth. The first of these includes the rushes, -sedges, and grasses; and the other contains the lilies and orchids, with -their allies, together with certain aquatic and semi-aquatic plants. - -Among the Grasses there are several species that show a preference for -the immediate neighbourhood of the sea, some growing luxuriantly at the -bases of the cliffs where the beach is sandy, and others thriving best -in salt marshes; but before dealing with these individually we shall -note the general characteristics of the order (_Gramineae_) to which they -belong. - -Grasses are distinguished by their jointed stems, which are usually -hollow, with a split sheath, and bearing alternately arranged narrow -leaves. The flowers, which are disposed either in spikes (sessile -flowers arranged along a common axis) or in panicles (flowers stalked -and arranged as in fig. 281), consist of scale-like bracts enclosing the -stamens and the pistil. The bracts are in two series, the outer usually -consisting of two _glumes_, and the inner of two _pales_; the upper -pale, however, has two ribs running through it, and is therefore usually -looked upon as a combination of two. In some species both glumes and -pales are absent; but the former, when present, enclose one or more -flowers, among which may be some that are abortive. The stamens are -generally three in number, attached to the base of the flower; and the -ovary is superior or free, that is, it grows above the other parts of -the flower, and contains but one seed. - -It will be convenient at this stage to refer briefly to the two -principal methods by which the pollen of flowers is transferred to the -stigmas for the purposes of fertilisation, and to see how various -species are structurally adapted to the means by which the transfer is -brought about. - -Speaking generally, we may classify flowers into those which are -fertilised by the wind (anemophilous flowers) and those in which the -pollen is transferred by insects (entomophilous flowers). The former -offer no attractions to allure the various forms of insect life. They -are, generally speaking, very inconspicuous, being of small size and -having no bright corollas. None of them are scented, nor do they produce -the sweet nectar that forms the principal food of so many insects. Their -anthers are borne on long filaments, so that they are exposed freely to -the wind; and they produce abundance of pollen to compensate for the -very wasteful method of wind-dispersion. The pollen, too, is not very -adherent, so that it may be readily carried away by the breeze; and the -plants concerned often produce their flowers early in the spring, before -the leaves have appeared, thus giving the wind very free play. - - [Illustration: FIG. 277.--EXPANDED SPIKELET OF THE OAT - G. glumes; P.e, outer pale; P.i, inner pale; A, awn; F.S, a sterile - flower. The stamens and the feathery stigmas of the fertile flower - are also shown] - -Insect-fertilised flowers, on the other hand, are usually of attractive -appearance; and, though often small and inconspicuous individually, they -are in such cases grouped together in more or less showy clusters. They -are also usually scented, and supply nectar and pollen to the insects -which they allure. Some are fertilised by insects that fly by day, and -these often close their petals on the approach of night, thus protecting -their pollen during the period in which their fertilisers sleep. Others, -fertilised by nocturnal insects, always spread their petals during the -night, and generally protect their pollen from waste by sleeping -throughout the day. As a rule, too, these night-bloomers have large and -pale-coloured petals that are more easily seen by night; they also evolve -a powerful scent to aid the insects in searching them out. - -It will be seen that the economic relationship existing between flowers -and insects is a mutual one, the latter visiting the former in order to -obtain food, while the former derive in return the advantage of a direct -transfer of pollen from flower to flower. - -It is a well-known fact that the self-fertilisation of a flower often -results in the development of very weak seedlings as compared with those -that are produced by crossing; and it often happens that the pollen of a -flower is incapable of producing the least effect when deposited on the -stigma of the same bloom. In some cases the contact of the pollen of a -flower with its own stigma will even act as a poison, causing the whole -to shrivel and die; and truly wonderful are the varied means by which -flowers contrive to secure a cross-fertilisation. It is here that the -work of the wind and insects proves so valuable to flowers; but, in -addition to this, a very large number of flowers are absolutely -incapable of self-fertilisation, for the anthers and the stigma are not -mature at the same time, or they exist in separate flowers, either on -the same plant or on distinct plants of the same species. It is most -interesting and instructive to study the many contrivances by which -flowers compel certain insects to convey the pollen exactly in the way -that best serves their purpose, sometimes even entrapping them after -they have been allured, and not allowing them to escape until they are -thoroughly dusted with the pollen which they are required to convey; but -it is hardly our province to enter more fully into this matter in these -pages. - -An examination of the grasses will show at once that they are adapted -for fertilisation by the wind. The flowers produce no nectar; and, -consistently, develop no bright petals and evolve no odours to attract -insects. On the other hand, their anthers produce abundance of -lightly-adhering pollen, and are mounted on long filaments which hold -them well exposed to the wind; and the stigmas are well adapted for -catching the scattered grains, being long and protruding, and often -covered with sticky hairy or feathery appendages. - -Although the flowers of grasses are generally wanting in attractive -colours, the clusters of blossoms are often very graceful and pretty, -especially when the large anthers, covered with bright-yellow pollen, -dangle in the breeze. - -We will now briefly describe the principal British grasses that grow -chiefly or exclusively in the immediate neighbourhood of the sea. - -The Sea Hard Grass (_Lepturus filiformis_) is a perennial species, -usually about six inches in height, very common on some sandy coasts, -and found in flower during the hottest months of the summer. The flowers -are arranged in simple spikes, on slender erect stems; and the glumes, -which are united at their bases, enclose a single bloom. - -In similar situations we may find the Sea Lyme Grass (_Elymus -arenarius_), a tall species, often reaching a height of four feet, with -glaucous rigid leaves. The flowers are arranged in a simple spike, but -the spikelets are clustered two or three together. This species flowers -in August. - -Of the well-known Barley Grasses there is one species (_Hordeum -maritimum_) that has its habitat along the coast. Like the others of its -genus, the spikelets are arranged in threes, each bearing a single -flower, and the pales have long slender processes (_awns_) which -constitute the so-called beard. It also resembles the common Meadow -Barley Grass in having the middle flower of each three perfect, while -the two laterals are abortive, but may be distinguished by its rough and -bristly glumes, and the semi-oval form of the pales of the lateral -flowers. It is a somewhat stunted species, sometimes only five or six -inches in height, and may be found in flower about Midsummer. - -The Brome Grasses have also a representative of a sea-loving nature, -which is to be found in fields near the cliffs. It is the Field Brome -Grass (_Bromus arvensis_), an annual grass that grows to a height of two -or three feet. Brome grasses generally are known by their loose panicles -of flowers, lanceolate and compressed spikelets, and awned florets -enclosed in unequal glumes; and _B. arvensis_ may be distinguished by -its hairy leaves and stem-sheath, and the drooping panicle with the -lower peduncle branched. - - [Illustration: FIG. 278.--THE SEA LYME GRASS] - -Among the Meadow Grasses we have three or four coast species. In these -the florets are in panicles and are not awned. The outer glumes are -keeled and traversed by several veins; and the lower pales are also -keeled, with five or more nerves. The Sea Meadow Grass (_Poa maritima_) -grows in salt marshes near the sea, its erect rigid panicles reaching a -height of about eight or ten inches. It has a creeping root, and its -leaves are curved inward at the margins. The Procumbent Meadow Grass -(_P. procumbens_) and a variety of the Reflexed Meadow Grass (_P. -distans_) are also plentiful in salt marshes. The former may be known by -the short rigid branches of its panicle and the five ribs of the lower -pales; and the latter is much like _P. maritima_, but grows taller, and -its spikelets are crowded. The Wheat Meadow Grass (_P. loliacea_) grows -on sandy shores. Its spikelets are arranged singly and alternately along -the central axis, and the upper glume reaches to the base of the fourth -floret. This species flowers in June, but the other three of the same -genus bloom from July to September. - -The reader is probably acquainted with the Fescue Grass, with its awned -flowers arranged in one-sided panicles. There are no less than seven -species, one of which--the Single-husked Fescue (_Festuca -uniglumis_)--grows on sandy shores, flowering in June and July, and -reaching a height of from nine to twelve inches. The panicles are -upright and unbranched, and the species may be readily known by the -flowers, which are compressed, with long awns, and with the lower glumes -wanting. - -_Knappia agrostidea_ is a dwarf species, rarely exceeding four inches in -height, that is found on certain sandy shores, but is very local. Its -flowers are arranged in a simple spike, the spikelets being solitary and -unilateral, with only a single flower, and the pales are shaggy. The -plant has several stems which bear short, rough leaves. - -The Mat Grass or Sea Reed (_Ammophila arundinacea_) is common on many -sandy coasts, where it grows to a height of three or four feet, and -flowers in July. The white flowers are clustered in dense cylindrical, -pointed spikes; and the leaves are of a glaucous green colour, rigid, -and curved inward at the edges. - -Dog's-tooth Grass (_Cynodon dactylon_). This species has a creeping -root, and the leaves are downy on the under side. The flowers are -arranged in a compound spreading spike, of three to five parts, and the -spikelets are of a purplish colour, ovate in form, and arranged in -pairs. The glumes are equal in size. It is found on sandy shores, grows -to a height of about six inches, and flowers in July. - -A species of Canary Grass (_Phalaris arundinacea_) is also to be seen on -sandy coasts. Unlike the other species of the same genus, its flowers -form an erect spreading panicle, and the glumes are not keeled. It is -also taller than the common canary grass of waste places, often reaching -a height of three feet, and is commonly known as the Reed Canary Grass. - - [Illustration: FIG. 279.--_Knappia agrostidea_] - - [Illustration: FIG. 280.--THE DOG'S-TOOTH GRASS] - - [Illustration: FIG. 281.--THE REED CANARY GRASS] - -The Sea Cat's-tail Grass (_Phleum arenarium_) is common on many coasts. -It is much smaller than the common species of Cat's-tail, being -generally less than a foot high. The spike is of an elongated oval form, -blunt at the tip and narrow at the base; and the glumes are narrow, -pointed at both ends, and fringed. Each spikelet has but one flower. - -In salt marshes we occasionally meet with the Perennial Beard Grass -(_Polypogon littoralis_), but it is somewhat rare. It has a creeping -root, and the flowers form a somewhat dense spike-like panicle. The -glumes have a slender awn. It grows to a height of one to two feet, and -flowers in July. - -The Tuberous Fox-tail Grass (_Alopecurus bulbosus_) is another rare -grass of the salt marshes, where it grows to the height of twelve to -sixteen inches, flowering in May and June. The genus to which it belongs -is very closely allied to _Phleum_, but may be distinguished by having -only one pale to each flower, and this species has a long awn attached -to the back portion. The panicle, too, is cylindrical and slender, the -glumes quite free and abruptly pointed, and the awns longer than the -pales. - -The last of the sea-side grasses are two rare species of Cord Grass -(_Spartina_), both of which are found in salt marshes. In these the -inflorescence is a compound spike, with one-sided spikelets inserted in -a double row. The glumes are keeled and pointed; the pales cleft, -pointed and without awns; and the styles two in number, very long. The -only British species of the genus are the two (_S. stricta_ and _S. -alternifolia_) referred to above. They both grow to a height of about -eighteen inches, and flower in late summer. In the former the spikes -number two or three, and are longer than the leaves; and the outer glume -is hairy, with a single nerve. The latter, which is the rarer of the -two, bears several spikes, shorter than the leaves; and the outer glume -has five nerves. - -Certain of the sedges (order _Cyperaceae_) are also more or less familiar -to the sea-side naturalist, and must therefore receive a small share of -our attention. In general terms these are grasslike, monocotyledonous -plants, the stems of which are solid, jointed, and frequently angular. -The leaves are very similar to those of grasses, except that the -sheaths, which surround the stem, are not split. The flowers are -generally arranged in a spike, overlapping each other, and each one -supported on a scale-like bract. In some sedges the flowers are perfect, -each one possessing both stamens and pistil; but in some species the -flowers are unisexual, some bearing stamens and no pistil, and others -pistil only. The stamens are generally three in number, the ovary is -superior, and the stigmas either two or three. - -Sedges abound in moist places, some being peculiar to salt marshes, -while others grows on sandy shores; and a few of the British species of -the latter habitat are often so abundant that their creeping roots bind -the sand together, effectually holding it in place while the surrounding -portions of the beach are mercilessly driven by the wind. - -A few of the sea-side sedges belong to the genus _Carex_, in which the -flowers are imperfect, and the fruit is enclosed in the outer parts of -the flower. _C. extensa_ thrives in salt marshes, growing to a height of -a foot or more, and flowering about midsummer. Its fertile flowers form -oblong erect spikelets, while the barren spikelets are solitary. The -bracts are long and leafy, with short sheaths surrounding the stem. The -leaves are curved in at the edges, and the fruit is oval and ribbed, -with a short straight beak. - -On sandy shores the Sea Sedge (_C. arenaria_) is often common, and its -underground stems are used for sarsaparilla. It is a perennial species, -growing to a height of about nine inches, and flowering in June and -July. The flowers grow in an oblong interrupted spike, the upper -spikelets being barren, and the intermediate ones barren at the tip. -The fruit is oval, veined, and winged. - -Another species of this genus--the Curved Sedge (_C. incurva_)--is -sometimes to be seen on sandy shores, but it is rare, and is also a very -small sedge, growing only to a height of about three inches. It derives -its specific name from its curved stem, and may be further distinguished -by its channelled leaves and the globular mass of spikelets which are -barren on the top. - - [Illustration: FIG. 282.--MALE AND FEMALE FLOWERS OF _Carex_, - MAGNIFIED] - -Some of the so-called rushes belong to the same order as the sedges, and -a few of these are more or less restricted to the neighbourhood of the -sea. The Salt-marsh Club Rush (_Scirpus maritimus_), as its name -implies, is to be found in marshes near the sea. It is very variable in -height, ranging from one to three feet, and displays its dense terminal -cluster of spikelets in July and August. In this genus all the flowers -are perfect, the glumes imbricated and bristled; and the present species -may be distinguished by the glumes being divided into two sharply -pointed lobes. A variety of _S. lacustris_ may also be found on the sea -shore, but it is somewhat rare. It has a leafless glaucous stem, and -flowers arranged in compound spikes. The glumes are rough, and contain a -compressed fruit. - -A very small species of the Spike Rush (_Eleocharis parvula_), growing -only one or two inches high, is sometimes found on the muddy shores of -Ireland. It has perfect flowers, in a single terminal spikelet. The -leaves are very narrow, growing from the base of the plant; and the -round stem is enclosed in a single leafless sheath. - -The true rushes belong to the order _Juncaceae_. These have fibrous roots -and narrow leaves, and bear clusters of brown flowers. The perianth -consists of six parts, and the stamens are usually six in number. The -ovary is generally three-celled, developing into a three-valved capsule. -The Lesser Sea Rush (_Juncus maritimus_) is common in salt marshes, -growing to a height of two or three feet, and flowering in July. It has -a rigid leafless stem, bearing lateral clusters of flowers. The segments -of the perianth are very narrow and sharp, and the seeds are enclosed in -a loose testa. Closely allied to this species is the Great Sea Rush (_J. -acutus_), which grows three or four feet high on sandy shores. In -general characteristics it resembles_ J. maritimus_, but the segments of -the perianth are oval and have thin transparent margins; and it is a -much rarer species. - - [Illustration: FIG. 283.--THE SEA SEDGE] - - [Illustration: FIG. 284.--THE CURVED SEDGE] - - [Illustration: FIG. 285.--THE GREAT SEA RUSH] - -We now pass to the peculiar Sea Grasses or Grass Wracks (_Zostera_) -which grow in salt water. They belong to the order _Naiadaceae_, and are -characterised by cellular leaves with parallel veins, and inconspicuous -unisexual or bisexual flowers. The perianth, when present at all, -consists of two or four scale-like parts, and the stamens correspond in -number with these. The ovary is free, and the carpels, one or more in -number, contain each a single ovule. In _Zostera_ the flowers are -imperfect, and seem to grow in the slit of the leaf. There are two -species, both of which grow in shallow water close to the shore, often -in such dense masses that they impede the progress of boats. They have -long creeping stems that lie buried in the sand, giving off numerous -root-fibres, and send up to the surface slender branches that bear -grass-like leaves. The flowers are unisexual, and are arranged in two -rows on the same side of a flattened stalk that is enclosed in a sheath -formed by short leaves. They have no perianth, the male flowers being -composed of a single anther, and the female of a one-celled ovary -containing a single ovule, and surmounted by a style with two long -stigmas. - -There are two species--the Broad-leaved Grass Wrack (_Z. marina_) with -leaves one to three feet long and traversed by three or more parallel -veins, and the Dwarf Grass Wrack (_Z. nana_), the leaves of which are -less than a foot long, with veins numbering one to three. There is a -variety of the former, however, named _Angustifolia_, in which the -leaves are much narrower than usual, and the veins fewer in number. - - [Illustration: FIG. 286.--THE BROAD-LEAVED GRASS WHACK] - - [Illustration: FIG. 287.--THE SEA-SIDE ARROW GRASS] - - [Illustration: FIG. 288.--THE COMMON ASPARAGUS] - -The order _Alismaceae_, which contains the water plantains, arrow-heads, -and other semi-aquatic plants, has a representative of marine tendencies -in the Sea-side Arrow Grass (_Triglochin maritimum_). The flowers of -this order are bisexual, with six stamens and a six-parted perianth. The -fruit consists of many carpels; and, although the plants are -monocotyledons, their leaves have netted veins; and altogether they -somewhat resemble the ranunculaceous exogens. The Sea-side Arrow Grass -is abundant in some salt marshes, growing to a height of about a foot, -and produces loose simple spikes of green flowers all through the -summer. The leaves are radical, narrow and fleshy; and the ovary -consists of six carpels. - -Of the interesting order _Liliaceae_ we have only one plant of the coast, -and even that--the _Asparagus_--is not by any means generally common. It -is the same plant that is so largely cultivated as an article of diet, -and which is so highly valued on account of its diuretic properties. It -is moderately common on parts of the south coast, particularly in the -Isle of Portland and in West Cornwall, and its general appearance is so -graceful that it is largely employed as an ornamental garden plant. The -stem is erect and freely branched, bearing feathery bunches of bristled -leaves and pale-yellow axillary flowers. As is the case with the -_Liliaceae_ generally, the flowers are bisexual, with a six-parted -perianth, six stamens, and a three-celled superior ovary; and the last -named, in the Asparagus, forms a bright-red berry in the autumn. - -We have now to leave the monocotyledonous plants and pass on to the -_dicotyledons_, which form the most highly developed of the primary -divisions of the vegetable kingdom. A few of the general characteristics -of this group have already been given, but we must now look rather more -closely into the nature of the plants included. - -The class receives its name from the presence of two cotyledons or -seed-leaves in the embryo plant, and is also known as the _Exogenae_ -because the stems increase in thickness by the addition of zones of -woody tissue at the exterior. When the young dicotyledonous plant first -appears above the ground, the two cotyledons, which formerly served to -shelter the immature bud, usually appear as tiny fleshy leaves; but -these soon wither away, while the bud produces the more permanent leaves -that are of a very different structure. A section of the stem will -reveal distinct pith, wood, and bark, the wood being more or less -distinctly divided into wedge-shaped masses by rays from the pith; and, -in the case of perennial stems, the wood is arranged in concentric -rings, the number of which correspond approximately with the years of -growth. The leaves of exogens have their veins in the form of a network, -and the parts of the flower are generally arranged in whorls of two or -five or of some multiple of these numbers. - -The flowers always have stamens and pistil, but in some these organs -exist in separate flowers, either on the same plant, or on different -plants of the same species, and the ovules are nearly always contained -in a case called the ovary. - -Dicotyledons are divided into three main groups, the division being -based on the structure of the flowers. They are the _Apetalae_ in which -the petals are absent, but the perianth is frequently petaloid, though -it is occasionally also absent; the _Gamopetalae_, in which the petals -are united; and the _Polypetalae_, in which the petals are always -distinct. - -Dealing with these divisions in the above order we come first to the -Spurges, three species of which occur on sandy shores. They belong to -the order _Euphorbiaceae_, which includes, in addition to the spurges, a -number of herbs, trees, and shrubs with entire leaves often a milky -juice, and small flowers, sometimes enclosed in calyx-like bracts. The -flowers may have one or several stamens, and the perianth, if present, -consists of three or four parts; but perhaps the best distinguishing -feature of the order is the nature of the fruit, which separates -elastically into three carpels. - - [Illustration: FIG. 289.--THE SEA SPURGE] - -The Sea Spurge (_Euphorbia Paralias_) is commonly seen on sandy shores, -where its yellow flowers bloom in late summer and in autumn. It may be -distinguished among the numerous species of the genus by its narrow -oblong imbricated leaves, of a tough leathery nature, the broad -heart-shaped bracts, and the wrinkled capsules containing smooth seeds. -The Portland Spurge (_E. portlandica_) is a similar plant, found in -similar situations, and flowering from May to September. Its leaves are -oval and narrow, obtuse, and of a glaucous colour, and the bracts are -more triangular than those of the last species. The capsules are -slightly rough, as are also the seeds. There is yet another sea-side -spurge--the Purple Spurge (_E. peplis_)--a somewhat rare plant, found on -some of the sandy shores of the south of England. It grows to about -eight or nine inches in length, and blooms in late summer, the flowers, -like those of most of the spurges, being yellow. The stem is of a -glaucous colour, and trails along the ground; the leaves are opposite -and somewhat heart-shaped, and the flowers solitary. This species may be -distinguished from other spurges by its stipuled leaves. - -On sandy cliffs we sometimes meet with the Sea Buckthorn (_Hippophae -rhamnoides_)--a spiny shrub, ranging from about two to seven feet in -height, the bark of which is covered with a silvery scaly scurf that -forms a beautiful object for the microscope. It is the British -representative of the Oleasters (order _Eleagnaceae_). The leaves are -alternate, lanceolate, with a silvery surface; and the flowers are -small, green and unisexual. The male flowers grow in catkins, each -arising from a scaly bract, and have a green perianth. The female -flowers have a tubular perianth, and a free one-celled ovary. The latter -forms a hard nut-like fruit, which is surrounded by a succulent mass -formed by the former. This shrub flowers in the spring, while the leaves -are still very small. - - [Illustration: FIG. 290.--THE PURPLE SPURGE] - - [Illustration: FIG. 291.--THE SEA BUCKTHORN] - -Of the order _Polygonaceae_, which includes the docks, knot grasses, -buckwheats, and sorrels, we have two sea-side representatives, both -belonging to the typical genus _Polygonum_. These are the sea-side Knot -Grass (_P. maritimum_) and Ray's Knot Grass (_P. Raii_). The plants of -this order are herbs, characterised by their alternate leaves with -sheathing stipules; and small flowers, usually bisexual, often with a -coloured perianth. Most of the species are remarkable for their -astringent and acid properties. In the genus _Polygonum_ the flowers are -usually in spikes or racemes; the perianth funnel-shaped, regular, and -five-cleft. The stamens vary from five to eight in number, and the -styles number two or three. The fruit is a small angular nut, usually -enclosed in the perianth. - -The sea-side Knot Grass is very common on some parts of the shore, where -it grows from one to three feet long, and flowers in August. The stem is -recumbent, tough and woody, bearing fleshy glaucous leaves with curled -edges. It may be further distinguished from the other knot grasses by -its long stipules, with freely-branching veins, and by the length of the -fruit exceeding that of the perianth. As in the other knot grasses, the -flowers arise from the axils of the leaves. - -Ray's Knot Grass is very much like the common knot grass so abundant in -all waste places, the leaves being flat; and the stipules, shorter than -in the last species, having but few veins; but while in the latter the -fruit is shorter than the calyx, in _P. Raii_ it is longer. This species -is found on many sandy shores, and flowers in July and August. - -The order _Chenopodiaceae_ is particularly rich in sea-side plants, more -than a dozen of the British species growing almost exclusively near the -shore. They are mostly inconspicuous plants, with small flowers which -are sometimes unisexual. The perianth is deeply divided, and the stamens -are inserted in its base, opposite the divisions. The ovary is free, -containing a single ovule. - -The typical genus (_Chenopodium_) contains the weeds designated by the -name of Goosefoot, all characterised by their straggling stems and small -flat leaves. One species (_C. botryoides_) is common on some sandy -shores. It is a small weed, its prostrate stem measuring only a few -inches in length. The leaves are triangular and fleshy, and the flowers -are arranged in dense leafy clusters. A variety of the Red Goosefoot -(_C. rubrum_) is also found on the coast. It is of a reddish colour, -with rhomboid leaves and short crowded spikes of flowers. - - [Illustration: FIG. 292.--_Chenopodium botryoides_] - -On muddy shores we meet with the Common Beet (_Beta maritima_), the -leaves of which are often cooked and eaten where the plant is abundant; -and it is this species from which the different varieties of garden beet -and mangold wurzel have been produced by cultivation. There are two -distinct varieties of the wild plant. In one the root and leaves are of -a purple colour, while in the other they are of a yellowish green. The -former has been cultivated for its root, while the latter is sometimes -grown for the leaves. In the wild state it has many stems, the lower -parts being more or less procumbent, and the leaves are fleshy, -gradually narrowing down into the stalk. The flowers, which are arranged -in long, simple, leafy spikes, are bisexual, with a five-parted -perianth, five stamens inserted opposite each segment, in a fleshy ring -and a flattened one-celled ovary which develops into a one-seeded -utricle. - -In similar situations we meet with two species of Sea Purslane -(_Obione_), in which the flowers are unisexual, both male and female -flowers being on the same plant. They are also distinguished from most -other Chenopods by the perianth adhering to the wall of the ovary. The -Shrubby Sea Purslane (_O. portulacoides_) is, as its name implies, a -shrubby plant. It grows to a height of eighteen inches or two feet, -bearing silvery oval lanceolate leaves and sessile fruit. The other -species referred to--the Stalked Sea Purslane (_O. pedunculata_)--is -herbaceous, with oval, mealy leaves, and stalked fruit. - - [Illustration: FIG. 293.--THE FROSTED SEA ORACHE] - - [Illustration: FIG. 294.--THE PRICKLY SALT WORT] - -The Oraches (genus _Atriplex_) resemble the Purslanes in the granular -mealiness of the foliage, and the two are so closely allied that they -are often placed in the same genus. Oraches are most readily -distinguished among the Chenopods by the two bracts which enclose the -fruit and enlarge after flowering; and, like the Purslanes, they have -unisexual flowers, both male and female being on the same plant. Three -of our five British species are sea-side plants. The Frosted Sea Orache -(_A. arenaria_) grows on sandy shores, about six or eight inches in -height, and flowers during late summer and autumn. It may be known by -its buff-coloured stem, with triangular or rhomboidal, jagged, silvery -leaves, and clusters of sessile flowers in the axils of the leaves. -Another species (_A. Babingtonii_) may be seen on both rocky and sandy -shores, usually from one to two feet in height, and flowering from July -to September. Its stem is procumbent, green with reddish stripes; leaves -oval-triangular, lanceolate towards the top, three-lobed at the base of -the stem, light green, with a mealy surface; flowers in terminal -clusters as well as in the axils of the leaves. A third species--the -Grass-leaved Orache (_A. littoralis_) grows in salt marshes. All its -leaves are grass-like and entire, and the stem is generally marked with -reddish stripes as in _A. Babingtonii_. The flowers, too, are in sessile -axillary clusters only. This plant reaches a height of from one to two -feet, and flowers in the late summer. - -The Prickly Salt Wort (_Salsola kali_) is a very common sea-side plant -on some of our coasts, and may be recognised at a glance by its general -form and habit. The stem is very much branched and prostrate, forming a -very bushy plant about a foot in height. It is also very brittle and -succulent, furrowed and bristly, and of a bluish-green colour. The -leaves are fleshy, awl-shaped, nearly cylindrical, with a spiny point, -and little prickles at the base. The flowers are axillary and solitary. -This plant and its exotic allies are very rich in alkaline salts, -particularly carbonate of soda, and were formerly the principal source -from which this compound was obtained. - - [Illustration: FIG. 295.--THE CREEPING GLASS WORT] - -Our last example of the sea-side chenopods is the Glass Wort -(_Salicornia_), which thrives in salt marshes. In this genus the stem is -jointed and the flowers bisexual. The Jointed Glass Wort (_S. herbacea_) -is common in most salt marshes, where its erect, herbaceous, leafless -stem may be seen growing to a height of a foot or more. The joints are -thickened upwards, and shrink to such an extent when dry that the upper -part of each segment of the stem forms a membranous socket into which -fits the base of the next segment above. The flowers are arranged in -dense tapering spikes, also jointed, with a cluster of three flowers on -the two opposite sides of the base of each segment. Each flower is -composed of a perianth, closed with the exception of a small aperture -through which the stigma and, later, the stamens protrude. The Creeping -Glass Wort (_S. radicans_) has a woody procumbent stem, with the joints -only slightly thickened, and the spikes do not taper so much as in _S. -herbacea_. Both these plants yield considerable quantities of soda, and -they are named 'Glass Wort' because they formerly constituted one of the -sources from which soda was obtained for the manufacture of glass. - -We now come to those flowers in which both calyx and corolla exist, and -shall deal first with the division _Gamopetalae_ or _Monopetalae_, in -which the petals are united. - -Our first example of this division is the Seaside Plantain (_Plantago -maritima_), of the order _Plantaginaceae_. This is a stem-less -herbaceous plant, with ribbed leaves and small green flowers, common on -many parts of the coast, and also found on the mountains of Scotland, -flowering throughout the summer. It may be distinguished from the other -plantains by its narrow fleshy leaves. As in the other species, the -flowers form a cylindrical spike. - - [Illustration: FIG. 296.--THE SEA-SIDE PLANTAIN] - - [Illustration: FIG. 297.--THE SEA LAVENDER] - -The order _Plumbaginaceae_ contains several sea-side plants, including -the Sea Pink or Thrift (_Armeria maritima_) and the various species of -Sea Lavender (genus _Statice_). They are characterised by a tubular -membranous calyx, persistent and often coloured, a regular corolla of -five petals united at their bases, five stamens opposite the petals and -attached at the base of the ovary, and a free one-celled and one-seeded -ovary. The well-known Sea Pink, with its compact head of rose-coloured -flowers, in bloom throughout the spring and summer, and linear -one-veined leaves, may be seen on most of our coasts, as well as on high -ground in inland districts. The Sea Lavender, of which there are four -British species, have their flowers arranged in spikes. The commonest -species (_Statice limonium_) may be found principally on muddy shores. -Its leaves are narrow and one-ribbed, and the bluish-purple flowers -arranged in short dense spikes, the flower stalk being branched only -above the middle. One variety of it has its flowers in a loose pyramidal -cluster, while another bears its spikes in a compact level-topped corymb -with short firm branches. Another species (_S. bahusiensis_) is -characterised by long spikes of distant flowers, the stalk being -branched from near the base. The Upright Sea Lavender (_S. binervosa_) -of rocky shores has the stalk branched from the middle, with, usually, -nearly all the branches flowering, though there are varieties in which -the flowers are differently arranged. The Matted Sea Lavender (_S. -caspia_) grows in salt marshes on the east coast of England. Its flower -stalk is branched from the base, but the lower branches are barren and -tangled, while the upper bear small crowded lilac flowers. The leaves of -the last two species are spatulate in form. - -The Bittersweet or Woody Nightshade (_Solanum Dulcamara_) of the order -_Solanaceae_ is common in hedgerows and waste places almost everywhere, -but a variety of it (_marinum_) has its habitat along the coast. It may -be distinguished from the normal form by its prostrate branched and -non-climbing stem, and by its fleshy leaves. The latter are all cordate, -while in the normal the upper leaves are auricular. The order to which -_Solanum_ belongs is characterised by a regular five-cleft calyx and -corolla, four or five stamens attached to the corolla, and a superior -two-celled ovary. The flowers are in axillary cymes, and the fruit is a -berry. - -_Convolvulaceae_ is represented on sandy shores by the Sea-side Bindweed -(_Convolvulus Soldanella_), a small species, with pinkish purple -flowers, the prostrate stem of which rarely measures more than a foot in -length. The plants of this order are generally climbing plants with -alternate leaves and regular showy flowers. The calyx is composed of -five sepals, the corolla of four or five lobes, and the stamens are -attached to the corolla. The ovary is superior, two- or four-celled, and -the fruit a capsule. The above species may be recognised by its reniform -leaves (sagittate in the others), which are also fleshy. - -To the order _Gentianaceae_ belong the Centaury (_Erythraea_), three out -of the four British species of which grow on sandy shores. In the -flowers of this order the calyx has from four to ten lobes; the stamens -also number four to ten, and are alternate with the lobes of the -corolla. The ovary is one- or two-celled, and the fruit is a berry with -many seeds. The leaves are usually opposite and entire, and the flowers -are generally showy, regular, and solitary. _Erythraea_ has a -funnel-shaped corolla, five stamens, and two stigmas, on a deciduous -style; and in all our species the flower is rose-coloured. The Dwarf -Centaury (_E. pulchella_), which is common on some sandy shores, is much -smaller than the species that thrives in pastures, being only two or -three inches in height. Its stem is also more freely branched, and its -flowers are axillary and terminal. The Tufted Centaury (_E. littoralis_) -and the Broad-leaved Centaury (_E. latifolia_) occur in similar -situations, but are comparatively rare. They are both small species, the -former with an unbranched stem, narrow leaves, and corymbose -inflorescence; and the latter with branched stem, broad elliptical -leaves, and flowers in dense forked tufts. - - [Illustration: FIG. 298.--THE DWARF CENTAURY] - -The extensive order _Compositae_ contains comparatively few sea-side -plants, and, in dealing with these, we pass to another division of the -monopetalous flowers, in which the ovary is inferior and the stamens are -on the corolla. The order includes those herbaceous plants in which -sessile flowers are collected together into compound heads (_capitula_) -surrounded by a whorl of bracts. The corolla is either tubular or -strap-shaped (_ligulate_), the stamens four or five in number, and the -fruit one-seeded, usually crowned with the limb of the calyx in the form -of a scaly feathery or hairy pappus. - -The Little Lettuce (_Lactuca saligna_) is found in chalky pastures near -the east and south-east coasts, growing to a height of about a foot, and -bearing heads of yellow flowers in July and August. All the flowers are -ligulate and perfect, the pappus is composed of silvery hairs, and the -fruit is compressed and beaked, the beak being twice as long as the -fruit. The leaves are smooth, linear, and sagittate, terminating in a -sharp point. The Sea-side Cotton Weed (_Diotis maritima_) is -occasionally met with on sandy shores, and may be recognised by its -dense coating of downy hair, its sessile obtuse leaves, and heads of -yellow flowers forming a corymb. The heads are discoid, and the fruit -has no pappus. The Sea Wormwood (_Artemisia maritima_) is a common -sea-shore composite, bearing drooping heads of reddish-white flowers in -August. This is another of the downy species, its pinnatifid leaves -having quite a woolly appearance. The capitulum contains but few -flowers, all of which are perfect; and the fruit has no pappus. A -variety of this plant is sometimes seen, with dense erect capitula. The -Sea Aster or Michaelmas Daisy (_Aster tripolium_) of salt marshes may be -known by the yellow discs and purple rays of its flower heads, which are -arranged in a corymb. The florets of the ray form a single row, and the -fruit has a hairy pappus. The leaves of this plant are spatulate and -fleshy. A variety occurs in which the purple florets of the ray are -absent. The Golden Samphire (_Inula crithmoides_) is a very local -sea-side plant, being found principally on the south-west coast. Its -leafy stems grow to a height of a foot or more, and bear yellow heads of -flowers that radiate in all directions. The leaves are linear, acute, -and fleshy, and the bracts are linear and imbricated. Our last example -of the sea-side composites is the Sea-side Corn Feverfew or Scentless -Mayweed, which is a variety of _Matricaria inodora_ of waste places. The -leaves are sessile and pinnatifid, with very narrow segments, and the -white flowers grow in solitary heads. The maritime variety differs from -the normal form in having fleshy leaves. - -We next deal with another very extensive order (the _Umbelliferae_), -which, however, has only three or four representatives on the shore, and -these introduce us to the last great division of the flowering plants, -namely, the _Polypetalous Dicotyledons_, in which the petals are not -united. Of these we shall first deal with that subdivision in which the -stamens are attached at the side of or upon the ovary. - -The most obvious characteristic of the _Umbelliferae_ is that implied in -the name--the arrangement of the flowers in that form of inflorescence, -called the umbel, in which the pedicels all branch from one point in the -main stalk, and are such that the flowers are all approximately on a -level. The flowers are mostly small and white, with five sepals (when -present), five petals, and five stamens. The inferior ovary is -two-celled, bearing two styles; and the fruit separates into two dry -one-seeded carpels that are ribbed longitudinally. - -Our first example of this group is the Sea Carrot, a variety of the Wild -Carrot (_Daucus carota_). In the ordinary form, which is so common in -fields, the leaflets are pinnatifid, with acute segments; and the -central flowers of each umbel are purple, while the outer ones are -white. The umbel, when in fruit, is concave above. The maritime variety -differs from this in having fleshy leaves, and the umbel convex above -when in fruit. The Sea Samphire (_Crithmum maritimum_) grows on the -rocks close to the sea, and thrives well where there is hardly a -vestige of soil. It usually grows to a height of seven or eight inches, -bearing greenish-white flowers surrounded by a whorl of very narrow -leaves. The other leaves are glaucous and bi-ternate, the leaflets being -narrow, fleshy, and tapering towards both ends. On cliffs near the sea, -especially in chalky districts, we meet with the Fennel, with its -finely-divided leaves, split up into numerous capillary leaflets, and -its small yellow flowers without bracts. It may be distinguished from -other closely-allied plants by the form of the fruit, which is flattened -at the sides. It is grown in some parts for use as a potherb, and an -aromatic oil is also obtained from the seeds. The plant grows to a -height of four or five feet, but there is a smaller variety known as the -Sweet Fennel, and distinguished by the stem being compressed at the -base. Our next example of the _Umbelliferae_ is the Sea Holly (_Eryngium -maritimum_), easily distinguished from the other umbellifers by its -spiny glaucous leaves, and the thistle-like heads of blue flowers -surrounded by a whorl of spiny bracts. Its fleshy creeping roots were -formerly gathered largely for the purpose of converting them into the -once-prized 'candied eryngo root,' which is still prepared in a few of -the fishing villages of our coast. The lower leaves of this plant are -spinous and very glaucous, and the upper ones palmate. The venation is -particularly strong and durable, so that the leaves and flowers are used -largely by the sea-side cottagers in the construction of skeleton -bouquets and wreaths. Another plant of the same genus--The Field Eryngo -(_E. campestre_)--is occasionally seen on sandy shores. It differs from -the last in having ternate radical leaves with pinnatifid lobes, and the -upper leaves, bi-pinnatifid. Our last example of the sea-side -umbellifers is the Wild Celery (_Apium graveolens_) of salt marshes and -ditches. This is the plant from which our highly-valued garden celery -has been produced, and it is remarkable that this sweet crisp and -wholesome vegetable has been derived from a wild plant of coarse taste -and odour, the acrid sap of which is highly irritating if not dangerous. -The plant may be known by its furrowed stem, and ternate leaves, the -leaflets of the lower leaves being round and lobed, while those of the -upper ones are notched. The umbels are sessile or nearly so, the flowers -have no calyx, and the fruit has five prominent ridges. - - [Illustration: FIG. 299.--THE SEA SAMPHIRE] - -On the sandy shores of the south-western counties we may meet with the -very local Four-leaved Allseed (_Polycarpon tetraphyllum_) of the order -_Illecebraceae_. It is a small plant, only four or five inches in height, -with the lower leaves in whorls of four and the upper ones in opposite -pairs. The flowers are minute, and are disposed in small dense clusters. - -Another rare species is the shrub known as the English Tamarisk -(_Tamarix anglica_), which is our only representative of the order -_Tamariscaceae_. There is some doubt, however, whether even this is -indigenous to Britain, though it occurs in a wild state on the coast. It -is a very twiggy shrub growing from six to ten feet in height, with -minute scale-like, acute leaves, and slender spikes of small -pinkish-white flowers. - -We now pass to the large order of Leguminous plants, characterised by -their stipuled leaves, and irregular papilionaceous flowers. The latter -usually have five united sepals, five petals forming an irregular, -butterfly-like corolla, ten stamens, and a superior ovary that develops -into a pod. - -Of these the Starry-headed Trefoil (_Trifolium stellatum_) is very -partial to the sea shore, though it is sometimes found some distance -inland. The genus to which it belongs is so called on account of its -trifoliate leaves which are characteristic of the clovers, trefoils, and -vetches, and which have stipules adhering to the petioles. The species -under notice receives its name from the star-like arrangement of the -long teeth of the hairy calyx. The stem of the plant is procumbent, -usually about six or eight inches long, with cylindrical and terminal -heads of yellowish-grey flowers. - -The Rough-podded Yellow Vetch (_Vicia lutea_) is somewhat rare, and -occurs principally on very rocky coasts. In common with the other -vetches it has pinnate, tendrilled leaves, without a terminal leaflet, -one stamen free and the rest united into a bundle, and a long, slender, -hairy style. Its stem is tufted and prostrate, averaging about a foot in -length, the leaflets long and narrow, and the yellow flowers sessile and -solitary. The teeth of the calyx are unequal, and the pods hairy and -curved. - - [Illustration: FIG. 300.--THE SEA-SIDE EVERLASTING PEA] - -The Sea-Side Everlasting Pea (_Lathyrus maritimus_) is a much commoner -plant of the coast, and may be readily recognised by its general -resemblance to the garden sweet-pea. The genus to which it belongs is -closely allied to the vetches, but may be distinguished by the style, -which is flattened below the stigma, hairy on the inner or upper side, -but quite smooth on the outer side. The sea-side species has an angled -(but not winged) stem, from one to three feet long, compound tendrilled -leaves with many oval leaflets, and large oval or cordate stipules. Its -purple flowers are in bloom during July and August. A variety of this -plant (_acutifolius_), with a slender straggling stem and narrow acute -leaflets, occurs on some parts of the Scottish coast. - - [Illustration: FIG. 301.--THE SEA STORK'S-BILL] - -The _Geraniaceae_ is represented at the sea-side by the Sea Stork's-bill -(_Erodium maritimum_), which, however, is by no means a very common -flower. Its relationship to the other stork's-bills and the -crane's-bills may be readily proved by the five persistent sepals, five -distinct clawed petals, the five to ten stamens attached _under_ the -ovary (for we have now reached that division of the polypetalous exogens -distinguished by this mode of insertion of the stamens), and the five -carpels surrounding a long beak resembling that of the stork and the -crane. The plant may sometimes be seen on sandy shores, averaging a foot -in height, though very variable in this respect, and displaying its -pretty pink flowers during the whole of the summer. The principal -features by which it is to be distinguished from the two other British -plants of the same species are its ovate or cordate leaves with very -short petioles, and the presence of only one or two flowers on each -peduncle. - -Passing now to the Sea Mallow (_Lavatera arborea_), we are dealing with -another rather rare plant, of the order _Malvaceae_, sometimes met with -on rocky coasts, chiefly, it appears, on the north coast of Cornwall and -Devon. This is a very shrubby plant, as its specific name implies, and -it is sometimes popularly known as the Tree Mallow on that account. It -has a very woody stem, growing to a height of four or five feet, and -bearing seven-pointed, downy leaves, and solitary, axillary, purple -flowers. As in the other mallows, the flowers have five petals, which -are curiously twisted when in the bud, five sepals, a large number of -stamens united into a tube, and an ovary of many cells, but it may be -distinguished from the other species of the order by its three-lobed -bracts. The plant is found principally in wild, uncultivated spots, but -is commonly grown as a garden plant by the cottagers of villages in the -south-west, and under cultivation it frequently grows to a height of -nine or ten feet, with a tree-like stem three or four inches in -thickness; and it produces such a quantity of fibre that its cultivation -for manufacturing purposes has been suggested. - -We now come to another of the very extensive orders, at least as far as -British plants are concerned, although it contains only a few sea-side -species. We refer to the _Caryophyllaceae_, containing the pinks, -campions, catchflies, chickweeds, &c. The chief features of the order -are jointed, herbaceous stems, opposite leaves, and regular white or red -flowers with four or five sepals and petals, eight or ten stamens, and a -capsular fruit opening at the top with teeth. - -One of the commonest species we have to consider is the Sea Campion -(_Silene maritima_), common on nearly all coasts, and often growing in -small crevices of the bare rocks quite within the reach of the spray of -storm-waves. In common with the other members of its genus it is -characterised by a tubular calyx of united sepals, ten stamens, and a -three-celled capsule opening at the top with six teeth; but it may be -known at once by its small size, being only a few inches in height, and -its solitary flowers with calyx much inflated and the corolla only -shortly cleft. - -The Sea Sand Wort (_Spergularia marina_) is another common plant of the -coast, recognised by its slender, creeping stems; linear, stipuled, -fleshy leaves, convex below and blunt at the apex; and its pinkish-white -flowers. The Sea Purslane (_Honckenya peploides_), belonging to the same -order, is also a creeping plant, with ovate, acute fleshy leaves, -flowering from May to August. It is the only British plant of its genus, -and may be distinguished from others by the absence of stipules, -distinct sepals, petals entire, ten stamens, and from three to five -styles. The flowers are white, solitary, and sessile. The one remaining -species of the sea-side _Caryophyllaceae_ is the Sea Pearl Wort (_Sagina -maritima_). This plant is closely allied to the last, being a creeper -with exstipulate leaves and distinct sepals, but its flowers are reddish -white, on erect peduncles, with very small petals. The leaves, too, are -linear, fleshy, and obtuse. There are three distinct varieties of this -plant, two of which have erect stems with short internodes, while the -third is procumbent with long internodes; and in all three the capsules -are shorter than the sepals. - - [Illustration: FIG. 302.--THE SEA CAMPION] - -A variety of the Common Milk Wort (_Polygala vulgaris_)--order -_Polygalaceae_--is moderately common on sandy shores. The ordinary form -of the species, which is so common on heaths, is a small plant with a -woody stem, small ovate leaves crowded below, and opposite lanceolate -leaves above. The flowers are irregular with five persistent sepals, two -larger than the others; three to five petals, the lowest keeled, and all -united to the tube formed by the eight stamens, which are divided above -into two bundles; and the fruit is a flat capsule with two one-seeded -cells. The flowers are very variable in colour, being white, pink, -lilac, or blue; and the seeds are downy. The sea-side variety -(_oxyptera_) has smaller flowers than the normal form, and the wings of -the calyx are narrower. - -One species of Pansy (_Viola Curtisii_) is occasionally to be met with -on sandy shores, and may be at once recognised as one of the _Violaceae_ -by its irregular spurred corolla, its five persistent sepals, and the -three-parted, one-celled ovary. The flowers are variable in colour and -size, the prevailing tints being blue and yellow, and the diameter of -the corolla occasionally reaching to one inch. It has a creeping woody -rootstock, and a rough angular stem; and the petals are generally but -little longer than the sepals. - - [Illustration: FIG. 303.--THE SEA PEARL WORT] - - [Illustration: FIG. 304.--THE SHRUBBY MIGNONETTE] - -The Shrubby Mignonette (_Reseda suffruticulosa_), of the order -_Resedaceae_, is a common sea-side plant that grows to a height of one or -two feet on sandy shores, bearing spikes of white flowers in July and -August. The order is characterised by alternate exstipulate leaves, -persistent calyx with four or five sepals, corolla of from four to seven -petals, many stamens, and a three-lobed, one-celled ovary. The sea-side -species is very much like the wild mignonette so common in chalky -districts, but differs in having all its leaves pinnate, waved, and -glaucous, with linear segments; and in having five _equal_ sepals and -petals. In a variety of the species, however, the sepals and petals are -six in number. - -The Crucifers are fairly well represented by coast plants, there being -several maritime species of the order. The _Cruciferae_ are named from -the nature of the corolla, the limbs of the four petals of which are -arranged so as to resemble the Maltese cross. The flowers have also four -sepals, six stamens, two of which are shorter than the other four, and -the fruit takes the form of a two-celled pod or pouch which opens by the -separation of its two valves from the central partition. - - [Illustration: FIG. 305.--THE WILD CABBAGE] - - [Illustration: FIG. 306.--THE ISLE OF MAN CABBAGE] - -Our first example is the Wild Cabbage (_Brassica oleracea_), which, -although so unlike the cabbage of our gardens, is really the parent of -all the cultivated varieties, including the cauliflower, broccoli, -Brussels sprouts, &c. It is a biennial plant, with fleshy lobed wavy -leaves that are covered with bluish bloom, and a fleshy cylindrical -root. It grows erect to a height of one or two feet, bearing yellow -flowers during the summer months. An allied species (_B. monensis_), -with a prostrate stem and deeply-divided leaves, occurs locally on the -sandy shores of the Isle of Man. - -Two species of Stock (_Matthiola_) are to be found on the coast, both -being characterised by purple flowers. The Great Sea Stock (_M. -sinuata_) is a rare plant growing on the shores of Wales and Cornwall, -and may be known by its herbaceous stem and narrow downy leaves; and the -other species--the Hoary Shrubby Stock (_M. incana_)--is also a rare -plant, found principally on the cliffs of the Isle of Wight, and is the -parent of the Brompton Stocks of our gardens. The latter has a branched -woody stem and narrow leaves. Both species grow to a height of about -eighteen inches, and the latter flowers in May and June, while the -former is in bloom during the hottest summer months. - -The Hare's-ear Treacle Mustard (_Erysimum orientale_) is a rare -crucifer, frequenting the cliffs of the southern and eastern counties. -It grows to a height of one to two feet, and bears its white flowers -about midsummer. It has glaucous leaves, and the fruit-pods are -quadrangular in form. - - [Illustration: FIG. 307.--THE GREAT SEA STOCK] - - [Illustration: FIG. 308.--THE HOARY SHRUBBY STOCK] - -The Common Scurvy Grass (_Cochlearia officinalis_) is abundant on many -shores, and its fleshy leaves, once highly valued as an antiscorbutic, -are still used for salad by the cottagers near the sea. It generally -grows to a height of six or seven inches, and displays its white flowers -during late spring and early summer. The root-leaves are cordate in -form, and the upper ones are sessile and angled, half embracing the -stem. The fruit is a rounded pouch. A variety (_danica_) with stalked, -deltoid leaves and an oval veiny pod, is _plentiful_ in some places. - - [Illustration: FIG. 309.--THE SCURVY GRASS] - - [Illustration: FIG. 310.--THE SEA RADISH] - -On some coasts we find the Sweet Alyssum (_Koniga maritima_)--a -naturalised plant with procumbent stem, narrow lanceolate, acute -leaves, and white flowers. It may be recognised by its compressed, -pointed pouch with one-seeded cells. This species flowers towards the -end of the summer. - -The Sea Radish (_Raphanus maritimus_) is a much larger plant, growing -three or four feet in height. In common with the Wild Radish of our -corn-fields, it has a tapering pod divided into one-seeded joints, but -it may be distinguished from the latter by its superior height and the -deeply-divided radical leaves. Its flowers are always yellow, while in -the field species they may be either yellow or white; and the style is -also shorter, being about the same length as the last joint of the pod. - -On sandy shores the Sea Rocket (_Cakile maritima_) is commonly seen, and -is readily distinguished by its zigzag branches, deeply-lobed, smooth, -fleshy leaves of a glaucous colour, and its succulent pod, which is -divided into two one-seeded cells by a horizontal partition. It grows -from one to two feet high, and bears pretty lilac flowers about -midsummer. - - [Illustration: FIG. 311.--THE SEA ROCKET] - -Our last example of the crucifers is the Sea Kale (_Crambe maritima_), a -hardy perennial, commonly seen growing among the sand and shingle of the -shore, which is the parent of the sea kale now so commonly cultivated in -our market gardens. It may be readily recognised by the fine glaucous -bloom of its stem, and its broad wavy toothed leaves of a glaucous grey -colour. It grows to a height of about eighteen inches, and bears white -flowers in June. The fruit is a two-jointed pouch, the upper being -rounded and one-seeded, while the lower is stalk-like and barren. This -plant is particularly common in the south-west of England, where the -leaves are sometimes blanched for food by burying them in the sand. - -One of the most striking plants of the coast is the Yellow Horned Poppy -(_Glaucium luteum_) of the order _Papaveraceae_, which contains the -well-known poppies of corn-fields. The general characteristics of the -order are two deciduous sepals, four petals, many stamens inserted below -the ovary, and the ovary one-celled with membranous divisions. The -plants of this species usually contain a milky juice, have alternate -leaves without stipules, and the flowers, which are regular, generally -nod when in bud. The Horned Poppy is a very conspicuous plant, usually -growing quite alone on some inaccessible portion of the cliff, or among -the pebbles or shingle not far from high-water mark. Its stem is -glaucous and branched, and the large waved and deeply-cut leaves, which -clasp the stem, are also of a glaucous hue. The flowers are rendered -conspicuous by their large yellow petals, which, however, last only for -a day, and are succeeded by the hornlike seed-pods that sometimes reach -a foot in length. - - [Illustration: FIG. 312.--THE SEA KALE] - -We will conclude our list of sea-side flowers by a brief mention of the -Lesser Meadow Rue (_Thalictrum minus_), a variety of which (_maritimum_) -grows on sandy shores. The Meadow Rue belongs to the _Ranunculaceae_, as -may be seen from the fruit of several distinct carpels, each containing -a single seed, the corolla of distinct petals, and the numerous stamens -inserted below the carpels. The normal form of the Lesser Meadow Rue, -which grows freely in some chalky pastures and thickets, has leaves -three or four times pinnate, and lax panicles of drooping flowers -without any petals. The sea-side variety differs from this in having the -stem leafless at the base, and the panicles leafless and broad. The -flowers are greenish white, and bloom in July and August. - - [Illustration: FIG. 313.--THE HORNED POPPY] - -To assist the reader in the identification of sea-side flowers we append -a list of the orders to which they belong, together with the principal -distinguishing characteristics of each. - - - - - SYNOPSIS OF THE NATURAL ORDERS - WHICH CONTAIN OUR PRINCIPAL - SEA-SIDE FLOWERING PLANTS - - - I. MONOCOTYLEDONS - - A. GLUMIFERAE - - FLOWERS WITHOUT A PERIANTH, ENCLOSED IN GLUMES - - =1. Gramineae=--Grassy plants with hollow stems enclosed in split - sheaths. Flowers generally bisexual with (usually) three - stamens. - - =2. Cyperaceae=--Grassy plants with solid stems and entire sheaths. - Flowers arranged in spikelets, unisexual or bisexual, with - from one to three stamens. - - - B. PETALOIDAE - - PERIANTH PETALOID - - =3. Juncaceae=--Rushes, with narrow leaves and small brown flowers. - Perianth 6-partite, with scarious segments. Stamens - usually 6; ovary superior; fruit a 3-valved capsule. - - =4. Naiadaceae=--Aquatic herbs with inconspicuous, unisexual or - bisexual flowers. Perianth absent or scale-like. Stamens - as many as the segments of the perianth. Fruit of from one - to four carpels--superior. - - =5. Alismaceae=--Aquatic plants with radical net-veined leaves, and - (generally) conspicuous, white, bisexual flowers. Perianth - 6-partite. Stamens 6. Fruit of many carpels--superior. - - =6. Liliaceae=--Herbs with narrow leaves and showy, bisexual - flowers. Perianth 6-partite. Stamens 6. Ovary superior, - 3-celled. Fruit a berry or capsule. - - II. DICOTYLEDONS - - A. CALYX, OR COROLLA, OR BOTH ABSENT - - =7. Euphorbiaceae=--Herbs with entire leaves and (generally) a milky - juice. Flowers small, unisexual, dioecious (male and - female flowers on separate plants), sometimes enclosed in - calyx-like bracts. Perianth 3- or 4-partite or absent. - Stamens one or more. Ovary inferior. Fruit separating - into carpels elastically. - - =8. Eleagnaceae=--Shrub with silvery scales, alternate, entire - leaves, and small, unisexual flowers--the staminate - flowers in catkins. Sepals of male flowers 3 or 4. Stamens - 4 to 8. Ovary superior. Fruit indehiscent (not splitting). - - =9. Polygonaceae=--Herbs with sheathing stipules, alternate leaves, - and small (generally) bisexual flowers. Stamens 5 to 8. - Ovary superior. Fruit indehiscent. - - =10. Chenopodiaceae=--Herbs with jointed stems and small unisexual or - bisexual flowers. Stamens usually 5, sometimes 1 or 2, - opposite the sepals. Ovary superior. Fruit indehiscent. - - B. PLANTS WITH BOTH CALYX AND COROLLA - - - _a._ COROLLA MONOPETALOUS - - 1. _Ovary Superior and Stamens generally on the Corolla_ - - =11. Plantaginaceae=--Herbs with radical entire leaves, and spikes - of small, green flowers. Calyx 4-cleft. Corolla 4-lobed, - scarious. Stamens 4. Ovary 2- to 4-celled. Fruit - many-seeded. - - =12. Plumbaginaceae=--Herbs with radical or alternate leaves, and - (generally) regular, blue flowers. Calyx tubular, - scarious. Corolla of 5 petals, united below. Stamens 5, - opposite the petals, attached below the ovary. Ovary - 1-celled and 1-seeded. - - =13. Primulaceae=--Herbs with (generally) radical leaves and - conspicuous, regular flowers. Calyx 4- to 7-cleft. Corolla - 4- to 7-cleft. Stamens 4 to 7, generally opposite the - petals. Ovary 1-celled. Fruit a capsule with many seeds. - - =14. Solanaceae=--Herbs with alternate leaves and axillary clusters - of regular flowers. Calyx 5-cleft. Corolla 5-cleft. - Stamens 4 or 5. Ovary 2-celled. Fruit a berry. - - =15. Convolvulaceae=--Climbing herbs with alternate leaves and showy, - regular flowers. Sepals 5. Corolla 4- or 5-lobed. Stamens - 4 or 5. Ovary 2- to 4-celled. Fruit a capsule. - - =16. Gentianaceae=--Herbs with opposite entire leaves and solitary - regular flowers. Calyx 4- to 10-lobed. Corolla 4- to - 10-lobed. Stamens 4 to 10, alternate with the lobes of the - corolla. Ovary 1- or 2-celled. Fruit a capsule. - - 2. _Ovary Inferior and Stamens on the Corolla_ - - =17. Compositae=--Herbs with flowers (generally yellow or white) - collected into compact heads. Calyx absent or represented - by a pappus. Corolla tubular or ligulate. Stamens 4 or 5. - - _b._ COROLLA POLYPETALOUS - - 1. _Stamens Perigynous_ (_around the Ovary_), _or Epigynous_ - (_upon the Ovary_) - - =18. Umbelliferae=--Herbs with (generally) compound leaves, and - small, white, umbelled flowers. Sepals (if present) 5. - Petals 5. Stamens 5. Ovary inferior. Fruit of two - adhering carpels. - - =19. Illecebraceae=--Small herbs with sessile, entire leaves, and - small flowers. Sepals 4 or 5. Petals 4 or 5 or absent. - Stamens 1 to 5. Ovary superior. - - =20. Tamariscaceae=--Shrub with small, scale-like leaves, and lateral - spikes of small regular flowers. Sepals 4 or 5. Petals 4 - or 5. Stamens 4 or more. - - =21. Leguminosae=--Herbs or shrubs with alternate, stipuled, pinnate - or ternate leaves, sometimes tendrilled, and irregular - flowers. Sepals 4 or 5. Corolla of 5 petals, - papilionaceous (butterfly-like). Stamens usually 10. Ovary - superior. Fruit a pod. - - 2. _Stamens Hypogynous_ (_attached below the Ovary_) - - =22. Geraniaceae=--Herbs with stipuled, lobed leaves, and showy - regular flowers. Sepals 5. Petals 5. Stamens 5 or 10. - Fruit of 5 carpels surrounding a long beak. - - =23. Malvaceae=--Herbs with alternate, stipuled leaves, and axillary, - red, or purple flowers. Sepals 5. Petals 5, twisted in the - bud. Stamens numerous, united into a tube. Ovary of many - cells. - - =24. Caryophyllaceae=--Herbs with (generally) jointed stems, opposite - leaves, and regular white or red flowers. Sepals 4 or 5. - Petals 4 or 5. Stamens 8 or 10. Fruit a 1-celled capsule - opening at the top with teeth. - - =25. Polygalaceae=--Herbs with alternate, simple leaves (without - stipules), and irregular flowers. Sepals 5, the inner - petal-like. Petals 3 to 5, unequal. Stamens 8, in two - clusters. Fruit a 2-celled capsule. - - =26. Violaceae=--Herbs with alternate, stipuled leaves and irregular - flowers. Sepals 5. Petals 5, unequal, the lower one - spurred. Stamens 5. Ovary 3-partite, but 1-celled. - - =27. Resedaceae=--Herbs or shrubs with alternate, exstipulate leaves, - and spikes of irregular, green flowers. Sepals 4 or 5. - Petals 4 to 7, unequal. Stamens more than 10. Ovary - 3-lobed, and 1-celled. - - =28. Cruciferae=--Herbs with alternate, exstipulate leaves, and - regular flowers. Sepals 4. Petals 4, cruciate. Stamens - 6--4 longer and 2 shorter. Ovary 1- or 2-celled. Fruit a - siliqua or a silicula. - - =29. Papaveraceae=--Herbs with alternate, exstipulate leaves, a milky - juice, and regular, showy flowers. Sepals 2, deciduous. - Petals 4. Stamens numerous. Ovary 1-celled with membranous - partitions. - - =30. Ranunculaceae=--Herbs with (generally) alternate leaves and - regular flowers. Sepals generally 5, distinct. Petals 5 or - more. Stamens numerous. Fruit of many, distinct carpels. - - - - - INDEX - - - Acalephae, 134 - - Acanthias, 319 - - Acarina, 304 - - Aclis, 246 - - Acmaea, 240 - - Acorn Barnacles, 263 - - Actinia, 142 - - Actinoloba, 143 - - Actora, 300 - - Adamsia, 154 - - Adeorbis, 243 - - AEgirus, 235 - - AEolidae, 235 - - Aepus, 303 - - Agonus, 335 - - Aiptasia, 144 - - Alaria, 385 - - Alcyonium, 155 - - Algae, 344, 347 - - -- reproduction, 351 - - Alismaceae, 401, 423 - - Allseed, 413 - - Alopecurus, 397 - - Ambulacrum, 163 - - Ammodytes, 326 - - Ammophila, 396 - - Amoeba, 102 - - Amphibia, 307 - - Amphipoda, 267, 304 - - Anarrhichas, 334 - - Anatinidae, 204, 255 - - Anemones, 127, 138 - - Angiosperms, 346, 348 - - Angler Fish, 336 - - Angling, 34 - - Anguilla, 324 - - Anguillidae, 323 - - Angular Crab, 289 - - Annelida, 177 - - Anomia, 222 - - Anomura, 279 - - Antedon, 160 - - Anthea, 149 - - Anurida, 299 - - Apetalae, 402 - - Aphaniptera, 305 - - Aphrodita, 179 - - Apium, 412 - - Aporrhais, 245 - - Aquarium, 51 - - -- aeration of, 61, 63 - - -- cement for, 54, 57 - - -- construction of, 53 - - -- fountain, 64 - - -- temporary, 52 - - -- weeds for, 61 - - Arachnoidea, 257, 293, 304 - - Araneidae, 304 - - Arca, 216 - - Arcadae, 216, 255 - - Arctopsis, 289 - - Arenicola, 178 - - Armeria, 408 - - Artemisia, 410 - - Arthropoda, 255 - - -- classification, 304 - - Asiphonida, 198, 216, 255 - - Asparagus, 402 - - Asperococcus, 383 - - Astarte, 212 - - Aster, 410 - - Asteroidea, 171 - - Atherina, 332 - - Atherinidae, 332 - - Atriplex, 406 - - Aurelia, 135 - - Aviculidae, 219, 255 - - - Badderlocks, 385 - - Baits, 39 - - Balanophyllia, 152 - - Balanus, 6, 263 - - Banded Cockle, 216 - - Barley Grasses, 395 - - Barnacles, 261 - - Bass, 338 - - Beach Fleas, 263 - - Beadlet, 142 - - Beard Grass, 397 - - Beet, 405 - - Bembidiidae, 301 - - Bembidium, 302 - - Beroe, 137 - - Bittersweet, 409 - - Bledius, 304 - - Blennies, 332 - - Blenniidae, 332 - - Blennius, 334 - - Blue Shark, 320 - - Bonnet Limpet, 240 - - Bopyrus, 267 - - Boring Pill-ball, 268 - - Boring Sponge, 124 - - Bottle-brush, 132 - - Brachelytra, 303 - - Brachiopods, 224 - - Brachyura, 271, 279, 285, 304 - - Branchiopoda, 265, 304 - - Brassica, 418 - - Bread-crumb Sponge, 123 - - Bristle-tails, 298 - - Brittle Starfish, 157, 159, 161 - - Broad-clawed Crab, 280 - - Brome Grasses, 395 - - Bromus, 395 - - Bryopsis, 354 - - Bryozoa, 188 - - Buccinidae, 248, 255 - - Buccinum, 248 - - Bugs, 297 - - Bulla, 236 - - Bull-heads, 335 - - Bull Huss, 320 - - Bunodes, 150 - - Butter Gunnel, 334 - - Byssus, 43, 195 - - - Cabinets, 89 - - Caecum, 245 - - Cakile, 420 - - Calamary, 252 - - Calcarea, 119 - - Calcareous Sponges, 119 - - Callianassa, 277 - - Calliblepharis, 367 - - Callionymus, 335 - - Callithamnion, 61, 358 - - Callophyllis, 365 - - Calpurna, 248 - - Calyptraea, 241 - - Calyptraeidae, 240, 255 - - Canary Grass, 396 - - Cancer, 292 - - Carangidae, 338 - - Caranx, 338 - - Carapace, 272 - - Carchariidae, 320 - - Carcharius, 320 - - Carcinus, 291 - - Cardiadae, 214, 255 - - Cardium, 214 - - Carex, 398 - - Carrageen Moss, 61, 364 - - Caryophyllaceae, 415, 425 - - Caryophyllia, 151 - - Catometopa, 286, 289 - - Cave-dweller, 147 - - Cell for live objects, 95 - - Cement for aquarium, 57 - - Centaury, 409 - - Centipedes, 305 - - Cephalophora, 191, 225, 255 - - Cephalopoda, 191, 250, 255 - - Ceramiaceae, 358, 389 - - Ceramium, 61, 362 - - Cerati-solen, 207 - - Cerithiadae, 245, 255 - - Cerithium, 245 - - Cetacea, 340 - - Chaetopoda, 177 - - Chalina, 122 - - Chalk, 109 - - Chambered Mussel, 219 - - Channelled Wrack, 387 - - Charales, 343, 348 - - Chenopodiaceae, 405, 424 - - Chenopodium, 405 - - Chilognatha, 305 - - Chilopoda, 305 - - Chironomus, 301 - - Chiton, 237 - - Chitonidae, 237, 255 - - Chlorophyll, 74 - - Chlorospermeae, 350, 389 - - Chondria, 374 - - Chondrus, 61, 364 - - Chorda, 385 - - Chordaria, 381 - - Chordariaceae, 380, 390 - - Chrysaora, 136 - - Chylocladia, 364 - - Cillenium, 303 - - Circe, 212 - - Cirripedia, 261, 304 - - Cladophora, 352 - - Cladostephus, 380 - - Cliffs, 2 - - Cliona, 124 - - Cloak Anemone, 154 - - Club-mosses, 345 - - Club Rush, 399 - - Clupea, 322 - - Clupeidae, 322 - - Coast--general characters of, 1 - - Cochlearia, 419 - - Cockles, 214 - - Cod, 327 - - Codium, 353 - - Coelenterates, 127 - - Coelopa, 300 - - Coleoptera, 301, 305 - - Columella, 226 - - Common sponges, 119 - - Compositae, 410, 425 - - Cone Shells, 248 - - Conidae, 248, 255 - - Coniferae, 347, 348 - - Confervaceae, 352, 389 - - Convolvulaceae, 409, 425 - - Convolvulus, 409 - - Copepoda, 264, 304 - - Corallina, 61, 369 - - Corallinaceae, 369, 390 - - Corallines--preserving 87 - - Corals, 151 - - Corbula, 206 - - Cord Grass, 398 - - Cordylecladia, 366 - - Cornish Sucker, 330 - - Corrosive sublimate, 75 - - Corystes, 286 - - Cottidae, 335 - - Cottus, 335 - - Cowries, 247 - - Crab-pots, 26 - - Crabs--as bait, 44 - - -- preserving, 81 - - Crambe, 420 - - Crangon, 278 - - Crenella, 219 - - Crinoidea, 171 - - Crithmum, 411 - - Cruciferae, 417, 426 - - Crustacea, 257, 304 - - Crustaceans--preserving, 80 - - Cryptogams, 343, 347 - - Cryptonemiaceae, 363, 389 - - Ctenophora, 137 - - Cup Coral, 151 - - Cup-and-saucer Limpet, 240 - - Cutleria, 382 - - Cuttlefishes, 191, 251, 253 - - Cycadeae, 347, 348 - - Cyclometopa, 286, 291 - - Cyclostomata, 307, 308 - - Cydippe, 137 - - Cynodon, 396 - - Cyperaceae, 398, 423 - - Cypraea, 248 - - Cypraeidae, 247, 255 - - Cyprina, 212 - - Cyprinidae, 212, 255 - - Cystoclonium, 365 - - Cystoseira, 387 - - Cythere, 266 - - Cytheria, 211 - - Cyttidae 338 - - - Dactylopteridae, 335 - - Dahlia Wartlet, 143 - - Daisy Anemone, 146 - - Danica, 419 - - Dasya, 376 - - Daucus, 411 - - Dead Men's Fingers, 155 - - Decapoda (Decapods), 251, 255, 269, 271, 279, 304 - - Delesseria, 366, 368 - - Delphinidae, 340 - - Demospongia, 119 - - Dendronotus, 235 - - Dentaliadae, 238, 255 - - Desmarestia, 385 - - Devon Cup-coral, 151 - - Dibranchiata, 251, 255 - - Dicotyledons, 347, 403, 424 - - Dictyosiphon, 383 - - Dictyotaceae, 382, 390 - - Dillisk, 365 - - Diotis, 410 - - Diptera, 299, 305 - - Dissecting microscope, 91 - - Dissecting trough, 98 - - Dissection, 91 - - Dog-fishes, 318 - - Dog Whelks, 248 - - Dog Winkles, 248 - - Dog's-tooth Grass, 396 - - Dolichopodidae, 300 - - Dolphin, 340 - - Donax, 208 - - Doridae, 235 - - Doto, 235 - - Dragonet, 335 - - Dredge, 26 - - Dreissina, 219 - - Dromia, 282 - - Dulse, 61, 365 - - Dumontia, 363 - - Dyschirius, 304 - - - Ear-shell, 242 - - Echinocyamus, 168 - - Echinoderms, 157 - - Echinoidea, 171 - - Echinus, 168 - - Ectocarpaceae, 378, 390 - - Ectocarpus, 378 - - Edible Cockle, 214 - - Edible Crab, 292 - - Edible Mussel, 217 - - Edriophthalmata, 266, 304 - - Eel, 323 - - Elachista, 381 - - Elasmobranchii, 318 - - Eleagnaceae, 403, 424 - - Eleocharis, 399 - - Elymus, 395 - - Elysia, 235 - - Emarginula, 242 - - Enteromorpha, 61, 355 - - Entomostraca, 266, 304 - - Equisetales, 345, 348 - - Erato, 248 - - Erodium, 414 - - Eryngium, 412 - - Eryngo, 412 - - Erysimum, 418 - - Erythraea, 409 - - Establishment of port, 17 - - Eulima, 246 - - Euphorbia, 403 - - Euphorbiaceae, 403, 424 - - Euplexoptera, 305 - - Exogenae, 402 - - - Father Lasher, 335 - - Feather Starfish, 159, 160 - - Ferns, 345 - - Fescue Grass, 396 - - Festuca, 396 - - Filicales, 345, 348 - - Fishes, 307 - - -- classification, 318 - - -- colour of, 313 - - -- distribution, 317 - - -- fins of, 311 - - -- gills, 312 - - -- preserving, 85 - - -- scales of, 309 - - -- skeleton, 314 - - -- tails, 315 - - Fishing, 34 - - Fishing Frog, 336 - - Fissurella, 241 - - Fissurellidae, 241, 255 - - Five-fingered Starfish, 157 - - Flat-fishes, 324 - - Floating Crab, 289 - - Flounders, 325 - - Flowering Plants--classification, 423 - - Flowers--fertilisation, 393 - - -- preserving, 86 - - -- structure, 346 - - Flustra, 188 - - Flying Gurnards, 335 - - Foraminifera, 106 - - Formaldehyde, 73 - - Fox-tail Grass, 398 - - Fragacea, 142 - - Fucaceae, 386, 390 - - Fucus, 386 - - Fungi, 344, 347 - - Furbelows, 384 - - Furcellaria, 364 - - Fusus, 249 - - - Gadiadae, 327 - - Gadus, 327 - - Galeomma, 214 - - Gamopetalae, 403 - - Gaper shell, 205 - - Gasteropoda, 232, 255 - - Gastrochaena, 203 - - Gastrochaenidae, 203, 255 - - Gastrosteidae, 331 - - Gastrosteus, 331 - - Gebia, 276 - - Gelidiaceae, 390 - - Gelidium, 367 - - Gem Pimplet, 150 - - Gentianaceae, 409, 425 - - Geodephaga, 301 - - Gephyrea, 176 - - Geraniaceae, 414, 425 - - Gibb's Crab, 289 - - Gigartina, 364 - - Glass-wort, 407 - - Glaucium, 420 - - Globigerina, 109 - - Globular Beroe, 137 - - Gloisiphonia, 364 - - Glumiferae, 423 - - Glycerine, 73 - - Goadby's fluid, 73 - - Gobies, 334 - - Gobiidae, 334 - - Gobioesocidae, 330 - - Gobius, 334 - - Golden Samphire, 411 - - Gonoplax, 290 - - Goosefoot, 405 - - Gracilaria, 366 - - Gramineae, 392, 423 - - Grantia, 120 - - Grass-wracks, 400 - - Green Laver, 61 - - Green Pea-urchin, 168 - - Grey Mullet, 332 - - Griffithsia, 61, 360 - - Ground bait, 49 - - Gurnards, 335 - - Gymnosperms, 346, 348 - - - Haddock, 327 - - Hake, 328 - - Halecium, 131 - - Halibut, 326 - - Halichondria, 123 - - Halidrys, 388 - - Haliotidae, 242, 255 - - Haliotis, 242 - - Halurus, 361 - - Hapalidiaceae, 390 - - Hare's Ear, 418 - - Heart Cockle, 212 - - Heart Urchin, 168 - - Helminthocladiae, 389 - - Henslow's Crab, 293 - - Henware, 385 - - Hepaticae, 344, 348 - - Hermit Crab, 44, 154, 280, 232 - - Herring, 322 - - Herring-bone Polype, 131 - - Hexactinellida, 119 - - Himanthalia, 387 - - Hippoglossus, 326 - - Hippophae, 403 - - Hog-louse, 268 - - Holostomata, 236, 255 - - Holothuroidea, 169 - - Homarus, 274 - - Honckenya, 416 - - Honeyware, 385 - - Hook-nose, 335 - - Hooks--fishing, 37 - - Hordeum, 395 - - Horned Poppy, 420 - - Horse Limpet, 240 - - Horse Mackerel, 338 - - Horse Mussels, 218 - - Horsetails, 345 - - Hydrozoa, 130 - - Hymenoptera, 305 - - Hypnaea, 365 - - - Ianthina, 242 - - Illecebraceae, 412, 425 - - Inachus, 289 - - Infusoria, 104, 112 - - Insecta (Insects), 257, 294, 305 - - Inula, 411 - - Iridaea, 364 - - Irish Moss, 61, 364 - - Isocardia, 212 - - Isopoda, 267, 304 - - Isotoma, 299 - - - Jania, 370 - - Jelly-fishes, 127, 134 - - John Dory, 338 - - Juncaceae, 400, 423 - - Juncus, 400 - - - Keyhole Limpet, 241 - - Knappia, 397 - - Knot-grasses, 404 - - Knotted Wrack, 386 - - Koniga, 419 - - - Labial palpi, 197 - - Labridae, 329 - - Lactuca, 410 - - Lacuna, 244 - - Lady Crab, 292 - - Lamellibranchiata (Lamellibranchs), 191, 192, 255 - - Laminaria, 384 - - Laminariaceae, 384, 390 - - Lampreys, 308 - - Lathyrus, 413 - - Laurencia, 370 - - Laurenciaceae, 370, 390 - - Lavatera, 415 - - Laver, 61, 354 - - Leathesia, 381 - - Leda, 217 - - Leguminosae, 413, 425 - - Lemon Sole, 326 - - Lenses, 91 - - Lepadogaster, 330 - - Lepidoptera, 305 - - Lepturus, 395 - - Lesser Rue, 422 - - Leucosolenia, 121 - - Ligia, 268 - - Liliaceae, 402, 423 - - Limnoria, 268 - - Limpets, 43, 238 - - Ling, 328 - - Lithodes, 282 - - Litosiphon, 383 - - Little Lettuce, 410 - - Littorina, 243 - - Littorinidae, 244, 255 - - Liverworts, 344 - - Lobster pots, 26 - - Lobsters, 274 - preserving, 81 - - Loligo, 252 - - Lomentaria, 371 - - Long-armed Crab, 286 - - Lophius, 336 - - Lucinidae, 213, 255 - - Lugworm, 39, 178 - - Lutraria, 209 - - Lycopodiales, 345, 348 - - - Machilis, 298 - - Mackerel, 337 - - Macrura, 271, 279, 304 - - Mactra, 209 - - Mactridae, 209, 255 - - Maia, 289 - - Malacostraca, 266, 304 - - Malvaceae, 415, 425 - - Mammals, 307, 339 - - Mantis Shrimps, 270 - - Marginella, 248 - - Marine aquarium, 51 - - Marsipobranchii, 308 - - Mat-grass, 396 - - Matricaria, 411 - - Matthiola, 418 - - Maugeria, 366 - - Meadow Grasses, 395 - - Meadow Rue, 421 - - Medusae, 134 - - Medusoids, 133 - - Melanospermeae, 350, 376, 290 - - Melobesia, 370 - - Merluccius, 328 - - Mesembryanthemum, 142 - - Mesenteries, 139 - - Mesogloia, 381 - - Methylated spirit, 72 - - Michaelmas Daisy, 410 - - Micralymma, 303 - - Milkwort, 416 - - Millepedes, 305 - - Modiola, 218 - - Molluscs, 190 - - -- bivalve, 192 - - -- classification, 255 - - Molva, 328 - - Monera, 110 - - Monocotyledons, 347, 391, 423 - - Montagu's Sucker, 331 - - Morone, 338 - - Moss Polyps, 188 - - Mosses, 344 - - Motella, 328 - - Mud-burrower, 277 - - Mugil, 332 - - Mugilidae, 332 - - Mullidae, 338 - - Mullus, 338 - - Murex, 249 - - Muricidae, 249, 255 - - Murlins, 385 - - Musci, 344, 348 - - Muscineae, 343, 344, 348 - - Museum, 88 - - Mussels, 42, 217 - - Mustelus, 320 - - Mya, 205 - - Myacidae, 205, 255 - - Myrionema, 381 - - Myriopoda, 257, 305 - - Myriotrichia, 379 - - Mytilidae, 217, 255 - - Mytilus, 217 - - - Naiadaceae, 400, 423 - - Nassa, 249 - - Natica, 246 - - Naticidae, 246, 255 - - Nautilidae, 255 - - Needle-fish, 329 - - Nephrops, 275 - - Nereis, 284 - - Nerophis, 329 - - Nesaea, 268 - - Nets, Collecting, 23 - - Neuroptera, 305 - - Nitophyllum, 367 - - Noctiluca, 114 - - Norway Lobster, 275 - - Notched Limpets, 242 - - Nucleobranchiata, 232, 255 - - Nucula, 217 - - Nudibranchiata, 233, 255 - - Nummulites, 108 - - Nummulitic limestone, 110 - - Nurse Dog, 320 - - Nut Crabs, 286 - - - Obione, 405 - - Octopoda, 251, 255 - - Octopus, 251 - - Odonthalia, 375 - - Odostomia, 246 - - OEpophilus, 297 - - Oleasters, 403 - - Oligochaeta, 177 - - Omar, 242 - - Oniscoda, 268 - - Opelet, 149 - - Operculum, 83, 227 - - Ophidiidae, 326 - - Ophiuroidea, 171 - - Opisthobranchiata, 232, 255 - - Opossum Shrimps, 270 - - Oraches, 406 - - Orange-disked Anemone, 148 - - Orthoptera, 305 - - Osmerus, 321 - - Ostracoda, 265, 304 - - Ostrea, 221 - - Ostreidae, 221, 255 - - Outdoor work, 21 - - Ovulum, 248 - - Oxyptera, 416 - - Oxyrhyncha, 286 - - Oxystomata, 286 - - Oysters, 221 - - - Padina, 382 - - Pagurus, 282, 285 - - Pallial line, 193 - - Pansy, 417 - - Papaveraceae, 420, 426 - - Parasitic Anemone, 153 - - Patella, 239 - - Patellidae, 255 - - Paternoster, 48 - - Pea Crabs, 289 - - Pea Urchin, 168 - - Peachia, 145 - - Pearl Oysters, 219 - - Pecten, 222 - - Pectunculus, 216 - - Pennant's Crab, 286 - - Pepper Dulse, 370 - - Pericardium, 196 - - Peristome, 226 - - Periwinkle, 62, 243 - - Petaloidae, 423 - - Phalaris, 396 - - Phanerogams, 343, 346, 348 - - Phasianella, 243 - - Pheasant Shell, 243 - - Phleum, 397 - - Phocaena, 340 - - Pholadidae, 199, 255 - - Pholadidea, 201 - - Pholas, 200 - - Phosphorescence, 18, 111 - - Phyllirhoidae, 286 - - Phyllophora, 365 - - Piddocks, 200 - - Pilchard, 322 - - Pileopsis, 241 - - Pilota, 361 - - Pimplet, 150 - - Pinna, 221 - - Pinna Pea-crab, 290 - - Pinnotheres, 290 - - Pipe-fishes, 328 - - Plaice, 325 - - Plantaginaceae, 408, 424 - - Plantago, 408 - - Plants, classification, 343, 347 - - Plate-gilled Molluscs, 191 - - Pleuronectes, 326 - - Pleuronectidae, 324 - - Plocamium, 61, 366 - - Plumbaginaceae, 408, 424 - - Poa, 396 - - Podded Sea-oak, 388 - - Podophthalmata, 266, 269, 304 - - Pogge, 335 - - Pollack, 327 - - Polybius, 293 - - Polycarpon, 413 - - Polychaeta, 177 - - Polygala, 416 - - Polygalaceae, 416, 426 - - Polygonaceae, 404, 424 - - Polygonum, 404 - - Polypetalae, 403 - - Polypogon, 397 - - Polysiphonia, 372 - - Polystomata, 115 - - Polyzoa, 188 - - Porcelain Crab, 280 - - Porcellana, 280 - - Porifera, 115 - - Porphyra, 355 - - Porpoise, 339 - - Portland Spurge, 403 - - Portunus, 292 - - Prawn, 44, 278 - - Preservation of marine objects, 71 - - Preservatives, 72 - - Prickly Cockle, 215 - - Prickly Salt-wort, 407 - - Primulaceae, 424 - - Prosobranchiata, 232, 236 - - Protophyta, 343, 347 - - Protoplasm, 102 - - Protoplasta, 104, 110 - - Protozoa, 102 - - -- classification, 104 - - Psammobia, 208 - - Pteropoda, 230, 255 - - Pulmonifera, 255 - - Punctaria, 383 - - Puncturella, 241 - - Purple Spurge, 403 - - Purple-tipped Urchin, 168 - - Purpura, 249 - - Pycnogonum, 293 - - Pyramidellidae, 246, 255 - - - Radiata, 140 - - Radiolaria, 104, 110 - - Ragworm, 40, 179 - - Raiidae, 318 - - Ranunculaceae, 422, 426 - - Raphanus, 420 - - Rays, 318 - - Red Mullets, 338 - - Red-specked Pimplet, 150 - - Reptilia, 307 - - Reseda, 417 - - Resedaceae, 417, 426 - - Rhizocarpeae, 345, 348 - - Rhizopods, 104 - - Rhizostoma, 136 - - Rhodomela, 372 - - Rhodomelaceae, 372, 390 - - Rhodophyllis, 61 - - Rhodospermeae, 350, 355, 389 - - Rhodymenia, 61, 365, 367 - - Rhodymeniaceae, 365, 389 - - Rhombus, 326 - - Rhynchota, 297, 305 - - Rissoa, 244 - - Rock-fishes, 46 - - Rocklings, 328 - - Rock-pools, 6, 31 - - Rosy Anemone, 149 - - Rosy Feather Star, 160 - - Rotifers, 189 - - Rushes, 400 - - Rytiphlaea, 375 - - - Sabella, 184 - - Saddle Oyster, 222 - - Sagartia, 146 - - Sagina, 416 - - Salicornia, 407 - - Salmo, 321 - - Salmon, 321 - - Salmon Dace, 339 - - Salmonidae, 321 - - Salsola, 407 - - Salt-wort, 407 - - Sand Eels, 326 - - Sandhoppers, 268 - - -- preserving, 81 - - Sand Smelts, 332 - - Sandworm, 178 - - Saxicava, 203 - - Scalaria, 244 - - Scallops, 222 - - Scentless Mayweed, 411 - - Schizopoda, 304 - - Schizymenia, 61, 364 - - Scirpus, 399 - - Scomber, 337 - - Scomberidae, 337 - - Scorpionidae, 304 - - Scorpion Spider-crab, 289 - - Scurvy Grass, 419 - - Scylliidae, 319 - - Scyllium, 319 - - Sea angling, 34 - - -- Aster, 410 - - -- Buckthorn, 403 - - -- Bullheads, 335 - - -- Bream, 338 - - -- Campion, 415 - - -- Carrot, 411 - - -- Cat, 334 - - -- Cat's-tail Grass, 397 - - -- Cucumbers, 169 - - -- Devil, 336 - - -- Eggs, 165 - - -- -- preserving, 79 - - -- Girdles, 384 - - -- Grass, 61, 353, 400 - - -- Hard-grass, 395 - - -- Holly, 412 - - -- Kale, 420 - - -- Lavender, 409 - - -- Lemons, 233 - - -- Lettuce, 61 - - -- Loach, 328 - - -- Lyme-grass, 395 - - -- Mallow, 415 - - -- Mat, 188 - - -- Meadow Grass, 396 - - -- Mouse, 179 - - -- Pearl-wort, 416 - - -- Perch, 338 - - -- Pill-ball, 268 - - -- Pink, 408 - - -- Purslane, 406, 416 - - -- Radish, 420 - - -- Reed, 396 - - -- Rocket, 420 - - -- Rushes, 400 - - -- Salt, 17, 59 - - -- Saltness of, 17 - - -- Samphire, 411 - - -- Sand-wort, 415 - - -- Sedge, 398 - - -- Slater, 268 - - -- Slugs, 233 - - -- Snails, 331 - - -- Spurge, 403 - - -- Squirts, 188 - - -- Stock, 418 - - -- Stork's-bill, 414 - - -- Urchins, 157, 165 - - -- -- preserving, 79 - - -- -- shell of, 166 - - -- teeth, 167 - - -- water, artificial, 59 - - -- composition, 59 - - -- weeds, 343 - - -- -- classification, 389 - - -- -- preserving, 86 - - -- Wormwood, 410 - - Seaside Arrow Grass, 401 - - -- Bindweed, 409 - - -- Cottonweed, 410 - - -- Feverfew, 411 - - -- Grasses, 392 - - -- Knot Grass, 404 - - -- Plantain, 408 - - -- plants, 391 - - -- classification, 423 - - Section cutting, 96 - - Sedges, 398 - - Selaginellales, 345, 348 - - Sepia, 253 - - Sepiadae, 253, 255 - - Sepiola, 252 - - Serpula, 185 - - Serranidae, 338 - - Serrated Pill-ball, 268 - - Serrated Wrack, 386 - - Sertularia, 128 - - Sessile-eyed crustaceans, 266 - - Shanny, 333 - - Sharks, 318 - - Shells, preserving, 83 - - Shore Crab, 261, 291 - - -- Spider, 293 - - Shrimps, 278 - - -- preserving, 81 - - Shrubby Mignonette, 417 - - Silene, 415 - - Silicia, 122 - - Siphonaceae, 358, 389 - - Siphonida, 198, 255 - - Siphonostomata, 236, 247, 255 - - Six-rayed Sponges, 119 - - Skates, 318 - - Slender-beaked Crab, 289 - - Sloke, 61, 355 - - Smelt, 321 - - Smooth Hound, 320 - - Snoods, 37 - - Solanaceae, 409, 424 - - Solanum, 409 - - Soldier Crab, 280 - - Sole, 326 - - Solea, 326 - - Solecurtus, 207 - - Solenidae, 255 - - Sparidae, 338 - - Spartina, 397 - - Sparus, 338 - - Spergularia, 415 - - Sphacelaria, 279 - - Sphaerococcoideae, 366, 390 - - Sphaerococcus, 366 - - Sphaeroma, 268 - - Spicules, 118 - - Spider Crabs, 288 - - Spike Rush, 399 - - Spiny-finned fishes, 329 - - Spirorbis, 187 - - Sponges, 115 - - Spongiocarpeae, 390 - - Spoon Worms, 176 - - Sporochnaceae, 385, 390 - - Sporochnus, 385 - - Spotted Dogfish, 320 - - Spotted Hog-louse, 268 - - Spout Shell, 245 - - Sprats, 323 - - Spring-tails, 299 - - Spurges, 403 - - Spyridia, 363 - - Spyridiaceae, 368, 389 - - Squamariae, 390 - - Squid, 252 - - Squirt Worms, 176 - - Stalk-eyed crustaceans, 266, 269 - - Starfishes, 157 - - -- preserving, 79 - - Stargazers, 336 - - Statice, 408 - - Stenorhynchus, 289 - - Sticklebacks, 331 - - Stilophora, 383 - - Sting Bull, 337 - - Sting Fish, 335 - - Stock, 418 - - Stomopoda, 269, 304 - - Stone Crab, 280 - - Strawberry Beadlet, 142 - - Sucker Fishes, 330 - - Sweet Alyssum, 419 - - Swimming Crab, 293 - - Sycon, 121 - - Syngnathidae, 328 - - Syngnathus, 329 - - - Tamariscaceae, 413, 425 - - Tamarisk, 413 - - Tangles, 384 - - Tapes, 211 - - Tealia, 143 - - Tectibranchiata, 238, 255 - - Tectibranchs, 236 - - Teleostomi, 318, 320 - - Tellina, 208 - - Tellinidae, 207, 255 - - Terebella, 181 - - Terebratulina, 225 - - Teredo, 201 - - Tetrabranchiata, 255 - - Thalictrum, 421 - - Thallophytes, 343, 344, 347 - - Trichoptera, 305 - - Thornback Crab, 289 - - Thracia, 204 - - Thrift, 408 - - Thuiaria, 132 - - Thysanoptera, 298, 305 - - Tides, 9 - - Tooth shells, 238 - - Top shells, 243 - - Trachinidae, 336 - - Trachinus, 337 - - Treacle Mustard, 418 - - Tree Mallow, 415 - - Trefoil, 413 - - Trifolium, 413 - - Triglochin, 401 - - Triopa, 235 - - Tritonia, 235 - - Tritoniadae, 235 - - Trivia, 248 - - Trochus, 243 - - Trumpet Anemone, 141 - - Tubularia, 132 - - Tunicates, 188 - - Turbellaria, 175 - - Turbinidae, 243, 255 - - Turbot, 326 - - Turkey-feather Laver, 382 - - Turret shells, 245 - - Turritella, 244 - - Turritellidae, 244, 255 - - Twin-bladder Wrack, 387 - - Two-spotted Sucker, 331 - - - Ulva, 61, 354 - - Ulvaceae, 389, 354 - - Umbelliferae, 411, 425 - - Umbilicus, 226 - - Umbo, 193 - - - Vascular cryptogams, 345 - - Velutina, 247 - - Velvet Crab, 292 - - Veneridae, 210, 255 - - Venus, 210 - - Vermes, 172 - - Vertebrates, 306 - - Vetch, 413 - - Vicia, 413 - - Viola, 417 - - Violaceae, 417, 426 - - Violet Fiddler, 292 - - - Water Ferns, 345 - - Weavers, 336 - - Wedge shells, 208 - - Whales, 340 - - Wheel animals, 189 - - Whelks, 248 - - Whirl Worms, 175 - - Whistle Fish, 328 - - Whitebait, 323 - - White Salmon, 339 - - Whiting, 327 - - Wild Cabbage, 418 - - Wild Celery, 412 - - Wing shells, 219 - - Wolf Fish, 334 - - Woody Nightshade, 409 - - Worms, 172 - - -- parasitic, 174 - - Worm Pipe-fish, 329 - - Wrangeliaceae, 389 - - Wrasses, 329 - - - Xantho, 292 - - Xylophaga, 201 - - - Yellow Poppy, 420 - - - Zeus, 338 - - Zoantharia, 138 - - Zoarces, 333 - - Zonaria, 382 - - Zostera, 353, 400 - - - _Printed in England at_ THE BALLANTYNE PRESS - SPOTTISWOODE, BALLANTYNE & CO. LTD. - _Colchester, London & Eton_ - - -Transcriber's Note - -Minor inconsistencies in the punctuation of tables or captions are -silently corrected. - -Hyphenation is variable. Those compound words which are hyphenated only -on line breaks are rendered using modern usage. - -The word 'movable' appears only once as 'moveable' (165), which is -retained. - -The index entry for 'OEpophilus' is considered to be an error. All -instances of the word appear in the text as 'AEpophilus'. This has been -corrected and moved to the appropriate alphabetic position. - -The following corrections were made to obvious printer's errors, - -devel[e/o]ped (336); co[n/m]posed (364); - -The following list contains punctuation corrections made: - - p. 65 one of them[.] Added. - - p. 255 [Class] =LAMELLIBRANCHIATA= Added to match other - entries. - - p. 257 their tendencies[,/.] Corrected. - - p. 292 low-water[-]mark Unhyphenated elsewhere. - - p. 340 [(]_Cetacea_) Added. - - p. 390 in firm gelatine[,/.] Corrected. - - p. 403 by its stipuled leaves[.] Added. - - p. 434 Rhodospermeae, 350, 355, 38[9] Added. - - - - - -End of the Project Gutenberg EBook of The Sea Shore, by William S. 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