A MANUAL OF ZOOLOGY GIF! 0? FROF.C.A.XOFOID PREFACE. IN issuing the first part of the present work in a second edition, and in bringing out the second, the Author has little to add to what he has already said. The chief point upon which it may be desirable to say a few words is, as to the object aimed at in the Introductory portion of the work. The Introduction is intended to exhibit to the student, in as brief a form as possible, the leading principles of Zoological Science. These principles are of the highest importance, and no adequate knowledge of Zoology can be attained without their full comprehension. At the same time, the principles in question depend, in many cases, upon data which are only evolved during the s-< stematic study of the subject. For this reason, it is not to be expected that the student should find himself fully able to comprehend the Introductory portion of the work, whilst still standing at the threshold of the subject. Whilst the student, therefore, will do well to glance over the Introduction before commencing the study of the systematic portion of the work, he must be prepared to find many points which he can only M1875S4 VI PREFACE. fully grasp after he has attained a knowledge of the leading modifications of structure exhibited in the Animal Kingdom. The Author has only to add that the first part of the work (on the Invertebrate Animals) has been carefully revised, and, as far as possible, brought up to the present level of the Science ; whilst the illustrations, with very few exceptions, have been drawn upon the wood by himself. EDINBURGH, December i, 1870. PREFACE TO FIRST EDITION OF PART I. IN bringing out the present work, the Author has been mainly guided by the recollection of his own difficulties as a student, and by the belief that he is supplying a distinct want. Many excellent and original works on Natural History are extant, but they mostly labour under disadvantages which more or less disqualify them as text-books for students. So vast, for instance, have been the additions to our Zoological knowledge within the last few years, that no work on Natural History, except the most recent ones, represents ade- quately the present state of the Science. Under this inevitable disqualification all the older Manuals labour. Other works again, of the most profound research, are unsuitable for ordinary students from their bulk, cost, and, more than all, from their very profundity. The Author's aim, therefore, has simply been to present to the ordinary student those leading facts in Natural History, the knowledge of which is essential, but which lie scattered through the pages of other larger and more costly works, inaccessible to those who merely I Vlil PREFACE. desire to learn the outlines of the Science. In carrying out this object, it is unnecessary for the Author to re- mark that he does not lay any claim to originality. He trusts, however, that he has succeeded in laying before his readers, not a mere mass of undigested facts, but something like an orderly and systematic review of the main points required to be known by the student. The Author is conscious of many imperfections in his plan, and also in the execution of his plan. The subject, however, is so extensive, and so constantly changing, that he can reasonably claim some indulgence, if the brief leisure-time of a busy life has not enabled him in every respect to keep abreast of the latest discoveries. Such defects as there may be, are, it is hoped, of such a nature as not to diminish the value of the work for ordinary students. Amongst the sources upon which the Author has mainly drawn, it is, perhaps, invidious to mention one more than another. He feels, however, bound to acknowledge with gratitude the very great assistance which he has derived from the various works of Pro- fessor Huxley. EDINBURGH, November 2, 1869. CONTENTS. PABT I.-IJSTVEBTEBRATE ANIMALS. GENERAL INTRODUCTION. PAGE Definition of Biology and Zoology — Differences between organised and unorganised bodies — Nature of life — Vital force — Differ- ences between animals and plants — Morphology and physiology — Differences between different animals — Specialisation of func- tions— Morphological type — Von Baer's law of development — Homology, analogy, and homomorphism — Correlation of growth — Classification — Definition of species — Impossibility of a linear classification — Reproduction — Sexual reproduction — Non-sexual reproduction — Gemmation and fission — Reproduction by internal gemmation — Alternation of generations — Parthenogenesis-— De- velopment, transformation, and metamorphosis — Spontaneous generation — Origin of species — Distribution, geographical and geological, 1-41 CHAPTER I. General characters of the Protozoa — Classification of the Protozoa — Gregarinidae — Psorospermiae, ...... 42-46 CHAPTER II. General characters of the Rhizopoda — Amcebea, . . . 46-50 CHAPTER III. Foraminifera — Classification of the Foraminifera — Bathybius — Cocco- liths, Coccospheres — Affinities of the Foraminifera — Distribution of Foraminifera in space — Distribution of Foraminifera in time, 50-57 CHAPTER IV. Radiolaria — Acanthometrse — Polycystina — Thalassicollida, . 57-6o CHAPTER V. Sponges — Nature of Sponges— Classification of Spongida — Distribu- tion of Sponges in space and in time — Affinities of Sponges, 60-65 CONTENTS. CHAPTER VI. Infusoria — Order Ciliata — Suctoria — Flagellata — Noctiluca — Phos- phoresence of the Sea, 66-73 CHAPTER VII. General characters of the Coelenterata — Divisions of the Coelenterata — Hydrozoa — General terminology of the Hydrozoa, . . 74~7& CHAPTER VIII. Divisions of the Hydrozoa — Sub-class Hydroida — Order Hydrida — Order Corynida — Reproduction of Hydroida — Sertularida — Cam- panularida, 78-88 CHAPTER IX. Siphonophora or Oceanic Hydrozoa — Calycophoridae — Divisions of Calycophoridae — Physophoridae — Divisions of Physophoridae, 89-95 CHAPTER X. Discophora — Structure of Medusidae — Value of Medusidae as an Order of Hydrozoa, . . 95'99 CHAPTER XI. Lucernarida — Steganophthalmate Medusas — Lucernariadae — Pelagidae — Rhizostomidae — Reproduction in Rhizostomidaa — Sub-class Graptolitidaa — Definition of the Sub-class — Structure of Grapto- lites, 99-107 CHAPTER XII. Distribution of Hydrozoa in space — Distribution of Hydrozoa in time — Oldhamia — Corynida — Sertularida — Graptolites, . . 107-109 CHAPTER XIII. General characters of the Actinozoa — Zoantharia Malacodermata — Actinidae — Ilyanthidae — Zoanthidse — Zoantharia Sclerobasica — Sclerobasic and Sclerodermic Corals — Antipathidae — Hyalone- madae — Zoantharia Sclerodermata — Gemmation and fission amongst Corals, 109-119 CHAPTER XIV. Alcyonaria — Alcyonidae — Tubiporidas — Pennatulidae — Gorgonidae — Red Coral, 119-122 CHAPTER XV. Rugosa — Distinctions between the Coralla of the different Orders of Actinozoa, ......... 123-124 CONTENTS. XI CHAPTER XVI. Ctenophora — General characters — Anatomy of Pleurobrachia — Divi- sions of Ctenophora, ...... . 124-128 CHAPTER XVII. Distribution of Actinozoa in space — Coral Reefs, their structure, and mode of origin — Distribution of Actinozoa in time — Tabular view of the divisions of the Zoantharia Sclerodermata and Rugosa, 129-134 CHAPTER XVIII. Annuloida — General characters of the Annuloida — General characters of the Echinodermata — Development of the Echinodermata — Divisions of Echinodermata, ' ...... JSS-IS^ CHAPTER XIX. Echinoidea — General characters — Anatomy of Echinus — Divisions of Echinoidea, ...... . . 138-144 CHAPTER XX. Asteroidea and Ophiuroidea — General characters of the Asteroidea — Divisions of the Asteroidea — General characters of the Ophiuroi- dea — Families of the Ophiuroidea, ..... 144-148 CHAPTER XXI. Crinoidea, Cystoidea, and Blastoidea — General characters of Crinoi- dea— Of Cystoidea — Of Blastoidea, ..... 148-153 CHAPTER XXII. Holothuroidea — General characters — Families of Holothuroidea, 153-155 CHAPTER XXIII. Distribution of Echinodermata in space — Distribution of Echinoder- mata in time — Crinoidea — Blastoidea — Cystoidea — Asteroidea — Ophiuroidea — Echinoidea — Holothuroidea, . . .155-158 CHAPTER XXIV. Scolecida — General characters of the class Scolecida — Entozoa — Platyelmia — Taeniada — Structure and development of the Tape- worm — Hydatids, ..... . . .158-164 CHAPTER XXV. Trematoda and Turbellaria — General characters of the Trematoda — General characters of the Turbellaria — Planarida — Nemer- tida, . . . . . ...... 164-168 Xll CONTENTS. CHAPTER XXVI. f Nematelmia — Acanthocephala — Gordiacea — Nematoda — Parasitic Nematoids — Free Nematoids, 168-172 CHAPTER XXVII. Rotifera— General characters of the Rotifera — Affinities of the Roti- fera, 172-176 CHAPTER XXVIII. Annulosa — General characters of the Annulosa — General characters of the Anarthropoda — Class Gephyrea — General characters of the class Annelida, 177-181 CHAPTER XXIX. Divisions of the Annelida — Hirudinea — Oligochseta — Tubicola— Errantia — Distribution of the Annelida in time— Tabular view of the Annelida— Class Chaetognatha, . 181-189 CHAPTER XXX. Arthropoda — General characters — Divisions of Arthropoda, . 190-191 CHAPTER XXXI. Crustacea — Characters of the class Crustacea — General morphology of Crustacea — Divisions of Crustacea, 191-198 CHAPTER XXXII. Epizoa — Ichthyophthira — Cirripedia — Characters of Cirripedia — De- velopment— Reproduction — Divisions, .... 198- 204 CHAPTER XXXIII. Entomostraca — Lophyropoda — Ostracoda — Copepoda — Branchio- poda — Cladocera — Phyllopoda — Trilobita — Merostomata — Xiphosura — Eurypterida, ....... 204-211 CHAPTER XXXIV. Malacostraca — Edriophthalmata — Lsemodipoda — Amphipoda — Iso- poda — Podophthalmata — Stomapoda — Decapoda — Macrura — Anomura — Brachyura, ...... .211-218 CHAPTER XXXV. Distribution of the Crustacea in space — Distribution of the Crustacea in time, ...... .... 219-220 CHAPTER XXXVI. General characters and divisions of the Arachnida, . . . 221-224 CONTENTS. xiii CHAPTER XXXVII. Divisions of the Arachnida — Podosomata — Acarina — A delarthroso- mata — Pedipalpi — Araneida, ...... 224-230 CHAPTER XXXVIII. Myriapoda — General characters of the class — Chilopoda — Chilog- natha — Distribution of Myriapoda in time, .... 230-233 CHAPTER XXXIX. General characters of the Insecta — Metamorphoses of Insects — Sexes of Insects, . .. ./.',; 233-241 CHAPTER XL. Divisions of the Insecta — Anoplura — Mallophaga — Thysanura — Hemiptera — Orthoptera — Neuroptera — Aphaniptera — Diptera — . Lepidoptera — Hymenoptera — Strepsiptera — Coleoptera, . 241-252 CHAPTER XLI. General characters of the Mollusca — Digestive system— Circulatory system — Respiratory system — Nervous system — Reproduction — Shell, . 253-257 CHAPTER XLII. Molluscoida — Polyzoa — Distinctions between the Polyzoa and Hy- drozoa — Polypide of the Polyzoa — Anatomy of the Polyzoa — Reproduction and development — Divisions of the Polyzoa. . 258-265 CHAPTER XLIII. Tunicata — General characters — Development — Types of— Homolo- gies — Divisions, ......... 265-270 CHAPTER XLIV. Brachiopoda — General characters — Shell — Arms— Atrial system — Divisions, . . .' '• » ' ; , » , • • • • • 270-275 CHAPTER XLV. Distribution of Molluscoida in space — Distribution of Molluscoida in time, . . . .- 275-277 CHAPTER XLVI. General characters and divisions of the Mollusca Proper — Lamelli- branchiata — General characters and anatomy — Divisions — Fami- lies of the Lamellibranchiata, ...... 278-286 CHAPTER XLVII. Encephala — Gasteropoda— General characters — Development — Shell of Gasteropoda, 286-290 xiv CONTENTS. CHAPTER XLVIII. Divisions of the Gasteropoda — Prosobranchiata — Opisthobranchiata — Heteropoda — Pulmonate Gasteropoda — Families of the Gastero- poda, 290-297 CHAPTER XLIX. Pteropoda — General characters — Divisions — Families, . . 297-298 CHAPTER L. Cephalopoda — General characters — Arms — Respiratory organs — Re- productive process — Shell — Divisions, ..... 299-304 CHAPTER LI. Dibranchiate Cephalopods — General characters — Octopoda — Argon- autidae — Octopodidas — Decapoda — Teuthidae — Sepiadae — Spiru- lidae — Belemnitidse — Tetrabranchiate Cephalapods — Structure of the Pearly Nautilus — Shell of the Tetrabranchiata — Nautilidse — Ammonitidae — Families of the Cephalopoda, . . . 304-312 CHAPTER LIT. Distribution of the Mollusca Proper in time, .... 312-315 Tabular view of the chief subdivisions of the Invertebrata, . . 315-319 PART XL-VERTEBRATE ANIMALS. CHAPTER LIII. General characters of the Vert ebrata— Osseous system — Digestive sys- tem — Blood — Circulation — Respiration — Nervous system — Organs of sense — Reproduction — Divisions, . . . 323-339 CHAPTER LIV. General characters of Fishes— Integumentary system — Osseous system — Fins — Respiration — Circulation — Digestive system — Swim- bladder — Nervous system — Olfactory organs — Reproduction, 340-352 CHAPTER LV. Pharyngobranchii — Marsipobranchii, ...... 353-357 CHAPTER LVI. Teleostei — Sub-orders — Malacopteri — Anacanthini — Acanthopteri — Plectognathi — Lophobranchii, . . . . . 357-364 CONTENTS. XV CHAPTER LVII. Ganoidei — Sub-orders — Lepidoganoidei — Placoganoidei, . . 364-369 CHAPTER LVII I. Elasmobranchii and Dipnoi — Sub-orders of Elasmobranchii — Holo- cephali — Plagiostomi — Dipnoi, ...... 370-377 CHAPTER LIX. Distribution of Fishes in time, ..... 377-38° CHAPTER LX. General characters of the Amphibia, . . . 381-383 CHAPTER LXI. Orders of Amphibia — Ophiomorpha — Urodela — Anoura — Develop- ment of Frog — Families of Anoura — Labyrinthodontia — Distribu- tion of Amphibia in time, ....... 384-392 CHAPTER LXII. General characters of Reptilia — Endoskeleton — Exoskeleton — Diges- tive system — Circulatory system — Respiratory system, . . 393-397 CHAPTER LXI 1 1. Divisions of Reptilia — Chelonia — General characters of Chelonian Reptiles — Distribution of Chelonia in time — Ophidia — General characters of Snakes— Sub-orders — Distribution of Ophidia in time, 397-407 CHAPTER LXIV. Lacertilia — Families of Lacertilia — Distribution of Lacertilia in time — Crocodilia — Sub-orders of Crocodilia — Distribution of Croco- dilia in time, .... 408-415 CHAPTER LXV. Extinct orders of Reptiles — Ichthyopterygia — Sauropterygia — Ano- modontia — Pterosauria — Dinosauria, ..... 416-422 CHAPTER LXVI. General characters of the class Aves — Feathers— Vertebral column — Skull — Pectoral arch and fore-limb — Pelvic arch and hind-limb — Digestive system — Respiratory system — Circulatory system — Reproductive organs — Nervous system and organs of Sense, . 423-441 CHAPTER LXVI I. General divisions of the class Aves— Characters and families of the order Natatores — Characters and families of Grallatores, . 441-450 XVI CONTENTS. CHAPTER LXVIII. Characters of Cursores — Characters and sections of Rasores — Galli- nacei — Columbacei, ........ 451-456 CHAPTER LXIX. Characters and families of Scansores — Characters of Insessores — Coni- rostres — Dentirostres — Tenuirostres — Fissirostres, . . 457-463 CHAPTER LXX. Characters and sections of Raptores — Characters of Saururae, . 464-467 CHAPTER LXXI. Distribution of Aves in time, . 467-470 CHAPTER IXXII. General characters of the Mammalia — Skeleton — Pectoral arch and fore-limb — Pelvic arch and hind-limb — Teeth — Dental formula — Digestive system — Circulatory system — Respiratory system — Re- productive system — Mammary glands — Nervous system — Integu- mentary appendages, 471-483 CHAPTER LXXI 1 1. Classifications of the Mammalia — Synopsis of the Mammalian orders, 484-488 CHAPTER LXXIV. Characters of Monotremata — Characters and divisions of Marsu- pialia, 489-497 CHAPTER LXXV. Characters and families of Edentata, . . . . . . 498-502 CHAPTER LXXVI. Characters of Sirenia — Characters and families of Cetacea, . . 502-5 1 1 CHAPTER LXXVII. General characters of Ungulata — Perissodactyla — Artiodactyla — Ru- minantia — Structure of the stomach in Ruminants — Dentition of Ruminants — Sections of Ruminants, 511-526 CHAPTER LXXVIII. Characters of Hyracoidea — Characters of Proboscidea, . . 526-530 CHAPTER LXXIX. Characters of Carnivora — Pinnigrada — Plantigrada — Digitigrada, 530-541 CONTENTS. XVli CHAPTER LXXX. Characters of Rodentia — Families of Rodentia, .... 541-546 CHAPTER LXXXI. Characters of Cheiroptera — Sections of Cheiroptera, . . . 546-549 CHAPTER LXXXII. Characters of Insectivora — Families of Insectivora — Galeopithe- cidse, 549-551 CHAPTER LXXXI II. Characters of Quadrumana — Sections of Quadrumana — Strepsirhina — Platyrhina — Catarhina, ....... 552-558 CHAPTER LXXXIV. Characters of Bimana, ........ 558-559 CHAPTER LXXXV. Distribution of Mammalia in time — Geographical succession of or- ganic forms — Tabular view of the chief sub-divisions of the Ver- tebrata, " . ; . . 559-571 GLOSSARY, . . . 572-602 INDEX, . 603-622 LIST OF ILLUSTRATIONS. 1. Gregarina of the Earth worm, 44 2. Morphology of Rhizopoda, 3. Actinophrys sol, .... 4. Morphology of Foramini- fera, 5. Nummulites Icevigatus, 6. Acanthometrina and Poly- cystina, 7. Morphology of Radiolaria, 8. Diagram of Spongilla, 9. Morphology and reproduc- tion of Spongida, . . 10. Morphology of Infusoria, 11. Vaginicola, Stentor, and Vorticella, .... 12. Morphology of Hydrozoa, 13. Morphology of Corynida, 14. Reproductive processes of Hydrozoa, .... 15. Medusiform gonophore of Clytia, 1 6. Tubiilaria indivisa, 17. Sertularia pinnata and Campanularia neglecta, 1 8. Morphology of Oceanic Hydrozoa, .... 19. Physalia utrictdus and Vel- ella vulgaris, . . . 20. Morphology of Medusidcz, 2 1 . Group of naked-eyed Med- usa, 97 22. Lucernaria auricula, . 23. Development of Lucer- narida, 24. Generative zooid of Chry- saora, 103 25. Generative zooid of Rhi- zostoma, 26. Morphology of Grapto- lites, 27. Didymograpsus V-fractus, 28. Diagram of Actinia, 29. Actinia rosea and Arach- nactis albida, . . . VGE FIG. 30. 44 31- 47 49 32. 33- 52 34- 57 35- 36. 58 37- 59 38. 62 39- 62 40. 68 41. 70 42. 79 43- 81 44. 83 45- 46. 84 47- 85 48. 86 49. 50- 90 $«• 94 96 52. 97 53- IOO 54- 102 55- 56. I03 57- IO4 58. 107 59- 108 60. no 61. 112 PAGE Morphology of Corals, . 1 14 Sclerodermic and Sclero- basic Corals, . . . .116 Pennatula phosphor ea, . 121 Virgularia mirabilis, . .121 Pleurobrachia pileus, . .125 Morphology of Ctenophora, 126 Structure of Coral-reefs, 130 Morphology of Echinoidea, 140 Cidaris papillata, . . . 140 Larva of Echinus. Dia- gram of Echinus, . .142 Cribella oculata, . . . .145 Ophiura texturata and Ophiocoma neglecta, . . 148 Rhizocrinus Lofotensis, . 1 50 Comatula rosacea, larva and adult, 151 Echinosphcerites aurantium, 152 Thy one papillosa, . . .154 Morphology of Tceniada, . 162 Trematoda, 165 Morphology* of Turbel- laria, 1 66 Echinorhynchus gigas, . 169 Anguillula aceti and Dory- laimus stagnalis, 170 174 Hydatina senta and Meli- certa ringens, .... Diagram of an Annulose animal, 177 Syrinx midus, . . . .178 Diagrammatic section of an Annelide, . . . .179 Medicinal Leech, . . .181 Serpula contortuplicata and Spirorbis communis, . 184 Nereis, 187 Diagram of the somite of a Crustacean, . . .194 Morphology of Lobster, . 195 Larva and adult of Achthe- res percarum, . . .199 Locomotive young of Ba- lanus, 201 LIST OF ILLUSTRATIONS. XIX 62. Morphology of Cirripedia, 202 63. Fresh-water£W0;7zw/ra<:#, 205 64. Chirocephalus diaphanus, 207 65. Morphology of Trilobites, 208 66. Limulus polyphemtis, . 2IO 67. Pterygotus Anglicus, . 210 68. Caprella phasma, . . 212 69. Talitrus locusta, . . . 212 70. Wood-lice, . . . . 213 71. Homarus vulgaris, . . 215 72. Spider-crab (Maia), . 218 73. Larva (Zoea) of Crab, . 218 74. Morphology of Arachnida, 223 75. Pycnogonum littorale, Te- tranyclnts telarius and Hydrachna globulus, . 226 76. Scorpion. 228 108. 109. no. III. 112. 113- 114. «s- 116. 117. 77- Theridion riparium, . 229 78. Centipede, .... 231 118. 79. Millipede, 232 80. Diagram of Insect, . . 234 81. Organs of the Mouth in Insects, . . . . 235 119. 120. 82. Digestive system of Beetle, 237 83. Metamorphosis of the Mag- pie Moth, .... 240 121. 122. 84. Bean Aphis, .... 243 85. Cockroach (Blatta), . . 243 86. Aphis Lion, .... 244 87. Tipula oleracea, . . . 247 88. Pontia brassica, . . 248 89. Cossus ligniperda, . . 248 90. Tenthredo grossularicz, . 249 91. Stylops Spencii, . . . 251 92. Cetonia aurata and Curcu- lio sulcatus, . . . . 252 93. Diagram of a Mollusc, . 253 94. Morphology of Polyzoa, 261 95. Flustra trztncata, Valkeria, and Lophopus crystal- linus . , . 262 I23. 124. 125. 126. 127. 128. 129. 130. 1^1 96. Morphology of Tunicata, 266 97. Lingula anatina, . . 271 98. Terebratula vitrea, . . 272 99. Anatomy of Mya arenaria, 280 loo. Shells of Lamellibranch- • ittta 282 132. 133- 134. I^e 101. Odontophore of the Whelk, 287 102. Ampullaria canalictilata, 288 103. Holostomatous and Si- phonostomatous Shells, 291 104. Doris Johnstoni, . . . 292 105. Carlnaria cymbium, . . 293 1 06. Cleodora pyramidata and Cuvieria columnella, . 297 107. Sepiola Atlantic a, . . . 300 M> 136. 137- 138. 139- 140. 141. 142. 143- 144. Octopus carena, . . . 303 Paper Nautilus, . . . 305 Diagram of Belemnite, . 306 Pearly Nautilus, . . . 308 Diagram of the Siphuncle and Septa in the Shells of various Tetrabranchi- ate Cephalapods, . .310 Orthoceras explorator^ . 311 Shells of Secondary Ce- phalopods, .... 314 Transverse Sections of the body of an invertebrate and a vertebrate animal, 324 Embryology ofVertebrata, 325 Lumbar Vertebra of Whale, and diagram of thoracic vertebra, .... 328 Skeleton of the Beaver, 329 Pectoral limb of Chim- panzee, 331 Pelvic Limb of Chimpan- zee, 332 Diagram of the digestive system of a Mammal, . 333 Blood-corpuscles of Ver- tebrata, 334 Diagram of the circula- tion of a Mammal, . . 335 Scales of Fishes, . . . 340 Skeleton of the Common Perch 341 Skull of the Cod, . . .343 Os hyoides and branchial arches of the Perch, . 345 Pectoral limbs of Fishes, 346 Outline of Percagranu- lata, 348 Homocercal and hetero- cercal tails, .... 349 Diagram of the circula- tion of a Fish, . . .350 Diagram of the Lancelet, 354 Lamprey, 355 Heart of Teleostean and Ganoid Fishes, . . . 359 Gymnotus electricus, . . 360 Rhombus punctatus, . . 362 Ostracion cornutus, . . 364 Polypterus and Osteolepis, 367 Cephalaspis Lyellii, . . 369 Coccosteus and Pterichthys, 369 Head of Piked Dog-fish, 371 Carcharias and Chimera, 372 Raia marginata, , . .374 Lepidosiren annectens, . 376 XX LIST OF ILLUSTRATIONS. 145. .Spines and Teeth of Pa- . lasozoic Elasmobranchii, 379 146. ffyla leucotcznia, . . . 382 147. Proteus anguinus, . . 385 148. Axolotl, 386 149. Triton cristatus, . . .387 150. Skeleton of the Frog, . 388 151. Development of the Frog, 389 152. Footprints of a Labyrin- thodont, 391 153. Skull of a Serpent, . . 395 1 54. Diagram of the circulation in Reptiles, .... 396 155. Skeleton of Tortoise, . 399 156. Hawk's-bill Turtle, . . 400 157. Eye of Serpent and Head of Viper, 403 158. Head of Ringed Snake, of Viper, and ofBlindworm,4O7 159. Iguana, 408 160. Blind-worm, .... 410 161. Head of Chameleon, . 412 162. Skull of Crocodilus bi- porcatus, 414 163. Ichthyosaiirus communis, 417 164. Plesiosaunts dolichodeirus, 418 165. Pterodactylus brevirostris, 419 1 66. Quill-feather, .... 425 167. Skull of Spur - winged Goose, 428 1 68. Pectoral arch and fore- limb of Penguin, . . 429 169. Fore-limb of Jer-falcon, . 430 170. Hind-limb of Loon, . . 432 171. Digestive System of the Common Fowl, . . . 434 1 72. Lung of Goose, . . . 436 173. Foot of Cormorant and Beak of Goose, . . . 444 174. Leg of Curlew, Head of Snipe, and Beak of Avocet, 448 175. Foot of Ostrich, and Breast-bone of Emeu, . 45 1 176. Foot of Fowl, and Head of Guinea-fowl, . . . 454 177. Foot of Woodpecker, and Head of Love-bird, . . 458 178. Feet and Heads of Inses- sores, 459 i?9. Head of Bullfinch, . .461 1 80. Foot of Peregrine Falcon, and Head of Buzzard, . 464 181. 182. 183. 184. 185. 1 86. 187. 188. 190. 191. 192. 193- 194. 196. 197. 198. 199. 200. 201. 2O2. 203. 204. 205. 206. 2O7. 208. 209. 210. 211. 212. 2I4. 215- 216. 217. 218. 219. 220. Foot of Tawny Owl, and Head of White Owl, . 465 Head of Vulture, . . . 466 Archceopteryx macrura, . 467 Fore-limbs of Horse and Deer, 476 Teeth of Chimpanzee, . 480 Ornithorhynchus para - doxus, 490 Pelvis of Kangaroo, . . 492 Dentition of Thylacimis and Hypsiprymnus, 494 497 499 500 5°3 505 Myrmecobius fasciatus, . Hand of three-toed Sloth, Chlamyphorus tmncatus, Dugong, Skull of Right Whale, . Diagram of Baleen-plates of a Whale, . . . PJiyseter macrocephalus, Delphimts delphis, Feet of Ungulata, . . Head of Two - horned Rhinoceros, . . . .514 Stomach of a Sheep, . . 519 Skull of hornless Sheep, Skull of the Indian Ele- phdnt, Skull of Deinotheritim, Feet of Carnivora, Phoca grcenlandica, . Skull of the Walrus, Skull of Jackal, . . Skull of Lion, . . . Skull of Beaver, . . Skeleton of Fox-bat, . . Head of Vampire-bat and Fox-bat, Skull of Hedgehog, . . Skulls of Orang and Eu- ropean adult, .... Jaw of Dromatherium, . Jaws of Phascolotheriumt Triconodon, Amphithe- rium, and Plagiaulax, . 561 Skull of Diprotodon, . .563 Skeleton of Megatherium, 563 Glyptodon clavipes, . .564 Skeleton viMegaceros Hi- bernicus, 566 Skeleton of Mastodon, . 567 Skeleton of Mammoth, . 567 507 509 5io 512 520 528 530 53i 532 533 539 540 542 547 548 550 557 PART I. INVERTEBRATE ANIMALS MANUAL OF ZOOLOGY. GENERAL INTRODUCTION. i. DEFINITION OF BIOLOGY AND ZOOLOGY. NATURAL HISTORY, strictly speaking, and as the term itself implies, should be employed to designate the study of all natural objects indiscriminately, whether these are organic or inorganic, endowed with life,- or exhibiting none of those incessant vicissitudes which collectively constitute vitality. So enormous, however, have been the conquests of science within the last century, that Natural History, using the term in its old sense, has of necessity been divided into several more or less nearly related branches. In the first place, the study of natural objects admits of an obvious separation into two primary sections, of which the first deals with the phenomena presented by the inor- ganic world, whilst the second is occupied with the investi- gation of the nature and relations of all bodies which exhibit life. The former department concerns the geologist and mi- neralogist, and secondarily the naturalist proper as well ; the latter department, treating as it does of living beings, is pro- perly designated by the term Biology (from /3/oc, life, and Xo'yos, a discourse). Biology, in turn, may be split up into the sciences of Botany and Zoology, the former dealing with plants, the latter with animals ; and it is really Zoology alone which is nowadays understood by the term Natural History. In determining, therefore, the limits and scope of Biology, we are brought at the very threshold of our inquiry to the question, What are the differences between dead and living bodies ; or rather, in the first place, what are the characteris- tics of an organised as compared with an unorganised body ? * * The differences between dead or inorganic bodies on the one hand and living or organic bodies on the other, may be taken for all practical purposes as the same as those between unorganised and organised bodies. It is quite true that certain living beings (Foraminifera) cannot be said to VOL. I. A &*: -*\' V * : ;M'A^UAL OF ZOOLOGY. 2. DIFFERENCES BETWEEN ORGANISED AND UNORGANISED BODIES. In determining this somewhat difficult point, it will be best to examine the differences between organised and unorgan- ised bodies seriatim, and to compare them together system- atically under the following heads : — a. Chemical Composition. — Unorganised bodies are composed of many elements, which may be either simple or combined ; but the combinations are mostly limited to a small number of elements (forming binary and ternary compounds), and these are united in low combining proportions. Thus, carbonate of lime, or common limestone, is an excellent example of an in- organic body,* being a ternary compound composed of one atom of the metal calcium, three of oxygen, and one of carbon. Organised bodies, on the other hand, are composed of few chemical elements, and these are almost always combined. Furthermore, the combinations are always complex (ternary and quaternary compounds), and the elements enter into union in high combining proportions. Finally, the combinations are invariably characterised by the presence of water, and are prone to spontaneous decomposition. Thus, the great organic com- pound, albumen, is composed of 144 atoms of carbon, no of hydrogen, 18 of nitrogen, 2 atoms of sulphur, and 42 of oxygen. Iron, however, exists in the blood, very probably in its elemental condition ; and copper has been detected in the liver of certain Mammalia, and largely in the red colouring- matter of the feathers of certain birds. b. Arrangement of Parts. — Unorganised bodies are composed of an aggregation of homogeneous parts (when unmixed) which bear no definite and fixed relations to one another. Organised bodies are composed of heterogeneous parts, the relations of which amongst themselves are more or less definite. c. Form. — Unorganised bodies are either of no definite shape — when they are said to be " amorphous " — or they are crystal- line, in which case they are almost invariably bounded by plane surfaces and straight lines. Organised bodies are always more or less definite in shape, presenting convex and concave surfaces, and being bounded by curved lines. be "organised " in the proper sense of the term ; still organisation is in such a vast proportion of cases the concomitant of vitality, that the pur- pose here in view will be fully served by assuming that all living bodies are organised and all dead bodies are unorganised. * In another sense limestone may be said to be organic — namely, when it has been produced by the operations of living beings ; but this does not affect the above definition. NATURE OF LIFE. 3 d. Mode of Increase. — When unorganised bodies increase in size, as crystals do, the increase is produced simply by what is called "accretion;" that is to say, by the addition of fresh particles from the outside. Organised bodies increase by what is often called the " in- tussusception " of matter ; in other words, by the reception of matter into their interior and its assimilation there. To this process alone can the term " growth " be properly applied. e. Cyclical Change. — Unorganised bodies exhibit no actions that are not purely physical or chemical, and they show no tendency to periodical vicissitudes. Organised bodies are pre- eminently distinguished by the tendency which they show to pass through spontaneous and cyclical changes. To sum up, all bodies which are composed of an aggrega- tion of diverse but definitely related parts, which have a defi- nite shape, bounded by curved lines and presenting concave and convex surfaces, which increase in size by the intussus- ception of foreign particles, and which pass through certain cyclical changes, are organised; and it is with the study of bodies such as these that Biology is concerned. In the foregoing it has been assumed, for the sake of simpli- city, that all living bodies exhibit organisation. It is to be remembered, however, that there are living bodies (e. g. Fora- minifera) to which the term of " organised," as above defined, cannot be applied. Such bodies are living, but they are not organised. In these cases the distinction from dead matter de- pends wholly upon the mode of growth, and upon the presence of vital activity as shown by the occurrence of various periodic changes. 3. NATURE OF LIFE. We have next to determine — and the question is one of great difficulty — what connection exists between organisation and life. Is organisation, as we have defined it, essential to the manifestation of life, or can vital phenomena be exhibited by any body which is devoid of an organised structure ? In other words, is life the cause of organisation, or the result of t ? And first, what do we mean by life ? Life has been variously defined by different writers. Bichat defines it as "the sum total of the functions which resist death; " Treviranus, as "the constant uniformity of phenomena with diversity of external influences ; " Duges, as " the special acti- vity of organised bodies;" and Beclard, as "organisation in action." All these definitions, however, are more or less objec- tionable, since the assumption underlies them all that life is 4 MANUAL OF ZOOLOGY. inseparably connected with organisation. In point of fact, no rigid definition of life appears to be at present possible, and it is best to regard it as being simply a tendency exhibited by certain forms of matter, under certain conditions, to pass through a series of changes in a more or less definite and determinate sequence. As regards the connection between life and organisation, it appears that whilst all organised bodies exhibit this ten- dency to change, and are therefore alive, all living beings are not necessarily organised. Many of the lowest forms of life (such as the Foraminifera amongst the Protozoa) fail to fulfil one of the most essential conditions of organisation, being de- void of definite parts or organs of any kind. Nevertheless, they are capable of manifesting all the essential phenomena of life ; they are produced from bodies like themselves ; they eat, digest, and move, and exhibit distinct sensibility to many ex- ternal impressions. Furthermore, many of these little masses of structureless jelly possess the power of manufacturing for themselves, of lime, or of the still more intractable flint, external shells of surpassing beauty and mathematical regu- larity. In the face of these facts we are therefore compelled to come to the conclusion that life is truly the cause and not the consequence of organisation ; or, in other words, that or- ganisation is not an intrinsic and indispensable condition of vital phenomena. Such an intrinsic and indispensable condition is, however, according to Huxley, to be found in the presence of a uniform " physical basis," to which he has applied the name of "pro- toplasm," (the "bioplasm" of Dr Beale). Without such a material substratum, or medium upon which to work, no one vital phenomenon can be exhibited. The necessary forces may be there, but in the absence of this necessary vehicle there can be no outward and visible manifestation of their existence. Life, therefore, as we know it, and as far as we know it, may be said to be inseparably connected with protoplasm. As regards its nature, protoplasm, though capable of form- ing the most complex structures, does not necessarily exhibit anything which can be looked upon as organisation, or dif- ferentiation into distinct parts ; and its chemical composi- tion is the only constant which can be certainly stated. It consists, namely, in all its forms, of the four elements, carbon, hydrogen, oxygen, and nitrogen, united into a proximate compound to which Mulder applied the name of " proteine," and which is very nearly identical with albumen or white-of- NATURE OF LIFE. 5 egg. It further appears probable that all forms of protoplasm can be made to contract by means of electricity, and " are liable to undergo that peculiar coagulation at a temperature of 4o°-5o° centigrade, which has been called ' heat-stiffening ' " (Huxley). If we admit, then, with Huxley — and the admission re- quires some qualifications — that " protoplasm, simple or nucleated, is the formal basis of all life," there, nevertheless, remain certain conditions equally indispensable to the external manifestation of vital phenomena; though life itself, or the power of exhibiting vital phenomena, may be preserved for a longer or shorter period, even though these conditions be ab- sent. These extrinsic conditions of vitality are firstly, a cer- tain temperature varying from near the freezing-point to 120° or 130°; secondly, the presence of water, which enters largely into the composition of all living tissues ; thirdly, the presence of oxygen in a free state, — this, like water, appearing to be a sine qua non of life, though certain fungi are stated to offer an exception to this statement* The non-fulfilment of any of these conditions for any length of time, as a rule, causes death, or the cessation of vitality; but, as before remarked, life may sometimes remain in a dormant or " potential " condition for an apparently indefinite length of time. An excellent illustration of this is afforded by the great tenacity of life, even under unfavourable conditions, exhibited by the ova of some animals and the seeds of many plants ; but a more striking example is to be found in the Rotifera, or Wheel- animalcules. These are minute, mostly microscopic creatures, which inhabit almost all our ponds and streams. Diminutive as they are, they are nevertheless, comparatively speaking, of a very high grade of organisation. They possess a mouth, masticatory organs, a stomach and alimentary canal, a dis- tinct and well-developed nervous system, a differentiated re- productive apparatus, and even organs of vision. Repeated experiments, however, have shown the remarkable fact, that, with their aquatic habits and complex organisation, the Roti- fers are capable of submitting to an apparently indefinite de- privation of the necessary conditions of their existence, with- out thereby losing their vitality. They may be dried and reduced to dust, and may be kept in this state for a period of many years ; nevertheless, the addition of a little water will, at any time, restore them to their pristine vigour and activity. It follows, therefore, that an organism may be deprived of all * Recent experiments, as yet unconfirmed, would go to prove that these conditions of vitality are not of such essential importance. 0 MANUAL OF ZOOLOGY. power of manifesting any of the phenomena which constitute what we call life, without losing its hold upon the vital forces which belong to it. If, in conclusion, it be asked whether the term " vital force " is any longer permissible in the mouth of a scientific man, the question must, I think, be answered in the affirmative. Formerly, no doubt, the progress of science was retarded and its growth checked by a too exclusive reference of natural phenomena to a so-called vital force. Equally unquestionable is the fact that the development of Biological science has pro- gressed contemporaneously with the successive victories gained by the physicists over the vitalists. Still, no physicist has hitherto succeeded in explaining any fundamental vital phe- nomenon upon purely physical and chemical principles. The simplest vital phenomenon has in it something over and above the merely chemical and physical forces which we can demon- strate in the laboratory. It is easy, for example, to say that the action of the gastric juice is a chemical one, and doubt- less the discovery of this fact was a great step in physiological science. Nevertheless, in spite of the most searching inves- tigations, it is certain that digestion presents phenomena which are as yet inexplicable upon any chemical theory. This is exemplified in its most striking form, when we look at a simple organism like the Amoeba. This animalcule, which is structurally little more than a mobile lump of jelly, digests as perfectly — as far as the result to itself is concerned — as does the most highly organised animal with the most complex digestive apparatus. It takes food into its interior, it digests it without the presence of a single organ for the purpose ; and still more, it possesses that inexplicable selective power by which it assimilates out of its food such constituents as it needs, whilst it rejects the remainder. In the present state of our knowledge^ therefore, we must conclude that even in the process of digestion as exhibited in the Amoeba there is some- thing that is not merely physical or chemical. Similarly, any organism when just dead consists of the same protoplasm as before, in the same forms, and with the same arrangement ; but it has most unquestionably lost a something by which all its properties and actions were modified, and some of them were produced. What that something is, we do not know, and perhaps never shall know; and it is possible, though highly improbable, that future discoveries may demonstrate that it is merely a subtle modification of some physical force. In the meanwhile, as all vital actions exhibit this mysterious something, it would appear unphilosophical to ignore its exist- DIFFERENCES. BETWEEN ANIMALS AND PLANTS. 7 ence altogether, and the term " vital force " may therefore be retained with advantage. In using this term, however, it must not be forgotten that we are simply employing a con- venient expression for an unknown quantity, for that residual portion of every vital action which cannot at present be re- ferred to the operation of any known physical force. 4. DIFFERENCES BETWEEN ANIMALS AND PLANTS. We have now arrived at some definite notion of the essen- tial characters of living beings in general, and we have next to consider what are the characteristics of the two great divisions of the organic world. What are the characters which induce us to place any given organism in either the vegetable or the animal kingdom ? What, in fact, are the differences between animals and plants ? It is generally admitted that all bodies which exhibit vital phenomena are capable of being referred to one of the two great kingdoms of organic nature. At the same time it is often extremely difficult in individual cases to come to any decision as to the kingdom to which a given organism should be referred, and in many cases the determination is purely arbitrary. So strongly, in fact, has this difficulty been felt, that some observers have established an intermediate kingdom, a sort of no-man's-land, for the reception of those debatable organisms which cannot be definitely and positively classed either amongst vegetables or amongst animals. Thus, Dr Ernst Haeckel has proposed to form an intermediate kingdom, which he calls the Regnum Protisticum, for the reception of all doubtful organisms. Even such a cautious observer as Dr Rolleston, whilst questioning the propriety of this step, is forced to conclude that "there are organisms which at one period of their life exhibit an aggregate of phenomena such as to justify us in speaking of them as animals, whilst at another they appear to be as distinctly vegetable." In the case of the higher animals and plants there is no- difficulty; the former being at once distinguished by the possession of a nervous system, of motor power which can be voluntarily exercised, and of an internal cavity fitted for the reception and digestion of solid food. The higher plants, on the other hand, possess no nervous system or organs of sense, are incapable of independent locomotion, and are not provided with an internal digestive cavity, their food being wholly fluid or gaseous. These distinctions, however, do not hold good as regards the lower and less highly organised members of the 8 MANUAL OF ZOOLOGY. two kingdoms, many animals having no nervous system or in- ternal digestive cavity, whilst many plants possess the power of locomotion ; so that we are compelled to institute a closer comparison in the case of these lower forms of life. a. Form. — As regards external configuration, of all charac- ters the most obvious, it must be admitted that no absolute distinction can be laid down between plants and animals. Many of our ordinary zoophytes, such as the Hydroid Polypes, the sea-shrubs and corals — as, indeed, the name zoophyte implies — are so similar in external appearance to plants that they were long described as such. Amongst the Molluscoida, the common sea-mat (Flustra) is invariably regarded by sea- side visitors as a seaweed. Many of the Protozoa are equally like some of the lower plants (Protophyta) ; and even at the present day there are not wanting those who look upon the sponges as belonging to the vegetable kingdom. On the other hand, the embryonic forms, or " zoospores," of certain un- doubted plants (such as the Protococcus nivalis, Vaucheria, &c.) are provided with ciliated processes With which they swim about, thus coming so closely to resemble some of the Infusorian animalcules as to have been referred to that divi- sion of the Protozoa. b. Internal Structure. — Here, again, no line of demarcation can be drawn between the animal and vegetable kingdoms. In this respect all plants and animals are fundamentally similar, being alike composed of molecular, cellular, and fib- rous tissues. c. Chemical Composition. — Plants, speaking generally, exhibit a preponderance of ternary compounds of carbon, hydrogen, and oxygen — such as starch, cellulose, and sugar — whilst nitrogenised compounds enter more largely into the compo- sition of animals. Still both kingdoms contain identical or representative compounds, though there may be a difference in the proportion of these to one another. Moreover, the most characteristic of all vegetable compounds, viz. cellulose, has been detected in the outer covering of the sea -squirts, or Ascidian Molluscs; and the so-called "glycogen," which is secreted by the liver of the Mammalia, is closely allied to, if not absolutely identical with, the hydrated starch of plants. As a general rule, however, it may be stated that the presence in any organism of an external envelope of cellulose raises a strong presumption of its vegetable nature. In the face, however, of the facts above stated, the presence of cellulose cannot be looked upon as absolutely conclusive. Another highly charac- teristic vegetable compound is chlorophyll, the green colouring- DIFFERENCES BETWEEN ANIMALS AND PLANTS. 9 matter of plants. Any organism which exhibits chlorophyll in any quantity, as a proper element of its tissues, is most probably vegetable. As in the case of cellulose, however, the presence of chlorophyll cannot be looked upon as a certain test, since it occurs normally in certain undoubted animals (e.g., Stentor, amongst the Infusoria, and the Hydra viridis, or the green Fresh-water Polype, amongst the Ccclenteratd). d. Motor Power. — This, though broadly distinctive of ani- mals, can by no means be said to be characteristic of them. Thus, many animals in their mature condition are permanently fixed, or attached to some foreign object ; and the embryos of many plants, together with not a few adult forms, are endowed with locomotive power by means of those vibratile, hair-like processes which are called "cilia," and are so characteristic of many of the lower forms of animal life. Not only is this the case, but large numbers of the lower plants, such as the Diatoms and Desmids, exhibit throughout life an amount and kind of locomotive power which does not admit of being rigidly separated from the movements executed by animals, though the closest researches have hitherto failed to show the mechanism whereby these movements are brought about. e. Nature of the Food. — Whilst all the preceding points have failed to yield a means of invariably separating animals from plants, a distinction which holds good almost without exception is to be found in the nature of the food taken respectively by each, and in the results of the conversion of the same. The unsatisfactory feature, however, in this dis- tinction, is this, that even if it could be shown to be, theoreti- cally, invariably true, it would nevertheless be practically impossible to apply it to the greater number of those minute organisms concerning which alone there can be any dispute. As a broad rule, all plants are endowed with the power of converting inorganic into organic matter. The food of plants consists of the inorganic compounds, carbonic acid, ammonia, and water, along with small quantities of certain mineral salts. From these, and from, these only, plants are capable of elaborating the proteinaceous matter or protoplasm which constitutes the physical basis of life. Plants, therefore, take as food very simple bodies, and manufacture them into much more complex substances. To this general statement, however, an exception must seemingly be made in favour of certain fungi, which require organised compounds for their nourishment. On the other hand, no known animal possesses the power of converting inorganic compounds into organised matter, but all, mediately or immediately, are dependent in this respect 10 MANUAL OF ZOOLOGY. upon plants. All animals, as far as is certainly known, require ready-made proteinaceous matter for the maintenance of exist- ence, and this they can only obtain in the first instance from plants. Animals, in fact, differ from plants in requiring as food complex organic bodies which they ultimately reduce to very much simpler inorganic bodies. Plants, therefore, are the great manufacturers in nature, animals are the great consumers. Just, however, as this law does not invariably hold good for plants, certan fungi being in this respect animals, so it is not impossible that a limited exception to the universality of the law will be found in the case of animals also. Thus, in some recent investigations into the fauna of the sea at great depths, a singular organism, of an extremely low type, but occupying large areas of the sea-bottom, has been discovered, to which Professor Huxley has given the name of Bathybius. As vegetable life is extremely scanty, or is altogether wanting, in these abysses of the ocean, it has been conjectured that this organism is possibly endowed with the power — otherwise exclusively found in plants — of elaborating organic compounds out of inorganic materials, and in this way supplying food for the higher animals which surround it. The water of the ocean, however, at these enormous depths, is richly charged with organic matter in solution, and this conjecture is thereby rendered doubtful. Be this as it may, there remain to be noticed two distinc- tions, broadly though not universally applicable, which are due to the nature of the food required respectively by animals and plants. In the first place, the food of all plants consists partly of gaseous matter and partly of matter held in solution. They require, therefore, no special aperture for its admission, and no internal cavity for its reception. The food of almost all animals consists of solid particles, and they are, therefore, usually provided with a mouth and a distinct digestive cavity. Some animals, however, such as the tape-worm and the Gre- garinae, live entirely by the imbibition of organic fluids through the general surface of the body, and many have neither a dis- tinct mouth nor stomach. Secondly, plants decompose carbonic acid, retaining the carbon and setting free the oxygen, certain fungi forming an exception to this law. The reaction of plants upon the atmo- sphere is, - therefore, characterised by the production of free oxygen. Animals, on the other hand, absorb oxygen and emit carbonic acid, so that their reaction upon the atmosphere is the reverse of that of plants, and is characterised by the pro- duction of carbonic acid. MORPHOLOGY AND PHYSIOLOGY. II Finally, it is worthy of notice that it is in their lower and not in their higher developments that the two kingdoms of organic nature approach one another. No difficulty is ex- perienced in separating the higher animals from the higher plants, and for these universal laws can be laid down to which there is no exception. It might, not unnaturally, have been thought that the lowest classes of animals would exhibit most affinity to the highest plants, and that thus a gradual passage between the two kingdoms would be established. This is not the case, however. The lower animals are not allied to the higher plants, but to the lower ; and it is in the very lowest mem- bers of the vegetable kingdom, or in the embryonic and imma- ture forms of plants little higher in jthe scale, that we find such a decided animal gift as the power of independent locomotion. It is also in the less highly organised and less specialised forms of plants that we find the only departures from the great laws of vegetable life, the deviation being in the direction of the laws of animal life. 5. MORPHOLOGY AND PHYSIOLOGY. The next point which demands notice relates to the nature of the differences between one animal and another, and the question is one of the highest importance. Every animal — as every plant — may be regarded from two totally distinct, and, indeed, often apparently opposite, points of view. From the first point of view we have to look simply to the laws, form, and arrangement of the structures of the organism ; in short, to its external shape and internal structure. This con- stitutes the science of morphology ({tootp^form, and Xo'yoj, dis- course}. From the second, we have to study the vital actions performed by living beings and \hz functions discharged by the different parts of the organism. This constitutes the science of physiology. A third department of zoology is concerned with the relations of the organism to the external conditions under which it is placed, constituting a division of the science to which the term " distribution " is applied. Morphology, again, not only treats of the structure of living beings in their fully developed condition (anatomy), but is also concerned with the changes through which every living being has to pass before it assumes its mature or adult charac- ters (embryology or development). The term " histology " is further employed to designate that branch of morphology which is specially occupied with the investigation of minute or micro- scopical tissues. 12 MANUAL OF ZOOLOGY. Physiology treats of all the functions exercised by living bodies, or by the various definite parts, or organs, of which most animals are composed. All these functions come under three heads : — i. Functions of Nutrition, divisible into func- tions of absorption and metamorphosis, comprising those func- tions which are necessary for the growth and maintenance of the organism. 2. Functions of Reproduction, whereby the per- petuation of the species is secured. 3. Functions of Correlation, comprising all those functions (such as sensation and voluntary motion) by which the external world is brought into relation with the organism, and the organism in turn reacts upon the external world. Of these three, the functions of nutrition and reproduction are often collectively called the functions of organic or vege- tative life, as being common to animals and plants ; while the functions of correlation are called the animal functions, as being more especially characteristic of, though not peculiar to, animals. 6. DIFFERENCES BETWEEN DIFFERENT ANIMALS. All the innumerable differences which subsist between dif- ferent animals may be classed under two heads, corresponding to the two aspects of every living being, morphological and physiological. One animal differs from another either morpho- logically, in the fundamental points of its structure ; or physio- logically, in the manner in which the vital functions of the organism are discharged. These constitute the only modes in which any one animal can differ from any other ; and they may be considered respectively under the heads of Specialisation of Function and Morphological type. a. Specialisation of Function. — All animals alike, whatever their structure may be, perform the three great physiological functions ; that is to say, they all nourish themselves, repro- duce their like, and have certain relations with the external world. They differ from one another physiologically in the manner in which these functions are performed. Indeed, it is only in the functions of correlation that it is possible that there should be any difference in the amount or perfection of the function performed by the organism, since nutrition and repro- duction, as far as their results are concerned, are essentially the same in all animals. In the manner, however, in which the same results are brought about, great differences are observable in different animals. The nutrition of such a simple organism as the Amoeba is, indeed, performed perfectly, as far as the result to the animal itself is concerned — as perfectly as in the SPECIALISATION OF FUNCTION. 13 case of the highest animal — but it is performed with the simplest possible apparatus. It may, in fact, be said to be performed without any special apparatus, since any part of the surface of the body may be extemporised into a mouth, and there is no differentiated alimentary cavity. And not only is the nutritive apparatus of the simplest character, but the function itself is equally simple, and is entirely divested of those complexities and separations into secondary functions which characterise the process in the higher animals. It is the same, too, with the functions of reproduction and correlation ; but this point will be more clearly brought out if we examine the method in which one of the three primary functions is performed in two or three examples. Nutrition, as the simplest of the functions, will best answer the purpose. In the simpler Protozoa, such as the Amoeba, the process of nutrition consists essentially in the reception of food, its di- gestion within the body, the excretion of effete or indigestible matter, and the distribution of the nutritive fluid through the body. The first three portions of this process are effected with- out any special organs for the purpose, and for the last there is simply a rudimentary contractile cavity. Respiration, if it can be said to exist at all as a distinct function, is simply effected by the general surface of the body. In a Ccelenterate animal, such as a sea-anemone, the func- tion of nutrition has not advanced much in complexity, but the means for its performance are somewhat more specialised. Permanent organs of prehension (tentacles) are present, there is a distinct mouth, and there is a persistent internal cavity for the reception of the food ; but this is not shut off from the general cavity of the body, and there are no distinct circulatory or respiratory organs. In a Mollusc, such as the oyster, nutrition is a much more complicated process. There is a distinct mouth, and an ali- mentary canal which is shut off from the general cavity of the body, and is provided with a separate aperture for the excre- tion of effete and indigestible matters. Digestion is performed by a distinct stomach with accessory glands ; a special contrac- tile cavity, or heart, is provided for the propulsion of the nutri- tive products of digestion through all parts of the organism, and the function of respiration is performed by complex organs specially adapted for the purpose. It is not necessary here to follow out this comparison further. In still higher animals the function of nutrition becomes still further broken up into secondary functions, for the due performance of which special organs are provided, the 14 MANUAL OF ZOOLOGY. complexity of the organism thus necessarily increasing part passu with the complexity of the function. This gradual sub- division and elaboration is carried out equally with the other two physiological functions, viz. reproduction and correlation, and it constitutes what is technically called the "specialisa- tion of functions," though it has been more happily termed by Milne-Edwards " the principle of the physiological division of labour." It is needless, however, to remark that in the higher animals it is the functions of correlation which become most highly specialised — disproportionately so, indeed, when com- pared with the development of the nutritive and reproductive functions. b. Morphological Type. — The first point in which one animal may differ from another is the degree to which the principle of the physiological division of labour is carried. The second point in which one animal may differ from another is in its "morphological type;" that is to say, in the funda- mental plan upon which it is constructed. By one not specially acquainted with the subject it might be readily imagined that each species or kind of animal was constructed upon a plan peculiar to itself and not shared by any other. This, how- ever, is far from being the case ; and it is now universally recognised that all the varied species of animals — however great the apparent amount of diversity amongst them — may be arranged under no more than half-a-dozen primary morpho- logical types or plans of structure. Upon one or other of these five or six plans every known animal, whether living or extinct, is constructed. It follows from the limited number of primitive types or patterns, that great numbers of animals must agree with one another in their morphological type. It follows also that all so agreeing can differ from one another only in the sole remaining element of the question — namely, by the amount of specialisation of function which they exhibit. Every animal, therefore, as Professor Huxley has well expressed it, is the resultant of two tendencies, the one morphological, the other physiological. The six types or plans of structure, upon one or other of which all known animals have been constructed, are techni- cally called "sub-kingdoms," and are known by the names Protozoa, Ccelenterata, Annuloida, Annulosa, Mollusca, and Vertebrata. We have, then, to remember that every member of each of these primary divisions of the animal kingdom agrees with every other member of the same division in being formed upon a certain definite plan or type of structure, and differs from every other simply in the grade of its organisation, MORPHOLOGICAL TYPE. 15 or, in other words, in the degree to which it exhibits specialisa- tion of function. VON BAER'S LAW OF DEVELOPMENT. — As the study of living beings in their adult condition shows us that the differences between those which are constructed upon the same morpho- logical type depend upon the degree to which specialisation of function is carried, so the study of development teaches us that the changes undergone by any animal in passing from the embryonic to the mature condition are due to the same cause. All the members of any given sub-kingdom, when examined in their earliest embryonic condition, are found to present the same fundamental characters. As development proceeds, however, they diverge from one another with greater or less rapidity, until the adults ultimately become more or less different, the range of possible modification being ap- parently almost illimitable. The differences are due to the different degrees of specialisation of function necessary to perfect the adult, and, therefore, as Von Baer put it, the pro- gress of development is from the general to the special. It is upon a misconception of the true import of this law that the theory arose, that every animal in its development passed through a series of stages in which it resembles, in turn, the different inferior members of the animal scale. With regard to man, standing at the top of the whole animal kingdom, this theory has been expressed as follows: — "Human organogenesis is a transitory comparative anatomy, as, in its turn, comparative anatomy is a fixed and permanent state of the organogenesis of man" (Serres). In other words, the embryo of a Vertebrate animal was believed to pass through a series of changes corresponding respectively to the permanent types of the lower sub-kingdoms — namely, the Protozoa, Cce- lenterata, Annuloida, Annulosa, and Mollusca — before finally assuming the true vertebrate characters. Such, however, is not truly the case. The ovum of every animal is from the first impressed with the power of developing in one direction only, and very early exhibits the fundamental characters proper to its sub-kingdom, never presenting the structural peculiarities belonging to any other morphological type. Never- theless, the differences which subsist between the members of each sub-kingdom in their adult condition are truly referable to the degree to which development proceeds, the place of each individual in his own sub-kingdom being regulated by the stage at which development .is arrested. Thus, many cases are known in which the younger stages of a given animal represent the permanent adult condition of an animal some- 1 6 MANUAL OF ZOOLOGY. what lower in the scale. To give a single example, the young Gasteropod (amongst the Mollusca) transiently presents all the essential characters which permanently distinguish the adult Pteropod. The development of the Gasteropod, however, pro- ceeds beyond this point, and the adult is much more highly specialised than is the adult Pteropod. 7. HOMOLOGY, ANALOGY, AND HOMOMORPHISM. When organs in different animals agree with one another in fundamental structure, they are said to be " homologous ; " when they perform the same functions they are said to be " analogous." Thus the wing of a bird and the arm of a man are constructed upon the same fundamental plan, and they are, therefore, homologous organs. They are not analogous, however, since they do not perform the same function, the one being adapted for aerial locomotion, the other being an organ of prehension. On the other hand, the wings of a bird and the wings of an insect both serve for flight, and they are, therefore, analogous, since they perform the same function. They are not homologous, however, as they are constructed upon wholly dissimilar plans. There are numerous cases, however, in which organs correspond with one another both structurally and functionally, in which case they are both homologous and analogous. A form of homology is often seen in a single animal in which there exists a succession of parts which are fundamentally identical in structure, but are variously modified to fulfil dif- ferent functions. Thus a Crustacean — such as the lobster — may be looked upon as being composed of a succession of rings, each of which bears a pair of appendages, these appen- dages being constructed upon the same type, and being, there- fore, homologous. They are, however, variously modified in different regions of the body to enable them to fulfil special functions, some being adapted for swimming, others for walk- ing, others for prehension, others for mastication, and so on. This succession of fundamentally similar parts in the same animal constitutes what is known as serial homology. When, however, the successive parts are similar to one another, both in structure and in function, the case becomes rather one of what is called " vegetative" or "irrelative repetition." An ex- cellent instance of this is seen in the common Millipede (lulus). Homomorphism. — Many examples occur, both among animals and among plants, in which families widely removed from one another as to their fundamental structure, nevertheless pre- CORRELATION OF GROWTH. I/ sent a singular, and sometimes extremely close, resemblance in their external characters. Thus the composite Hydroid Polypes and the Polyzoa are singularly like one another ; so much so, that they have often been classed together, whereas, in reality, they belong to different sub-kingdoms. Many other cases of this " mimetic " resemblance of different animals might be adduced, and in many cases these "repre- sentative forms " appear to be able to fill each other's places in the general economy of nature. This is so far true, at any rate, that " homomorphous " forms are generally found in dif- ferent parts of the earth's surface. Thus, the place of the Cacti of South America is taken by the Euphorbias of Africa ; or, to take a zoological illustration, many of the different orders of Mammalia are represented in the single order Marsupialia in Australia, in which country this order has almost alone to discharge the functions elsewhere performed by several orders. Many mimetic forms, however, live peacefully side by side, and it is difficult to say whether in this case the resemblance between them is for the advantage or for the disadvantage of either. 8. CORRELATION OF GROWTH. This term is employed by zoologists to express the empi- rical law, that certain structures, not necessarily or usually connected together by any visible link, invariably occur in association with one another, and never occur apart, — so far, at any rate, as human observation goes. Thus, all animals which possess two condyles on the occi- pital bone, and possess non-nucleated red blood-corpuscles, suckle their young. Why an animal with only one condyle on its occipital bone should not suckle its young we do not know, and perhaps we shall at some future time find mam- mary glands associated with a single occipital condyle. Again, the feet are cleft in all animals which ruminate, but not in any other. In other cases the correlation is even more appa- rently lawless, and is even amusing. Thus all, or almost all, cats which are entirely white and have blue eyes, are at the same time deaf. With regard to these and similar gene- ralisations we must, however, bear in mind the following three points : — i. The various parts of the organisation of any animal are so closely interconnected, and so mutually dependent upon one another, both in their growth and development, that the characters of each must be in some relation to the characters of all the rest, whether this be obviously the case or not. VOL. I. B 1 8 MANUAL OF ZOOLOGY. 2. It is rarely possible to assign any reason for correlations of structure, though they are certainly in no case accidental. 3. The law is a purely empirical one, and expresses nothing more than the result of experience ; so that structures which we now only know as occurring in association, may ultimately be found dissociated, and conjoined with other structures of a different character. 9. CLASSIFICATION. Classification is the arrangement of a number of diverse objects into larger or smaller groups, according as they ex- hibit more or less likeness to one another. The excellence of any given classification will depend upon the nature of the points which are taken as determining the resemblance. Sys- tems of classification, in which the groups are founded upon mere external and superficial points of similarity, though often useful in the earlier stages of science, are always found in the long-run to be inaccurate. It is needless, in fact, to point out that many living beings, the structure of which is fundamentally different, may, nevertheless, present such an amount of adaptive external resemblance to one another, that they would be grouped together in any " artificial" classifica- tion. Thus, to take a single example, the whale, by its ex- ternal characters, would certainly be grouped amongst the fishes, though widely removed from them in all the essential points of its structure. "Natural" systems of classification, on the other hand, endeavour to arrange animals into divi- sions founded upon a due consideration of all the essential and fundamental points of structure, wholly irrespective of external similarity of form and habits. Philosophical classifi- cation depends upon a due appreciation of what constitute the true points of difference and likeness amongst animals ; and we have already seen that these are morphological type and specialisation of function. Philosophical classification, therefore, is a formal expression of the facts and laws of Morphology and Physiology. It follows that the more fully the programme of a philosophical and strictly natural classifi- cation can be carried out, the more completely does it afford a condensed exposition of the fundamental construction of the objects classified. Thus, if the whale were placed by an arti- ficial grouping amongst the fishes, this would simply express the facts that its habits are aquatic and its body fish-like. When, on the contrary, we obtain a natural classification, and we learn that the whale is placed amongst the Mammalia, we then know at once that the young whale is born in a compa- SPECIES. 19 ratively helpless condition, and that its mother is provided with special mammary glands for its support \ this expressing a fundamental distinction from all fishes, and being associated with other equally essential correlations of structure. The entire animal kingdom is primarily divided into some half-a-dozen great plans of structure, the divisions thus formed being called " sub-kingdoms." The sub-kingdoms are, in turn, broken up into classes, classes into orders, orders into families, families into genera, and genera into species. We shall examine these successively, commencing with the consideration of a species, since this is the zoological unit of which the larger divisions are made up. Species. — No term is more difficult to define than " species," and on no point are zoologists more divided than as to what should be understood by this word. Naturalists, in fact, are not yet agreed as to whether the term species expresses a real and permanent distinction, or whether it is to be regarded merely as a convenient, but not immutable, abstraction, the employment of which is necessitated by the requirements of classification. By Buffon, " species" is defined as " a constant succession of individuals* similar to and capable of reproducing each other." De Candolle defines species as an assemblage of all those individuals which resemble each other more than they do others, and are able to reproduce their like, doing so by the generative process, and in such a manner that they may be supposed by analogy to have all descended from a single being or a single pair. \ -^ • M. de Quatrefages defines species as "an assemblage of individuals, more or less resembling one another, which are de- scended, or may be regarded as being descended, from a single primitive pair by an uninterrupted succession of families." Miiller defines species as " a living form, represented by in- dividual beings, which reappears in the product of generation with certain invariable characters, and is constantly repro- duced by the generative act of similar individuals." According to Woodward, " all the specimens, or individuals, which are so much alike that we may reasonably believe them to have descended from a common stock, constitute a species''1 From the above definitions it will be at once evident that there are two leading ideas in the minds of zoologists when * In using the term " individual," it must be borne in mind that the "zoological individual" is meant; that is to say, the total result of the development of a single ovum, as will be hereafter explained at greater length. 20 MANUAL OF ZOOLOGY. they employ the term species ; one of these being a certain amount of resemblance between individuals, and the other being the proof that the individuals so resembling each other have descended from a single pair, or from pairs exactly simi- lar to one another. The characters in which individuals must resemble one another in order to entitle them to be grouped in a separate species, according to Agassiz, "are only those determining size, proportion, colour, habits, and relations to surrounding circumstances and external objects." On a closer examination, however, it will be found that these two leading ideas in the definition of species — external resemblance and community of descent — are both defective, and liable to break down if rigidly applied. Thus, there are in nature no assemblages of plants or animals, usually grouped together into a single species, the individuals of which exactly resemble one another in every point. Every naturalist is compelled to admit that the individuals which compose any so-called species, whether of plants or animals, differ from one another to a greater or less extent, and in respects which may be regarded as more or less important. The existence of such individual differences is attested by the universal employment of the terms "varieties" and "races." Thus a "variety" comprises all those individuals which possess some distinctive peculiarity in common, but do not differ in other respects from another set of individuals sufficiently to entitle them to take rank as a separate species. A "race," again, is simply a permanent or "perpetuated" variety. The question, however, is this — How far may these differences amongst in- dividuals obtain without necessitating their being placed in a separate species ? In other words : How great is the amount of individual difference which is to be considered as merely " varietal" and at what exact point do these differences become of "specific" value ? To this question no answer can be given, since it depends entirely upon the weight which different naturalists would attach to any given individual difference.* Distinctions which appear to one observer as sufficiently great to entitle the individuals possessing them to be grouped as a distinct species, by another are looked upon as simply of varietal value ; and, in the nature of the case, it seems impos- sible to lay down any definite rules. To such an extent do individual differences sometimes exist in particular genera — * As an example of this, it is sufficient to allude to the fact that hardly any two botanists agree as to the number of species of Willows and Bram- bles in the British Isles. What one observer classes as mere varieties, another regards as good and distinct species. SPECIES. 21 termed "protean" or "polymorphic" genera — that the deter- mination of the different species and varieties becomes an almost hopeless task. Besides the individual differences which ordinarily occur in all species, other cases occur in which a species consists normally and regularly of two or even three distinct forms, which cannot be said to be mere varieties, since no inter- mediate forms can be discovered. When two such distinct forms exist the species is said to be " dimorphic," and when three are present it is called " trimorphic." Thus in dimorphic plants a single species is composed of two distinct forms, similar to one another in all respects except in their repro- ductive organs, the one form having a long pistil and short stamens, the other a short pistil with long stamens. In tri- morphic plants, the species is composed of three such distinct forms, which differ in like manner in the conformation of their reproductive organs, though they are otherwise undistinguish- able. — (Darwin.) Similar cases are known in animals, but in them the differences, though apparently connected with repro- duction, are not confined to the reproductive organs. Thus the females of certain butterflies normally appear under two or three entirely different forms, not connected by any inter- mediate links, and the same thing occurs in some of the Crustacea. As regards, therefore, the first point in the definition of species — namely, the external resemblance of assemblages of individuals — we are forced to conclude that no two individuals are exactly alike ; and that the amount and kind of external resemblance which constitutes a species is not a precise and invariable quantity, but depends upon the value attached to particular characters by any given observer. The second point in the definition of species — namely, com- munity of descent — is hardly in a more satisfactory condition, since the descent of any given series of individuals from a single pair, or from pairs exactly similar to one another, is at best but a probability, and is in no case capable of proof. In the case of the higher animals it can doubtless be shown that certain assemblages of individuals possess amongst themselves the power of fecundation and of producing fertile progeny, and that this power does not extend to the fecundation of in- dividuals belonging to another different assemblage. Amongst the higher animals, "crosses" or "hybrids" can only be pro- duced between closely -allied species, and when produced they are sterile, and are not capable of reproducing their like. In these cases, therefore, we may take this as a most satis- MANUAL OF ZOOLOGY. factory element in the definition of " species." The sterility, however, of hybrids is not universal, even amongst the higher animals ; and amongst plants no doubt can be entertained but that the individuals of species universally admitted to be dis- tinct are capable of mutual fertilisation ; the hybrid progeny thus produced being likewise fertile, and capable of reproduc- ing similar individuals. That this fertility is often irregular, and may be destroyed in a few generations, admits of explana- tion, and hardly alters the significance of these undoubted facts. Upon the whole, then, it seems in the meanwhile safest to adopt a definition of species which implies no theory, and does not include the belief that the term necessarily expresses a fixed and permanent quantity. Species, therefore, may be defined as an assemblage of individuals which resemble each other in their essential characters, are able, directly or indirectly, to pro- ditce fertile individuals, and which do not (as far as human ob- servation goes) give rise to individuals which vary from the general type through more than certain definite limits. The pro- duction of occasional monstrosities does not, of course, in- validate this definition. Genus is a term applied to groups of species which possess a community of essential details of structure. A genus may include a single species only, in cases where the combination of characters which make up the species are so peculiar that no other species exhibits similar structural characters ; or, on the other handr it may contain many hundreds of species. Families are groups of genera which agree in their general characters. According to Agassiz, they are divisions founded upon peculiarities of " form as determined by structure." Orders are groups of families related to one another by structural characters common to all. Classes are larger divisions, comprising animals which are formed upon the same fundamental plan of structure, but differ in the method in which the plan is executed (Agassiz). Sub-kingdoms are the primary divisions of the animal king- dom, which include all those animals which are formed upon the same structural or morphological type, irrespective of the degree to which specialisation of function may be carried. Impossibility of a Linear Classification. — It has sometimes been thought that the animal kingdom can be arranged in a linear series, every member of the series being higher in point of organisation than the one below it. As we have seen, how- ever, the status of any given animal depends upon two condi- tions— one its morphological type, the other the degree to which specialisation of function is carried. Now, if we take REPRODUCTION. 23 two animals, one of which belongs to a lower morphological type than the other, no degree of specialisation of function, however great, will place the former above the latter, as far as its type of structure is concerned, though it may make the former a more highly organised animal. Every Vertebrate animal, for example, belongs to a higher morphological type than every Mollusc ; but the higher Molluscs, such as cuttle- fishes, are much more highly organised, as far as their type is concerned, than are the lowest Vertebrata. In a linear classi- fication, therefore, the cuttle fishes should be placed above the lowest fishes — such as the lancelet — in spite of the fact that the type upon which the latter are constructed is by far the highest of the two. It is obvious, therefore, that a linear classification is not possible, since the higher members of each sub-kingdom are more highly organised than the lower forms of the next sub- kingdom in the series, at the same time that they are con- structed upon a lower morphological type. TO. REPRODUCTION. Reproduction is the process whereby new individuals are generated and the perpetuation of the species insured. The methods in which this end may be attained exhibit a good deal of diversity, but they may be all considered under two heads. I. Sexual Reproduction. — This consists essentially in the production of two distinct elements, a germ-cell or ovum, and a sperm-cell or spermatozoid, by the contact of which the ovum — now said to be "fecundated" — is enabled to develop itself into a new individual. As a rule, the germ-cell is pro- duced by one individual (female) and the spermatic element by another (male) ; in which case the sexes are said to be dis- tinct, and the species is said to be " dioecious." In other cases the same individual has the power of producing both the essential elements of reproduction ; in which case the sexes are said to be united, and the individual is said to be " her- maphrodite," "androgynous," or "monoecious." In the case of hermaphrodite animals, however, self-fecundation — contrary to what might have been expected — rarely constitutes the re- productive process ; and as a rule the reciprocal union of two such individuals is necessary for the production of young. Even amongst hermaphrodite plants, where self-fecundation may, and certainly does, occur, provisions seem to exist by which perpetual self-fertilisation is prevented, and the influence 24 MANUAL OF ZOOLOGY. of another individual secured at intervals. Amongst the higher animals sexual reproduction is the only process whereby new individuals can be generated. II. Non-sexual Reproduction. — Amongst the lower animals fresh beings may be produced without the contact of an ovum and a sperm atozoid ; that is to say, without any true generative act. The processes by which this is effected vary in different animals, and are all spoken of as forms of " asexual " or " agamic " reproduction. As we shall see, ho\vever, the true " individual " is very rarely produced otherwise than sexually, and most forms of agamic reproduction are really modifica- tions of growth. a. Gemmation and Fission. — Gemmation, or budding, con- sists in the production of a bud, or buds, generally from the exterior, but sometimes from the interior, of the body of an animal, which buds are developed into independent beings, which may or may not remain permanently attached to the parent organism. Fission differs from gemmation solely in the fact that the new structures in the former case are pro- duced by a division of the body of the original organism into separate parts, which may remain in connection, or may under- go detachment. The simplest form of gemmation, perhaps, is seen in the power possessed by certain animals of reproducing parts of their bodies which they may have lost. Thus, the Crustacea possess the power of reproducing a lost limb, by means of a bud which is gradually developed till it assumes the form and takes the place of the missing member. In these cases, how- ever, the process is not in any way generative, and the pro- duct of gemmation can in no sense be spoken of as a distinct being (or zooid). Another form of gemmation may be exemplified by what takes place in the Foraminifera, one of the classes of the Protozoa. The primitive form of a Foraminifer is simply a little sphere of sarcode, which has the power of secreting from its outer surface a calcareous envelope ; and this condition may be permanently retained (as in Lagena). In other cases a process of budding or gemmation takes place, and the prim- itive mass of sarcode produces from itself, on one side, a second mass exactly similar to the first, which does not detach itself from its parent, but remains permanently connected with it. This second mass repeats the process of gemmation as before, and this goes on — all the segments remaining attached to one another — until a body is produced, which consists of a number of little spheres of sarcode in organic connection REPRODUCTION. 25 with one another, and surrounded by a shell, often of the most complicated description. In this case, however, the buds produced by the primitive spherule are not only not detached, but they can only remotely be regarded as independ- ent beings. They are, in all respects, identical with the prim- ordial segment, and it is rather a case of " vegetative " repeti- tion of similar parts. Another form of gemmation is exhibited in such an organ- ism as the common sea-mat (Flustra), which is a composite organism composed of a multitude of similar beings, each of which inhabits a little chamber, or cell ; the whole forming a structure not unlike a sea-weed in appearance. This colony is produced by gemmation from a single primitive being (" poly- pide "), which throws out buds, each of which repeats the pro- cess, apparently almost indefinitely. All the buds remain in contact and connected with one another, but each is, neverthe- less, a distinct and independent being, capable of performing all the functions of life. In this case, therefore, each one of the innumerable buds becomes an independent being, similar to, though not detached from, the organism which gave it birth. This is an instance of what is called " continuous gem- mation." In other cases — as in the common fresh-water polype or Hydra — the buds which are thrown out by the primitive or- ganism become developed into creatures exactly resembling the parent, but, instead of remaining permanently attached, and thus giving rise to a compound organism, they are de- tached to lead an entirely independent existence. This is a simple instance of what is termed " discontinuous gemmation." The method and results of fission may be regarded as essen- tially the same as in the case of gemmation. The products of the division of the body of the primitive organism may either remain undetached, when they will give rise to a composite structure (as in many corals), or they may be thrown off and live an independent existence (as in some of the Hydrozoa). We are now in a position to understand what is meant, strictly speaking, by the term " individual." In zoological lan- guage, an individual is defined as " equal to the total result of the development of a single ovum" Amongst the higher animals there is no difficulty about this, for each ovum gives rise to no more than one single being, which is incapable of repeating it- self in any other way than by the production of another ovum; so that an individual is a single animal. It is most import- ant, however, to comprehend that this is not necessarily or always the case. In such an organism as the sea-mat, the 2(5 MANUAL OF ZOOLOGY. ovum gives rise to a primitive polypide which repeats itself by a process of continuous gemmation, until an entire colony is produced, each member of which is independent of its fellows, and is capable of producing ova. In such a case, therefore, the term u individual " must be applied to the entire colony, since this is the result of the development of a single ovum. The separate beings which compose the colony are technically called " zooids." In like manner, the Hydra which produces fresh and independent Hydrse by discontinuous gemmation, is not an " individual," but is a zooid. Here the zooids are not permanently united to one another, and the " individual" Hydra consists really of the primitive Hydra, plus all the detached Hydrae to which it gave rise. In this case, therefore, the " indi- vidual " is composed of a number of disconnected and wholly independent beings, all of which are the result of the develop- ment of a single ovum. It is to be remembered that both the parent zooid and the "produced zooids" are capable of giving rise to fresh Hydras by a true generative process. It must also be borne in mind that this production of fresh zooids by a process of gemmation is not so essentially different to the true sexual process of reproduction as might at first sight appear, since the ovum itself may be regarded merely as a highly spe- cialised bud. In the Hydra, in fact, where the ovum is pro- duced as an external process of the wall of the body, this like- ness is extremely striking. The ovarian bud, however, differs from the true gemmae or buds in its inability to develop itself into an independent organism, unless previously brought into contact with another special generative element. The only exceptions to this statement are in the rare cases of true "par- thenogenesis," to be subsequently alluded to. b. Reproduction by Internal Gemmation. — Before considering the phenomena of " alternate generations," it will be as well to glance for a moment at a peculiar form of gemmation exhi- bited by some of the Polyzoa, which is in some respects inter- mediate between ordinary discontinuous gemmation and alternation of generations. These organisms are nearly allied to the sea-mat, already spoken of, and, like it, can reproduce themselves by continuous gemmation (forming colonies), by a true sexual process, and rarely by fission. In addition to all these methods they can reproduce themselves by the formation of peculiar internal buds, which are called " statoblasts." These buds are developed upon a peculiar cord, which crosses the body-cavity, and is attached at one end to the fundus of the stomach. When mature they drop off from this cord, and lie loose in the cavity of the body, whence they are liberated on ALTERNATION OF GENERATIONS. 2/ the death of the parent organism. When thus liberated, the statoblast, after a longer or shorter period, ruptures and gives exit to a young Polyzoon, which has essentially the same structure as the adult. It is, however, simple, and has to undergo a process of continuous gemmation before it can assume the compound form proper to the adult. As regards the nature of these singular bodies, "the in- variable absence of germinal vesicle and germinal spot, and their never exhibiting the phenomena of yelk-cleavage, inde- pendently of the conclusive fact that true ova and ovary occur elsewhere in the same individual, are quite decisive against their being eggs. We must then look upon them as gemmce peculiarly encysted, and destined to remain for a period in a quiescent or pupa-like state." — (Allman.) c. Alternation of Generations. — In the case of the Hydra and the sea-mat, which we have considered above, fresh zooids are produced by a primordial organism by gemmation ; the beings thus produced (as well as the parent) being capable not only of repeating the gemmiparous process, but also of producing new individuals by a true generative act. We have now to consider a much more complex series of pheno- mena, in which the organism which is developed from the primitive ovum produces by gemmation two sets of zooids, one of which is destitute of sexual organs, and is capable of per- forming no other function than that of nutrition, whilst the other is provided with reproductive organs, and is destined for the perpetuation of the species. In the former case the produced zooids all resembled each other, and the parent organism which gave rise to them ; in the latter case, the pro- duced zooids are often utterly unlike each other and unlike the parent, since their functions are entirely different. The simplest form of the process is seen in certain of the Hydroid Polypes, such as Campanularia. The ovum of Cam- panularia is a free-swimming ciliated body, which, after a short locomotive existence, attaches itself to some submarine object, develops a mouth and tentacles, and commences to pro- duce zooids like itself by a process of continuous gemmation. These remain permanently attached to one another, with the result that a compound organism is produced, consisting of a number of zooids, or " polypites," organically connected to- gether, but enjoying an independent existence. None of the zooids, however, are provided with sexual organs ; and though there is theoretically no limit to the size which the colony may reach by gemmation, its buds are not detached, and the species would, therefore, die out, unless some special provision 28 MANUAL OF ZOOLOGY. were made for its preservation. Besides these nutritive zooids, however, other buds are produced which differ con- siderably in appearance from the former, and which have the power of generating the essential elements of reproduction. These generative zooids derive their nourishment from the materials collected by the nutritive zooids, but only live until the ova are matured in their interior and liberated, when they disappear. The ova thus produced become free-swimming ciliated bodies, such as the one with which the cycle began. In this case, therefore, the " individual " Campanularia con- sists of a series of nutritive zooids, collectively called the " trophosome," and another series of reproductive zooids, col- lectively called the " gonosome," the entire series often remain- ing in organic connection. In other forms nearly allied to Campanularia (such as Coryne) the process advances a step further. In Coryne the generative buds, or zooids, do not produce the reproductive elements as long as they remain attached to the parent colony ; but they require a preliminary period of independent existence. For this purpose they are specially organised, and when sufficiently matured they are detached from the stationary colony. The generative zooid now appears as an entirely independent being, described as a species of jelly-fish (or Medusa) under the name of Sarsia. It consists of a bell- shaped disc, by means of which it is enabled to swim freely ; from the centre of this disc depends a nutritive process, with a mouth and digestive cavity, whereby the organism is able to increase considerably in size. The substance of the disc is penetrated by a complex system of canals, and from its margin hang a series of tentacular processes. After a period of independent locomotive existence, the Medusa attains its full growth, when it develops ova and spermatozoa. By the contact of these embryos are produced ; but these, instead of resembling the jelly-fish by which they were immediately gene- rated, proceed to develop themselves into the fixed Hydroid colony by which the Medusa was originally produced. Still more extraordinary phenomena have been discovered in other Hydrozoa, as in many of the Lucernarida. In these the ovum gives rise (as in Campanularia) to a locomotive ciliated body, which ultimately fixes itself, becomes trumpet- shaped, and develops a mouth and tentacles at its expanded extremity, when it is known as the "hydra-tuba," from its resemblance to the fresh-water polype, or Hydra. The hydra- tuba has the power of multiplying itself by gemmation, and it can produce large colonies in this way; but it does not ALTERNATION OF GENERATIONS. 2Q obtain the power of generating the essential elements of reproduction. Under certain circumstances, however, the hydra-tuba enlarges, and, after a series of preliminary changes, divides by transverse fission into a number of segments, each of which becomes detached and swims away. These liberated segments of the little hydra-tuba (it is about half an inch in height) now live as entirely independent beings, which were described by naturalists as distinct animals, and were called Ephyrae. They are provided with a swimming - bell, or "umbrella," by means of which they propel themselves through the water, and with a mouth and digestive cavity. They now lead an active life, feeding eagerly, and attaining in some instances a perfectly astonishing size (the Medusoids of some species are several feet in circumference). After a while they develop the essential elements of reproduction, and after the fecundation and liberation of their ova they die. The ova, however, are not developed into the free-swimming and comparatively gigantic jelly-fish by which they were immediately produced, but into the minute, fixed, sexless hydra-tuba. We thus see that a small, sexless zooid, which is capable of multiplying itself by gemmation, produces by fission several independent locomotive beings, which are capable of nourish- ing themselves and of performing all the functions of life. In these are produced generative elements, which give rise by their development to the little fixed creature with which the series began. To the group of phenomena of which the above are examples, the name "alternation of generations " was applied by Steen- strup ; but the name is not an appropriate one, since the process is truly an alternation of generation with gemmation or fission. The only generative act takes place in the repro- ductive zooid, and the production of this from the nutritive zooid is a process of gemmation or fission, and not a pro- cess of generation. The "individual," in fact, in all these cases, must be looked upon as a double being composed of two factors, both of which lead more or less completely inde- pendent lives, the one being devoted to nutrition, the other to reproduction. The generative being, however, is in many cases not at first able to mature the sexual elements, and is, therefore, provided with the means necessary for its growth and nourishment as an independent organism. It must also be remembered that the nutritive half of the " individual " is usually, and the generative half sometimes, compound; that is to say, composed of a number of zooids produced by con- 30 MANUAL OF ZOOLOGY. tinuous gemmation ; so that the zoological individual in these cases becomes an extremely complex being. These phenomena of so-called " alternation of generations," or " metagenesis," occur in their most striking form amongst the Hydrozoa ; but they occur also amongst many of the intes- tinal worms (Entozoa), and amongst some of the Tunicata (Molluscoida). d. Parthenogenesis. — "Parthenogenesis "is the term employed to designate certain singular phenomena, resulting in the production of new individuals by virgin females without the intervention of a male. By Professor Owen, who first em- ployed the term, parthenogenesis is applied also to the processes of gemmation and fission, as exhibited in sexless beings or in virgin females ; but it seems best to consider these phenomena separately. Strictly, the term parthenogenesis ought to be confined to the production of new individuals from virgin females by means of ova, which are enabled to develop themselves without the contact of the male element. The difficulty in this definition is found in framing an exact definition of an ovum, such as will distinguish it from an in- ternal gemma or bud. No body, however, should be called an " ovum " which does not exhibit a germinal vesicle and germinal spot, and which does not exhibit the phenomenon known as segmentation of the yelk. Moreover, ova are almost invariably produced by a special organ, or ovary. As examples of parthenogenesis we may take what occurs in plant-lice (Aphides) and in the honey-bee ; but it will be seen that in neither of these cases are the phenomena so unequivo- cal, or so well ascertained, as to justify a positive assertion that they are truly referable to parthenogenesis in the above restricted sense of the term. The Aphides, or plant-lice, which are so commonly found parasitic upon plants, are seen towards the close of autumn to consist of male and female individuals. By the sexual union of these true ova are produced, which remain dormant through the winter. At the approach of spring these ova are hatched ; but instead of giving birth to a number of males and females, all the young are of one kind, variously regarded as neuters, virgin females, or hermaphrodites. Whatever their true nature may be, these individuals produce viviparously a brood of young which resemble themselves ; and this second generation, in like manner, produces a third, and so the process may be repeated, for as many as ten or more generations, throughout the summer. When the autumn comes on, however, the vivi- parous Aphides produce — in exactly the same manner — a final PARTHENOGENESIS. 3! brood ; but this, instead of being composed entirely of similar individuals, is made up of males and females. Sexual union now takes place, and ova are produced and fecundated in the ordinary manner. The bodies from which the young of the viviparous Aphides are produced are variously regarded as internal buds, as "pseud- ova " (i.e. as bodies intermediate between buds and ova), and as true ova. Without entering into details, it is obvious that there is only one explanation of these phenomena which will justify us in regarding the case of the viviparous Aphides as one of true parthenogenesis, as above defined. If, namely, the spring broods are true females, and the bodies which they produce in their interior are true ova, then the case is one of genuine par- thenogenesis, for there are certainly no males. The case might still be called one of parthenogenesis, even though the bodies from which these broods are produced be regarded as internal buds, or as "pseudova ;" for a true ovum is essentially a bud. If, however, Balbiani be right, and the viviparous Aphides are really hermaphrodite, then, of course, the phenomena are of a much less abnormal character. In the second case of alleged parthenogenesis which we are about to examine — namely, in the honey-bee — the phenomena which have been described cannot be said to be wholly free from doubt. A hive of bees consists of three classes of indivi- duals— T. A "queen," or fertile female; 2. The "workers," which form the bulk of the community, and are really undeveloped or sterile females ; and, 3. The " drones," or males, which are only produced at certain times of the year. We have here three distinct sets of beings, all of which proceed from a single fertile individual, and the question arises, In what manner are the differences between these produced ? At a certain period of the year the queen leaves the hive, accompanied by the drones (or males), and takes what is known as her " nuptial flight " through the air. In this flight she is impregnated by the males, and it is immaterial whether this act occurs once in the life of the queen, or several times, as asserted by some. Be this as it may, the queen, in virtue of this single impregna- tion, is enabled to produce fresh individuals for a lengthened period,, the semen of the males being stored up in a receptacle which communicates by a tube with the oviduct, from which it can be shut off at will. The ova which are to produce workers (undeveloped females) and queens (fertile females) are fertil- ised on their passage through the oviduct, the semen being allowed to escape into the oviduct for this purpose. The sub- 32 MANUAL OF ZOOLOGY. sequent development of these fecundated ova into workers or queens depends entirely upon the form of the cell into which the ovum is placed, and upon the nature of the food which is supplied to the larva. So far there is no doubt as to the nature of the phenomena which are observed. It is asserted, how- ever, By Dzierzon and Siebold, that the males or drones are produced by the queen from ova which she does not allow to come into contact with the semen as they pass through the oviduct. This assertion is supported by the fact that if the communication between the receptacle for the semen and the oviduct be cut off, the queen will produce nothing but males. Also, in crosses between the common honey-bee and the Ligu- rian bee, the queens and workers alone exhibit any intermediate characters between the two forms, the drones presenting the un- mixed characters of the queen by whom they were produced. If these observations are to be accepted as established, and upon the whole there can be no hesitation in accepting them as in the main correct, then the drones are produced by a true process of parthenogenesis ; but some observers maintain that the development of any given ovum into a drone is really due — as in the case of the queens and workers — to the special cir- cumstances under which the larva is brought up. There are various other cases in which parthenogenesis is said to occur, but the above will suffice to indicate the general character of the phenomena in question. The theories of par- thenogenesis appear to be too complex to be introduced here ; and there is the less to regret in their omission, as naturalists have not yet definitely adopted any one explanation of the phenomena to the exclusion of the rest. First Law of Quatrefages. — From the phenomena of asexual reproduction in all its forms, M. de Quatrefages has deduced the following generalisation : — " The formation of new individuals may take place, in some instances, by gemmation from, or division of, the parent-being ; but this process is an exhaustive one, and cannot be carried out indefinitely ; when, therefore, it is necessary to insure the continuance of the species, the sexes must present themselves, and the germ and sperm must be allowed to come in contact with one another." It should be added that the act of sexual reproduction, though it insures the perpetuation of the species, is very de- structive to the life of the individual. The formation of the essential elements of reproduction appears to be one of the highest physiological acts of which the organism is capable, and it is attended with a corresponding strain upon the vital DEVELOPMENT. 33 energies. In no case is this more strikingly exhibited than in the majority of insects, which pass the greater portion of their existence in a sexually immature condition, and die almost immediately after they have become sexually perfect, and have consummated the act whereby the perpetuation of the species is secured. ii. DEVELOPMENT, TRANSFORMATION, AND METAMORPHOSIS. Development is the general term applied to all those changes which a germ undergoes before it assumes the characters of the perfect individual ; and the chief differences which are ob- served in the process as it occurs in different animals consist simply in the extent to which these changes are external and visible, or are more or less completely concealed from view. For these differences the terms " transformation" and "meta- morphosis " are employed ; but they must be regarded as essen- tially nothing more than variations of development Transformation is the term employed by Quatrefages to de- signate " the series of changes which every germ undergoes in reaching the embryonic condition ; those which we observe in every creature still within the egg ; those, finally, which the species born in an imperfectly developed state present in the course of their external life." Metamorphosis is defined by the same author as including the alterations which are " undergone after exclusion from the egg, and which alter extensively the general form and mode of life of the individual." Though by no means faultless, these terms are sufficiently convenient, if it be remembered that they are merely modifi- cations of development, and express differences of degree and not of kind. An insect, such as a butterfly, is the best illus- tration of what is meant by these terms. All the changes which are undergone by a butterfly in passing from the fe- cundated ovum to the condition of an imago, or perfect insect, constitute its development. The egg which is laid by a butterfly undergoes a series of changes which eventuate in its giving birth to a caterpillar, these preliminary changes constitut- ing its transformation. The caterpillar grows rapidly, and after several changes of skin becomes quiescent, when it is known as a "chrysalis." It remains for a longer or shorter time in this quiescent and apparently dead condition, during which period developmental changes are going on rapidly in its interior. Finally, the chrysalis ruptures, and there escapes from it the perfect winged insect. To these changes the term VOL. i. c 34 MANUAL OF ZOOLOGY. metamorphosis is rightly applied. These changes, however, do not differ in kind from the changes undergone by a Mammal; the difference being that in the case of a Mammal the ovum is retained within the body of the parent, where it undergoes the necessary developmental changes, so that at birth it has little to do but grow, in order to be converted into the adult animal. From these considerations we arrive at the second law laid down by Quatrefages : — " Those creatures whose ova — owing to an insufficient supply of nutritious contents, and an incapacity on the part of the mother to provide for their complete de- velopment within her own substance — are rapidly hatched, give birth to imperfect offspring, which, in proceeding to their definitive characters, undergo several alterations in structure and form, known as metamorphoses." Retrograde Development. — Ordinarily speaking, the course of development is an ascending one, and the adult is more highly organised than the young ; but there are cases in which there is an apparent reversal of this law, and the adult is to all appearance a degraded form when compared with the embryo. This phenomenon is known as " retrograde " or "recurrent" development; and well-marked instances are found amongst the Cirripedia and Lernaese, both of which belong to the Crustacea. Thus, in the Cirripedes (acorn-shells, &c.) and in the parasitic Lernaese the embryo is free-swimming and provided with organs of vision and sensation, being in most respects similar to the permanent condition of certain other Crustacea, such as the Cypris (Ostracoda). The adult, however, in both cases, is degraded into a more or less completely sedentary animal, more or less entirely deprived of organs of sense, and leading an almost vegetative life. As a compensation, repro- ductive organs are developed in the adult, and it is in this respect superior to the locomotive, but sexless, larva. 12. SPONTANEOUS GENERATION. Spontaneous or Equivocal generation is the term applied to the alleged production of living beings without the pre- existence of germs of any kind, and therefore without the pre-existence of parent organisms. The question is one which has been long and closely disputed, and is far from being settled ; so that it will be sufficient to indicate the facts upon which the theory rests. . If an animal or vegetable substance be soaked in hot or SPONTANEOUS GENERATION. 35 cold water, so as to make an organic infusion, and if this in- fusion be exposed for a sufficient length of time to the air, the following series of changes is usually observed : — 1. At the end of a longer or shorter time, there forms upon the surface of the infusion a thin scum, or pellicle, which, when examined microscopically, is found to consist of an in- calculable number of extremely minute molecules. 2. In the next stage these molecules appear, many of them, to have melted together in twos and threes to form short fila- ments, called " bacteria," which become longer by the appo- sition of fresh molecules at their extremities, or by uniting with one another, when they are termed " vibriones." Both the bacteria and the vibrios now exhibit a vibratile or serpen- tine movement through the surrounding fluid. 3. After a varying period, the bacteria and vibrios become motionless, and disintegrate so as to produce again a finely molecular pellicle. 4. Little spherical bodies now appear, each of which is provided with a vibratile cilium with which it moves actively through the infusion. (Monas lens.) 5. Varied forms of ciliated Infusoria — some which possess a mouth and are otherwise highly organised — make their appearance in the fluid. The above is the general sequence of the phenomena which have been observed, and the following are the two theories which have been advanced to account for them : — a. By the advocates of spontaneous generation, or " Hetero- geny," it is affirmed that the Infusoria, which finally appear in the infusion, are produced spontaneously out of the molecular pellicle, the molecules of which are also of spontaneous origin, and are not derived from any pre-existing germs. b. By the " panspermists," or the opponents of spontaneous generation, it is alleged, on the other hand, that the produc- tion of Bacteria, Vibrios, Monads, and Infusoria, in organic infusions, is due simply to the fact that the atmosphere, and probably the fluid itself, is charged with innumerable germs — too minute, perhaps, to be always detectable by the microscope — which, obtaining access to the fluid, and finding there favourable conditions, are developed into living beings. A large number of elaborate experiments have been carried out to prove that atmospheric air is absolutely necessary for the production of these living beings, and that if the air be properly purified by passage through destructive chemical reagents, no such organisms will be produced, provided that the infusion have been previously boiled. As the results of 36 MANUAL OF ZOOLOGY. all these experimental trials have hitherto proved more or less contradictory, it is unnecessary to enter into the question further, and it will be sufficient to indicate the following general considerations : — a. The primary molecules which appear in the fluid are extremely minute, and if they are developed from germs, these may be so small as to elude any power of the microscope yet known to us. As they subsequently become converted into bacteria and vibrios, and as there can be little dispute as to these being truly living organisms, we are obliged to believe that they must have had some definite origin. It appears, however, to be hardly philosophical to assume that they form themselves out of the inorganic materials of the infusion ; since this implies the sudden appearance, or creation, of new force, for which there seems to be no means of accounting. b. The nature of the vibrios and bacteria must be looked upon as quite uncertain. To say the least of it, they are quite as likely to be plants as animals ; and the most probable hypo- thesis would place the former near the filamentous Confervse. c. What has been said above with regard to the origin of the bacteria and vibrios applies equally to the origin of the Monads, which appear in the infusion subsequently to the death of the vibrios. d. These Monads, as • shown by recent researches, are pro- bably to be looked upon as the embryonic, or larval, forms of the higher Infusoria which succeed them. cium is effected either non-sexually by fission (i.e. by a simple division of its substance) or by a true sexual process. In this latter method two ParamKcia come together, and adhere closely to one another by their ven- 63 MANUAL OF ZOOLOGY. tral surfaces. The "nucleus," which is truly an ovary, enlarges, and a number of ovules are formed in its interior. In like manner, the " nucleolus " of each, which is really a testis or sper- marium, also enlarges, and develops in its interior a number of fusiform or rod-like bodies, which are believed to be sperma- tozoa. The nucleolus of each then passes into the body of the other, the act of transference being effected through the mouth. Contact of the two reproductive elements then takes place, and a number of germs are produced, which, after their liberation from the body of the parent, are developed into adult Paramoecia. Vorticella (fig. n, and constituting the « ster- trating the composition of the num proper ; the arc being completed by tegumentary skeleton of the t wo lateral pieces, termed the " episterna." Crustacea (after Milne-Ed- These plates are usually more or less com- Tergal pieces ;°T* Ephneral pletely anchylosed together, and the true pieces ; v. Ventral arc ; s JT structure of the somite in these cases is often Sternal pieces; //Episternal shown by what are called "apodemata." extremiui^ rtl°n °f ^ These <«* sePta which Proceed inwards from the internal surface of the somite, penetrating more or less deeply between the various organs enclosed by the ring, and always proceeding from the line of junction of the different pieces of the segment (fig. 58). It must be borne in mind that though the so-called " head"- that is to say, the " cephalothorax" — of the Lobster is produced by an amalgamation of the various somites of the head and thorax, this is not the case with the great shield which covers this portion of the body. This shield — the so-called " cephalic buckler," or " carapace " — is not produced by the union of the tergal arcs of the various cephalic and thoracic segments, as would at first sight appear to be the case. On the contrary, the " carapace" in the higher Crustacea is produced by an enor- mous development of the tergal pieces, or of the "epimera" of one or two of the cephalic segments : the tergal arcs of the remaining somites being overlapped by the carapace and re- maining undeveloped. Examining the somites from behind forwards (for simplici- ty's sake), the last segment comes to be first described. This is the so-called " telson," which forms the last articulation of ANNULOSA : CRUSTACEA. 195 the abdomen, and never bears any appendages. For this reason, many authorities do not regard it as a somite, properly speaking, but simply as an azygos appendage — that is to say, as an appendage without a fellow. In the next segment (the last but one, or the last, of the abdomen, according to the view Fig. 59. — Morphology of Lobster, i. Lobster with all the appendages, except the terminal swimmerets, removed, and the abdominal somites separated from one another, ca Carapace ; t Telson. 2. The third abdominal somite separated, t Ter- gum ; s Sternum ; / Pleuron ; a Protopodite ; b Exopodite ; c Endopodite. 3. One of the last pair of foot-jaws or maxillipedes. e Epipodite ; g Gill ; the other letters as before. which is taken of the " telson "), there is a pair of natatory ap- pendages, called "swimmerets." Each swimmeret (fig. 59, 2) consists of a basal joint, which articulates with the sternum, 196 MANUAL OF ZOOLOGY. and is called the " protopodite " or propodite, and of two di- verging joints, which are attached to the former ; the outer of these being called the " exopodite," and the inner the " endo- podite." In this particular segment, the exopodite and endo- podite are greatly expanded, so as to form powerful paddles, and the exopodite is divided into two by a transverse joint. In the succeeding somites of the abdomen — with the exception of the first, in which there is some modification — the appen- dages are in the form of swimmerets, essentially the same as those attached to the penultimate segment, and differing only in the fact, that the exopodite and endopodite are much nar- rower, and the former is undivided (fig. 59, 2). The last thoracic somite — immediately in front of the abdomen — car- ries a pair of the walking or ambulatory legs, each consisting of a short basal piece, or "propodite," and of a long jointed "endopodite," the "exopodite" not being developed. The next thoracic segment carries another pair of ambulatory limbs, quite similar to the last, except for the fact that the protopo- dite bears a process which serves to keep the gills apart, and is termed the " epipodite." The succeeding segment supports a pair of limbs similar to the last in all respects, except that its extremities, instead of being simply pointed, are converted into nipping claws, or "chelae." The next segment of the thorax carries a pair of chelate limbs, just like the preceding, and the next is furnished with appendages, which are essen- tially the same in structure, but are much larger, constituting the great claws. The next two segments of the thorax, and the segment in front of these (by some looked upon as belong- ing to the head, by others as referable to the thorax), bear each a pair of modified limbs, which are termed "maxillipedes," or "foot-jaws." These are simply limbs with the ordinary structure of protopodite, exopodite, endopodite, and epipodite, but modified to serve as instruments of mastication, the hind- most pair being less altered than the two anterior pairs (fig. 59, 3). The next two somites carry appendages, which are in the form of jaws, and are termed respectively the first and second pairs of " maxillae." Each consists of the parts aforementioned, but the epipodite of the first pair of maxillae is rudimentary, whilst that of the second pair is large, and is shaped like a spoon. It is termed the " scaphognathite," and its function is to cause a current of water to traverse the gill-chamber by con- stantly baling water out of it. The next segment carries the biting jaws, or "mandibles; " .each of which consists of a large protopodite, and a small endopodite, which is termed the " palp," whilst the exopodite is undeveloped. The aperture ANNULOSA: CRUSTACEA. 197 of the mouth is situated between the bases of the mandibles, bounded behind by a forked process, called the " labium," or " metastoma," and in front by a single plate, called the " la- brum" (upper lip). The next segment bears the long antennae, or feelers (fig. 71, ga)t each consisting of a short protopodite, and a long, jointed, and segmented endopodite, with a very rudimentary exopodite. In front of the great antennae are the next pair of appendages, termed the " antennules," or smaller antennae (fig. 71, a), each composed of a protopodite, and a segmented endopodite and exopodite, which are nearly of equal size. Finally, attached to the first segment of the head are the eyes, each of which is borne upon an eye-stalk formed by the protopodite. The gill-chamber is formed by a great prolonga- tion downwards of the pleura of the thoracic segments, and the gills are attached to the bases of the legs. As regards the digestive system of the Crustacea, the ali- mentary canal is, with few exceptions, continued straight from the mouth to the aperture of the anus. There are no salivary glands, but a large and well-developed liver is usually present. A heart is generally, but not always, present. In most of the lower forms it is a long vasiform tube, very like the " dorsal vessel" of Insects. The exact course of the cir- culation has been differently stated by different writers, but the following appear to be the facts of the case : In some of the lower forms (e.g., Copepodd) there are no arterial vessels, and the venous blood returned from the body is collected into a venous sinus — the so-called " pericardium," which surrounds the heart and opens into it by valvular apertures. In the higher forms, the heart gives off a number of arteries by which the blood is driven to all parts of the body and to the gills. The arteries do not terminate in a system of capillary vessels, but in a series of irregular lacunae occupying all the interstices between the different organs of the body. From this inter- stitial lacunar system arise the venous trunks, which are gene- rally dilated into more or less extensive sinuses. Whether the whole of the venous blood is submitted to the action of the gills, or whether the blood sent to the gills is derived mainly from the heart, is a matter of question ; but the former is the more probable view. Be this as it may, the blood is invariably returned to a large venous sinus which surrounds the heart, and opens into it by a number of valvular apertures. It follows from this description, that the heart of the Crustacea is mainly, if not altogether, a systemic heart, being concerned chiefly, if not en- tirely, in driving the aerated blood to all parts of the body. Distinct respiratory and circulatory organs may be altogether 198 MANUAL OF ZOOLOGY. wanting ; but, as a rule, distinct branchiae are present. The exact form and structure of the gills differ in different cases, but their leading modifications will be alluded to in treating of the different orders. TABULAR VIEW OF THE DIVISIONS OF THE CRUSTACEA. Sub-class I. EPIZOA (Haustellata). Order i. Ichthyophthira. Sub-class II. CIRRIPEDIA. ( Balanidae. Order 2. Thoracica. \ Vemicidse. ( Lepadidse. „ 3. Abdominalia. „ 4. Apoda. Sub-class III. ENTOMOSTRACA. 0rderS- °^a^,a- „ 6. Copepoda. „ 7. Cladocera. „ 8. Phyllopoda. Legion, Branchiopoda. „ 9. Trilobita. „ 10. Merostomata. Sub-class IV. MALACOSTRACA. Division A. EDRIOPHTHALMATA. Order n. Lcemodipoda. „ 12. Isopoda. „ 13. Amphipoda. Division B. PODOPHTHALMATA. Order 14. Stomapoda. „ 15. Decapoda. Tribe a. Macrura. „ b. Anomura. „ c. Brachyura. CHAPTER XXXII. EPIZOA AND CIRRIPEDIA. SUB-CLASS I. EPIZOA. (Haustellata). — The members of this sub- class of the Crustacea are in the adult state parasitic upon the bodies of fishes, and are usually deformed ; but in the young ANNULOSA: CRUSTACEA. 199 condition they are locomotive, and are furnished with antennae and eyes. The mouth is suctorial, and the limbs are terminated by suckers, hooks, or bristles. There are no differentiated respiratory organs, but respiration is performed by the surface of the body. The males are rudimentary, and are much smaller than the females, which are usually furnished with ex- ternal ovisacs. This division includes the single order Ichthyophthira, the characters of which are therefore the same as those of the sub- class, comprising various parasites upon fishes belonging to the genera Lerncea, Achtheres, Peniculus, &c. ORDER I. ICHTHYOPHTHIRA. — The members of this order are attached in the adult condition to the skin, eyes or gills of fishes, and when mature possess an elongated body, having a more or less distinct head, and in the females usually a pair of long, cylindrical ovisacs, depending from the extremity of the abdomen. Some adhere by a suctorial mouth, or by cephalic processes (Cephaluna) ; others are attached by a suctorial disc, developed at the extremities of the last pair of thoracic limbs, which are united together (Brachiuna)\ whilst in others (Onchu- na) attachment is effected by hooks at the free extremities of the first pair of thoracic limbs. — (Owen.) Fig. 60. — Ichthyophthira. a Free-swimming larva of Achtheres percarum, in its firs stage ; b Adult male of the same. Enlarged. (After Owen.) The males are usually not attached, but adhere to the fe- males, of which, from their much smaller size, they appear to be mere parasites. The chief anatomical peculiarities of the female are the following : — The head is provided usually with a pair of jointed antennae, and the body is divided into a cepha- lothorax and abdomen. The alimentary canal consists of a mouth, gullet, and intestine, terminating posteriorly in a distinct anus. The nervous system consists of a double ventral cord. The embryo (fig. 60, a) is free-swimming, and is provided with visual organs and locomotive appendages. The two sexes are now alike, and the conversion of the active embryo, 20O MANUAL OF ZOOLOGY. or larva, into the swollen and deformed adult, must be regarded as an instance of " retrograde metamorphosis." SUB-CLASS II. CIRRIPEDIA. — This sub-class includes, amongst others, the common Acorn-shells and the Barnacles or Goose- mussels. All the Cirripedia are distinguished by the fact, that, in the adult condition, they are permanently fixed to some solid object by the anterior extremity of the greatly metamor- phosed head ; the first three cephalic segments being much developed, and enclosing the rest of the body. The larva is free and locomotive, and the subsequent attachment, and con- version into the fixed adult, is effected by means of a peculiar secretion, or cement, which is discharged through the antennae of the larva, and is produced by a special cement-gland, which is really a portion of the ovary. In the Cirripedia^ therefore, the head of the adult is permanently fixed to some solid object, and the visceral cavity is protected by an articulated calcareous shell, or by a coriaceous envelope. The posterior extremity of the animal is free, and can be protruded at will through the orifice of the shell. This extremity consists of the abdomen, and of six pairs of forked, ciliated limbs, which are attached to the thorax, and serve to provide the animal with food. The two more important types of the Cirripedia are the Acorn- shells (Balanidce) and the Barnacles (Lepadidce.) In the former the animal is sessile, the larval antennae, through which the cement exudes, being imbedded in the centre of the mem- branous or calcareous "basis" of the shell. In the latter the animal is stalked, and consists of a " peduncle" and a "capi- tulum." The peduncle consists of the anterior extremity of the body, with the larval antennse, usually cemented to some foreign body. The capitulum is supported upon the peduncle, and consists of a case composed of several calcareous plates, united by a membrane, enclosing the remainder of the animal. Before giving a more detailed description of this singular and important sub-class, the following definition, as given by Owen, may be advantageously appended : — "Body, chitinous, or chitino-testaceous, sub-articulated, mostly symme- trical, with aborted antennae and eyes. Mouth, prominent, composed of a labrum, palpi, two mandibles, and two pairs of maxillae. Thorax, attached to the sternal internal surface of the carapace, with six pairs of multiarti- culate, biramous, setigerous limbs. Abdomen, rudimentary. Vascular system diffused ; white blood. Branchiae, when present, attached to the inferior lateral part of the surface. Most are hermaphrodite ; a few have minute, rudimentary, male individuals, parasitically attached to the females. Penis, proboscidiform, multiarticulate, attached to the hinder end of the abdomen. No oviducts. Metamorphosis and metagenesis, resulting in a permanent parasitic attachment of the fully-developed female or herma- phrodite individual." ANNULOSA: CRUSTACEA. 201 As regards the development of the Cirripedia, the larva is at first oval in shape, devoid of segmentation, and protected by a dorsal carapace. There is a single eye, two pairs of antennae, and three pairs of natatory limbs, of which the two posterior pairs are bifid at their extremities. The larva, in fact, in this stage very closely resembles some of the smaller Entomostraca. In a more advanced stage, the carapace becomes considerably altered, the great antennae become modified for prehension, the first pair of antennae (antennules) disappears, and the eye becomes double. In a still more advanced condition (fig. 61), a Fig. 61. — Locomotive young of Balanus. a Eye ; b Caudal bristles ; c Setigerous limbs. the anterior pair of natatory limbs become bifid, like the pos- terior ones; three additional pairs of limbs are developed behind those already existing ; the abdomen becomes defined from the thorax ; and the carapace is composed of two portions, or valves, which enclose the thorax and abdomen with their appendages. Finally, the young Cirripede fixes itself to some solid object by means of the prehensile antennae. " The * ce- ment-ducts ' can be traced as far as the third or ' disc-seg- ment * of the antennas. There the cement seems to transude and fasten down the disc ; soon both antennae are surrounded by a common border of cement, which gradually increases in extent after the metamorphosis. In the Lepas fascicularis the cement is poured forth in sufficient quantities to form, itself, the substance to which the peduncle of the adult barnacle adheres, and for a cluster of which barnacles it constitutes a central vesicular float." — (Owen.) The cement-gland, as shown by Darwin, is "part of, and continuous with, the branching ovaria," and the cement-ducts open through the prehensile antennae. The form of the adult, as already said, differs considerably, but the two most important types are those presented respec- tively by the Sessile and by the Pedunculated Cirripedia. In the common Acorn-shells (Balaniy fig. 62, a) the anterior portion of the head is not elongated, but is fixed to the centre of a basal, membranous, or shelly plate, termed the " basis," 202 MANUAL OF ZOOLOGY. which adheres by its external surface to some solid body. Above the basis rises a more or less limpet-shaped, or conical, shell, which is open at the top, but is capable of being corn- Fig. 62. — Morphology of Cirripedia. a Sessile Cirripede or Balanoid, Balanus sulcatus. b Pedunculate Cirripede or Lepadoid, Lepas anatifera. pletely closed by a pyramidal lid, or " operculum." Both the shell itself and the operculum are composed of calcareous plates, usually differing from one another in shape, and dis- tinguished by special names. Within the shell the animal is fixed, head downwards. The thoracic segments, six in num- ber, bear six pairs of limbs, each of which consists of a jointed protopodite and a much segmented exopodite and endopo- dite, both of which are ciliated, and constitute the so-called " cirri," from which the name of the sub-class is derived. These twenty-four cirri — the "glass hand" of the Balanus — are in incessant action, being protruded from the opening of the shell, and again retracted within it, constantly producing cur- rents of water, and thus bringing food to the animal. There are no specialised respiratory organs in the family of the Balanidce. In the Barnacles (Lepadidcz, fig. 62, b) the anterior ex- tremity of the animal is enormously elongated, forming with the prehensile antennae, the cement-ducts, and their exuda- tion, a long stalk or peduncle, whereby the animal is attached to some solid object. At its free extremity the peduncle bears the " capitulum," which corresponds to the shell of the Ba- lanoids, and is composed of various calcareous plates, united together by a membrane, moved upon one another by appro- priate muscles, and protecting in their interior the body of the animal with its appendages. The thorax and limbs resemble those of the Balanus ; but " slender appendages, which from their position and connections are homologous with the branchiae of the higher Crustacea, are attached to, or near to, the bases of a greater or less number of the thoracic feet, and ANNULOSA: CRUSTACEA. 203 extend in an opposite direction outside the visceral sac."- (Owen.) All the BalanidcR are hermaphrodite, and this is also the case with most of the Lepadida, but some extraordinary exceptions occur in this latter order. Thus, in some species of Scalpellum the individual forming the ordinary shell is female, and each female has two males lodged in transverse depressions within the shell. These males " are very singular bodies ; they are sac-formed, with four bead-like, rudimental valves at their upper ends ; they have a conspicuous internal eye ; they are absolutely destitute of a mouth, or stomach, or anus ; the cirri are rudimental and furnished with straight spines, serving apparently to protect the entrance of the sac ; the whole animal is attached like the ordinary Cirripede, first by the prehensile antennae, and afterwards by the cementing substance ; the whole animal may be said to consist of one great sperm-receptacle, charged with spermatozoa ; as soon as these are discharged, the animal dies." "A far more singular fact remains to be told ; Scalpellum vulgare is, like ordinary Cirripedes, hermaphrodite, but the male organs are somewhat less developed than is usual ; and, as if in compensation, several short-lived males are almost invariably attached to the occludent margin of both scuta. . . . I have called these beings complemental males, to signify that they are complemental to an hermaphrodite, and that they do not pair like ordinary males with simple females." — (Darwin.) DIVISIONS OF ClRRIPEDIA. — (AFTER DARWIN.) ORDER I. THORACICA. Carapace, either a capitulum on a pedicle, or an operculated shell with a basis. Body, formed of six thoracic segments, generally furnished with six pairs of limbs ; abdomen rudimentary, but often bearing caudal appen- dages. Mouth, with labrum not capable of independent movements. Larva, firstly one-eyed, with three pairs of legs ; lastly two-eyed, with six pairs of legs. Fam. i. Balanida. Sessile, without a peduncle; scuta and terga (forming the oper- culum) provided with depressor muscles ; the rest of the valves immovably united together. Fam. 2. Verrucidce. Sessile. Shell asymmetrical, with scuta and terga, which are movable, but not furnished with a depressor muscle. Fam. 3. Lepadidce. Pedunculated. Peduncle flexible, provided with muscles. Scuta and terga, when present, not furnished with a depressor muscle. Other valves, when present, not united into a single immovable case. ORDER II. ABDOMINALIA. Carapace flask-shaped ; body formed of one cephalic, seven thoracic, 204 MANUAL OF ZOOLOGY. and three abdominal segments, the latter bearing three pairs of cirri, but the thoracic segments being without limbs. Mouth, with the labrum greatly produced, and capable of independent movements. Larva, firstly egg-shaped, without external limbs, or an eye ; lastly binocular, without thoracic limbs, but with abdominal appendages. Genus. Cryptophialus. ORDER III. APODA. Carapace, reduced to two separate threads, serving for attachment. Body consisting of one cephalic, seven thoracic, and three abdominal seg- ments, all destitute of cirri. Mouth suctorial. Genus. Proteolepas. CHAPTER XXXIII. SUB-CLASS ENTOMOSTRACA. SUB-CLASS III. ENTOMOSTRACA. — The term Entomostraca has been variously employed, an4 few authorities include exactly the same groups of the Crustacea under this name. By most the division is simply defined as including all those Crustacea in which the segments of the thorax and abdomen, taken together, are more or fewer than fourteen in number — the parasitic Epizoa and the Cirripedia being excluded. By Professor Rupert Jones the following definition of the Entomos- traca has been given : — "Animal aquatic, covered with a shell, or carapace, of a horny consistency, formed of one or more pieces, in some genera resembling a cuirass or buckler, and in others a bivalve shell, which completely or in great part envelops the body and limbs of the animal ; in other genera the animal is invested with a multivalve carapace, like jointed plate-armour ; the branchiae are attached either to the feet or to the organs of mastication ; the limbs are jointed, and more or less setiferous. The animals, for the most part, undergo a regular moulting or change of shell, as they grow ; in some cases this amounts to a species of transformation." The Entomostraca are divided into two great divisions, or " legions," the Lophyropoda and the Branchiopoda, with which the order Merostomata may be conveniently considered. DIVISION A. LOPHYROPODA. — The members of this division possess few branchiae, and these are attached to the appen- dages of the mouth. The feet are few in number, and mainly subserve locomotion ; the carapace is in the form either of a shield protecting the cephalothorax, or of a bivalve shell ANNULOSA: CRUSTACEA. 205 enclosing the entire body. The mouth is not suctorial, but is furnished with organs of mastication. This division comprises the two orders Ostracoda and Copepoda. ORDER I. OSTRACODA. — Small Crustaceans having the entire body enclosed in a shell or carapace, which is composed of two valves united along the back by a membrane. The branchiae are attached to the posterior jaws, and there are only two or three pairs of feet, which subserve locomotion, but are not adapted for swimming. The order includes the Cyprides (fig. 63, a), which are of almost universal occurrence .in fresh water. The common Cypris is completely protected from its enemies by a bivalve carapace, which it can open and shut at will, and out of which it can protrude its feet. Locomotion is mainly effected by means of a pair of caudal appendages. The Cypris is ex- tremely prolific, and a single impregnation appears to last the female for its entire lifetime. It appears, also, that the young females, produced in this way, are capable for some generations of producing fresh individuals without the influence of a male (parthenogenesis). Fig. 63. — Fresh-water Entomostraca. a Cypris tris-striat* ; b Daphnia pulex; c Cyclops quadricomis. ORDER II. COPEPODA. — Small Crustaceans, having the head and thorax covered by a carapace, and furnished with five pairs of natatory feet. Usually there are two caudal locomo- tive appendages. In the Cyclops (fig. 63, c) which is one of the commonest of the "Water-fleas," the cephalothorax is protected superiorly by a carapace, and the abdominal somites are conspicuous. In front of the head is situated a single large eye, behind which are the great antennae and the antennules. The feet are five 206 MANUAL OF ZOOLOGY. pairs in number, each consisting of a protopodite and a seg- mented exopodite and endopodite, usually furnished with hairs and forming an efficient swimming apparatus. The young pass through a metamorphosis, and are not capable of repro- ducing the species until after the third moult or change of skin. The female Cyclops carries externally two ovisacs, in which the ova remain till they are hatched. A single congress with the male is apparently sufficient to fertilise the female for life. The Copepodd) or Oar-footed Crustaceans, are all of small size, and are of common occurrence in fresh water in all parts of Europe. By Professor Huxley the Ichthyophthira are regarded as merely Copepoda peculiarly modified to suit a life of parasitism. DIVISION B. BRANCHIOPODA. — The Crustaceans included in this division have many branchiae, and these are attached to the legs, which are often numerous, and are formed for swimming. In other cases the legs themselves are flattened out so as to form branchiae. The body is either naked, or is protected by a carapace, which may enclose either the entire body, or the head and thorax only. The mouth is provided with organs of mastication. The Branchiopoda comprise the Cladocera, the Phyllopoda, and probably the Trilobita, though this order departs in many respects from the above definition. The Merostomata may be considered along with these, though these, too, are in many respects peculiar. ORDER I. CLADOCERA. — The members of this order are small Crustaceans, which have a distinct head, and have the whole of the remainder of the body enclosed within a bivalve carapace, similar to that of the Ostracoda. The feet are few in number (usually four or five pairs), and are mostly respira- tory, carrying the branchiae. Two pairs of antennae are present, the larger pair being of large size, branched, and acting as natatory organs. In the Daphnia pulex (fig. 63, b\ or "branched -horned Water-flea," which occurs commonly in our ponds, the body is enclosed in a bivalve shell, which is not furnished with a hinge posteriorly, and which opens anteriorly for the protrusion of the feet. The head is distinct, not enclosed in the cara- pace, and carrying a single eye. The mouth is situated on the under surface of the head, and is provided with two mandibles and a pair of maxillae. The gills are in the form of plates, attached to the five pairs of thoracic legs. The males are very few in number, compared with the females, and a single ANNULOSA: CRUSTACEA. 2O/ congress is all that is required to fertilise the female for life. Not only in this case, but the young females produced from the original fecundated female appear to be able to bring forth young without having access to a male. In this way the influ- ence of a single fecundation appears to be transmitted through several generations. ORDER II. PHYLLOPODA. — Crustacea, mostly of small size, the carapace protecting the head and thorax, or the body entirely naked. Feet numerous, never less than eight pairs, mostly foliaceous or leaf-like, branchial in function. The eyes sometimes confluent, sometimes distinct and sub-pedunculate. Fig. 64. — Phyllopoda. Fairy Shrimp (Chirocephalus diaphanus) — after Baird. The Phyllopoda are chiefly interesting from their affinity to the extinct Trilobites. In the typical genera Limnadia and Apus, the body is protected by a carapace which is bivalve in the former and shield-like in the latter. In Limnadia the carapace covers the greater part of the body, and opens along the ventral margin. There are from 18 to 30 pairs of mem- branaceous and respiratory feet. In Apus the carapace is clypeiform and covers a portion of the abdomen, and there are sixty pairs of feet, of which all but the first pair are foliaceous. In Branchipus, which occurs in many pools, the body is not protected by a carapace, and this is also the case with the singular little Artemia salina which inhabits the brine-pans at Lymington and elsewhere. ORDER III. TRILOBITA. — This order is entirely extinct, none of its members having survived the close of the Palaeozoic period. It is probable that the Trilobites should be placed near the Phyllopoda, but their exact position is uncertain, as no traces of any appendages of any kind, except the labrum, have hitherto been discovered in any Trilobite. The body of a Trilobite (fig. 65), was covered with a " crust," or exoskeleton, which shows more or less markedly a division into three longitudinal lobes, from the presence of which the name of the order is derived. The shell is composed of a cephalic shield, a certain number of free and movable thoracic 208 MANUAL OF ZOOLOGY. rings, and a caudal shield, or " pygidium," the rings of which are more or less completely anchylosed. On the under surface of the body nothing has hitherto been discovered, except the " hypostome," or " labrum," which was a plate placed in front of the mouth. No traces of ambulatory or natatory limbs, of branchiae, or of antennae, have ever been discovered. The eyes, when present, are compound, and usually sessile, but are sometimes supported upon projecting processes. It has generally been supposed that the body of the Trilobite occupied the median lobe of the crust, commencing with the " glabella " in front, and terminating with the " pygidium " behind ; whilst the axial lobes protected a series of delicate respiratory feet ; but this view is doubted by many authorities, and the question is one which we have at present no means of deciding. Quite recently, however, a specimen of a Trilobite has been discovered in which it is said that the bases of the legs were distinctly recognisable. The specimen in question was an Asaphus ; but the great number and excellent preservation of Trilobites, as a general rule, render it highly probable that in most cases the limbs were destitute of a chitinous exoskeleton, and were therefore incapable of being preserved in a fossil state. Fig. 65. — Morphology of Trilobites. i. Angelina Sedgwickii; 2. Diagram of the cephalic shield of a- Trilobite (after Salter). a Glabella; b b Free cheeks, bearing the eyes (p 0} ; c c Fixed cheek, including the eye-lobe (d~) ; e e Facial suture. The cephalic shield of a typical Trilobite is more or less completely semicircular (fig. 65, 2), and is composed of a central and of two lateral pieces, of which the two latter may, or may not, be united together in front of the former. The median portion is usually elevated above the remainder of the cephalic shield, and is called the "glabella;" it protected the region of the stomach, and is usually divided into from three to four lobes by lateral grooves. At each side of the glabella, and continuous with it, is a small semicircular area, called the "fixed cheek." The glabella, with the "fixed cheeks," is separated from the lateral portions of the cephalic shield — termed the "movable," or "free cheeks,"— by a peculiar suture or line ANNULOSA: CRUSTACEA. 209 of division, which is known as the "facial suture," and is quite unknown amongst recent Crustacea, except for a faint indication in the Limulus, and more or less doubtful traces in certain other forms. The movable cheeks bear the eyes, which are generally crescentic or reniform in shape, are rarely pedunculated, and consist of an aggregation of facets covered by a thin cornea. The facial sutures may join one another in front of the glabella — in which case the free cheeks will form a single piece — or they may cut the anterior margin of the shield separately — in which case the free cheeks will be discontinuous. The posterior angles of the free cheeks are often produced into long spines. Behind the cephalic shield comes the thorax, composed of a variable number of segments, which are not soldered together, but are capable of free motion upon one another, so as to allow the animal to roll itself up after the manner of a wood-louse, or hedgehog. The thorax is usually strongly trilobed, and each thorax-ring shows the same trilobation, being composed of a central, more or less strongly convex, portion, called the "axis," and of two flatter side-lobes, called the "pleurae." The " pygidium," or "tail," is usually trilobed also, and, like the thorax, consists of a median axis and of a marginal limb, the composition of the whole out of anchylosed segments being shown by the existence of axial and pleural grooves. ORDER IV. MEROSTOMATA. — The members of this order are Crustacea, often of gigantic size, in which the mouth is fur- nished with mandibles and maxillae, the terminations of which become walking or swimming feet, and organs of prehension. This order comprises the recent King Crabs, and the extinct Pterygoti and Eurypteri. SUB-ORDER i. XIPHOSURA (Pczcilopoda). — " Crustacea having the anterior segments welded together to form a broad convex buckler, upon the dorsal surface of which are placed the com- pound eyes and ocelli ; the former sub-centrally, the latter in the centre in front. The mouth is furnished with a small labrum, a rudimentary metastoma and six pairs of appendages. Posterior segments of the body more or less free, and bearing upon their ventral surfaces a series of broad lamellar appen- dages; the telson, or terminal segment, ensiform." — (Henry Woodward. ) The Xiphosura include no other recent forms than the Limuli (King Crabs, or Molucca Crabs) (fig. 66). They are distinguished by the possession of six pairs of chelate limbs, placed round the mouth, having their bases spinous and officiating as jaws. Six other pairs of foliaceous appendages are attached to the abdomen, and the last five of these carry branchiae. The body, which is often of great size, when viewed from above exhibits a division into three portions : — (i) An an- terior semicircular shield, which carries two compound and two simple eyes ; (2) a posterior, irregularly hexagonal shield, which covers the abdomen ; and (3) a long, sword-like telson, VOL. i. o 210 MANUAL OF ZOOLOGY. articulated to the dorsal buckler, and giving the name to the sub-order. The chief features, therefore, which characterise the Limulus are as follows : — i. The possession of six pairs of appendages which are placed round the mouth, have their bases spinous, act as jaws, and have their free extremities developed into claws; 2. The possession of six abdominal pairs of appendages, expanded for swimming, and carrying the gills ; 3. The posses- sion of a semicircular buckler, covering the cephalothorax, and Fig. 66. — Xiphosura. Limulus polypke- mus, viewed from below, c The cephalic shield carrying the sessile eyes upon its upper surface ; o "Operculum," covering the reproductive organs ; b Branchial plates ; a First pair of antennae (anten- nules) ending in chelae. Below these is the aperture of the mouth surrounded by the spiny bases of the remaining five pairs of appendages, which are regarded t>y Woodward as being respectively, from before backwards, the great antennae, the mandibles, the first maxillae, the second maxillae, and a pair of maxillipedes. All have their extremities chelate. Fig. 67. — Eurypterida. Pterygotus An- glicus, restored (after H. Woodward). c c Chelate antennae ; o o Eyes, situated at the anterior margin of the carapace ; m m The mandibles, and first and se- cond maxillae ; n n The maxillipedes ; the basal margins of these are serrated, and are drawn as if seen through the me- tastoma or post-oral plate, which serves as a lower lip. Immediately behind this is seen the operculum or thoracic plate which covers the two anterior thoracic somites. Behind this are five thoracic and five abdominal somites, and lastly there is the telson (f). carrying the eyes upon its upper surface; 4. The possession of a second buckler, or " operculum," covering the abdomen ; ANNULOSA : CRUSTACEA. 21 1 5. The presence of a long, sword-shaped telson, or tail-spine, articulated to the dorsal shield. The larval Limulus does not possess the ensiform post-anal spine of the adult SUB-ORDER 2. EURYPTERIDA. — " Crustacea with numerous, free, thoracico-abdominal segments, the first and second (?) of which bear one or more broad lamellar appendages upon their ventral surface, the remaining segments being devoid of appen- dages; anterior rings united into a carapace, bearing a pair of larval eyes (ocelli] near the centre, and a pair of large, mar- ginal, or sub-central eyes ; the mouth furnished with a broad post-oral plate, or metastoma, and five pairs of movable appen- dages, the posterior of which form great swimming feet ; the telson, or terminal segment, extremely variable in form ; the integument characteristically sculptured." — (Henry Wood- ward.) The Eurypterida are all extinct, and are entirely confined to the Palaeozoic period. Many of them attained to a compara- tively gigantic size; Pterygotus Anglicus (fig. 67) being sup- posed to have reached a length of probably six feet. In their characters they present many larval features ; resembling the larvae of the Decapoda especially in the fact that all the free somites of the abdomen (except the two anterior ones) were totally devoid of appendages. CHAPTER XXXIV. MALA COSTRA CA. SUB-CLASS IV. MALACOSTRACA.— The Crustacea of this sub- class are distinguished by the possession of a generally definite number of body-segments ; seven somites going to make up the thorax, and an equal number entering into the composition of the abdomen (counting, that is, the telson as a somite). The Malacostraca are divided into two primary divisions, termed respectively the Edriophthalmata and the Podophthalmata ac- cording as the eyes are sessile, or are supported upon eye-stalks. DIVISION A. EDRIOPHTHALMATA. — This division comprises those Malacostraca in which the eyes are sessile, and the body is not protected by a carapace. It comprises the three orders, Lamodipoda, Isopoda, and Amphipoda. ORDER I. L^EMODIPODA. — The Lczmodipoda are small Cms- 212 MANUAL OF ZOOLOGY. Fig. 68. — Lsemodipoda. Caprella phasma. taceans, which are distinguished amongst the Edriophthalmata by the rudimentary condition of the abdomen. The first thoracic segment is amal- gamated with the head, and the limbs of this seg- ment appear to be inserted beneath the head, or, as it were, beneath the throat (fig. 68) ; hence the name given to the order. The respiratory organs are in the form of two or three pairs of membranous vesicles attached to the segments of the thorax, or to the bases of the legs. The L&modipoda do not swim, and one section of the order com- prises parasitic Crustaceans, of which the Whale-louse ( Cyamus Ceti) is the most familiar. ORDER II. AMPHIPODA. — The members of this order resemble those of the preceding in the nature of the respiratory organs, which consist of membranous vesicles attached to the bases of the thoracic limbs. The first thoracic segment, however, is dis- tinct from the head, and the abdomen is well developed, and is composed of seven segments. There are seven pairs of thoracic limbs, directed partly forwards, and partly backwards, the name of the order being derived from this circumstance. Fig. 69. — Amphipoda. The Sand-hopper, Talitrus Zocusta, enlarged. All the Amphipoda are small, the " Sand-hopper" (Talitms locusta, fig. 69) and the "fresh-water Shrimp" (Gammarus pulex] being two of the commonest forms. ORDER III. ISOPODA. — In this order the head is always dis- tinct from the segment bearing the first pair of feet. The respiratory organs are not thoracic, as in the two preceding orders, but are attached to the inferior surface of the abdomen, ANNULOSA: CRUSTACEA. 213 and consist of branchiae, which in the terrestrial species are protected by plates which fold over them. The thorax is com- posed of seven segments, bearing seven pairs of limbs, which, in the females, have marginal plates, attached to their bases, and serving to protect the ova. The num- ber of segments in the ab- domen varies, but is never more than seven. The eyes are two in number, formed of a collection of simple eyes, or sometimes truly compound. Of the mem- bers of this order, many are aquatic in their habits, and are often parasitic, but others are terrestrial. By Milne - Edwards the Isopoda are divided into three sections, termed re- spectively from their habits, the Natatorial, Sedentary, Fig. 70.— Isopoda. Wood-lice (Oniscus. ) and Cursorial Isopods. In the Natatorial Isopoda the ex- tremity of the abdomen and the last pair of abdominal legs are expanded so as to form a swimming tail. Some of this section are parasitic upon various fishes ( Cymothoa), whilst others are found in the sea (Sphceroma). In the Sedentary Isopoda the animals are all parasitic, with short, incurved, hooked feet. This section includes the single family of the Bopyridce, all the species of which live parasitically either in the gill-chambers, or attached to the ventral surface, of certain of the Decapod Crustacea, such as the Shrimps ( Crangones) and the Palcemones. The Cursorial, or running, Isopods mostly live upon the land, and are, therefore, destitute of swimming feet. The most familiar examples of this section are the common Wood-lice (Oniscus]. Here, also, belongs the little Limnoria terebrans, so well known for the destruction which it produces by boring into the wood-work of piers and other structures placed in the sea. DIVISION B. PODOPHTHALMATA. — The members of this divi- sion have compound eyes supported upon movable stalks or peduncles, and the body is always protected by a cephalotho- racic carapace. It comprises the two orders Stomapoda and 214 MANUAL OF ZOOLOGY. Decapoda, of which the latter includes all the highest and most familiar examples of the class Crustacea. ORDER I. STOMAPODA. — In this order there are generally from six to eight pairs of legs, and the branchiae, when present, are not enclosed in a cavity beneath the thorax, but are either suspended beneath the abdomen, or, more rarely, are attached to the thoracic legs. The shell, also, is thin, and often mem- branous. From all the preceding orders the Stomapoda are, of course, distinguished by the possession of pedunculate eyes. All the Stomapods are marine, and Squilla mantis may be taken as a good example of the order. In this Crustacean the carapace is small, and the posterior half of the thorax is un- protected. Several of the anterior appendages are developed into powerfully prehensile and hooked feet. The branchiae are attached to the first five pairs of abdominal feet. The three posterior thoracic and the abdominal appendages are in the form of " swimmerets," and the tail is expanded into a powerful fin. ORDER II. DECAPODA. — The members of this order are the most highly organised of all the Crustacea, as well as being those which are most familiarly known, the Lobsters, Crabs, Shrimps, &c., being comprised under this head. For the most part they are aquatic in their habits, and they are usually pro- tected by strong,, resisting shells. There is always a complicated set of " gnathites/' or appendages modified for masticatory pur- poses, surrounding the mouth. The ambulatory feet are made up of five pairs of legs (hence the name of the order), the first pair — and often some other pairs behind this — being " chelate," or having their extremities developed into nipping claws. The branchiae are pyramidal, and are contained in cavities at the sides of the thorax. The carapace is large, covering the head and thorax, and the anterior part of the abdomen. The Decapoda are divided into three tribes, tenned respec- tively the Macrura, Anomura and Brachyura, and characterised by the nature of the abdomen. TRIBE A. MACRURA. — The " long-tailed " Decapods included in this tribe are distinguished by the possession of a well* developed abdomen, often longer than the cephalothorax, the posterior extremity of which forms a powerful natatory organ or caudal fin. This section comprises the Lobster, Cray-fish, Shrimp, Prawn, &c., of which the Lobster may be taken as the type. In the Lobster (fig. 71) the somites of the head and thorax are amalgamated into a single mass, the "cephalothorax," covered by a carapace or shield, which is developed from " the lateral or epimeral elements of the fourth cephalic ring, which ANNULOSA : CRUSTACEA. 215 meet along the back, and give way preparatory to the moult. The tergal elements of the thoracic rings are not developed in either Crabs or Lobsters ; when these rings are exposed by lifting up the cephalothoracic shield, the epimeral parts alone are seen, converging obliquely towards one another, but not joined at their apices." — (Owen.) Fig. 71. — Macrura. Common Lobster (Homarus vulgaris). i. First pair of legs, constituting the great chelae or nipping claws ; 2. Second pair of legs, also chelate ; 3. Third pair of legs, also chelate ; 4 and 5. Last two pairs of ambulatory legs, with simply pointed extremities ; a. Antennules ; go. Great antennas ; ca. Carapace. The first segment of the head bears the compound eyes, which are supported upon long and movable eye-stalks or peduncles. Behind these come two pairs of jointed tactile 2l6 MANUAL OF ZOOLOGY. organs, the larger called the "great antennae" (fig. 71, ga), the smaller the " antennules " (a). The mouth is situated on the under surface of the front of the head, and is provided from before backwards with an upper lip (" labrum "), two " mandi- bles," two pairs of " maxillae," three pairs of " maxillipedes " or "foot-jaws," and a bifid lower lip, or "metastoma." The five remaining segments of the thorax carry the five pairs of ambulatory legs, of which the first (fig. 71, i) constitute the great claws, or " chelae ; " the next two pairs (2 and 3) are also che- late, though much smaller; and the last two pairs are terminated by simply pointed extremities. The segments of the abdomen carry each a pair of natatory limbs, or " swimmerets," the last pair being greatly expanded, and constituting, with the " tel- son," a powerful caudal fin. Most posteriorly of all is the post-anal plate, or " telson," which may be looked upon either as an azygos appendage, or as a terminal segment which has no lateral appendages. The mouth leads by a short oesophagus into a globose stomach, in the cardiac portion of which is a calcareous appa ratus for triturating the food, which is commonly called the "lady in the lobster." The intestine is continued backwards from the stomach without convolutions, and the anal aperture is situated just in front of the telson. There is, also, a well- developed liver, consisting of two lobes which open by separate ducts into the intestine. The heart is situated dorsally, and consists of a single poly- gonal contractile sac, which opens by valvular apertures into a surrounding venous sinus, inappropriately called the " peri- cardium." The heart is filled with oxygenated blood derived from the gills, and propels the aerated blood through every part of the body. The gills (fig. 59, 3,^) are pyramidal bodies attached to the bases of the legs, and protected by the sides of the carapace. They consist each of a central stem sup- porting numerous laminae, and they are richly supplied with blood, but are not ciliated. The water which occupies the gill-chambers is renovated partly by the movements of the legs, and partly by the expanded epipodite of the second pair of maxillae, which constantly spoons out the water from the front of the branchial chamber, and thus causes an entry of fresh water by the posterior aperture of the cavity. The nervous system is of the normal " homogangliate " type, consisting of a longitudinal series of ganglia of different sizes, united by commissural cords, and placed along the ventral surface of the body. The organs of sense consist of the two compound eyes, the two pairs of antennae, and two auditory sacs. ANNULOSA: CRUSTACEA. 217 The sexes are invariably distinct, and the generative pro- ducts are conveyed to the exterior by efferent ducts, which open at the base of one of the pairs of thoracic legs. The ovum is " meroblastic," a portion only of the vitellus under- going segmentation. The neural side of the body, that is to say, the ventral surface, appears on the surface of the ovum, so that the embryo is built up from below, and the umbilicus is situated posteriorly. TRIBE B. ANOMURA. — The Decapods which belong to this tribe are distinguished by the condition of the abdomen, which is neither so well developed as in the Macntra, nor so rudi- mentary as in Crabs. Further, the abdomen does not termi- nate posteriorly in a caudal fin, as in the Lobster. The most familiar of the Anomura are the Hermit-crabs (Pagurida). In the common Hermit-crab (Pagurus Bernhar- dus) the abdomen is quite soft, and is merely enclosed in a membrane, so that the animal is compelled to protect itself by adopting the empty shell of some Mollusc, such as the common Whelk, which it changes at will, when too small. The Hermit is provided with a terminal caudal sucker, and with two or three pairs of rudimentary feet developed upon the abdomen, by means of which he retains his position within his borrowed dwelling. The carapace is not strong, but the claws are well developed, one being always larger than the other. TRIBE C. BRACHYURA. — The " short-tailed " Decapods, or Crabs, are distinguished from the two preceding tribes by the rudimentary condition of the abdomen, which is very short, and is tucked up beneath the cephalothorax, the latter being disproportionately large. The extremity of the abdomen is not provided with any appendage, and it is merely employed by the female to carry the ova. The Crabs (fig. 72) are mostly furnished with ambulatory limbs, and are not formed for swimming, most of them being littoral in their habits, and some few even living inland. In all the essential points of their anatomy the Crabs do not differ from the Lobster and the other Macrura j but they are decidedly higher in their organisation. This is especially seen in the disposition of the nervous system, the ventral ganglia in the Crab being concentrated into a single large ganglion, from which nervous filaments are sent to all parts of the body. Reproduction in the Crabs is the same as in the Macrura^ but the larva is exceedingly unlike the adult, and approximates closely to the type of the Macrura, another proof that the Brachyura stand higher in the Crustacean scale. The larval Crab was originally described as a distinct animal, under the 2l8 MANUAL OF ZOOLOGY. name of Zoea (fig. 73), presenting in this condition a long and Fig. 72.— Brachyura. The Spiny Spider- Crab (Maia squinadd). well-developed abdomen. It is only after several successive moults that the young Crab assumes its characteristic Brachy- Fig. 73. — Larva (Zoea) of Crab (Pirimela denticulate?), magnified — after Kinahan. urous form, and acquires by gradual changes the features which distinguish the adult. ANNULOSA: CRUSTACEA. 2IQ CHAPTER XXXV. DISTRIBUTION OF THE CRUSTACEA. DISTRIBUTION OF CRUSTACEA IN SPACE. — The following gene- ral principles have been laid down by Milne-Edwards with regard to the geographical distribution of the Crustacea : — 1. The different forms and modes of organisation of the Crustacea are more varied and numerous, in proportion as we pass from the polar regions towards the equator. 2. The number of different species is not only greater, but the number of types is greater in warm regions as compared with cold. 3. The higher Crustacea are either entirely wanting or are sparingly represented in the colder regions of the globe, but increase rapidly in relative numbers as the equator is ap- proached. 4. The size attained by the Crustacea is greater on the aver- age in warm regions than in colder climates. 5. The special points of structure which are characteristic of the different groups of Crustacea are more strongly mani- fested in the warmer regions of the globe. 6. There exists a decided relation between the temperature of any given region and the character of its Crustacean fauna; similar generic forms being usually found occupying regions of the same climatal character. DISTRIBUTION OF CRUSTACEA IN TIME. — The class Crustacea is largely represented in past time, ranging from the Cambrian Rocks up to the present day. The oldest families of the Crus- tacea are the Trtlobita and the Eurypterida, both of which are exclusively Palaeozoic, and died out at the close of the Car- boniferous epoch. It is worthy of notice how larval are the characters of these ancient groups when compared with their modern successors. Of the remaining orders the Cirripedia, Ostracoda, and Phyllopoda are the three which are most largely represented. i. Cirripedia. — The Cirripedes are hardly known as Palaeo- zoic fossils, but valves of a singular member of this order (2ur- rilepas] have been found in the Silurian Rocks of Scotland. With this exception, the Cirripedes are entirely confined in past time to the Secondary and Tertiary epochs. The Bala- nidce are the most common, commencing, as far as is yet known, in the Eocene period, and attaining their maximum in recent seas. The Verrucidcs, commence in the Chalk, and the 220 MANUAL OF ZOOLOGY. Lepadidce begin still lower, in the Jurassic Rocks, and attain their maximum of development in the Cretaceous epoch. 2. Ostracoda. — Small Ostracode Crustacea are extremely abundant as fossils in many formations, and extend from the Lower Silurian period up to the present day. 3. Phyllopoda. — Remains of Crustaceans supposed to belong to this order are found in the Palaeozoic Rocks. Hymenocaris is found in the Upper Cambrian, Caryocaris in the Lower Silurian, Ceratiocaris in the Upper Silurian, and Dithyrocaris in the Carboniferous Limestone. All these forms, with other similar ones, are believed to be most closely allied to the recent Apus and Nebalia. 4. Trilobita. — The Trilobites are exclusively Palaeozoic fos- sils. In the Upper Cambrian Rocks — the so-called " primor- dial zone " — there occurs a singular group of Trilobites — the so-called primordial Trilobites — distinguished by the posses- sion of many larval characters. In the Lower and Upper Silurian Rocks the Trilobites attain their maximum of devel- opment. They are still well represented in the Devonian Rocks ; but they die out completely before the close of the Carboniferous epoch, being represented in the Mountain Lime- stone by three genera only (Phillipsia^ Br achy met opus, and Griffithides). 5. Eurypterida. — These, like the last, are entirely Palaeozoic, attaining their maximum in the Upper Silurian and Devonian formations, and dying out in the Carboniferous Rocks. Ptery- gotus,Eurypterus,a.t\&Slimoniaa.rQ the most characteristic genera. 6. Xiphosura. — The genus Limulus commenced, as far as is yet known, in the Permian period, and has survived up to the present day. Its first appearance, therefore, was just at the close of the Palaeozoic epoch. The two remaining genera, which constitute with Limulus this sub-order (viz., Belinurus and Prestwichia\ are Palaeozoic, and are not known to occur out of the Carboniferous Rocks. 7. Isopoda. — The earliest known Isopod is the Prosoponiscus of the Permian Rocks. 8. Stomapoda. — This order is doubtfully represented in the Carboniferous Rocks. 9. Decapoda. — The Decapods, with the exception of a single doubtful form from the Carboniferous Rocks, are not known to have existed at all during the Palaeozoic period ; but they are well represented, in all their three tribes, in the Secondary and Tertiary epochs, attaining their maximum at the present day. The London Clay (Eocene) is especially rich in the remains of Macrura and Brachyura. AXXULOSA: ARACHNIDA. 221 i CHAPTER XXXVI. ARACHNIDA. CLASS II. ARACHNIDA. — The Arachnida — including the Spi- ders, Scorpions, Mites, &c. — possess almost all the essential characters of the Crustacea, to which they are very closely allied. Thus, the body is divided into a variable number of somites, some of which are always provided with articulated appendages. A pair of ganglia is primitively developed in each somite, and the neural system is placed ventrally. The heart, when present, is always situated on the opposite side of the alimentary canal to the chain of ganglia. The respiratory organs, however, whenever these are differentiated, are never in the form of branchiae as in the Crustacea, but are in the form either of pulmonary vesicles or sacs, or of ramified tubes, formed by an involution of the integument, and fitted for breathing air directly. Further, there are never " more than four pairs of locomotive limbs, and the somites of the abdomen, even when these are well developed, are never provided with limbs;" the reverse being the case amongst the Crustacea. Lastly, " in the higher Arachnida, as in the higher Crustacea, the body is composed of twenty somites, six of which are al- lotted to the head ; but, in the former class, one of the two normal pairs of antennae is never developed, and the eyes are always sessile ; while, in the higher Crustacea, the eyes are mounted upon movable peduncles, and both pairs of antennae are developed." — (Huxley.) The head in the Arachnida is always amalgamated with the thorax, to form a " cephalothorax ; " the integument is usually chitinous, and the locomotive limbs are mostly similar in form to those of insects, and are usually terminated by two hooks. In many of the Arachnida the integument remains soft over the entire body ; in others, as in the majority of Spiders, the abdomen remains soft and flexible, whilst the cephalothorax is more or less hard and chitinous ; in the Scorpions, again, the integument over the whole body forms a strong chitinous shelL The typical somite of the Arachnida is constituted upon exactly the same plan as that of the Crustacea, consisting essentially of a dorsal and ventral arc ; the former composed of a central piece, or "tergum," and of two lateral pieces, or " epimera ; " whilst the latter is made up of a median " ster- num " and of two lateral " episterna." As regards the composition of the cephalothorax of Spiders, 222 MANUAL OF ZOOLOGY. " the tergal elements of the coalesced segments are wanting, and the back of the thorax is protected by the elongation, con- vergence, and central confluence of the epimeral pieces ; the sternal elements have coalesced into the broad plate in the centre of the origins of the ambulatory legs, from which it is separated by the episternal elements The non-devel- opment of the tergal elements explains the absence of wings." —(Owen.) The mouth is situated, in all the Arachnida, in the anterior segment of the body, and is surrounded by suctorial or masti- catory appendages. In the higher Arachnida the mouth is provided from before backwards with the following appendages (fig. 74, 4). i. A pair of "mandibles," used for prehension. 2. A pair of " maxillae," each of which is provided with a long jointed appendage, the " maxillary palp." 3. A lower lip, or " labium." In the Scorpion an upper lip, or " labrum," is also present. In the Spiders (fig. 74, 4) each mandible terminates in a sharp movable hook, which possesses an aperture at its extremity communicating by a canal with a gland, which is placed in the preceding joint of the mandible, and secretes a poisonous fluid. The maxillary palps in the Spiders are long, jointed appendages, terminated in the females by pointed claws, but frequently swollen, and carrying a special sexual apparatus in the males. In the Scorpions (fig. 74, i) the mandibles are short, and terminate in strong pincers, or " chelicerse." The maxillary palpi are also greatly developed, and constitute powerful grasping claws, or " chelae." In the genus Galeodes, the man- dibles, like those of the Scorpion, constitute " chelicerae," though comparatively much larger and longer ; but the maxil- lary palps are not developed into " chelae." With regard to antennae, these organs, as such, do not exist in the Arachnida. It is generally believed, however, that the mandibles of the Arachnida are truly homologues, not of the parts which bear the same name in the other Arthropoda, but of the antenna. The antennae, therefore, of the Spiders, are converted into prehensile and offensive weapons ; whilst in the Scorpions, as in the King Crabs, they are developed into nip- ping claws, or chelae. In the lower Arachnida, the organs of the mouth, though essentially the same as in the higher forms, are enveloped in a sheath, formed by the labium and maxillae, whilst the man- dibles are often joined together so as to constitute a species of lancet. ANNULOSA: ARACHNIDA. 223 The mouth opens into a pharynx, which is of remarkably small calibre in the true spiders, all of which live simply on the juices of their prey. The intestinal canal is usually short — \ 4 Fig. 74.— Morphology of Arachnida. i. Organs of the mouth in the Scorpion, on one side ; m Mandibles (antennae) converted into chelae, and called the chelicerae ; p Maxillary palpi greatly developed, and forming strong chelae. 2. Telson of the Scorpion. 3. One of the abdominal segments of the Scorpion, showing the "stig- mata," or apertures of the pulmonary sacs. 4. Tegenaria domestica, the common Spider (male), viewed from below ; ^ Spinnerets ; m Mandibles with their perforated hooks — below the mandibles are the maxillae, and between the bases of these is the labium ; / The maxillary palpi with their enlarged tumid extremities. and straight, no convolutions intervening between the mouth and the aperture of the anus. Often, however, lateral caeca are appended to the alimentary tube. Salivary glands are also present, as well as ramified tubes, supposed to perform the functions of a kidney, and to correspond to the " Malpighian vessels" of Insects. The circulation in the Arachnida is maintained by a dorsal heart, which is situated above the alimentary canal. Usually the heart is greatly elongated, and resembles the " dorsal vessel " of the Insecta. In the lower Arachnida, however, there is no central organ of the circulation, and there are no differ- entiated blood-vessels. All the Arachnida breathe the air directly, and the respiratory function is performed by the general surface of the body (as in the lowest members of the class), or by ramified air-tubes, termed "tracheae," or by dis- tinct pulmonary chambers or sacs ; or, lastly, by a combination of tracheae and pulmonary vesicles. The " tracheae " consist of ramified or fasciculated tubes, opening upon the surface of the 224 MANUAL OF ZOOLOGY. body by distinct apertures, called " stigmata," and usually branch- ing freely as they penetrate the tissues internally. The walls of the tube are generally prevented from collapsing by means of a chitinous fibre or filament, which is coiled up into a spiral, and is situated beneath their epithelial lining. The pulmonary sacs are simple involutions of the integument, abundantly sup- plied with blood ; the vascular surface thus formed being in- creased in area by the development of a number of close-set membranous lamellae, or vascular plates, which project into the interior of the cavity. Like the tracheae, the pulmonary sacs communicate with the exterior by minute apertures, or "stigmata" (fig. 74, 3). The nervous system is of the normal articulate type, but is often much concentrated. In the Spiders there is a cephalic, or " cerebral," ganglion, a large thoracic ganglion, and in some instances a small abdominal ganglion. In some of the lower forms the articulate type of nervous system is lost, and there is merely a ganglionic mass which is traversed by the gullet. In none of the Arachnida are compound eyes present, and in none are the eyes supported upon foot-stalks. The organs of vision, when present, are in the form of from two to eight simple eyes, or " ocelli." In all the Arachnida, with the exception of the Tardigrada, the sexes are distinct. The great majority of the Arachnida are oviparous, and in most cases the larvae are like the adult in all except in size. In some cases, however (Acarina) the larvas have only six legs, and do not attain the proper four pairs of legs until after some moults. The Arachnida may be divided into two great sections or sub-classes—viz., the Trachearia, in which respiration is effected by the general surface of the body, or by tracheae, and there are never more than four ocelli ; and the Pulmonaria, in which respiration is effected by pulmonary sacs, either alone or com- bined with tracheae, and there are six or more eyes. CHAPTER XXXVII. DIVISIONS OF THE ARACHNIDA. DIVISION A. TRACHEARIA. — Respiration cutaneous, or by trachea. Eyes never more than four in number. The Trachearia comprise three orders — viz., the Podosomata, the Acarina, or Monomerosomata, and the Adelarthrosomata. ANNULOSA: ARACHNIDA. 225 ORDER I. PODOSOMATA (Pantopoda). — The members of this order, sometimes called " Sea-spiders," have been placed alter- nately amongst the Arachnida and the Crustacea, their true position being rendered doubtful by the fact that, though marine in their habits, they possess no differentiated respira- tory organs. They possess, however, no more than four pairs of legs, and would therefore appear to be properly referable to the Arachnida. The commoner forms of the Podosomata (such as Nymphon and Pycnogomtm) may be found on the sea- coast at low water, crawling about amongst marine plants or hiding beneath stones. Some species of the latter genus are asserted to be parasitic upon fishes and other marine animals, but the common British species (P. littorale] is free when adult, and does not appear to be parasitic at any stage of its existence (fig. 75, a). The legs consist of four pairs, some- times greatly exceeding the body in length, and sometimes containing caecal prolongations of the digestive cavity for a portion of their length. The mouth is provided with a pair of " chelicerae," or chelate mandibles, and with two well-developed maxillary palpi, behind which in the female are a pair of false legs which carry the ova. The abdomen is rudimentary. Though there are no respiratory organs, there is a distinct heart. The sexes are in different individuals. ORDER II. ACARINA or MONOMEROSOMATA. — The members of this order possess an unsegmented abdomen which is fused with the cephalothorax into a single mass. Respiration is effected by tracheae. Most of the Acarina are parasitic, and the most familiar are the Mites and Ticks. Family i. Linguatulina or Pentastomida. — The members of this family are singular vermiform animals, found as parasites in the frontal sinuses and lungs of some Vertebrates. In their adult condition they possess no external organs except two pairs of hooks, representing limbs, placed near the mouth. They thus closely approximate to the Taniada, beside which they have been generally placed. In the young condition, however, they possess four articulated legs, and even in the adult state the characters of the nervous system are higher than those of the Scolecida. There are no differentiated organs of respiration, and there are no circulatory organs, but the sexes are distinct. Family 2. Macrobiotidcz (Tardigrada or Arctisca). — The " Sloth" or "Bear animalcules," which compose this family, are microscopic animals, very much like Rotifers, found in damp moss and in the gutters of houses. The nervous system consists of four ganglia, and there is a suctorial mouth, with VOL. i. p 226 MANUAL OF ZOOLOGY. rudimentary jaws or stilets. The abdomen is undeveloped, and there are four pairs of rudimentary legs. They exhibit no traces of either circulatory or respiratory organs, and the sexes are united in the same individual. Family 3. Acarida. — This family includes the Mites, Ticks, and Water-mites, some of which are parasitic, whilst others are free, and some are even aquatic in their habits. The mouth is formed for suction. There is no definite line of demarcation between the unsegmented abdomen and the cephalothorax. In the true Acari (fig. 75, b\ of which the Cheese-mite may be taken as an example, there are four pairs of legs, adapted for walking. In the Sarcoptes scabiei — the cause of the skin- disease known as the " itch " — the two anterior pairs of legs are provided with suckers, and the two posterior are terminated by bristles ; the mouth, also, is furnished with bristles. In the Ticks (Ixodes] the mouth is provided with a beak, or " rostrum," which enables them to pierce the skin, and retain their hold firmly. In the Hydrachnida (fig. 75, c], or Water-mites, the Fig. 75. — Arachnida. a Pycnogonum littorale ; b Tetranychus telarius, one of the " Sociable" mites ; c Hydrachna globulus, one of the " Water-mites." head is furnished with two or four ocelli, and there are four pairs of hairy natatory legs. They are parasitic, during at least a portion of their existence, upon Water-beetles and other aquatic insects. They pass through a metamorphosis, the larva being hexapod, or having only three pairs of legs. Another member of the Acarina is the curious little Demodex folliculorum, which is found in the sebaceous follicles of man, especially in the neighbourhood of the nose. It is probable that very few, if any, individuals are exempt from this harm- less parasite. ORDER III. ADELARTHROSOMATA. — The members of this order, comprising the Harvest-spiders, the Book-scorpions, &c., are distinguished from the preceding by the possession of an ANNULOSA: ARACHNIDA. 22? abdomen, which is more or less distinctly segmented, but generally exhibits no line of separation from the cephalothorax, the two regions being of equal breadth and conjoined together. The mouth is furnished with masticatory appendages, and respiration is effected by tracheae, which open on the lower surface of the body by two or four stigmata. Family i. Phalangidce. — The well known "Harvest-spiders" belong to this family. They are characterised by the great length of the legs, and by the filiform maxillary palpi, termi- nated by simple hooks. Family 2. Pseudoscorpionidcz (Cheliferida>). — The "Book- scorpion " ( Chelifer) is a common little animal in old books. It is distinguished by the fact that the maxillary palpi are of large size, and are converted into nipping claws, or chelae, thus giving the animal the appearance of a Scorpion in miniature. Family 3. Solpugufa. — In this family the abdomen is not only very distinctly segmented, but is also clearly separated from the abdomen. The mandibles in Galeodes, which is the type of the group, are chelate, but the maxillary palpi consti- tute long feet. DIVISION B. PULMONARIA. — Respiration by pulmonary sacs alone, or by pulmonary sacs conjoined with trachetz. Eyes six or more in number. Abdomen usually distinct from the cepha- lothorax. This division comprises the higher Arachnida, such as the Scorpions, and the majority of what are commonly known as Spiders; the former constituting the order of the Pedipalpi, the latter that of the Araneida or Dimerosomata. ORDER I. PEDIPALPI. — In this order are the true Scorpions, together with certain other animals which are in some respects intermediate between the Scorpions and the true Spiders. The members of this order are distinguished by the fact that the abdomen in all is distinctly segmented, but is not separated from the cephalothorax by a well-marked constriction. They agree in this character with the Adelarthrosomata ; hence the two are sometimes united into a single order (Arthrogastrd), but they are separated by the nature of the respiratory organs, the latter breathing by tracheae, and not by pulmonary sacs. Family i. Scorpionidcz. — The Scorpions are amongst the best known of the Arachnida, as well as being amongst the largest. They are distinguished by their long, distinctly segmented ab- domen, terminating in a hooked claw (figs. 74, 76). This claw, which is really a modified "telson," is the chief offensive weapon of the Scorpion, and is perforated at its point by the duct of a poison-gland which is situated at its base. The abdomen is 228 MANUAL OF ZOOLOGY. composed of twelve somites, but there is no evident line of de- marcation between this region and the cephalothorax. The thoracic segments carry four pairs of ambulatory feet. The Fig. 76. — Scorpion (reduced). maxillary palpi are greatly developed, and constitute strong nipping claws, or "chelae" (figs. 74, 76). The mandibles (an- tennae) also form claws, or "chelicerae." The respiratory organs are in the form of pulmonary sacs, four on each side, opening upon the under surface of the abdomen by as many stigmata, each of which is surrounded by a raised margin, or " peritrema" (fig. 74, 3). The Scorpions are mostly inhabitants of warm regions, and their sting, though much exaggerated, is of a very severe nature. Family 2. Thelyphonida . — The members of this family in external appearance closely resemble the true Spiders, from which they are separated by the possession of a segmented abdomen and long, spinose palpi, and by the absence of spin- nerets. They are distinguished from the Scorpionida by the amalgamation of the head and thorax into a single mass, which is clearly separated from the abdomen by a slight constriction, as well as by the fact that the maxillary palpi terminate in movable claws instead of chelae. Further, the extremity of the abdomen is not furnished with a terminal hook, or "sting." ORDER II. ARANEIDA or DIMEROSOMATA. — This order includes the true Spiders, which are characterised by the amal- gamation of the cephalic and thoracic segments into a single mass, and by the generally soft, unsegmented abdomen, attached to the cephalothorax by a constricted portion, or peduncle. Respiration is effected by pulmonary sacs usually in combina- tion with tracheae. (Hence the name Pulmotrachearia, some- times applied to the order.) The number of the pulmonary ANNULOSA : ARACHNIDA. 22Q sacs is smaller in the true Spiders than in the Scorpions, being either two or four, opening by as many stigmata upon the under surface of the abdomen. The head bears from six to eight simple eyes ; the mandibles are simply hooked, and are perforated by the duct of a gland which secretes a poisonous fluid ; and the maxillary palpi are never chelate. Spiders (fig. 77) are all predaceous animals, and many of them possess the power of constructing webs for the capture of their prey or for lining their abodes. For the production of the web, Spiders are furnished with special glands, situated at the extremity of the abdomen. The secretion of these glands is a viscid fluid which hardens rapidly on exposure to air, and which is cast into its proper, thread-like shape, by being passed through what are called the "spinnerets." These are little conical or cylindrical organs four or six in number, situated Fig- 77- — Araneida. Theridion riparium (female). below the extremity of the abdomen. The excretory ducts of the glands open into the spinnerets, each of wrhich has its apex perforated by a great number of minute tubes, through which the secretion of the glands has to pass before reaching the air. Many spiders, however, do not construct any web, unless it be for their own habitations, but hunt their prey for themselves. As regards the reproductive process in the Spiders, it appears certain that the act of copulation, so to speak, is per- formed by the males by means of the maxillary palpi, the extremities of which are specially modified for this purpose. The testes are abdominal, but the semen appears to be stored up in the enlarged extremities of the maxillary palps, which thus perform the part of the vesiculse seminales. " The most careful observations, repeated by the most attentive and expe- rienced entomologists, have led to the conviction that the ova 230 MANUAL OF ZOOLOGY. are fertilised by the alternate introduction into the vulva of the appendages of the two palpi of the male. Treviranus's supposition that these acts are merely preliminary stimuli, has received no confirmation, and is rejected by Duges, Westwood, and Blackwall ; and with good reason, as the detection of the spermatozoa in the palpal vesicles has shown. . . . Duges offers the very probable suggestion that the male himself may apply the dilated cavities of the palpi to the abdominal aper- ture (of the testes), and receive from the vasa deferentia the fertilising fluid, preparatory to the union. . . . Certain it is that an explanation of this singular condition of the male ap- paratus, in which the intromittent organ is transferred to the remote and outstretched palp, is afforded by the insatiable proneness to slay and devour in the females of these most predaceous of articulated animals."— (Owen.) The Spiders are oviparous, and the young pass through no metamorphosis ; but they cast their skins, or moult, repeatedly, before they attain the size of the adult. DISTRIBUTION OF ARACHNIDA IN TIME. — The Arachnida are only very rarely found in a fossil condition. As far as is yet known, both the Scorpions and the true Spiders appear to have their commencement in the Carboniferous epoch, the former being represented by the celebrated Cyclophthalmus senior from the Coal-measures of Bohemia. Spiders are also known to occur in the Jurassic Rocks (Solenhofen Slates) and in the Tertiary period. CHAPTER XXXVIII. MYRIAPODA. CLASS III. MYRIAPODA. — The Myriapoda are defined as articu- late animals in which the head is distinct, and the remainder of the body is divided into nearly similar segments, the thorax exhibiting no clear line of demarcation from the abdomen. There is one pair of antenna, and the number of the legs is indefinite. Respiration is by trachea. In this class — comprising the Centipedes (fig. 78) and the Millipedes — the integument is chitinous, the body is divided into a number of somites provided with articulated appen- dages, and the nervous and circulatory organs are con- structed upon a plan similar to what we have seen in Crustacea ANNULOSA: MYRIAPODA. 231 Fig. 78.— Centipede (Scolopendra) reduced. and Arachnida. The head is invariably distinct, and there is no marked line of demarcation between the segments of the thorax and those of the abdomen. The body always consists of more than twenty somites, and those which corre- spond to the abdomen in the Arachnida and Insecta are always provided with locomotive limbs. " The head consists of at least five, and probably of six, coalescent and modified somites, and some of the anterior segments of the body are, in many genera, coales- cent, and have their appendages specially modified to subserve prehension." — (Hux- ley.) The respiratory organs, with one ex- ception, agree with those of the Insecta and of many of the Arachnida in being "tracheae" — that is to say, ramified tubes, which open upon the surface of the body by minute apertures, or " stigmata," and the walls of which are strengthened by a spirally coiled filament of chitine. The somites, with the exception of the head and the last abdominal segment, are usually undistinguishable from one another, and each bears a single pair of limbs. In some cases, however, each segment appears to be provided with two pairs of appendages (fig. 79). This is really due to the coalescence of the somites in pairs, each apparent segment being in reality composed of two amalgamated somites. This is shown, not only by the bigeminal limbs, but also by the arrangement of the stigmata, which in the normal forms occur on every alternate ring only, whereas in these aberrant forms they are found upon every ring. The head always bears a pair of jointed antennae, resembling those of many Insects, and behind the antennae there is gene- rally a variable number of simple sessile eyes. The young, in some cases, on escaping from the egg, possess nearly all the characters of the parents, except that the number of somites, and consequently of limbs, is always less, and increases at every change of skin ("moult" or "ecdysis"). In other cases, there is a species of metamorphosis, the embryo being at first either devoid of locomotive appendages, or pos- sessed of no more than three pairs of legs, thus resembling the true hexapod Insects. In these cases the number of legs proper to the adult is not obtained until after several moults, 232 MANUAL OF ZOOLOGY. the entire process being stated to occupy in some species as much as two years, before maturity is reached. The Myriapoda are divided into two orders — viz., the Chilo- poda and the Chilognatha. ORDER I. CHILOPODA. — This order comprises the well- known carnivorous Centipedes and .their allies, and is charac- terised by the number of legs being rarely indefinitely great (usually from 15 to 20 pairs), by ttys composition of the antennae out of not less than 14 joints (14 to 40 or more), and by the structure of the masticating organs. These consist of a pair of mandibles with small palpi, a labium, and two pairs of" maxillipedes," or foot-jaws, of which the second is hooked, and is perforated for the discharge of a poisonous fluid. There is not more than one pair of legs to each somite, and the last two limbs are often directed backwards in the axis of the body, so as to form a kind of tail. The body in all the Chilopoda is flattened. Scolopendra (fig. 78), Lithobius, and Geophilus are common European genera of this order. The ordinary Centipedes of this country are perfectly harmless, but those of tropical regions sometimes attain a length of a foot, or more, and these are capable of inflicting very severe, and even dangerous, bites. ORDER II. CHILOGNATHA. — This order comprises the vege- table-eating Millipedes (lulidce) and the Gallyworms (Polydes- mus). The order is characterised by the great number of legs, each segment — except the anterior ones — bearing two pairs ; by the composition of the antennae out of six or seven joints; and by the structure of the masticating organs, which consist of a pair of mandibles without palps, covered by a lower lip, composed of the confluent maxillae. Fig. 79. — Millipede (lulus). In the common Millipede (lulus) the body is composed of from forty to fifty segments, each of which bears two pairs of minute, thread-like legs. The lull of this country are of small size, but an American species attains a length of more than half a foot. DISTRIBUTION OF MYRIAPODA IN TIME. — About twenty species of Myriapoda are known as fossils, the oldest example ANNULOSA : INSECT A. 233 of the order having been found in the Carboniferous epoch. From rocks of this age several species of Chilognathous Myria- pods have been discovered. They belong to the genera Xylobins and Archiulus, and have been placed in a special family under the name of Archiulida. The occurrence of air-breathing articulate animals (both Arachnida and Myria- poda) in the Carboniferous period is noticeable, as being contemporaneous with the earliest known terrestrial Molluscs. CHAPTER XXXIX. INSECTA. GENERAL CHARACTERS OF THE INSECTA. CLASS IV. INSECTA. — The Insecta are denned as articulate animals in which the head, thorax, and abdomen are distinct; there are three pairs of legs borne on the thorax; the abdomen is destitute of legs ; a single pair of antenna is present ; mostly, there are two pairs of wings on the thorax. Respiration is effected by trachea. In the Insecta the body is divided into a variable number of definite segments, or somites, some of which are furnished with jointed appendages, and the nervous and circulatory systems are constructed upon essentially the same plan as in the Crustacea, Arachnida, and Myriapoda. The head, thorax, and abdomen are distinct (fig. 80), and the total number of somites in the body never exceeds twenty. " Of these, five certainly, and six probably, constitute the head, which pos- sesses a pair of antennae, a pair of mandibles, and two pairs of maxillae, the hinder pair of which are coalescent, and form the 'labium.' Three, or perhaps, in some cases, more, somites unite and become specially modified to form the thorax, to which the three pairs of locomotive limbs, characteristic of perfect Insects, are attached. Two additional pairs of loco- motive organs, the wings, are developed, in most insects, from the tergal walls of the second and third thoracic somites. No locomotive limbs are ever developed from the abdomen of the adult insect, but the ventral portions of the abdominal somites, from the eighth backwards, are often metamorphosed into apparatuses ancillary to the generative function." — (Huxley.) 234 MANUAL OF ZOOLOGY. The integument of the Insecta, in the mature condition, is more or less hardened by the deposition of chitine, and usually forms a resisting exoskel- eton, to which the mus- cles are attached. The segments of the head are amalgamated into a single piece, which bears a pair of jointed feelers or an- tennae, a pair of eyes, usually compound, and the appendages of the mouth. The segments of the thorax are also amalgamated into a single piece ; but this, neverthe- less, admits of separation into its constituent three somites (fig. 80). These are termed respectively, from before backwards, the "prothorax," "meso- thorax," and " metatho- rax," and each bears a pair Fig. 80.— Diagram of Insect a Head, carrying of jointed legS. In the the eyes and antenna; £ Prothorax, carrying great majority of InSCCtS, the first pair of legs ; c Mesothorax, carrying & . J . J , r , i the second pair of legs and first pair of wings ; d the QOrsal archCS OI the Metathorax, with the third pair of legs and the mac/-\fhrkrc] Y nnrl rnpfa second pair of wings; * Abdomen, without .limbs, niCSOtnoraX and meta- but having terminal appendages subservient to thorax glVC Origin each reproduction. to a pair of wingS. Each leg consists of from six to nine joints. The first of these, which is attached to the sternal surface of the thorax, is called the " coxa," and is succeeded by a short joint, termed the "trochanter." The trochanter is followed by a joint, often of large size, called the " femur," and this has articulated to it the " tarsus," which may be composed of from two to five joints. The wings of Insects are membranous " flattened vesicles, sustained by slender but firm hollow tubes, called ' nervures/ along which branches of the tracheae and channels of the cir- culation are continued." — (Owen.) In the Cokoptera (Beetles) the anterior pair of wings become hardened by the deposition of chitine, so as to form two protective cases for the hinder membranous wings. In this condition the anterior wings are known as the "elytra," or "wing-cases." In some of the Hemiptera this change only affects the inner portions of the ANNULOSA : INSECTA. 235 anterior wings, the apices of which remain membranous, and to these the term uhernelytra;' is applied. In the Diptera the posterior pair of wings are rudimentary, and are converted into two capitate filaments, called " halteres," or " balancers." In the Strepsiptera the anterior pair of wings are rudimentary, and are converted into twisted filaments. The abdomen in Insects is normally composed of nine somites, which are usually more or less freely movable upon one another, and never carry locomotive limbs. The extremity of the abdomen is, however, not infrequently furnished with appendages, which are connected with the generative function, and not infrequently serve as offensive and defensive weapons. Of this nature are the ovipositors of Ichneumons and other Insects, and the sting of Bees and Wasps. In the Earwig (Forficula) these caudal appendages form a' pair of forceps; whilst in many Insects they are in the form of bristles, by which powerful leaps can be effected, as is seen in the Spring- tails (Podura). The organs about the mouth in Insects are collectively termed the " trophi," or " instrumenta cibaria." Two principal types require consideration — namely, the masticatory and the suctorial — both types being sometimes modified, and occasion- ally combined. In the Masticatory Insects, such as the Beetles (fig. 81, i), Fig. 81. — Organs of the mouth in Insects, i. Trophi of a masticating Insect (Beetle): a Labrum or upper lip ; b Mandibles ; c Maxillae with their palpi ; d Labium or lower lip with its palpi. 2. Mouth of a Butterfly: o Eye; ./"Base of antennae; g Labial palp ; h Spiral trunk or "antlia." 3. Mouth of a Hemipterous Insect {Nepa cinerea): I Labium ; m Maxillae ; n Mandibles. the trophi consist of the following parts, from before back- wards: — (i.) An upper lip, or " labrum," attached below the front of the head. (2.) A pair of biting jaws, or "mandibles." 236 MANUAL OF ZOOLOGY. (3.) A pair of chewing jaws, or " maxillae," provided with one or more pairs of "maxillary palps," or sensory and tactile filaments. (4.) A lower lip, or " labium," composed of a second coalescent pair of maxillae, and also bearing a pair of palpi, the " labial palps." The lower or basal portion of the labium is called the " mentum " or chin, whilst the upper portion is more flexible, and is termed the "ligula." The upper portion of the ligula is often developed into a kind of tongue, which is very distinct in some Insects, and is termed the " lingua." In the typical suctorial mouth, as seen in the Butterflies (fig. 8 1, 2), the following is the arrangement of parts: — The labrum and the mandibles are now quite rudimentary; the first pair of maxillae is greatly elongated, each maxilla forming a half-tube. These maxillae adhere together by their inner surfaces, and thus form a spiral " trunk," or " antlia " (inappro- priately called the " proboscis ")f by which the juices of flowers are sucked up. Each maxilla, besides the half-tube on one side, contains also a tube in its interior ; consequently on a transverse section the trunk is found really to consist of three canals, one in the interior of each maxilla, and the third formed between them by their apposition. To the base of the trunk are attached the maxillary palpi, which are extremely small. Behind the trunk is a small labium, composed of the united second pair of maxillae. The " labial palpi " are greatly devel- oped, and form two hairy cushions, between which the trunk is coiled up when not in use. In the Bee there exists an intermediate condition of parts, the mouth being fitted partly for biting and partly for suction. The labrum and mandibles are^well developed, and retain their usual form. The maxillae and the labium are greatly elon- gated ; the former being apposed to the lengthened tongue in such a manner as to form a tubular trunk, which cannot be rolled up, as in the Butterflies, but is capable of efficient suc- tion. The labial palpi are also greatly elongated. In the ffemiptera, the " trophi " consist of four lancet-shaped needles, which are the modified mandibles and maxillae, enclosed in a tubular sheath formed by the elongated labium (fig. 81, 3). Lastly, in the Diptera — as in the common House-fly — there is an elongated labium, which is channelled on its upper surface for the reception of the mandibles and maxillae, these being modified into bristles or lancets. The mouth in the Masticating Insects leads by a pharynx and oesophagus into a membranous, usually folded, stomach — the " crop," or " ingluvies " — from which the food is trans- ANNULOSA: INSECTA. '37 mitted to a second muscular stomach, called the " gizzard " (fig. 82). The gizzard is adapted for crushing the food, often hav- ing plates or teeth of chitine developed in its walls, and is suc- ceeded by the true digestive cavity, called the "chylific sto- mach " (vcntriculus chylopoieti- cus}. From this an intestine of variable length proceeds, its terminal portion, or rectum, opening into a dilatation which is common to the ducts of the generative organs, and is termed the "cloaca." The oesophagus is furnished with salivary glands of varying size and complexity, and is provided in some of the Suctorial Insects with a dilata- tion called the "sucking sto- mach." Behind the pyloric aperture of the stomach, with very few exceptions, are a vari- able number of caecal, convolu- ted tubes (fig. 82, e), which open into the intestine, and are called the "Malpighian tubes." These are often looked upon as representing the liver, but are by some believed to have a renal function. If the Malpig- hian vessels truly perform the functions of a liver — as their position would appear to prove — then the kidneys will be repre- sented by a series of csecal tubes which are only occasionally present, and which open into the rectum, close to the cloaca. There are no absorbent vessels, and the products of digestion simply transude through the walls of the alimentary canal into the sinuses or irregular cavities which exist between the abdom- inal organs. The apparatus of digestion does not differ essen- tially from the above in any of the Insects, but the alimentary canal is, generally speaking, considerably lengthened in the herbivorous species. There is no definite and regular course of the circulation in the Insects. The propulsive organ of the circulation is a long contractile cavity, situated in the back and termed the " dorsal vessel." This is composed of a number of sacs (ordinarily Fig. 82. — Digestive system of a Beetle (Carabus auratiis), a (Esophagus ; b Crop ; c Gizzard ; d Chylific stomach ; e Malpighian tubes; /Intestine; ^Clo- aca ; h Supposed renal vessels. 238 MANUAL OF ZOOLOGY. eight), opening into one another by valvular apertures, which allow of a current in one direction only — viz., towards the head. The blood is collected from the irregular venous sinuses which are formed by the lacunae and interstices be- tween the tissues, and enters the dorsal vessel from behind ; it is then driven forwards, and is expelled at the anterior ex- tremity of the body. Respiration is effected by means of " tracheae," or branched tubes, which commence at the surface of the body by lateral apertures, called " stigmata," or " spiracles," and ramify through every part of the animal. In structure the tracheae are mem- branous, but their walls are strengthened by a chitinous fila- ment, which is rolled up into a continuous spiral coil. In the aquatic larvae of many insects, and in one adult insect, branches of the tracheae are sent to temporary outgrowths which are termed " tracheal gills," and in which the blood is oxygenated. In all, however, except the single insect above mentioned, these temporary external appendages fall off when maturity is attained. The wings, also, whilst acting as locomo- tive organs, doubtless subserve respiration. The nervous system in Insects, though often concentrated into special masses, consists essentially of a chain of ganglia, placed ventrally, and united together by a series of double cords or commissures. The cephalic or " prae-cesophageal " ganglia are of large size, and distribute filaments to the eyes and antennae. The post-oesophageal ganglia are united to the preceding by cords which form a collar round the gullet, and they supply the nerves to the mouth, whilst the next three ganglia furnish the nerves to the legs and wings. The organs of sense are the eyes and antennae. The eyes in Insects are usually " compound," and are composed of a number of hexagonal lenses, united together, and each supplied with a separate nervous filament. Besides these, simple eyes —"ocelli," or "stemmata" — are often present, or, in rare cases, may be the sole organs of vision. In structure these resemble the single elements of the compound eyes. In a few cases the eyes are placed at the extremities of stalks or ped- uncles, but in no case are these peduncles movably articulated to the head, as is the case in the Podophthalmous Crustaceans. The antennae are movable, jointed filaments, attached usually close to the eyes, and varying much in shape in different In- sects. They doubtless discharge the functions of tactile prgans, but are probably the organ of other more recondite senses in addition. The sexes in Insects are in different individuals, and most ANNULOSA : INSECTA. 239 are oviparous. Generally speaking, the young insect is very different in external characters from the adult, and it requires to pass through a series of changes, which constitute the " meta- morphosis," before attaining maturity. In some Insects, how- ever, there appears to be no metamorphosis, and in some the changes which take place are not so striking or so complete as in others. By the absence of metamorphosis, or by the degree of its completeness when present, Insects are divided into sections, called respectively Ametabola, Hemimetabola, and ffolometabola, which, though not, perhaps, of a very high scien- tific value, are nevertheless very convenient in practice. Section i. Ametabolic Insects. — These pass through no meta- morphosis, and also, in the mature condition, are destitute of wings. The young of these insects (Apterd] on escaping from the ovum resemble their parents in all respects except in size ; and though they may change their skins frequently, they undergo no alteration before reaching the perfect condition, except that they grow larger. Section 2. Hemimetabolic Insects. — In the insects belonging to this section there is a metamorphosis consisting of three stages. The young on escaping from the ovum is termed the larva ; " when it reaches its second stage it is called the pupa," or " nymph ; " and in its third stage, as a perfect nsect, it is called the " imago." In the Hemimetabola, the 1 larva," though of course much smaller than the adult, or * imago," differs from it in little else except in the absence of wings. It is active and locomotive, and is generally very like the adult in external appearance. The " pupa," again, is a little larger than the larva, but really differs from it in nothing else than in the fact that the rudiments of wings have now appeared, in the form of lobes enclosed in cases. The "pupa" is still active and locomotive, and the term " nymph " is usually applied to it. The pupa is converted into the perfect insect, or " imago," by the liberation of the wings, no other change being requisite for this purpose. From the comparatively small amount of difference between these three stages, and from the active condition of the pupa, this kind of metamorphosis is said to be " incomplete." In some members of this section, however — such as the Dragon-flies — the larva and pupa are aquatic, whereas the imago leads an aerial life. In these cases there is necessarily a considerable difference between the larva and the adult ; but the larva and pupa are closely alike, and the latter is active. Section 3. Holometabolic Insects. — These — comprising the Butterflies, Moths, Beetles, &c. — pass through three stages 240 MANUAL OF ZOOLOGY. which differ greatly from one another in appearance, the me- tamorphosis, therefore, being said to be "complete." In these insects (fig. 83) the " larva " is vermiform, segmented, and usually provided with loco- motive feet, which do not correspond with those of the adult, though these latter are usually present as well (figs. 83, 89). In some cases the larva is destitute of legs, or is " apodal." The larva is also provided with mastica- tory organs, and usually eats voraciously. In this stage of the metamorphosis the larvae constitute what are usually called " caterpillars " and "grubs." Having remained in this condition for a longer or shorter length of time, and having undergone repeated changes of skin, or " moults," Fig. 83.— Metamorphosis of the Magpie- necessitated by its rapid growth, the larva passes into the second stage, and becomes a " pupa." The insect is now perfectly quiescent, unless touched or otherwise irritated, is incapable of changing its place, and is often attached to some foreign object. This constitutes what — in the case of the Lepidoptera — is generally known as the " chrysalis," or " aure- lia" (fig. 88). The body of the pupa is usually covered by a chitinous pellicle, which closely invests the animal. In some cases the pupa is further protected within the dried skin of the larva; and in other cases the larva — immediately before en- tering upon the pupa-stage — spins, by means of special organs for the purpose, a protective case, which surrounds the chry- salis, and is termed the " cocoon." Having remained for a variable time in the quiescent pupa- stage, and having undergone the necessary development, the insect now frees itself from the envelope which obscured it, and appears as the perfect adult, or " imago," characterised by the possession of wings. SEXES OF INSECTS. — The great majority of Insects, as is the case with most of the higher animals, consist of male and female individuals; but there occur some striking exceptions ANNULOSA: INSECTA. 241 to this rule, as seen in the Social Insects. In those organised communities which are formed by Bees, Ants, and Termites, by far the greater number of the individuals which compose the colony are either undeveloped females, or are of no fully developed sex. This is the case with the workers amongst Bees, and the workers and soldiers amongst Ants and Termites. And these sterile individuals, or " neuters," as they are com- monly called, are not necessarily all alike in structure and external appearance. Amongst the Bees all the neuters re- semble one another, but amongst Ants and Termites they are often divided into " castes " which have different functions to perform in the general polity, and differ from one another greatly in their characters. In all the above-mentioned insects the males are relieved from the performance of any of the duties of life except that of propagating the species ; and the females — which are gene- rally solitary in each community — fulfil no other function save that of laying eggs. All the other duties which are necessary for the existence of the community are performed by the workers, or neuters. The organs of the two sexes are in no case united in the same individual, or, in other words, there are no hermaphro- dite Insects. As has been noticed, however, before, asexual reproduction is by no means unknown amongst the Insecta, and the attendant phenomena are often of extreme interest. (See Introduction.) CHAPTER XL. DIVISIONS OF INSECTA. THE class Insecta includes such an enormous number of species, genera, and families, that it would be impossible to treat of these satisfactorily otherwise than in a treatise especially de- voted to Entomology. Here it will be sufficient to give simply the differential characters of the different orders, draw- ing attention occasionally to any of the more important points in connection with any given family. As already said, the Insecta are divided into three divisions, termed Ametabola, Hemimetabola, and Holometabola, according as they attain the adult condition without passing through a metamorphosis, or have an incomplete or complete metamor- VOL. I. Q 242 MANUAL OF ZOOLOGY. phosis. The Insects which come under the first head (viz. Ametabold] are not furnished with wings in the adult condition, and the three orders which compose this section are com- monly grouped together under the name Aptera. By some, however, this division is entirely rejected, and the three orders in question are placed amongst the Hemimctabola, or even grouped with the Myriapoda. SUB-CLASS I. AMETABOLA. — Young not passing through a metamorphosis, and differing from the adult in size only. Imago destitute of wings ; eyes simple, sometimes wanting. ORDER I. ANOPLURA. — Minute Aptera, in which the mouth is formed for suction ; and there are two simple eyes, or none. This order comprises insects which are commonly parasitic upon man and other animals, and are known as Lice (Pediculi]. The common Louse is furnished with a simple eye, or ocellus, on each side of a distinctly differentiated head, the under sur- face of which bears a suctorial mouth. There is little distinc- tion between the thorax and abdomen, but the segments of the former carry three pairs of legs. The young pass through no metamorphosis, and their multiplication is extremely rapid. ORDER II. MALLOPHAGA. — Minute Aptera, in which the mouth is formed for biting, and is furnished with mandibles and maxillae. The members of this order are commonly known as " Bird- lice," being parasitic, sometimes upon Mammals, but mostly upon Birds. They strongly resemble the Pediculi, but the mouth is formed for biting, to suit their mode of life ; since they do not live upon the juices of their hosts, but upon the more delicate tegumentary appendages. ORDER III. THYSANURA. — Apterous insects, usually with a masticatory mouth, and having the extremity of the abdomen furnished with locomotive appendages. The most familiar members of this order are the Podura, or " Spring-tails," which are characterised by the possession of a forked caudal appendage, by the extension of which consider- able leaps can be effected. In the nearly allied Lepismce loco- motion is assisted by caudal bristles. In both, the body is covered with hairs or scales, the structure of the latter being often very beautiful. SUB-CLASS II. HEMIMETABOLA. — Metamorphosis incomplete; the larva differing from the imago chiefly in the absence of wings, and in size; pupa usually active, or, if quiescent, capable of movement* * The Coccidce, amongst the Hemiptera, undergo a complete metamor- phosis. In certain of the Hemiptera and Orthoptera the adult is apterous, ANNULOSA : INSECTA. 243 ORDER IV. HEMIPTERA. — Mouth suctorial, beak-shaped, consisting of a jointed rostrum, composed of the elongated Fig. 84. — Hemiptera. Bean Aphis (Aphis f aba), winged male and wingless female. labium, which forms a sheath for the bristle-shaped styliform mandibles and maxillae Eyes compound, usually with ocelli as well. Two pairs of wings. The Hemiptera live upon the juices of plants or animals, which they are enabled to obtain by means of the suctorial rostrum. Amongst the more familiar examples of this order are the Plant-lice (Aphides, fig. 84), the Field-bug (Pentatoma), the Boat-fly (Notonectd], the Cochineal Insects (Coca), and the Cicadas. The order is divided into the following two sub-orders : — Sub -order a. Homoptera. — The anterior pair of wings of the same texture throughout (membranous) ; the mouth turned backwards, so that the beak springs from the back of the head. Sub-order b. Heteroptera. — An- terior wings membranous near their apices, but chitinous to- wards the base (hemelytra). The rostrum springing from the front of the head. ORDER V. ORTHOPTERA. — Mouth masticatory; wings four; the anterior and in these cases there cannot be said to be any metamorphosis, since the larvae differ from the adult only in size, in having fewer joints to the antennas, and in having a smaller number of facets in each of the com- pound eyes. 244 MANUAL OF ZOOLOGY. pair smaller than the posterior, coriaceous or leathery, and forming elytra; posterior pair of wings membranous, folded longitudinally like a fan. This order includes the Crickets (Achetina), Grasshoppers (Gryllind), Locusts (Locnstina\ Cockroaches (Blattina, fig. 85), &c. Some of them are formed for running (cursorial], all the legs being nearly equal in size ; whilst in others the first pair of legs are greatly developed, and form powerful raptorial organs, as in the Mantis. In others, again, as in the Grasshoppers and Crickets, the hindmost pair of legs are greatly elongated, so as to give a considerable power of leaping to them. All the Orthoptera are extremely voracious, and the ravages caused by locusts in hot countries are well known to all. ORDER VI. NEUROPTERA. — Mouth usually masticatory ; wings four in number, all membranous, generally near- ly equal in size, traversed by numerous delicate nervures, having a longitudinal and transverse direction, and giv- ing them a reticulated, lace- like aspect. Metamorphosis generally incomplete, rarely complete. This order includes the Dra- gon-flies (Libelhtlidcz), Caddis- flies (Phryganeida), May-flies (Ephcmcrida)? the Ant-lion (MyrmeUo), Termites, &c. The last of these — namely, the Termites or White Ants — are social, and live in communi- ties, and their habits are so singular that a short description of them will not be out of place here. They are mostly inhabit- ants of hot countries, where they are commonly known as " White Ants;" but it must be borne in mind that they have nothing to do with the insects commonly called Ants, which belong, indeed, to a different order (Hymenoptera). The follow- ing account is taken from Mr Bates's work on the Amazons, where there is an excellent description of the habits of these remarkable insects. Termites are small, soft-bodied insects, which live in large Fig. 86. — Neuroptera. Aphis-lion (Heme robiicUe), imago, larva, and eggs. * By Huxley the Dragon-flies (Libelluttdtz\ the May-flies and the Termites are placed amongst the Orthoptera ; whilst the Caddis- flies are placed in a separate order under the name of Trichoptera. ANNULOSA: INSECTA. 245 communities, as do the true Ants. They differ, however, from the Ants in the fact that the workers are individuals of no fully developed sex, whereas amongst the latter they are undeveloped females. Further, the neuters of the Termites are always composed of two distinct classes or " castes " — the workers and the soldiers. Lastly, the Ants undergo a quiescent pupa-stage, whereas the young Termites on their emergence from the egg do not differ from the adult in any respect except in size. Each species of Termites consists of several distinct orders or castes, which live together, and constitute populous, or- ganised communities. They inhabit structures known as " Termitaria," consisting of mounds or hillocks, some of which are " five feet high, and are formed of particles of earth worked into a material as hard as stone." The Termitarium has no external aperture for ingress or egress, as far as can be seen, the entrance being placed at some distance, and connected with the central building by means of covered ways and galleries. Each Termitarium is composed of "a vast num- ber of chambers and irregular intercommunicating galleries, built up with particles of earth or vegetable matter, cemented together with the saliva of the insects." Many of " the very large hillocks are the work of many distinct species, each of which uses materials differently compacted, and keeps to its own portion of the tumulus." A family of Termites consists of a king and queen, of the workers, and of the soldiers. The royal couple are the parents of the colony, and " are always kept together, closely guarded by a detachment of workers, in a large chamber in the very heart of the hive, surrounded by much stronger walls than the other cells. They are both wingless, and immensely larger than the workers and soldiers. The queen, when in her chamber, is always found in a gravid condition, her abdomen enormously distended with eggs, which, as fast as they come forth, are conveyed by a relay of workers in their mouths from the royal chamber to the minor cells dispersed through the hive." At the beginning of the rainy season a number of winged males and females are produced, which, when they arrive at maturity, leave the hive, and fly abroad. They then shed their wings (a special provision for this existing in a natural seam running across the root of the wing and dividing the nervures); they pair, and then become the kings and queens of future colonies. The workers and the soldiers are distinct from the moment 246 MANUAL OF ZOOLOGY. of their emergence from the egg, and they do not acquire their special characteristics in consequence of any difference of food or treatment. Both are wingless, and they differ solely in the armature of the head. The duties of the workers are to " build, make covered roads, nurse the young brood from the egg upwards, take care of the king and queen, who are the progenitors of the whole colony, and secure the exit of the males and females when they acquire wings and fly out to pair and disseminate the race/' The duties of the soldiers are to defend the community from all attacks which may be made upon its peace, for which purpose the mandibles are greatly developed. It may well be admitted, that in such organised communities as those of the Termites, we have the highest development of Insect-life yet known to us. The principle of the division of labour is carried out to its fullest extent — much further, indeed, than is possible amongst human beings — since the perfection of the greater number of the individuals which compose the com- munity— as organisms — is sacrificed in order to secure the ful- filment of the duties which are necessary for the existence and welfare of the whole. Even the task of perpetuating the species, and of giving origin to fresh colonies, is entirely left to one class of the community, the defence and protection of which is the special object and care of the remainder. No higher de- velopment could well be imagined amongst creatures devoid of the higher psychical endowments ; and it is worthy of note that at least three distinct and independent families of Insects have attained to this stage — namely, the Termites, the Bees, and the true Ants. SUB-CLASS III. HOLOMETABOLA. — Metamorphosis complete; the larva, pupa, and imago differing greatly from one another in external appearance. The larva vermiform, and the pupa qui- escent. ORDER VII. APHANIPTERA. — Wings rudimentary, in the form of plates, situated on the mesothorax and metathorax. Mouth suctorial. Metamorphosis complete. This order comprises the Fleas (Pulicidcz), most of which are parasitic upon different animals. The larva of the common Flea is an apodal grub, which in about twelve days spins a cocoon for itself, and becomes a quiescent pupa, from which the imago emerges in about a fortnight more. ORDER VIII. DIPTERA. — The anterior pair of wings alone developed ; the posterior pair of wings rudimentary, repre- sented by a pair of clubbed filaments, called " halteres," or " balancers " (fig. 87). Mouth suctorial. The metamorphosis ANNULOSA: INSECTA. 247 is complete, the larvae being completely destitute of feet ; but in some cases (e.g,, the gnats) the pupae are aquatic and are actively locomotive. In most cases, however, the pupae are quiescent. The Diptera constitute one of the largest of the orders of the Insecta; the House-flies (Mused), Gnats (Cufex), Forest- flies (Hippobosca\ and Gad-flies (Tabanida\ constituting good examples. Fig. 87. — Diptera. Crane-fly ( Tipula oleracea), ORDER IX. LEPIDOPTERA. — Mouth suctorial, consisting of a spiral trunk or " antlia," composed of the greatly elongated maxillae, protected, when not in use, by the cushion-shaped, hairy, labial palpi. Labrum and mandibles rudimentary. Wings four in number, flattened, covered with modified hairs or scales. Larvae vermiform, commonly known as "cater- pillars." This well-known and most beautiful of all the orders of Insects comprises the Butterflies (fig. 88) and the Moths (fig. 89) ; the former being diurnal in their habits, the latter mostly crepuscular or nocturnal. The larvae of Lepidoptera (fig. 89), commonly called " cater- pillars," are vermiform in shape, normally composed of thirteen segments, the anterior portion forming a distinct horny head, with antennae, jaws, and usually simple eyes. The mouth of the caterpillar, unlike that of the perfect insect, is formed for 248 MANUAL OF ZOOLOGY. mastication. The labium also is provided with a tubular organ — the " spinneret " — which communicates with two internal glands, the functions of which are to furnish the silk, whereby Fig. 88.— Large White Cabbage Butterfly (Pontia brassier), a Larva or Caterpillar ; b Pupa or Chrysalis ; c Imago or perfect Insect. Fig. 89. — Goat-moth (Cossus ligniperda) and Caterpillar. ANNULOSA: INSECTA. 249 the animal constructs its ordinary abode, or spins its cocoon. The three segments behind the head correspond with the pro- thorax, mesothorax, and metathorax of the perfect insect, and carry three pairs of jointed walking-legs. Besides these, a variable number of the segments of the abdomen are provided with soft, fleshy legs, which are called " pro-legs " (fig. 89). ORDER X. HYMENOPTERA. — Wings four, membranous, with few nervures ; sometimes absent. Mouth always provided with biting jaws, or mandibles ; the maxillae and labium often converted into a suctorial organ. Females having the ex- tremity of the abdomen mostly furnished with an ovipositor (terebra or aculeus). The Hymenoptera form a very extensive order, comprising the Bees, Wasps, Ants, Ichneumons, Saw-flies (fig. 90), &c. The ovipositor, which is very generally present in the females of this order, is sometimes a boring or- gan (terebra), or in other cases a " sting " (aculeus). Amongst the Hymenop- tera we find social com- munities, in many respects resembling those of the Termites, of which a de- scription has already been given. The societies of Bees and Ants are well known, and merit a short description. The social Bees, of which the common Ho- ney-bee (Apis mellificd) is so familiar an example, form organised communi- ties, consisting of three classes of individuals — the males, females, and neuters. As a rule, each community consists of a single female — " the queen " — and of the neuters, or "workers." The impregnation of the female is effected by the production of males, or " drones," during the summer. After impregnation has been effected, the drones, as being then useless, are destroyed by the workers. The eggs produced by the fecundated queen are mostly intended Fig. 90.— Gooseberry Saw-fly (Tenthredo gros- sularice), larva, pupa, and imago- 250 MANUAL OF ZOOLOGY. „ to give origin to neuters, to which end they are placed in the ordinary cells. The ova which are to give origin to females — the " queens" of future colonies — are placed in cells of a peculiar construction, and the larvae are fed by the workers with a special food. The ova which are to produce males are likewise placed in cells, which are slightly larger than those allotted to the workers. It is asserted, however, that this is not the sole or true cause of the production of the males ; but that the ova which are intended to produce drones are not fer- tilised by the female with the semen which she has stored up in her spermatheca, and are therefore produced by a process of Parthenogenesis. That the males are produced partheno- genetically in some, at any rate, of the Hymenoptera, appears to have been placed beyond a reasonable doubt by the researches by Von Siebold. (See Introduction.) In the Humble-bees (Bombida), and in the Wasps (Ves- pid continue their movements long after the death of the animal. MOLLUSCOIDA: POLYZOA. 263 stage, which is termed by Professor Allman the " lophophore." In the majority of Polyzoa — including almost all the marine species — the lophophore is circular (fig. 95, 2), but in most of the fresh-water forms it has its neural side extended into two long arms, so that the entire lophophore becomes crescentic or "horse-shoe-shaped" (fig. 95, 3); hence this section is sometimes collectively termed the " Hippocrepian " Polyzoa. In all the Polyzoa in which this crescentic condition of the lophophore exists, there is also a singular valve-like organ which arches over the mouth, and is termed the " epistome." The only marine forms in which the lophophore is bilateral are Pedicellina and Rhabdopleura ; the only fresh-water species in which the lophophore is orbicular are Paludicella and Urnatetta. The mouth conducts by an oesophagus into a dilated stomach. In some cases a pharynx may be present, and in others there is in front of the stomach a muscular proventriculus, or giz- zard. From the stomach proceeds the intestine, which shortly turns forward to open by a distinct anus close to the mouth. As the nervous ganglion is situated on that side of the mouth towards which the intestine turns in order to reach its ter- mination, the intestine is said to have a " neural flexure," and this relation is constant throughout the entire class. Respiration in the Polyzoa appears to be carried on by the ciliated tentacles, and by the " perigastric space," which is filled with a clear fluid, containing solid particles in suspension. A kind of circulation is kept up in this "perigastric fluid" by means of the cilia lining the inner surface of the endocyst. Beyond this there is nothing that could be called a circulation, and there are no distinct circulatory organs of any kind. The nervous system in all the Polyzoa consists of a single small ganglion (fig. 94, 2), placed upon one side of the oeso- phagus, between it and the anal aperture. Besides the single ganglion which belongs to each polypide, there is also in many, if not in all, of the Polyzoa, a " colonial nervous system." That is to say, there is a well -developed nervous system, which unites together the various zooids composing the colony, and brings them into relation with one another. It is probably in virtue of this system that the avicularia are enabled to con- tinue their movements, and retain their irritability after the death of the polypides. The muscular system is well developed, and consists of various muscular bands, with special functions attaching to each. The most important fasciculi are the retractor muscles (fig. 94, 2, g), which retract the upper portion of the polypide 264 MANUAL OF ZOOLOGY. within the cell. These muscles arise from the inner surface ot the endocyst near the bottom of the cell, and are inserted into the upper part of the oesophagus. The polypide, when re- tracted, is again exserted, chiefly by the action of the " parietal muscles," which are in the form of circular bundles running transversely round the cell. As far as is known, all the Polyzoa are hermaphrodite, each polypide containing an ovary and testis (fig. 94, 2). The ovary is situated near the summit of the cell, and is attached to the inner surface of the endocyst. The testis is situated at the bottom of the cell, and a curious cylindrical appendage, called the "funiculus," usually passes from it to the fundus of the stomach. There are no efferent ducts to the reproductive organs; and the products of generation — i.e., the spermatozoa and ova — are discharged into the perigastric space, where fecundation takes place ; but it is not certainly known how the impregnated ova escape into the external medium. As already mentioned, continuous gemmation occurs in all the Polyzoa, the fresh zooids thus produced remaining attached to the organism from which they were budded forth, and thus giving rise to a compound growth. A form of discontinuous gemmation, however, occurs in many of the Polyzoa, in which certain singular bodies, called " statoblasts," are developed in the interior of the polypide. The statoblasts are found in certain seasons lying loose in the perigastric cavity. In form " they may be generally described as lenticular bodies, varying, according to the species, from an orbicular to an elongated-oval figure, and enclosed in a horny shell, which consists of two concavo-convex discs united by their margins, where they are further strengthened by a ring which runs round the entire margin, and is of different struc- ture from the discs When the statoblasts are placed under circumstances favouring their development, they open by the separation from one another of the two faces, and there then escapes from them a young Polyzoon, already in an advanced stage of development, and in all essential respects resembling the adult individual in whose cell the statoblasts were produced." — (Allman.) The statoblasts are formed as buds upon the " funiculus " — the cord already alluded to as extending from the testis to the stomach — upon which they may usually be seen in different stages of growth. They do not appear to be set free from the perigastric space prior to the death of the adult, and when liberated, they are enabled to float near the surface of the water, in consequence of the cells of the marginal ring, or "annulus," being spongy and MOLLUSCOIDA: TUNICATA. 265 filled with air. They must be looked upon as "gemma pecu- liarly encysted, and destined to remain for a period in a qui- escent or pupa-like state." — (Allman.) As regards the development of the Polyzoa, the embryo upon its emergence from the ovum presents itself as a ciliated, free- swimming, sac-like body, from which the polypide is subse- quently produced by a process of gemmation. DIVISIONS OF THE POLYZOA. — The Polyzoa are divided into two divisions or orders — the Phylactolczmata (fig. 95, 3), dis- tinguished by the possession of a bilateral horse-shoe-shaped lophophore, and of an " epistome " arching over the mouth ; and the Gymnoltzmata (fig. 95, 2), in which the lophophore is orbicular, and there is no epistome. TABLE OF THE DIVISIONS OF THE POLYZOA. — (AFTER BUSK.) ORDER I. PHYLACTOL^MATA. Lophophore bilateral ; mouth with an epistome. Sub-order I. Lophopea (fresh- water). Arms of lophophore free or obsolete ; consistence horny, sub-cal- careous. Sub-order 2. Pedicellinea (marine). Arms of lophophore united at their extremities ; consistence soft, fleshy. ORDER II. GYMNOL^MATA. Lophophore orbicular, or nearly so ; no epistome. Sub-order 3. Pahidicellea (fresh-water). Polypide completely retractile ; evagination of tentacular sheath imperfect ; consistence horny or sub-calcareous. Sub-order 4. Cheilostomata (marine). Polypide completely retractile ; evagination perfect ; orifice of cell sub-terminal, of less diameter than the cell, and usually closed with a movable lip or shutter, sometimes by a contractile sphincter ; cells not tubular ; consistence calcareous, horny, or fleshy. Sub-order 5. Cydostomata (marine). Cell tubular ; orifice terminal, of the same diameter as the cell, without any movable apparatus for its closure ; consistence cal- careous. Sub-order 6. Ctenostomata (marine). Orifice of the cell terminal, furnished with a usually setose fringe for its closure ; cells distinct, arising from a common tube ; con- sistence horny or carnose. CHAPTER XLIII. TUNICATA. CLASS II. TUNICATA (Ascidwida).—rYte members of this class of the Molluscoida are defined as follows : — " Alimentary canal 266 MANUAL OF ZOOLOGY. suspended in a double-walled sac, but not capable of protrusion and retraction ; mouth opening into the bottom of a respira- tory sac, whose walls are more or less completely lined by a network of blood-vessels." — (Allman.) Animal simple or com- posite. An imperfect heart in the form of a simple tube open at both ends. The Tunicaries are all marine, and are protected by a lea- thery, elastic integument, which takes the place of a shell. In appearance a solitary Ascidian (fig. 96) may be compared to a double-necked jar with two prominent apertures situated Fig. 96. — Morphology of Tunicata. i. Diagram of a Tunicary (after Allman) : a Oral aperture ; b Atrial aperture ; c Pharyngeal or branchial sac, with its rows of ciliated apertures; d Alimentary canal, with its haemal flexure ; e Anus ; f Atrium ; g Ner- vous ganglion. 2. Cynthia papillosa, a simple Ascidian (after Woodward). close to one another at the free extremity of the animal, one of these being the mouth, whilst the other serves as an excre- tory aperture. The covering of an Ascidian is composed of two layers. Of these the outer is called the " external tunic," or " test," and is distinguished by its coriaceous or cartilaginous consistence. It is also remarkable for containing a substance which gives the same chemical reactions as cellulose, and is probably identical with this characteristic vegetable product. The test is lined by a second coat, which is termed the " second tunic," or " mantle." and which is mainly composed of longi- tudinal and circular muscular fibres. By means of these the animal is endowed with great contractility, and has the power of ejecting water from its branchial aperture with considerable force. The mantle lines the test, but is only slightly and MOLLUSCOIDA : TUNICATA. 267 loosely attached to it, especially near the apertures. The mouth is usually surrounded by a circlet of small, non-ciliated, non-retractile tentacles, and opens into a large chamber (fig. 96, i, c\ which usually occupies the greater part of the cavity of the mantle, and has its walls perforated by numerous aper- tures. This is known variously as the " pharynx," the " respi- ratory sac," or the " branchial sac." (It must be remembered that the aperture here spoken of as the mouth can only be looked upon in this light provided that the respiratory sac is looked upon as the pharynx. By Professor Allman, whose definition is given at the head of this chapter, this view is not accepted, and consequently the internal or inferior opening of the respiratory sac is regarded as the true mouth.) Inferiorly the respiratory sac leads by a second aperture into an oeso- phagus, which opens into a capacious stomach. From the stomach an intestine is continued, generally with few flexures, to the anal aperture, which does not communicate directly with the exterior, but opens into the bottom of a second cham- ber, which is called the " cloaca " (fig. 96, i, f). Superiorly the cloaca communicates with the external medium, by means of the second aperture in the test. The first bend of the intestine is such that, if continued, it would bring the anus on the opposite side of the mouth to that on which the nervous ganglion is situated. The intestine, therefore, is said to have a " haemal flexure ; " whereas the flexure in the case of the Polyzoa is " neural." The intestine, however, in the Tunicata does not preserve this primary haemal flexure, but is again bent to the neural side of the body, the nervous ganglion coming finally to be situated between the mouth and the rectum. As just stated, the anus is not in direct communication with the exterior, but opens into a large cavity, called the " cloaca," or "atrial chamber," which, in turn, opens externally by the second aperture of the animal. This cloaca is a large sac lined by a membrane which " is reflected like a serous sac on the viscera, and constitutes the ' third tunic,' or ' peritoneum.' " From the cloaca "it is reflected over both sides of the pharynx" (respiratory sac), " extending towards its dorsal part very nearly as far as that structure which has been termed the * en- dostyle.' It then passes from the sides of the pharynx to the body- walls, on which the right and left lamellae become con- tinuous, so as to form the lining of the chamber into which the second aperture leads, or the 'atrial chamber.' Posteriorly, or at the opposite end of the atrial chamber to its aperture, its lining membrane (the ' atrial tunic ') is reflected to a greater or less extent over the intestine and circulatory organs 268 MANUAL OF ZOOLOGY. Where the atrial tunic is reflected over the sides of the pharynx, the two enter into a more or less complete union, and the sur- faces of contact become perforated by larger or smaller, more or less numerous, apertures. Thus the cavity of the pharynx acquires a free communication with that of the atrium ; and as the margins of the pharyngo-atrial apertures are fringed with cilia working towards the interior of the body, a current is produced, which sets in at the oral aperture and out by the atrial opening, and may be readily observed in a living Ascidian." — (Huxley.) As regards some points in the above description, Professor Allman does not agree with Huxley, but believes, on the other hand, " that the walls of the atrium simply surround the branchial sac, without being reflected on its sides, and that the branchial sac is therefore properly within the cavity of the atrium." In structure, the pharyngeal or " branchial " sac is composed of a series of longitudinal and transverse bars, which cross each other at right angles, and thus give rise to a series of quadrangular meshes, the margins of which are fringed with vibratile cilia. These bars are hollow, and are really vessels which open on each side into two main longitudinal sinuses, the so-called " branchial " or "thoracic" sinuses — one of which is placed along the haemal side of the pharynx, whilst the other runs along its neural aspect. The function of the entire perforated pharynx is clearly respiratory. The Tunicata possess a distinct heart, consisting of a simple muscular tube, which is open at both ends, and is not provided with valves. In consequence of this, the circulation in the majority of Tunicaries is periodically reversed, the blood being propelled in one direction for a certain number of con- tractions, and being then driven for a like period in an oppo- site direction ; " so that the two ends of the heart are alter- nately arterial and venous." The nervous system consists of a single ganglion placed on one side of the oral aperture, between it and the anus, in all known Tunicata, except in the aberrant form Appendicularia. The only organs of sense are pigment-spots, or ocelli, placed between the oral tentacles, and an auditory capsule, sometimes containing an otolith. These organs, however, do not appear to be constantly present. With the exception of Doliolum and Appendicularia, all the Tunicata are hermaphrodite. The reproductive organs are situated in the fold of the intestine, and their efferent duct opens into the atrium. The embryo Tunicate is at first gene- MOLLUSCOIDA: TUNICATA. 269 rally free, and is mostly shaped like the tadpole of a frog, swimming by means of a long caudal appendage. In one case the larval form appears to be destitute of a tail ; and in several instances the larval caudal appendage has been shown to ex- hibit a cylindrical rod-like body, which has been paralleled with the chorda dorsalis of Vertebrates. Amongst the Salpians a species of alternation of generations has been observed. A solitary Salpian produces long chains of embryos, which remain organically connected throughout their entire life. Each individual of these associated specimens produces solitary young, which are often very unlike their parents, and these again give rise to the aggregated forms. The Timicata are often spoken of as exhibiting three main types of structure, which give origin to as many sections, known respectively as the solitary, the social, and the compound forms. In the " solitary " Tunicaries, the individuals, however produced, remain entirely distinct, or, if not so primitively, they become so. In the " social " Ascidians the organism con- sists of a number of zooids, produced by gemmation and per- manently connected together by a vascular canal, or " stolon," composed of a prolongation of the common tunic, through which the blood circulates. Finally, in the " compound" forms, the zooids become aggregated into a common mass, their tests being fused together, but there being no internal union. HOMOLOGIES OF THE TUNICATA. — The general resemblance between a solitary Ascidian and a single polypide of a Polyzoon is extremely obvious ; each consisting of a double-walled sac, containing a freely suspended alimentary canal, with a distinct mouth and anus, and a nervous ganglion placed between the two. The chief feature in the Tunicata, as to the exact nature of which there is much difference of opinion, is the branchial or respiratory sac. By Professor Allman this is believed to be truly homologous with the tentacular crown of the Polyzoa, and the oral tentacles of the Tunicaries are believed to be something superadded, and not represented at all in the Polyzoa. By Professor Huxley, on the other hand, the branchial sac is looked upon as an enormously developed pharynx, and the oral tentacles are regarded as a rudimentary representative of the tentacular crown of the Polyzoa. Pro- bably the most correct view of the homologies of the Tunicata is taken by Rolleston, who regards the " branchial sac " as the homologue of the gills of the ordinary Bivalve Molluscs (La- mellibranchiatd], whilst the oral and atrial apertures are looked upon as corresponding to the respiratory apertures of these same animals. 270 MANUAL OF ZOOLOGY. DIVISIONS OF THE TUNICATA. — By Professor Huxley the following arrangement of the Tunicaries is adopted : — CLASS TUNICATA. Order I. Ascldia Branchialia. Branchial sac occupying the whole, or nearly the whole, length of the body ; intestine lying on one side of it. (AscitKada, Botryllus^ &>c.) Order II. Ascidia Abdominalia. Alimentary canal completely behind the branchial sac, which is comparatively small. (Clavellina, Doliolum, &*<:.) Order III. Ascidia Larvalia. Permanent larval form. (Appendicularia.} The following subdivisions are those adopted by Mr Wood- ward : — CLASS TUNICATA. Fam. I. Asddiadtz (Simple Ascidians). Animal simple, fixed, solitary, or gregarious ; oviparous ; sexes united ; branchial sac simple ; or disposed in (8 — 18) deep and regular folds. Fam. II. Clavellinida (Social Ascidians). Animal compound, fixed ; individuals connected by creeping tubular prolongations of the common tunic through which the blood circulates (or by a common gelatinous base). Reproduction effected by ova, or by gemmation from the common tube ; the new individuals remaining attached to the parent, or becoming completely free. Fam. III. Botryllida (Compound Ascidians). Animals compound, fixed, their tests fused, forming a common mass in which they are imbedded in one or more groups. Individuals not connected by any internal union ; oviparous and gemmiparous. Fam. IV. Pyrosomida. Animal compound, free and oceanic. Fam. V. Salpida. Animals free and oceanic ; alternately solitary and aggregated. CHAPTER XLIV. BRACHIOPODA. CLASS III. — BRACHIOPODA (Palliobranchiata). — The members of this class are defined by the possession of a body protected by a bivalve shell, which is lined by an expansion of the in- tegument, or " mantle." The mouth is furnished with two long cirriferous arms. The nervous system consists of a single ganglion, placed in the re-entering angle between the gullet and the rectum, so that the intestine has a " neural flexure." The Brachiopoda are essentially very similar in structure to MOLLUSCOIDA : BRACHIOPODA. 271 the Polyzoa^ from which they are distinguished by the fact that they are never composite, and by the possession of a bivalve, calcareous, or sub-calcareous shell. They are commonly known as " Lamp-shells," and are all inhabitants of the sea. All the living forms are fixed to some solid object in their adult condi- tion • but there is good reason to believe that many of the fossil forms were unattached and free in their fully-grown con- dition. From the presence of a bivalve shell, the Brachiopods have often been placed near the true bivalve Mollusca (the Lamellibranchiatd); but their organisation is very much inferior, and there are also sufficient .differences in the shell to justify their separation. The two valves of the shell of any Brachiopod are articulated together by an apparatus of teeth and sockets, or are kept in apposition by muscular action alone. One of the valves is always slightly, sometimes greatly, larger than the other, so that the shell is said to be " inequi valve." As regards the contained animal, the position of the valves is anterior and posterior, so that they are therefore term- ed respectively the "ventral" and "dorsal" valves. In the ordinary bivalve Mollusca (Lamellibranchiatd), on the other hand, the two valves of the shell are usually of the same size (equivalve), and they are situated upon the sides of the animal, so that, instead of being dorsal and ventral, they are now termed " right " and " left " valves. The ven- tral valve in the shell of the Brachiopoda is usually the largest, and usually possesses a pro- minent curved beak. The beak is sometimes perforated by a " foramen," or terminal aper- ture, through which there is transmitted a muscular peduncle, whereby the shell is at- tached to some foreign object. In some cases, however (as in Lingula, fig. 97), the peduncle simply passes between the apices of the valves, and there is no foramen ; whilst in others, as in Crania) the shell is merely attached by the substance of the ventral valve. The dorsal or smaller valve is always free, and is never perforated by a foramen. In intimate structure, the shell of most of the Brachiopoda consists " of flattened prisms, of considerable length, arranged parallel to one another with great regularity, and at a very Fig. 97. — Lingula anatina, showing the muscular ped- uncle by which the shell is attached. 2/2 MANUAL OF ZOOLOGY. acute angle — usually only about 10° or 12° — with the surfaces of the shell." — (Carpenter.) In most cases, also, the shell is perforated by a series of minute canals, which pass from one surface of the shell to the other, in a more or less vertical direction, usually widening as they approach the external surface. These canals give the shell a " punctated " structure, and in the living animal they contain caeca! tubuli, or pro- longations, from the mantle, which are considered by Huxley as analogous to the vascular processes by which in many Ascidians the muscular tunic, or " mantle," is attached to the outer tunic, or " test." In some of the Brachiopoda (as in the Rhynchonellidcz) the shell is " impunctate," or is devoid of this singular canal system. The inner surface of the valves of the shell is lined by ex- pansions of the integument which secrete the shell, and are called the " lobes " of the " pallium," or " mantle." The diges- tive organs and muscles occupy a small space near the beak of the shell, which is partitioned off by a membranous septum, which is perforated by the aperture of the mouth. The re- mainder of the cavity of the shell is almost filled by two long oral processes, which are termed the " arms," and from which the name of the class has been derived (fig. 98, i.) These organs are lateral prolongations of the margins of the mouth, usually of great length, closely coiled up, and fringed on one side with lateral processes, or " cirri." In many Brachiopods the arms are supported upon a more or less complicated inter- nal calcareous framework or skeleton, which is sometimes called the " carriage-spring apparatus." Fig. 98. — Brachiopoda ( Terebratula vitred). i. Showing the ciliated " arms ;" 2. Showing the shell with its loop. (After Woodward.) The mouth conducts by an oesophagus into a distinct stomach, surrounded by a well-developed granular liver. The intestine has a " neural flexure," and " either ends blindly in the middle line, or else terminates in a distinct anus between the pallial lobes." — (Huxley.)- MOLLUSCOIDA: BRACHIOPODA. 273 Within the pallial lobes there is a remarkable system of more or less branched tubes, anastomosing with one another, and ending in caecal extremities. This, which has been termed by Huxley the "atrial system," communicates with the peri visceral cavity by means of two or four organs which are called " pseudo-hearts," and which were at one time supposed to be true hearts. " Each pseudo-heart is divided into a narrow, elongated, external portion (the so-called ' ventricle ') which communicates, as Dr Hancock has proved, by a small apical aperture, with the pallial cavity ; and a broad, funnel- shaped, inner division (the so-called ' auricle ') communicating, on the one hand, by a constricted neck, with the so-called ' ventricle ; ' and, on the other, by a wide, patent mouth, with a chamber which occupies most of the cavity of the body proper, and sends more or less branched diverticula into the pallial lobes."— (Huxley.) This system of the atrial canals has been looked upon as a rudimentary respiratory apparatus ; but its function is more probably to act as an excretory organ, and also to convey away the reproductive elements, the organs for which are developed in various parts of its walls. By Woodward, the pseudo-hearts are regarded as oviducts, and it is stated that they have been found to contain mature ova, so that there can be little doubt but that this view of their nature is the correct one. By Rolleston the pseudo-hearts are looked upon as corresponding with the so-called " organ of Bojanus " of the Lamellibranchiata. The function of respiration is probably performed, mainly, if not entirely, by the cirriferous oral arms, as it appears chiefly to be by the homologous tentacular crown of the Polyzoa. A true vascular system and a distinct heart are present in some, at any rate, of the Brachiopoda, but this subject is still involved in considerable obscurity. In Terebratula the heart is in the form of a unilocular, pyriform vesicle, placed on the dorsal surface of the stomach. The nervous system consists of a principal ganglion, of no great size, placed in the re-entering angle between the gullet and the rectum. In those Brachiopods in which the valves of the shell are united by a hinge, the nervous system attains a greater development, and consists of a gangliated oesophageal collar. The sexes are said to be ordinarily distinct, but in some cases they appear to be united in the same individual. The development of the Brachiopoda is still shrouded in considerable obscurity, but in some cases the young have been observed to move from place to place, either by protruding their ciliated VOL. i. s 274 MANUAL OF ZOOLOGY. arms, or by means of spines developed in the ventral lobe of the mantle. By Huxley the Brachiopoda are divided into two groups, called respectively the Articulata and Inarticulata. In the former the valves of the shell are united along a hinge-line, the lobes of the mantle are not completely free, and the intestine ends caecally. In this group are the recent Tere- bratulidce and Rhynckortdlida. In the Inarticulata the valves of the shell are not united along a hinge-line, the mantle- lobes are completely free, and the intestine terminates in a distinct anus. In this group are the Craniadce, JDiscinidce, and LinguZidce. CLASSIFICATION OF THE BRACHIOPODA (AFTER DAVIDSON). CLASS BRACHIOPODA. Fam. I. Terebratulida. Shell minutely punctate ; ventral valve with a prominent beak perforated by a foramen for the emission of a muscular peduncle, whereby the animal is fixed to some solid object. Foramen partially surrounded by a deltidium of one or two pieces. Oral appendages entirely or partially supported by calcified processes, usually in the form of a loop, and always fixed to the dorsal valve. Genera. — Terebratula (with Terebratulina, and IValdheimid), Tere- bratella, Stringocephalus^ <2rY. Fam. II. Thecididce. Shell fixed to the sea-bottom by the beak of the larger or ventral valve ; structure punctated. Oral processes united in the form of a bridge over the visceral cavity ; cirrated arms folded upon themselves, and supported by a calcareous loop. Genus. — Thecidium. Fam. III. Spiriferidce. Animal free, or rarely attached by a muscular peduncle. Shell punctated or unpunctated. Arms largely developed, and entirely supported by a thin, shelly, spirally rolled lamella. Genera. — Spirifer^ Spiriferina, Cyrtia, Athyris, &>c. Fam. IV. Koninckida. Animal unknown. Shell free ; valves unarticulated (?). Oral arms supported by two lamellae, spirally coiled. Genus. — Koninckia. Fam. V. Rhynchonellidce. Animal free, or attached by a muscular peduncle issuing from an aperture situated under the extremity of the beak of the ventral valve. Arms spirally rolled, flexible, and supported only at their origin by a pair of short, curved, shelly processes. Shell-structure fibrous and impunctate. Genera. — Rhynchonella, Pentamerus, Porambonites, &>c. Fam. VI, Strophomenida. Animal unknown ; some probably free, others attached, during the whole or a portion of their existence, by a muscular peduncle. No calcified supports for the arms. Shell with a straight hinge-line, and a low triangular area in each valve. Shell-structure fibrous and punctated. Genera. — Orthis, Otthisina, Strophomena, and Lefihzna. MOLLUSCOIDA: DISTRIBUTION. 275 Fam. VII. Produciidce. Animal unknown. Shell entirely free, or attached to marine bottoms by the substance of the beak ; valves either regularly articulated, or kept in place by muscular action. No calcified support for the oral appendages. Genera. — Producta, Chonetes, Strophalosia, Aulosteges. Fam. VIII. Calceolida* Animal unknown. Shell probably free ; valves not articulated ; ventral valve pyramidal, with a large, flat, triangular area ; dorsal valve flat, semicircular, with a straight hinge-line. No foramen, or muscular or vascular impressions. Genus. — Calceola. Fam. IX. CraniadcB. Animal fixed to submarine objects by the substance of the shell of the ventral valve. Arms fleshy and spirally coiled ; no hinge or articulating processes ; upper or dorsal valve patelliform (i.e. limpet- shaped). Genus. — Crania. Fam. X. Disdnida. Animal attached by means of a muscular peduncle passing through the ventral or lower valve by means of a slit in its hinder portion or a circular foramen excavated in its substance. Arms fleshy, valves unarticulated. Genera. — Discina, Trematis, Siphonotreta, Acrotreta. Fam. XI. Lingulidce. Animal fixed by a muscular peduncle passing out between the beaks of the valves ; arms fleshy, unsupported by calcified processes. Shell unarticulated, sub-equivalve, texture horny. Genera. — Lingula, Obolus. CHAPTER XLV. DISTRIBUTION OF MOLLUSCOIDA. DISTRIBUTION OF MOLLUSCOIDA IN SPACE. — The Polyzoa, like all the Molluscoida, are exclusively aquatic in their habits, but, unlike the remaining two classes, they are not exclusively con- fined to the sea. The marine Polyzoa are of almost universal occurrence in all seas. The fresh-water Polyzoa, however, not only differ materially from their marine brethren in structure, but appear to have a much more limited range, being, as far as is yet known, confined to the north temperate zone. Britain can claim the great majority of the described species of fresh- water Polyzoa, but this is probably due to the more careful scrutiny to which this country has been subjected. * Recent researches have thrown some doubt upon the position of Calceola amongst the Brachiopoda, and have tended to show that it is a very abnormal type of Rugose Coral, provided with a lid or operculum. 2/6 MANUAL OF ZOOLOGY. The Tunicata are cosmopolitan in their distribution, and are found in all seas, the Mediterranean appearing to be especially rich in members of this class. Four genera are pelagic in their habits, and several are found in the Arctic regions. The Brachiopoda, though of very partial occurrence, have a wide range in space, being found both in tropical seas and in the Arctic Ocean. Their bathymetrical range is also very wide, extending from the littoral zone, almost to the greatest depths at which animal life has hitherto been detected. DISTRIBUTION OF MOLLUSCOIDA IN TIME. — The Polyzoa have left abundant traces of their past existenceln the stratified series, commencing in the Lower Silurian Rocks and extending up to the present day. The Oldhamia of the Cambrian Rocks of Ireland, and the Graptolites have been supposed to belong to the Polyzoa, but the former is very possibly a plant, and the latter should be referred to the Hydrozoa. Of undoubted Po- lyzoa, the marine orders of the Cheilostomata and Cyclostomata are alone known with certainty to be represented. Several Palaeozoic genera — such as Fenestella (the Lace-coral), Ptilo- dictya, Ptilopora, &c. — are exclusively confined to this epoch, and do not extend into the Secondary Rocks. Amongst the Mesozoic formations, the Chalk is especially rich in Polyzoa, over two hundred species having been already described from this horizon alone. In the Tertiary period, the Coralline Crag (Pleiocene) is equally conspicuous for the great number of the members of this class. The Tunicata, from the nature of their bodies, are not known to occur in a fossil condition. The Brachiopoda are found from the Cambrian Rocks up to the present day, and present us with an example of a group which appears to be slowly dying out. Nearly two thousand extinct species have been described, and the class appears to have attained its maximum in the Silurian epoch, which is, for this reason, sometimes called the " Age of Brachiopods." Numerous genera and species are found also in both the Devonian and Carboniferous formations. In the Secondary Rocks Brachiopoda are still abundant, though less so than in the Palaeozoic period. In the Tertiary epoch a still further diminution takes place, and at the present day we are not acquainted with a hundred living forms. Of the families of Brachiopoda, the Productidce, Strophomenida, and Spiriferidcz are the more important extinct types. Of the genera, the most persistent is the genus Lingida, which commences in the Cam- brian Rocks, and has maintained its place up to the present day, though it appears to be gradually dying out. MOLLUSCOIDA: DISTRIBUTION. 277 According to Woodward : — " The hingeless genera attained their maximum in the Palaeozoic age, and only three now sur- vive (Lingula, Distina, Crania] — the representatives of as many distinct families. Of the genera with articulated valves, those provided with spiral arms appeared first, and attained their maximum while the Terebratulidcz were still few in number. The subdivision with calcareous spires disappeared with the Liassic period, whereas the genus Rhynchonella still exists. Lastly, the typical group, Terebratulidce, attained its maximum in the Chalk period and is scarcely yet on the decline." 2/8 MANUAL OF ZOOLOGY. MOLLUSC A PROPER. CHAPTER XLVI. LAMELLIBRANCHIA TA. DIVISION II. MOLLUSCA PROPER. — This division includes those members of the sub-kingdom Mollusca in which the nervous system consists of three, principal pairs of ganglia; and there is always a well-developed heart, which is never composed of fewer than two chambers. The Mollusca proper may be roughly divided into two great sections, respectively termed the Acephala and the Encephala (or Cephalophora], characterised by the absence or presence of a distinctly differentiated head. The headless, or Acephalous, Molluscs correspond to the class Lamellibranchiata ; also dis- tinguished, at first sight, by the ' possession of a bivalve shell. The Encephalous Molluscs are more highly organised, and are divided into three classes — viz., the Gasteropoda, the Pteropoda, and the Cephalopoda. The shell in these three classes is of very various nature, but they all possess a singular and com- plicated series of lingual teeth ; hence they are grouped to- gether by Professor Huxley under the name of Odontophora. CLASS I. LAMELLIBRANCHIATA, or CONCHIFERA. — The members of this class are characterised by the absence of a distinctly differentiated head, and by having the body more or less completely protected in a bivalve shell. There are two lamellar gills on each side of the body, the intestine has a neural flexure, and there is no odontophore. The Lamellibranchiata are commonly known as the bivalve shell-fish, such as Mussels, Cockles, Oysters, Scallops, &c., and they are all either marine or inhabitants of fresh water. Though they agree with the Brachiopoda in possessing a shell which is composed of two pieces or valves, there are, nevertheless, many points in which the shell of a Lamelli- branch is distinguishable from that of a Brachiopod, irrespec- tive of the great difference in the structure of the animal in MOLLUSCA: LAMELLIBRANCHIATA. 279 each. The shell in the Brachiopoda, as we have seen, is rarely or never quite equivalve, and always has its two sides equally developed (equilateral); whilst the valves are placed antero- posteriorly as regards the animal, one in front and one behind, so that they are "dorsal" and " ventral." In the Lamellibran- chiata, on the other hand, the two valves are usually of nearly equal size (equivalve), and are more developed on one side than on the other (inequilateral) ; whilst their position as re- gards the animal is always lateral, so that they are properly termed "right" and "left" valves, instead of "ventral" and "dorsal." The following are the chief points to be noticed in connec- tion with the shell of any Lamellibranch : Each valve of the shell may be regarded as essentially a hollow cone, the apex of which is turned more or less to one side ; so that more of the shell is situated on one side of the apex than on the other. The apex of the valve is called the " umbo," or " beak," and is always turned towards the mouth of. the animal. Conse- quently, the side of the shell towards which the umbones are turned is the "anterior" side, and it is usually the shortest half of the shell. The longer half of the shell, from which the umbones turn away, is called the " posterior" side, but in some cases this is equal to, or even shorter than, the anterior side. The side of the shell where the beaks are situated, and where the valves are united to one another, is called the "dorsal" side, and the opposite margin, along which the shell opens, is called the " ventral" side, or " base." The length of the shell is measured from its anterior to its posterior margin, and its breadth from the dorsal margin to the base. At the dorsal margin the valves are united to one another, for a shorter or longer distance, along a line which is called the "hinge-line." The union is effected in most shells by means of a series of parts which interlock with one another (the " teeth"), but these are sometimes absent, when the shell is said to be "edentulous." Posterior to the umbones, in most bivalves, is another structure passing between the valves, which is called the " ligament," and which is usually composed of two parts, either distinct or combined with one another. These two parts are known as the " external ligament " (or the liga- ment proper) and the "cartilage," and they constitute the agency whereby the shell is opened, but one or other of them may be absent. The ligament proper is outside the shell, and consists of a band of horny fibres, passing from one valve to the other just behind the beaks, in such a manner that it is put upon the stretch when the shell is closed. The cartilage, or 280 MANUAL OF ZOOLOGY. internal ligament, is lodged between the hinge-lines of the two valves, generally in one or more " pits," or in special processes of the shell. It consists of elastic fibres placed perpen- dicularly between the surfaces by which it is contained, so that they are necessarily short- ened and compressed when the valves are shut. To open the shell, therefore, it is simply necessary for the animal to relax the muscles which are provided for the closure of the valves, whereupon the elastic force of the ligament and car- tilage is sufficient of itself to open the shell. The body in the Lamelli- branchiata is always enclosed in an expansion of the dorsal integument, which constitutes the "mantle," or "pallium," whereby the shell is secreted. The lobes of the mantle are right and left, and not anterior and posterior as are the mantle- lobes of the Brachiopoda. To- wards its circumference the mantle is more or less com- pletely united to the shell, leaving in its interior, when the soft parts are removed, a more or less distinctly impres- sed line, which is called the "pallial line," or "impression" (fig. TOO). There is no distinctly diffe- rentiated head in any of the Lamdlibranchiata, and the mouth is simply placed at the anterior extremity of the body. It is furnished with membran- ous processes or "palpi" (usu- ally four in number), but there is no dental apparatus. The mouth opens into a gullet, which conducts to a distinct Fig. 99. — Anatomy of a bivalve Mollusc (Mya arenaria). The left valve and mantle-lobe and half the siphons are re- moved. ^ J Respiratory siphons, the arrows indicating the direction of the currents ; a a' Adductor muscles ; b Gills ; h Heart ; o Mouth, surrounded by (/) labial palpi ; /Foot ; v Anus ; m Cut edge of the mantle. (After Woodward.) MOLLUSCA: LAMELLIBRANCHIATA. 281 stomach. On the right side of the stomach, and opening into it, is, in many cases, a blind sac containing a peculiar transparent glassy body, which is known as the u crystalline stylet," but the functions of which are absolutely unknown. The intestine has its first flexure neural, perforates the wall of the heart, and terminates posteriorly in a distinct anus, which is always placed near the respiratory aperture. The liver is large and well developed, but there are no salivary glands. There is always a distinct heart, composed either of an auricle and ventricle, or of two auricles and a ventricle. The ventricle propels the blood into the arteries, by which it is dis- tributed through the body. From the arteries it passes into the veins, and is conducted to the gills, where it is aerated, and is finally returned to the auricles. The respiratory organs in all the Lamellibranchiata consist of two lamelliform gills, placed on each side of the body (fig. 99, b\ In some cases there is only one gill on each side of the body, the external pair of branchise being absent. The gills are in the form of membranous plates, composed usually of tubular rods, which support a network of capillary vessels, and are covered with vibrating cilia, whereby a circulation of the water is maintained over their surfaces. In some bivalves the margins of the mantle are united to one another, so that a closed branchial chamber is produced; and in the others the arrangements for the admission of fresh and the expulsion of effete water are equally perfect, though there is no such cham- ber. In those in which the mantle-lobes are united at their margins, there are two orifices, one of which serves to admit fresh water, whilst the effete water is expelled by the other. The margins of these " inhalant " and " exhalant " apertures are often drawn out and extended into long muscular tubes or " siphons," which may be either free, or may be united to one another along one side (fig. 99, s s), and which can usually be partially or entirely retracted within the shell by means of special muscles, called the " retractor- muscles of the siphons." These siphons are more especially characteristic of those La- mellibranchs which spend their existence buried in the sand, protruding their respiratory tubes in order to obtain water, and with it such nutrient particles as the water may contain. The presence or absence of retractile siphons can be readily deter- mined merely by inspection of the dead shell. In those bi- valves in which siphons are not present, or if present are not retractile, the "pallia! line" in the interior of the shell is un- broken in its curvature, and presents no indentation (Integro- pallialid). In those, on the other hand, in which retractile 282 MANUAL OF ZOOLOGY. siphons exist, the pallial line does not run in an unbroken curve, but is deflected inwards posteriorly, so as to form an indentation or bay, which is termed the " pallial sinus," or " siphonal impression," and is caused by the insertion of the retractor-muscle of the siphon. Those bivalves in which this sinus exists form the section Sinu-pallialia (fig. 100, 2). Fig. 100. — Shells of Lamellibranchiata. i. Cyclas amnica, a dimyary shell with an entire pallial line. 2. Tapes pullastra, a dimyary shell with an indented pallial line. 3. Perna. ephippium, a monomyary shell. (After Woodward ) a Pallial line; b Muscular impressions left by the adductors ; c Siphonal impression. The nervous system of the Lamellibranchiata is composed of the three normal ganglia — the cephalic, the pedal, and the parieto-splanchnic or branchial. The so-called " organ of Bojanus" of the Bivalves is doubtless mainly concerned in excretion, and in all probability represents the kidney. There is one of these organs on each side of the body, each com- posed of two sacs separated from those of the opposite side by a venous sinus. Or it may be looked upon as a double organ composed of two bilaterally symmetrical halves. It is situated just below the " pericardium," and communicates with it and also with the mantle-cavity. Though undoubtedly per- forming the functions of a kidney, the organ of Bojanus is also connected in some cases with reproduction, and it appears to correspond to the " pseudo-hearts " of the Brachiopoda. The majority of the bivalves are dioecious, but in some the sexes are united in the same individual. The young are hatched before they leave the parent, and are, when first libe- rated, ciliated and free-swimming. The muscular system of the Lamellibranchs is well deve- loped. Besides the muscular margin of the mantle, and the muscles of the siphons (when these exist), there are also pre- sent other muscles, of which the most important are the mus- cles which close the shell and those which form the " foot " (fig. 99,/). The "foot" is present in the majority of bivalves, though it is not such a striking feature as in the Gasteropoda. MOLLUSCA : LAMELLIBRANCHIATA. 283 It is essentially a muscular organ, developed upon the ventral surface of the body, its retractor-muscles usually leaving dis- tinct impressions or scars (the "pedal impressions") in the interior of the shell. In many the foot subserves locomotion, but in the attached bivalves it is rudimentary, and in others (as in the Scallops) locomotion is effected by the alternate opening and closure of the valves. In some — such as the ordinary Mussel — the foot is subsidiary to a special gland, which secretes the tuft of silky threads ("byssus") whereby the shell is at- tached to foreign objects. This gland secretes a viscous material, which the foot moulds into threads. The valves of the shell are brought together by one or two muscles, which are called the " adductor muscles " — those bivalves with only one being called Monomyaria, whilst those which possess two are termed Dimyaria. In most there are two adductor muscles (fig. 99, a a) passing between the inner surfaces of the valves, one being placed anteriorly in front of the mouth, the other posteriorly on the neural side of the intes- tine. In the monomyary bivalves the posterior adductor is the one which remains, and the anterior adductor is absent. The adductors leave distinct " muscular impressions " in the interior of the shell, so that it is easy to determine whether there has been one only in any given specimen, or whether two were present. The habits of the Lamellibranchiata are very various. Some, such as the Oyster (Ostrea), and the Scallop (Pecten\ habit- ually lie on one side, the lower valve being the deepest, and the foot being wanting, or rudimentary. Others, such as the Mussel (Mytilus), and the Pinna, are attached to some foreign object by an apparatus of threads, which is called the "byssus," and is secreted by a special gland. Others are fixed to some solid body by the substance of one of the valves. Many, such as the Myas, spend their existence sunk in the sand of the sea- shore or in the mud of estuaries. Others, as the Pholades and Lithodomi) bore holes in rock or wood, in which they live. Finally, many are permanently free and locomotive. The Lamellibranchiata are divided into two sections, accord- ing as respiratory siphons are absent or present, as follows : — SECTION A. ASIPHONIDA. — Animal without respiratory siphons; mantle-lobes free; the pallial line simple and not indented (Integro-pallialia). This section comprises the families Ostreida, Aviculidce, My- tilidce, Arcadcz, Trigoniadce, and Unionidce. SECTION B. SIPHONIDA. — Animal with respiratory siphons ; mantle-lobes more or less united. 284 MANUAL OF ZOOLOGY. Two subdivisions are comprised in this section. In the first the siphons are short, and the pallial line is simple (Integro- pallialia] ; as is seen in the families Chamidtz, Hippuritidcz, Tridacnidcz, Cardiadce, Lucinida, Cycladidcz, and Cyprinida. The second subdivision (Sinu-pallialid] is distinguished by the possession of long respiratory siphons, and a sinnated pallial line, and it comprises the families Veneridce, Mactridce, Tellinidce, Solenidce, Myacidcz, Anatinidce, Gastrochtznidcz, and PholadidcR. SYNOPSIS OF THE FAMILIES OF THE LAMELLIBRANCHIATA. SECTION A. ASIPHONIDA. Fam. i. Ostreidce. — Shell inequivalve, slightly inequilateral, free or attached; hinge usually edentulous. Ligament internal. Lobes of the mantle entirely separated ; the foot small and byssi- ferous, or wanting. A single adductor. 111. Gen. Ostrea, Pecten, Spondylus, &c. Fam. 2. Aviculidce. — Shell, inequivalve, very oblique, attached by a byssus ; hinge nearly, or quite, edentulous. Mantle-lobes free ; anterior adductor small, leaving its impression within the umbo ; posterior adductor large and sub-central. Foot small. 111. Gen. Avicula, Inoceramus, Pinna. Fam. 3. Mytilida. — Shell equivalve, umbones anterior, hinge eden- tulous ; anterior muscular impression small, posterior large. Shell attached by a byssus. Mantle-lobes united between the siphonal apertures. Foot cylindrical, grooved, and byssiferous. 111. Gen. Mytilus, Modiola, Dreissena. Fam. 4. Arcades. — Shell equivalve ; hinge long, with many comb- like equal teeth. Muscular impressions nearly equal. Mantle- lobes separated ; foot large, bent, and deeply grooved. 111. Gen. Area, Pectunculus, Cucullcea. Fam. 5. Trigoniadce. — Shell equivalve, trigonal ; hinge-teeth few, diverging ; umbones directed posteriorly. Mantle open ; foot long and bent. 111. Gen. Trigonia, Axinus. Fam. 6. Unionidce. — Shell usually equivalve, with a large external ligament. Anterior hinge-teeth thick and striated ; posterior laminar, or wanting. Mantle-lobes united between the siphonal apertures. Foot very large, compressed, byssiferous in the fry. 111. Gen. Unto, Anodon, Miilleria. SECTION B. SIPHONIDA. — Subdivision I. Integro-pallialia. — Siphons short, pallial line simple. Fam. 7. Chamida— Shell inequivalve, attached ; hinge-teeth 2-1 (two in one valve and one in the other). Adductor impressions large. Mantle closed ; pedal and siphonal orifices small and nearly equal. Foot very small. 111. Gen. Chama, Diceras. Fam.%. Hippuritida. — "Shell inequivalve, unsymmetrical, thick, attached by the right umbo ; umbones frequently camerated ; structure and sculpturing of valves dissimilar ; ligament internal ; hinge-teeth 1-2 ; adductor impressions 2, large, those of the left valve on prominent apophyses ; pallial line simple, sub-marginal." — (Woodward.) 111. Gen. Hippurites, Radiolites, Caprinella. Fam. 9. Tridacnidcz. — Shell equivalve ; ligament external ; muscular impressions blended, sub-central. Animal attached by a byssus, MOLLUSCA : LAMELLIBRANCHIATA. 285 or free. Mantle-lobes extensively united ; pedal aperture large ; siphonal orifices surrounded by a thickened pallial border. Foot finger-like and byssiferous. 111. Gen. Tridacna. Fam. 10. Cardiadce. — Shell equivalve, heart-shaped, with radiating ribs ; cardinal teeth 2 ; lateral teeth i-i, in each valve. Mantle open in front, siphons usually very short ; foot large, sickle - shaped. 111. Gen. Cardium, Hemicardium^ Conocardium, Fam. II. Ludnida. — Shell orbicular, and free; hinge-teeth I or 2; lateral teeth i-i, or obsolete. Mantle-lobes open below, with one or two siphonal orifices behind ; foot elongated, cylindrical, or strap-shaped. 111. Gen. Ludna, Diplodonta, Kellia. Fam. 12. Cydadidcz. — Shell sub-orbicular, closed; hinge with cardinal and lateral teeth; ligament external. Mantle open in front; 1-2 siphons, more or less united. Foot large, tongue- shaped. 111. Gen. Cyclas, Cyrena. Fam. 13. Cyprinida. — Shell equivalve, closed; ligament external ; cardinal teeth 1-3 in each valve, and usually a posterior tooth. Mantle-lobes united behind by a curtain pierced with two siphonal orifices. Foot thick, and tongue-shaped. 111. Gen. Cyprina, Astarte, Isocardia. Subdivision II. Sinu-pallialia . — Respiratory siphons large; pallial line sinuated. Fam. 14. Veneridce. — Shell regular, sub-orbicular or oblong ; liga- ment external ; hinge with usually 3 diverging teeth in each valve. Animal usually free and locomotive ; mantle with a rather large anterior opening ; siphons unequal, more or less united. Foot tongue-shaped, compressed, sometimes grooved and byssiferousj. 111. Gen. Venus, Cytherea, Vcnerupis. Fam. 15. Mactridtz. — Shell equivalve, trigonal ; hinge with two diverging cardinal teeth, and usually with anterior and posterior lateral teeth. Mantle more or less open in front ; siphons united, with fringed orifices ; foot compressed. 111. Gen. Mactra, Lutraria. Fam. 16. Tellinidce. — Shell free, usually equivalve and closed; cardinal teeth 2 at most, laterals i-i, sometimes wanting. Liga- ment on the shortest side of the shell, sometimes internal. Mantle widely open in front. Siphons separate, long and slender ; foot tongue-shaped, compressed. 111. Gen. Tellina, Psammobia, Donax. Fam. 17. Solenida. — Shell elongated, gaping at both ends; ligament external ; hinge-teeth usually 2-3. Siphons short and united (in the long-shelled genera), or longer and partly separate (in the genera with shorter shells). Foot very large and powerful. Gills prolonged into the branchial siphon. 111. Gen. Solen, Cultellus, Solecurtus. Fam. 1 8. Myadda. — Shell gaping posteriorly. Mantle almost entirely closed ; siphons united, partly or wholly retractile. Foot very small. 111. Gen. Afya, Panopcea, Glycimeris. Fam. 19. Anatinidce. — Shell often inequivalve, with an external ligament. Mantle-lobes more or less united ; siphons long, more or less united. Foot small. 111. Gen. Anatina, Pholadomya, Myochama. Fam. 20. GasirochanicUe. — Shell equivalve, gaping, with thin eden- tulous valves, sometimes cemented to a calcareous tube. Mantle- margins thick in front, united, with a small pedal aperture. 286 MANUAL OF ZOOLOGY. Siphons very long, united. Foot finger-shaped. 111. Gen. Gastro- chcena, Saxicava, Aspergillum. Fam. 21. Pholadidce. — Shell gaping at both ends, without hinge or ligament, often with accessory valves. Animal club-shaped or worm-like, with a short, truncated foot. Mantle closed in front. Siphons long, united to near their extremities. 111. Gen. Pholast Xylophaga,) Teredo. CHAPTER XLVII. GASTEROPODA. DIVISION ENCEPHALA, or CEPHALOPHORA. — The remaining three classes of the Mollusca proper all possess a distinctly- differentiated head, and are all provided with a peculiar masti- catory apparatus, which is known as the " odontophore." For the first of these reasons they are often grouped together under the name Encephala ; and for the second reason they are united by Huxley into a single great division, under the name of Odonlophora. Whichever name be adopted, the three classes in question (viz., the Gasteropoda, Pteropoda, and Cephalopoda) certainly show many points of affinity, and form a very natural division of the Mollusca. The Pteropoda, as being the lowest class, should properly be treated of first, but it will conduce to a clearer understanding of their characters if the Gasteropoda are considered first. CLASS II. GASTEROPODA. — The members of this class are characterised by being never included in a bivalve shell ; loco- motion being effected by means of a broad, horizontally flat- tened, ventral disc — the " foot " — or by a vertically flattened, ventral, fin-like organ. Flexure of intestine haemal or neural. This class includes all those Molluscous animals which are commonly known as " univalves," such as the land-snails, sea- snails, whelks, limpets, &c. The shell, however, is sometimes composed of several pieces (multivalve), and in many there is either no shell at all, or nothing that would be generally recognised as such. In none is there a bivalve shell. In their habits the Gasteropods show many differences, some being sedentary, but the great majority being free and locomotive. In these latter, locomotion may be effected by the successive contractions and expansions of a muscular foot ; but some possess the power of swimming freely by means of a modified fin-like foot. MOLLUSCA : GASTEROPODA. 287 In most of the Gasteropoda the body is unsymmetrical, and is coiled up spirally, " the respiratory organs of the left side being usually atrophied." — (Woodward.) The body is enclosed in a "mantle," which is not divided into two lobes as in the Lamel- libranchiata, but is continuous round the body. Locomotion is effected by means of the " foot," which is usually a broad muscular disc, developed upon the ventral surface of the body, and not exhibiting any distinct division into parts. In the Heteropoda, however, and in the Wing-shells (Strombidce), the foot exhibits a division into three portions — an anterior, the " propodium ; " a middle, the " mesopodium j" and a posterior lobe, or "metapodium." In some, again, the upper and lateral surfaces of the foot are expanded into muscular side-lobes, which are called " epi- podia." In many cases the metapodium, or posterior portion of the foot, secretes a calcareous, horny, or fibrous plate, which is called the " operculum" (fig. 102, 0), and which serves to close the orifice of the shell when the animal is retracted within it. The head in most of the Gasteropoda is very distinctly marked out, and is provided with two tentacles and with two eyes, which are often placed upon long stalks. The mouth is sometimes furnished with horny jaws, and is always provided with a singular masticatory apparatus, called the " tongue " or " odontophore " (fig. 101). " It consists essentially of a carti- laginous cushion, supporting, as on a pulley, an elastic strap, which bears a long series of transversely-dis- posed teeth. The ends of the strap are con- nected with muscles attached to the upper and lower surface of the hinder extremities of the cartilaginous cushions ; and these muscles, by their alternate contractions, cause the toothed strap to work backwards and forwards over the end of the pulley formed by its ante- rior end. The strap consequently acts, after the fashion of a chain-saw, upon any substance to which it is applied, and the resulting wear and tear of its anterior teeth are made good by ~ '!' ,1 i _ ° , .-' rig. 101. — r ragment the incessant development of new teeth in of the lingual nb- the secreting sac in which the hinder end of ^ °of thlcoSl the strap is lodged." — (Huxley.) The teeth of mon Whelk (&*#• the odontophore ("lingual teeth") are com- S£ffiX(Afti posed of silica, and are usually arranged in a Woodward.) central (" rachidian ") and two lateral (" pleural ") rows. The mouth leads by a gullet into a distinct stomach, which is 288 MANUAL OF ZOOLOGY. sometimes provided with calcareous plates for the trituration of the food. The intestine is long, and its first flexure is commonly "haemal," or towards that side of the body on which the heart is situated ; though in some the flexure is "neural." Distinct salivary glands are usually present, and the liver is well developed. A distinct heart is usually present, composed of an auricle and ventricle. Respiration is very variously effected ; one great division (Branchiogasteropoda) being constructed to breathe air by means of water ; whilst in another section (Pulmogas- teropodd) the respiration is aerial. In the former division res- piration may be effected in three ways. Firstly, there may be no specialised respiratory organ, the blood being simply ex- posed to the water in the thin walls of the mantle-cavity (as in some of the Heteropoda). Secondly, the respiratory organs may be in the form of outward processes of the integument, exposed in tufts on the back and sides of the animal (as in the Nudibranchiata], Thirdly, the respiratory organs are in the form of pectinated or plume-like branchiae, contained in a more or less complete branchial chamber formed by an inflec- tion of the mantle. In many members of this last section the water obtains access to the gills by means of a tubular prolon- gation or folding of the mantle, forming a " siphon," the effete water being expelled by another posterior siphon similarly con- structed. In the air-breathing Gasteropods, the breathing- organ is in the form of a pulmonary chamber, formed by an inflection of the mantle, and having a distinct aperture for the admission of air. Fig. 102. — Ampullaria canaliculata, one of the Apple-shells, o Operculum ; ^ Respiratory siphon. The nervous system in the Gasteropoda has its normal com- position of three principal pairs of ganglia, the supra-oesopha- MOLLUSCA : GASTEROPODA. 289 geal or cerebral, the infra-cesophageal or pedal, and the parieto- splanchnic ; but there is a tendency to the aggregation of these in the neighbourhood of the head. The organs of sense are the two eyes, and auditory capsules placed at the bases of the tentacles, the latter being tactile organs. The sexes are mostly distinct, but in some they are united in the same individual. The young, when first hatched, are always provided with an embryonic shell, which in the adult may become concealed in a fold of the mantle, or may be entirely lost. In the branchiate Gasteropods the embryo is protected by a small nautiloid shell, within which it can en- tirely retract itself; and it is enabled to swim freely by means of two ciliated lobes arising from the sides of the head ; thus, in many respects, resembling the permanent adult condition of the Pteropoda. Shell of the Gasteropoda, — The shell of the Gasteropods is composed either of a single piece (univalve), or of a number of plates succeeding one another from before backwards (mul- tivalve). The univalve shell is to be regarded as essentially a cone, the apex of which is more or less oblique. In the simplest form of the shell the conical shape is retained without any alteration, as is seen in the common Limpet (Patella}. In the great majority of cases, however, the cone is consider- ably elongated, so as to form a tube, which may retain this shape (as in Dentalium\ but is usually coiled up into a spiral. The "spiral univalve" (fig. 103) may, in fact, be looked upon as the typical form of the shell in the Gasteropoda. In some cases the coils of the shell — termed technically the " whorls " — are hardly in contact with one another (as in Vermetus). More commonly the whorls are in contact, and are so amalga- mated that the inner side of each convolution is formed by the pre-existing whorl. In some cases the whorls of the shell are coiled round a central axis in the same plane, when the shell is said to be "discoidal" (as in the common fresh- water shell Planorbis). In most cases, however, the whorls are wound round an axis in an oblique manner, a true spiral being formed, and the shell becoming " turreted," " trochoid," " turbinated," &c. This last form is the one which may be looked upon as most characteristic of the Gasteropods, the shell being composed of a number of whorls passing obliquely round a central axis or " columella," having the embryonic shell or "nucleus" at its apex, and having the mouth or "aperture" of the shell placed at the extremity of the last and largest of the whorls, termed the " body-whorl." The lines or grooves formed by the junction of the whorls are termed the " sutures," VOL. I. T 2QO MANUAL OF ZOOLOGY. and the whorls above the body-whorl constitute the " spire " of the shell. The axis of the shell (columella) round which the whorls are coiled is usually solid, when the shell is said to be " imperforate ; " but it is sometimes hollow, when the shell is said to be " perforated," and the aperture of the axis near the mouth of the shell is called the " umbilicus." The margin of the "aperture" of the shell is termed the "peristome," and is composed of an outer and inner lip, of which the former is often expanded or fringed with spines. When these expan- sions or fringes are periodically formed, the place of the mouth of the shell at different stages of its growth is marked by ridges or rows of spines, which cross the whorls, and are called " varices." In most of the phytophagous Gasteropods (Holo- stomata) the aperture of the shell (fig. 103, a) is unbrokenly round or " entire," but in the carnivorous forms (Siphonosto- mata) it is notched, or produced into a canal (fig. 103, b). Often there are two of these canals, an anterior and a posterior, but they do not necessarily indicate the nature of the food, as their function is to protect the respiratory siphons. The animal withdraws into its shell by a retractor-muscle, which passes into the foot, or is attached to the operculum ; its scar or impression being placed, in the spiral univalves, upon the columella. In the multivalve Gasteropods, the shell is composed of eight transverse imbricated plates, which succeed one another from before backwards. CHAPTER XLVIII. DIVISIONS OF THE GASTEROPODA. THE Gasteropoda are divided into two primary sections or sub-classes, according as the respiratory organs are adapted for breathing air directly, or dissolved in water: termed re- spectively the Pulmonifera or Pulmogasteropoda, and the Branchifera or Branchiogasteropoda. SUB-CLASS A. BRANCHIFERA or BRANCHIOGASTEROPODA. — In this sub-class respiration is aquatic, effected by the thin walls of the mantle-cavity, by external branchial tufts, or by pectinated or plume -like gills, contained in a more or less complete branchial chamber. Flexure of intestine hamal. This sub-class comprises three orders — viz., the Proso- MOLLUSCA : GASTEROPODA. 29I branchial^ the Opisthobranchiata, and the Nudeobranchiata or Heteropoda. ORDER I. PROSOBRANCHIATA. — The members of this order are defined as follows : — " Abdomen well developed, and pro- tected by a shell, into which the whole animal can usually retire. Mantle forming a vaulted chamber over the back of the head, in which are placed the excretory orifices, and in which the branchiae are almost always lodged. Bronchia pectinated or plume-like, situated (prosori) in advance of the heart. Sexes distinct." — M.-Edwards. (See Woodward's ' Manual.') The order Prosobranchiata includes all the most character- istic members of the Branchiate Gasteropods, and is divisible into two sections, termed respectively Siphonostomata and Holostomata, according as the aperture of the shell is notched or produced into a canal, or is simply rounded and " entire." The Siphonostomata, of which the common Whelk (Bucci- num undatum} may be taken as an example, are all marine, and are mostly carnivorous in their habits. The following families are comprised in this section : — Strombidce (Wing- shells), Muritidce, Buccinida (Whelks), Conida (Cones), Volu- tida, and Cypraida (Cowries). The Holostomata, of which the Common Periwinkle (Litto- Fig. 103. — Gasteropoda, a Holostomatous shell ( Turri fella communis] \ b Siphonostomatous shell (Buccinum undatuni). rina littorea) is a good example, are either spiral, or limpet- shaped, in some few instances tubular, or multivalve ; the aper- ture of the shell being in most cases entire. They are mostly 2Q2 MANUAL OF ZOOLOGY. plant-eaters, and they may be either marine or inhabitants of fresh water. The following families are included in this sec- tion : — Natitidcz, Pyramidellidce, Cerithiada, Melaniada, Turri- tellidcz, Littorinidcz (Periwinkles), Paludinida (River- snails), Neritidce, Turbinida (Top-shells), Haliotidcz (Ear-shells), Fis- surellida (Key-hole Limpets), CalyptrceidcB (Bonnet Limpets), PatdlidcR (Limpets), Dentalidce (Tooth-shells), and Chitonida. ORDER II. OPISTHOBRANCHIATA. — This order is denned as follows : — " Shell rudimentary, or wanting. Branchicz arborescent or fasciculated, not contained in a special cavity, but more or less completely exposed on the back and sides, towards the rear (opisthen) of the body. Sexes united." — M.-Edwards. (See Woodward's ' Manual.') The Opisthobranchiata, or " Sea-slugs," may be divided into two sections, the Tectibranchiata and Nudibranchiata, accord- ing as the branchiae are protected or are uncovered. The first section, that of the Tectibranchiata, is distinguished by the fact that the animal is usually provided with a shell, both in the larval and adult state, and that the branchiae are protected by the shell or by the mantle. Under this family are included the families of the Tornatellidce, Bullidcz (Bubble- shells), Aplysiada (Sea-hares), Pleurobranchidcz and Phyllidiada. In the second section, that of the Nudibranchiata (fig. 104), the animal is destitute of a shell, except in the embryo condition, and the branchiae are always placed externally on the back or sides of the body. This section com- prises the families Doridce, (Sea- Fig 104. — Nudibranchiata. Doris lemons), Tritotiiada, Johnston, one of the Sea-lemons. T. '' .. . _, ' . 7 ~ Phylhrhoidcz, and Elysiadce. Spe- cimens of the Sea-slugs and Sea-lemons may at any time be found creeping about on sea-weeds, or attached to the under surface of stones at low water. The head is furnished with tentacles, which appear to be rather connected with the sense of smell than to be used as tactile organs ; and behind the tentacles are generally two eyes. The nervous system is extremely well developed, and would lead to the belief that the Nudibranchs are amongst the highest of the Gasteropoda. Locomotion is effected, as in the true Slugs, by creeping about on the flattened foot. ORDER III. NUCLEOBRANCHIATA or HETEROPODA. — This order is defined by the following characteristics : — Animal pro- vided with a shell, or not, free-swimming and pelagic ; loco- MOLLUSCA: GASTEROPODA. 293 motion effected by a fin-like tail, or by a fan-shaped, vertically- flattened, ventral fin. Fig. 105. — Heteropoda. Carinariacyntbium. ^Proboscis; t Tentacles; b Branchiae ; *• Shell; / Foot ; d Disc. (After Woodward.) The Heteropoda are pelagic in their habits, and are found swimming at the surface of the sea. They are to be regarded as the most highly organised of all the Gasteropoda, at the same time that they are not the most typical members of the class. Some of them can retire completely within their shells, closing them with an operculum ; but most have large bodies, and the shell is either small or entirely wanting. They swim by means of a flattened ventral fin, or by an elongated tail, and adhere at pleasure to sea-weed by a small sucker situated on the side of the fin. These organs are merely modifications of the foot of the ordinary Gasteropods ; the fin-like tail being the " metapodium" (as shown by its occasionally carrying an operculum), the sucker being the " mesopodium," and the ven- tral fin being a modified " propodium." The "epipodia" are apparently altogether wanting. Respiration is sometimes car- ried on by distinct branchiae, but in many cases these are wanting, and the function is performed simply by the walls of the pallial chamber. The Heteropoda are divided into the two families Firolidce and Atlantid&i the former characterised by having a small shell covering the circulatory and respiratory organs, or by having no shell at all : whilst in the latter there is a well-developed shell, into which the animal can retire, and an operculum is often present. SUB-CLASS B. PULMONIFERA or PULMOGASTEROPODA. — In this sub-class of the Gasteropoda respiration is aerial, and is carried on by an inflection of the mantle, forming a pulmonary chamber, into which air is admitted by an external aperture. 294 MANUAL OF ZOOLOGY. The flexure of the intestine is neural, and the sexes are united in the same individual. The Pulmonifera include the ordinary land -snails, slugs, pond - snails, &c., and are usually provided with a well- developed shell, though this may be rudimentary (as in the slugs), or even wanting. Though formed to breathe air di- rectly, many of the members of this sub-class are capable of inhabiting fresh water. They are divided into two sections as follows : — Section I. Inoperculata. — Animal not provided with an oper- culum to close the shell. In this section are included the families Helicida (Land-snails), Limacidce (Slugs), Oncidiadcz, Limnceidcv (Pond-snails), and Atiriculidce. Section II. Operculata. — Shell closed by an operculum. In this section are included the families Cyckstomida and Aciculidcs. SYNOPSIS OF THE FAMILIES OF THE GASTEROPODA. (AFTER WOODWARD.) SECTION A. BRANCHIFERA. Respiration aquatic, by the walls of the mantle-cavity, or by branchiae. ORDER I. PROSOBRANCHIATA. The branchiae situated (proson) in ad- vance of the heart. Division a. Siphonostomata. Margin of the shell-aperture notched or produced into a canal. Fam. I. Strombidtz. Shell with an expanded lip, deeply notched near the canal. Operculum claw-shaped. Foot narrow, adapted for leaping. 111. Gen. Strombus, Pteroceras. Fam. 2. Muricida. Shell with a straight anterior canal, the aper- ture entire posteriorly. Foot broad. 111. Gen. Murex, Triton, Pyrula, Fustis. Fam. 3. Buccinidce. Shell notched anteriorly, or with the canal abruptly reflected, producing a kind of varix on the front of the shell. 111. Gen. Buccinum, Nassa, Purpura, Cassis, Harpa, Oliva. Fam. 4. Conidcz. Shell inversely conical, with a long narrow aper- ture, the outer lip notched at or near the suture. Operculum minute, lamellar. 111. Gen. Conus, Pleurotoma. Fam. 5. Volutida. Shell turreted or convolute, the aperture notched in front ; the columella obliquely plaited. No operculum. Foot very large ; mantle often reflected over the shell. 111. Gen. Valuta, Mitra, Marginella. Fam. 6. Cypraidce. Shell convolute, enamelled ; spire concealed, aperture narrow, channelled at each end. Outer lip thin in the young shell, but thickened and inflected in the adult. Foot broad ; mantle forming lobes which meet over the back of the shell. 111. Gen. Cypr&a, Ovulum. Division b. Holostomata. Margin of the shell- aperture "entire," rarely notched or produced into a canal. Fam. i. AraticidcE. Shell globular, of few whorls, with a small spire, outer lip acute, pillar often callous. Foot very large ; mantle- lobes hiding more or less of the shell. Gen. Natica, Sigaretus. MOLLUSCA: GASTEROPODA. 295 Fam. 2. Pyramidellidcz. Shell turreted, with a small aperture, sometimes with one or more prominent plaits on the columella. Operculum horny, imbricated. 111. Gen. Pyramidella^ Ckemnitzia, Eulima. Fam. 3. Cerithiada. Shell spiral, turreted ; aperture channelled in front, with a less distinct posterior canal. Lip generally expanded in the adult. Operculum horny and spiral. 111. Gen. Cerithium, Potamides, Aporrhais. Fam. 4. Melaniadce. Shell spiral, turreted ; aperture often chan- nelled or notched in front ; outer lip acute. Operculum horny and spiral. 111. Gen. Melania, Paludomus. Fam. 5. Turritellidce. Shell tubular, or spiral, often turreted ; upper part partitioned off; aperture simple. Operculum horny, many-whorled. Foot very short. Branchial plume single. 111. Gen. Turritella, Vermetus, Scalaria. Fam. 6. Littorinidce. Shell spiral, top-shaped, or depressed ; aper- ture rounded and entire ; operculum horny and pauci-spiral. 111. Gen. Littorina, Solarium, Rissoa, Phorus. Fam. 7. Pahtdinidiz. Shell conical or globular ; aperture rounded and entire ; operculum horny or shelly. 111. Gen. Paludina, Ampullaria, Valvata. Fam. 8. Neritida. Shell thick, globular, with a very small spire ; aperture semi - lunate, its columellar side expanded ; outer lip acute. Operculum shelly, sub-spiral. 111. Gen. Nerita, Pileolus, Neritina. Fam. 9. Turbinida. Shell turbinated (top-shaped), or pyramidal, nacreous inside. Operculum horny and multi-spiral, or calca- reous and pauci-spiral. 111. Gen. Turbo, Trochus, Delphinulat Euomphalus. Fam. 10. Haliotida. Shell spiral, ear-shaped, or trochoid ; aperture large, nacreous. Outer lip notched or perforated. No operculum. Mantle-margin with a posterior fold or siphon, occupying the slit or perforation in the shell. Metapodium rudimentary. 111. Gen. Haliotisy Scissurella, Pleurotomaria, Murchisonia, lanthina. Fam. 1 1. Fissurellida. Shell conical, patelliform, with a notch in the anterior margin, or a perforation at its apex, which is occupied by an anal siphon. Muscular impression horse-shoe-shaped, open in front. 111. Gen. Fissurella, Emarginula, Parmophorus. Fam. 12. Cafyptrceida. Shell patelliform, with a more or less spiral apex ; interior simple, or divided by a shelly process to which the adductor muscles are attached. 111. Gen. Calyptnza, Pileopsis. Fam. 13. Patellidtz. Shell conical, with the apex turned forwards; muscular impression horse-shoe-shaped, open in front. Foot as large as the margin of the mantle. Respiratory organ in the form of one or two branchial plumes, lodged in a cervical cavity ; or of a series of lamellae surrounding the animal between the body and the mantle. 111. Gen. Patella, Acmcea. Fam. 14. Dentalida. Shell tubular, symmetrical, curved, open at both ends. Aperture circular. Foot pointed, with symmetrical side-lobes. Gen. Dentalium* Fam. 15. Ckitonida. Shell multivalve, composed of eight transverse * Dentalium is placed by Professor Huxley amongst the Pteropoda, from its rudimentary head, the neural flexure of the intestine, the nature of the epipodia, and the characters of the larva. 296 MANUAL OF ZOOLOGY. imbricated plates. Animal with broad creeping foot ; branchiae forming a series of lamellae between the foot and the mantle, round the posterior part of the body. 111. Gen. Chiton, Crypto- chiton. ORDER II. OPISTHOBRANCHIATA. Branchiae placed towards the rear (ppistheri) of the body. Section a. Tectibranchiata. Branchice covered by the shell or mantle; a shell in most. Sexes united. Fam. I. Tornatellidce. Shell external, spiral, or convoluted ; aper- ture long and narrow ; columella plaited. 111. Gen. Tornatella, Cinulia. Fam. 2. Bullidce. Shell convoluted, thin ; spire small or concealed, lip sharp. Animal more or less investing the shell. 111. Gen. Bulla, Cylichna, Philine. Fam. 3. Aplysiada. Shell absent, or rudimentary and concealed by the mantle. Animal slug -like, with extensive side -lobes (epipodia), reflected over the back and shell. 111. Gen. Aplysia, Dolabella. Fam. 4. PleurobranchidcB. Shell patelliform, or concealed, rarely wanting. Mantle or shell covering the back of the animal. 111. Gen. Pleurobranchus, Umbrella, Tylodina. Fam. 5. Phyllidiada. Animal shell-less, covered by a mantle. 111. Gen. Phyllidia, Diphyllidia. Section b. Nudibranchiata. Animal destitute of a shell in the adult con- dition. Branchice external, on the back or sides of the body. Fam. 6. Dorida. 111. Gen. Doris. Fam. 7. Tritoniada. 111. Gen. Tritonia, Scyll&a. Fam. 8. sEolidce. 111. Gen. sEolis, Glaucus. Fam. 9. Phyllirhoidce. Gen. Phyllirhoe. Fam. 10. Elysiadce. 111. Gen. Elysia, Acteonia. ORDER III. NUCLEOBRANCHIATA or HETEROPODA. Shell present or absent. Animal free-swimming and pelagic, with a fin-like tail, or a flattened ventral fin. Fam. i. Firolidce. Body large ; branchiae exposed on the back, or covered by a small hyaline shell ; locomotion by means of a ventral fin and a tail-fin. 111. Gen. Carinaria, Firola. Fam. 2. Atlantida. Animal furnished with a well-developed shell into which it can retire. Branchiae contained in a dorsal mantle- cavity. Shell symmetrical, discoidal, sometimes with an oper- culum. 111. Gen. Atlanta, Bellerophon, Maclurea. SECTION B. PULMONIFERA. Respiration aerial, by means of a pulmonary chamber. DIVISION I. INOPERCULATA. Shell not provided with an operculum. Fam. I. Helicida. Shell external, capable of containing the whole animal. 111. Gen. Helix, Bulimus, Clausilia, Pupa. Fam. 2. Limacidce. Shell rudimentary, usually internal or partly concealed by the mantle. 111. Gen. Limax, Parmacella, Testa- cella. Fam. 3. Oncidiada. Shell wanting. Animal slug-like. 111. Gen. Oncidium, Vaginulus. Fam. 4. Limn&idce. Shell thin, horn-coloured, well developed. Aperture simple, lip sharp. 111. Gen. Limnaa, Physa, Ancylus, Planorbis. Fam. 5. Auriculida. Shell spiral, with a horny epidermis ; aperture elongated, denticulated. 111. Gen. Auricula, Conovulus. DIVISION II. OPERCULATA. Shell with an opercuhun. MOLLUSCA: PTEROPODA. 297 Fam. 6. Cyclostomidce. Shell spiral, rarely elongated, often de- pressed. Aperture nearly circular. Operculum spiral. 111. Gen. Cyclostoma, Cyclophorus, Pupina. Fam. 7. Aciculidce. Shell elongated, cylindrical ; operculum thin, and sub-spiral. Gen. Acicula, Geomdania. CHAPTER XLIX. PTEROPODA. CLASS III. PTEROPODA. — The Pteropoda are defined by being free and pelagic, swimming by means of two wing-like appen- dages (epipodia), developed from each side of the anterior extremity of the body. The flexure of the intestine is neural. As to the position of the Pteropoda in the Molluscan scale, they must be looked upon as inferior in organisation to any of the Gasteropoda, of which class they are often regarded as the lowest division. They permanently represent, in fact, the tran- sient, larval, stage of the sea-snails. Fig. 1 06. — Pteropoda. a Cleodora pyramidata ; b Cuvierta columnella. (After Woodward.) The Pteropods are all of small size, and are found swim- ming at the surface of the open ocean, often in enormous numbers. Locomotion is effected by two wing-like fins, devel- oped from the sides of the head, and composed of the greatly developed " epipodia." The true " foot " is rudimentary and rarely distinct, but the " metapodium " is sometimes provided with an operculum. There is usually a symmetrical glassy shell (fig. 1 06), either consisting of a dorsal and ventral plate united, or forming a spiral, but in some cases the body is naked. The head is rudimentary, and bears the mouth, which is occasionally tentaculate. arid which is furnished with an odontophore. There is a muscular stomach, and a well-devel- 298 MANUAL OF ZOOLOGY. oped liver, and the flexure of the intestine is neural, so that the anus is situated on the ventral surface of the body. The heart consists of an auricle and ventricle. The respi- ratory organ is very rudimentary, and consists of a ciliated surface, which is either entirely unprotected, or may be con- tained in a branchial chamber. The ganglia of the nervous system " are concentrated into a mass below the oesophagus " (Woodward), and the eyes are rudimentary. The sexes are united in all the Pteropods, and the young pass through a metamorphosis, having at first a bilobed ciliated veil attached to the sides of the head. The Pteropoda are divided into two orders, termed Thecoso- mata and Gymnosomata ; the former characterised by possess- ing an external shell and an indistinct head; the latter by being devoid of a shell, and by having a distinct head, with fins attached to the neck. The Pteropoda, as already said, are found swimming near the surface in the open ocean, and they are found in all seas from the tropics to within the arctic circle, sometimes in such numbers as to discolour the water for many miles. They are nocturnal in their habits, and, minute as they are, they con- stitute in high latitudes one of the staple articles of diet of the whale. They themselves are, in turn, probably car- nivorous, feeding upon small Crustaceans and other diminutive animals. Though all the living forms are small, Geology leads us to believe that there formerly existed comparatively gigantic representatives of this class of the Mollusca. SYNOPSIS OF THE FAMILIES OF THE PTEROPODA. (AFTER WOODWARD.) ORDER I. THECOSOMATA. Animal with an external shell; head indistinct; foot and ten- tacles rudimentary ; mouth situated in a cavity formed by the union of the locomotive organs. Respiratory organs contained within a mantle-cavity. Fain. I. Hyaleida. Shell symmetrical, straight or curved, globular, or needle-shaped. 111. Gen. Hyalea, Cleodora, Theca, Conularia. Fam. 2. Limacinidce. Shell minute, spiral, sometimes operculate. 111. Gen. Limacina, Spirialis. ORDER II. GYMNOSOMATA. Animal naked, without mantle or shell, head distinct j fins at- tached to the sides of the neck ; gill indistinct. Fam. 3. Cliida. Body fusiform, foot distinct, with a central and posterior lobe; head with tentacles. 111. Gen. Clio, Pneumodermon. MOLLUSCA: CEPHALOPODA. 299 CHAPTER L. CEPHALOPODA. CLASS IV. CEPHALOPODA. — The members of this class are defined by the possession of eight or more arms placed in a circle round the mouth ; the body is enclosed in a muscular mantle-sac, and there are two or four plume-like gills within the mantle. There is an anterior tubular orifice (the " infun- dibulum " or "funnel"), through which the effete water of re- spiration is expelled. The flexure of the intestine is neural. The Cephalopoda, comprising the Cuttle-fishes, Squids, Pearly Nautilus, &c., constitute the most highly organised of the classes of the Molhtsca. They are all marine, and carnivo- rous, and are possessed of considerable locomotive powers. At the bottom of the sea they can walk about, head downwards, by means of the arms which surround the mouth, and which are usually provided with numerous suckers or " acetabula." They are also enabled to swim, partly by means of lateral expansions of the integument or fins (not always present), and partly by means of the forcible expulsion of water through the tubular " funnel," the reaction of which causes the animal to move in the opposite direction. The majority of the living Cephalopods are naked, possess- ing only an internal skeleton, and this often a rudimentary one; but the Argonaut (Paper Nautilus), and the Pearly Nautilus, are protected with an external shell, though the nature of this is extremely different in the two forms. The integument in the Cuttle-fishes is provided with nume- rous little sacs, containing pigment-granules of different colours, and termed " chromatophores." By means of these many species can change their colours rapidly, under irritation or excitement. The body in the Cephalopoda is symmetrical, and is enclosed in an integument which may be regarded as a modification of the mantle of the other Mollusca. Ordinarily there is a tolerably distinct separation of the body into an anterior cephalic portion (prosoma), and a posterior portion, enveloped in the mantle, and containing the viscera (metasoma). The head is very distinct, bearing a pair of large globular eyes, and having the mouth in its centre. The mouth is surrounded by a circle of eight, ten, or more, long muscular processes, or "arms" (fig. 107), which are generally provided with rows of suckers. Each sucker, or " acetabulum," consists of a cup- 300 MANUAL OF ZOOLOGY. shaped cavity, the muscular fibres of which converge to the centre, where there is a little muscular eminence or papilla. When the sucker is applied to any surface, the contraction of the radiating muscular fibres depresses the papilla so as to produce a vacuum below it, and in this way each sucker acts most efficiently as an adhesive organ. In some forms (Decapoda) the base of the papilla, or piston, is surrounded by a horny dentated ring, and in some others (as in Onychoteuthis] the papillae are produced into long claws. In the Octopod Cuttle-fishes there are only eight arms, and these are all nearly alike. In the Decapod Cuttle- fishes there are ten arms, but two of these — called " tentacles " — are much longer than the others, and bear suckers only at their extremities, which are en- larged and club-shaped. In the Nautilus the arms are and are devoid of suckers. The arms are really produced by an extension of the mar- gins of the " foot," or of the part corresponding to the foot of the other Mollusca. The " antero-lateral parts of each side of the foot extend forwards beyond the head, uniting with it and with one another; so that, at length, the mouth, from having been situated, as usual, above the anterior margin of the foot, comes to be placed in the midst of it. The two epipodia, on the other hand, unite posteriorly above the foot, and where they coalesce, give rise either to a folded muscular expansion, the edges of which are simply in apposition, as in the Nautihis ; or to an elongated flexible tube, the apex of which projects beyond the margin of the mantle, called the 'funnel,' or ' infundibulum/ as in the dibranchiate Cephalopoda" — (Huxley.) The mouth leads into a buccal cavity, containing two powerful, horny or partially calcareous, mandibles, working vertically like the beak of a bird ; together with an " odonto- phore" or "tongue," the anterior part of which is sentient, Fig. 107. — Cephalopoda. Sepiola Pearly Atlantica, one of the Cuttle-fishes (after Woodward). " UlTierOUS, MOLLUSCA: CEPHALOPODA. 301 whilst the remainder is covered with recurved spines. The buccal cavity conducts by an oesophagus — into which salivary glands usually pour their secretion — to a stomach, from which an intestine is continued, with a neural flexure, to open on the ventral surface of the animal at the base of the funnel. In many cases there is also a special gland, called the " ink-bag," for the secretion of an inky fluid, which the animal discharges into the water, so as to enable it to escape when menaced or pursued. The duct of the ink-bag opens at the base of the funnel ; but this apparatus is entirely wanting in the Tetra- branchiate Cephalopods, where, in consequence of the presence of an external shell, this means of defence is not needed. The respiratory organs are in the form of two or four plume- like gills, placed on the sides of the body in a branchial cavity which opens anteriorly on the under surface of the body. At the base of each gill, in the Cuttle-fishes, is a special contrac- tile cavity, whereby the venous blood returned from the body is driven through the branchiae. In addition to these accessory organs — the so-called "branchial hearts" — there is a true systemic heart, by which the aerated blood received from the gills is propelled through the body. In the higher Cephalopods a capillary system of vessels intervenes, in most cases at any rate, between the arteries and the veins. The admission of water to the branchiae is effected by the expansion of the mantle so as to allow the entrance of the outer water into the pallial chamber. The mantle then contracts, and the water is forcibly expelled through the funnel, which is provided with a valve permitting the egress of water but preventing its ingress. By a repetition of this process, not only is respi- ration effected, but locomotion is simultaneously subserved; the jets of water expelled from the funnel, by their reaction, driving the animal in the opposite direction. The nervous system is formed upon essentially the same plan as in the other Mollusca, but it is more concentrated, and the supra-cesophageal or cerebral ganglia are protected by a cartilage, which is to be regarded as a rudimentary cranium. This structure, therefore, presents us with the nearest ap- proach which we have yet met with to the Vertebrate type of organisation. The sexes in all the Cephalopoda are in different individuals, and the reproductive process in the Dibranchiate section of the class (Cuttle-fishes) is attended with some very singular phenomena. In this order the ducts of the generative organs open into the pallial chamber, and each individual, besides the essential organs of reproduction (testis or ovary), gene- 302 MANUAL OF ZOOLOGY. rally possesses an accessory gland ; that of the female secret- ing a viscid material which unites the eggs together, whilst that of the male coats the spermatozoa, and aggregates them into peculiar worm-like filaments, termed " spermatophores," or the " moving filaments of Needham." The spermatophore is filled with spermatozoa, and possesses the power of ex- panding when moistened, rupturing, and expelling the con- tained spermatozoa with considerable force. During the congress of the sexes the male transfers the spermatophores to the pallial chamber of the female, true intromission not being possible. Further, in all the male Cuttle-fishes one of the arms is specially modified to subserve reproduction ; being in many cases so altered as to become useless as a locomotive organ. The arm so affected, in the more striking forms, is said to be " hectoctoylised," and — like the metamorphosed palpi of the male spiders — it serves to convey the seminal fluid to the female. The mode in which this is effected varies in different species. Thus, in the male Octopus (the Poulpe) the third right arm is primitively developed in a cyst, which ultimately ruptures and liberates the metamorphosed arm, which then appears to be of greater size than the correspond- ing arm on the left side, and to terminate in an oval plate (fig. 1 08). To this terminal plate the spermatophore is pro- bably transmitted, but the arm itself probably remains perma- nently attached to the animal. It is asserted, however, that in the form figured below (Octopus carena) the hectocotylised arm is detached and deposited in the pallial chamber of the female ; being reproduced after each generative act. In Tre- moctopus the third right arm of the male is " hectocotylised," and is converted into a vermiform body, with two rows of ventral suckers, and an oval appendage or sac behind, which contains spermatozoa. Besides the suckers, the anterior part of the back is fringed with a number of so-called " branchial " filaments. In the Argonaut the male is not more than an inch in length, is devoid of a shell, and has its third left arm hectocotylised. This arm is developed in a cyst, which is ruptured by the movements of the "hectocotylus," which then appears as a small worm-like body, with a filiform appendage in front, with two rows of alternating suckers, and a dorsal sac with nume- rous " chromatophores." The duct of the testis probably opens into the base of the hectocotylus, which is ultimately detached, and is deposited by the male within the pallial chamber of the female. When first discovered in this position, it was described as a parasitic worm under the name of " Hectocotylus;" sub- MOLLUSCA : CEPHALOPODA. 303 sequently it was described as the entire male, and it is only recently that its true nature has been fully ascertained. Fig. 108. — i. Octopus carena (male), showing cyst in place of the third arm. 2. Ven- tral side of an individual, more developed, with the hectocotylus (a). (After Woodward.) The shell of the Cephalopoda is sometimes external, some- times internal. The internal skeleton is known as the " cuttle- bone," " sepiostaire," or "pen" (gladius), and may be either corneous or calcareous. In some cases it is rendered complex by the addition of a chambered portion or " phragmacone," which is to be regarded as a visceral skeleton or " splanchno- skeleton." In Spirula the phragmacone is the sole internal skeleton, and is coiled into a spiral, the coils of which lie in one plane, and are near one another, but not in contact. It thus resembles the shell of the Pearly Nautilus, but it is internal, and differs, therefore, entirely from the external shell of the latter. The only living Cephalopods which are provided with an external shell are the Paper Nautilus (Argonautd), and the Pearly Nautilus (Nautilus pompilius) ; but not only is the struc- ture of the animal different in each of these, but the nature of 304 MANUAL OF ZOOLOGY. the shell itself is entirely different. The shell of the Argonaut (fig. 109) is involuted, but is not divided into chambers, and it is secreted by the webbed extremities of two of the dorsal arms of the female. The arms are bent backwards, so as to allow the animal to live in the shell, but there is in reality no organic connection between the shell and the body of the animal. In fact, the shell of the Argonaut, being confined to the female, and serving by its empty apex as a receptacle for the ova, may be looked upon as a " nidamental shell," or as it is secreted by a modified portion of the foot, it may more properly be regarded as a "pedal shell." The shell of the Pearly Nautilus (fig. m), on the other hand, is a true pallial shell, and is secreted by the body of the animal, to which it is organically connected. It is involuted, but it differs from the shell of the Argonaut in being divided into a series of chambers by shelly partitions or septa, which are pierced by a tube or " siphuncle," the animal itself living in the last chamber only of the shell. The Cephalopoda are divided into two extremely distinct and well marked orders, termed the Dibranchiata and the Tetra- branchiata. The former is characterised by the possession of two branchiae only, and comprises the Cuttle-fishes, Squids, and the Paper Nautilus. The latter is distinguished by the presence of four gills, and, though abundantly represented in past time, has no other living representative than the Pearly Nautilus alone. CHAPTER LI. DIVISIONS OF THE CEPHALOPODA. ORDER I. DIBRANCHIATA. — The members of this order of the Cephalopoda are characterised as being swimming animals, almost invariably naked, with never more than eight or ten arms, which are always provided with suckers. There are two branchiae, which are furnished with branchial hearts ; an ink-sac is always present ; the funnel is a complete tube, and the shell is internal, or, if external, is not chambered. The Cuttle-fishes are rapacious and active animals, swim- ming freely by means of the jet of water expelled from the funnel. The arms constitute powerful offensive weapons, being excessively tenacious in their hold, and being sometimes provided with a sharp claw in the centre of each sucker. They MOLLUSCA : CEPHALOPODA. 305 are mostly nocturnal or crepuscular animals, and they some- times attain to a great size. They may be divided into two sec- tions, Octopoda and Decapoda, according as they have simply eight arms, or eight arms and two additional " tentacles." SECTION A. OCTOPODA. — The Cephalopods comprised in this section are distinguished by the possession of not more than eight arms, which are provided with sessile suck- ers. The shell is internal and rudimentary ; in one instance only (the Argo- naut), external. This section comprises the two families of the Argonautidce, and the Oc- topodidcz. In the former of these there is only the single genus Argonauta (the Paper Sailor, or the Paper Nautilus), of which the female and male differ greatly from one another. The female Argonaut (fig. 109) is protected by a thin single-chambered shell, in form symmetrical and in- voluted, which is secreted by the webbed extremi- ties of the dorsal arms, but is not attached in any way to the body of the animal. It sits in its shell with the funnel turned toward the keel, and the webbed arms applied to the shell. The male Argonaut is much smaller than the female (about an inch in length), and is not protected by any shell. The third left arm is developed in a cyst, and ultimately becomes a " hectocotylus," and is deposited by the male in the pallial chamber of the female. ^ In the Octopodida (or Poulpes) there are eight arms, all similar to one another, and united at the base by a web. There is an internal rudimentary shell, represented by two short styles encysted in the substance of the mantle. — (Owen.) The body is seldom provided with lateral fins. The third right arm of the male is primarily developed in a cyst, and ulti- mately becomes " hectocotylised." VOL. i. Fig. 109. — Argonauta argo, the "Paper Nau- tilus," female. The animal is represented in its shell, but the webbed dorsal arms are se- parated from the shell, which they ordinarily embrace. 306 MANUAL OF ZOOLOGY. SECTION B. DECAPODA. — The Cephalopods of this section have eight arms and two additional " tentacles," which are much longer than the true arms, and have ex- panded club-shaped extremities (fig. 107). The suckers are pedunculated; the body is always provided with lateral fins, and the shell is always internal. This section comprises the three living families of the Tatthidce, Sepi- adcz, and the Spirnlidce, and the extinct family of the Belemnitidce. The family of the Ttuthidce com- prises the Calamaries or Squids, cha- racterised by the possession of an elongated body with lateral fins. The shell is internal and horny, con- sisting of a median shaft and of two lateral wings ; it is termed the "gladi- us" or "pen," and in old specimens several may be found lodged in the mantle, one behind the other. In the common Calamary (Loligo) the fourth left arm of the male is meta- morphosed towards its extremity to subserve reproduction. In the family of the Sepiadcz the internal shell is calcareous ("cuttle- bone " or " sepiostaire")and is in the fonn of a broad plate, having an im- perfectly chambered apex. In the living members of the family the body is provided with long lateral fins, sometimes as long and as wide as the body itself. In the singular family of the Spiru- lidce the internal skeleton is in the form of a nacreous, discoidal shell, the whorls of which are not in con- tact with one another, and which is divided into a series of chambers by means of partitions or septa which are pierced by a ventral tube or " siphuncle." The body is provided with minute terminal fins. The shell of the Spirula — commonly known as the " post-horn " — is similar Fig. no. — Diagram of Belem- nite (after Professor Phillips). r Horny pen or "pro-ostra- cum ;" p Chambered " phrag- macone" in its cavity (a) or ' ' alveolus ; " g" Guard. " MOLLUSCA : CEPHALOPODA. 3O/ in structure to the shell of the Nautilus, but it is lodged in the posterior part of the body of the animal, and is therefore internal, whereas the shell of the latter is external. It really corresponds to the " phragmacone" of the Belemnite. Though the shell occurs in enormous numbers in certain localities, a single perfect specimen of the animal is all that has been hitherto obtained. In the extinct family of the Belemnitidce, our knowledge is chiefly confined to the hard parts. Certain specimens, however, have been discovered which show that the Belemnite had essentially the structure of a Cuttle-fish, such as the recent Sepia. The body was provided with lateral fins ; the arms were eight, furnished with horny hooks, with two "tentacles;" and probably the mouth was provided with horny mandibles. An ink-bag was present. The internal skeleton of a Belem- nite (fig. no) consists of a chambered cone — the "phragma- cone"— the septa of which are pierced with a marginal tube or " siphuncle." In the last chamber of the phragmacone is contained the ink-bag, often in a well-preserved condition. Anteriorly the phragmacone is continued into a horny lamina or " pen " (the " pro-ostracum " of Huxley), and posteriorly it is lodged in a conical sheath or " alveolus," which is excavated in the substance of a nearly cylindrical, fibrous body, the "guard" (fig. no, g\ which projects backwards for a longer or shorter distance, and is the part most usually found in a fossil condition. ORDER II. TETRABRANCHIATA. — The members of this order of the Cephalopoda are characterised by being creeping animals, protected by an external, many- chambered shell, the septa between the chambers of which are perforated by a membra- nous or calcareous tube, termed the " siphuncle." The arms are numerous, and are devoid of suckers; the branchiae are four in number, two on each side of the body ; the funnel does not form a complete tube ; and there is no ink-bag. Though abundantly represented by many and varied extinct forms, the only living member of the Tetrabranchiata is the Pearly Nautilus, which has been long known by its beautiful chambered shell, but the soft parts of which can hardly be said to be known by more than one perfect specimen, which was examined by Professor Owen. The soft structures in the Pearly Nautilus may be divided into a posterior, soft, membranous mass (metasoma), contain- ing the viscera, and an anterior muscular division, comprising the head (prosoma )/ the whole being contained in the outer- most, capacious chamber (the body-chamber) of the shell, from 308 MANUAL OF ZOOLOGY. which the head can be protruded at will. The shell itself (fig. in) is involuted and many- chambered, the animal being con- tained successively in each chamber, and retiring from it as its size becomes sufficiently great to necessitate the acquisition of more room. Each chamber, as the animal retires from it, is walled off by a curved, nacreous septum ; the communication between the chambers being still kept up by a membranous tube or siphuncle, which opens at one extremity into the peri- cardium, and is continued through the entire length of the shell. The position of the siphuncle is in the centre of each septum. Fig. in. — Pearly Nautilus (Nautilus pompilius). a Mantle; b Its dorsal fold; c Hood ; o Eye ; t Tentacles ; / Funnel. Posteriorly the mantle of the Nautilus is very thin, but it is much thicker in front, and forms a thick fold or collar sur- rounding the head and its appendages. From the sides of the head spring a great number of muscular prehensile processes or " arms," which are annulated, but are not provided with cups or suckers. In the centre of the head is the mouth, sur- rounded by a circular fleshy lip, external to which is a series of labial processes. The mouth opens into a buccal cavity, armed with two horny mandibles, partially calcified towards their extremities, and shaped like the beak of a parrot, ex- cept that the under mandible is the longest. There is also a " tongue," which is fleshy and sentient in front, but is armed with recurved teeth behind. The gullet opens into a MOLLUSCA I CEPHALOPODA. 309 large crop, which in turn conducts to a gizzard, and the intes- tine terminates at the base of the funnel. On each side of the crop is a well-developed liver. The heart is contained in a large cavity, divided into several chambers, and termed the "pericardium."- — (Owen.) The re- spiratory organs are in the form of four pyramidal branchiae, two on each side. The chief masses of the nervous system are the cerebral and infra-oesophageal ganglia, which are partially protected by a cartilaginous plate, which is to be regarded as a rudimentary cranium, and which sends out processes for the attachment of muscles. The organs of sense are two large eyes, attached by short stalks to the sides of the head, and two hollow plicated subocular processes, believed to be olfactory in their function. The reproductive organs of the female consist of an ovary, oviduct, and accessory nidamental gland. There is no ink-bag, and the funnel does not form a com- plete tube, but consists of two muscular lobes, which are simply in apposition. It is the organ by which swimming is effected, the animal being propelled through the water by means of the reaction produced by the successive jets emitted from the funnel. The function of the chambers of the shell appears to be that of reducing the specific gravity of the animal to near that of the surrounding water, since they are most probably filled with some gas secreted by the animal. The function of the siphuncle is unknown, except in so far as it doubtless serves to maintain the vitality of the shell. SHELL OF THE TETRABRANCHIATA. — The shells of all the Tetrabranchiata agree in the following points : — T. The shell is external. 2. The shell is divided into a series of chambers by plates or " septa," the edges of which, where they appear on the shell, are termed the " sutures." 3. The outermost chamber of the shell is the largest, and is the one inhabited by the animal. 4. The various chambers of the shell are united by a tube, termed the " siphuncle." Agreeing in all these fundamental points of . structure, two very distinct types of shell may be distinguished as character- istic of the two families Nautilida and Ammonitida, into which the order Tetrabranchiata is divided. In the family Nautilida (fig. 112), the " septa" of the shell are simple, curved, or slightly lobed ; the " sutures " are more or less completely plain; and the "siphuncle" is central, 3io MANUAL OF ZOOLOGY. sub-central, or internal (i.e., on the concave side of the curved shells). In the family Ammonitida (fig. 112), on the other hand, the septa are folded and complex ; the sutures are angulated, zig- zag, lobed, or foliaceous ; and the siphuncle is external (i.e., on the convex side of the curved shells). 0 ,0 ' Q .0 Fig. 112. — Diagram to illustrate the position of the siphuncle and the form of the septa in various Tetrabranchiate Cephalopoda. The upper row of figures represents transverse sections of the shells, the lower row represents the edges of the septa. a a Ammonite or Baculite', bb Ceratite', cc Goniatite\ dd Clymenia', e e Nau- tilus or Orthoceras. In both these great types of shell, a series of representative forms exists, resembling each other in the manner in which the shell is folded or coiled, but differing in their fundamental structure. All these different forms may be looked upon as produced by the modification of a greatly elongated cone, the structure of which may be in conformity with the type either of the Nautilida or of the Ammonitidce. The following table (after Woodward) exhibits the representative forms in the two families : — Nautilidce. Ammonitidce. Shell straight .... Orthoceras . . Baculites. „ bent on itself . . Ascoceras . . Ptychoceras. „ curved .... Cyrtoceras . . Toxoceras. „ spiral Trochoceras . Turrilites. „ discoidal .... Gyroceras . . Crioceras. „ discoidal and produced Lituites . . . Ancyloceras. „ involute .... Nautilus . . . Ammonites. After the Nautilus itself, the most important form of the Nautilidce is the Orthoceras (fig. 113). In structure this was doubtless essentially identical with the Nautilus, but the shell, instead of being coiled into a spiral lying in one plane, was ex- tended in a straight, or nearly straight, line. Orthoceratites of more than six feet in length have been discovered, but in all, MOLLUSCA : CEPHALOPODA. 311 the body-chamber, in which the animal was lodged, appears to have been comparatively small. The siphuncle is usually very complex in structure, and was calcareous throughout its entire length. Fig. 113. — Orthoceras exploraior, Billings, i. Side view of a fragment, showing the septa. 2. Transverse section of the same, showing (s) the siphuncle. The simplest form of the Ammonitidce is the Baculite, in which the shell is straight, like that of an Orthoceras^ whilst the septa have the characters of those of an Ammonite, and the siphuncle is external. In the Turrilite the structure of the shell is the same, but it is coiled into a spiral. In the Ammonite itself, the shell is discoidal and involuted, corresponding (in form) to the shell of the Nautilus ; the body-chamber was of comparatively large size, and had its aperture closed, in some species at any rate, by an operculum. SYNOPSIS OF THE FAMILIES OF THE CEPHALOPODA. CLASS CEPHALOPODA. ORDER I. DIBRANCHIATA. Animal with two branchiae; not more than eight or ten arms, provided with suckers; an ink-bag; shell commonly internal and rudimentary ; rarely external, but not chambered. SECTION A. OCTOPODA. Arms eight, suckers sessile. Fam. I. Argonautidce. Female provided with a calcareous, external, monothalamous shell, secreted by the webbed extremities of the dorsal arms. Gen. Argonauta. Fam. 2. Octopodidcz. Shell internal, rudimentary, uncalcified. No pallial fins in most. 111. Gen. Octopus, Tremoctopus, Eledone, Pinnoctopus. SECTION B. DECAPODA. Arms eight, with two clavate "tentacles;" suckers pedunculated* Fam. 3. Teuthida. Shell an internal horny " pen " or "gladius." Fins mostly terminal. 111. Gen. Loligo, Onychoteuthis, Ommastrephes. Fam. 4. Belemnitidce. Shell internal, composed of a conical chambered portion ("phragmacone") with a marginal siphuncle, sometimes produced into a horny plate or "pen," and lodged in a cylindrical fibrous "guard." 111. Gen. Belemnites, Belemnitella, Belemniteuthis. 312 MANUAL OF ZOOLOGY. Fam. 5- Sepiadce. Shell calcareous, consisting of a broad, laminar plate, termi- nating posteriorly in an imperfectly chambered apex ("phragma- cone "). 111. Gen. Sepia t Beloptera, Spirulirostra. Fam. 6. Spirulida. Shell internal, nacreous, chambered, discoidal ; the whorls separate ; a ventral siphuncle. Gen. Spirula. ORDER II. TETRABRANCHIATA. Animal with four gills ; arms more than ten, without suckers; no ink-bag ; shell external, chambered, and siphuncled. Fam. i. Nautilidce. Sutures of the shell simple ; the siphuncle central, sub-central, or, near the concavity of the curved shells, simple. Sub-family Nautilidce proper. Body-chamber capacious ; aperture simple; siphuncle central or internal. 111. Gen. Nautilus, Lituites, Trocho- ceras. Sub-family Orthoceratidcz. Shell straight, curved, or discoidal; body-chamber small; aperture contracted; siphuncle complicated. 111. Gen. Orthoceras, Phragmoceras, Cyrtoceras. Fam. 2. Ammonitidce. Shell discoidal, curved, spiral, or straight; body-chamber elongated ; aperture guarded by processes, or closed by an oper- culum; sutures angulated, lobed, or foliaceous; siphuncle external or dorsal (on the convex side of the curved shells). 111. Gen. Ammonites, Ceratites, Baculiles, Turrilitcs, Scaphites, Ancyloceras, CHAPTER LII. DISTRIBUTION OF THE MOLLUSC A PROPER IN TIME. REMAINS of the Mollusca proper are found in greater or less abundance in almost all the stratified rocks from the com- mencement of the Silurian period up to the present day. Speaking generally, the Tetrabranchiate Cephalopoda are the chief representatives of the Mollusca in the Palaeozoic rocks, the Lamellibranchiata and the Dibranchiate Cephalopoda in the Mesozoic rocks, and the Gasteropoda in the Kainozoic period; but all the primary classes are represented even in the Lower Silurian rocks. The following are the more noticeable facts relating to the distribution of the various classes in past time. Lamellibranchiata. — The Lamellibranchs are known to have existed in the Lower Silurian period, and have steadily in- creased up to the present day, when the class appears to have attained its maximum, both as regards numbers and as regards MOLLUSCA: DISTRIBUTION. 313 variety of type. The recent bivalves are also superior in organisation to those which have preceded them. Upon the whole the Asiphonate bivalves are more characteristically Palaeozoic, whilst those in which the mantle-lobes are united, and there are respiratory siphons, are chiefly found in the Secondary and Tertiary epochs. One very singular and aber- rant family — viz., the HippuritidcE — is exclusively confined to the Secondary rocks, and is, indeed, not known to occur beyond the limits of the Cretaceous formation. The Veneridce, which are perhaps the most highly organised of the families of the Lameliibranchiata, appear for the first time in the Oolitic rocks, and, increasing in the Tertiary period, have culminated in the Recent period. Gasteropoda, — The Gasteropoda are represented in past time from the Lower Silurian rocks up to the present day. Of the Branchifera the Holostomata are more abundant in the Palaeo- zoic period, the Siphonostomata abounding more in the Secon- dary and Tertiary rocks, but not attaining their maximum till the present day. The place of the carnivorous Siphono- stomata in the Palaeozoic seas appears to have been filled by the Tetrabranchiate Cephalopods. The Heteropoda are likewise of very ancient origin, having commenced their existence in the lowest Silurian deposits. The genera Bellerophon, Porcellia, Cyrtolites, and Maclurea, are almost exclusively Palaeozoic; Bellerophina is found in the Gault (Secondary), and Carinaria has been detected in the Tertiaries. The Pulmonate Gasteropoda , as was to be anticipated, are not found abundantly as fossils, occurring chiefly in lacustrine and estuarine deposits, in which the genera Limnaa, Paludina, Valvata, Ancylus, &c., are amongst those most commonly represented. These, however, are entirely Mesozoic and Kainozoic. In the Palaeozoic period the sole known represen- tatives of the Pulmonifera are the Pupa vetusta and Zonites priscus of the Carboniferous rocks. Pteropoda. — The Pteropods are not largely represented in fossiliferous deposits, but they have a wide range in time, ex- tending from the Lower Silurian rocks up to the present day. The Theca and Conularia of the Palaeozoic period, if truly Pteropods, are of comparatively gigantic size, and extend from the Lower Silurian to the Carboniferous period. The Silurian fossil, Tentaculites, is asserted by M. Barrande to be a Pteropod, but it is usually looked upon as a tubicolous Annelide. The recent genus Hyalea is represented in the Tertiary period (Miocene). 314 MANUAL OF ZOOLOGY. Cephalopoda. — The Cephalopods are largely represented in all the primary groups of stratified rocks from the Lower Silurian up to the present day. Of the two orders of Cepha- lopoda, the Tetrabranchiata is the oldest, attaining its maximum in the Palaeozoic period, decreasing in the Mesozoic and Kainozoic epochs, and being represented at the present day by the single form Nautilus pompilius. Of the sections of this order, the Nautilidcc proper and the Orthoceratidcz are pre- eminently Palaeozoic, and the Ammonitida are not only pre- eminently but are almost exclusively Secondary. Of the abun- dance of the two former families in the Silurian seas some idea may be obtained when it is mentioned that over a thousand species have been described by M. Barrande from the Silurian basin of Bohemia alone. The Nautilida proper have gradually decreased in numbers from the Palaeozoic, through the Secondary and Tertiary periods to the present day. The Orthoceratidcz died out much sooner, being exclu- sively Palaeozoic, with the exception of the genera Orthoceras itself and Cyrtoceras, which survived into the commencement of the Secondary period, finally dying out in the Trias. Fig. 114. — Shells of Secondary Cephalopods. i Ancyloceras Matheronianus; 2 Sca- pkites eequalis; 3 Crioceras Duvalii; 4 Hamttes attenuatus ; 5 Turrilites catenatus. The second family of the Tetrabranchiata — viz., the Ammo- nitidcz — is almost exclusively Secondary, being very largely re- presented by numerous species of the genera Ammonites, Cera- SUBDIVISIONS OF INVERTEBRATA. 315 fifes, B acuities, Turrilites, &c. The only Palaeozoic genera are Goniatites and Bactrites, of which the former is found ' from the Upper Silurian to the Trias, whilst the latter is a Devo- nian form. The genus Ceratites is characteristically Triassic, but it is said to occur in the Devonian rocks. All the remain- ing genera are exclusively Secondary, the genera Baculites, Turrilites, Hamites, and Ptychoceras being confined to the Cre- taceous period. Of the Dibranchiate Cephalopoda the record is less perfect, as they have few structures which are capable of preservation. They attain their maximum, as fossils, shortly after their first appearance in the Secondary rocks, where they are represented by the large and important family of the Belemnitida. Some of the Teuthidce and Sepiadcz are found both in the Secondary and in the Tertiary rocks, and two species of Argonaut have been discovered in the later Tertiaries. No example of a Dibranchiate Cephalopod is known from the Palaeozoic de- posits, and the order attains its maximum at the present day. TABULAR VIEW OF THE CHIEF SUBDIVISIONS OF THE INVERTEBRATA. SUB-KINGDOM I.— PROTOZOA. CLASS I. GREGARINID^E. CLASS II. RHIZOPODA. Order i. Amcebea. 2. Foraminifera. 3. Radiolaria. 4. Spongida. CLASS III. INFUSORIA. Order i. Suctoria. 2. Ciliata. 3. Flagellata. SUB-KINGDOM II.— CCELENTERATA. CLASS I. HYDROZOA. Sub-class A. Hydroida. Order i. Hydrida. 2. Corynida. 3. Sertularida. 4. Campanularida. 3l6 MANUAL OF ZOOLOGY. Sub-class B. Siphonophora. Order 5. Calycophoridae. 6. Physophoridae. Sub-class C. Discophora. Order 7. Medusidae. Sub-class I). Lucernarida. OrderS. Lucernariadae. 9. Pelagidae. 10. Rhizostomidae. Sub-class E. Graptolitida. CLASS II. ACTINOZOA. Order i. Zoantharia. Sub-order a. Z. Malacodermata. b. Z. Sclerobasica. <:. Z. Sclerodermata. Order 2. Alcyonaria. Fam. a. Alcyonidse. b. Tubiporidae. c. Pennatulidae. d. Gorgonidse. Order 3. Rugosa. Order 4. Ctenophora. Sub-order a. Stenostomata. b. Eurystomata. SUB-KINGDOM III.— ANNULOIDA. CLASS I. ECHINODERMATA. Order i. Cystoidea. 2. Blastoidea. 3. Crinoidea. 4. Echinoidea. 5. Asteroidea. 6. Ophiuroidea. 7. Holothuroidea. CLASS II. SCOLECIDA. Division A. Platyelmia. Order i. Taeniada. 2. Trematoda. 3. Turbellaria. Sub-order a. Planarida. b. Nemertida. Division B. Nematelmia. Order 4. Acanthocephala. 5. Gordiacea. 6. Nematoda. SUBDIVISIONS OF INVERTEBRATA. 317 Division C. Rotifera. Order. Rotifera. SUB-KINGDOM IV.— ANNULOSA. DIVISION A. ANARTHROPODA. CLASS I. GEPHYREA. CLASS II. ANNELIDA. Order i. Hirudinea a. OligochEeta Abranchiata. ' CLASS III. CH^ETOGNATHA. DIVISION B. ARTHROPODA or ARTICULATA. CLASS I. CRUSTACEA. Sub -class I. Epizoa. Order i. Ichthyophthira. Sub-class II. Cirripedia. ( Balanidse. Order 2. Thoracica. < Verrucidse. ( Lepadidse. 3. Abdominalia. 4. Apoda. Sub-class III. Entomostraca. Order «;. Ostracoda ) T T . 6. Copepoda } Legion Lophyropoda. 7. Cladocera \ 8. Phyllopoda > Legion Branchiopoda. 9. Trilobita J 10. Merostomata. Sub-order a. Xiphosura. b. Eurypterida. Sub-class IV. Malacostraca. Order 1 1. Laemodipoda \ Division A. 12. Isopoda V Edriophthalmata> 13. Amphipoda J 14. Stomapoda ) Division B. 15. Decapoda J Podophthalmata. Tribe a. Macrura. b. Anomura. c. Brachyura. 3l8 MANUAL OF ZOOLOGY. CLASS II. ARACHNIDA. Division A. Trachearia. Order i. Podosomata. 2. Acarina. 3. Adelarthrosomata. Division B. Pulmonaria. Order 4. Pedipalpi. 5. Araneida. CLASS III. MYRIAPODA. Order i. Chilopoda. 2. Chilognatha. CLASS IV. INSECTA. Sub-class I. Ametabola. Order i. Anoplura. 2. Mallophaga. 3. Thy san lira. Sub-class II. Hemimetabola. Order 4. Hemiptera. 5. Orthoptera. 6. Neuroptera. Sub-class III. Holometabola. Order 7. Aphaniptera. 8. Diptera. 9. Lepidoptera. 10. Hymenoptera. 11. Strepsiptera. 12. Coleoptera. SUB-KINGDOM V.— MOLLUSCA. DIVISION A. MOLLUSCOIDA. Class I. Polyzoa. Order i. Phylactolsemata. .2. Gymnolsemata. Class II. Tunicata. Order i. Ascidia branchialia. 2. Ascidia abdominalia. 3. Ascidia larvalia. Class III. Brachiopoda. DIVISION B. MOLLUSCA PROPER. Class IV. Lamellibranchiata. Section a. Asiphonida. . b. Siphonida. SUBDIVISIONS OF INVERTEBRATA. 319 Class V. Gasteropoda. Sub-class I. Branchifera. Order i. Prosobranchiata. Section a. Siphonostomata. b. Holostomata. Order 2. Opisthobranchiata. Section a. Tectibranchiata. b. Nudibranchiata. Order 3. Nucleobranchiata (Heteropoda.) Fam. a. Firolidae. b. Atlantidas. Sub-class II. Pulmonifera. Section a. Inoperculata. b. Operculata. CtassVI. Pteropoda. Order i. Thecosomata. 2. Gymnosomata. Class VII. Cephalopoda. Order i. Tetrabranchiata. 2. Dibranchiata. PART II. VERTEBRATE ANIMALS VERTEBRATE ANIMALS. CHAPTER LIU. GENERAL CHARACTERS AND DIVISIONS OF THE VERTEBRATA. THE five sub-kingdoms which we have previously considered — viz., the Protozoa, Codenterata, Annuloida, Annulosa, and Mol- lusca — were grouped together by the French naturalist Lamarck to form one great division, which he termed Invertebrata, the remaining members of the animal kingdom constituting the division Vertebrata. The division Vertebrata, though includ- ing only a single sub-kingdom, is so compact and well-marked a division, and its distinctive characters are so numerous and so important, that this mode of looking at the animal kingdom is, at any rate, a very convenient one. The sub-kingdom Vertebrata may be shortly defined as com- prising animals in which the body is composed of a number of definite segments, arranged along a longitudinal axis ; the nervous system is in its main masses dorsal, and the neural and hcemal regions of the body are always completely shut off from one an- other by a partition ; the limbs are never more than four in number, and are always turned away from the neural aspect of the body ; mostly there is the bony axis known as the " spine" or " vertebral column" and in all the structure known as the " noto- chord" is present — in the embryo, at any rate. These charac- ters distinguish the Vertebrata, as a whole, from the Invtrte- brata; but it is necessary to define these broad differences more minutely, and to consider others which are of little less importance. One of the most obvious, as it is one of the most funda- mental, of the distinctive characters of Vertebrates is to be found in the shutting off of the main masses of the nervous 324 MANUAL OF ZOOLOGY. system from the general cavity of the body. In all Inverte- brate animals, without exception, the body (fig. 115, A) may be regarded as a single tube, enclosing all the viscera ; and consequently, in this case, the nervous system is contained within the general cavity of the body, and is not in any way shut off from the alimentary canal. The transverse section, Fig. 115. — A, Tranverse section of the body of one of the higher Invertebrata: a Body-wall ; b Alimentary canal ; c Haemal system ; n Nervous system. B, Trans- verse section of the body of a Vertebrate animal : a Body-wall ; b Alimentary canal ; c Haemal system ; « Sympathetic system of nerves ; n' Cerebro-spinal system of nerves ; ch Notochord. however, of a Vertebrate animal exhibits two tubes (fig. 115, B) one of which contains the great masses of the nervous system — that is, the " cerebro-spinal axis," or brain and spinal cord — whilst the other contains the alimentary canal and the chief circulatory organs, together with certain portions of the ner- vous system, known as the " ganglionic" or ," sympathetic" system. Leaving the cerebro-spinal centres out of sight for a moment, we see that the larger or visceral tube of a Vertebrate animal contains the digestive canal, the haemal system, and a gangliated nervous system. Now this is exactly what is con- tained in the visceral cavity of any of the higher Invertebrate animals ; and it follows from this, as pointed out by Von Baer, that it is the sympathetic nervous system of Vertebrates which is truly comparable to, and homologous with, the nervous sys- tem of Invertebrates. The cerebro-spinal nervous centres of the Vertebrata are to be regarded as something superadded, and not represented at all amongst the Invertebrata. The tube containing the cerebro-spinal centres is formed as follows : — At an early period in the development of the em- bryo of any Vertebrate animal, the portion of the ovum in which development is going on — the "germinal area" — be- comes elevated into two parallel ridges, one on each side of the middle line, enclosing between them a long groove, which is known as the " primitive groove" (fig. 1 16, A, B). The ridges which bound the primitive groove are known as the " laminse GENERAL CHARACTERS OF THE VERTEBRATA. 325 dorsales ;" and they become more and more raised up, till they ultimately meet in the middle line, and unite to form a tube, within which the cerebro-spinal nervous centres are developed. It follows from its mode of formation that the inner wall of the tube formed by the primitive groove, which remains as the septum between the cerebro-spinal canal and the body-cavity, is nothing more than a portion of the primitive wall of the body of the embryo. And there appears to be little doubt, as be- lieved by Remak and Huxley, that the cerebro-spinal nervous centres are " the result of a modification of that serous layer of the germ, which is continuous elsewhere with the epidermis" (Huxley). 1) Fig. 116. — Embryology of Vertebrata. A, Portion of the germinal area of the ovum of a Bitch, showing the primitive groove (after Bischoff). B, Profile view of the same. C, Diagram representing the amnion and allantois : e Embryo ; a Am- nion ; u Umbilical vesicle ; b Allantois ; f Pedicle of the allantois, afterwards the urinary bladder. D, Head of an embryo, showing the visceral arches (z> v). Another remarkable peculiarity as regards the nervous sys- tem is found in the fact that in no Vertebrate animal does the alimentary canal pierce the main masses of the nervous system, but turns away to open on the opposite side of the body. In most Invertebrates, on the other hand, in which there is a well-developed nervous system, this is perforated by the gullet, so that an cesophageal nerve-collar is formed, and some of the nervous centres become prse-cesophageal, whilst others are post-oesophageal. Furthermore, the floor of the "primitive groove" in the embryo of all Vertebrates has developed in it at an early period the structure known as the " notochord " or " chorda dorsalis" (fig. 115, B, ch). This structure, doubtfully present in any Invertebrate, is a semi-gelatinous or cartilaginous col- 326 MANUAL OF ZOOLOGY. lection of cells, forming a rod-like axis, which tapers at both ends, and extends along the floor of the cerebro-spinal canal, supporting the cerebro-spinal nervous centres. In some Ver- tebrates, such as the Lancelet (Amphioxus\ the notochord is persistent throughout life. In the majority of cases, however, the notochord is replaced before maturity by the structure known as the " vertebral column " or " backbone," from which the sub-kingdom Vertebrata originally derived its name. This is not the place for an anatomical description of the spinal column, and it is sufficient to state here that it is essen- tially composed of a series of cartilaginous, or more or less completely ossified, segments or vertebras, arranged so as to form a longitudinal axis, which protects the great masses of the nervous system. It is to be remembered, however, that all Vertebrate animals do not possess a vertebral column. They all possess a notochord; but this may be persistent, and in many cases the development of the spinal column is extremely imperfect. Another embryonic structure which is characteristic of all Vertebrates, is found in the so-called " visceral arches " and " clefts" (fig. 1 1 6, D). The "visceral arches" are a series of par- allel ridges running transversely to the axis of the body, situ- ated at the sides of, and posterior to, the mouth. As develop- ment proceeds, the intervals between these ridges become grooved by depressions which gradually deepen, until they become converted into a series of openings or " clefts," where- by a free communication is established between the upper part of the alimentary canal (pharynx) and the external medium. The limbs of Vertebrate animals are always articulated to the body, and they are always turned away from the neural aspect of the body. They may be altogether wanting, or they may be partially undeveloped ; but there are never more than two pairs, and they always have an internal skeleton for the attachment of the muscles of the limb. A specialised blood-vascular or " haemal " system is present in all the Vertebrata, and in all except one — the Amphioxus — there is a contractile cavity or heart, which never consists of less than two chambers provided with valvular apertures. In all the Vertebrata the heart is essentially a respiratory heart — that is to say, it is concerned with driving the impure or venous blood to the breathing-organs ; and in its simplest form (fishes) it is nothing more than this. In the higher Vertebrates, how- ever, there is superadded to this a pair of cavities which are concerned in driving the pure or arterial blood to the body. In the case of the Mammals, these two circulations are often GENERAL CHARACTERS OF THE VERTEBRATA. 327 spoken of as the "lesser" or "pulmonary" circulation, and the " greater " or " systemic " circulation. In all Vertebrates there is that peculiar modification of the venous system which is known as the " hepatic portal system." That is to say, a portion of the blood which is sent to the ali- mentary canal, instead of returning to the heart by the ordi- nary veins, is carried to the liver by a special vessel — the vena portcz — which ramifies through this organ after the manner of an artery. In all Vertebrates, also, is found the peculiar system of vessels known as the " lacteal system." This is to be regarded as an appendage of the venous system of blood-vessels, and consists of a series of vessels which take up the products of digestion from the alimentary canal, elaborate them, and finally empty their contents into the veins. Lastly, the masticatory organs of Vertebrates are modified portions of the walls of the head, and never " hard productions of the alimentary mucous membrane or modified limbs " (Huxley), as they are amongst the Invertebrata. The above are the leading characters of the Vertebrata as a whole ; but before going on to consider the primary divisions of the sub-kingdom, it may be as well to give a veiy brief and general description of the anatomy of the higher and more typical Vertebrates, commencing with their bony framework or skeleton. The skeleton of the Vertebrata may be regarded as consisting essentially of the bones which go to form the head and trunk on the one hand (sometimes called the "axial" skeleton), and of those which form the supports for the limbs (" appendicular" skeleton) on the other hand. The bones of the head and trunk may be looked upon as essentially composed of a series of bony rings or segments, arranged longitudinally, one behind the other. Anteriorly these segments are much expanded, and likewise much modified, to form the bony case which encloses the brain, and which is termed the cranium or skull. Behind the head the segments enclose a much smaller cavity, which is called the " neural " or spinal canal, as it encloses the spinal cord ; and they are arranged one behind the other, forming the vertebral column. The segments which form the vertebral column are called "vertebrae," and they have the following general structure: — Each vertebra (fig. 117, A) consists of a central piece, which is the fundamental and essential element of the vertebra, and is known as the "body" or "centrum" (c). From the upper or posterior surface of the centrum spring two bony arches (n n), which are called the/' neural arches" or "neu- 328 MANUAL OF ZOOLOGY. rapophyses," because they form with the body a canal — the " neural canal " — which encloses the spinal cord. From the point where the neural arches meet behind, there is usually developed a longer or shorter spine, which is termed the " spi- nous process " or " neural spine " (s). From the neural arches there are also developed in the typical vertebra two processes (aa\ which are known as the " articular " processes, or " zyga- pophyses." The vertebrae are united to one another partly by these, fyut to a greater extent by the bodies or " centra." From the side£ of the vertebral body, at the point of junction with the neural arches, there proceed two lateral processes (d d\ which are known as the " transverse processes." (In the typical vertebra the transverse processes consist each of two pieces, an anterior piece or " parapophysis," and a posterior piece or " diapophysis.") These elements form the vertebra of the human anatomist, but the " vertebra " of the transcendental anatomist is completed by a second arch which is placed be- neath the body of the vertebra, and which is called the " hae- mal " arch, as it includes and protects the main organs of the circulation. This second arch is often only recognisable with great difficulty, as its parts are generally much modified, but a good example may be obtained in the human chest, or in the caudal vertebra of a bony fish. Fig. 117. — A, Lumbar vertebra of a Whale: c Body or centrum ; n n Neural arches ; s Neural spine ; a a Articular processes ; dd Transverse processes. B, Diagram of a thoracic vertebra : c Centrum ; n n Neural arches enclosing the neural canal ; s Neural spine ; r r Ribs, assisting in the formation of the haemal arch ; pp Costal car- tilages ; b Sternum, with haemal spine. (After Owen.) The haemal arch in the case of the human thorax (fig. 117, B) is formed by the ribs (r r) and the costal cartilages GENERAL CHARACTERS OF THE VERTEBRATA. 329 and is completed in front by the breast-bone or sternum (b), which in some cases — but not in man — develops a spine (the haemal spine), which corresponds to the neural spine on the opposite aspect of the vertebra. It follows from the above, that the typical vertebra consists of a central piece or body from which two arches are given off, one of which protects the great masses of the nervous system, and is therefore said to be " neural ; " whilst the other pro- tects the main organs of the circulation, and is therefore said to be "haemal." The correspondence of the typical bony segment or vertebra with the doubly tubular structure of the body in all Vertebrates is thus too obvious to require to be specially pointed out. As a general rule, the vertebral column is divisible into a number of distinct regions, of which the following are recog- nisable in man and in the higher Vertebrata : — i. A series of vertebrae which compose the neck, and constitute the "cervical region" of the spine (fig. 118, c). 2. A number of vertebrae Fig. 1 1 8. —Skeleton of the Beaver (Castor fiber], showing the different- regions of the vertebral column, c Cervical region ; d Dorsal region ; b Lumbar region ; j Sacrum ; t Caudal region. which usually carry well-developed ribs, and form the " dorsal region " (d). 3. A series of vertebrae which form the region of the loins, or "lumbar region" (b). 4. A greater or less 330 MANUAL OF ZOOLOGY. number of vertebrae which constitute the " sacral region," and are usually amalgamated or " anchylosed " together to form a single bone, the " sacrum " (s). 5. The spinal column is completed by a variable number of vertebras which constitute the " caudal " region, or tail (/). As regards the skull of the Vertebrata, it has been thought advisable not to enter into any general details here, partly because the subject is one which can only be properly dis- cussed in a work specially devoted to Human or Comparative Anatomy, and partly because there is still much diversity of opinion as to the exact composition of the skull. There is, however, a very general concurrence of opinion that the skull is composed of a number of separate segments, and this is a point which it is important to remember. By Owen, and by many other competent authorities, these cranial segments are looked upon as being nothing more than so many vertebra, the neural canals of which are greatly expanded to enclose the brain, whilst the haemal arches are very greatly modified to serve different purposes. This view is not accepted by Hux- ley, but the general fact that the skull is composed of separate segments appears to be universally admitted. The only portion of the bony framework of the head which it is absolutely essential to understand, is the lower jaw or " mandible." The lower jaw is sometimes wanting, but when present, it consists in all Vertebrata of two halves or " rami," which are united to one another in front, and articulate separately with the skull behind. In many cases, each half, or " ramus," of the lower jaw consists of several pieces united to one another by sutures ; but in the Mammalia each ramus consists of no more than a single piece. The two rami are very variously connected with one another, being sometimes only joined by ligaments and muscles, sometimes united by cartilage or by bony suture, -and sometimes fused or anchylosed with one another, so as to leave no evidence of their true composition. The mode by which each ramus of the lower jaw articulates with the skull also varies. In the Mammalia the lower jaw articulates with a cavity formed on what is known to human anatomists as the temporal bone ; but in Birds and Reptiles, the lower jaw articulates with the skull, not directly, but by the intervention of a special bone, known as the "quadrate bone" or " os quad- ratum" As regards the limbs of Vertebrates, whilst many differences exist, which will be afterwards noticed, there is a general agreement in the parts of which they are composed. As a rule, each pair of limbs is joined to the trunk by means of a GENERAL CHARACTERS OF THE VERTEBRATA. 331 series of bones which also correspond to one another in general structure. The fore-limbs, often called the " pectoral " limbs, are united with the trunk by means of a bony arch, which is called the "pectoral" or "scapular" arch; whilst the hind- limbs are similarly connected with the trunk by means of the "pelvic arch." In giving a general description of the parts which compose the limbs and their supporting arches, it will be best to take the case of a Mammal, and the departures from this type will then be readily recognised. The pectoral or scapular arch consists usually of three bones, the " scapula " or shoulder-blade, the " coracoid," and the " clavicle " or collar-bone ; but in the great majority of the Mammals, the coracoid is anchylosed with the scap- ula, of which it forms a mere process. The scapula or shoulder-blade (fig. 119, s) is usually placed outside the ribs, and it forms, either alone or in conjunction with the other bones of the shoulder- girdle, the cavity with which the upper arm is articulated. The coracoid, though rarely existing as a distinct bone in the Mammals, plays a very important part in other Vertebrates, as we shall see hereafter. The clavicles are often wanting, or rudimentary, and they are the least essential elements of the scapular arch. The fore-limb proper consists, firstly, of a single bone which forms the upper arm, and which is known as the humerus (h). This arti- culates above with the shoulder-girdle, and is followed below by the fore-arm, which consists of two bones, called the radius and ulna. Of these the radius is chiefly concerned with carrying the hand. The radius and ulna are fol- lowed by the bones of the wrist, which are usually composed of several bones, and constitute what is called the carpus (d). These support the bones of the root of the hand, which vary in number, but are always more or less cylindrical in shape. They constitute what is called the metacarpus. The bones of the metacarpus carry the digits, Fig. 119. — Pectoral limb (arm) of Chimpanzee. (After Owen). c Cla- vicle ; ^ Scapula or shoul- der-blade ; h Humerus ; r Radius ; « Ulna ; d Bones of the wrist, or car- pus ; m Metacarpus ; p Phalanges of the fingers. 332 MANUAL OF ZOOLOGY. which also vary in number, but are composed each of from two to three cylindrical bones, which are known as the phalanges (p\ Homologous parts are, as a rule, readily recognisable in the hind-limb. The pelvic arch, by which the hind-limb is united with the trunk, consists of three pieces — the ilium, ischium, and pubes — which are usually anchylosed together, and form conjointly what is known as the innominate bone (fig. 120, /'). In most Mammals, the two innominate bones unite in front by a ligamentous or cartilaginous union and they constitute, with the sacrum, what is known as the pelvis. The hind -limb proper consists of the following parts : — i. The thigh- bone or femur, corresponding with the humerus in the fore-limb. 2. The bones of the shank, corresponding with the radius and ulna of the fore-limb, and known as the tibia and fibula. Of these, the tibia is mainly or altogether con- cerned in carrying the foot, and it is thus shown to correspond to the radius, whilst the fibula corresponds to the ulna. 3. The small bones of the ankle, known as the tarsus, and varying in number in different cases. 4. A variable number of cylindrical bones (normally five), which are called the metatarsus, and which correspond to the metacarpus. 5. Lastly, the metatarsus carries the digits, which consist of from two 'to three small bones or phalanges, as Fig. 120. — Pelvic in the fore-limb. ofmb cSpaJSee The diSesti™ system of Vertebrates will be (after Owen). * spoken of at greater length hereafter; but a >r±,aortbh°igh- brief sketch may be siven here of the gener^ bone; t Tibia; s phenomena of digestion. All Vertebrate ani- m Metatarsus!*/ mals are provided with a mouth for the re- Phaianges of the ception of food, and in the great majority of cases the mouth is furnished with teeth, which are used sometimes merely to hold to the prey, but more commonly to cut and bruise the food, and thus render it capable of digestion. The food is also generally subjected in the mouth to the action of "salivary" glands, the se- cretion of which serves not only to moisten the food, and thus mechanically assist deglutition, but also to render soluble the starchy elements of the food. The food is next swallowed, or, in other words, is transferred from the mouth to the stomach, GENERAL CHARACTERS OF THE VERTEBRATA. 333 this being effected by a complicated arrangement of muscles, whereby the food is forced down the gullet (oesophagus) to the proper digestive cavity or stomach. In the stomach (fig. 121, s) the food is subjected to two sets of actions ; it is mechanically triturated and ground down by the constant contractions of the muscular walls of the stomach; and it is subjected to the chemical action of a special fluid secreted by the stomach, and called the " gastric juice." This fluid has the power of reducing albuminoid substances to a soluble form, and by its action the food is ultimately reduced to a thick acid fluid, called the " chyme." Leaving the stomach by its lower aperture (the pylorus), the chyme passes into the intestine, the first portion of which is divided into several sections, but is collectively known as the " small intestine." Here the chyme is sub- jected to the action of three other digestive fluids; the bile, secreted by a special organ, the liver; the pancreatic juice, secreted by another gland, the pancreas; and the intes~ final juice, secreted by certain glands situated in the mucous membrane of the intestine itself. The result of the whole process is that the " chyme " is ultimately converted into a white, alkaline, milky fluid, which is called " chyle." The indigestible portions of the food pass from the small in- testine into a tube of larger dimen- sions, called the "large intestine." Such portions of the food as are still soluble, and capable of being employed in nutrition, are here taken up into the blood, the use- less remainder being ultimately ex- pelled by an anal aperture. The last portion of the large intestine is usually less convoluted than the rest, and IS Called the " rectum." The fluid and originally soluble portions of the food, and the chyle which is formed in the process of digestion, are taken into the blood, the losses of which they serve to repair. Part of the nutritive materials of the food is taken up directly by the blood-vessels, and is conveyed by the "vena portse" to the s Stomach; sm Small intestine; Itn Large intestine; r Rectum, terminating in the aperture of the anus. 334 MANUAL OF ZOOLOGY. liver, whence it ultimately reaches the great veins which go to the heart. The greater part, however, of the liquefied food, constituting the chyle, is taken up, not by the blood-vessels, but by a special set of tubes, which form a network in the walls of the intestine, and are known as the " lacteals." In these vessels, and in certain glands which are developed upon them, the chyle undergoes still further elaboration, and is made more similar in composition to the blood itself. All the lacteal vessels ultimately unite into one or more large vessels which open into one of the veins, so that all the chyle is thus finally added to the mass of the circulating blood. The blood, then, or nutrient fluid from which the tissues are built up, is formed in this way out of the materials which are taken into the alimentary canal as food. In all the Vertebrata, with the single exception of the Lancelet (Amphioxus], the blood is of a red colour when viewed in mass. This is due to & Fig. 122. — Blood-corpuscles of Vertebrata. a Red blood-discs of man ; b Blood- discs of Goose ; c Crocodile ; d Frog ; e Skate. the presence in it of an incredible number of microscopical bodies, which are known as the " blood-corpuscles," the fluid in which these float being itself colourless (fig. 122). In all the Vertebrata the blood is distributed through the body by means of a system of closed tubes, which constitute the " blood-vessels ; " and in all except the Lancelet, the means of propulsion are derived from a contractile muscular cavity or " heart," furnished with valvular apertures. In the most complete form of circulation, as seen in Birds and Mammals, tfye heart is essentially a double organ, composed of two halves, each of which consists of two cavities, an auricle and a ventricle. The right side of the heart is wholly concerned with the "lesser" or pulmonary circulation, whilst the left side is concerned with driving the blood to all parts of the body (systemic circulation). The modifications of the circulat- ory process will be noticed in speaking of the different classes of Vertebrates, but a brief sketch may be given here of the circu- lation in its most complete form, as in a Mammal. In such a case, the venous or impure blood, which has circulated through the body and has parted with its oxygen, is returned by the great veins to the right auricle. From the right auricle (fig. 1 23, #) the GENERAL CHARACTERS OF THE VERTEBRATA. 335 blood passes by a valvular aperture into the right ventricle (v), whence it is driven through the pulmonary artery to the lungs. The right side of the heart is therefore wholly respiratory in its function. Having been sub- mitted to the action of the lungs, and having given off carbonic acid and taken up oxygen, the blood now becomes arterial, and is re- turned by the pulmonary veins to the left auricle (a1). From the left auricle the aerated blood passes through a valvular aperture into the left ventricle (if), whence it is pro- pelled to all parts of the body by means of a great systemic vessel, the " aorta." The left side of the heart is therefore wholly occu- pied in carrying out the " greater" or systemic circulation. The purification of the blood is carried out in all Vertebrates by means of distinct respiratory organs, assisted to a greater or less extent by the skin. In the Fishes, and in the Amphibians to some extent, the process of respiration is carried on by means of branchice or gills — that is, by organs adapted for breathing air dissolved in water. These are therefore often spoken of as " Branchiate " Vertebrates ; but the Amphibians always develop true lungs in the later stages of their existence. In the Reptiles, Birds, and Mammals, branchiae are never developed, and the respiration is always carried on by means of true lungs — that is, by organs adapted for breathing air directly. These are therefore often spoken of as the " Abranchiate " Vertebrates. The waste substances of the body — of which the most im- portant are water, carbonic acid, and urea — are got rid of by the skin, lungs, and kidneys. Under ordinary circumstances, the lungs are mainly occupied with the excretion' of carbonic acid and watery vapour. The skin chiefly gets rid of superflu- ous moisture, but can also in many animals excrete carbonic acid as well. The kidneys are present in almost all Vertebrate Fig. 123. — Diagram of the circulation of a Mammal. The venous system is marked black ; the arterial system is left white. a Right auricle; v Right ventricle ; p Pulmonary artery, gs; •u' Left ventricle ; & Aorta, carrying arterial blood to the body ; c Vena cava carrying venous blood to the heart. 336 MANUAL OF ZOOLOGY. animals, and their function is mainly to excrete water, and the nitrogenous substance known as urea. In the majority of cases the fluid excreted by the kidneys is conveyed to the ex- terior by means of two tubes known as the ureters, which empty themselves into a common receptacle, the urinary bladder. In some cases, however, the ureters open into the termination of the alimentary canal (rectum). The nervous system of Vertebrate animals usually exhibits a well-marked division into two parts — the cerebro-spinal system, and the sympathetic system. The cerebro-spinal system of nerves constitutes the great mass of the nervous system of Vertebrates, and usually exhibits a well-marked separation into spinal cord (myelon) and brain (encephalori). The pro- portion borne by the brain to the spinal cord differs much in different cases ; and in the Lancelet a brain can hardly be said to be present at all. As already said, the brain and spinal cord are always completely shut off from the visceral cavity, and they are placed upon the dorsal surface of the body. The nerves given off from the cerebro-spinal axis are symmetrically disposed on the two sides of the body, and they are mainly concerned with the functions of " animal " life — that is to say, with sensation and locomotion. The sympathetic system of nerves is unsymmetrically disposed to a greater or less extent, and presides mainly over the functions of " organic," or " vege- tative " life, being mainly concerned with regulating the func- tions of digestion and respiration, and the circulation of the blood. In its most fully developed form it consists of a double gangliated cord placed in the visceral cavity on the under sur- face of the spine, and of a series of nervous ganglia, united by nervous cords, and scattered mainly over the great viscera of the thorax and abdomen. The organs of the senses are well developed in the Vertebrata, and those appropriated to the senses of sight, hearing, smell, and taste are protected within bony cavities of the head. The perfection of the senses differs much in different cases, but they are probably never wholly wanting in any Vertebrate animal. There are cases in which vision must be of the most rudimen- tary character ; but even in these cases it is probable that there is a perception of light, even if there is no power of distinguish- ing objects. The only cases in which it would appear that vision is really altogether absent, are those of animals placed under the wholly abnormal condition of spending their exist- ence in darkness (such as the Proteus anguinus of the caves of Illyria). Smell, hearing, and taste are probably rarely, if ever, altogether absent in Vertebrates ; though in many cases their DIVISIONS OF THE VERTEBRATA. 337 organs are very rudimentary. Touch, or " tactile sensibility," is usually possessed to a greater or less degree by the entire surface of the body; but the sense of touch is.generally localised in certain particular parts, such as the appendages of the mouth, the lips, the tongue, or the digits. In all Vertebrata without exception reproduction is carried on by means of the sexes, and in all the sexes are in different individuals. No Vertebrate animal possesses the power of re- producing itself by fission or gemmation ; and in no case are composite organisms or colonies produced. Most of the Ver- tebrates are oviparous, that is to say, the ova are expelled from the body of the parent either before or very shortly after im- pregnation. In other cases, the eggs are retained within the body of the parent until the young are hatched, and in these cases the animals are said to be ovo-viviparous. In other cases, again, not only is the egg hatched within the parent, but the embryo is retained within the body of the mother until its de- velopment has been carried out to a greater or less extent; and these animals are said to be viviparous. DIVISIONS OF THE VERTEBRATA. — The sub-kingdom Verte- brata is divided into the five great classes of the Fishes (Pisces), Amphibians (Amphibia), Reptiles (Reptilia), Birds (Aves), and Mammals (Mammalia). So far there is perfect unanimity; but when it is inquired into what larger sections the Vertebrata may be divided, there is much difference of opinion. Here, the divisions proposed by Professor Huxley will be adopted, but it is necessary that those employed by other writers should be mentioned and explained. One of the commonest methods of classifying the Vertebrata is to divide them into the two primary sections of the Branch- iata and Abranchiata. Of these, the Branchiate section in- cludes the Fishes and Amphibians, and is characterised by the fact that the animal is always provided at some period of its life with branchiae or gills. The Abranchiate section includes the Reptiles, Birds, and Mammals, and is characterised by the fact that the animal is never provided at any time of its life with gills. Additional characters of the Branchiate Vertebrates are, that the embryo is not furnished with the structures known as the amnion and allantois. Hence the Branchiate Vertebrates are often spoken of as the Anamniota and as the Anallantoidea. In the Abranchiate Vertebrates, on the other hand, the embryo is always provided with an amnion and allantois, and hence this section is spoken of as the Amniota or as the Allantoidea* * The amnion (fig. 116, C) is a membranous sac, containing a fluid — the liquor amnii — and completely enveloping the embryo. It consti- VOL. II. Y 338 MANUAL OF ZOOLOGY. By Professor Owen the Vertebrata are divided into the two primary sections of the Hcematocrya and the H&matotherma, the characters of the blood being taken as the distinctive character. The Hcematocrya or Cold-blooded Vertebrates comprise the Fishes, Amphibia, and Reptiles, and are characterised by their cold blood, and imperfect circulation. The Hcematotherma or Warm-blooded Vertebrates comprise the Birds and the Mam- mals, and are characterised by their hot blood, four-chambered heart, and complete separation of the pulmonary and systemic circulations. The chief objection to this division lies in the separation which is effected between the Reptiles and the Birds, two classes which are certainly very nearly allied to one another. By Professor Huxley the Vertebrata are divided into the fol- lowing three primary sections : — I. ICHTHYOPSIDA. — This section comprises the Fishes and the Amphibians, and is characterised by the presence at some period of life of gills or branchiae, the absence of an amnion, the absence or rudimentary condition of the allantois, and the possession of nucleated red blood-corpuscles. II. SAUROPSIDA. — This section comprises the Birds and the Reptiles, and is characterised by the constant absence of gills, the possession of an amnion and allantois, the articulation of the skull with the vertebral column by a single occipital con- dyle ; the composition of each ramus of the lower jaw of several pieces, and the articulation of the lower jaw with the skull by the intervention of an " os quadratum;" and, lastly, the posses- sion of nucleated red blood-corpuscles. III. MAMMALIA. — This section includes the single class of the Mammals, and agrees with the preceding in never possess- ing gills, and in having an amnion and allantois. The Mam- malia, however, differ from the Sauropsida in the fact that the skull articulates with the vertebral column by two occipital condyles ; each ramus of the lower jaw is simple, composed of tutes one of the so-called "foetal membranes," and is thrown off at birth. The allantois (fig. 116, C) is an embryonic structure, which is developed out of the middle or " vascular " layer of the germinal membrane. It ap- pears at first as a solid, pear-shaped, cellular mass, arising from the under part of the body of the embryo. In the process of development, the allan- tois increases largely in size, and becomes converted into a vesicle which envelops the embryo in part or wholly. It is abundantly supplied with blood, and is the organ whereby the blood of the foetus is aerated. The part of the allantois which is external to the body of the embryo is cast off at birth; but the portion which is within the body is retained and is con- verted into the urinary bladder. DIVISIONS OF THE VERTEBRATA. 339 a single piece, and the lower jaw is united with the temporal (squamosal) element of the skull, and is not articulated to a quadrate bone. There are special glands — the mammary glands — for the nourishment of the young for a longer or shorter period after birth, and the red blood-corpuscles are non- nucleated. 340 MANUAL OF ZOOLOGY. DIVISION L ICHTHYOPSIDA. CHAPTER LIV. CLASS L— PISCES. THE first class of the Vertebrata is that of the Fishes (Pisces), which may be broadly defined as including Vertebrate animals which are provided with gills throughout the whole of life; the heart, when present, consists (with one exception) of a single au- ricle and a single ventricle ; the blood is cold; the limbs, when present, are in the form of fins, or expansions of the integument; and there is neither an amnion nor allantois in the embryo, unless the latter is represented by the urinary bladder. In form, Fishes are adapted for rapid locomotion in water, the shape of the body being such as to give rise to the least possible friction in swimming. To this end also, as well as for purposes of defence, the body is usually enveloped with a coating of scales developed in the inferior or dermal layer of the skin. The more important modifications in the form of these dermal scales are as follows : I. Cycloid scales (fig. 124, a), consisting of thin, flexible, horny scales, circular or elliptical in shape, and having a more or less completely smooth outline. These are the scales which are character- istic of most of the ordinary bony fishes. II. Ctenoid scales (fig. 124, b\ also consisting of thin horny plates, but having their posterior margins fringed with spines, or cut into Fig. 124.— Scales of different fishes. COmb-Hke projections. III. Gail- iSft^T^Jrid'SS ^scales, composed of an inferior (Thornback); d Ganoid scales layer Composed of bone, COVCred by a superficial layer of hard po- lished enamel (the so-called " ganoine "). These scales (fig. CHARACTERS OF FISHES. 34! 1 24, d) are usually much larger and thicker than the ordinary- scales, and though they are often articulated to one another by special processes, they only rarely overlap. IV. Placoid scales, consisting of detached bony grains, tubercles, or plates, of which the latter are not uncommonly armed with spines (fig. 124, c). In most fishes there is also to be observed a line of peculiar scales, forming what is called the " lateral line." Each of the scales in this line is perforated by a tube leading down to a longitudinal canal which runs along the side of the body, and is connected with cavities in the head. The function of this singular system has been ordinarily believed to be that of se- creting the mucus with which the surface of the body is covered; but it seems to be more probably sensory in function, and to be connected with the sense of touch. As regards their true osseous system or endoskeleton, Fishes vary very widely. In the Lancelet there can hardly be said to be any skeleton, the spinal cord being simply supported by the gelatinous notochord, which remains throughout life. In others the skeleton remains permanently cartilaginous j in others it is partially cartilaginous and partially ossified ; and, lastly, in most modern fishes it is entirely ossified or converted into bone. Taking a bony fish (fig. 125) as in this respect a typical example of the class, the following are the chief points in the osteology of a fish which require notice : — d' Fig. 125.— Skeleton of the common Perch (Percaflumatilis.} p one of the pectora fins ; v One of the ventral fins ; a Anal fin, supported upon interspinous bones (/) ; c Caudal fin ; d First dorsal fin ; d' Second dorsal fin, both supported upon interspinous bones; ii Interspinous bones; rRibs; s Spinous processes of vertebrae ; h Hsemal processes of vertebrae. The vertebral column in a bony fish consists of vertebrae, which are hollow at both ends, or biconcave, and are techni- 342 MANUAL OF ZOOLOGY. cally said to be " amphiccelous." The cup-like margins of the vertebral bodies are united by ligaments, and the cavities formed between contiguous vertebrae are filled with the gela- tinous remains of the notochord. This elastic gelatinous sub- stance acts as a kind of ball-and-socket joint between the bodies of the vertebrae, thus giving the whole spine the extreme mo- bility which is requisite for animals living in a watery medium. The ossification of the vertebrae is often much more imperfect than the above, but in no case except that of the Bony Pike (Lepidosteus) is ossification carried to a greater extent than this. In this fish, however, the vertebral column is composed of "opisthocoelous" vertebrae — that is, of vertebrae the bodies of which are concave behind and convex in front. The entire spinal column is divisible into not more than two distinct re- gions, an abdominal and a caudal region. The abdominal vertebrae possess a superior or neural arch (through which passes the spinal cord), a superior spinous process (neural spine), and two transverse processes to which the ribs are usually attached. The caudal vertebrae (fig. 125) have no marked transverse pro- cesses ; but, in addition to the neural arches and spines, they give off an inferior or hcemal arch below the body of the verte- bra, and the haemal arches carry inferior spinous processes (haemal spines). The ribs of a bony fish are attached to the transverse pro- cesses, or to the bodies of the abdominal vertebrae, in the form of slender curved bones which articulate with no more than one vertebra each, and that only at a single point. Unlike the ribs of the higher Vertebrates, the ribs do not enclose a thoracic cavity, but are simply embedded in the muscles which bound the abdomen. Usually each rib gives off a spine-like bone, which is directed backwards amongst the muscles. Inferiorly the extremities of the ribs are free, or are rarely united to der- mal ossifications in the middle line of the abdomen ; but there is never any breast-bone or sternum properly so called. The only remaining bones connected with the skeleton of the trunk are the so-called interspinous bones (fig. 125, ii). These form a series of dagger-shaped bones plunged in the middle line of the body between the great lateral muscles which make up the greater part of the body of a fish. The internal ends or points of the interspinous bones are attached by ligament to the spinous processes of the vertebrae ; whilst to their outer ends are articulated the "rays " of the so-called " median " fins, which will be hereafter described. As a rule, there is only one interspinous bone to each spinous process, but in the Flat-fishes (Sole, Turbot, &c.) there are two. CHARACTERS OF FISHES. 343 Beside the fins which represent the limbs (pectoral and ventral fins), fishes possess other fins placed in the middle line of the body, and all of these alike are supported by bony spines or "rays," which are of two kinds, termed respectively " spi- nous rays" and " soft rays." The " spinous rays" are simple bony spines, apparently composed of a single piece each, but really consisting of two halves firmly united along the middle line. The " soft rays " are composed of several slender spines proceeding from a common base, and all divided transversely into numerous short pieces. The soft rays occur in many fishes in different fins, but they are invariably found in the caudal fin or tail (fig. 125, c). The rays of the median fins, whatever their character may be, always articulate by a hinge-joint with the heads of the interspinous bones. The skull of the bony fishes is an extremely complicated structure, and it is impossible to enter into its composition here. The only portions of the skull which require special mention are the bones which form the gill-cover or operculum, Fig. 126.— Skull of Cod (Morrhua vulgaris}—Cuvier. a Urohyal ; b Basihyal ; c Ceratohyal ; d Branchiostegal rays; / Prae-operculum ; o Operculum proper; s Sub- operculum ; t Inter-operculum ; m Mandible ; n Inter-maxillary bone. and the hyoid bone with its appendages. For reasons con- nected with the respiratory process in fishes, as will be after- 344 MANUAL OF ZOOLOGY. wards seen, there generally exists between the head and the scapular arch a great cavity or gap on each side, within which are contained the branchiae. The cavity thus formed opens externally on each side of the neck by a single vertical fissure or " gill-slit," closed by a broad flap, called the " gill-cover " or " operculum," and by a membrane termed the " branchi- ostegal membrane." The gill-cover (fig. 126, /, 0, s, i) is composed of a chain of broad flat bones, termed the opercular bones. Of these, the innermost articulates with the skull (tympano-mandibular arch), and is called the " praa-operculum ; " the next is a large bone called the "operculum" proper; and the remaining two bones, called respectively the "sub-operculum" and "inter-operculum," form, with the operculum proper, the edge of the gill-cover. These various bones are united together by membrane, and they form collectively a kind of movable door, by means of which the branchial chamber can be alternately opened and shut. Besides the gill-cover, however, the branchial chamber is closed by a membrane called the " branchiostegal mem- brane," which is attached to the os hyoides. The membrane is supported and spread out by a number of slender curved spines, which are attached to the lateral branches of the hyoid bone, act very much as the ribs of an umbrella, and are known as the "branchiostegal rays" (fig. 126, d). The hyoid arch of fishes is attached to the temporal bones of the skull by means of two slender styliform bones, which correspond to the styloid processes of man, and are called the " stylohyal " bones (fig. I27,/). The rest of the hyoid arch is composed of a central portion and two lateral branches. Each branch is composed of the following parts : — i. A triangular bone attached above to the stylohyal, and termed the " epihyal bone" (fig. 127, e) ; 2. A much longer bone, known as the " ceratohyal " (d). The central portion of the hyoid arch is made up of two small polyhedral bones — the " basihyals " (b). From the basihyal there extends forwards in many fishes a slender bone, which supports the tongue, and is termed the " glossohyal " or " lingual " bone (a). There is also another compressed bone, which extends backwards from the basihyals, and which is known as the " urohyal bone " (c). This last- mentioned bone is of importance, as it often extends back- wards to the point of union of the coracoid bones, and thus forms the isthmus which separates the two branchial apertures. From the outer margins of the epihyal and ceratohyal bones on each side arise the slender curved " branchiostegal rays," which have been previously mentioned. There are usually CHARACTERS OF FISHES. 345 seven of these on each side. Above the urohyal, and attached in front to the body of the os hyoides, is a chain of bones, placed one behind the other, and termed by Owen the " basi- Fig. 127. — Os hyoides, branchiostegal rays, and scapular arch of the Perch (after Cuvier). ss Supra-scapula ; j Scapula ; co Coracoid ; cl Supposed representative of the clavicle ; a Glossohyal bone ; b Basihyal ; c Urohyal ; d Ceratohyal ; e Epihyal ; ./Stylohyal; br Branchial arches; t Branchiostegal rays. branchial bones." Springing from these are four bony arches — the " branchial arches " — which proceed upwards to be con- nected superiorly by ligament with the under surface of the skull. The branchial arches — as will be subsequently de- scribed— carry the branchiae, and each is composed of two main pieces, termed respectively the " cerato-branchial " and " epi-branchial " bones. The second and third arches are con- nected with the skull by the intervention of two small bones, often called the " superior pharyngeal bones," but termed by Owen the " pharyngo-branchial " bones. The limbs of fishes depart considerably from the typical form exhibited in the higher Vertebrates. One or both pairs of limbs may be wanting, but when present the limbs are always in the form of fins — that is, of expansions of the integument 346 MANUAL OF ZOOLOGY. strengthened by bony or cartilaginous fin-rays. The anterior limbs are known as the pectoral fins, and the posterior as the ventral fins; and they are at once distinguished from the so-called "median" fins by being always symmetrically dis- posed in pairs. Hence they are often spoken of as the paired fins. The scapular arch (figs. 127, 128) supporting the pec- toral limbs is usually joined to the skull (occipital bone), and consists of the following pieces on each side : — i. The supra- scapula (ss) ; 2. The scapula (s), articulating with the former; and, 3. The coracoid (co), attached above with the scapula, and Fig. 128.— Pectoral limbs of Fishes (after Owen). A, Cod (Morrhua vulgaris) ; B, Angler (Lophius}. ss Supra-scapula ; s Scapula ; co Coracoid ; r Radius ; u Ulna ; cc Carpal bones ; f Fin-rays, representing the metacarpus and phalanges of the fingers. united below, by ligament or suture, with the coracoid of the opposite side, thus completing the pectoral arch. Lastly, there is often another bone, sometimes single, but oftener of two CHARACTERS OF FISHES. 347 pieces, attached to the upper end of the coracoid, and this is believed to represent the collar-bone or clavicle.* The fore-limb possesses in a modified form most of the bones which are present in the higher Vertebrata. The hum- eruSj or bone of the upper arm, is usually wanting, or it is alto- gether rudimentary. A radius and ulna (fig. 128, r, u) are usually present, and are followed by a variable number of bones, which represent the carpus, and some of which some- times articulate directly with the coracoid. The carpus is fol- lowed by the " rays " of the fin proper, these representing the metacarpal bones and phalanges. The hind-limbs or " ventral fins" are wanting in many fishes, and they are less developed and less fixed in position than are the pectoral fins. In the ventral fins no representatives of the tarsus, tibia and fibula, or femur, are ever developed. The rays of the ventral fins — representing the metatarsus and the phalanges of the toes — unite directly with a pelvic arch, which is composed of two sub-triangular bones, united in the middle line and believed to represent the ischia. The imperfect pelvic arch, thus constituted, is never united to the vertebral column in any fish. In those fishes in which the ventral fins are " abdominal " in position (i.e., placed near the hinder end of the body) the pelvic arch is suspended freely amongst the muscles. In those in which the ventral fins are "thoracic" or "jugular" (*>., placed beneath the pectoral fins, or on the sides of the neck) the pelvic arch is attached to the coracoid bones of the scapular arch, and is therefore wholly removed from its proper vertebra. In addition to the pectoral and ventral fins — the homologues of the limbs — which may be wanting, fishes are furnished with certain other expansions of the integument, which are " median " in position, and must on no account be confounded with the true "paired" fins. These median fins are variable in number, and in some cases there is but a single fringe running round the posterior extremity of the body. In all cases, however, the median fins are " azygous " — that is to say, they occupy the middle line of the body, and are not sym- metrically disposed in pairs. Most commonly, the median fins consist of one or two expansions of the dorsal integument, called the "dorsal fins" (fig. 129, dy d') ; one or two on the ventral surface near the anus — the " anal fins " (fig. 129, a) • and a broad fin at the extremity of the vertebral column, called the * These are the views entertained by Owen as to the composition and nature of the pectoral arch of fishes, but they are dissented from by Mr Parker, one of the greatest living authorities on this subject. 348 MANUAL OF ZOOLOGY. " caudal fin " or tail (c). In all cases, the rays which support the median fins are articulated with the so-called interspinous bones, which have been previously described. Fig. 129. — Outline of a fish (Perca granulata), showing the paired and unpaired fins. / One of the pectoral fins ; v One of the ventral fins ; d First dorsal fin ; d' Second dorsal fin ; a Anal fin ; c Caudal fin. . The caudal fin or tail of fishes is always set vertically at the extremity of the spine, so as to work from side to side, and it is the chief organ of progression in the fishes. In its vertical position and in the possession of fin-rays, it differs altogether from the horizontal integumentary expansion which constitutes the tail of the Whales, Dolphins, and Sirenia (Dugong and Manatee). In the form of the tail fishes exhibit two very distinct types of structure, termed respectively the "homocercal" and " hetero- cercal" type of tail (fig. 130). The homocercal tail is the one which most commonly occurs in our modern fishes, and it is characterised by the fact that the two lobes of the tail are equal, and the vertebral column, instead of being prolonged into the upper Fig. 130.— Tails of different fishes, lobe of the tail, stops short at a. Homocercal tail (Sword -nsh); • -L T ±1- -L i i ± -i b Heterocercai tail (Sturgeon). its base. In the hetcrocercal tail, on the other hand, the vertebral column is prolonged into the upper lobe of the tail, so that the tail becomes unequally lobed, its greater portion being placed CHARACTERS OF FISHES. 349 below the spine. Even where the vertebral column is not pro- longed into the upper lobe, the tail may nevertheless become heterocercal, in consequence of a great development of the haemal spines as compared with the neural spines of the vertebrae. The process of respiration in all fishes is essentially aquatic, and is carried on by means of branchial plates or tufts devel- oped upon the posterior visceral arches, which are persistent, and do not disappear at the close of embryonic life, as they do in other Vertebrates. In the Lancelet alone, respiration is effected partly by branchial filaments placed round the com- mencement of the pharynx, and partly by the pharynx itself, which is greatly enlarged, and has its walls perforated by a series of transverse ciliated fissures. The arrangement and structure of the branchiae differs a good deal in the different orders of Fishes, and these modifications will be noticed sub- sequently. In the meanwhile it will be sufficient to give a brief description of the branchial apparatus in one of the bony fishes. In such a fish, the branchiae are connected with the hyoid arch, and are situated in two special chambers, situated one on each side of the neck. The branchiae are carried upon the outer convex sides of what have been already described as the "branchial arches ;" that is to say, upon a series of bony arches which are connected with the hyoid arch inferiorly, and are united above with the base of the skull. The internal concave sides of the branchial arches are usually furnished with a series of processes, constituting a kind of fringe, the function of which is to prevent foreign substances finding their way amongst the branchiae, and thus interfering with the proper action of the respiratory organs. The branchiae, themselves, usually have the form of a double series of cartilaginous leaflets or laminae. The branchial laminae are flat, elongated, and pointed in shape, and they are covered with a highly vascular mucous membrane, in which the branchial capillaries ramify. The blood circulates through the branchial laminae, and is here subjected to the action of aerated water, whereby it is oxygen- ated. The water is constantly taken in at the mouth by a movement analogous to swallowing, and it gains admission to the branchial chambers by means of a series of clefts or slits, the " branchial fissures," which are situated on both sides of the pharynx. Having passed over the gills, the deoxygenated water makes its escape posteriorly by an aperture called the " gill-slit " or " opercular aperture," one of which is situated on each side of the neck. As we have seen before, the gill-slit is closed in front by a chain of flat bones, collectively consti- 350 MANUAL OF ZOOLOGY. tuting the "gill-cover" or " operculum ; " and the gill-covers are finally completed by a variable number of bony spines— the " branchiostegal rays "—which articulate with the hyoid arch, and support a membrane — the " branchiostegal membrane." The heart of Fishes is, properly speaking, a branchial or respiratory heart. It consists of two cavities, an auricle and a ventricle (fig. 131, a, ?;), and the course of the circulation is as follows : — The venous blood de- rived from the liver and from the body generally is poured by the vena cava into the auricle (a), and from this it is propelled into the ventricle (v). From the ventricle arises a single aortic arch (the right), and the base of this is usually dilated into a cavity or sinus, called the "bulbus arteriosus " (m). The arterial bulb is sometimes covered with a special coat of striated muscular fibres, and is provided with several transverse rows of valves. In these cases, the bulbus acts as a kind of continuation of the ventricle, being capable of rhythmical contractions. The blood is driven by the ventricle through the branchial artery (ri) to the gills, through which it is dis- tributed by means of the branchial vessels, the number of which varies (there are three on each side in a few fishes, four in most of the bony fishes, five in the Skates and Sharks, and six or seven in the Lampreys). The aerated blood which has passed through the gills is not returned to the heart, but is driven from the branchiae through all parts of the body; the propulsive force necessary for this being derived chiefly from the heart, assisted by the contractions of the vol- untary muscles. In some fishes (as in the Eel) the return of the blood to the heart is assisted by a rhythmically contractile dilatation of the caudal vein. The essential peculiarity, then, of, the circulation of fishes depends upon this — that the arterial- ised blood returned from the gills is propelled through the sys- temic vessels of the body, without being sent back to the heart. Fig. 131.— Diagram of the cir- culation in a fish, a Auricle, receiving venous blood from the body ; v Ventricle ; in Bulbus arteriosus, at the base of the branchial artery; n Branchial artery, carrying the venous blood to the gills (b b); c Aorta, carrying the arterial- ised blood to all parts of the body. CHARACTERS OF FISHES. 351 The Lancelet (Amphioxus\ alone of all Fishes, has no special heart, and the circulation is effected by contractile dilatations developed upon several of the blood-vessels. In the Mud-fish (Lepidosiren) the heart consists of two auricles and a single ventricle. The blood-corpuscles of Fishes are nucleated (fig. 122, e\ and the blood is red in all except the Amphioxus. As regards the digestive system of Fishes there is not much of peculiar importance. The mouth is usually furnished with a complicated series of teeth, which, in the Bony Fishes, are not only developed upon the jaws proper, but are also situated upon other bones which enter into the composition of the buccal cavity (such as the palate, the pterygoids, vomer, branchial arches, the glossohyal bone, &c.) The oesophagus is usually short and capacious, and generally op ens into a large and well-marked stomach. The pyloric aperture of the stomach is usually furnished with a valve, and behind it there is usually a number (from one to sixty) of blind appendages, termed the " pyloric caeca." These are believed to represent the pancreas, but there may be a recognisable pancreas either alone or in addition to the pyloric caeca. The intestinal canal is a longer or shorter, more or less convoluted tube, the absorbing surface of which, in certain fishes, is largely increased by a spiral reduplicature of the mucous membrane, which winds like a screw in close turns from the pylorus to the anus. The liver is usually large, soft, and oily, and a gall-bladder is almost universally present ; but in the Amphioxus the liver is doubt- fully represented by a hollow sac-like organ. The kidneys of fishes are usually of great size, and form two elongated organs, which are situated beneath the spine, and extend along the whole length of the abdominal cavity. The ureters often dilate, and form a species of bladder, the doubtful representative of the allantois. Whilst the respiration of all fishes is truly aquatic, most of them are, nevertheless, furnished with an organ which is doubtless the homologue of the lungs of the air-breathing Vertebrates. This — the " air " or " swim bladder " — is a sac containing gas, situated beneath the alimentary tube, and often communicating with the gullet by a duct. In the great majority of fishes the functions of the air-bladder are certainly hydrostatic — that is to say, it serves to maintain the necessary accordance between the specific gravity of the fish and that of the surrounding water. In the singular Mud-fishes, however, it acts as a respiratory organ, and is therefore not only the homologue, but also the analogue, of the lungs of the higher 352 MANUAL OF ZOOLOGY. Vertebrates. In most fishes the air-bladder is an elongated sac with a single cavity, but in many cases it is variously sub- divided by septa. In the Mud-fish the air-bladder is composed of two sacs, completely separate from one another, and divided into a number of cellular compartments. The duct leading in many fishes from the air-bladder (ductus pneumaticus) opens into the oesophagus, and is the homologue of the wind-pipe (trachea}. The air contained in the swim-bladder is composed mainly of nitrogen in most fresh-water fishes, but in the sea- fishes it is mainly made up of oxygen. The nervous system of Fishes is of an inferior type of organ- isation, the brain being of small size, and consisting mainly of ganglia devoted to the special senses. As regards the special senses, there is one peculiarity which deserves special notice, and this is the conformation of the nasal sacs. The cavity of the nose is usually double, and is lined by an olfactory mem- brane, folded so as to form numerous plicae. Anteriorly, the water is admitted into the nasal sacs by a single or double nostril, usually by two apertures; but posteriorly the nasal sacs are closed, and do not communicate with the pharynx by any aperture. The only exceptions to this statement are to be found in the Myxinoids and in the Lepidosiren. The essential portion of the organ of hearing (labyrinth} is present in almost all fishes, but in none is there any direct communi- cation between the ear and the external medium. As regards their reproductive system, fishes are, for the most part, truly oviparous, the ovaries being familiarly known as the " roe." The testes of the male are commonly called the " soft roe " or " milt." The products of the reproductive organs are often set free into the peritoneal cavity, ultimately finding their way to the external medium, either by means of an abdominal pore (or pores), or by being taken up by the open mouths of the " Fallopian tubes." In other cases the generative pro- ducts are directly conveyed to the exterior by the proper ducts of the reproductive organs. PHARYNGOBRANCHII. 353 DIVISIONS OF FISHES. CHAPTER LV. PHARYNGOBRANCHII AND MARSIPOBRANCHII. THE class Pisces has been very variously subdivided by dif- ferent writers ; but the classification here adopted is the one proposed by Professor Huxley, who divides the class into the following six orders, in the subdivisions of which Professor Owen has been followed: — ORDER I. PHARYNGOBRANCHII (= Cirrostomi, Owen; and Leptocardia, Miiller). — This order includes but a single fish, the anomalous Amphioxus lanceolatus, or Lancelet, the organ- isation of which differs in almost all important points from that of all the other members of the class. The order is defined by the following characters, which, as will be seen, are mostly negative : — No skull is present, nor lower jaw (mandible), nor limbs. The notochord is persistent ; and there are no verte- bral centra nor arches. No distinct brain nor auditory organs are present. In place of a distinct heart, pulsating dilatations are developed upon several of the great blood-vessels. The blood is pale. The mouth is in the form of a longitudinal fissure, surrounded by filaments or cirri. The walls of the pharynx are perforated by numerous clefts or fissures, the sides of which are ciliated, the whole exercising a respiratory function. The Lancelet is a singular little fish which is found burrow- ing in sandbanks, in various seas, but especially in the Medi- terranean. The body is lanceolate in shape, and is provided with a narrow membranous border, of the nature of a median fin, which runs along the whole of the dorsal and part of the ventral surface, and expands at the tail to form a lancet-shaped caudal fin. No true paired fins, representing the anterior and posterior limbs, are present. The mouth is a longitudinal fissure, situated at the front of the head, and destitute of jaws. It is surrounded by a cartilaginous ring, composed of many pieces, which give off prolongations, so as to form a number of cartilaginous filaments or " cirri " on each side of VOL. n. z 354 MANUAL OF ZOOLOGY. the mouth. (Hence the name of Cirrostomi, proposed by Professor Owen for the order.) The throat is provided on each side with vascular lamellae, which are believed by Owen Fig. 132. — Diagram of the Lancelet (Atnphioxus), m Mouth, surrounded by cartila- ginous cirri; p Greatly dilated pharynx, perforated by ciliated clefts; i Intestine, terminating in anus (a); h Haemal system, with pulsating dilatations ; ch Notochord ; n Spinal cord. to perform the function of free branchial filaments. The mouth leads into a dilated chamber, which is believed to represent the pharynx, and is termed the " pharyngeal " or " branchial sac." It is an elongated chamber, the walls of which are strengthened by numerous cartilaginous filaments, between which is a series of transverse slits or clefts, the whole covered by a richly cili- ated mucous membrane. This branchial dilatation has given rise to the name Branchiostoma, often applied to the Lancelet. Posteriorly the branchial sac opens into an alimentary canal, to which is appended a long and capacious sac or caecum, which is believed to represent the liver. The intestinal tube termi- nates posteriorly by a distinct anus. Respiration is effected by the admission of water taken in by the mouth into the branchial sac, having previously passed over the free branchial filaments before mentioned. The water passes through the slits in the branchial sac, and thus gains access to the abdominal cavity, from which it escapes by means of an aperture with contractile margins situated a little in front of the anus, and called the " abdominal pore." There is no distinct heart, and the circulation is entirely effected by means of several rhythmi- cally contractile dilatations which are developed upon several of the great blood-vessels. The blood itself is colourless. No kidneys have as yet been discovered, and there is no lymphatic system. There is no skeleton properly so called. In place of the vertebral column, and constituting the whole endoskeleton, is the semi-gelatinous cellular notochord, enclosed in a fibrous sheath, and giving off fibrous arches above and below. The notochord is, further, peculiar in this, that it is prolonged quite to the anterior end of the body, whereas in all other Vertebrates MARSIPOBRANCHII. 355 it stops short at the pituitary fossa. There is no cranium, and the spinal cord does not expand anteriorly to form a distinct cerebral mass. The brain, however, may be said to be repre- sented, since the anterior portion of the nervous axis gives off nerves to a pair of rudimentary eyes, and another branch to a ciliated pit, believed to represent an olfactory organ. The generative organs (ovaria and testes) are not furnished with any efferent ducts (oviduct or vas deferens). The generative products, therefore, must be admitted into the abdominal cavity, and gain the external medium by the "abdominal pore." ORDER II. MARSIPOBRANCHII (= Cyclostomi, Owen ; and Cyclostomata, Miiller). — This order includes the Lampreys (Petromyzonidcz) and the Hag -fishes (Myxinidcz), and is de- fined by the following characters : — The body is cylindrical, worm-like, and destitute of limbs. The skull is cartilaginous, without cranial bones, and having no lower jaw (mandible). The notochord is persistent, and there are either no vertebral centra, or but the most rudimentary traces of them. The heart consists of one auricle and one ventricle, but the branchial artery is not furnished with a bulbus arteriosus. The gills are sac-like, and are not ciliated. The type of piscine organisation displayed in the Marsipo- branchii is of a very low grade, as indicated chiefly by the persistent notochord without vertebral centra, the absence of any traces of limbs, the absence of a mandible, and the struc- ture of the gills. Fig. 133. — A, Lamprey (Petromyzon), showing the sucking-mouth and the apertures of the gill-sacs. B, Diagram to illustrate the structure of the gills in the Lamprey : a Pharynx ; b Tube leading from the pharynx into one of the gill-sacs ; c One of i the gill-sacs, showing the lining membrane thrown into folds ; d External opening of the gill-sac. (In reality the gill-sacs do not open directly into the pharynx, but into a common respiratory tube, which is omitted for the sake of clearness.) Both the Lampreys (fig. 133, A) and the Hag-fishes are vermiform, eel-like fishes, which agree in possessing no paired fins, to represent the limbs, but in having a median fin running 356 MANUAL OF ZOOLOGY. round the hinder extremity of the body. The skeleton re- mains throughout life in a cartilaginous condition, the chorda dorsalis is persistent, and the only traces of bodies of vertebrae are found in hardly perceptible rings of osseous matter de- veloped in the sheath of the notochord. The neural arches of the vertebrae, enclosing the spinal cord, are only represented by cartilaginous prolongations. The mouth in the Hag-fish (Myxine) is of a very remarkable character, and enables it to lead a very peculiar mode of life. It is usually found, namely, embedded in the interior of some other larger fish, into which it has succeeded in penetrating by means of its singular dental apparatus. The mouth is sucker-like, destitute of jaws, but provided with tactile filaments or cirri. In the centre of the palate is fixed a single, large, recurved fang, which is firmly attached to the under surface of the cranium. The sides of this fang are strongly serrated, and it is by means of this that the Hag-fish bores its way into its victim, having previ- ously attached itself by its sucker-like mouth. In the Lam- preys the mouth has also the form of a circular cup or sucker, and is also destitute of jaws; but in addition to the palatine fang of the Myxine, the margins of the lips bear a number of horny processes, which are not really true teeth, but are hard structures developed in the labial mucous membrane. The tongue, also, is armed with serrated teeth, and acts as a kind of piston ; so that the Lampreys are in this manner enabled to attach themselves firmly to solid objects. A very remarkable peculiarity in the Hag-fishes, and one very necessary to remember, is found in the structure of the nasal sacs. In all fishes, namely, except these and the Mud- fishes (Lepidosiren\ the nasal sacs are closed behind, and do not open posteriorly into the throat. In the Myxinoids, how- ever, such a communication exists, and the nasal sac — for there is only one — is placed in communication with the cavity of the mouth by means of a canal which perforates the palate. In front the nasal cavity communicates with the external me- dium by a second tube, which opens on the top of the head by a single aperture, which is often called the " spiracle," and which is in reality an unpaired nostril. In the Lampreys, on the other hand, the single nasal sac has the same structure as in the typical fishes — that is to say, it is closed behind, and does not communicate in any way with the cavity of the mouth. Another very remarkable point in the Hag-fishes and Lam- preys is to be found in the structure of the gills, from which the name of the order is derived. In the Lampreys, in place TELEOSTEI. 357 of the single gill-slit, covered by a gill-cover, as seen in the ordinary bony fishes, the side of the neck, when viewed ex- ternally, exhibits six or seven round holes placed far back in a line on each side (fig. 133, A). In the Hag-fishes the external apertures of the gills are reduced to one on each side, placed below the head ; but the internal structure of the gills is the same in both cases. In both the Lampreys and the Hag-fishes, namely, the gills are in the form of sacs or pouches (fig. 133,6), the mucous membrane of which is thrown into folds or plaits like the leaves of a book, over which the branchial vessels ramify. Internally the sacs communicate with the cavity of the pharynx, either directly or by the intervention of a common respiratory tube. It follows from this, that the gill-pouches on the two sides, with their included fixed branchial laminae, com- municate freely with one another through the pharynx. The object of this arrangement appears to be mainly that of ob- viating the necessity of admitting water to the gills through the mouth, as is the case with the ordinary bony fishes. These fishes are in the habit of fixing themselves to foreign objects by means of the suctorial mouth ; and when in this position it is, of course, impossible that they can obtain the necessary water of respiration through the mouth. As the branchial pouches, however, on the two sides of the neck communicate freely with one another through the pharynx, water can readily pass in and out. This, in the Lampreys, is further assisted by a kind of elastic cartilaginous framework upon which the respiratory apparatus is supported, and which acts somewhat like the ribs of the higher Vertebrata. Water can also be admitted to the pharynx, and thence to the branchial sacs, by means of a tube which leads from the pharynx to an aperture placed on the top of the head. The Lampreys are, some of them, inhabitants of rivers ; but the great Sea-lamprey (Petromyzon marinus] only quits the salt water in order to spawn. The Hag-fish ( Myxine glutinosa) is an inhabitant of the North Sea, and is commonly captured on the Norwegian coast. CHAPTER LVI. TELEOSTEI. ORDER III. TELEOSTEI. — This order includes the great ma- jority of fishes in which there is a well-ossified endoskeleton, MANUAL OF ZOOLOGY. and it corresponds very nearly with Cuvier's division of the " osseous" fishes. The Teleostei are denned as follows : — The skeleton is usually well ossified ; the cranium is provided with cranial bones ; and a mandible is present ; whilst the vertebral column almost always consists of more or less completely ossi- fied vertebrae. The pectoral arch has a clavicle ; and the two pairs of limbs, when present, are in the form of fins supported by rays. The gills are free, pectinated or tufted in shape ; a bony gill-cover and branchiostegal rays being always devel- oped. The branchial artery has its base developed into a bul- bus arteriosus ; but this is never rhythmically contractile, and is separated from the ventricle by no more than a single row of valves. The order Teleostei comprises almost all the common fishes ; and it will be unnecessary to dilate upon their structure, as they were taken as the types of the class in giving a general description of the Fishes. It may be as well, however, to recapitulate very briefly some of the leading characters of the order. I. The skeleton, instead of remaining throughout life more or less completely cartilaginous, is now always more or less thoroughly ossified. The notochord is not persistent, and the vertebral column, though sometimes cartilaginous, consists of a number of vertebrae. The bodies of the vertebras are what is called "amphicoelous" — that is to say, they are concave at both ends. It follows from this, that between each pair of vertebrae there is formed a doubly-conical cavity, and this is filled with the cartilaginous or semi-gelatinous remains of the notochord. By this means an extraordinary amount of flexi- bility is given to the entire vertebral column. In no fish except the Bony Pike (which belongs to the order Ganoidei) is the ossification of the vertebral centra carried further than this. The skull is of an extremely complicated nature, being com- posed of a number of distinct cranial bones ; and a mandible or lower jaw is invariably present. II. The anterior and posterior pairs of limbs are usually, but not always, present, and when developed they are always in the form of fins. The fins may be supported by "spinous" or " soft" rays, of which the former are simple undivided spines of bone, whilst the latter are divided transversely into a num- ber of short transverse pieces, and also are broken up into a number of longitudinal rays proceeding from a common root. (The Fishes with soft rays in their paired fins are termed " Malacopterygii" — those with spinous rays, " Acanthopterygtif) III. Besides the paired fins, representing the limbs, there is TELEOSTEI. 359 a variable number of unpaired or azygous integumentary ex- pansions, which are known as the " median fins." When fully developed (fig. 129), they consist of one or two fins on the back — the " dorsal " fins ; one or two on the ventral surface — the " anal " fins ; and one clothing the posterior extremity of the body — the " caudal" fin. The caudal fin is set vertically, and not horizontally, as in the Whales and Dolphins; and in all the bony fishes its form is " homocercal" — that is, it consists of two equal lobes, and the vertebral column is not prolonged into the superior lobe. In all the median fins the fin-rays are supported upon a series of dagger-shaped bones, which are plunged in the flesh of the middle line of the body, and are attached to the spinous processes of the vertebrae. These are the so-called "interspinous" bones. IV. The heart consists of two chambers — an auricle and a ventricle, and the branchial artery is furnished with a bulbus arteriosus. The arterial bulb, however, is not furnished with a special coat of striated muscular fibres, is not rhythmically con- tractile, and is separated from the ventricle by no more than a single row of valves (fig. 134, A). Fig. 134. — A, Heart of the Angler (Lophius piscatorius). B, Arterial bulb of Bony Pike (Lepidosteus) cut open. C, Heart of the same, viewed externally : a Auricle ; •v Ventricle ; b Arterial bulb. V. The respiratory organs consist of free, pectinated, or tufted branchiae, situated in two branchial chambers, each of which communicates internally with the pharynx by a series of clefts, and opens externally on the side of the neck by a single aper- ture (or "gill-slit"), which is protected in front by a bony gill- cover, and is also closed by a " branchiostegal membrane," sup- ported upon "branchiostegal rays." The branchiae are attached to a series of bony branchial arches, which are connected in- feriorly with the hyoid bone and superiorly with the skull ; and 360 MANUAL OF ZOOLOGY. the water required in respiration is taken in at the mouth by a process analogous to swallowing. VI. The nasal sacs never communicate posteriorly with the cavity of the pharynx. The subdivisions of the osseous fishes are so numerous, and they contain so many families, that it will be sufficient to run over the more important sub-orders, and to mention the more familiar examples of each. SUB-ORDER A. MALACOPTERI, Owen (= Physostomata, Miil- ler). — This sub-order is defined by usually possessing a com- plete set of fins, supported by rays, all of which are " soft" or many-jointed, with the occasional exception of the first rays in the dorsal and pectoral fins. A swim-bladder is always present, and always communicates with the oesophagus by means of a duct, which is the homologue of the windpipe. The skin is rarely naked, and is mostly furnished with cycloid scales ; but in some cases ganoid plates are present. This sub-order is one of great importance, as comprising many well-known and useful fishes. It is divided into two groups, according as ventral fins are present or not. In the first group — Apoda — there are no ventral fins ; and the most familiar examples are the common Eels of our own country. More remarkable, however, than the ordinary Eels is the Gymnotus elcctricus, or great Electric Eel, which inhabits the marshy waters of those wonderful South American plains, the so-called " Llanos." This extraordinary fish (fig. 135) is from Fig. 135. — Electric Eel (Gymnotus electricus). five to six feet in length, and the discharge of its electrical organs is sufficiently powerful to kill even large animals. The following striking account is given by Humboldt of the manner in which the Gymnoti are captured by the Indians : — " A number of horses and mules are driven into a swamp which is closely surrounded by Indians, until the unusual disturbance excites the daring fish to venture an attack. Serpent-like, TELEOSTEI. 361 they are seen swimming along the surface of the water, striving cunningly to glide under the bellies of the horses. By the force of their invisible blows numbers of the poor animals are suddenly prostrated ; others, snorting and panting, their manes erect, their eyes wildly flashing terror, rush madly from the raging storm ; but the Indians, armed with long bamboo staves, drive them back into the midst of the pool. " By degrees the fury of this unequal contest begins to slacken. Like clouds which have discharged their electricity, the wearied eels disperse. They require long rest and nourish- ing food, to repair the galvanic force which they have so lavishly expended. Their shocks gradually become weaker and weaker. Terrified by the noise of the trampling horses, they timidly approach the banks of the morass, where they are wounded by harpoons, and drawn on shore by non-conducting pieces of dry wood. " Such is the remarkable contest between horses and fish. That which constitutes the invisible but living weapon of these inhabitants of the waters — that which, awakened by the con- tact of moist and dissimilar particles, circulates through all the organs of animals and plants — that which, flashing amid the roar of thunder, illuminates the wide canopy of heaven — which binds iron to iron, and directs the silent recurring course of the magnetic needle — all, like the refracted rays of light, flow from one common source, and all blend together into one eternal all-pervading power." The second group of the Malacopteri is that of the Abdomi- nalia, in which there are ventral fins, and these are abdominal in position. Space will not permit of more here than merely mentioning that in this section are contained amongst others the well-known and important groups of the Clupeidce (Herring tribe), the Pikes (Esotida), the Carps (Cyprinidce), the" Sternop- tixince, and the Salmonidce, comprising the various species of Salmon and Trout. Also belonging to this group are the Sheat-fishes (Siluridce), which are chiefly noticeable because they are amongst the small number of living fishes possessed of structures of the same nature as the fossil spines known as " ichthyodorulites." The structure in question consists of the first ray of the pectoral fins, which is largely developed and constitutes a formidable spine, which the animal can erect and depress at pleasure. Unlike the old "ichthyodorulites," how- ever, the spines of the Siluridcz have their bases modified for articulation with another bone, and they are not simply hollow and implanted in the flesh. The " Siluroids " are also remark- able for their resemblance to certain of the extinct Ganoid 362 MANUAL OF ZOOLOGY. fishes (e. g., Pterichthys, Coccostens, &c.), caused by the fact that the head is protected with an exoskeleton of dermal bones. SUB -ORDER B. ANACANTHINI. — This sub.- order is distin- guished by the fact that the fins are entirely supported by " soft " rays, and never possess " spiny" rays ; whilst the ven- tral fins are either wanting, or, if present, are placed under the throat, beneath or in advance of the pectorals, and supported by the pectoral arch. The swim-bladder may be wanting, but when present it does not communicate with the oesophagus by a duct. As in the preceding order, the Anacanthini are divided into two groups, distinguished by the presence or absence of the ventral fins. In the first of these groups (Apoda) are only a few fishes, of which one of the most familiar examples is the little Sand-eel (Ammodytes lancea\ which occurs on all our coasts. In the second group (Sub-brachiata) in which ventral fins exist, are the two important families of the Gadidce and Pleuronectidce. The Gadidcs. or Cod family, comprising the Haddock, Whiting, Ling, and Cod itself, is of great value to man, most of its members being largely consumed as food. In the Pleuronectida or Flat-fishes are comprised the Sole, Plaice, Turbot, Halibut, Brill and others, in all of which there is a very curious modification in the form of the body. The body, namely, in all the Flat-fishes (fig. 136) is very much compressed Fig. 136. — Pleuronectidse. Rhombus punctatus. Natural size (after Gosse). from side to side, and is bordered by long dorsal and anal fins. The bones of the head are twisted in such a manner that the two eyes are both brought to one side of the body. The fish usually keeps this side uppermost and is dark-coloured on this aspect, whilst the opposite side, on which it rests, is white. From this habit of the Flat-fishes of resting upon one flat sur- TELEOSTEI. 363 face, the sides are often looked upon as the dorsal and ventral surfaces of the body. This, however, is erroneous, as they are shown by the position of the paired fins to be truly the lateral surfaces of the body. SUB-ORDER C. ACANTHOPTERI. — This sub-order is charac- terised by the fact that one or more of the first rays in the fins are in the form of true, unjointed, inflexible, "spiny" rays. The exoskeleton consists, as a rule, of ctenoid scales. The ventral fins are generally beneath or in advance of the pectorals, and the duct of the swim-bladder is invariably obliterated. This sub-order comprises two families : — a. The Pharyngognathi, in which the inferior pharyngeal bones are anchylosed so as to form a single bone, which is usually armed with teeth. The family is not of much import- ance, the only familiar fishes belonging to it being the " Wrasses " ( Cydolabridce). b. The Acanthopteri vert, characterised by having always spiny rays in the first dorsal fin, and usually in the first rays of the other fins, whilst the inferior pharyngeal bones are never anchylosed into a single mass. This family includes many subordinate groups, and may be regarded as, on the whole, the most typical division of the Teleostean Fishes. It will not be necessary, however, to do more than mention as amongst the more important fishes contained in it, the Perch family (Percidce), the Mullets (Mugilidce), the Mackerel family (Scom- beridISTRIBUTION OF AMPHIBIA IN TIME. — From a geological point of view by far the most important of the Amphibia are the Labyrinthodontia, the distribution of which has just been spoken of. The living orders of Amphibia are of much more modern date, being, as far as known, wholly Tertiary and Post-tertiary. The Anoura are represented by both Toads and Frogs in Miocene times, and they have survived to the present day. The " Tailed " Amphibians are best known to geologists by a singular fossil, which was described by its ori- ginal discoverer as human, under the name of Homo diluvit testis. The fossil in question is of Miocene age, and it is now known to belong to a Salamander, nearly allied to the giant- salamander of Java (Menopoma\ It is termed the Andrias Sheuchzeri. CHARACTERS OF REPTILIA. 393 DIVISION II. SAUROPSIDA. CHAPTER LXII. CLASS III.— REPTILIA. THE second great division of the Vertebrate Sub-kingdom, according to Huxley, is that of the Sauropsida, comprising the true Reptiles and the Birds. It is, no doubt, at first sight an almost incredible thing that there should be any near bond of relationship between the Birds and the Reptiles, no two classes of animals being more unlike one another in habits and ex- ternal appearance. It is, nevertheless, the fact that the Birds are more nearly related to the Reptiles than to any other class of the Vertebrata, and it will shortly be seen that many affini- ties and even transitional forms are known to exist between these great sections. The Reptiles and Birds, then, may be naturally included in a single primary section of Vertebrates, which may be called Sauropsida after Huxley, and which is defined by the possession of the following characters : — At no period of existence are branchiae, or water-breathing respiratory organs, developed upon the visceral arches; the embryo is furnished with a well-developed amnion and allantois ; the red corpuscles of the blood are nucleated (fig. 122, £, c); the skull articulates with the vertebral column by means of a single articulating surface or condyle ; and each half or " ramus " of the lower jaw is composed of several pieces, and articulates with the skull, not directly, but by the intervention of a pecu- liar bone, called the " quadrate bone," or " os quadratum " (fig. 153). These being the common characters of Reptiles and Birds by which they are collectively distinguished from other Verte- brates, it remains to inquire what are the characters by which they are distinguished from one another. The following, then, are the characters which separate the Reptiles from the Birds : — The blood in Reptiles is cold — that is to say, slightly warmer than the external medium— owing mainly to the fact that the pulmonary and systemic circulations are always directly con- 394 - MANUAL OF ZOOLOGY. nected together, either within the heart or in its immediate neighbourhood, so that the body is supplied with a mixture of venous and arterial blood, in place of pure arterial blood alone. The terminations of the bronchi at the surface of the lung are closed, and do not communicate with air-sacs, placed in dif- ferent parts of the body. When the epidermis develops horny structures, these are in the form of horny plates or scales, and never in the form of feathers. The fore-limbs are formed for various purposes, including in some cases even flight, but they are never constructed upon the type of the " wings " of Birds. Lastly, with one or two doubtful exceptions, whilst the ankle- joint is placed between the distal and proximal portions of the tarsus, the tarsal and metatarsal bones of the hind-limb are never anchylosed into a single bone. These are the leading characters by which Reptiles are dis- tinguished from Birds, but we must not forget the other dis- tinctive peculiarities in which Reptiles agree with Birds, and differ from other Vertebrates — namely, the presence of an amnion and allantois in the embryo, the absence of branchiae at all times of life, the possession of only one occipital condyle, and the articulation of the complex lower jaw with the skull by means of a quadrate bone. It is now necessary to consider these characteristics of the Reptilia a little more minutely. The class includes the Tor- toises and Turtles, the Snakes, the Lizards, the Crocodiles, and a number of extinct forms ; and with the exception of the Tor- toises and Turtles they are mostly of an elongated cylindrical shape, provided posteriorly with a long tail. The limbs may be altogether absent, as in the Snakes, or quite rudimentary, as in some of the Lizards, but as a general rule both pairs of limbs are present, sometimes in the form of ambulatory legs, sometimes as swimming-paddles, and in some extinct forms modified to subserve an aerial life. The endoskeleton is always well ossified, and is never cartilaginous or semi-cartila- ginous, as in many fishes and some Amphibians. The skull articulates with the atlas by a single condyle. The lower jaw is complex, each half or ramus being composed of from four to six pieces, united to one another by sutures (fig. 153). In the Tortoises, however, these are anchylosed into a single piece, and the two rami are also anchylosed. In most Reptiles, how- ever, the two rami of the lower jaw are only loosely united — in the Snakes by ligaments and muscles only, in the Lizards by fibro-cartilage, and in the Crocodilia by a regular suture. In all, the lower jaw articulates with the skull by a quadrate bone (fig. 153, a)-} and as this often projects backwards, the CHARACTERS OF REPTILIA. 395 opening of the mouth is often very extensive, and may even extend beyond the base of the skull. Teeth are usually pre- sent, but are not sunk in separate sockets or alveoli, except in Fig. 153. — Skull of a Serpent (Python), b Articular portion of the lower jaw ; a Quadrate bone J c Squamosal portion of the temporal bone. the Crocodiles. In the Tortoises and Turtles alone there are no teeth, and the jaws are simply sheathed in horn, constituting a kind of beak like that of a bird. Ribs are always present and always well developed, but they differ much in form. It is not correct, however, to regard the presence of ribs as separating the true Reptiles from the Am- phibia, as is sometimes stated. Some of the most Lizard-like of the Amphibians, such as the Siren, possess short but well- developed ribs, and rudiments of ribs are traceable in other orders ; whilst in the C&cilice. they are large and well de- veloped. As regards the exoskeleton, all Reptiles have horny epider- mic scales, and they are divided into two great sections — called respectively Squamata and Loricata — according as the integu- mentary skeleton consists simply of these scales, or there are osseous plates developed in the derma as well. In the Tor- toises, the epidermic plates unite with the bony exoskeleton and with the true endoskeleton to form the case or box in which the body of these animals is enclosed. The digestive system of the Reptilia possesses few characters of any special importance, except that the rectum opens, as in Amphibia, into a common cavity or " cloaca," which not only receives the faeces, but also serves for the discharge of the products of the urinary and generative organs. The heart in the Reptiles consists of two completely separate auricles, and a ventricular cavity, which is divided into two by an .incomplete partition. In \hzCrocodilia alone is the septum p ... 396 MANUAL OF ZOOLOGY. between the ventricles a perfect one, and even in these, as in all other Reptiles, the heart consists functionally of no more than three chambers. The ordinary course of the circulation, where the ventricular septum is imperfect, is as follows : — The impure venous blood returned from the body is, of course, poured by the venae cavse into the right auricle (fig. 154, a), and thence into the ventricle. The pure arterialised and aerated blood that has passed through the lungs, is equally, of course, poured into the left auricle (#'), and thence propelled into the ventricle (v). As the ventricular cavity is single, and not divided by a complete partition, it fol- lows of necessity that there is a mixture in the ventricle, resulting in the production of a mixed fluid, consisting partly of venous and partly of arterial blood. This mixed fluid, then, occupies the common ventricular cavity, and by this it is driven both to the lungs (through the pulmonary artery), and to the body (through the systemic aorta). Conse- in Reptiles, both the and the various tissues and m of the circulation in Fig. 154.— Diagra Reptiles. (The the arterial system is black, and Reptiles. (The venous system is left light, the vessels containing mixed blood are r ,1 •• j T j 1 cross-shaded.) a Right auricle, receiv- organs of the body are supplied ing venous blood from the body ; of with a mixture of arterial and Left auricle, receiving arterial blood - from the lungs ; v Arterio-venous ven- VCnOUS blood, and not With Un- tricle, containing mixed blood, which is rm'VArl Klnr»rl \\\p- Inncrc with driven by (/) the pulmonary artery to miXe<1 DlOOQ- -tHC lUngS W1U1 the lungs, and by (o] the aorta to the purely venous, and the body with purely arterial blood — as is the case with the higher Vertebrata. In the Crocodilia, as before said, the partition between the ventricles is a complete one, and consequently this mixture of the arterial and venous blood cannot take place within the heart itself. In these Reptiles, however, a direct communication exists between the pulmonary artery and aorta (the right and left aortas) by the so-called " foramen Panizzae," close to the point where these vessels spring respectively from the right and left ventricle. In these Reptiles, therefore, the same mixture of arterial blood with DIVISIONS OF REPTILES. 397 * venous takes place as in the lower Reptilia, though probably not to so complete an extent. It is this peculiarity of the circulation in all Reptiles which conditions their low tempera- ture, slow respiration, and generally sluggish vital actions. The lungs in all Reptiles, except the Crocodiles, are less completely cellular than in the Birds and Mammals, and they often attain a very great size. In no Reptile is the cavity of the thorax shut off from that of the abdomen by a complete muscular partition or "diaphragm;" though traces of this structure are found in the Crocodiles. The lungs, therefore, often extend along the whole length of the thoracico-abdominal cavity. In no case are the lungs connected with air-receptacles situated in different parts of the body; and not uncommonly there is only a single active lung, the other being rudimentary or completely atrophied (Ophidia). Lastly, all Reptiles are essentially oviparous, but in some cases the eggs are retained within the body till the young are ready to be excluded, and the animals are then ovo-viviparous. The egg-shell is usually parchment-like, but sometimes contains more or less calcareous matter. CHAPTER LXIII. DIVISIONS OF REPTILES. CHELONIA AND OPHIDIA. THE class Reptilia is divided into the following nine orders, of which the first four are represented by living forms, whilst the remaining five are extinct : — 1. Chelonia (Tortoises and Turtles). 2. Ophidia (Snakes). I Recent 3. Lacertilia (Lizards). 4. Crocodilia (Crocodiles and Alligators). J 5. Ichthyopterygia. 1 6. Sauropterygia. 7. Anomodontia. \ Extinct. 8. Pterosauria. 9. Deinosauria. J ORDER I. CHELONIA. — The first order of living Reptiles is that of the Chelonia, comprising the Tortoises and Turtles, and 398 -MANUAL OF ZOOLOGY. distinguished by the following characters : — There is an osseous exoskeleton which is combined with the endoskeleton to form a kind of bony case or box in which the body of the animal is enclosed, and which is covered by a leathery skin, or, more usually, by horny epidermic plates. The dorsal vertebrae are immovably connected together, and are devoid of transverse processes. The ribs are greatly expanded (fig. 155, r), and are united to one another by sutures, so that the walls of the thoracic cavity are immovable. All the bones of the skull except the lower jaw and the hyoid bone are immovably united together. There are no teeth, and the jaws are encased in horn so as to form a kind of beak. The heart is three-chambered, the ventricular septum being imperfect. There is a large uri- nary'bladder, and the anal aperture is longitudinal or circular. Of these characters of the Chelonia, the most important and distinctive are the nature of the jaws, and the structure of the exoskeleton and skeleton. As regards the first of these points, the lower jaw in the adult appears to consist of a single piece, its complex character being masked by anchylosis. The sepa- rate pieces which really compose each ramus of the jaw are immovably anchylosed together, and the two rami are also united in front by a true bony union. There are also no teeth, and the edges of the jaws are simply sheathed in horn, constituting a sharp beak. As regards the second of these points, the bony case in which the body of a Chelonian is enclosed consists essentially of two pieces, a superior or dorsal piece, generally convex, called the "carapace," and an in- ferior or ventral piece, generally flat or concave, called the "plastron." The carapace and plastron are firmly united along their edges, but are so excavated in front and behind as to leave apertures for the head, tail, and fore and hind limbs. The limbs and tail can almost always be withdrawn at will under the shelter of the thoracico-abdominal case formed in this way by the carapace and plastron, and the head is also generally retractile. The carapace or dorsal shield is composed of the following elements : — i. The spinous processes of the dorsal vertebra, which are much flattened out laterally and form a series of broad plates. 2. The ribs, which are also much flattened and expanded, and constitute what are known as the " costal plates" (fig. 155, r). They are generally eight in number on each side, and are commonly united throughout the whole of their lateral margins by sutures. In some cases, however, they leave marginal apertures towards their extremities, and these openings are DIVISIONS OF REPTILES. 399 simply covered by a leathery skin or by horny plates. 3. The margin of the carapace is completed by a series of bony plates, which are called the " marginal plates." These are variously Fig. 155.— Skeleton of Tortoise (Emys Europea), the plastron being removed, ca Carapace ; r Ribs, greatly expanded, and united by'their edges ; s Scapular arch, placed within the carapace, and carrying the fore-limbs ; p Pelvic arch, also placed within the carapace, and carrying the hind-limbs. regarded as being dermal bones belonging to the exoskeleton, or as being endoskeletal, and as representing the ossified cartilages of the ribs (in this last case the marginal plates would correspond with what are known as the " sternal ribs " of Birds). The " plastron " or ventral shield is composed of a number of bony plates (nine in number), the nature of which is doubt- ful. By Professor Owen, the plastron is still regarded as a greatly-developed breast-bone or sternum. By Huxley and Rolleston, on the other hand, the Chelonia are regarded as being wholly without a sternum, and the bones of the plastron are looked upon as exclusively integumentary ossifications. Both the carapace and the plastron are covered by a leathery skin, or more generally by a series of horny plates (fig. 156), 4OO MANUAL OF ZOOLOGY. which roughly correspond with the bony plates below, and which constitute in some species the " tortoise-shell " of com- merce. These epidermic plates, however, must on no account be confounded with the true bony box in which the animal is enclosed, and which is produced partly by the true endo- skeleton, and partly by dermal integumentary ossifications. The other points of importance as regards the endoskeleton are these : — Firstly, The dorsal vertebrae are immovably joined together, and have no transverse processes, the heads of the ribs uniting directly with the bodies of the vertebrae. Secondly, The scapular and pelvic arches, supporting the fore and hind limbs respectively (fig. 155, s and/), are placed within the carapace, so that the scapular arch is thus inside the ribs, instead of being outside, as it normally is. The scapular arch consists of the shoulder-blade or scapula, and two other bones, of which one corresponds with the acromion process of human anatomy, and the other to the coracoid process, or to the " coracoid bone " of the Birds. The clavicles, as is also the case with the Crocodilia, are absent. The order Chelonia is conveniently divided into three sec- Fig. 156.— Hawk's-bill Turtle (CJuIonia. imbricata}-^^ BelL tions, according as the limbs are natatory, amphibious, or ter- restrial. In the first of these, the limbs are converted into most efficient swimming-paddles, all the toes being united by a common covering of integument. In this section are the well- CHELONIA. 401 known Turtles (Cheloniidce), all of which swim with great ease and power, but are comparatively helpless upon the land (fig. 156). The best-known species are the "edible" or Green Turtle (Chelonia mydas), the Loggerhead Turtle (Chelonia caou- anna), the Hawk's-bill Turtle (C. imbricata), and the Leathery Turtle (Sphargis coriacea). The Green Turtle is largely im- ported into this country as a delicacy, and occurs abundantly in various parts of the Atlantic and Indian Oceans. The Hawk's-bill Turtle is of even greater commercial importance, as the horny epidermic plates of the carapace constitute the " tortoise-shell" so largely used for ornamental purposes. The Leathery Turtle is remarkable in having the carapace covered with a leathery skin in place of the horny plates which are found in other species. In the second section of the Chelonia, in which the limbs are adapted for an amphibious life, are the Mud-turtles or Soft Tortoises (Trionycida), and the Terrapenes (Emydida). In the Trionycidcz the development of the carapace is imperfect, the ribs being expanded and united to one another only near their bases, and leaving apertures near their extremities. The entire carapace is covered by a smooth leathery skin, and the horny jaws are furnished with fleshy lips. All the Trionytida inhabit fresh water and are carnivorous in their habits. One of the largest and best known is the so-called Snapping Turtle (Trionyx ferox) of North America, but other species are found in Egypt and in the East Indies. The Terrapenes (Emys) have a horny beak, and have the shield covered with epider- mic plates. They are inhabitants of fresh water, and are most of them natives of America. The third section of the Chelonia comprises only the Land Tortoises (Testudinidce), in which the limbs are adapted for ter- restrial progression, and the feet are furnished with short nails. The carapace is strongly convex, and is covered by horny epi- dermic plates ; the head, limbs, and tail can be completely re- tracted within the carapace. Though capable of swimming, the Tortoises are really terrestrial animals, and are strictly vegetable-feeders. The most familiar species is the Testudo Graca, which is indigenous in Spain, Italy, and Greece, but is commonly kept in this country as a domestic pet. DISTRIBUTION OF CHELONIA IN TIME. — The earliest known traces of Chelonians occur in the Permian Rocks, in the lower portion, that is, of the New Red Sandstone of older geologists. These traces, however, are not wholly satisfactory, since they con- sist solely of the footprints of the animal upon the ripple-marked surfaces of the sandstone. Of this nature is the Chelichnus VOL, II. 2 C 4O2 MANUAL OF ZOOLOGY. Duncani, described by Sir William Jardine in his classical work on the "Ichnology" of Annandale in Dumfriesshire. The ear- liest unequivocal remains of Chelonians are in the Oolitic Rocks (the Chelonia planiceps of the Portland Stone). Fossil CheloniidcR, Emydida, and Trimycufa occur, also, from the Upper Oolites to the present day, the Eocene period being peculiarly rich in their remains. In the Tertiary deposits of India (Sivalik Hills) there occurs a gigantic fossil Tortoise — the Colossochelys Atlas — which is believed to have been eighteen to twenty feet in length, and to have possibly survived to within the human period. ORDER II. OPHIDIA. — The second order of Reptiles is that of the Ophidia, comprising the Snakes and Serpents, and distinguished by the following characters : — The body is always more or less elongated, cylindrical, and worm-like, and whilst possessing a covering of horny scales, is always unprovided with a bony exoskeleton. The dorsal ver- tebrae are concave in front (procoelous), with rudimentary trans- verse processes. There is never any sternum, nor pectoral arch, nor fore-limbs, nor sacrum, and as a rule there are no traces of hind-limbs. Rudimentary hind-limbs, however, are occasionally present (e.g., in Python and Tortrix). There are always numerous ribs. The two halves or rami of the lower jaw are composed of several pieces, and the rami are united anteriorly by ligaments and muscles only, and not by cartilage or suture. The lower jaw further articulates with the skull by means of a quadrate bone (fig. 153, a), which is always more or less movable, and is in turn united with the squamous por- tion of the temporal bone, which is also movable, and is not firmly united with the skull. Hooked conical teeth are always present, but they are never lodged in distinct sockets or alveoli. Functionally, they are capable of performing nothing more than merely holding the prey fast, and the Snakes are provided with no genuine masticatory apparatus. The heart has three chambers, two auricles and a ventricle, the latter imperfectly divided into two cavities by an incomplete septum. The lungs and other paired organs are mostly not bilaterally symmetrical, one of each pair being either rudimentary or absent. There is no urinary bladder, and the cloacal aperture is transverse. Of these characters of the Snakes, the most obvious and striking are to be found in the nature of the organs of locomo- tion. The front limbs, with the scapular arch and sternum, are invariably altogether absent; and the hind-limbs, if not wholly wanting, are never represented by more than a pair of rudimentary pelvic bones concealed within the muscles on each OPHIDIA. 403 side of the anal aperture, and never exhibiting any outward evidence of their existence beyond the occasional presence of short horny claws or spurs ("calcaria"). In the entire absence, then, or rudimentary condition of the limbs, the Snakes progress by means of the ribs. These bones are always extremely nu- merous (sometimes amounting to more than three hundred pairs), and in the absence of a sternum they are, of course, ex- tremely movable. Their free extremities, in fact, are simply terminated by tapering cartilages, which are attached by mus- cular connections to the abdominal scales or " scuta " of the integument. By means of this arrangement the Serpents are enabled to progress rapidly, walking, so to speak, upon the ends of their ribs : their movements being much facilitated by the extreme mobility of the whole vertebral column, conditioned by the cup-and-ball articulation of the bodies of the vertebras with one another. The body in the Snakes is covered with numerous scales, developed apparently in the lower layer of the epidermis, and covered by a thin, translucent, superficial pellicle, which is peri- odically cast off and renewed. On the head and along the abdomen these scales are larger than over the rest of the body, and they constitute what are known as the " scuta " or shields. The only other points in the anatomy of the Ophidia which demand special attention are the structure of the tongue, teeth, and eye. The tongue in the Snakes is probably an organ more of Fig. 157.— A, Diagram of the eye of a Serpent (after Cloquet) : a Ball of the eye covered by a conjunctival sac, into which the lachrymal secretion is discharged ; b Optic nerve ; d Antocular membrane, formed by the epidermis ; e e Ring of scales surrounding the eye. B, Head of the common Viper (Pelias berus)— alter Bell- showing the bifid tongue, and the poison-fangs in the upper jaw. touch than of taste. It consists of two muscular cylinders, united towards their bases, but free towards their extremities. The bifid organ, thus constituted, can be protruded and 404 MANUAL OF ZOOLOGY. retracted at will, being in constant vibration when protruded, and being in great part concealed by a sheath when retracted. As regards the eye of Serpents (fig. 157, A), the chief peculiarity lies in the manner in which it is protected exter- nally. There are no eyelids, and hence the stony unwinking stare of all snakes. In place of eyelids, the eye is surrounded by a circle of scales (e e\ to the circumference of which is attached a layer of transparent epidermis, which covers the whole eye ($.—Pterodactyhis brevirostris. Skeleton and restoration. armed with teeth, and these were implanted in distinct sockets. In some forms (Ramphorhynchus) there appear to have been no teeth in the anterior portion of the jaws, and these parts 420 MANUAL OF ZOOLOGY. seem to have been sheathed in horn, so as to constitute a kind of beak. A ring of bony plates occurs in the sclerotic coat of the eye. The pectoral arch consists of a scapula and distinct coracoid bone, articulating with the sternum as in Birds, but no clavicles have hitherto been discovered. The fore-limb (fig. 165) consists of a humerus, ulna and radius, carpus, and hand of four fingers, of which the inner three are short and unguiculate, whilst the outermost is clawless and is enormously elongated. Between this immensely -lengthened finger, the side of the body, and the comparatively small hind-limb, there must have been supported an expanded flying-membrane or " patagium," which the animal must have been able to employ as a wing, much as the Bats of the present day. Lastly, most of the bones were " pneumatic " — that is to say, were hollow and filled with air. By the presence of teeth in distinct sockets, and, as will be seen hereafter, especially in the structure of the limbs, the Pterodactyles differed from all known Birds, and there can be little question as to their being genuine Reptiles. The only Reptile, however, now existing, which possesses any power of sustaining itself in the air, is the little Draco volans, but this can only take extended leaps from tree to tree, and cannot be said to have any power of flight properly so called. That the Pterodactyles, on the other hand, possessed the power of genuine flight is shown by the presence of a median keel upon the sternum, proving the existence of unusually-developed pectoral muscles; by the articulation of the coracoid bones with the top of the sternum, providing a fixed point or fulcrum for the action of the pectoral muscles ; and, lastly, by the exist- ence of air-cavities in the bones, giving the animal the neces- sary degree of lightness. The apparatus, however, of flight was not a " wing," as in Birds, but a flying-membrane, very similar in its mode of action to the patagium of the Mammalian order of the Bats. The patagium of the Bats, however, differs from that of the Pterodactyles in being supported by the greatly- elongated fingers, whereas in the latter it is only the outermost finger which is thus lengthened out. The Pterosauria are exclusively Mesozoic, being found from the Lower Lias to the Middle Chalk inclusive, the Lithographic Slate of Solenhofen (Upper Oolite) being particularly rich in their remains. Most of them appear to have attained no very great size, but the remains of a species from the Cretaceous Rocks have been considered to indicate an animal with more than twenty feet expanse of wing, counting from tip to tip. In the genus Pterodactylus proper, the jaws are provided EXTINCT ORDERS OF REPTILES. 421 with teeth to their extremities, all the teeth being long and slender. In Dimorphodon, the anterior teeth are large and pointed, the posterior teeth small and lancet-shaped. In Ramphorhynchus, the anterior portion of both jaws is edentulous, and may have formed a horny beak, but teeth are present in the hinder portion of the jaws. ORDER IX. DINOSAURIA. — The last order of extinct Reptiles is that of the Dinosauria, comprising a group of very remarkable Reptiles, which show many points of decided affinity to the Birds on the one hand, and to the so-called Pachydermatous Mammals on the other. Most of the Dinosauria were of gigantic size, and the order is denned by the following characters : — The skin was sometimes naked, sometimes furnished with a well-developed exoskeleton, consisting of bony shields, much resembling those of the Crocodiles. A few of the anterior ver- tebrae were opisthoccelous, the remainder having flat or slightly biconcave bodies. The anterior trunk-ribs were double-headed. The teeth were confined to the jaws and implanted in distinct sockets. There were always two pairs of limbs, and these were strong, furnished with claws, and adapted for terrestrial pro- gression. In some cases the fore-limbs were very small in proportion to the size of the hind-limbs. No clavicles have been discovered. The most familiar examples of the Dinosauria are Megalo- saurus and Iguanodon. Megalosaurus is a gigantic Oolitic Reptile, which occurs also in the Cretaceous series (Weald Clay). Its length has been estimated at between forty and fifty feet, the femur and tibia each measuring about three feet in length. As the head of the femur is set on nearly at right angles with the shaft, whilst all the long bones contain large medullary cavities, there can be no doubt but that Megalosaurus was terrestrial in its habits. That it was carnivorous and destructive in the highest degree is shown by the powerful, pointed, and trenchant teeth. The Iguanodon is mainly, if not exclusively, Cretaceous, being especially characteristic of the great delta-deposit of the Wealden. The length of the Iguanodon has been estimated as being probably from fifty to sixty feet, and from the close re- semblance of its teeth to those of the living Iguanas, there is little doubt that it was herbivorous and not carnivorous. The femur of a large Iguanodon measures from four to five feet in length, with a circumference of twenty-two inches in its smallest part. From the disproportionately small size of the fore-limbs, 422 MANUAL OF ZOOLOGY. and from the occurrence of pairs of gigantic three-toed foot- steps in the same beds, it has been concluded, with much pro- bability, that Iguanodon, in spite of its enormous bulk, must have walked temporarily or permanently upon its hind-legs, thus coming to present a most marked and striking affinity to the Birds. The most remarkable, however, of the Dinosauria is the little Compsognathus longipes from the Lithographic Slate of Solenhofen, referred to this order by Professor Huxley. This Reptile is not remarkable for its size, which does not seem to have been much more than two feet, but for the remarkable affinities which it exhibits to the true Birds. The head of Compsognathus was furnished with toothed jaws, and supported upon a long and slender neck. The fore-limbs were very short, but the hind-limbs were long and like those of Birds. The proximal portion of the tarsus resembled that of Birds in being anchylosed to the lower end of the tibia ; but the distal portion of the tarsus — unlike that of Birds — was free, and was not anchylosed with the metatarsus. Huxley concludes that " it is impossible to look at the conformation of this strange Reptile, and to doubt that it hopped or walked in an erect or semi-erect position, after the manner of a bird, to which its long neck, slight head, and small anterior limbs must have given it an extraordinary resemblance." CHARACTERS OF AVES. 423 DIVISION II. SAUROPSIDA. CHAPTER LXVI. CLASS IV. — AVES. THE fourth class of the Vertebrata is that of Aves, or Birds. The Birds may be shortly defined as being " oviparous Verte- brates with warm blood, a double circulation, and a covering of feathers " (Owen). More minutely, however, the Birds are defined by the possession of the following characters : — The embryo possesses an amnion and allantois, and branchiae or gills are never developed at any time of life upon the visceral arches. The skull articulates with the vertebral column by a single occipital condyle. Each half or ramus of the lower jaw consists of a number of pieces, which are separate from one another in the embryo ; and the jaw is united with the skull, not directly, but by the intervention of a quadrate bone (as in the Reptiles). The fore-limb in no existing birds possesses more than three fingers or digits, and the metacarpal bones are anchylosed together. In all living Birds the fore-limbs are useless as regards prehension, and in most they are organs of flight. The hind-limbs in all Birds have the ankle-joint placed in the middle of the tarsus, the proximal portion of the tarsus coalescing with the tibia, and the distal portion of the tarsus being anchylosed with the metatarsus to constitute a single bone known as the " tarso-metatarsus." The heart consists of four chambers, two auricles, and two ventricles; and not only are the right and left sides of the heart completely separated from one another, but there is no communication between the pulmonary and systemic circula- tions, as there is in Reptiles. There is only one aortic arch, the right. The blood is hot, having an average temperature of as much as 103° to 104°. The blood-corpuscles are oval and nucleated. The respiratory organs are in the form of spongy cellular lungs, which are not freely suspended in pleural sacs; and the bronchi open on their surface into a number of air-sacs, placed in different parts of the body. 424 MANUAL OF ZOOLOGY. All birds .are oviparous, none bringing forth their young alive, or being even ovo - viviparous. All birds are, lastly, provided with an epidermic covering, so modified as to con- stitute what are known as feathers. Professor Huxley's account of the method in which feathers are produced is so remarkably clear, that no apology is neces- sary for quoting it in its entirety. Feathers "are evolved within sacs from the surface of conical papillae of the dermis. The external surface of the dermal papilla, whence a feather is to. be developed, is provided upon its dorsal surface with a median groove, which becomes shallower towards the apex of the papilla. From this median groove lateral furrows pro- ceed at an open angle, and passing round upon the under surface of the papilla, become shallower, until, in the middle line, opposite the dorsal median groove, they become obso- lete. Minor grooves run at right angles to the lateral furrows. Hence the surface of the papilla has the character of a kind of mould, and if it were repeatedly dipped in such a substance as a solution of gelatine, and withdrawn to cool until its whole surface was covered with an even coat of that substance, it is clear that the gelatinous coat would be thickest at the basal or anterior end of the median groove, at the median ends of the lateral furrows, and at those ends of the minor grooves which open into them; whilst it would be very thin at the apices of the median and lateral grooves, and between the ends of the minor grooves. If, therefore, the hollow cone of gelatine, removed from its mould, were stretched from within, or if its thinnest parts became weak by drying, it would tend to give way, along the inferior median line, opposite the rod- like cast of the median groove, and between the ends of the casts of the lateral furrows, as well as between each of the minor grooves, and the hollow cone would expand into a flat feather-like structure, with a median shaft, as a ' vane ' formed of ' barbs ' and * barbules.' In point of fact, in the develop- ment of a feather, such a cast of the dermal papilla is formed, though not in gelatine, but in the horny epidermic layer de- veloped upon the mould, and, as this is thrust outwards, it opens out in the manner just described. After a certain period of growth the papilla of the feather ceases to be grooved, and a continuous horny cylinder is formed, which constitutes the 'quill.'" A typical feather (fig. 166) consists of the following parts : — i. The "quill" or "barrel" (a), which forms the basal portion of the feather, by which it is inserted in the skin on its own dermal papilla. It is the latest-formed portion of the fea- CHARACTERS OF AVES. 425 ther, and consists of a hollow horny cylinder. 2. The " shaft," (b) which is simply a continuation of the quill, and which forms the central axis of the feather. The inferior surface of the shaft always exhibits a strong longitu- dinal groove, and it is composed of a horny external sheath, con- taining a white spongy substance, very like the pith of a plant. 3. The shaft carries the lateral ex- pansions or "webs" of the fea- ther, collectively constituting the "vane." Each web is composed of a number of small branches, which form an open angle with the shaft, and which are known as the "barbs" (c). The margins of each barb are, in turn, furnish- ed with a series of still smaller branches, which are known as the " barbules." As a general rule, the extremities of the barbules are hooked, so that those springing from the one side of each barb interlock with those springing from the opposite side of the next barb. In this way the barbs are kept in apposition with one another over a greater or less portion of the entire web. More or less of the barbs in the lower portion of the feather are, how- ever, disunited, and not connected by their barbules ; and these con- stitute what is known as the "down." In the Ostriches, Emeus, and some others, all the barbs of the feathers are discon- nected, giving to the plumage of these birds its peculiarly soft character. At the point where the shaft joins the quill there is very generally found a small feather, known as the " accessory plume," or " plumule." This is usually much the same in structure as the main feather, but considerably smaller. It Fig. 166.— Quill-feather (Stenopsis). a Quill or barrel ; b Shaft ; c c Webs, composed of the barbs, and together forming the "vane." 426 MANUAL OF ZOOLOGY. may, however, be as large as the original feather, or it may be reduced to nothing more than a tuft of down. The feathers vary in different parts of the bird, and are generally divided into those which cover the body — " clothing feathers," and those which occur in the wings and tail — " quill- feathers." As regards the great quill-feathers of the wings, the longest are those which arise from the bones of the hand, and they are called the " primaries." Those which arise from the distal end of the fore-arm (radius and ulna) are termed the " secondaries," and those which are attached to the proximal end of the fore-arm are the " tertiaries." The feathers which lie over the humerus and scapula are the " scapulars." The rudimentary "thumb" also carries some quills, which form what is known as the "alula," or " bastard - wing. " The smaller feathers, which cover the bases of the quill-feathers above and below, are the "wing-coverts" — "greater," "lesser," and " under." The great quill-feathers of the tail (" rectrices") form a kind of fan of great use in steering the bird in flight, and their bases are covered by a series of feathers which constitute the " tail-coverts." The entire skeleton of the Birds is singularly compact, and at the same time singularly light. The compactness is due to the presence of an unusual amount of phosphate of lime; and the lightness, to the absence in many of the bones of the ordinary marrow, and its replacement by air. As regards the vertebral column, birds exhibit some very in- teresting peculiarities. The cervical region of the spine is unusually long and flexible, since the fore-limbs are useless as organs of prehension — and all acts of prehension must be exer- cised either by the beak or by the hind-feet, or by both acting in conjunction. In all birds alike, the neck is sufficiently long and flexible to allow of the application of the beak to an oil- gland placed at the base of the tail, this act being necessary for the due performance of the operation of " preening " — that is, of lubricating and cleaning the plumage. The number of vertebrae in the neck varies from nine to twenty-four, and their structure is always such as to allow of considerable freedom of motion one upon the other. The dorsal vertebrae vary from six to ten in number, and of these the anterior four or five are generally anchylosed with one another, so as to give a base of resistance to the wings. In the Cursorial birds, however (such as the Ostrich and Emeu), and in some others (such as the Penguin), in which the power of flight is wanting, the dorsal vertebrae are all more or less freely movable one upon another. There are no lumbar vertebrae, but all the vertebrae between - CHARACTERS OF AVES. 427 the last dorsal and the first caudal (varying from nine to twenty) are anchylosed together to form a bone which is ordi- narily known as the " sacrum." To this, in turn, the iliac bones are anchylosed along its whole length, giving perfect immo- bility to this region of the spine and to the pelvis. The coccygeal or caudal vertebrae vary in number from eight to ten, and are movable »upon one another. The most noticeable feature about this part of the spinal column is what is known as the " ploughshare-bone." This is the last joint of the tail, and is a long, slender, ploughshare-shaped bone, de- stitute of lateral processes, and without any medullary canal (fig. 170, B). In reality it consists of two or more of the caudal vertebrae, completely anchylosed, and fused into a single mass. It is usually set on to the extremity of the spine at an angle more or less nearly perpendicular to the axis of the body; and it affords a firm basis for the support of the great quill-feathers of the tail (" rectrices"). It also supports the coccygeal oil-glands, and can be raised at pleasure, so as to meet the bill, when the operation of preening is in pro- gress. In the Cursorial Birds, which do not fly, the terminal joint of the tail is not ploughshare-shaped. In the extraordi- nary Mesozoic bird, the Archaopteryx macrura, there is no ploughshare-bone, and the tail consists of twenty separate vertebrae, all distinct from one another, and each carrying a pair of quill-feathers, one on each side (fig. 183). As the vertebrae of the ploughshare-bone are distinct from one another in the embryos of existing birds, the tail of the Archaopteryx is to be regarded as a case of the permanent retention in the adult of an embryonic character. In the increased number of caudal vertebrae, however, and in some other characters, the tail of the Archczopteryx makes a decided approach to the true Reptiles. The various bones which compose the skull of Birds are amalgamated in the adult so as to form a single piece, and the sutures even are obliterated, the lower jaw alone remaining movable. The occipital bone carries a single occipital condyle only, and this is hemispherical or nearly globular in shape. The " beak" (fig. 167), which forms such a conspicuous feature in all birds, consists of an upper and lower half, or a " superior" and " inferior mandible." The upper mandible is composed almost entirely of the greatly elongated intermaxillary bones, flanked by the comparatively small superior maxillae. The inferior mandible is primitively composed of twelve pieces, six on each side; but in the adult these are all indistinguishably amal- gamated with one another, and the lower jaw forms a single 428 MANUAL OF ZOOLOGY. piece. As in the Reptiles, the lower jaw articulates with the skull, not directly, but through the intervention of a distinct bone — the quadrate bone or tympanic bone — which always re- |Fig. 167. — Skull of Spur-winged Goose (Plectrofiterus Gambensis). mains permanently movable, and is never anchylosed with the skull. In no bird are teeth ever developed in either jaw, but both mandibles are encased in horn, forming the beak, and the margins of the bill are sometimes serrated. The thoracic cavity is bounded by the dorsal vertebrae, which are usually, as before said, anchylosed to one another to a greater or less extent. Laterally, the thorax is bounded by the ribs, which vary in number from six to ten pairs. In most birds each rib carries a .peculiar process — the "uncinate pro- cess"— which arises from its posterior margin, is directed up- wards and backwards, and passes over the rib next in succes- sion behind, where it is bound down by ligament. The first and last dorsal ribs carry no uncinate processes, and in some cases the processes continue throughout life as separate pieces (fig. 1 68, B). Anteriorly, the ribs articulate with a series of straight bones, which are called the " sternal ribs," but which in reality are to be looked upon as the ossified " costal carti- lages." These sternal ribs (fig, 168, B) are in turn movably articulated to the sternum in front, and " they are the centres upon which the respiratory movements hinge" (Owen). In front the thoracic cavity is completed by an enormously-ex- panded sternum or breast-bone, which in some birds of great powers of flight extends over the abdominal cavity as well, in some cases even reaching the pelvis. The sternum of all birds which fly, is characterised by the presence of a greatly- developed median ridge or keel (fig. 168, A), to which are at- tached the great pectoral muscles which move the wings. As a general rule, the size of this sternal crest allows a very tolerable estimate to be formed of the flying powers of the bird to which CHARACTERS OF AVES. 429 it may have belonged ; and in the Ostriches and other birds which do not fly, there is no sternal keel. At its anterior angles the sternum exhibits two pits for the attachment of the coracoid bones. Fig. 168. — A, Breast-bone, shoulder-girdle, and fore-limb of Penguin (after Owen): b Sternum, with the sternal keel ; s s Scapulae ; k k Coracoid bones ; c Furculum or merry-thought, composed of the united clavicles ; h Humerus ; u Ulna ; r Radius ; t Thumb ; tn Metacarpus ; p Phalanges of the fingers. B, Ribs of the Golden Eagle : a a Ribs giving off (b b) uncinate processes ; c c bternal ribs. The scapular or pectoral arch consists of the shoulder-blade or scapula, the collar-bone or clavicle, and the coracoid bone, on each side. The scapula, as a rule (fig. 168, A, s s), is a simple elongated bone, not flattened out into a broad plate, and carrying no transverse ridge, or spinous process. Only a portion of the glenoid cavity for the articulation with the head of the humerus is formed by the scapula, the remainder being formed by the coracoid. The coracoid bones (fig. 168, A, k k) correspond with the coracoid processes of man, but in birds they are distinct bones and are not anchylosed with the scap- ula. The coracoid bone on each side is always the strongest of the bones forming the scapular arch. Superiorly it articu- lates with the clavicle and scapula, and forms part of the gle- noid cavity for the humerus. Inferiorly each coracoid bone articulates with the upper angle of the sternum. The position of the coracoids is more or less nearly vertical, so that they 430 MANUAL OF ZOOLOGY. form fixed points for the action of the wings in their down- ward stroke. The clavicles (fig. 168, A, c) are rarely rudimen- tary or absent, and are in some few cases separate bones. In the great majority, however, of birds, the clavicles are anchy- losed together at their anterior extremities, so as to form a single bone, somewhat V-shaped, popularly known as the "merry-thought," and technically called the "furculum." The outer extremities of the furculum articulate with the scapula and coracoid ; and the anchylosed angle is commonly united by ligament to the top of the sternum: The function of the clavicular or furcular arch is "to oppose the forces which tend to press the humeri inwards towards the mesial plane, during the downward stroke of the wing" (Owen). Consequently the clavicles are stronger, and their angle of union is more open, in proportion to the powers of flight possessed by each bird. We have next to consider the structure of the bones which compose the fore - limb or " wing " of the bird ; and as this organ is the one which chiefly conditions the pecu- liar life of the bird, it is in it that we find some of the most characteristic points of struc- ture in the whole skeleton. Though considerably modi- fied to suit its function as an organ of aerial progression, the wing of the bird is readily seen to be homologous with the arm of a man or the fore- limb of a Mammal (fig. 168, A, and fig. 169). The upper arm (brachium) is supported by a single bone, the humerus, which is short and strong, and articulates above with the arti- cular cavity formed partly by the scapula and partly by the coracoid (fig. l6o, Jl). The , ,\ ° " ' / humeniS IS SUCCCCded dlStally by the fore-arm (antibrachium) Fig. 169. - Fore-limb of the Jer-falcon. k Humerus; r Radius; u Ulna; / "Thumb;" m Metacarpals, anchylosed 1 extremities ; ** phalanees of constituted by the normal two bones, the radius and ulna (fig. 169, r, u), of which the radius is much the smaller and more slender, and the ulna much CHARACTERS OF AVES. 431 the larger and stronger. The ulna and radius are followed inferiorly by the bones of the wrist or carpus; but these are reduced in number to two small bones, "so wedged in between the antibrachium and metacarpus as to limit the mo- tions of the hand to those of abduction and adduction neces- sary for the folding up and expansion of the wing ; the hand is thus fixed in a state of pronation ; all power of flexion, exten- sion, or of rotation, is removed from the wrist-joint, so that the wing strikes firmly, and with the full force of the con- traction of the depressor muscles, upon the resisting air" (Owen). One other bone of the normal carpus (namely, the " os magnum") is present, but this is anchylosed with one of the metacarpals. There are thus really three carpal bones, though only two appear to be present. The carpus is followed by the metacarpus, the condition of which agrees with that of the carpal bones. The two outermost of the normal five metacarpals are absent, and the remaining three are anchy- losed— together with the os magnum — so as to form a single bone (fig. 169, m). This bone, however, appears externally as if formed of two metacarpals united to one another at their extremities, but free in their median portion. The metacarpal bone which corresponds to the radius is always the larger of the two (as being really composed of two metacarpals), and it carries the digit which has the greatest number of phalanges. This digit corresponds with the " index" finger, and it is com- posed of two, or sometimes three, phalanges (fig. 169, /). At the proximal end of this metacarpal, at its outer side, there is generally attached a single phalanx, constituting the so-called " thumb " (fig. 169, /), which carries the " bastard-wing." The digit which is attached to the ulnar metacarpal corresponds to the " ring finger," and never consists of more than a single phalanx (fig. 169). As regards the structure of the posterior extremity or hind- limb, the pieces which compose the innominate bones (namely, the ilium, ischium, and pubes) are always anchylosed to one another ; and the two innominate bones are also always an- chylosed, by the medium of the greatly-elongated ilia, to the sacral region of the spine. In no living bird, however, with the single exception of the Ostrich, are the innominate bones united in the middle line in front by a symphysis pubis. The stability of the pelvic arch, necessary in animals which sup- port the weight of the body on the hind-limbs alone, is amply secured in all ordinary cases by the anchylosis of the ilia with the sacrum. As in the higher Vertebrates, the lower limb (fig. 170, A) 432 MANUAL OF ZOOLOGY. consists of a femur, a tibia and fibula, a tarsus, metatarsus, and phalanges ; but some of these parts are considerably ob- scured by anchylosis. The femur or thigh-bone (fig. 170, A,/") is generally very short, comparatively speaking. The chief Fig. 170. — A, Hind-limb of the Loon (Colymbus glacialis) — after Owen : i Innominate bone ; f Thigh-bone or femur ; / Tibia, with the proximal portion of the tarsus an- chylosed to its lower end ; r Fibula ; m Tarso-metatarsus, consisting of the distal portion of the tarsus anchylosed with the metatarsus ; f p Phalanges of the toes. B, Tail of the Golden Eagle : j Ploughshare-bone, carrying the great tail-feathers. bone of the leg is the tibia (/), to which a thin and tapering fibula (r} is anchylosed. The upper end of the fibula, how- ever, articulates with the external condyle of the femur. The ankle-joint is placed, as in Reptiles, between the proximal and distal portions of the tarsus. The proximal portion of the tarsus is undistinguishably amalgamated with the lower end of the tibia. The distal portion of the tarsus is anchylosed with the whole of the metatarsus to constitute the most characteristic bone in the leg of the Bird — the " tarso-metatarsus " (m). In most of the long-legged birds, such as the waders, the dispro- portionate length of the leg is given by an extraordinary elon- gation of the tarso-metatarsus. CHARACTERS OF AVES. 433 The tarso-metatarsus is followed inferiorly by the digits of the foot. In most birds the foot consists of three toes directed forwards and one backwards — four toes in all. In no wild bird are there more than four toes, but often there are only three, and in the Ostrich the number is reduced to two. In all birds which have three anterior and one posterior toe, it is the posterior thumb or hallux (that is to say, the innermost digit of the hind-limb) which is directed backwards ; and it invariably consists of two phalanges only. The most internal of the three toes which are directed forwards, consists of three phalanges; the next has four phalanges ; and the outermost or " little " toe is made up of five phalanges (fig. 170, A). This increase in an arithmetical ratio of the phalanges of the toes, in proceeding from the inner to the outer side of the foot, ob- tains in almost all birds, and enables us readily to detect which digit is suppressed, when the normal four are not all present. Variations of different kinds exist, however, in the number and disposition of the toes. In many birds — such as the Parrots — the outermost toe is turned backwards, so that there are two toes in front and two behind. In others, again, the outer toe is normally directed forwards, but can be turned backwards at the will of the animal. In the Swifts, on the other hand, all four toes are present, but they are all turned forwards. In many cases — especially amongst the Natatorial birds — the hallux is wholly wanting, or is rudimentary. In the Emeu, Cassowary, Bustards, and other genera, the hallux is in- variably absent, and the foot is three-toed. In the Ostrich both the hallux and the next, toe (" index ") are wanting, and the foot consists simply of two toes, these being the outer toe and the one next to it. The digestive system of birds comprises the beak, tongue, gullet, stomach, intestines, and cloaca. Teeth are invariably wanting in birds, and the jaws are encased in horn, constitut- ing the bill. The form of the bill varies enormously in differ- ent birds, and it is employed for holding and tearing the prey, for prehensile purposes, for climbing, and in some birds as an organ of touch. In these last-mentioned cases the bill is more or less soft, and is supplied with filaments of the fifth nerve. In many birds, too, in which the bill is not soft, the base of the upper mandible is surrounded by a circle of naked skin, constituting what is called the " cere," and this, no doubt, serves also as a tactile organ. The tongue of birds can hardly be looked upon as an organ of taste, since it is generally cased in horn like the mandibles. It is, in fact, principally employed as an organ of prehension ; VOL. II. 2 E 434 MANUAL OF ZOOLOGY. but in some cases — as in the Parrots — it is soft and fleshy, and then, doubtless, is to some extent connected with the sense of taste. It is essentially composed of a prolongation of the hyoid bone (the glosso-hyal), which is sheathed in horn, and is variously serrated or fringed. Salivary glands are invariably present, but they are rarely of large size, and they have often a very simple structure. In accordance with the structure of the neck, the gullet in birds is usually of great length, and it is generally very dilatable. In the carnivorous, or Raptorial, and in the granivorous birds, the gullet (fig. 171, o) is dilated into a pouch, which is situated Fig. 171. — Digestive System of the Common Fowl (after Owen), o Gullet ; c Crop ; / Proventriculus ; g Gizzard ; sm Small intestine ; k Intestinal cseca ; / Large in- testine; cl Cloaca. at the lower part of the neck, just in front of the merry-thought. This is what is known as the " crop " or " ingluvies " (c), and it may be either a mere dilatation of the tube of the gullet, or it may be a single or double pouch. The food is detained in the crop for a longer or shorter time, according to its nature, before it is subjected to the action of the proper digestive organs. The oesophagus, after leaving the crop, shortly opens into a second cavity, which is known as the " proventriculus " or " ventriculus succenturiatus " (/). This is the true digestive cavity, and its mucous membrane is richly supplied with gastric CHARACTERS OF AVES. 435 follicles which secrete the gastric juice. The proventriculus, however, corresponds, not with the whole stomach of the Mam- mals, but only with its cardiac portion ; and it opens into a second, muscular cavity, which corresponds to the pyloric division of the Mammalian stomach. The gizzard (g) is situ- ated below the liver, and forms in all birds an elongated sac, having two apertures above, of which one conducts into the duodenum or commencement of the small intestine, whilst the other communicates with the proventriculus. The two chief forms of gizzard are exhibited respectively by the Raptorial birds, which feed on easily - digested animal food, and the Rasores and some of the Natatores, which feed on hardly- digested grains. In the birds of Rapine the gizzard scarcely deserves the name, being nothing more than a wide membran- ous cavity with thin walls. In the granivorous birds, whose hard food requires crushing, the gizzard is enormously devel- oped ; its lining coat is formed of a thick, horny epithelium, and its walls are extremely thick and muscular. This consti- tutes a grinding apparatus, like the stones of a mill ; whilst the " crop " or oesophageal dilatation may be compared to the " hopper " of a mill, since it supplies to the gizzard " small successive quantities of food as it is wanted " (Owen). Sup- plementing the action of the muscular walls of the gizzard, and acting in the place of teeth, are the small stones or pebbles, which, as is so well known, so many of the granivorous birds are in the habit of swallowing with their food, or at other times. In fact there can be no doubt but that the gravel and pebbles swallowed by these birds is absolutely essential to ex- istence, since the gizzard, without this assistance, is unable properly to triturate the food. The intestinal canal extends from the gizzard to the cloaca, and is comparatively speaking short. The secretions of the liver and pancreas are poured into the small intestine, as in Mammals. The commencement of the large intestine is almost always furnished with two long " caeca " or blind tubes, the length of which varies a good deal in different birds (fig. 171, k). They are sometimes wanting ; and their exact function is un- certain ; though they are most probably connected partly with digestion and partly with excretion. The large intestine is always very short — seldom. more than a tenth part of the length of the body — and it terminates in the "cloaca" (fig. 171, cl). This is a cavity which in all birds receives the termination of the rectum, the ducts of the generative organs and the ureters ; and serves, therefore, for the expulsion of the faeces, the gen- erative products, and the urinary secretion. 436 MANUAL OF ZOOLOGY. Respiration is effected in Birds more completely and actively than in any other class of the Vertebrata, and as the result of this, their average temperature is also higher. This extensive development of the respiratory process is conditioned by the fact that, in addition to true lungs, air is admitted into a greater or less number of the bones, and into a number of cavities — the so-called air-receptacles — which are distributed through vari- ous parts of the body. By this extensive penetration of air into various parts of the body, the aeration of the blood is effected, not only in the lungs, but also over a greater or less extent of the systemic circulation as well ; and hence in Birds this pro- cess attains its highest perfection. The cavities of the thorax and abdomen are not separated from one another by a complete partition, the diaphragm being only present in a rudimentary form. The lungs are two in num- ber, of a bright-red colour, and spongy texture. They are confined to the back of the thorax, extend- ing along each side of the spine, from the second dorsal vertebra to the kidney. They differ from the lungs of the Mammals in not being freely suspended in a pleural membrane. The pleura, on the other hand, is reflected only over the anterior surface of the lungs. The bronchi, or primary divisions of the wind- pipe (fig. 172), dimmish in size as they pass through the lung, by giving off branches, which, in turn, give off the true air-vesicles of the lung. When the bronchial tubes reach the surface of the lung, they open, by a series of dis- tinct apertures, into a series of " air-sacs." These are a series of membranous sacs formed by the continuation of the lining mem- brane of the bronchi, and sup- ported by reflections of the serous membrane of the thoracico- abdominal cavity. In those aquatic birds which, like the Penguin, do not enjoy the power of flight, the air-cells are Fig. 172. — Lung of Goose (after Owen). a Main bronchus dividing into secon- dary branches as it enters the lung, these giving off smaller branches, the openings of which are seen on the back of the bronchial tubes ; b b Bris- tles passed from the bronchi through the apertures on the surface of the lung by which the bronchi communi- cate with the air-receptacles. CHARACTERS OF AVES. 437 restricted to the abdomen; but in most birds they are con- tinued along the sides of the neck and limbs. In some cases — as the Pelican and Gannet — air-receptacles are situated beneath almost the whole of the integument. The air-cells not only greatly reduce the specific gravity of the bird, and thus fit them for an aerial life, but also assist in the mechanical work of respiration, and must also greatly promote the aeration of the blood. In connection with the air-receptacles, and as an extension of them, is a series of cavities occupying the interior of a greater or less number of the bones, and also containing air. In young birds these air-cavities do not exist, and the bones are filled with marrow as in the Mammals. The extent also to which the bones are " pneumatic " varies greatly in different birds. In the Penguin — which does not fly — all the bones contain marrow, and there are no air-cavities. In the large Running Birds (Cursores), such as the Ostrich, the bones of the leg, pelvis, spine, ribs, skull, and sternum are pneumatic; but the bones of the wings, with the exception of the scapular arch, are without air - cavities, and permanently retain their marrow. All birds which fly, with the singular exception of the Woodcock, have air admitted to the humerus. In the Pelican and Gannet, all the bones of the skeleton, except the phalanges of the toes, are penetrated by air; and in the Horn- bill even these are pneumatic. The functions discharged by the air-cavities of the bones appear to be much the same as those of the air-receptacles — namely, that of diminishing the specific gravity of the body and subserving the aeration of the blood. The heart in all Birds consists of four chambers, two auricles and two ventricles. The right auricle and ventricle, constitut- ing the right side of the heart, are wholly concerned with the pulmonary circulation ; the left auricle and ventricle, forming the left side of the heart, are altogether occupied with the systemic circulation ; and no communication normally exists in adult life between the two sides of the heart. In all essen- tial details, both as regards the structure of the heart itself and the course taken by the circulating fluid, Birds agree with Mammals. The venous blood — namely, that which has circu- lated through the body — is returned by the venae cavae to the right auricle, whence it is poured into the right ventricle. The right ventricle propels it through the pulmonary artery to the lungs, where it is aerated, and becomes arterial. It is then sent back by the pulmonary veins to the left auricle, whence it is driven into the left ventricle. Finally, the left ventricle pro- 438 MANUAL OF ZOOLOGY. pels the aerated blood to all parts of the body through the great systemic aorta. The chief difference between Birds and Reptiles as regards the course of the circulation is, that in the Birds the two sides of the heart are completely separated from one another, the blood sent to the lungs being exclusively venous, whereas that which is sent to the body is exclusively arterial. In Reptiles, on the other hand, the pulmonary and systemic circulations are connected together either in, or in the immediate neigh- bourhood of, the heart; so that mixed venous and arterial blood is propelled both through the lungs and through every part of the body. In accordance with their extended respiration and high mus- cular activity, the complete separation of the greater and lesser circulations, and the perfect structure of the heart, Birds main- tain a higher average temperature than is the case with any other class of the Vertebrata. This result is also to a consider- able extent conditioned by the non-conducting nature of the combined down and feathers which form the integumentary covering of Birds. The urinary organs of Birds consist of two elongated kid- neys and two ureters, but there is no urinary bladder. The ureters open into the cloaca, or into a small urogenital sac which communicates with the cloaca. As regards the reproductive organs, the males have two testes placed above the upper extremities of the kidneys, and their efferent ducts (vasa deferentid] open into the cloaca alongside of the ureters. A male organ (penis] may or may not be pre- sent, but there is no perfect urethra. The female bird, as a general rule, is provided with only one ovary and oviduct — that of the left side — the corresponding organs of the right side being rudimentary or absent. The oviduct is very long and tortuous, and the egg, during its passage through it, receives the albuminous covering which serves for the nutrition of the embryo, and which is known as the " white " of the egg. The lower portion of the oviduct is dilated, and the egg receives here the calcareous covering which constitutes the " shell." Finally, the oviduct debouches into the cloaca, into which the egg, when ready, is expelled. The further development of the chick is secured by the process of " incubation " or brooding, for which birds are peculiarly adapted, in consequence of the high temperature of their bodies. The development of the ovum belongs to physiology, and does not concern us here. It is sufficient to notice the means by which in many cases the chick is ultimately enabled to escape CHARACTERS OF AVES. 439 from the egg. When development has reached a stage at which external life is possible, it is of course necessary for the chick to be liberated from the egg, the shell of which is often ex- tremely hard and resistant. To this end, in very many in- stances, the young bird is provided with a little calcareous knob on the point of the upper mandible, and by means of this it chips out an aperture through the shell. Having effected its purpose, this temporary appendage then disappears, without leaving a trace behind. The state of the young upon exclusion from the egg is very different in different cases, and in accordance with this, Birds have been divided into the two sections of the Autophagi or Aves prczcoces, and the Heterophagi or Aves altrices. In the Autophagi the young bird is able to run about and help itself from the moment of liberation from the egg. In the Hetero- phagi the young are born in a blind and naked state, unable to feed themselves, or even to maintain unassisted the necessary vital heat. In these birds, therefore, the young require to be brooded over and fed by the parents for a longer or shorter period after exclusion from the egg. As regards their nervous system, the brain of birds is rela- tively larger, especially as regards the size of the cerebrum proper, than the brain of Reptiles. The cerebellum, though always present, consists simply of the central lobe (the " vermi- form process "), and is not provided with the lateral lobes which occur in the Mammals, or they are only present in a rudimen- tary form. The corpus callosum is absent, and the surface of the cerebral hemispheres is devoid of convolutions. As regards the organs of the senses^ the eyes are always well developed, and in no bird are they ever rudimentary or absent. The chief peculiarity of the eye is that the cornea forms a segment of a much smaller sphere than does the eyeball pro- per, so that the anterior part of the eye is obtusely conical, whilst the posterior portion is spheroidal. Another peculiarity is that the form of the eye is maintained by a ring of from thirteen to twenty bony plates, which are placed in the anterior portion of the sclerotic coat. Eyelashes are almost universally absent ; but in addition to the ordinary upper and lower eye- lids, Birds possess a third membranous eyelid — the " membrana nictitans " — which is sometimes pearly-white, sometimes more or less transparent. This third eyelid is placed on the inner side of the eye, and possesses a special muscular apparatus, by which it can be drawn over the anterior surface of the eye like a curtain, moderating the intensity of the light. As to the organ of hearing, Birds possess no external ear or concha, by 44O MANUAL OF ZOOLOGY. which sounds can be collected and transmitted to the internal ear. In some birds, however, as in the Ostrich and Bustard, the external meatus auditorius is surrounded by a circle of feathers, which can be raised and depressed at will. The ex- ternal nostrils in Birds are usually placed on the sides of the upper mandible, near its base, in the form of simple perfora- tions, which sometimes communicate from side to side by the deficiency of the septum narium. In the singular Apteryx of New Zealand the nostrils are placed at the extreme end or tip of the elongated upper mandible. Sometimes the nostrils are defended by bristles, and sometimes by a scale (Rasores). Taste must be absent, or almost absent, in the great majority of birds, the tongue being nothing more than a horny sheath surrounding a process of the hyoid bone, and serving for deglu- tition or to seize the prey. In the Parrots, however, the tongue is thick and fleshy, and some perception of taste may be present. Touch or tactile sensibility, too, as already re- marked, is very poorly developed in Birds. The body is entirely, or almost entirely, covered with feathers ; the anterior limbs are converted into wings, and rendered thereby useless as organs of touch ; and the posterior limbs are covered with horny scales or feathers. The bill certainly officiates as an organ of touch, but it cannot possess any acute sensibility, as in most birds it is encased in a rigid horny sheath. In some birds, however, such as the common Duck, the texture of the bill is moderately soft, and it is richly supplied with filaments of the fifth nerve ; so that in these cases the bill doubtless con- stitutes a tolerably efficient tactile organ. The " cere," too, or the fleshy scale found at the base of the bill in some birds, is in all probability also used as a tactile organ. The last anatomical peculiarity of Birds which requires notice is the peculiar apparatus known as the " inferior larynx," by which the song of the singing birds is conditioned. "The air-passages of birds commence by a simple superior larynx, from which a long trachea extends to the anterior aperture of the thorax, where it divides into the two bronchi, one for each lung. At the place of its division there exists in most birds a complicated mechanism of bones and cartilages, moved by appropriate muscles, and constituting the true organ of voice; this part is termed the inferior larynx." — (Owen.) The structure of the vocal apparatus is extremely complicated, and there is no necessity for entering upon it here. It is to be remembered, however, that those modifications of the voice which constitute the song of birds, are produced in a special and complex cavity placed at the point where the trachea DIVISIONS OF BIRDS. 44! divides into the two bronchi, and not in a true larynx situated at the summit of the windpipe. Lastly, the trachea of birds is always of considerable proportionate length, and it is often twisted or dilated at intervals, this structure, doubtless, having something to do with the production of vocal sounds.* Before passing on to the consideration of the divisions of Birds, a few words may be said as to the migration of birds. In temperate and cold climates comparatively few birds remain constantly in the same region in which they were hatched. Those which do so remain, are called "permanent birds " (aves manentes). Other birds, such as the Woodpeckers, wander about from place to place, without having any fixed direction. These are called "wandering birds" (aves erratica), and their irregular movements are chiefly conditioned by the scarcity or abundance of food in any particular locality. Other birds, however, at certain seasons of the year, undertake long journeys, usually uniting for this purpose into large flocks. These birds — such as the swallows, for instance — are properly called " migratory birds " (aves migratoritz). The movements of these birds are conditioned by the necessity of having a certain mean temperature, and consequently they leave the cold regions at the approach of winter, and return again for the warmer season. CHAPTER LXVII. DIVISIONS OF BIRDS. i. GENERAL DIVISIONS OF AVES. 2. NATATORES. 3. GRALLATORES. OWING to the extreme compactness and homogeneity of the entire class Aves, conditioned mainly by their adaptation to an aerial mode of life, the subject of their classification has been one of the greatest difficulties of the systematic Zoologist. By Professor Huxley the Birds are divided into the following three orders : — i. SAURUR^E. — In this order the caudal vertebrae are numerous, and there is no ploughshare -bone. The tail is * The student desirous of fuller information as to the anatomy of Birds should consult the masterly article by Owen on "Aves" in the 'Cyclo- paedia of Anatomy and Physiology,' or the second volume of the ' Vertebrata ' of the same author, from which the preceding summary has been chiefly derived. 442 MANUAL OF ZOOLOGY. longer than the body, and the metacarpal bones are not anchy- losed together. This order includes only the single extinct bird the Archceopteryx macmra, in which the long lizard-like tail is only the most striking of several abnormalities. 2. RATITVE.— This order comprises the Running birds, which cannot fly, such as the Ostriches, Emeus, and Cassowaries. It is characterised by the fact that the sternum has no median ridge or keel for the attachment of the great pectoral muscles. The sternum is therefore raft-like (from the Lat. rates, a raft), hence the name of the order. 3. CARINAT^E. — This comprises all the living Flying birds, and is characterised by the fact that the sternum is furnished with a prominent median ridge or keel (carind) ; hence the name of the order. This is probably the nearest approach to a strictly natural classification of Birds which has yet been proposed ; but the order Carinatce is so disproportionately large as compared with the other two, that it would lead to considerable inconvenience if it were to be adopted here. For the purposes of the present work it will be better to adhere, with some modifications, to the classification of the Birds originally proposed by Kirby, and since sanctioned by the adoption of other distinguished naturalists. In this more generally current, but certainly artificial, arrangement, the Birds are divided into the following seven orders, founded chiefly on the habits and mode of life, and on the resulting anatomical or structural peculiarities. To these an eighth order must be added for the reception of the Mesozoic bird, the Archceopteryx, the discovery of which dates from a recent period. Before entering upon a consideration of the individual orders, it will be as well to present to the student, synoptically and in an easily-remembered form, the leading differences between these eight orders : — 1. Natatores or Swimmers. — These are characterised by the fact that the toes are united by a membrane or web ; the legs are short and are placed behind the point of equilibrium of the body. The body is closely covered with feathers, and with a thick coating of down next the skin. (Ex. Ducks, Geese, Pelicans, Gulls.) 2. Grallatores or Waders. — The Wading birds are charac- terised by the possession of long legs, which are naked or are not covered with feathers from the distal end of the tibia downwards. The toes are long, straight, and not united to one another by a membrane or web. (Ex. Curlews, Herons, Storks.) DIVISIONS OF BIRDS. 443 3. Cur sores or Runners. — The Cursorial birds have very short wings which are not used in flight, and the sternum is without a ridge or keel. The legs are exceedingly robust, and there are only two or at most three developed toes, the hind- toe or hallux being always absent or quite rudimentary. The order agrees with the Ratitce. of Huxley. (Ex. Ostrich, Emeu, Apteryx. ) 4. Rasores or Scratchers. — The Rasorial birds have usually strong feet with powerful blunt claws adapted for scratching, but sometimes for perching. All the four toes are present. The upper mandible is vaulted, and the nostrils are pierced in a membranous space at its base, and are covered by a cartilaginous scale. (Ex. Fowls, Game-birds, Pigeons.) 5. Scansores or Climbers. — The Climbing birds are charac- terised by the structure of the foot, in which two toes are turned backwards and two forwards, so as to give the bird unusual facilities in climbing trees. (Ex. Parrots, Toucans, Woodpeckers.) 6. Insessores or Perchers. — The Insessorial or Passerine birds are characterised by having slender and short legs, with three toes before and one behind, the two external toes generally united by a very short membrane, and the whole foot being adapted for perching. This is by far the largest order of birds, and includes all our ordinary songsters, such as the Thrushes, Linnets, Larks, &c., together with the Swallows, Humming- birds, and many others. 7. Raptor es or Birds of Prey. — The Birds of Rapine are characterised by their strong, curved, sharp-edged and sharp- pointed beak, adapted for tearing animal food ; and by their robust legs armed with four toes, three in front and one behind, all furnished with long, strong, crooked claws or talons. (Ex. Eagles, Hawks, Owls.) 8. Saurura. — The metacarpal bones are not anchylosed together, and the tail is longer than the body, and consists of numerous free vertebrae, without a terminal ploughshare-bone. The only member of this order is the extinct Archceopteryx. ORDER I. NATATORES. — The order of the Natatores or Swim- mers comprises a number of birds which are as much or even more at home in the water than upon the land. In accordance with their aquatic habit of life, the Natatores have a boat- shaped body, usually with a long neck. The legs are short, and placed behind the centre of gravity of the body, this position enabling them to act admirably as paddles, at the same time that it renders the gait upon dry land more or less 444 MANUAL OF ZOOLOGY. awkward and shuffling. In all cases the toes are " webbed " or united by membrane to a greater or less extent (fig. 173, A). In many instances the membrane or web is stretched com- pletely from toe to toe, but in others the web is divided or split up between the toes, so that the toes are fringed with membranous borders, but the feet are only imperfectly webbed. As their aquatic mode of life exposes them to great reductions of temperature, the body of the Natatorial birds is closely covered with feathers and with a thick coating of down next the skin. They are, further, prevented from becoming wet in the water by the great development of the coccygeal oil-gland, by means of which the plumage is kept constantly lubricated and waterproof. They are usually polygamous, each male consorting with several females ; and the young are hatched in a condition not requiring any special assistance from the parents, being able to swim and procure food for themselves from the moment they are liberated from the egg. Fig. 173. — Natatores. A, Foot of Cormorant (Phalacrocorax) ; B, Beak of the Bean-goose (A riser segetum). The Natatores are divided by Owen into the following four families : — Fam. i. BrevipennatcB. — In this family of the swimming birds the wings are always short, and are sometimes useless as organs of flight, the tail is very short, and the legs are placed very far back, so as to render terrestrial progression very diffi- cult or awkward. The family includes the Penguins, Auks, Guillemots, Divers, and Grebes. In the Penguins (Sphcnisddafy the wings are completely rudimentary, without quills, and cov- ered with a scaly skin. They are useless, as far as flight is con- cerned, but they are employed by the bird as fins, enabling it to swim under water with great facility. The feet are webbed, and the hinder toe is rudimentary or wanting. The Pen- guins live in the seas of the southern hemisphere, on the coasts NATATORES. 445 of South Africa and South America, especially at Terra del Fuego, and in the solitary islands of the South Pacific. When on land the Penguins stand bolt upright, and as they usually stand on the shore in long lines, they are said to present a most singular appearance. In the Auks (Alcidcz) the wings are better developed than in the Penguins, and they contain true quill- feathers; but they are still short as compared with the size of the body, and are of more use as fins than for flight. The great Auk or Gare-fowl (Alca impennis) is remarkable for being one of the birds which appear to have become entirely extinct within the human period, having been, in fact, destroyed by man himself. It used to abound in the arctic regions, and occasionally visited our own shores in the winter. The little Auk (Mergulus alba) occurs still in abundance in the seas of the arctic regions. Other well-known members of this group are the Razor-bill, the Puffins (Fratercula arctica), and the Guil- lemots (Uria). In the Divers (Colymbidat), comprising the true Divers and the Grebes, the power of flight is pretty well developed, but the bird still is much more active in the water, swimming or diving, than on land. The Grebes are not uncommon in our own country, and are largely killed for making muffs, collars, and other articles of winter dress. They have the membrane between the toes deeply incised. In the Divers proper the front toes are completely united by a membrane. The Nor- thern Diver or Loon (Colymbus glacialis) is a familiar example, and is found on the coasts of high northern latitudes. Fam. 2. Longipennatce. — This family of Natatores is charac- terised by the well-developed wings, the pointed, sometimes knife-like, sometimes hooked bill, and by never having the hallux united with the anterior toes by a membrane. The fol- lowing are the more important groups coming under this head : — a. Laridce, or Gulls and Terns, having powerful wings, a free hinder toe, and the three anterior toes united by a membrane. The Gulls form an exceedingly large and widely distributed group of birds ; and the Terns or Sea-swallows are equally beautiful, if not quite so common. b. Procellaridce, or Petrels, closely resembling the true Gulls, but having no hinder toe, and having the upper mandible strongly hooked. The smaller species of Petrel are well known to all sailors under the name of Storm-birds and Mother Carey's Chickens. The largest member of the group is the gigantic Albatross (Diomedea exulans\ not uncommonly found far from land in both the northern and southern oceans. The 446 MANUAL OF ZOOLOGY. Albatross sometimes measures as much as fifteen feet from the tip of one wing to that of the other, and their flight is powerful in proportion. Fam. 3. Totipalmatce, characterised by having the hinder toe or hallux more or less directed inwards, and united to the innermost of the anterior toes by a membrane (fig. 173, A). In this family are the Pelicans, Cormorants, Gannets, Frigate- birds, Darters, and others. The Pelicans (Pelicanidce) are large birds, which subsist on fish, and are found in Europe, Asia, Africa, and the New World. They sometimes measure as much as from ten to fif- teen feet between the tips of the wings, and most of the bones are pneumatic, so that the skeleton is extremely light. The lower mandible is composed of two flexible branches which serve for the support of a large " gular " pouch, formed by the loose unfeathered skin of the neck. The fish captured by the bird are temporarily deposited in this pouch, and the parent birds feed their young out of it. In the Cormorants (Phalacrocorax) there is no pouch be- neath the lower mandible, but the skin of the throat is very lax and distensible. They are widely distributed over the world, one species being very abundant in many parts of Europe. The Gannets (Sula) have a compressed bill, the mar- gins of which are finely crenate or toothed. They occur abundantly on many parts of the coasts of northern Europe, one of the most noted of their stations being the Bass Rock at the mouth of the Firth of Forth. Another species (Sula varie- gatd] is of greater importance to man, as being one of the birds from the accumulated droppings of which guano is derived. The Frigate-birds (Tachypetes) are chiefly remarkable for their extraordinary powers of flight, conditioned by their enormously long and powerful wings and long forked tail. They occur on the coasts of tropical America, and are often found at im- mense distances from any land. The Darters (Plotus) are somewhat aberrant members of this group, characterised by their elongated necks and long pointed bills. They occur in America, Africa, and Australia, and catch fish by suddenly darting upon them from above. Fam. 4. Lamellirostres. — The last family of the Natatores is that of the Lamellirostres, including the Ducks, Geese, Swans, and Flamingos ; and characterised by the form of the beak (figs. 167, 173), which is flattened in form and covered with a soft skin. The edges of the bill are further furnished with a series of transverse plates or lamellae, which form a kind of fringe or " strainer," by means of which these birds sift the NATATORES. 447 mud in which they habitually seek their food. The bill is richly supplied with filaments of the fifth nerve, and doubtless serves as an efficient organ of touch. The feet are furnished with four toes, of which three are turned forwards, and are webbed, whilst the fourth is turned backwards, and is free. The trachea in the males is generally enlarged or twisted in its lower part, and co-operates in the production of the peculiar clanging note of most of these birds. The body is heavy, and the wings only moderately developed. The groups of the Ducks (Anatida), Geese \Anserina\ and Swans ( Cygnida\ are too familiar to require any special notice. The Flamingos, however, forming the group of the Phcenicop- teridce, require some notice ; if only for the fact that the legs are so long and slender that they have often been placed in the order Grallatores on this account. The three anterior toes, however, are webbed or completely united by membrane, and the bill is lamellate, so that there can be little hesitation in leaving the Flamingo in its present position amongst the Nata- tores. The common Flamingo (Phoznicopterns ruber) occurs abundantly in various parts of southern Europe. It stands between three and four feet in height, the general plumage being rose-coloured, the wing-coverts red, and the quill-feathers of the wings black. The tongue is fleshy, and one of the extrava- gances of the Romans during the later period of the Empire was to have dishes composed solely of Flamingos' tongues. Other species occur in South America and Africa. ORDER II. GRALLATORES. — The birds comprising the order of the Grallatores, or Waders, for the most part frequent the banks of rivers and lakes, the shores of estuaries, marshes, la- goons, and shallow pools, though some of them keep almost ex- clusively to dry land, preferring, however, moist and damp situa- tions. In accordance with their semi-aquatic amphibious habits, the Waders are distinguished by the great length of their legs ; the increase in length being mainly due to the great elongation of the tarso-metatarsus. The legs are also unfeathered from the lower end of the tibia downwards. The toes are elongated and straight (fig. 174, A), and are never completely palmate, though sometimes semi-palmate. There are three anteriqr toes, and usually a short hallux, but the latter may be wanting. The wings are long, and the power of flight usually considerable ; but the tail is short, and the long legs are stretched out behind in flight to compensate for the brevity of the tail. The body is generally slender, and the neck and beak usually of consid- erable length (fig. 174, B). They are sometimes polygamous, 448 MANUAL OF ZOOLOGY. sometimes monogamous, and the young of the former are able to run about as soon as they are hatched. Fig. 174. — Grallatores. A, Leg and foot of the Curlew; B, Head of Snipe; C, Beak of the Avocet. The most typical Waders — those, namely, which are semi- aquatic in their habits — spend most of their time wading about in shallow waters or marshes, feeding upon small fishes, worms, shell-fish, or insects. Others, such as the Storks, live mostly upon the land, and are more or less exclusively vegetable- feeders. The Grallatores are divided by Owen into the four families of the Macrodactyli, the Cultirostres^ the Longirostres, and the Pressirostres. Fam. i. Macrodactyli. — In this family the feet are furnished with four elongated, sometimes lobate, toes, and the wings are of moderate or less than average size. In many of their char- acters a considerable number of the birds of this family ap- proach the Rasorial birds, and differ from the true Waders. The beak is mostly short, rarely longer than the head, and is compressed from side to side, or wedge-shaped. The legs are strong and not particularly lengthy ; but the toes are often of great length, and are furnished with long claws. The neck is not very long, and the tail is very short. Some of them are strictly aquatic in their habits, and, like the Coots, approach in many respects to the Natatores; others, again, are exclusively terrestrial. The most familiar members of this family are the Rails (Rallida\ Water-hens (Gallinula), the Coots (Fulica\ and the Jacana (Parra jacana}. The Water-hens and Coots are aquatic or semi-aquatic, swimming and diving with great GRALLATORES. 449 ease. In the Coots the toes are semi-palmate, being bordered by membranous lobes, like the toes of the Grebes. Amongst the Coots should probably be placed the Aotornis (Owen), long supposed to be extinct, but recently proved to be still living in the Middle Island of New Zealand. The Notornis is much larger than the ordinary Coots, and is remarkable in the fact that, like many extinct and some living New Zealand birds, the wings are so rudimentary as to be useless for flight. The true Rails, comprising the common Land -rail (Rallus aquaticus), and the Corn-crake (Crex pratensis) of our own country, live almost exclusively on land, though the former usually frequents damp or marshy places. In the Jacanas, lastly, the feet are furnished with excessively long and slender toes, which enable the bird to run about upon the leaves of aquatic plants. Fam. 2. Cultirostres. — In this family of the Grallatores are some of the most typical and familiar forms contained in the entire order. The bill in this family is long — usually longer than the head — and is compressed from side to side ; the legs are long and slender, having a considerable portion of the tibiae unfeathered; and the feet have four toes, which are usually connected to a greater or less extent at their bases by membrane. In this family are the Cranes, Herons, Stork, Ibis, Spoonbill, and others of less importance. The Cranes (Gruidce) are large and elegant birds, and are chiefly remarkable for their long migrations, which were noticed by many classical authors. In these journeys the Cranes usually fly in large flocks, led by a single leader, so that the whole assemblage assumes a wedge-like form; or they fly in long lines. The common Crane (Grus cinerea) breeds in the north of Europe and Siberia, and migrates southwards at the approach of winter. The Herons (Ardeida) are familiarly known to every one in the person of the common Gray or Crested Heron (Ardea cinerea). It was one of the birds most generally pursued in the now almost extinct sport of falconry. Various species of Heron are found over the whole world, both in temperate and hot climates. The Ibises (Tantalina) form a group of beautiful birds, species of which occur in all the warm countries of the world. One, the Ibis religiosa, was regarded by the ancient Egyptians as a deity, and was treated with divine honours, being often embalmed along with their mummies, or figured on their monuments. The Storks (Cicomttit) are large birds, of which one, the common Stork (Ciconia alba), is rarely found in Britain, but VOL. II. 2 F 450 MANUAL OF ZOOLOGY. occurs commonly on the Continent, where it is often semi- domesticated. The Spoonbills (Ptataleadtz) are also large birds, very like the Storks, but the bill is flattened out so as to form a broad spoon-like plate. The common White Spoonbill (Platalea leucorodia) is found commonly on the Continent, but is of very rare occurrence in Britain. Fam. 3. Longirostres. — The third family of Waders is that of the Longirostres, characterised by the possession of long, slender, soft bills, grooved for the perforations of the nostrils (fig. 174, B). The legs are sometimes rather short, sometimes of great length; the toes are of moderate length, and the hallux is usually short, and is sometimes absent. The bill in these birds serves as an organ of touch, being used as a kind^ of probe to feel for food in mud or marshy soil. To fulfil this purpose, the tip of the bill is furnished with numerous filaments of the fifth nerve. They feed mostly upon insects and worms, and are not strictly aquatic in their habits, mostly frequenting marshy districts, moors, fens, the banks of rivers or lakes, or the shores of the sea. In this family of the Long-billed Waders are the Snipes (Scolopatidce), the Sandpipers (Tringidce), the Curlews (Nu- menius), the Ruffs, Godwits, Turnstones, Avocet, and many others which need no particular notice. Fam. 4. Pressirostres. — The members of this family are characterised by the moderate length of the bill, which is seldom longer than the head, and has a compressed tip. The legs are long, but the toes are short, and are almost always partially connected together at their bases by membrane. The hallux is short, and is often wanting. In this section are two very distinct sub-families, the Charadriidce. or Plovers and the Otidce or Bustards. In the former of these the legs are long and slender, the toes are united at their bases by a small membrane, and the hind-toe is very small and raised above the ground, or is entirely wanting. In this group are the true Plovers and Lapwings, the Oyster-catcher (Hamatopus\ and the Thick-knee (CEdicnemits). In the Otidce, or Bustards, the legs are long and the toes are short and furnished with stout claws. The hinder toe or hallux is entirely wanting; and these birds are chiefly interesting from the affinities which they exhibit to the Rasores on the one hand, and to the Cursores (Ostrich, &c.) on the other. The wings, however, are of ample size, and the tail is long, the reverse being the case in the Cursores. The Bustards are entirely confined to the Old World, and two species were formerly not uncommon in Britain. CURSORES AND RASORES. 451 CHAPTER LXVIII. CURSORES AND RASORES. ORDER III. CURSORES. — The third order of Birds is that 01 the Cursores, or Runners, comprising the Ostriches, Rheas, Cassowaries, Emeus, and the singular Apteryx of New Zealand. In many respects the Cursores are to be looked upon as an artificial assemblage; but in the meanwhile it will be most convenient to consider them as forming a distinct division. The Cursores are characterised by the rudimentary condition of the wings, which are so short as to be useless for flight, and by the compensating length and strength of the legs. In accordance with this condition of the limbs, many of the bones retain their marrow, and the sternum (fig. 175, B) is destitute of the prominent ridge or keel, to which the great pectoral muscles are attached (hence the name of Raiita, applied by Huxley to the order). In the Ostrich the pubic bones of the pelvis unite to form a symphysis pubis, as they do in no other bird, and in all the pelvic arch possesses unusual strength and stability. The legs are extremely robust and powerful, and the hind-toe is entirely wanting, except in the Apteryx, in which it is rudimentary. The anterior toes are two or three in number, and are provided with strong blunt claws or nails. The plumage presents the remarkable peculiarity that the barbs of the feathers, instead of being connected to one another by hooked barbules, as is usually the case, are remote and disconnected from one another, presenting some resemblance to hairs. Fig. 175.— Cursores. A, Foot of the Ostrich (Struthio camelus) ; B, Sternum of the Emeu (Dromaius Novce-Hollandice), The order Cursores may be divided into the two families of the Struthionidce and the Apterygidce, — the former characterised by the absence of the hallux, and comprising the Ostrich, 452 MANUAL OF ZOOLOGY. Rhea, Emeu, and Cassowary, with several extinct forms ; the latter comprising only the Apteryx of New Zealand, and char- acterised by the possession of a rudimentary hallux. The African Ostrich (Struthio camelus] occurs in the desert plains of Africa and Arabia, and is the largest of all living birds, attaining a height of from six to eight feet. The head and neck are nearly naked, and the quill-feathers of the wings and tail have their barbs wholly disconnected, constituting the ostrich-plumes of commerce. The legs are extremely strong, and are terminated by two toes only (fig. 175, A), these con- sisting respectively of four and five phalanges, showing that it is the hallux and the innermost toe which are wanting. The Ostriches run with extraordinary speed, and can outstrip the fastest horse. They are polygamous, each male consorting with several 'females, and they generally keep together in larger or smaller flocks. The eggs are of great size, averaging three pounds each in weight, and the hens lay their eggs in the same nest, this being nothing more than a hole scratched in the sand. The eggs appear to be hatched mainly by the exertions of both parents, relieving each other in the task of incubation, but also partly by the heat of the sun. The American Ostriches or Rheas are much smaller than the African Ostrich, and have the head feathered, whilst the feet are furnished with three toes each. They inhabit the great plains of South America, and are polygamous. The Emeu (Dromaius Nova-Hollandice) is exclusively found in the Australian continent, and nearly equals the African Ostrich in size, attaining a height of from five to seven feet. The feet are furnished with three toes each, and the head is feathered. The throat, however, is naked, and the general plumage resembles long hairs, the feathers hanging down on both sides of the body from & central line or parting which runs down the middle of the back. The Emeus are mono- gamous, and the eggs are dark green in colour. The last of the Struthionida is the Cassowary (Casuarius galeattts), which inhabits the Moluccan Islands and New Guinea, and was first brought alive to Europe by the Dutch. It stands about five feet in height, and possesses a singular horny crest upon its head. The head and neck are naked, and the feet have three toes each. The general plumage is black, and the feathers more or less closely resemble hairs. The second family of the Cursorial birds is that of the Apterygidce, comprising only the singular Apteryx of New Zealand. The beak in the Apteryx is long, slender, and slightly curved, the tip being obtuse, and the nostrils placed RASORES. 453 at the extremity of the upper mandible. The legs are com- paratively short, and there is a rudimentary hind-toe or hallux, forming a kind of spur, furnished with a claw. The wings are entirely rudimentary, and are quite concealed by the feathers, each terminating in a sharp claw. The feathers are long and narrow, and the tail is short and inconspicuous. The Apteryx is wholly confined to New Zealand, and is nocturnal in its habits, living upon insects and worms. Besides the above-mentioned living forms, the order Cursores comprises several gigantic extinct forms, which will be treated of when describing the geological distribution of Birds as a class. ORDER IV. RASORES. — The fourth order of Birds is that of the Rasores, or Scratchers, often spoken of collectively as the " Gallinaceous " birds, from the old name of " Gallinae," given to the order by Linnaeus. The Rasores are characterised by the convex, vaulted upper mandible, having the nostrils pierced in a membranous space at its base. The nostrils are covered by a cartilaginous scale. The legs are strong and robust, mostly covered with feathers as far as the joint between the tibia and tarso-metatarsus. There are four toes, three in front and one behind, the latter being short, and placed at a higher level than the other toes. All the toes terminate in strong blunt claws suitable for scratching (fig. 176, A). The food of the Scratchers or Gallinaceous birds consists chiefly of hard grains and seeds, and in accordance with this they have a ca- pacious crop and an extremely strong and muscular gizzard. They mostly nidificate, or build their nests, upon the ground, and the more typical members of the order are polygamous. The males take no part in either nidification or incubation, and the young are generally " precocious," being able to run about and provide themselves with food from the moment they quit the egg. The young of the Pigeons and Doves, however, are brought forth in a comparatively helpless condition. The wings in the majority of the Rasores are more or less weak, and the flight is feeble and accompanied with a whirring sound. Many of the Pigeons, however, are capable of very powerful and sustained flight. The order Rasores is divided into two sub-orders, called re- spectively the Gallinacei and the Columbacei, or sometimes, from the charactets of the sounds which they utter, the Clama- tores and the Gemitores. Sub -order i. Gallinacei or Clamatores. — This sub -order comprises the typical members of the order Rasores, such as the common Fowls, Turkeys, Partridge, Grouse, Pea-fowl, and 454 MANUAL OF ZOOLOGY. a number of allied forms. Its characters are therefore those of the order itself, but it is especially distinguished from the Columbacd by being less fully adapted for flight. The body is B ^sss&r^ A Fig. 176.— Rasores. A, Foot of Fowl (Callus Bankiva); B, Head of Guinea-fowl. much heavier comparatively speaking, the legs and feet are stronger, and the wings shorter and less powerful. On the whole, therefore, these birds are worse fliers than the Columbacei, and are better adapted for living upon the ground. The back of the tarsus, too, is usually furnished in the males with a spur (calcar\ which is used as an offensive weapon, and has sometimes been looked upon as a rudimentary toe. Lastly, the Gallinacei are all polygamous, and the males are usually much more brilliantly coloured than the females, this being an adaptive modification of the plumage to meet this peculiarity in their mode of life. The two most important families of the Gallinacei are the Tetraonida and the Phasianidtz. The Tetraonida, or Grouse family, comprises the Capercailzie (Tftrao urogallus), the Blackcock (Tetrao tetrix), the common or Red Grouse (Lagopus Scoticus), the Ptarmigan (Lagopus vulgaris), the Partridges (Perdix), the Quails (Cotttrnix), and many other allied forms. The PhasianidcR or Pheasant family, comprises the Turkeys and Guinea-fowl (Meleagrincz), the common Pheasant (Phasi- anus Colchicus), the Golden and Silver Pheasants, the common Fowl (Gallus domesticus), and the Pea-fowl (Pavonince). None of these birds — all of which can be domesticated, and most of which are of great value to man — are natives of this country, though they will all breed readily, and thrive even in confine- ment. The domestic Turkey (Meleagris gallopavd] is originally a native of North America, where it still occurs in a wild con- dition, having been brought to Europe about the beginning of the sixteenth century. The Guinea-fowl (Numida Meleagris) is originally an African bird. The common Pheasant (Phasianus Colchicus\ though now regarded as an indigenous bird, truly RASORES. 455 belongs to Asia, and it is asserted that it was really brought to Europe from Colchis by the Greeks; hence its specific name. The common Fowl is certainly not a native of Europe, and it is almost as certainly a native of Asia or of some of the Asiatic islands ; but its exact original habitat is uncertain, as is the species from which the domestic breeds are descended (com- monly said to be the Gallus Bankiva of Java). The introduc- tion of the Fowl into Europe is lost in the mists of antiquity, and it is wholly unknown whence the original stock may have been brought. The Pea - fowl (Pavo) are really natives of Thibet and Hindostan, and were originally brought to Greece by Alexander the Great. They were formerly much esteemed as food, but are now regarded merely from an ornamental point of view. There are many other forms belonging to the Gallinaceous section of the Rasores, but these are in every way the most important. The second sub-order of the Rasores is that of the Columbacei or Gemitores, comprising the Doves and Pigeons, and often raised to the rank of a distinct order under the name of Co- lumba. The Columbacei are separated from the more typical members of the Rasores by being furnished with strong wings, so as to endow them with considerable powers of flight. In place, therefore, of being chiefly ground-birds, they are to a great extent arboreal in their habits, and in accordance with this the feet are slender, and are well adapted for perching. There are four toes, three in front and one behind, and the former are never united towards their bases by a membrane, though the base of the outer toe is sometimes united to that of the middle toe. Lastly, they are all monogamous, and pair for life, in consequence of which fact, and of their being readily susceptible of domestication, they present an enormous number of varieties, often so different from one another that they would certainly be described as distinct species if found in a wild state. It seems certain, however, that all the common domestic breeds of Pigeons, however unlike one another, are really descended from the Rock-pigeon (Columba livia), which occurs wild in many parts of Europe, and has retained its dis- tinguishing peculiarities unaltered for many centuries up to the present day. Finally, the young of the Columbacei are born in a naked and helpless state, whilst those of the Gallinacei are " precocious," and can take care of themselves from the mo- ment of their liberation from the egg. Of the various living birds included in this section, the true Pigeons (Columbida) are too well known to require any de- scription; but the Ground-pigeons (Gouridte) depart to some 456 MANUAL OF ZOOLOGY. extent from this type, being ground-loving birds, more closely allied to the ordinary GallinaceL The only other member of the sub-order which Acquires special notice, is the remarkable extinct bird, the Dodo (Didus ineptus\ which seems certainly to belong here, though its size was gigantic, and some of its characters very anomalous. The Dodo may, properly speak- ing, be said to be extinct, since it no longer occurs in a living state, but it is not extinct in the sense that geologists speak of " fossils " as extinct ; since it has been extirpated by man him- self within quite a recent period — in fact not more than three centuries ago. The Dodo was an inhabitant of the Island ot the Mauritius up to the commencement of the seventeenth cen- tury, and was a large bird, considerably over the size of a swan. All that remains nowadays to prove the existence of the Dodo are two or three old, but apparently faithful, oil-paintings, two heads, a foot, and some feathers, to which a few bones have recently been added. The Dodo owed its extermination to the fact that it was unable to fly. The body must have been extremely weighty, and the wings were rudimentary and com- pletely useless as organs of flight. The legs were short and stout, the feet had four toes each, and the tail was extremely short, carrying, as well as the wings, a tuft of soft plumes. The beak (unlike that of any of the Columbacei except the little Didunculus strigirostris) was strongly arched towards the end, and the upper mandible had a strongly hooked apex, not at all unlike that of a bird of prey. The nearest living ally of the Dodo appears to be the little Didunculus just alluded to, which inhabits the Navigator Islands, and is little bigger than a par- tridge. It is worthy of notice that in the little island of Rodriguez, lying to the east of Mauritius, there existed one large wingless bird, the Solitaire or Pezophaps, which has likewise become ex- tinct during the human period. Other cases in which wingless birds have been, or are being, exterminated by man, lead us to the belief that the absence of wings is not compatible with the coexistence of birds and human beings. In other words, the sole protection possessed by birds against the destructive propensities of man is to be found in their power of flight. SCANSORES AND INSESSORES. 457 CHAPTER LXIX. SCANSORES AND INSESSORES. ORDER V. SCANSORES. — The order of the Scansorial or Climb- ing birds is easily and very shortly denned, having no other distinctive and exclusive peculiarity except the fact that the feet are provided with four toes, of which two are turned back- wards and two forwards. Of the two toes which are directed backwards, one, of course, is the hallux or proper hind-toe, and the other is the outermost of the normal three anterior toes. This arrangement of the toes (fig. 177, A) enables the Scansores to climb with unusual facility. Their powers of flight, on the other hand, are generally only moderate and below the average. Their food consists of insects or fruit. Their nests are usually made in the hollows of old trees, but some of them have the remarkable peculiarity that they build no nests of their own, but deposit their eggs in the nests of other birds. They are all monogamous. The most important families of the Scansores are the Cuckoos (Cuculid&\ the Woodpeckers and Wry-necks (Pidda), the Par- rots (Psittacidce), and the Toucans (Rhamphastida). The Cuculida, or Cuckoos, are chiefly remarkable for the ex- traordinary fact that many of them, instead of nidificating and incubating for themselves, lay their eggs in the nests of other birds. As a rule, only one egg is deposited in each nest, and the young Cuckoo which is hatched from it, is brought up by the foster-parent, generally at the expense of the legitimate off- spring. The large Channel-bill (Scythrops Novce-Hollandice) is said to possess the same curious habit, but many species of this group build nests for themselves in the ordinary manner. The second family of the Scansores is that of the Picidce, and comprises the Woodpeckers and Wry-necks. These birds feed chiefly upon insects, and the tongue is extensible and covered with a viscid secretion, so as to enable them to catch their prey by suddenly darting it out. The next family is that of the Parrots (Psittacida), the largest group of the Scansores, comprising over three hundred species. The bill in the Parrots is large and strong, and the upper mandible is considerably longer than the lower and is hooked at its extremity (fig. 177, B). The bill is used as a kind of third foot in climbing. At the base of the upper mandible is a " cere," in which the nostrils are pierced. The tongue is soft and fleshy. The feet are especially adapted for 458 MANUAL OF ZOOLOGY. climbing, some, however, of the Parrots moving about actively on the ground. The colours of the plumage are generally ex- tremely bright and gaudy; and they live for the most part upon Fig. 177. — A, Foot of Woodpecker (Picus) ; B, Head of Love-bird (Aga^ornis). fruits. The Parrots are divided into numerous sub-families, such as the Cockatoos, the true Parrots and the Parrakeets. They are all natives of hot climates, abounding especially in tropical America and in the forests of Australia. The true Macaws (Araince) are exclusively American ; and the true Parrakeets, Pezoporincz, are exclusively confined to the eastern hemisphere, being especially characteristic of Australia. In the last family of the Scansores are the Toucans (Rham- phastida), characterised by having a bill which is always very large, longer than the head, and sometimes of comparatively gigantic size. The mandibles are, however, to a very great extent hollowed out into air-cells, so that the weight of the bill is much less than would be anticipated from its size. The Toucans live chiefly upon fruits, and are all confined to the hotter regions of South America, frequenting the forests in con- siderable flocks. ORDER VI. INSESSORES. — The sixth order of Birds is that of the Insessores, or Perchers — often spoken of as the Passeres, or " Passerine " Birds. They are defined by Owen as follows : — " Legs slender, short, with three toes before and one behind, the two external toes united by a very short membrane " (fig. 178, A, B). " The Perchers form the largest and by far the most numer- ous order of birds, but are the least easily recognisable by dis- tinctive characters common to the whole group. Their feet, being more especially adapted to the delicate labours of nidi- fication, have neither the webbed structure of those of the Swimmers, nor the robust strength and destructive talons which INSESSORES. 459 characterise the feet of the "Birds of Rapine, nor yet the ex- tended toes which enable the Wader to walk safely over marshy soils and tread lightly on the floating leaves of aquatic plants ; but the toes are slender, flexible, and moderately elon- gated, with long, pointed and slightly-curved claws. " The Perchers in general have the females smaller and less brilliantly coloured than the males ; they always live in pairs, build in trees, and display the greatest art in the construction of their nests. The young are excluded in a blind and naked state, and wholly dependent for subsistence during a certain period on parental care. The brain arrives in this order at its greatest proportionate size ; the organ of voice here attains its greatest complexity, and all the characteristics of the bird, as power of flight, melody of voice, and beauty of plumage, are enjoyed in the highest perfection by one or other of the groups of this extensive and varied order." The structure of the feet, then, gives the definition of the order, but the minor subdivisions are founded on the nature Fig. 178.— Insessores. A, Foot of Yellow Wagtail ; B, Foot of Water-ousel ; C, Conirostral beak (Hawfinch) ; D, Dentirostral beak (Shrike) ; E, Tenuirostral beak (Humming-bird) ; F, Fissirostral beak (Swift). of the beak ; this organ varying in form according to the nature of the food, " which may be small or young birds, carrion, 460 MANUAL OF ZOOLOGY. insects, fruit, seeds, vegetable juices, or of a mixed kind " (Owen). In accordance with the form of the beak, the Insessores have been divided into four great sections or sub-orders, known as the Conirostres, Dentirostres, Tenuirostres, and Fissirostres. Sub-order i. Conirostres. — In this section of the Insessores the beak is strong and on the whole conical, broad at the base and tapering with considerable rapidity to the apex (fig. 178, C). The upper mandible is not markedly toothed at its lower margin. Good examples of the Conirostral type of beak are to be found in the common Sparrow, Hawfinch, or Bullfinch. The greater number of the Conirostres are omnivorous ; the re- mainder are granivorous, or feed on seeds and grains. The sub-order includes the families of the Horn-bills (Buceridcz\ the Starlings (Sturnida), the Crows (Corvida), the Cross-bills (Loxiadce), and the Finches and Larks (Fringillidcz). In the Horn-bills the conirostral shape of the beak is masked, partly by its being of very great size, and partly by the fact that above the upper mandible is placed a hollow appendage like a kind of helmet. Both the beak and the appendage above it are rendered light by the presence of numerous air- cells. The Horn-bills are exclusively confined to the warm countries of the eastern hemisphere, and are the largest of all the Insessorial birds, sometimes attaining the size of a goose. They live on fruits, and make their nests in the holes of trees. The family of the Corvidcz, or Crows, is an extremely exten- sive one, and includes a large number of very dissimilar look- ing birds, all characterised by their long, strong, and com- pressed beaks, the tip of the upper mandible being slightly hooked and more or less notched. In this family are the Jays (Garrulina)\ the true Crows or Corvince. (comprising the Rooks, Carrion-crows, Ravens, Jackdaws, Magpie, Chough, &c.), and the Birds of Paradise (Paradiseidce). These last differ considerably from the ordinary Corvidcz, but can hardly be separated as a distinct family. They are amongst the most beautiful of all birds, and are entirely confined to New Guinea and the neighbouring islands. They feed upon insects and fruit, and are largely destroyed for the sake of their feathers. The natives who capture them usually cut off their legs ; hence the notion formerly prevailed that the Birds of Paradise were destitute of these limbs. It is only the males which possess the brilliant plumage, the females being soberly dressed ; and in accordance with this fact, it is stated that the Birds of Para- dise are polygamous, being in this respect an exception to the entire order of the Insessores. INSESSORES. 461 The family of the Starlings (Stiirnidcz) is not separated from that of the Crows by any important characters. Besides our common Starlings, it includes a number of other more or less singular birds, of which the Bower-birds of Australia are perhaps the most peculiar. These curious birds have the habit of building very elaborate bowers, often very beautifully constructed and of considerable size, in which they amuse themselves and apparently make love to one another. These bowers are wholly independent of their nests, which they construct elsewhere. The last family of the Conirostres is that of the Fringillida, comprising the Finches, Linnets, and Larks. In these birds the bill is stout and conical, with a sharp apex, but not having the upper mandible toothed. The toes are adapted for perch- ing, and are provided with long and curved claws, that of the hinder toe being usually longer than the rest. They are all monogamous, and they build more or less elaborate nests. In this family are the true Finches (Frin- gillina), the Buntings, the Larks, the Tanagers, the Grosbeaks, and many others, but their numbers are so great that any further notice of them is impossible here. The only remaining members of the Conirostres which require notice are the Cross-bills (Loxiadce), which are some- times placed with the Finches, and sometimes considered as a separate order. In these birds the structure of the beak is so peculiar that its Conirostral character is completely masked, and it has been looked upon as a deformity. Both mandibles, namely, cross one another towards the tip, giving the entire bill a most remarkable appearance. In point of fact, however, instead of being a deformity, the bill of the Cross-bills is a beautiful natural adaptation, enabling the bird with the greatest facility to tear in pieces the hard fir-cones, on the seeds of which it feeds. Sub -order .2. Dentirostres. — The birds in this section are characterised by the fact that the upper mandible is provided with a distinct notch in its lower margin near the tip (fig. 178, D). They all feed upon insects. This sub-order includes the Shrikes (Laniidce), the Fly-catchers (Muscicapid(z\ the Thrushes (Merulida\ the Tits (Parma), and the Warblers (Sylviadcs). rte- (Pyrrhula vulgaris), showing the Coni- rostral beak. 462 MANUAL OF ZOOLOGY. The Shrikes are highly predacious birds, which in many respects make a close approach to the true Birds of Prey. They feed, however, mostly upon worms and insects, and only occasionally destroy small birds or mice. The great family of the Thrushes (Merulidcs) comprises not only the true Thrushes, Field-fares, and Blackbirds, but a number of exotic forms, of which the most familiar are the Orioles, so well known for their brilliant plumage and their beautifully-constructed nests. In the Sylviada, amongst other forms, are the Wag-tails (Motacillince) and the Pipits (Anthus), the Titmice, Robins, Hedge-sparrow, Stone-chat, Redstarts, and other well-known British birds. The Titmice (Parince) are often placed in the sub-order of the Conirostres. The Nightingale also belongs to this family. Sub-order 3. Tenuirostres. — The members of this sub-order are characterised by the possession of a long and slender beak, gradually tapering to a point (fig. 178, E). The toes are very long and slender, the hind-toe or hallux especially so. Most of the Tenuirostral birds live upon insects, and some of these present a near resemblance in many of their characters to the Dentirostres, but it is asserted that some live partially or wholly on the juices of flowers. The chief families of the Tenuirostres are the Creepers (Certhidce), the Honey-eaters (Meliphagida), the Humming- birds (Trochilidai), the Sun-birds (Promeropidcz), and the Hoopoes ( Upupida), of which only the Creepers and Hum- ming-birds need any further notice. The family Certhida includes several familiar British birds, such as the little brown Creeper (Certhia familiaris], the Nuthatch (Sitta Eurofcea), and the Wrens (Troglodytes). With these are a number of exotic forms, of which the singular Lyre-birds of Australia are the most remarkable. The family of the Trochilidce, or Humming-birds, includes the most fragile and brightly coloured of all the birds, some not weighing more than twenty grains when alive, and many exhibiting the most brilliant play of metallic colours. The Humming-birds are pre-eminently South American, but extend northwards as far even as the southern portions of Canada. The bill (fig. 178, E) is always very long and slender, as are the toes also. The tongue is bifid, and appears to be used either to catch insects within the corollas of flowers, or to suck up the juices of the flowers themselves. Sub-order 4. Fissirostres. — In this sub-order of the Insessores the beak is short but remarkably wide in its gape (fig. 178, F), INSESSORES. 463 and the opening of the bill is fenced in by a number of bristles (vibrissa). This arrangement is in accordance with the habits of the Fissirostres, the typical members of which live upon insects and take their prey upon the wing. The most typical Fissirostral birds, in fact, such as the Swallows and Goat-suckers, fly about with their mouths widely opened ; and the insects which they catch in this way are prevented from escaping partly by the bristles which border the gape, and partly by a viscid saliva which covers the tongue and inside of the mouth. The typical Fissirostres, characterised by this structure of the beak, comprise three families — the Swallows and Martens (Hirimdinidcz), the Swifts (Cypsdidce], and the Goat-suckers (Caprimulgidce). These three families differ in many important respects from one another, but it would be inconvenient to separate them here. The Swifts, especially, are remarkable for the peculiarity that whilst the hallux is present, it is turned forwards along with the three anterior toes. The Goat-suckers, again, hunt their prey by night, and they are provided with the large eyes and thick soft plumage of all nocturnal birds. Besides the above, there remain the two families of the King- fishers and Bee-eaters, which are generally placed amongst the Fissirostres, though in very many respects the arrangement appears to be an unnatural one. These families are charac- terised by their stronger and longer bills, and by having the external toe nearly as long as the middle one, to which it is united nearly as far as the penultimate joint. In consequence of this peculiar conformation of the toes, these families were united by Cuvier into a single group under the name of Syndactyli. The Bee-eaters (Mcropida) live upon insects, chiefly upon various species of bees and wasps ; but the King-fishers live upon small fish, which they capture by dashing into the water. The common King-fisher (Alcedo ispidd) is a somewhat rare native of Britain, and is perhaps the most beautiful of all our truly indigenous species. Some exotic King-fishers are of large size, and one of the most remarkable of them is the Laughing Jackass (Dacelo gigas) of Australia, so called from its extraordinary song, resembling a prolonged hysterical laugh. 464 MANUAL OF ZOOLOGY. CHAPTER LXX. RAPTORES AND SAURUR&. ORDER VII. RAPTORES. — All the members of this order are characterised by the shape of the bill, which is "strong, curved, sharp-edged, and sharp-pointed, often armed with a lateral tooth" (Owen.) The upper mandible is the longest (fig. 1 80, B), and is strongly hooked at the tip. The body is very muscular • the legs are robust, short, with three toes in front and one behind, all armed with long, curved, crooked claws or talons (fig. 1 80, A) ; the wings are commonly pointed, and of considerable size, and the flight is usually rapid and powerful. The Birds of Rapine are monogamous, and the female is larger than the male. They build their nests generally in lofty and inaccessible situations, and rarely lay more than four eggs, from which the young are liberated in a naked and helpless condition. The order Raptor es is divided into two great sections — the Nocturnal Birds of Prey, which hunt by night, and have the eyes directed forwards ; and the Diurnal Raptores, which catch their prey by day, and have the eyes directed laterally. B Fig. 180.— A, Foot of the Peregrine Falcon ; B, Head of Buzzard. The section of the Nocturnal Raptores includes the single family of the Strigidcz, or Owls. In these birds the eyes are large, and are directed forwards. The plumage is exceedingly loose and soft, so that their flight (even when they are of large size) is almost noiseless. The beak is short, strongly hooked, furnished with bristles at its base, and having the nostrils pierced in a membranous " cere" at the base of the upper man- dible. The cranial bones are highly pneumatic, and the head is therefore of large size. The feathers of the face usually form RAPTORES. 465 an incomplete or complete " disc " or circle round each eye (fig. 1 8 1, B), and a circle of plumes is likewise placed round each external meatus auditorius. The legs are short and strong, and are furnished with four toes, all armed with strong crooked talons. The outer toe can be turned backwards, so that the foot has some resemblance to that of the Scansores. The tarso-metatarsus is densely feathered (fig. 181, A), and the plumes sometimes extend to the extremities of the toes. The oesophagus is not dilated into a crop; and the indigestible portions of the food are rejected by regurgitation from the stomach in the form of small pellets. The Owls hunt their prey in the twilight or on moonlight nights, and they live mostly upon field-mice and small birds, though they will also eat insects or frogs. Fig. 181.— A, Foot of tawny Owl (Ulula stridula); B, Head of white Owl (Strix Jlammea). The section of the Diurnal Raptores in eludes the two groups of the Acdpitrince (Falcons, Hawks, and Eagles), and the Vul- turidce, or Vultures. The eyes in this section are much smaller than in the preceding, and are placed laterally ; and the plum- age is not soft. As regards their power of flight, they show a decided advance upon the Nocturnal Birds of Prey. The wings are long and pointed ; the sternal keel and pectoral muscles are greatly developed ; and many of the members of this section exhibit a more rapid power of locomotion than is seen in any other division of the animal kingdom. The bill is long and strong, with a large " cere " at the base of the upper mandible, in which the nostrils are pierced. The tarso-meta- tarsus and toes are usually covered by scales, and are rarely feathered. Lastly, the oesophagus is dilated into a capacious crop. VOL. II. 2 G 466 MANUAL OF ZOOLOGY. In the AccipitrincB or Falconidcz (fig. 180, B) the head and neck are always clothed with feathers, and the eyes are more or less sunk in the head, and provided with a superciliary ridge or eyebrow. It is to a great extent to the presence of this ridge that many of these birds owe their fearless and bold ex- pression. In this family are the Falcons, Hawks, Buzzards, Kites, Harriers, and Eagles, most of which are so well known that any description is unnecessary. In the Vukvridtt (fig. 182) the eyes are destitute of an eye- brow, and the head and neck are frequently naked, or covered only by a short down. In this family are the Bearded Vul- tures, the true Vultures, and the Condor. Fig. 182. — Head of Vulture (Neophron, percnopterus). The Bearded Vulture, or Lammergeyer (Gypsaetus barbatus), is the largest of European birds, measuring from nine to ten feet from the tip of one wing to that of the other. This power- ful and rapacious bird inhabits the mountain-ranges of the south of Europe and the west of Asia, and feeds chiefly on goats, lambs, and deer, which it kills by precipitating down steep declivities. It is distinguished from the true Vultures by the fact that the head and neck are feathered. The true Vultures have the head, and generally the neck also, naked, or covered with down. They are filthy and dis- gusting birds, which live almost entirely upon carrion, a pecu- liarity which renders them of great service in hot climates. The last member of this section is the gigantic Condor (Sarcorhampus gryphus). This enormous bird has a stretch of SAURUIUE. 46; wing of over fourteen feet, and is usually seen soaring at great heights in the air, rising, it is said, to a height of over twenty thousand feet. It inhabits the lofty mountain-ranges of the Andes, and builds its nest at a height of from ten to fifteen thousand feet. ORDER VIII. SAURUR^:. — This order includes only the extinct bird, the Archtzopteryx macrura, a single specimen of which — and that but a fragmentary one — has been discovered in the Lithographic Slates of Solenhofen (Upper Oolites). This extraordinary bird appears to have been about as big as a Rook ; but it differs from all known birds in having two free claws belonging to the wing, and in having a long lizard-like tail, longer than the body, and composed of separate verte- brae. The tail was destitute of any ploughshare-bone, and each vertebra carried a single pair of quills. The metacarpal bones, also, were not anchylosed together as they are in all other known Birds, living or extinct. Fig. 183. — ArcJuzopteryx macrura, showing tail and tail-feathers, with detached bones. CHAPTER LXXI. DISTRIBUTION OF AVES IN TIME. As regards the geological distribution of Birds, there are many reasons why we should be cautious in reasoning upon merely negative evidence, and more than ordinarily careful not 468 MANUAL OF ZOOLOGY. to infer the non-existence of birds during any particular geolo- gical epoch, simply because we can find no positive evidence for their presence. As Sir Charles Lyell has well remarked, " the powers of flight possessed by most birds would insure them against perishing by numerous casualties to which quad- rupeds are exposed during floods;" and, "if they chance to be drowned, or to die when swimming on water, it will scarcely ever happen that they will be submerged so as to become pre- served in sedimentary deposits," since, from the lightness of the bones, the carcase would remain long afloat, and would be liable to be devoured by predacious animals. As, with a few utterly trivial exceptions, all the deposits in which fossils are found have been laid down in water, and more especially as they are for the most part marine, these considerations put forward by Sir Charles Lyell afford obvious ground against the anticipation that the remains of birds should be either of frequent occurrence or of a perfect character in any of the fossiliferous rocks. In accordance with these considerations, as a matter of fact, most of the known remains of birds are either fragmentary or belong to forms which were organised to live a terrestrial life, and were not organised for flig;ht. The earliest remains which have been generally referred to birds are in the form of footprints impressed upon certain sand- stones in the valley of the Connecticut River in the United States. These sandstones are almost certainly Triassic, and if the ornithic character of these footprints be admitted, then Birds date their existence from the commencement of the Mesozoic period, and, for anything we know to the contrary, may have existed during the Palaeozoic epoch. The evidence as to the ornithic character of the footprints in the American Trias is as follows : — Firstly, The tracks are, beyond all question, those of a biped — that is to say, of an animal which walked upon two legs. No living animals walk habitually upon two legs except Man and Birds, and therefore there is a prim A fade presumption that the authors of these prints were birds. Secondly, The impressions are mostly tridactylous — that is to say, formed by an animal with three toes on each foot, as is the case in many Waders and most Cursorial birds. Thirdly, The impressions of the toes show the same numeri- cal progression in the number of phalanges as exists in living birds — that is to say, the innermost of the anterior toes has three phalanges, the middle one has four, and the outermost toe has five phalanges. Taking this evidence collectively, it would have seemed, till DISTRIBUTION OF AVES IN TIME. 469 lately, tolerably certain that these impressions were formed by Birds. We must not, however, lose sight of the possibility that these impressions may have been formed by Reptiles more bird-like in their characters than any of the living forms with which we are acquainted. The recent researches of Huxley, Cope, and others, go to show that the Dinosaurian Reptiles possessed the power of walking temporarily or per- manently on the hind-legs, and many curious affinities to the true Birds have been pointed out. It is therefore by no means impossible that these footprints of the Connecticut valley are truly Reptilian. The size and other characters of the above-mentioned im pressions vary much, and they have certainly been produced by several different animals. In the largest hitherto discov- ered, each footprint is twenty-two inches long, and twelve inches wide, showing that the feet were four times as large as those of the African Ostrich. The animal, therefore, which produced these impressions — whether Avian or Reptilian — must have been of gigantic size. The first unmistakable remains of a bird have been found in the Solenhofen Slates of Bavaria, of the age of the Upper Oolites. A single unique specimen, consisting of bones and feathers, but unfortunately without the skull, is all that has hitherto been discovered ; and it has been named the Archa- opteryx macrura. The characters of this singular and aberrant bird, which alone constitutes the order Saururce, have been already given, and need not be repeated here. Other doubtful remains of birds have been alleged to occur in the Mesozoic series, but many of these certainly belong in reality to Pterodactyles. In the Tertiary Rocks, however, there are, comparatively speaking, many remains of birds. In the Eocene Rocks of France has been found a large bird, as big as an Ostrich, the so-called Gastornis Parisiensis ; and in England, in the same formation, we have a small Vulture (Lithornis vulturinus), and a King-fisher (Halcyornis toliapicus). In the Eocene of Claris in Switzerland occurs, also, the oldest known Insessorial or Passerine bird, the Protornis Glarisiensis, which was about as big as a lark. Numerous remains of birds have likewise been found in the Miocene and Pliocene deposits. With the exception, how- ever, of the Mesozoic Archceopteryx, by far the most remark- able remains of birds have been found in the Post-tertiary or Pleistocene deposits. All the remains now alluded to are those of gigantic wingless birds ; and it is worthy of notice 4/0 MANUAL OF ZOOLOGY. that they are exclusively found in regions now tenanted by smaller wingless birds, whilst there is reason to believe that some of them have been in existence during the human period. Most of the remains in question have been found in New Zealand, where there have been obtained the bones of several species of large wingless birds, referred by Owen to the genera Dinornis, Palapteryx, and Aptornis. The Dinornis giganteus must have been one of the most -gigantic of the whole class of birds, the tibia measuring upwards of a yard in length, and the skeleton indicating a bird which stood at least ten feet in height. In another species, the Dinornis elephantoptis, the " framework of the skeleton is the most massive of any in the whole class of birds," and "the toe-bones almost rival those of the Elephant" (Owen). The feet were furnished with three anterior toes, and are of interest as presenting us with an un- doubted bird big enough to produce the largest of the foot- prints of the Triassic Sandstones of Connecticut. There is reason to believe from the traditions of the Maories that the Dinornis was living at no very remote period, and that it has been exterminated by man. In Madagascar bones have been discovered of a bird as large or larger than the Dinornis giganteus, which has been described under the name of the sEpiornis maximus. With the bones have been found eggs measuring from thirteen to fourteen inches in diameter, and computed to be as big as three ostrich-eggs, or one hundred and forty-eight hens' eggs. Unlike New Zealand, where there is the Apteryx, Madagascar itself has no living wingless birds; but in the neighbouring island of Mauritius the Dodo has been exterminated less than three hundred years ago ; and the little island of Rodriguez, in the same geographical province, has in a similar period lost the wingless Solitaire (Pezophaps). MAMMALIA. 4/1 DIVISION III. MAMMALIA. CHAPTER LXXII. GENERAL CHARACTERS OF THE MAMMALIA. THE last and highest class of the Vertebrata, that of the Mam- malia, may be shortly defined as including Vertebrate animals in which some part or other of the integument is always provided with hairs at some time of life ; and the young are nourished, for a longer or shorter time, by means of a special fluid — the milk — secreted by special glands — the mammary glands. These two characters are of themselves sufficient broadly to separate the Mammals from all other classes of the Vertebrate sub-king- dom. In addition, however, to these two leading peculiarities, the Mammals exhibit the following other characters of scarcely less importance : — 1. The skull articulates with the vertebral column by means of a double articulation, the occipital bone carrying two con- dyles, in place of the single condyle of the Reptiles and Birds. 2. The lower jaw or mandible consists of two halves or rami, united anteriorly by a symphysis, but not necessarily anchylosed ; but these are each composed of a single piece, instead of being complex and consisting of several pieces, as in the Reptiles and Birds. Further, the lower jaw always articulates directly with the squamosal element of the skull, and is never united to an os quadra turn, as in the Sauropsida. 3. The two hemispheres of the cerebral mass, or brain proper, are united together by a more or less extensively developed " corpus callosum " or commissure. 4. The heart consists — as in Birds — of four cavities or chambers, two auricles and two ventricles. The right and left sides of the heart are completely separated from one another, and there is no communication between the pulmonary and systemic circulations. The red blood-corpuscles are non- nucleated, and, with the exception of the Camelida, they are circular biconcave discs. There is only one aorta — the left — which turns over the left bronchus, and not over the right, as it does in Birds. 472 MANUAL OF ZOOLOGY. 5. The cavities of the thorax and abdomen are completely separated from one another by a muscular partition — the dia- phragm or midriff. 6. The respiratory organs are in the form of two lungs placed in the thorax, but none of the bronchi end in air-recep- tacles, distributed through the body, as in Birds. 7. The embryo mammal is invariably enveloped in an am- nion, and an allantois is never wanting. The allantois, how- ever, either disappears at an early period of life, or it develops the structure known as the " placenta." The placenta is a vascular organ which serves as a means of communication between the parent and the foetus, but it will be noticed more particularly hereafter. 8. In no Mammal do the visceral arches and clefts of the embryo ever carry branchiae, as they do in the Fishes and Amphibians. These are the essential characters which distinguish the Mammalia as a class, but it will be necessary to consider these, and some other points, in a more detailed manner. In the first place, with regard to the osteology of the Mam- mals, the following points should be noticed : — With the exception of the Whales and Dolphins (Cetacea\ and the Dugongs and Manatees (Sirenia), the vertebral column is divisible into the same regions as in man — namely, into a cervical, dorsal, lumbar, sacral, and caudal or coccygeal region (see fig. 1 1 8). In the Cetacea and Sirenia the dorsal region of the spine is followed by a number of vertebrae which com- pose the hinder extremity of the body, but which cannot be separated into lumbar, sacral, and caudal vertebrae. In spite of the great difference which is observable in the length of the neck in different Mammals, the number of vertebrae in the cervical region is extraordinarily constant, being almost invariably seven, as in man. In this respect there is no difference between the Whale and the Giraffe. The only exceptions to this law are the Manatus australis, one of the Sea-cows, which has usually six cervical ver- tebrae, and the three-toed Sloth (Bradypus tridactyhis], which is commonly regarded as possessing nine, though competent anatomists would refer the posterior two of these to the dorsal region. The dorsal vertebrae are mostly thirteen in number, but they vary from ten to twenty-four. In Man there are twelve, in one of the Armadillos only ten, and in the three-fingered Sloth the maximum is attained. The lumbar vertebrae are usually six or seven in number, rarely fewer than four. In Man they are CHARACTERS OF MAMMALIA. 473 five in number, and they are reduced to two in the two-toed Sloth, one of the Ant-eaters, and the Duck-mole. The first vertebra, or atlas, always bears two articular cavi- ties for the reception of the two condyles of the occipital bone, and the second vertebra, or axis, usually has an " odontoid " process on which the head rotates. In the true Whales, how- ever, in which the cervical vertebrae are anchylosed together to a greater or less extent, and the neck is immovable, the odontoid process is also wanting. In almost all Mammals the spinous processes of the dorsal vertebrae are very largely developed for the attachment of the structure which is known as the ligamentum nuchtz. This is a great band of elastic fibrous tissue, which is attached in front to the occipital bone and spinous processes of the cervical vertebrae, and which relieves the muscles of the task of support- ing the head, in those Mammals which progress with the body in a horizontal position. The development of the ligamentum nucha is consequently, as a rule, proportionate to the size of the head and the length of the neck. In Whales no such apparatus is necessary, owing to the fixation of the cervical vertebrae by anchylosis ; and in Man, who walks erect, the ligamentum nucha can hardly be said to exist as a distinct structure, being merely represented by a band of fascia. The number of lumbar and sacral vertebrae, as we have seen, varies in different mammals ; but ordinarily some of the verte- brae are anchylosed into a single bone, and have the iliac bones abutting against them, thus constituting the " sacrum " of human anatomists. In the Cetacea and Sirenia, in which the hind-limbs are wanting, and the pelvis rudimentary, there is no "sacrum." The thoracic cavity or chest in Mammals is always enclosed by a series of ribs, the number of which varies with that of the dorsal vertebrae. In most cases each rib articulates by its head with the bodies of two vertebrae, and by its tubercle with the transverse process of one of these vertebrae (the lower one). In the Monotremata (e. g., the Duck-mole), the ribs articulate with the body of the vertebra only, and in the Whales the hindermost of the ribs, or all of them, articulate with the trans- verse processes only, and not with the centra at all. There are usually no bony pieces uniting the ribs with the sternum or breast-bone in front, as in Birds ; but the so-called " sternal ribs " of Aves are represented by the " costal carti- lages " of the Mammals. In some cases, however, the carti- lages of the ribs do become ossified and constitute sternal ribs. Sometimes, as in the Armadillos, there is a joint between the 4/4 MANUAL OF ZOOLOGY. vertebral rib and costal cartilage. More rarely, as in the Monotremes, an intermediate piece is found between the verte- bral and costal portions of the rib. Only the anterior ribs reach the sternum, and these are called the " true " ribs ; the posterior ribs, which fall short of the breast-bone, being known as the " false " ribs. The sternum or breast-bone is formed of several pieces placed one behind the other, but usually anchylosed together to form a single bone. It is placed upon the ventral surface of the body, and is united with the vertebral column by the ribs and their cartilages. It is generally a long and narrow bone, but in the Cetacea it is broad. It is only in some burrowing ani- mals (such as the Moles) and in the true flying Mammals (the Bats), that the sternum is provided with any ridge or keel for the attachment of the pectoral muscles, as it is in Birds. The sternum is primitively composed of three pieces, an anterior piece or prcesternum, a middle piece or mesosternum, and a posterior piece or xiphisternum. The praesternum is the " manubrium sterni " of human anatomy, and is the portion of the sternum which lies in front of the attachment of the second pair of ribs. All the other ribs are connected with the meso- sternum. The xiphisternum is the " xiphoid cartilage " of human anatomy, and it commonly remains throughout life more or less unossified. In the Monotremes there is a T-- shaped bone above or in front of the praesternum, but this is probably to be regarded as belonging to the shoulder-girdle, and as representing the " episternum " or " interclavicle " of the Reptiles. The normal number of limbs in the Mammalia is four, two anterior and two posterior ; and hence they are often spoken of as " quadrupeds," though all the limbs are not universally present, and other animals have four limbs as well. The ante- rior limbs are not known to be wanting in any Mammal, but the posterior limbs are absent in the Cetacea and Sirenia. As regards the structure of the anterior limb, the chief points to be noticed concern the means by which it is connected with the trunk. The scapula or shoulder-blade is never absent, and it is in the form of a broad flat bone, applied to the outer aspect of the ribs, and much more developed than in the Birds. The coracoid bone, which forms such a marked feature in the scapular arch of Aves, is fused with the scapula, and only arti- culates with the sternum in the Duck-mole and Echidna (Mono- trematd). In all other Mammals the coracoid forms merely a process of the scapula, and does not reach the top of the breast- bone. The collar-bones or clavicles never unite in any Mam- CHARACTERS OF MAMMALIA. 475 mal to form a "furculum," as in Birds ; but in the Monotremes they unite with an " inter-clavicle " placed in front of the ster- num. The clavicles, in point of fact, are not present in a well- developed form in any Mammals except in those which use the anterior limbs in flight, in digging, or in prehension. The Cetacea, the Hoofed Quadrupeds ( Ungulata), and some of the Edentata, have no clavicles. Most of the Carnivora and some Rodents possess a clavicle, but this is imperfect, and does not articulate with the top of the sternum. The Insectivorous Mammals, many of the Rodents, the Bats, and all the Quadru- mana, have (with man) a perfect clavicle articulating with the anterior end of the sternum. The humerus, or long bone of the upper arm (braclmuri), is never wanting, but is extremely short in the Whales, in which the anterior limbs are converted into swimming-paddles. In many Mammals, as in the Monkeys, and Felidcz (constituting the most typical group of the Carnivora), the median nerve and brachial or ulnar artery are protected on their way down the arm by a canal placed a little above the elbow, and formed by a process — the " supra-condyloid " process — which is some- times present in man as an abnormality. In the fore-arm of all Mammals the ulna and radius are re- cognisable, but they are not necessarily distinct; and the radius, as being the bone which mainly supports the hand, is the only one which is always Veil developed, the ulna being often rudi- mentary. In the Cetacea the ulna and radius are anchylosed together; and in most of the Hoofed Quadrupeds they are anchylosed towards their distal extremities. In the flying Mammals or Bats alone is the ulna ever altogether absent. The fore-arm attains its greatest perfection in man, in whom the radius can rotate upon the ulna, so as to allow the back of the hand to be placed upwards or downwards, these movements being known respectively as " pronation " and " supination." In the Monkeys only is there any approach to this power of rotation. The fore-arm is succeeded by the small bones which com- pose the wrist or " carpus." These are eight in number in man, but vary in different Mammals from five to eleven. The metacarpus in man and in most Mammals consists of five cylindrical bones, articulating proximally with the carpus, and distally with the phalanges of the fingers. The most re- markable modification of this normal state of things occurs in the Ruminants and in the Horse. In the Ruminants, in which the foot is cleft, and consists of two toes only, there are two metacarpal bones in the embryo ; but these are anchylosed to- MANUAL OF ZOOLOGY. gather in the adult, and form a single mass which is known as the " canon-bone " (fig. 184, ca). In the Horse, in which the foot consists of no more than a single digit, there is only a single metacarpal bone, on each side of which are two little bony spines — the so-called "splint- bones" — which are attached superiorly to the carpus. These are to be regarded as rudimen- tary metacarpals ; but by Cuvier they were looked upon as im- perfect fingers. In most of the other Ungulates there are at least three metacarpals, and in the Elephants there are five. The normal number of digits is five, but they vary from one to five. The middle finger is the longest and most persistent of the digits of the fore-limb ; and in the Horse it is the only one which is left (fig. 184, A). The thumb is very frequently absent. In the Ruminants there are only two fingers which are functionally useful, these carry- ing the hoofs. In all Ruminants, however, there are two rudi- mentary and functionally use- Fig. 184.— A, Fore-leg'of the Horse: r leSS digits in addition. §$&£Z$&%^£y& Normally each digit has three pastern;" 3 Second phalanx or "small phalanges, CXCCpt the thumb, C"?W™K?l°»^ which has only two. In the Radius; c Carpus; ca Canon-bone ; * Whales and Dolphins (CetdCed), Supplementary toe. ^ swimming-paddles, very like those of the Ichthyosaurus and Plesiosaurus, the phalanges are considerably increased in number as they are in those Reptiles. In all the Mammalia, too, except the Cetacea, it is the rule that the terminal phalanx in each digit should carry a nail, claw, or hoof. The power of opposing the thumb to the other digits of the hand is found only in Man, and in a considerable number of the Quadrumana, but never so perfectly developed as in Man. In Man only does this power attain its full perfection, and it constitutes one of the most striking of the merely anatomical peculiarities by which Man is separated from the Monkeys. CHARACTERS OF MAMMALIA. 477 As, however, this feature is purely adaptive, and is really to be regarded as of extremely small physiological value, we ought to learn from this that the difference between man and the Quadrumana is to be sought in the mental powers of each, and not in any merely structural character. Whilst the anterior limbs are never absent in any Mammal, the posterior limbs are occasionally wholly wanting, as in the Cetacea and Sirenia. Generally speaking, however, the poste- rior limbs are present, and the pelvic arch has much the same structure as in man. The two halves of the pelvis — the ossa innominata — consist each of three pieces in the embryo — viz., the ilium, ischium, and pubes, which meet to form the cup- shaped cavity known as the " acetabulum," with which the head of the thigh-bone articulates. In the adult Mammal these three bones are anchylosed together, and the two ossa innominata unite in front by means of a symphysis pubis, con- stituted either by a cartilaginous union (synchondrosis), or by merely ligamentous attachment. In some Mammals, however, such as the Mole, and many of the Bats, the pubic bones re- main disunited during life. As a rule, also, the ossa innomin- ata are firmly united with the vertebral column. In the Ceta- ceans, in which the hind-limbs are wanting, and there is no sacrum, the innominate bones are rudimentary, and are not attached in any way to the spine. The only other bones which are ever connected with the pelvis are two small bones which are directed upwards from the brim of the pelvic cavity in Marsupials and Monotremes. These are the so-called " Marsupial bones" regarded generally as not forming parts of the skeleton properly so called, but as being ossifications of the internal tendons of the " external oblique " muscles of the abdomen (fig. 187). In those Mammals which possess hind-limbs, the normal composition of the member is of the following parts : — i. A thigh-bone or femur ; 2. Two bones forming the shank, and known as the tibia and fibula ; 3. A number of small bones constituting the ankle or tarsus ; 4. The " root " of the foot, made up of the "metatarsus;" 5. The phalanges of the toes (see fig. 120). The thigh-bone or femur articulates with the pelvis, usually at a very open angle. In Man it is distinguished by being the longest bone of the body, and by having the axis of its shaft nearly parallel to that of the vertebral column. In most Mammals the femur is relatively shorter, and the axis of its shaft deviates considerably from that of the spine, being some- times at right angles, or even at an acute angle. 478 J MANUAL OF ZOOLOGY. Of the bones of the leg proper the tibia corresponds to the radius in the fore-limb, as shown by its carrying the tarsus ; and the fibula is the representative of the ulna. The articula- tion between the tibia and fibula on the one hand, and the femur on the other, constitutes the " knee-joint," which is usu- ally defended in front by the " knee-pan " or patella, a large sesamoid bone developed in the tendons of the great extensor muscles of the thigh. The patella is of small size in the Car- nivora, but does not appear to be wanting in any except the Marsupials. In many cases the tibia and fibula are anchylosed towards their distal extremities. In the Horse the fibula has much the same character as in Birds, being a long splint-like bone which only extends about half-way down the tibia. In the Ruminants the reverse of this obtains, the upper half of the fibula being absent, and only the lower half present. The tibia articulates with the tarsus, consisting in man of seven bones, but varying in different Mammals from four to nine. The foot consists normally of five toes connected with the tarsus by means of five metatarsal bones, which closely re- semble the metacarpals. In the Ruminants there are only two metatarsals, and these are anchylosed in the adult, and carry two toes. In the Horse there is only one metatarsal support- ing a single toe. As a rule, the number of digits in the hind- limb or foot is the same as that in the fore-limb or hand ; but this is not always the case. In the Lions, Tigers, Cats, and Dogs, the posterior limb carries only four toes, the innermost toe or hallux being wanting. In the Quadrumana, again, all the five toes are generally present, but the four outer toes are much longer than in Man, and the hallux is shorter than the other toes, and often opposable to them, so that the foot forms a kind of posterior hand. The hallux is also not uncommonly opposable in other cases. The cranial bones are invariably connected with one another by sutures, and in no other examples than the Monotremes are these sutures obliterated in the adult. The differences of opinion which are entertained as to the fundamental structure of the skull are so enormous that it will be best not to attempt here any detailed description of the skull of the Mammalia, more especially as there is as yet no universal agreement even as to the nomenclature to be employed. It is sufficient to re- member that the skull is composed of a series of bony segments, which are usually regarded as modified vertebrae. The occipi- tal bone carries two condyles for articulation with the first cervical vertebra. The lower jaw is composed of two halves CHARACTERS OF MAMMALIA. 479 or rami, which are distinct from another in the embryo, and may or may not be anchylosed together in the adult. How- ever this may be, in no Mammal is the ramus of the lower jaw composed of several pieces, as it is in Birds and Reptiles, nor does it articulate with the skull by the intervention of an os quadratum. On the other hand, each ramus of the lower jaw in the Mammals is composed of only a single piece, and arti- culates with the squamosal element of the skull, or, in other words, with the squamous portion of the temporal bone. Teeth are present in the great majority of Mammals; but they are only present in the embryo of the Whalebone Whales, and are entirely absent in the genera Echidna, Manis, and Myrmecophaga. In the Duck-mole ( Ornithorhynchns) the teeth are horny, and the same was the case in the extinct Rhytina amongst the Sirenia. In all other Mammals the teeth have their ordinary structure of dentine, enamel, and crusta petrosa, these elements being variously disposed in different cases. In no Mammals are the teeth ever anchylosed with the jaw, and in all the teeth are implanted into distinct sockets or alveoli, which, however, are very imperfect in some of the Cetacea. Many Mammals have only a single set of teeth throughout life, and these are termed by Owen "monophyodont." In most cases, however, the first set of teeth — called the " milk" or " deciduous " teeth — is replaced in the course of growth by a second set of " permanent " teeth. The deciduous and per- manent sets of teeth do not necessarily correspond to one another ; but no Mammal has ever more than these two sets. The Mammals with two sets of teeth are called by Owen 11 diphyodont." In Man and in many other Mammals the teeth are divisible into four distinct groups, which differ from one another in position, appearance, and function ; and which are known respectively as the incisors, canines, prcemolars, and molars (fig. 185). "Those teeth which are implanted in the prae- maxillary bones, and in the corresponding part of the lower jaw, are called 'incisors,' whatever be their shape or size. The tooth in the maxillary bone which is situated at or near to the suture with the praemaxillary, is the ' canine/ as is also that tooth in the lower jaw which, in opposing it, passes in front of its crown when the mouth is closed. The other teeth of the first set are the ' deciduous molars ; ' the teeth which displace and succeed them vertically are the * prsemolars ; ' the more posterior teeth, which are not displaced by vertical successors, are the 'molars' properly so called." — (Owen.) The deciduous dentition, therefore, of a diphyodont Mammal 480 MANUAL OF ZOOLOGY. consists of only three kinds of teeth — incisors, canines, and molars. The incisor and canine teeth of the deciduous set are replaced by the teeth which bear the same names in the per- manent set. The deciduous " molars," however, are replaced by the permanent " praemolars," and the " molars " of the per- manent set of teeth are not represented in the deciduous series, only existing once, and not being replaced by suc- cessors. Fig. 185. — Teeth of the right side of the lower jaw of the Chimpanzee (after Owen). * Incisors ; c Canine teeth : pm Prasmolars ; m Molars. All these four kinds of teeth are not necessarily present in all Mammals, and, as will be afterwards seen, the characters of the teeth are amongst the most important of the distinc- tions by which the Mammalian orders are separated from one another. The variations which exist in the number of teeth in different Mammals are usually expressed by a " dental formula," which presents the " dentition" of both jaws in a condensed and easily- recognised form. According to Owen, the typical permanent dentition of a diphyodont Mammal would be expressed by the following formula : — The four kinds of teeth are indicated in such a formula by the letters — incisors /, canines c, praemolars pm, molars m. The numbers in the upper line indicate the teeth in the upper jaw, those in the lower line stand for those in the lower jaw ; and the number of teeth on each side of the jaw is indicated by the short dashes between the figures. CHARACTERS OF MAMMALIA. 481 As regards the digestive system of the Mammalia, salivary glands are present in all except the true Cetacea. The alimen- tary canal has in most cases essentially the same structure as in man ; and the same accessory glands are present — namely, the liver and pancreas. Some very remarkable modifications occur in the structure of the stomach and in the termination of the intestine ; but these will be noticed in speaking of the orders in which they occur. The cavity of the abdomen is always separated from that of the thorax by a complete muscular partition — the diaphragm — as is the case in no other Vertebrate animals. The abdomen contains the greater portion of the alimentary canal, the liver, spleen, pancreas, kidneys, and other organs. The thorax mainly holds the heart and lungs. The heart is contained in a serous bag, the pericardium, and consists (as in Birds) of two auricles and two ventricles. The effete and deoxygenated blood is returned from the tissues by the veins, and is conducted by the two venae cavae to the right side of the heart into the right auricle. From the right auricle it passes into the right ventricle, whence it is propelled through the pulmonary artery to the lungs. Having been submitted to the action of the air, the blood, now arterialised, is carried by the pulmonary veins to the left auricle, and thence into the left ventricle. From the left ventricle the aerated blood is driven through the aorta and systemic vessels to all parts of the body. In Mammals, therefore, as in Birds, the pulmonary and systemic circulations are altogether distinct and separate from one another. The two sides of the heart — except in the foetus and as an abnormality in adults — have no communica- tion with one another except by means of the capillaries. The red blood-corpuscles are never nucleated, and in all except the Camelida (in which they are oval) they are circular and discoid. The lungs of Mammals differ from those of Birds in being freely suspended in the thoracic cavity, the greater part of which they fill, and in being enclosed freely in a serous sac (pleura] which envelops each lung. The lungs are minutely cellular throughout, and the bronchi never open on the sur- face of the lung into a series of air-receptacles communicating with one another, and placed in different parts of the body, as is the case in Birds. There is no "inferior larynx" in any Mammal, and the upper aperture of the true larynx is always protected by an epiglottis. The kidneys in Mammals are situated in the lumbar region, and exhibit a division of their substance into cortical and me- dullary portions. VOL. II. 2 H 482 MANUAL OF ZOOLOGY. There are two ovaries in all Mammals, and the oviducts are known as the " Fallopian tubes." Each oviduct dilates on its way to the surface into a uterine cavity, which opens into the vagina. In the Monotremes and Marsupials this primitive condition is retained throughout life, the uterus remaining double, and opening by two apertures into the cloaca or vagina. In most cases this condition is so far modified in the adult, that the two uteri have coalesced inferiorly, so as to have only a single opening into the vagina, whilst they separate into two horns or " cornua" superiorly. Only in the Monkeys and in Man have the two uteri completely coalesced to form a com- pletely single cavity, into the " fundus" of which the Fallopian tubes open. In male Mammals there are always two testes present. In many Mammals the testes are permanently retained in the abdominal cavity and there is no scrotum. This is the case in the Monotremes, the Elephants, all the Cetacea, and many of the Edentata. Mostly, however, the testes at an early period of life are transferred from the ab- domen to a pouch of integument called the " scrotum." Usually the scrotum is placed beneath the pubic arch and behind the penis, but this position is reversed in the Marsupials. Mammary glands are present in all Mammals, and they are regarded by Huxley as an extreme modification of the cutane- ous sebaceous glands. In the male Mammals the mammary glands are present, but, under all ordinary circumstances, they remain functionally useless and undeveloped. Considerable differences obtain as to the number and position of the mam- mary glands in different cases ; but they are always placed on the inferior surface of the body, and their ducts in the great majority of cases open collectively upon a common elevation — the "teat" or "nipple." In the Monotremata, however, there are no nipples, the ducts of the mammary glands open- ing either into a pouch of the integument (Echidna) or upon a flat surface (Ornithorhynchus). The young Mammal is nourished for a longer or shorter time by the milk secreted by the mammary glands of the mother. In ordinary cases the milk is obtained by voluntary suction on the part of the young animal ; but in the Marsupials the young are at first unable to suck for themselves, and the milk is forced out of the gland by the contractions of a special muscle. The nervous system of Mammals is chiefly remarkable for the great proportionate development of the cerebral mass as compared with the size of the spinal cord. In the higher Mammals, again, the hemispheres of the cerebrum are much CHARACTERS OF MAMMALIA. 483 more largely developed proportionately than the remaining parts of the brain. The brain of the Mammals is chiefly distinguished from that of the lower Vertebrata by the fact that the two hemispheres of the cerebellum are united by a transverse commissure — the pom Varolii — and the hemispheres of the brain are connected by a great commissure — the corpus cal- losum — which is, however, of small size in the lower Mammalia. The senses, as a rule, attain great perfection in the Mam- mals ; and the only sense which appears to be ever entirely wanting is that of vision. In one of the most familiar instances of this last-mentioned fact — namely, in the Mole — it has recently been shown that it is only in the adult that vision is lost, but that the organs of sight are well developed in the young. The sclerotic coat of the eye is never supported by a ring of bony plates as in Birds and many Reptiles. As a rule, in addition to the upper and lower eyelids there is a third perpendicular lid — the membrana nictitans — but this is wanting or quite rudimentary in Man and in the Monkeys. An external ear or concha for collecting the vibrations of sound is usually present, but is wanting in the Cetacea, many of the Seals, and in some other cases. The integument is furnished over a greater or less portion of its surface with the epidermic appendages known as " hairs." These are developed, much as feathers are, upon little eminences or papillae of the derma, but they do not split up in the process of development as feathers do. In the Manis or Scaly Ant-eater the epidermic appendages are in the form of horny scales, and not uncommonly they are developed into long spines, as in the Echidna, Porcupine, and Hedgehog. In the Armadillos, again, the integument has the power of developing plates of. bone over a greater or less extent of its surface. The only apparent exception to the universal presence of hairs in some part or other of the skin of all Mammals is constituted by the Cetacea, some of which are without hairs in the adult state. Some, however, of these (such as the Whales) possess a few bristles in the neighbourhood of the mouth even when fully grown. And the Dolphins, which are totally hair- less when adult, exhibit tufts of hair on the muzzle in the fcetal state. 484 MANUAL OF ZOOLOGY. CHAPTER LXXIII. CLASSIFICATION OF THE MAMMALIA. NUMEROUS classifications of the Mammalia have been pro- posed, and it is a matter of regret that no one has been universally accepted by Zoologists. Here, it will be sufficient to describe briefly the three leading systems upon which the Mammalia have been divided into sub-classes ; whilst the first will be adopted as sufficient for all practical purposes. I. By many writers the class Mammalia is divided into two great primary divisions, the Placentalia or Placental Mammals, and the Implacentalia or Non-placental Mammals, according as the structure known as the "placenta " is present or absent. The placenta, as before said, is a vascular organ developed in the greater number of Mammals, by means of which the blood of the foetus is brought into relation with the blood of the mother. The sub-class Placentalia, in which such a vascular connection between the mother and foetus exists, comprises by far the largest number of the Mammals. The sub-class Implacentalia, in which no such vascular connection exists, comprises only the two orders of the Monotremata and the Marsupialia. II. By Professor Owen the Mammalia are divided into four sub-classes, characterised by the structure of the brain, as follows : — a. Lyencephala, characterised by the fact that the cerebral hemispheres are without folds, and leave the cerebellum, the olfactory lobes, and part of the optic lobes uncovered. The hemispheres are not connected together by a corpus callosum. (Monotremata and Marsupialia.} b. Lissencephala, characterised by the fact that the cerebral hemispheres are smooth or are provided with few folds, and leave the cerebellum and part of the olfactory lobes exposed. A corpus callosum is present. ( Cheiroptera, Insectivora, Rode?itia, Edentata.} c. Gyrencephala, characterised by the fact that the hemispheres of the cerebrum cover the greater part of the cerebellum and the olfactory lobes. A corpus callosum is present, and the surface of the cerebral hemispheres is thrown into numerous convolutions. (Cetacea, Carnivora, Sirenia, Proboscidea, Ungu- lata, Quadrumana.) d. Archencephala, characterised by the fact that the cerebral hemispheres now completely overlap the cerebellum and olfac- DIVISIONS OF MAMMALIA. 485 tory lobes ; the number of convolutions attains its maximum; and there is a corpus callosum. (Man.) This is the primary classification of the Mammalia put forth by Owen, and there can be no question but that in many respects it expresses substantial and important differences. It will not be adopted here, partly because it is somewhat difficult to follow or to apply in practice, and partly because some of the characters upon which it is founded are denied by other eminent naturalists. Thus, in the definition of the sub-class Lyencephala it is stated as one of the essential characters that there is no corpus callosum or commissure between the hemi- spheres of the cerebrum. On the other hand, it is asserted by Flower and Huxley that a corpus callosum does exist in these animals, though it never attains to any high degree of development. III. It was proposed by De Blainville, and the arrangement has been accepted by Huxley and Rolleston, to divide the Mammalia into the following three sub-classes, founded upon the nature of the reproductive organs : — a. Ornithodelphia, characterised by the fact that the uterine enlargements of the oviducts do not coalesce even in their inferior portion to form a common uterine cavity, but open separately as in the Birds and Reptiles. Furthermore, the two uteri open, not into a distinct vagina, but into a cloacal cavity, into which the rectum and ureters also discharge themselves ; so that the condition of parts is very much the same as it is in Birds. This division includes only the Duck-mole (Ornithorhynchus) and the Porcupine Ant-eater (Echidna), forming collectively the single order of the Monotremata. b. Didelphia, characterised by the fact that the uterine dilatations of the oviducts continue distinct throughout life, opening into two distinct vaginae, which in turn open into a urogenital canal, which is distinct from the rectum, though embraced by the same sphincter muscle. This sub-class contains the Marsupialia, such as the Kan- garoos, Opossums, Wombats, &c., most of which are almost entirely confined to Australia. They have many other char- acters in common, which will be spoken of hereafter. III. Monodelphia, characterised by the fact that the uterine enlargements of the oviducts coalesce to a greater or less extent to form a single uterine cavity, which, however, generally shows its true composition by being divided superiorly into two cornua. The uterus opens again into a single vagina, which is always distinct from the rectum. This sub-class 486 MANUAL OF ZOOLOGY. corresponds with the division of the "Placental" Mammals, and includes all the Mammalia except the Monotremes and Marsupials. Before going on to consider the different orders of the Mam- malia in detail, it may be as well very briefly to run over the leading characters by which the various orders are distinguished : Order I. Monotremata, characterised by the fact that the ureters and ducts of the reproductive organs open into a com- mon urogenital canal, which in turn opens, along with the rectum, into a " cloaca." The testes are abdominal, and are not lodged in a scrotum. The mammary glands have no nipples. The young is devoid of a placenta, but the female possesses no marsupial pouch, though the pelvis is furnished with " marsupial bones." In this order are only the Duck- mole and the Echidna. Order II. Marsupialia, characterised by the fact that the uterine dilatations of the oviducts open with the ureters into a urogenital canal, which is distinct from the rectum, though embraced by the same sphincter muscle. The testes are not abdominal, but are lodged in a scrotum which is suspended by a narrow neck in front of the penis. The females are mostly furnished with a marsupial pouch, in which the young are carried for some period after birth. The young are not provided with a placenta, and are born in a very imperfect state of development. Marsupial bones are present. In this order are the Kangaroos, Opossums, Wombats, &c. Order III. Edentata or Bruta, characterised by the univer- sal absence of the median incisors, and the general absence of all the incisors. The canines are usually wanting as well, and sometimes there are no molars either. There is only one set of teeth, and the teeth have neither complete roots nor are furnished with a covering of enamel. The toes are always furnished with claws. Placenta sometimes deciduate, some- times non-deciduate. As examples of this order may be taken the Sloths, Armadillos, and the great Ant-eater. Order IV. Sirenia, comprising the Dugongs and Manatee, characterised by being adapted to an aquatic life. Body fish- like, with a strong horizontal tail-fin. There is no sacrum, and the hind-limbs are invariably wanting, whilst the fore- limbs are converted into swimming-paddles. There are, in the living forms at any rate, two sets of teeth, and the molars have flattened crowns adapted for a vegetable diet. There are two nostrils, and these are placed at the upper part of the snout. There are two mammae, and these are placed on the. chest, and not on the abdomen. DIVISIONS OF MAMMALIA. 487 Order V. Cetacea, comprising the true Whales and Dolphins, characterised by being aquatic Mammals, with a horizontal tail-fin, no sacrum nor hind-limbs, and fore-limbs in the form of swimming-paddles. The nostrils are single or double, and are placed on the top of the head. The mammary glands are two in number, and are placed in the region of the groin. There is never more than one set of teeth, and in many cases the adult is destitute of teeth altogether. Placenta non-deciduate. Order VI. Ungulata or Hoofed Quadrupeds, comprising the whole of the Ruminants, the Horses, and most of the old group of the Pachydermatous Mammals. This order is split up into many important sections, and, as a whole, it is simply characterised by the fact that there are never more than four full-sized toes to each limb, and that the extremities of the toes are furnished with expanded nails, constituting hoofs. There are no clavicles. Placenta non-deciduate. Order VII. Hyracoidea, comprising only the single genus Hyrax, characterised by having no canines, but by having long curved incisors, which grow from permanent pulps, as in the Rodents. There are no clavicles. The front-feet have four toes, and the hind-feet three. The placenta is deciduate and zonary. Order VIII. Proboscidea, comprising no other living Mam- mal except the Elephant, characterised by having no canines, but only molars and incisors, of which the latter grow from permanent pulps, and constitute defensive tusks. There are no clavicles. The feet are five-toed. The nose is prolonged into a proboscis. The mammae are two in number. The placenta is deciduate and zonary. Order IX. Carnivora, comprising all the well-known beasts of prey, such as Lions, Tigers, Dogs, Cats, &c., together with the aquatic Seals and Walruses. They are all characterised by always possessing the three different kinds of teeth — incisors- canines, and molars — the canines being usually of great length, and a greater or less number of the molars having sharp cut, ting edges. The clavicles are always rudimentary, the teats are abdominal, and the placenta is deciduate and zonary. Order X. Rodentia, comprising the Beavers, Rats, Mice, Hares, Rabbits, Squirrels, and others, characterised by the absence of canines and the possession of no more than two incisors in the lower jaw, and usually no more than two in the upper jaw. The incisors are greatly developed, growing from permanent pulps, and continuing to grow during the life of the animal. Placenta deciduate and discoidal. Order XI. Cheiroptera, comprising only the various Bats, 488 MANUAL OF ZOOLOGY. and characterised by the fact that the four outer or ulnar fingers are greatly developed and elongated, and are united together by a leathery flying-membrane or " patagium," which is continued from the hand and arm to the side of the body and hind-limb. By means of this patagium the Bats possess the power of flight. Clavicles are always present. The teeth vary a good deal, but there are always canines. The placenta is deciduate and discoidal. Order XII. Insectivora, comprising the Moles, Shrew-mice, and Hedgehogs, characterised by having the crowns of the molar teeth furnished with sharp and pointed cusps. Well- developed clavicles are present in almost all cases. The pla- centa is deciduate and discoidal. Order XIII. Quadrumana, comprising the Lemurs, Apes, and Monkeys. Dentition usually the same as in man, or with an additional prsemolar on each side of each jaw, or varying a good deal in the lower forms. The series of teeth is uneven and interrupted. The innermost digit of the fore-limb (pollex) is opposable to the other fingers when present, but it may be wanting. The hallux is also opposable to the other toes of the hind-limb, so that the hind-feet constitute prehensile hands. Clavicles are always present. The placenta is deciduate and discoidal. Order XIV. Bimana. — This order includes Man alone. The dental formula is — /*=?; ,1=1; ^2-2. ^3=3 = 32. 2 — 2 I — I 2 — 2 3—3 The teeth are nearly even, and are not interrupted by any interval (diastemd). The pollex or thumb on the fore-limb is opposable to the other digits, but this is not the case with the hallux or great -toe. The attitude of the body in progression is habitually erect. The placenta is deciduate and discoidal. MONOTREMATA. 489 NON-PLACENTAL MAMMALS: CHAPTER LXXIV. MONOTREMATA AND MARSUPIAL1A. ORDER I. MONOTREMATA. — The first and lowest order of the Mammalia is that of the Monotremata, constituting by itself the division Ornithoddphia, and containing only two genera, both belonging to Australia — namely, the Duck-mole (Ornitho- rhynchus] and the Porcupine Ant-eater (Echidna). The order is distinguished by the following characters:— The intestine opens into a " cloaca," which receives also the products of the urinary and generative organs, which discharge themselves into a urogenital canal, the condition of parts being very much the same as in Birds. The jaws are either wholly destitute of teeth (Echidna), or are furnished with horny plates which act as teeth. The pectoral arch has some highly bird-like characters, the most important of these being the extension [of the coracoid bones to the anterior end of the sternum. The females possess no marsupial pouch, but the pelvis is furnished with the so-called " marsupial bones," be- lieved to be ossifications of the internal tendon of the external oblique muscle of the abdomen. The testes of the male are abdominal throughout life, and there is therefore no scrotum, whilst the vasa deferentia open into the cloaca. The corpus callosum is very small, and has been asserted to be altogether wanting. There are no external ears. The mammary glands have no nipples, and their ducts open either into a kind of integumentary pouch (Echidna) or simply on a flat surface (Ornithorhynchus). The young are said to be destitute of a placenta, or, in other words, no vascular connection is estab- lished between the foetus and the mother. The feet have five toes each, armed with claws, and the males carry perforated spurs on the back of the tarsus (attached to a supplementary tarsal-bone). The order Monotremata includes only the two genera Orni- 490 MANUAL OF ZOOLOGY. thorhynchus and Echidna — the one represented by a single species (O. paradoxus\ and the other by two species (E. hystrix and E. setosa). All are exclusively confined to Aus- tralia and Tasmania. The Ornithorhynchus or Duck-mole is one of the most ex- traordinary of Mammals. The body (fig. 186) resembles that of a mole or small otter, and is covered with a close, short, brown fur. The tail is broad and flattened. The jaws are produced to form a beak just like that of a duck in appearance; hence the name of " Duck-billed animal," often applied to it. The margins of the jaw are sheathed with horn, and furnished with transverse horny plates ; but there are no teeth. The nostrils are placed at the apex of the upper mandible. The legs are short, and the feet have five toes each, furnished with Fig. 186. — Ornithorhynchus paradoxus. strong claws, which enable the animal to burrow with facility. The toes are also united by a membrane or web, so that the animal swims with great ease. The Ornithorhynchus is exclu- sively found in Australia and Tasmania, and inhabits streams and ponds. Its food consists chiefly, if not exclusively, of insects, and the animal makes very extensive burrows on the banks of the rivers which it frequents. The young are born quite blind, and nearly naked, and the method in which they obtain milk from the mother is somewhat obscure, as there are no nipples, nor is there any marsupial pouch. It is certain, however, that the beak of the young animal is extremely differ- ent from what it is in the adult condition. The genus Echidna is represented by two species, E. hystrix and E. setosa, both belonging to the Australian province. The Echidna hystrix is the best-known species, and in some exter- nal respects is not unlike a large hedgehog, having the back covered with strong spines, interspersed with a general coating of bristly hairs. The snout has not the form of a duck's bill, MARSUPIALIA. 49 1 as in the Ornithorhynchus, but the two mandibles are greatly elongated, and are enclosed in a continuous skin till close upon their extremities, where there is a small aperture for the protrusion of a very long and flexible tongue. The jaws are wholly devoid of teeth or anything in the place of teeth; and the nostrils are placed at the extremity of the cylindrical snout The feet have five toes each, furnished with strong curved digging-claws, but the toes are not webbed. The Echidna measures from fifteen to eighteen inches in length, and is a nocturnal animal. It lives in burrows, and feeds upon insects, which it catches by protruding its long and sticky tongue. ORDER II. MARSUPIALIA. — The order Marsupialia consti- tutes by itself the sub-class Didelphia, and forms with the Monotremata the division of the Non-placental Mammals. With the single exception of the genus Didelphys, which is American, all the Marsupialia belong to the Melanesian pro- vince ; that is to say, they all belong to Australia, Van Diemen's Land, New Guinea, and some of the neighbouring islands. The following are the characters which distinguish the order : — The skull is composed of distinct cranial bones united by sutures, and they all possess true teeth ; whilst the angle of the lower jaw is almost always inflected. The pectoral arch has the same form as in the higher Mammals, and the cora- coid no longer reaches the anterior end of the sternum. All possess the so-called " marsupial bones," attached to the brim of the pelvis. The corpus callosum is very small, and has been asserted to be absent. The young Marsupials are born in a very imperfect condition, of very small size, and at a stage when their development has proceeded to a very limited degree only. It is believed that there is no placenta or vas- cular communication between the mother and foetus, parturition taking place before any necessity arises for such an arrange- ment. As the young are born in such an imperfect state of development, special arrangements are required to secure their existence. When born, they are therefore, in the great ma- jority of cases, transferred by the mother to a peculiar pouch formed by a folding of the integument of the abdomen. This pouch is known as the " marsupium," and gives the name to the order. Within the marsupium are contained the nipples, which are of great length. Being for some time after their birth extremely feeble, and unable to perform the act of suc- tion, the young within the pouch are nourished involuntarily, the mammary glands being provided with special muscles which force the milk into the mouths of the young. At a 492 MANUAL OF ZOOLOGY. later stage the young can suckle by their own exertions, and they leave the pouch and return to it at will. In a few forms there is no complete marsupium as above described ; but the structure of the nipples is the same, and the young are carried about by the mother, adhering to the lengthy teats. The so-called "marsupial bones" (fig. 187) doubtless serve to support the marsupial pouch and its contained young, but this cannot be their sole function, since they occur in the Monotremes, in which there is no pouch. The oviducts open into vaginal tubes which open into a urogenital canal; but this does not open into a " cloaca," though embraced by a sphincter muscle common to it and to the rectum. The testes are not abdominal throughout life as in the Monotremes, but are lodged in a scrotum. This, however, is placed in front of the penis, and not beneath the pubic arch as in most Mammals. From this unusual position of the scrotum, it is regarded by Owen as being the same structure as the mar- supial pouch of the female, turned inside out. Though they form an extremely natural order, sharply sep- arated from all the rest of the Mam- mals, the Marsupials form a large and varied group. In fact this order, from being the almost exclusive possessor of a continent as large as Australia, has to discharge in the economy of nature func- tions which are elsewhere discharged by several orders. The Marsupialia are divided by Owen into the following sections : — a. Rhizophaga. — In this section is the well-known Australian animal, the Wombat (Phascolomys fossor\ often called by the colonists the "badger." The Wombat is a stout, heavy animal, which attains a length of from two to three feet. The legs are very short and stout, and the animal burrows with ease by means of strong curved digging-claws, with which the fore-feet are furnished. The tail in the Wombat is quite rudimentary, and the whole body is clothed with a brown woolly hair. In its dentition the Wombat presents a curious resemblance to the herbivorous Rodents, There are two Fig. 187.— One side of the pelvis of a Kangaroo, showing the " marsupial bones " (m) — after Owen. MARSUPIALIA. 493 incisors in each jaw, and these are long and rootless, growing from permanent pulps. There are no canines, so that the incisors and praemolars are separated by a considerable space. The dental formula is — . i — i o — o i — i 4 — 4 t - ; c ----- ; Am - ; m - - = 24. i— i ' o— o' * i— i 4—4 The praemolars and molars agree with the incisors in growing from permanent pulps, in which respect the Wombat differs from all the other Marsupials, and agrees with the herbivorous Rodents, with those Edentata which have teeth, and with the extinct Toxodon. — (Owen.) The Wombat is a nocturnal animal, and feeds chiefly upon roots and grass. b. Poephaga. — In this section are the Kangaroos (Macropo- dida) and the Kangaroo-rats or Potoroos (Hypsiprymnus\ all strictly phytophagous. The Kangaroos are distinguished by the disproportionate length of the hind-limbs and dispropor- tionate development of the posterior portion of the body as compared with the fore-limbs and fore part of the body. The hind-legs are exceedingly long and strong, and the feet are much elongated — the whole sole being applied to the ground. The hind-feet have four toes each, of which the central one is by far the largest, and the two inner toes are very small, and are united by a common integument. The tail is also extremely long and strong, and by the assistance of this organ and the powerful hind-limbs the Kangaroos are enabled to effect extraordinarily long and continuous leaps. In fact, leap- ing is the ordinary mode of progression in the typical Kan- garoos; and when walking upon all fours their locomotion is slow and ungraceful. The anterior extremity of the body is very diminutive as compared with the posterior, and the fore- limbs are quite small, but have five well-developed toes armed with strong nails. The head is small, with large ears, and the dental formula is — . 3 — 3 o — o i — i 4 — 4 There are therefore six upper incisors, two lower incisors, and no functional canines (though rudimentary upper canines are present in the young of some of the Kangaroos, at any rate). The stomach is complex, and sacculated. The Kan- garoos are all herbivorous, and mostly live, either scattered or gregariously, on the great grassy plains of Australia. The " Tree-kangaroos," however (constituting the genus Dendro- 494 MANUAL OF ZOOLOGY. 'lagus) live mostly in trees, and in adaptation to this mode of life the fore-legs are nearly as long and strong as the hind-legs. They are natives of New Guinea. The Kangaroo-rats (Hypsiprymnus) differ from the true Kan- garoos chiefly in their smaller size, and in the presence of well- developed upper canines (fig. 188, B). They are diminutive nocturnal animals, and they live mostly upon roots. c. Carpophaga. — Intermediate between the Kangaroos and the typical members of the present section (the Phalangers) is the Phascolarctos — the " native sloth " or " bear " of the Australian colonists and the "koala" of the natives. This curious animal is about two feet in length, having a stout body, covered with a dense bluish-grey fur. The tail is wanting; and the feet are furnished with strong curved claws, which enable the animal to pass the greater part of its existence in trees. In Fig. 188. — A, Dentition of a Carnivorous Marsupial (Thylacinus], showing the long and pointed canines and the trenchant molars and praemolars. B, Dentition of a herbivorous Marsupial (Hypsiprymnus\ showing the flat-crowned molars. (After Owen.) c Canine teeth ; i i Incisors. this it is greatly assisted by the fact that all the feet are pre- hensile, the hallux being opposable, and the digits of the fore- limb divided into two sets, the thumb and index-finger being MARSUPIALIA. 495 opposable to the other fingers. The koala is a slow animal which feeds on the foliage of the trees in which it spends its existence. The typical group of the Carpophagous Marsupials is that of the Phalangistidtz or Phalangers, so called because the second and third digits of the hind-feet are joined together almost to their extremities. The family includes a number of small Marsupials, fitted for an arboreal existence, to which end the hallux is opposable and nail-less, whilst the four remaining toes of the hind-feet have long curved claws. The tail, too, is generally very long, and its tip is usually prehensile. The Phalangers are all small nocturnal animals which live upon fruits and other vegetable food. The best known of them is the Australian Opossum (Phalangista vulpind). which must not be confounded with the true or American Opossums, which belong to another section of the Marsupialia. The Phalangers, namely, are distinguished from the Opossums properly so called, amongst other characters, by their dentition, the canine teeth being always very small and functionally use- less in the lower jaw, and sometimes . in the upper jaw as well. The Phalangista vulpina is nocturnal and arboreal in its habits, and its flesh is esteemed a great delicacy by the native Australians, with whom opossum-hunting is a favourite pursuit. The flying Phalangers or Pdauri are closely allied to the true Phalangers, but differ in not having a prehensile tail, and in having a fold of skin extending on each side between the sides of the body and the fore and hind limbs. By the help of these lateral membranes the Petauri can take extensive leaps from tree to tree ; but though called " flying" Phalangers, they have no power of flight properly so called. They are beautiful little animals, nocturnal in their habits, and having the body clothed with a soft and delicate fur. d. Entomophaga. — In this section the jaws are always furnished with canine teeth, but these are not of very large size, and the animals composing the section are therefore not highly predacious, but "prey, for the most part, on the smaller and weaker classes of invertebrate animals." In this section are the Bandicoots (Peramelidce), the American Opossums (Diddphidce)^ and the Banded Ant-eater (Myrmecobius). The Bandicoots (Peramelidcz) are small Australian animals, which appear to fill the place of the Hedgehogs, Shrew-mice, and other small Insectivora of the Old World. The hind- limbs in the Bandicoots are considerably longer than the fore- limbs, and their progression is therefore by a series of bounds. 496 MANUAL OF ZOOLOGY. The fore-limbs have really five toes each, but only the central three of these are well developed, the outermost and innermost digits being rudimentary. The three functional toes are armed with long strong claws, with which the Bandicoots burrow with great ease. The marsupial pouch — and this is a singular point — opens, in some species at any rate, backwards instead of forwards. In the nearly-allied genus Ch&ropus, also from Australia, it appears that the two outer toes of the fore-feet are entirely absent. The second family of this section — namely, the true Opos- sums or Didelphidce — is remarkable in being the only group of the whole order which occurs out of the Australian province. The Diddphid&i namely, are exclusively found in North and South America, where they are known as "Opossums." A considerable number of species are known, but they are mostly of small size, the largest measuring not more than from two to three feet, inclusive of the tail. The Virginian Opos- sum (Didelphys Virginiana) is the only member of the family which is found in North America, and it was the earliest Mar- supial known to science. Most of the Opossums are carnivor- ous, feeding upon small quadrupeds and birds, but they also eat insects, and sometimes even fruit. One species (Didelphys cancrivord) lives chiefly upon Crabs ; and the Yapock ( Cheiro- nectes) has webbed feet, and appears to lead a semi-aquatic life. All the Didelphidce have the hallux nail-less and opposable to the other toes, so as to convert the hind-feet into prehensile hands, and all have a more or less perfectly prehensile tail, these being adaptations to an arboreal life. The marsupial pouch is sometimes not present in a complete form, but is merely represented by cutaneous folds of the abdomen con- cealing the nipples. In the Didelphys dorsigera, in which this peculiarity obtains, the young soon leave the nipples, and are then carried about on the back of the mother, to whom they cling by twining their prehensile tails round hers. The dentition of the Opossums is remarkable for, the great number of the incisor teeth, the dental formula being — / 5-ZL5. c !=I;^ 3-3. ^ ±=4 = 50. 4—4 i— i 3—3 4—4 The Banded Ant-eater (Myrmecobius fasciatus) is a small but extremely elegant little animal, which inhabits Western and Southern Australia, and lives upon insects (fig. 189). The tail is bushy, and differs from that of the Didelphidce. in not being prehensile. The fore-feet have five toes armed with claws ; the hind-feet have only four toes. The Myrmecobius is remarkable MARSUPIALIA. 497 for the extraordinary number of molar teeth, in which it exceeds any existing Marsupial, and is only surpassed by some of the Armadillos. The dental formula is — • 4=4 ; c ! 33 * • e. Sarcophaga. — This is the last section of the existing Mar- supials, and includes a number of predacious and rapacious Fig. 189. — Myrmecobius fasciattts. forms, which fill the place held elsewhere by the true Carnivora. They are distinguished by the fact that the intestine is destitute of a caecum, and by their strictly carnivorous dentition, the canines being strong, long, and pointed, whilst the molars and praemolars have cutting edges furnished with three cusps (fig. 1 88, A). The best-known species of this section are the Thy- lacinus cynocephalus and the Dasyurus ursinus. The former of these is the largest of the rapacious Marsupials, being about as big as a shepherd's dog. It is a native of Van Diemen's Land, and is known to the colonists as the " hyaena." Its head is very large, and the back exhibits several transverse black bands. It lives in caverns and amongst the rocks in the wildest parts of the colony, and its numbers have been very much reduced by the constant war waged upon it by the settlers. The Dasyurus ursinus is also a native of Van Diemen's Land, where it is known as the "native devil." Though smaller than the Thylacine, the Dasyurus is extremely ferocious, and is capable of committing great havoc amongst animals even as large as sheep. VOL. II. 2 i MANUAL OF ZOOLOGY. PL A CENTAL MAMMALS. CHAPTER LXXV. EDENTATA. ORDER III. EDENTATA, or BRUTA. — The lowest order of the placental or monodelphous Mammals is that of the Edentata, often known by the name of Bruta. The name Edentata is certainly not an altogether appropriate one, since it is only in two genera in the order that there are absolutely no teeth. The remaining members of the order have teeth, but these are always destitute of true enamel, are never displaced by a second set, and have no complete roots. Further, in none of the Edentata are there any median incisors, and in only one species (one of the Armadillos) are there any incisor teeth at all. Canine teeth, too, are almost invariably wanting. Clav- icles are usually present, but are absent in the Scaly Ant- eater or Manis. All the toes are furnished with long and powerful claws. The mammary glands are usually pectoral, but are sometimes abdominal in position. The testes are ab- dominal in position. The skin is often covered with bony plates or horny scales. The order Edentata is conveniently divided into two great sections, in accordance with the nature of the food, the one section being phytophagous, the other insectivorous. In the former section is the single group of the Sloths (Bradypodidce). In the latter are the two groups of the Armadillos (Dasypodid&\ and the various species of Ant-eaters (the latter constituting Owen's group of the Edentula). The order Edentata is but sparingly represented in modern times, and its geographical distribution is peculiar. The true Ant-eaters, the Armadillos and the Sloths, are entirely confined to South America, in which country a group of gigantic extinct Edentates existed in Post-tertiary times. The Scaly Ant-eater or Manis is common to Asia and Africa, and the genus Oryc- teropus is peculiar to South Africa. The family Bradypodidcs comprises some exceedingly curious EDENTATA. 499 animals which are exclusively confined to South America, in- habiting the vast primaeval forests of that continent. The Sloths have a remarkably short and rounded face, and the body is cov- ered with hair. The incisor teeth are altogether wan ting, but there are always simple molars, and in the Two-toed Sloth or Unau the first tooth in each jaw on each side is so much larger than the others, and so much more pointed, that it has been regarded as a canine. The stomach is complex, somewhat resembling that of the Ruminants. The cervical vertebrae are generally regarded as being more than the normal seven in number in the Two-toed Sloth, and the long bones have no medullary cavi- ties. The most striking peculiarities, however, about the Sloths are connected with their peculiar mode of life. The Sloths, in fact, are constructed to pass their life suspended from the under surface of the branches of the trees amongst which they live ; and for this end their organisation is singularly adapted. The fore-limbs are much longer than the hind-limbs, and the bones of the fore-arm are unusually movable. All the feet, but especially the fore-feet, are furnished with enormously long curved claws (fig. 190), by the aid of which the animal is enabled to move about freely suspended back-downwards from the branches. Not only is this the ordinary mode of progres- sion amongst the Sloths, but even in sleep the animal appears to retain this apparently unnatural position. Fig. 190.— Hand of Three-toed Sloth (Bradypus tridactylus)—zS.ter Owen. Owing to the disproportionate size of the fore-limbs as com- pared with the hind-limbs, and owing to the fact that the hind- feet are so curved as to render it impossible to apply the sole to the ground, the Sloth is an extremely awkward animal upon the ground, and it has therefore recourse to terrestrial progres- sion only when absolutely compelled to do so. Whilst the 50O MANUAL OF ZOOLOGY. name of " Sloth" may thus appear to be a merited one from the point of view of a terrestrial Mammal, it is wholly unde- served when the animal is looked upon as especially adapted for an arboreal existence. The second family of the Edentata is that of the Dasypodida or Armadillos. These are found exclusively in South America, as are the Sloths, but they are very different in their habits. The Armadillos are burrowing animals, furnished with strong digging-claws and well-developed collar-bones. The jaws are provided with numerous simple molars, which attain the enor- mous number of nearly one hundred in the great Armadillo (Dasypus gigas). The upper surface of the body is covered with a coat of mail, formed of hard bony plates or shields, united at their edges. A portion of this armour covers the head and shoulders, and another portion protects the hind- quarters; whilst between these is a variable number of movable bands which run transversely across the body, and give the necessary flexibility to this singular dermoskeleton. In some species this flexibility is so great that the animal can roll itself up like a hedgehog. The tail is likewise covered with bony scutes. Fig. 191. — Chlamyphorus truncatus. The Armadillos are confined entirely to South America, ranging from Mexico to Patagonia. In this country, also, have been found the remains of a gigantic armour-plated animal allied to the Armadillos, which will be subsequently described under the name of the Glyptodon. The remaining members of the Edentata are the various Ant- eaters, but these are so different from one another in their char- EDENTATA. 501 acters that they form three distinct families, also distinguished by their geographical distribution. a. Myrmecophagida. — This family is exclusively confined to South America, as are the two preceding, and it contains only the Hairy or true Ant-eaters. These curious animals feed chiefly upon Ants and Termites, which they catch with their long sticky tongues. The jaws are wholly destitute of teeth ; the body is covered with hair ; there is a long tail ; and the feet are armed with long and strong curved digging-claws. The best-known species of this family is the "Tamandua" or Great Ant-eater (Myrmecophaga jubata). This singular animal attains a length of over four feet, and has an extremely long and bushy tail. The jaws are produced to form a long and slender snout, which is entirely enclosed in the skin, till just at its extremity, where there is an aperture for the protru- sion of the thread-like tongue. The anterior feet have four, and the posterior feet five toes, all armed with strong curved claws, which, when not used in digging, are bent inwards, so that the animal walks on the sides of the feet. The animal is perfectly harmless and gentle when unmolested, and leads a solitary life. It lives mainly upon Termites, into the nests of which it forces its way by means of the powerful claws. When the Termites rush out to see what is the matter, the Ant-eater thrusts out its glutinous tongue, an action which can be repeated with mar- vellous rapidity. b. Manidce. — This family includes only the Scaly Ant-eaters or Pangolins, all exclusively confined to the Old World, and found in both Africa and Asia. The whole of the body in the Manidce is covered with an armour of horny imbricated plates, overlapping like the tiles of a house, and apparently consisting of agglutinated hairs. The legs are short, and furnished with five toes each, ending in long and strong digging-claws ; but there are no clavicles. The tongue resembles that of the Hairy Ant-eaters in being long and contractile, and capable of being exserted for a considerable distance beyond the mouth. It is covered with a glutinous saliva, and is the agent by which the animal catches ants and other insects. The jaws are wholly destitute of teeth. When threatened by danger, the Pangolins roll themselves up into a ball, like the hedgehogs. The tail is comparatively long, and is covered with scales. Though very strong for their size, none of the species attain a length of more than three or four feet, inclusive of the tail. c. Orycteropidcz. — The last family of the living Edentata is that of the Orycteropidtz, comprising only the single genus Orycteropus. This genus comprises only a single species, the SO2 MANUAL OF ZOOLOGY. O. Capensis, which is peculiar to South Africa, and is known by the Dutch colonists as the "Aardvark" or Ground-hog. The animal is nocturnal in its habits, and lives upon insects. The body is elongated, and the tail is long, the species attain- ing a total length of four feet or more. The legs are short, the anterior pair having four unguiculate toes, the posterior five. The claws are strong and curved, and enable the animal to construct extensive burrows. The skin is very thick, and is thinly covered with bristly hairs ; and the tail is hairy. The head is elongated, and the mouth small — devoid of incisor and canine teeth, but furnished with a number of cylindrical molars (^^)- The crowns of the molars are flat, and they are composed of dentine traversed by numerous dichotomising pulp-cavities. The tongue is long, and is covered by a sticky saliva, by the aid of which the animal catches insects. CHAPTER LXXVI. SI RENT A AND GET ACE A. ORDER IV. SIRENIA. — This order comprises no other living animals except the Dugongs and Manatees, which are often placed with the true Cetaceans (Whales and Dolphins) in a common order. There is no doubt, in fact, but that the Sirenia are very closely allied to the Cetacea, and though they are to be regarded as separate orders, yet they may be advantage- ously considered as belonging to a single section, which has been called Mutilata, from the constant absence of the hind- limbs. The Sirenia agree with the Whales and Dolphins in their complete adaptation to an aquatic mode of life (fig. 192); especially in the presence of a powerful caudal fin, which differs from that of Fishes in being placed horizontally and in being a mere expansion of the integuments, not supported by bony rays. The hind-limbs are wholly wanting, and there is no sa- crum. The anterior limbs are converted into swimming-paddles or " flippers." The snout is fleshy and well developed, and the nostrils are placed on its upper surface, and not on the top of the head, as in the Whales. Fleshy lips are present, and the upper one usually carries a moustache. The skin is covered with fleshy bristles. The head is not disproportionately large, SIRENIA. 503 as in the true Whales, and is not so gradually prolonged into the body as it is in the latter. There may be only six cervical vertebrae. The teats are two in number and are " thoracic," — i. e., are placed on the chest. There are no clavicles, and the digits have no more than three phalanges each. The testes are retained throughout life within the abdomen, but vesiculae seminales are present. The animal is diphyodont, the perma- nent teeth consisting of molars with flattened crowns adapted for bruising vegetable food, and incisors which are present in the young animal, at any rate. In the extinct Rhytina it does not appear that there were any incisor teeth. Fig. 192. — Sirenia. Dugong (Halicore). The only existing Sirenia are the Manatees (Manatus) and the Dugongs (Halicore], often spoken of collectively as " sea- cows," and forming the family of the Manatidcs. The Manatees are characterised by the possession of numer- 8—8 ous molar teeth (o~o), and of two small upper incisors, which are wanting in the adult. The tail-fin is oblong or oval in shape, and the anterior limbs are furnished with nails to the four outer digits. They occur on the east coast of North America, especially in the Gulf of Mexico, and another species is found on the west coast of Africa, They are generally found in considerable numbers about the mouths of rivers and estu- aries, and they appear to live entirely upon sea-weeds, aquatic plants, or the littoral vegetation. They are large awkward animals, attaining a length of from eight to ten feet as a rule, but sometimes growing to a length of nearly twenty feet. The Dugongs (Halicore, fig. 192) have —^- molar teeth in 0 0 2— — 2 the young condition, but only - — when old. Inferior incis- ors are present in the young animal, but are wanting in the adult. The upper jaw carries two permanent incisors, which 504 MANUAL OF ZOOLOGY. are entirely concealed in the jaw in the females, but which increase in size in the males with the age of the animal, till they become pointed tusks. The anterior extremities are nail- less, and the tail-fin is crescentic in shape. In their general appearance and in their habits the Dugongs differ little from the Manatees, and they are often killed and eaten. They attain a length of from eight to ten, twelve, or more feet, and are found chiefly on the coasts of the Indian Ocean. The bones are remarkable for their extreme density, their texture being nearly as close as ivory. The Manatees and Dugongs, as before said, are the only living Sirenia; but besides these there is a very singular form, the Rhytina Stelleri, which is now extinct, having been exter- minated by man within a comparatively recent period. This remarkable animal was discovered about the middle of the eighteenth century in a little island (Behring's Island) off the coast of Kamschatka. Upon this island the celebrated voyager Behring was wrecked, and he found the place inhabited by these enormous animals, which were subsequently described by M. Steller, who formed one of his party. The discovery, however, was fatal to the Rhytina, for the last appears to have been seen in the year 1768. The Rhytina was an animal of great size, measuring twenty-five feet in length, and twenty feet at its greatest circumference. There can hardly be said to have been any true teeth, but the jaws contained — — large lamelliform fibrous structures, which officiated as teeth, and may be looked upon as molars. The epidermis was extremely thick and fibrous, and hairs appear to have been wanting. There was a crescentic tail-fin, and the anterior limbs alone were present. ORDER V. CETACEA. — In this order are the Whales, Dol- phins, and Porpoises, all agreeing with the preceding in their complete adaptation to an aquatic life (figs. 195, 196). The body is completely fish-like in form ; the anterior limbs are con- verted into swimming - paddles or "flippers"; the posterior limbs are completely absent ; and there is a powerful, horizon- tally-flattened, caudal fin, sometimes accompanied by a dorsal fin as well. In all these characters the Cetacea agree with the Sirenia, except in the one last mentioned. On the other hand, the nostrils, which may be single or double, are always placed at the top of the head, constituting the so-called " blow-holes " or " spiracles " ; and they are never situated at the end of a snout. The body is very sparingly furnished with hairs, or the adult may be completely hairless. The testes are retained CETACEA. 505 throughout life within the abdomen and there are no vesiculas seminales. The teats are two in number and are placed upon the groin. The head is generally of disproportionately large size, and is never separated from the body by any distinct con- striction or neck. The lumbar region of the spine is long, and, as in the Sirenia, there is no sacrum, and the pelvis is only present in a rudimentary form. There are no clavicles, and some of the digits may possess more than three phalanges each. Lastly, the adult is either destitute of teeth or is mono- phyodont — that is to say, possesses but a single set of teeth, which are never replaced by others. When teeth are present, they are usually conical and numerous, and they are always of one kind only. The Cetacea may be divided into the three families of the Balcenidcz or Whalebone Whales, the Delphinida or Dolphins and Porpoises, and the Catodontida or Sperm Whales. Of these, the BalcenidcE are often spoken of as the " toothless " Whales, whilst the other two families are called the " toothed " Whales ( Odontoceti}. Fig. 193. — Skull of the Right Whale Bal&na mysticetus) — after Owen. Fam. i. Balcenida. — Tti*l?afo*jafa or Toothless Whales are characterised by the total absence of teeth in the adult (fig. 193). Teeth, however, are present in the fcetal Whale, but they never cut the gum. The place of teeth is supplied by a number of plates of whalebone or " baleen " attached to the palate ; hence the name of " whalebone Whales " often given to this family. They are the largest of living animals, and may be divided into the two sections of the Smooth Whales, in which the skin is smooth and there is no dorsal fin (as in the Greenland Whale), and the Furrowed Whales, in which the skin is furrowed and a dorsal fin is present (as in the so- called Finner Whales and Hump-backed Whales). 506 MANUAL OF ZOOLOGY. The Greenland or " Right " Whale (Balcena mysticetiis) will illustrate almost all the leading points of interest in the family. The Greenland Whale is the animal which is sought after in the whale-fishery of Europe, and hence the name of " Right " Whale often applied to it. It is an inhabitant of the Arctic seas, and reaches a length of from forty to sixty feet. Of this enormous length, nearly one-third is made up of the head, so that the eye looks as if it were placed nearly in the middle of the body. The skin is completely smooth, and is destitute of hairs in the adult. The fore-limbs are converted into " flip- pers " or swimming-paddles, but the main organ of progression is the tail, which often measures from twenty to twenty-five feet in breadth. The mouth is of enormous size, the upper jaw somewhat smaller than the lower, and both completely destitute of teeth. Along the middle of the palate runs a strong keel bordered by two lateral depressions, one on each side. Arranged transversely in these lateral depressions are an enormous number of horny plates, constituting what is known as the " baleen " plates, from which the whalebone of commerce is derived. The arrangement of the plates of baleen is somewhat as follows (fig. 1 94) : — Each plate is somewhat trian- gular in shape, the shortest side or base being deeply sunk in the palate. The outer edge of the plate is nearly straight, and is quite unbroken. The inner edge is slightly concave, and is furnished with a close fringe formed of detached fibres of whale- bone. For simplicity's sake each baleen-plate has been re- garded here as a single plate, but in reality each plate is com- posed of several pieces, of which the outermost is by far the largest, whilst the others gradually decrease in size towards the middle line of the palate. The large marginal plates are from eight to ten or fourteen feet in length, and there may be about two hundred on each side of the mouth. The object of the whole series of baleen-plates with which the palate is furnished, is as follows : — The Whale is a strictly carnivorous or zoophagous animal, but owing to the absence of teeth, and the comparatively small calibre of the oesophagus, it lives upon very diminutive animals. The Whale, in fact, lives mostly upon the shoals of small Pteropodous Molluscs, Ctenophora, and Medusa, which swarm in the Arctic seas. To obtain these, the Whale swims with the mouth opened, and thus fills the mouth with an enormous mass of water. The baleen-plates have the obvious function of a " screening-appa- ratus." The water is strained through the numerous plates of baleen, and all the minute animals which it contains are arrested and collected together by the inner fibrous edges of the baleen- GET ACE A. 507 plates. When, by a repetition of this process, the Whale has accumulated a sufficient quantity of food within the central cavity of the mouth, it is enabled to swallow it, without taking the water at the same time. Fig. 194. — Diagram of the Baleen-plates of a Whale, a. a Section of the palatal sur- face of the upper jaw, showing the strong median ridge or keel ; b b Baleen-plates, sunk at their bases in the palate ; ff Fibrous margin of Baleen-plates. We have now to speak of a phenomenon which has given rise to a considerable amount of controversy, namely, what is known as the " blowing " or " spouting " of the whale. In all the Cetaceans the nose opens by a single or double aperture (the latter in the Balcznida) upon the top of the head, and these external apertures or nostrils are known as the " blow-holes " or " spiracles." The act known to the whalers as " blowing " consists in the expulsion from the blow-holes of a jet of what is apparently water, or at any rate looks like it. The act is performed by the whale upon rising to the surface, and it is usually by this that the whereabouts of the animal is discovered. The old view as to what takes place in the act of blowing is, that the whale is really occupied in getting rid of the surplus water which it has taken in at the mouth and strained through the baleen-plates. The modern, and doubtless correct, view, however, is that the water which has been strained through the 508 MANUAL OF ZOOLOGY. baleen really makes its escape at the side of the mouth, and does not enter the pharynx to be expelled through the nose. Upon this view the apparent column of water emitted from the blow-holes in the act of blowing consists really of the expired air from the lungs, the contained watery vapour of which is suddenly condensed on its entrance into the cold atmosphere. With the expired air there may be such water as may have gained access to the nose through the blow-hole, for the expul- sion of which proper provision exists in the form of muscular diverticula of the nasal cavity. It is also possible that the column of air in being forcibly expelled from the blow-hole may take up with it some of the superincumbent water. The skin in the Right Whale is perfectly smooth and naked, but it is underlaid by a thick layer of subcutaneous fat, which varies from eight to fifteen inches in thickness, and is known as the " blubber." The blubber serves partly to give buoyancy to the body, but more especially to protect the ani- mal against the extreme cold of the medium in which it lives. It is the blubber which is chiefly the object of the whale-fishery, as it yields the whale-oil of commerce. The whale which is captured in the Antarctic regions is not the same species as the Greenland Whale, and is termed the Balczna australis. It is much about the size of the Right Whale, averaging about fifty feet, but the head is proportion- ately smaller. This whale is an inhabitant of the greater part of the Pacific out of the regions of the tropics; but it is chiefly captured when approaching land, which the females do for the purpose of bringing forth their young. The only remaining members of the Balanida which require notice are the Rorquals and Hump - backed Whales, consti- tuting the group of the " Furrowed " Whales. These are col- lectively distinguished by having the skin furrowed or plaited to a greater or less extent, whilst the baleen-plates are short, and there is a dorsal fin. The specific determination of these animals is a matter of great difficulty, but there would appear to be two very well marked genera: — i. The genus Megap- tera, including the so-called Hump-backed Whales, in which the flippers are of great length, from one-third to one-fifth of the entire length of the body. 2. The genus Balcznoptera, compris- ing the so-called Rorquals or Piked Whales, in which the flip- pers are of moderate size. In both genera there is a dorsal adipose fin, so that they are both " Finner " Whales. The Balanoptera reach a gigantic size, being sometimes as much as eighty or one hundred feet in length. They are very active animals, however, and their CETACEA. 509 whalebone is comparatively valueless, so that the whalers rarely meddle with them, though they are not uncommon, and are often driven ashore on our own coasts. Fam. 2. Catodontida. — The family of the Catodontidcz or Physeterida comprises the Sperm Whales or Cachalots, with which we commence the series of the Toothed Whales ( Odon- toceti). They are characterised by the fact that the palate is destitute of baleen-plates, and the lower jaw possesses a series (about fifty-four) of pointed conical teeth, separated by inter- vals, and sunk in a common alveolar groove, which is only im- perfectly divided by septa. The upper jaw is also in reality furnished with teeth, but, with a single partial exception, these do not cut the gum. Fig. 195. — Spermaceti Whale (Physeter macrocefhalus). The best-known species of this family is the great Cachalot or Spermaceti Whale (Physeter macrocephalus, fig. 195). This animal is of enormous size, averaging from fifty to seventy feet in length, but the females are a good deal smaller than the males. The head is disproportionately large, as in the Balczn- id(Z) forming nearly one-third of the entire length of the body. The snout forms a broad truncated muzzle, and the nostrils are placed near the front margin of this. The Sperm Whales live together in troops or " schools," and they are found in various seas, especially in the North Pacific. They are largely sought after, chiefly for the substance known as " spermaceti ; " but besides this they yield oil and the singular body called " ambergris." The spermaceti is a fatty substance which has the power of concreting when exposed to the air. It is 'not only diffused through the entire blubber, but is also contained in special cavities of the head. The sperm-oil yielded by the blubber is exceedingly pure, and is free from the unpleasant odour of ordinary whale-oil. The ambergris is a peculiar sub- stance which is found in masses in the intestine, and is proba- bly of the nature of a biliary calculus, since it is said to be com- posed of a substance very nearly allied to cholesterine. It is used both as a perfume itself, and to mix with other perfumes. 510 MANUAL OF ZOOLOGY. Fam. 3. Delphinida. — This family includes the Dolphins, Por- poises, and Narwhal, and is characterised by usually possessing teeth in both jaws ; the teeth being numerous, and conical in shape. The nostrils, as in the last family, are united, but they are placed further back, upon the top of the head. The single blow-hole or nostril is transverse and mostly crescentic or lunate in shape. The head is by no means so disproportionately large as in the former families, usually forming about one-seventh of the entire length of the body. Fig. 196. — The common Dolphin (Delfhinus delphis). The most noticeable members of this family are the true Dolphins, the Porpoises, and the Narwhal. The Dolphins have an elongated snout, separated from the head by a transverse depression. The common Dolphin (Del- phinus delphis, fig. 196) is the best-known species. It aver- ages from six to eight feet in length, and has the habit of swim- ming in flocks, often accompanying ships for many miles. The female, like most of the Cetacea, is uniparous. The Dolphin occurs commonly in all European seas, and is especially abun- dant in the Mediterranean. The common Porpoise (Phocana communis) is the commonest and smallest of all the Cetacea, rarely exceeding four feet in length. The head is blunt, and is not produced into a pro- jecting muzzle. The Porpoise frequents the North Sea, and is commonly seen off our coasts. Another British species is the Grampus (Phoccena orca), but this is much larger, attaining a length of from eighteen to twenty feet. Nearly allied to the Grampus is the so-called " Caing " Whale, or, as it is some- times termed, the " Bottle-nosed " Whale (Globicephalus or Phocana globiceps). This species occurs not uncommonly round the Orkney and Shetland Islands, and attains a length of as much as twenty-four feet It is gregarious in its habits, and is often killed for the sake of its oil. Closely allied to the true Dolphins are two curious Cetaceans, UNGULATA. 5 1 1 belonging to different genera, but both inhabiting fresh waters. One of these is the Gangetic Dolphin (Platanista Gangeticd), which inhabits the Ganges, especially near its mouth. This singular animal is characterised by the great length of its slender muzzle, and by the small size of the eyes. It attains the length of seven feet, and the blow-hole is a longitudinal fissure, and therefore quite unlike that of the typical Del- phinidce. The other fresh-water form is the Inia Boliviensis, which inhabits the rivers of Bolivia, and is found at a distance of more than two thousand miles from the sea. In its essential characters it differs little from its marine brethren, and it attains a length of from seven (female) to fourteen feet (male). The last of the Delphmida is the extraordinary Narwhal or Sea-unicorn (Monodon monoceros). The Narwhal is an inhabi- tant of the Arctic seas, and attains a length of as much as fifteen feet, counting in the body alone. The dentition, how- ever, is what constitutes the great peculiarity of the Narwhal. The lower jaw is altogether destitute of teeth, and the upper jaw in the females also exhibits no teeth externally, as a general rule at any rate, though there are two rudimentary incisors which do not cut the gum. In the males, the lower jaw is likewise edentulous, but the upper jaw is furnished with two molar teeth concealed in the gum, and with two incisors. Of these two upper incisors, that of the right side is generally rudimentary, and is concealed from view. The left upper incisor, on the other hand, is developed from a permanent pulp, and grows to an enormous size, continuing to increase in length throughout the life of the animal. It forms a tusk of from eight to ten feet in length, and it has its entire surface spirally twisted. As an abnormality, both the upper incisors may be developed in this way so as to form projecting tusks; and it is stated that the tusk is occasionally present in the female. The function of this extraordinary tooth is doubtless offensive. CHAPTER LXXVIL UNGULATA.' ORDER VI. UNGULATA.— The order of the Unguiata, or Hoofed Quadrupeds, is one of the largest and most important of all the divisions of the Mammalia. It comprises three entire old orders — namely, the Pachydermata, Solidungula, and Ruminantia. 512 MANUAL OF ZOOLOGY. The first of these old divisions — that of the Pachydermata — included the Elephants, Rhinoceros, Hippopotamus, Tapirs, and the Pigs, all characterised, as the name implies, by their thick integuments. The name is still used to express this fact, though the order is now abandoned, and is merged with that of the Ungulata; the Elephants alone being removed to a separate order under the name of Proboscidea. The second old order — that of the Solidungula or Solipedes — included the Horse, Zebra, and Ass, all characterised by the fact that the foot terminates in a single toe, encased in an expanded hoof. The name Solidungula is still retained for these animals, as a section of the Ungulata. The third old order — that of the Ruminantia — includes all those animals, such as Oxen, Sheep, Goats, Camels, Giraffes, Deer, and others, which chew the cud or " ruminate," and have two functional toes to each foot, encased in hoofs. The name Ruminantia is still retained for these animals, as constituting a most natural group of the Ungulata. All these various animals, then, are now grouped together into the single order of the Ungulata, or Hoofed Quadrupeds, and the following are the characters of the order : — All the four limbs are present, and that portion of the toe which touches the ground is always encased in a greatly-ex- Fig. 197.— Ungulata. A, Perissodactyle foot of Zebra (Solidungula)', B, Artiodactyle foot of Llama ; C, Artiodactyle foot of Antelope ; D, Perissodactyle foot of Rhino- ceros. panded nail, constituting a "hoof." There are never more than four full-sized toes to each limb. Owing to the encase- ment of the toes in hoofs, the limbs are useless for prehension, and only subserve locomotion ; hence clavicles are always want- UNGULATA. 513 ing in the entire order. There are always two sets of enamelled teeth, so that the animal is diphyodont. The molar teeth are massive and have broad crowns, adapted for grinding vegetable substances. The order Ungulata is divided into two primary sec- tions : — the Perissodactyla, in which the toes or hoofs are odd in number (one or three), and the Artiodactyla> in which the toes are even in number (two or four). SECTION A. PERISSODACTYLA. — The section of the Perisso- dactyle Ungulates includes the Rhinoceros, the Tapirs, the Horse and its allies, and some extinct forms, all agreeing in the following characters : — The hind-feet are odd-toed in all (fig. 197, A, D), and the fore-feet in all except the Tapirs. The dorso-lumbar vertebrae are never less than twenty-two in number. The femur has a third trochanter. The horns, if present, are not paired. Usually there is only one horn, but if there are two, these are placed in the middle line of the head, one behind the other (fig. 198). In neither case are the horns ever supported by bony horn-cores. The stomach is simple, and is not divided into several compartments; and there is a large and capacious caecum. The three existing genera of Perissodactyle Ungulates — namely, the Horse, Tapir, and Rhinoceros, are widely removed from one another in many important characters; but the intervals between them are filled up by an extensive series of fossil forms, commencing in the Lower Tertiary Strata. Fam. i. Rhinocerida. — This family comprises only a single genus, the genus Rhinoceros, unless, indeed, the little Hyrax is to be retained in this order. The Rhinoceroses are ex- tremely large and bulky brutes, having a very thick skin, which is usually thrown into deep folds. The muzzle is rounded and blunt, and there are - — - molars, with tuberculate crowns. There are no canines, but there are usually incisor teeth in both jaws. The feet are furnished with three toes each, encased in hoofs. The nasal bones support one or two horns, which are not paired. The horn is composed of longitudinal fibres, which are agglutinated together, and are of the nature of epidermic growths, somewhat analogous to hairs. When two horns are present, the hinder one is carried by the frontal bones, and is placed in the middle line of the head behind the anterior horn. The posterior horn is usually much shorter than the anterior one, and if not, it differs in shape. The Rhino- ceroses live in marshy places, and subsist chiefly on the foliage VOL. II. 2 K 514 MANUAL OF ZOOLOGY. of trees. They are exclusively confined at the present day to the warmer parts of the Old World; but an extinct species (Rhinoceros tichorhinus] formerly inhabited England, and ranged over the greater part of Europe. Of the one-horned species, the best known is the Indian Rhinoceros (R. Indicus], which was probably the "Unicorn " of the ancients. Another species with one horn (R. Sondaicus) inhabits Java. Of the two-horned species, one (R. Sumatrensis) is found in Sumatra, and is remarkable for the comparative absence of cutaneous folds. The best known, however, is the African Rhinoceros (R. bicornis), which occurs abundantly in Cape Colony and in the southern parts of the African continent (fig. 198.) Fig. 198. — Head of two-horned Rhinoceros (R. bicornis). Fain. 2. Tapiridce. — The Tapirs are characterised by the pos- session of a short movable proboscis or trunk. The skin is hairy and very thick. The tail is extremely short. The fore- feet have four toes each, but these are unsymmetrical, and the hind-feet have only three toes, all encased in hoofs. The jaws are furnished with incisor teeth, (~^% small canines, and <5 «3 I — 7 molars. 6 — 6 Three species of Tapir are known, of which the most familiar is the American Tapir (T. Americanus), which inhabits the vast forests of South America. It is a large animal, something like a pig in shape, but brownish black in colour. It is nocturnal in its habits, and is strictly phytophagous. The proboscis is employed in conveying the food to the mouth, and the nostrils are placed at its extremity. It attains altogether a total length UNGUUATA; 515 of from five to six feet. Another species, with longer hair (T. villosus), inhabits the Andes, and a still larger species (T. Ma- layanus) is found in Sumatra and Malacca. Nearly allied to the Tapirs is the fossil genus Palaotherium, found in the Eocene Rocks of France and other countries. Many species of the genus are known, all seeming to have possessed a short proboscis like that of the Tapirs. All the feet, however, were tridactylous. Earn. 3. Solidungula or Equidcz. — This family comprises the Horses, Asses, and Zebras, characterised by the fact that the feet have only a single perfect toe each, enclosed in a single broad hoof, without supplementary hoofs (fig. 197, A). There is a discontinuous series of teeth in each jaw ; and in the males, canines are present, but these are wanting in the females. The dental formula Js — i 3=3. c 1=J ; pm 3=3 . m 3=3 = 4a 3—3 i— i 3—3 3—3 The skin is covered with hair, and the neck is furnished with a mane. The family Equida is divided by Dr Gray into two sections or genera: Equus, comprising the Horse; and Asinus, com- prising the Asses and Zebras. The genus Equus is distinguished by the fact that the animal is not banded, and has no dorsal line, both the fore and hind legs have warts, and the tail is hairy throughout. The genus appears to contain no more than one well-marked species, as far as living forms are concerned — namely, the Equus caballus. From this single species appear to have descended all the in- numerable varieties of horses which are employed by man. The native country of the horse appears to have been Central Asia, but all the known wild individuals at the present day appear to be descendants of domestic breeds. The genus Asinus is characterised by the fact that there is always a distinct dorsal line, and the body is more or less banded, the fore-legs alone have warts, and the tail has a tuft of long hairs at its extremity. The Ass is probably a native of Asia (where the wild Ass is at present a native), and there ap- pears to be little doubt but that the common Ass is merely the domesticated form of the wild Ass (Equus onager]. The striped members of this section are known as Zebras and Quaggas, and are natives of the southern parts of Africa. SECTION B. ARTIODACTYLA. — In this section of the Ungu- lates the number of the toes is even — either two or four — and the third toe in each foot forms a symmetrical pair with the 516 MANUAL OF ZOOLOGY. fourth (fig. 197, B, C). The dorso-lumbar vertebrae are nineteen in number, and there is no third trochanter on the femur. If true horns are present, these are always in pairs, and are sup- ported by a bony horn-core. The antlers of the Deer are also paired, but they are not to be regarded as true horns. The stomach is always more or less complex, or is divided into se- parate compartments, and the caecum is comparatively small and simple. The section Artiodactyla comprises the Hippopotamus, the Pigs, and the whole group of the Ruminants, including Oxen, Sheep, Goats, Antelopes, Camels, Llamas, Giraffes, Deer, &c. Besides these there is an extensive series of fossil forms com- mencing in the Eocene or Lower Tertiary period, and in many respects filling up the gaps between the living forms. OMNIVORA. 1. Hippopotamida. — This group contains only the single genus Hippopotamus, characterised by the massive heavy body, the short blunt muzzle, the large head, and the presence of /j <2 teeth of three kinds in both jaws. The incisors are > tne 2 2 i — i 7 — 7 6 — 6 canines extremely large, , and the molars or ^ — -,, with crowns adapted for grinding vegetable substances. The feet are massive, and are terminated by four hoofed toes each. The eyes and ears are small, and the skin is extremely thick, and is furnished with few hairs. The tail is very short. Several extinct species of Hippopotamus are known, but there is only one well-established living form, the Hippopotamus am- phibius, and this is confined to the African continent. It is an enormously bulky and unwieldy animal, reaching a length of eleven or twelve feet. It is nocturnal in its habits, living upon grass and small shrubs, and it swims and dives with great facility. It is found in tolerable abundance in the rivers of Abyssinia, and occurs plentifully in South Africa. Another supposed species (H. Liberiensis) occurs on the west coast of Africa, but there is some doubt as to the specific distinct- ness of this. 2. Suida. — The group of the Suida, comprising the Pigs, Hogs, and Peccaries, is very closely allied to the preceding ; but the feet have only two functional toes, the other two toes being placed at some elevation above the ground, and being rudimentary. All the three kinds of teeth are present, but they vary a good deal. The canines always are very large, and in UNGULATA. 517 the males they usually constitute formidable tusks projecting from the sides of the mouth. The molars vary from three to seven on each side of the mouth (3-z^ or j^). The stom- 3 — 3 7 — 7 ach is mostly slightly divided, and is not nearly so complex as in the Ruminants. The snout is truncated and cylindrical, and is capable of considerable movement. The skin is more or less abundantly covered with hair, and the tail is very short, or represented only by a tubercle. Of the true Swine, the best known and most important is the Wild Boar (Sus scrofd], from which it is probable that all our domestic varieties of swine have sprung. The Wild Boar formerly inhabited this country, and is still abundant in many of the forests of Europe. It is often hunted, and the size and sharpness of its canines render it a tolerably formidable adver- sary, as is also its congener, the Indian Hog (Sus Indicus). Another curious form, closely related to the Wild Boar, is the Babyroussa (Sus Babyrtissa), which inhabits the Malayan Pen- insula, and some of the islands of the Indian Archipelago. It is remarkable for the great size and backward curvature of the upper canines. The African Wart-hogs, forming the genus Phacoch&rus, are distinguished by having a fleshy wart under each eye. They inhabit Abyssinia, the Guinea coast, and other parts of Africa. The American Peccaries (Dicotyles) represent the Swine of the Old World. They are singular for having only three toes on the hind-feet, the outer of the two supplemental hoofs being wanting. They are exclusively confined to America, and the commonest species is the Collared Peccary (Dicotyles torquatus). They are not at all unlike small pigs either in their appearance or in their habits, and they are gregarious, generally occurring in small flocks. Forming a kind of transition between the Swine and the true Ruminants, is the extinct group of the Anoplot her idee > from the Lower Tertiary Rocks. The Anoplotheria were slender in form, with long tails, and feet terminated by two hoofed toes each, sometimes with small accessory hoofs. The dentition consisted of six incisors in each jaw, small canines not larger than the incisors, and seven molars on each side, there being no interval or diastema between the molars and the canines. RUMINANTIA. The last section of the Artiodaetyk Ungulates is the great and natural group of the Ruminantia, or Ruminant animals. 5.1 8 MANUAL OF ZOOLOGY. This section comprises the Oxen, Sheep, Antelopes, Giraffes, Deer, Camels, &a, and is distinguished by the following char- acters : — The foot is what is called " cloven," consisting of a symmet- rical pair of toes encased in hoofs, and looking as if produced by the splitting into two equal parts of a single hoof. In addi- tion to these functional toes, there are usually two smaller sup- plementary hoofs placed at the back of the foot. The meta- carpal bones of the two functional toes of the fore-limb, and the metatarsal bones of the same toes of the hind-limb, coalesce to form a single bone, known as the "canon-bone." The stomach is complex, and is divided into several compartments, this being in accordance with their mode of eating. They all, namely, ruminate or " chew the cud" — that is to say, they first swallow their food in an unmasticated or partially-masticated condition, and then bring it up again, after a longer or shorter time, in order to chew it thoroughly. This process of rumination is so characteristic of this group, that it will be necessary to describe the structure of the stomach, as showing the mechanism by which this singular process is effected. The stomach (fig. 199) is divided into four compartments, which are usually so distinct from one another that they have generally been spoken of as so many separate stomachs. The gullet opens at a point situated between the first and second of these cavities or " stomachs." Of these the largest lies on the left side, and is called the "rumen" or "paunch" (fig. 199, r.) This is a cavity of very large capacity, having its interior furnished with numerous hard papillae or warts. It is the chamber into which the food is first received when it is swallowed, and here it is moistened and allowed to soak for some time. The second stomach, placed to the right of the paunch, is much smaller, and is known as the "reticulum" or "honeycomb -bag" (h). Its inner surface is reticulated, or is divided by ridges into a number of hexagonal or many-sided cells, somewhat resem- bling the cells of a honeycomb. The reticulum is small and globular, and it receives the food after it has lain a sufficient time in the paunch. The function of the reticulum is to com- press the partially-masticated food into little balls or pellets, which are then returned to the mouth by a reversed action of the muscles of the oesophagus. After having been thoroughly chewed and prepared for digestion, the food is swallowed for the second time. On this occasion, however, the triturated food passes on into the third cavity (/), which is variously known as the "psalterium," "omasum," or (Scottice) the "many- UNGULATA. 519 plies." The vernacular and the first of these technical names both refer to the fact that the inner lining of this cavity is thrown into a number of longitudinal folds, which are so close as to resemble the leaves of a book. The psalterium opens by a wide aperture into the fourth and last cavity, the " abo- masum" (a), both appearing to be divisions of the pyloric Fig. 199. — Stomach of a Sheep, o Gullet; r Rumen or Paunch ; h Honeycomb-bag or Reticulum ; p Manyplies or Psalterium; a Fourth Stomach or Abomasum. portion of the stomach. The mucous membrane of the abo- masum is thrown into a few longitudinal folds, and it secretes the true acid gastric juice. It terminates, of course, in the commencement of the small intestine — i.e., the duodenum. The intestinal canal of Ruminants, as in most animals which live exclusively upon a vegetable diet, is of great relative length. The dentition of the Ruminants presents peculiarities al- most as great and as distinctive as those to be derived from the digestive system. In the typical Ruminants (e.g,, Oxen, Sheep, Antelopes), there are no incisor teeth in the upper jaw, their place being taken by a callous pad of hardened gum, against which the lower incisors impinge (fig. 200). There are also no upper canine teeth, and the only teeth in the upper jaw are six molars on each side. In the front of the lower jaw is a continuous and uninternipted series of eight teeth, of which the central six are incisors, and the two outer ones are regarded by Owen as being canines. Upon this view, canine teeth are present in the lower jaw of the typical Ruminants, and they are only remarkable for being placed in the same series as the incisors, which they altogether resemble in shape, size, and direction. Behind this continuous series of eight teeth in the lower jaw there is a vacant space, which is followed behind by six molars on each side. 520 MANUAL OF ZOOLOGY. The dental formula, then, for a typical Ruminant animal is — o — o i — * -* — i The departures from this typical formula occur in the Camdida and in some of the Deer. Most of the Deer conform in their Fig. 200. — Skull of a hornless Sheep (after Owen), i Incisors ; c Canines ; in Molars and praemolars. dentition to the above formula, but a few forms (e.g., the Musk- deer) have canine teeth in the upper jaw. These upper canines, however, are mostly confined to the males ; and if they occur in the females, they are of a small size. The denti- tion of the Camelida (Camels and Llamas) is still more aber- rant; there being two upper incisors and upper canines as well. The lower canines also are more pointed and stand more erect than the lower incisors, so that they are easily recognisable. The group of the Ruminantia includes the families of the Camelidce (Camels and Llamas), the Moschida (Musk-deer), the Cervidcz (Deer), the Camdopardalida (Giraffe), and the Cavicornia (Oxenf Sheep, Goats, Antelopes). a. Camelida. — The Camels and Llamas constitute in many respects an aberrant group of the Ruminantia, especially in their dentition, the peculiarities of which have been spoken of above, and need not be repeated here. In their feet, too, the Camelidcz are peculiar. The feet are long and terminate in UNGULATA. 521 only two toes, which are covered by an imperfect nail-like hoof, covering no more than the upper surface of each toe. The two hinder supplementary toes, which are generally pre- sent in the Ruminants, are here altogether wanting ; and the soles of the feet are covered by a callous horny integument upon which the animal walks. The head in all the Camelida is destitute of horns, and the nostrils can be closed at the will of the animal. The true Camels are peculiar to Asia and Africa, and two species are known, distinguished from one another by the possession of a double or single adipose hump on the back. The African or Arabian Camel ( Camelus Dromedarius) is often called the Dromedary, and has only one hump on its back. The two toes are united together by the callous sole ; and the chest, shoulders, and knees are furnished with callous pads, upon which they rest when they lie down. The hump is almost entirely composed of fat, and appears to act as a kind of reserve supply of food, as it is noticed to diminish much in size upon long journeys. The Camel can likewise support a very prolonged deprivation of water, as the paunch is furnished with large cells, which the animal fills when it has access to water, and then makes use of subsequently as occasion may require. The structure of the Camel adapts it admirably for locomotion in the sandy deserts of Arabia and Africa ; and as it is very docile and good-tempered, it is almost exclusively employed as a beast of burden in the countries in which it occurs. The Bactrian Camel (C. Bactrianus) is distinguished by the possession of two humps ; but in other respects it does not differ from the Dromedary. The two species are said to breed together, and the hybrid offspring is stated to be occa- sionally fertile. The place of the Camels is taken in the New World by the Llama^ and Alpaca, with two other nearly-allied forms. These animals form the genus Auchenia, and are in many respects similar to the true Camels. They are distin- guished, however, by having no hump upon the back, and by the fact that the sole of the foot is destitute of a callous pad. The Llamas are chiefly found in Peru and Chili, and consider- able doubt exists as to the number of species. They live in flocks in mountainous regions, and are much smaller than the Camels in size. The true Llama is kept as a domesticated animal, and used as a beast of burden. The Alpaca is still smaller than the Llama, and is not very unlike a sheep, having a long woolly coat. It is partially domesticated, and the wool is largely imported into Europe. 522 MANUAL OF ZOOLOGY. b. Moschidcz. — The second group is that of the Musk-deer, characterised by the total absence of horns in both sexes, and by the presence of canines in both jaws, those in the upper jaw being in the form of tusks in the males, but being much smaller in the females. The true Musk-deer (Moschus moschiferus) is an elegant little animal, which inhabits the elevated plains of central Asia. It is remarkable for the fact that the male has a glan- dular sac on the abdomen, by which the well-known perfume, musk, is secreted. c. Cervidcz. — This family is of much greater importance than that of the Moschida, including as it does all the true Deer. They are distinguished from the other Ruminants chiefly by the nature of the horns. With the single exception of the Reindeer, these appendages are confined to the males amongst the Cervidcz, and do not occur in the females. They do not consist, as in the succeeding group, of a hollow sheath of horn surrounding a central bony core, nor are they permanently re- tained by the animal. On the other hand, the horns, or, as they are more properly called, the antlers, of the Cervidtz are deciduous, and are solid. They are bony throughout, and are usually more or less branched, and they are annually shed and annually reproduced at the breeding season. They increase in size and in the number of branches every time they are reproduced, until in the old males they may attain an enormous size. The antlers are carried upon the frontal bone, and are produced by a process not at all unlike that by which injuries of osseous structures are made good in man. At first the antlers are covered with a sensitive hairy skin ; but as develop- ment proceeds, the vessels of the skin are gradually obliter- ated, and the skin dies and peels off. In all the Deer there is a sebaceous gland, called the "lachrymal sinus," or " larmier," which is placed beneath each eye, and secretes a strongly- smelling waxy substance. The Cervidce. are very generally distributed, but no member of the group has hitherto been discovered in either Australia or South Africa, their place in the latter continent seeming to be taken by the nearly-allied Antelopes (distinguished by their hollow horns). Very many species of Cervidcz are known, and it is not pos- sible to allude to more than two or three of the more familiar and important forms. Three species occur in Britain — namely, the Roebuck, Red -deer, and Fallow-deer, the last being a doubtful native. The Roebuck (Capreolus caprcza) was once very generally distributed over Britain, but is almost confined UNGULATA. $23 to the wilder parts of Scotland at the present day. It is of small size, and the horns are without brow-tynes, and are of small size, with three terminal branches. The Red-deer, or Stag (Cervus elephus] is a much larger species, with well- developed spreading antlers. It is still found in the Lake- district and in Scotland, but it is gradually in process of exter- mination. The Red-deer of this country is represented in North; (America by a still larger species, known as the Wapiti (Cervus Canadensis}. The third British species is the Fallow-deer (Dama platyceros), characterised by the fact that the antlers are palmated — that is, dilated towards their extremities. It is a doubtful native, and is never found in a wild state at the present day. Allied to the Fallow-deer is a gigantic extinct species, the Megaceros Hibernicus, which inhabited Ireland, the Isle of Man, Scotland, and probably the greater part of Europe, up to a comparatively modern date, probably having survived into the human period. It is often, but incorrectly, spoken of as the Irish " Elk," but it is really a genuine Stag. The animal was of very great size, and was furnished with enormous spreading and palmate antlers, which measure from ten to twelve feet between the tips. Of all the Deer, the largest living form is the true Elk (Alces palmatus\ which is generally distributed over the northern parts of Europe, Asia, and America, being often spoken of as the Moose. The antlers in the Elk are of very large size, and are very broad, terminating in a series of points along their outer edges. The only completely domesticated member of the Cervidce is the Reindeer (Cervus tarandus), which is remarkable for the fact that the female is furnished with antlers similar to, but smaller than, those of the males. At the present day the Rein- deer is exclusively confined to the extreme north of Europe and Asia, abounding especially in Lapland. Remains, however, of the Reindeer are known to occur over the greater part of Europe, extending as far south, at any rate, as the Alps, and occurring also in Britain. From this fact, taken along with many others, the existence of an extremely cold climate over the greater part of Europe at a comparatively recent period may be safely inferred. The Reindeer lives chiefly upon moss and a pecu- liar kind of lichen (Lichen rangiferina), and they are extensively used by the Laplanders both as beasts of burden and as sup- plying food. d. Camelopardalidcz. — This family includes only a single living animal — the Camelopardalis Giraffa, or Giraffe — some- times called the Camelopard, from the fact that the skin is 524 MANUAL OF ZOOLOGY. spotted like that of the Leopard, whilst the neck is long, and gives it some distant resemblance to a Camel. There are no upper canines in the Giraffe, and both sexes possess two small frontal horns, which, however, are persistent, and remain per- manently covered by a hairy skin. The neck is of extraordi- nary length, but, nevertheless, consists of no more than the nor- mal seven cervical vertebrae. The fore-legs appear to be much longer than the hind-legs, and all are terminated by two toes each, the supplementary toes being altogether wanting. The tongue is very long and movable, and is employed in stripping leaves off the trees. The Giraffe is the largest of all the Ruminants, measuring as much as from fifteen to eighteen feet in height. It is a harmless and inoffensive animal, but defends itself very effectually, if attacked, by kicking. It is found in Nubia, Abyssinia, and the Cape of Good Hope. Remains of gigantic Ruminants allied to the Giraffe have been found in France and Greece (Helladot her turn} ; but the Sivatherium, sometimes referred to this family, appears to have been more nearly allied to the true Antelopes. e. Cavicornia. — The last family of the Ruminants is that of the Cavicornia or Bovidcz, comprising the Oxen, Sheep, Goats, and Antelopes. This family includes the most typical Rumi- nants, and those of most importance to man. The upper jaw in all the Cavicornia is wholly destitute of incisors and canines, the place of which is taken by the hardened gum, against which the lower incisors bite. There are six incisors and two canines in the lower jaw, placed in a continuous series, and the molars are separated by a wide gap from the canines. There are six molars on each side of each jaw. Both sexes have horns, or the males only may be horned, but in either case these appendages are very different to the " antlers " of the Cervida. The horns, namely, are persistent, instead of being deciduous, and each consists of a bony process of the frontal bone — or " horn-core " — covered by a sheath of horn. The feet are cleft, but are furnished with accessory hoofs placed on the back of the foot. The Cavicornia comprise the three families of the Antilopidce, Ovidce, and Bovida. The Antelopes form an extremely large section, with very many species. They are characterised by their slender deer-like form, their long and slender legs, and their simple cylindrical or twisted horns, which are usually confined to the males, but sometimes occur in the females as well. The Antelopes must on no account be confounded with the true Deer, to which they present many points of similarity. Th e structure of the horns, however, is quite sufficient to dis- UNGULATA. 525 tinguish them. The Antelopes are especially numerous, both in individuals and in species, in Africa, in which country they appear to take the place of the true Deer (only one species of Deer being indigenous to Africa). Amongst the better-known African species of Antelopes are the Springbok, Hartebeest, Gnu, Eland, and Gazelle. The only European Antelope is the Chamois (Rupicapra tragus), which inhabits the Alps and other mountain-ranges of southern Europe. The Sheep and Goats (Ovidce) have mostly horns in both sexes, and the horns are generally curved, compressed, and turned more or less backwards. The body is heavier, and the legs shorter and stouter than in the true Antelopes. In the true Goats (Capra) both sexes have horns, and there are no lachrymal sinuses. The throat is furnished with long hair, forming a beard, and this appendage is usually present in both sexes, though sometimes in the males only. The goats live in herds, usually in mountainous and rugged districts. The do- mestic Goat ( Capra hircus) is generally believed to be a descen- dant of a species which occurs in a wild state in Persia and in the Caucasus (the " Paseng," or Capra agagrus). The true sheep (Ovis) are destitute of a beard, and the horns are gener- ally twisted into a spiral. Horns may be present in both sexes, or in the males only. Lachrymal sinuses are almost in- variably present Numerous varieties of the domestic Sheep (Ovis aries)a.re known, but it is not certainly known from what wild species these were originally derived. The Merino Sheep (a Spanish breed) and the Thibet Sheep are particularly cele- brated for their long and fine wool. With the exception of one species (the Big-horn, Ovis montano), all the Sheep appear to be originally natives of the Old World. The true Oxen (Bovida) are distinguished by having simply rounded horns, which are not twisted in a spiral manner. There are no lachrymal sinuses. Most of the Oxen admit of being more or less completely domesticated, and some of them are amongst the most useful of animals, both as beasts of burden and as supplying food. The parent-stock of our nu- merous breeds of cattle is not known with absolute certainty ; the nearest approach to British Wild Cattle being a celebrated breed which is still preserved in one or two places. These " Chillingham Cattle" are a fine wild breed, which at one time doubtless existed over a considerable part of Britain. They are pure white, with a black muzzle, the horns white, tipped with black. Another large Ox, which formerly existed in Brit- ain, and abounded over the whole of Europe, is the Aurochs or Lithuanian Bison (JBos bison). The Aurochs is of very large 526 MANUAL OF ZOOLOGY. size, considerably exceeding the common Ox in bulk. It still occurs in the forests of the Caucasus in a wild state, but it no longer occurs wild in Europe, if we except a herd maintained by the Czar in one of the forests of Lithuania. Nearly allied to the Aurochs is the American Bison or Buffalo (Bison Ameri- canus). This species formerly occurred in innumerable herds in the prairies of North America, but it has been gradually driven westwards, and has been much reduced in numbers. Two other very well known forms are the Cape Buffalo (Bu- balus Coffer) and the common Buffalo (Bubalus bubalis). The former of these occurs in southern and eastern Africa, and the latter is domesticated in India and in many parts of the south of Asia. The horns in both species are of large size, and their bases are confluent, so that the forehead is protected by a bony plate of considerable thickness. The last of the Oxen which deserves notice is the curious Musk-ox (Ovibos moschatus). This singular animal is at the present day a native of Arctic America, and is remarkable for the great length of the hair. It is called the Musk-ox, because it gives out a musky odour. Like the Reindeer, the Musk-ox had formerly a much wider geographical range than it has at present ; the conditions of climate which are necessary for its existence having at that time extended over a very much larger area than at present. The Musk-ox, in fact, in Post- tertiary times is known to have extended over the greater part of Europe, remains of it occurring abundantly in certain of the bone-caves of France. CHAPTER LXXVIII. HYRACOIDEA AND PROBOSCIDEA. ORDER VII. HYRACOIDEA. — This is a very small order which has been constituted by Huxley for the reception of two or three little animals, which make up the single genus Hyrax. These have been usually placed in the immediate neighbour- hood of the Rhinoceros, to which they have some decided affinities, and they are still retained by Owen in the section of the Perissodactyle Ungulates. The order is distinguished by the following characters : — There are no canine teeth, and the incisors of the upper jaw are long and curved, and grow from permanent pulps, as they PROBOSCIDEA. do in the Rodents (such as the Beaver, Rat, &c.) The molar teeth are singularly like those of the Rhinoceros. According to Huxley, the dental formula of the aged animal is — c . m 2—2 o—o 4—4 3—3 The fore-feet are tetradactylous, the hind-feet tridactylous, and all the toes have rounded hoof-like nails, with the ex- ception of the inner toes of the hind-feet, which have an obliquely-curved nail. There are no clavicles. The nose and ears are short, and the tail is represented by a mere tubercle. The placenta is deciduate and zonary, whereas in the Ungulates it is non-deciduate. Two or three species of Hyrax are known, but they resemble one another in all essential particulars. They are all gregarious little animals, living in holes of the rocks, and capable of domestication. One species is said to be arboreal in its habits. The " coney" of Scripture is believed to be the Hyrax Syriacus, which occurs in the rocky parts of Syria and Palestine. Another species — the Hyrax Capensis — occurs commonly in South Africa, and is known by the colonists as the " badger." ORDER VIII. PROBOSCIDEA. — The eighth order of Mammals is that of the Proboscidea, comprising no other living animals except the Elephants, but including also the extinct Mastodon and Deinotherium. The order is characterised by the total absence of canine teeth ; the molar teeth are few in number, large, and trans- versely ridged or tuberculate ; incisors are always present, and grow from persistent pulps, constituting long tusks (fig. 201). In living Elephants there are two of these tusk-like incisors in the upper jaw, and the lower jaw is without incisor teeth. In the Deinotherium this is reversed, there being two tusk-like lower incisors and no upper incisors. In the Mastodons, the incisors are usually developed in the upper jaw, and form tusks, as in the Elephants, but sometimes there are both upper and lower incisors, and both are tusk-like. The nose is prolonged into a cylindrical trunk, movable in every direction, highly sensitive, and terminating in a finger-like prehensile lobe (fig. 201). The nostrils are placed at the extremity of the proboscis. The feet are furnished with five toes each, but these are only indicated externally by the divisions of the hoof. The feet are furnished with a thick pad of integument, forming the palms of the hand and the soles of the feet. There are no clavicles. The testes are abdominal throughout life. There are two teats, and these are placed upon the chest. The placenta is deciduate and zonary. 528 MANUAL OF ZOOLOGY. The recent Elephants are exclusively confined to the tropical regions of the Old World, in the forests of which they live in herds. Only two living species are known — the Asiatic Elephant (Elephas Indiais), and the African Elephant (E. Africanus). There can be no doubt, however, but that the Mammoth (Elephas primigenius] existed in Europe within the human period. Fig. 201. — Skull of the Indian Elephant (Elephas Indicus). i Tusk-like upper in- cisors ; m Lower jaw, with molars, but without incisors ; « Nostrils, placed at the end of the proboscis. (After Owen)^ In both the living Elephants the " tusks" are formed by an enormous development of the two upper incisors. The lower incisors are absent, and there are no other teeth in the jaws except the large molars, which are usually two in number on each side of each jaw. The molar teeth are of very large size, and are composed of a number of transverse plates of enamel united together by dentine. In the Indian Elephant the transverse ridges of enamel are narrow and undulating, whilst in the African Elephant they enclose lozenge-shaped intervals. The Indian Elephant is the only species which is now caught and domesticated, and as it will not breed in captivity, the demand for it is supplied entirely by the capture of adult wild PROBOSCIDEA. 529 individuals, which are taken chiefly by the assistance of those which have been already tamed. The Indian Elephant is dis- tinguished by its concave forehead, its small ears, and the characters of the molars. The African Elephant, on the other hand, has a strongly convex forehead and great flapping ears. The African Elephant is chiefly hunted for the sake of its ivory, and there is too much reason to believe that the pursuit will ultimately end in the destruction of these fine animals. A great deal, however, of the ivory of commerce comes from Siberia, and is really derived from the tusks of the now extinct Mammoth, which formerly inhabited the north of Asia in great numbers. The Elephants are all phytophagous, living almost entirely on the foliage of shrubs and trees, which they strip off by means of the prehensile trunk. As the tusks prevent the animal from drinking in the ordinary manner, the water is sucked up by the trunk, which is then inserted into the mouth, into which it empties its contents, Many species of fossil Elephants are known, but the most familiar of them is the Mammoth (Elephas primigenius). This enormous animal is now wholly extinct, but it formerly abounded in the northern parts of Asia and over the whole of Europe. It occurred also in Britain, and unquestionably existed in the earlier portion of the human period, its remains having been found in a great number of instances in connec- tion with human implements. From its great abundance in Siberia, it might have been safely inferred that the Mammoth was able to endure a much colder climate than either of the living species. This inference, however, has been rendered a certainty by the discovery of the body of more than one Mammoth embedded in the frozen soil of Siberia. These specimens had been so perfectly preserved that even micro- scopical sections of some of the tissues could be made; and in one case even the eyes were preserved. From these speci- mens we know that the body of the Mammoth was covered with long woolly hair. Closely allied to the true Elephants are the Mastodons, characterised by the fact that the crowns of the molar teeth have nipple -shaped tubercles placed in pairs. Generally speaking, the two upper incisors formed long curved tusks, as in the Elephants, but in some cases there were two lower incisors as well. The various species of Mastodon all belong to the later Tertiary and Post-tertiary periods. The last of the Proboscidea is a remarkable extinct animal, VOL. II. 2 L 530 MANUAL OF ZOOLOGY. the Deinotherium. This extraordinary animal has hitherto only been found in Miocene de- posits, and little is known of it except its enormous skull. Mo- lars and praemolars were present in each jaw, and the upper jaw was destitute of canines and in- cisors. In the lower jaw were two very large tusk-like incisors, which were not directed forwards as in the true Elephants, but were bent abruptly downwards (fig. 202). The animal must have attained an enormous size, and it is probable that the curved tusks were used • \ • ••• either in digging up roots or in mooring the animal to the banks of rivers, for it was probably aquatic or semi-aquatic in its habits. Fig. 202. — Skull of Deinotherium CHAPTER LXXIX. CARNIVORA. ORDER IX. CARNIVORA. — The ninth order of Mammals is that of the Carnivora, comprising the Feres or feeasts, of Prey, along with the old order of the Pinnipedia, or Seals and Wal- ruses, these latter being now universally regarded as merely a group of the Carnivora modified to lead an aquatic life. The Carnivora are distinguished by always possessing two sets of teeth, which are simply covered by enamel, and are always of three kinds — incisors, canines, and molars — differing from one another in shape and size. The incisors are generally •2 •? J I — — (except in some seals); the canines are always - — and are invariably much larger and longer than the incisors. The praemolars and molars are mostly furnished with cutting or trenchant edges ; but they graduate from a cutting to a tuber- culate form, as the diet is strictly carnivorous, or becomes more or less miscellaneous. In the typical Carnivores (such as the Lion and Tiger), the last tooth but one in the upper jaw and the last tooth in the lower jaw are known as the "carnassial" or "sectorial" teeth, having a sharp cutting edge CARNIVORA. 531 adapted For dividing flesh. A varying number, however, of the molars and pragmolars may be " tuberculate," their crowns being adapted for bruising rather than cutting. In all the Carnivora the clavicles are either altogether want- ing, or are quite rudimentary. The toes are provided with sharp curved claws. The teats are abdominal; and the pla- centa is deciduate and zonular. The order Carnivora is divided into three very natural sections : — Section L Pinnigrada or Pinnipedia. — This section com- prises the Seals and Walruses, in which the fore and hind limbs are short, and are expanded into broad webbed swim- ming-paddles (fig. 203, B.) The hind-feet are placed very far back, nearly in a line with the axis of the body, and they are more or less tied down to the tail by the integuments. Section II. Plantigrada. — This section comprises the Bears and their allies, in which the whole, or nearly the whole, of the foot is applied to the ground, so that the animal walks upon the soles of the feet (fig. 203, A.) Section III. Digitigrada. — This section comprises the Lions, Tigers, Cats, Dogs, &c., in which the heel of the foot is raised entirely off the ground, and the animal walks upon the tips of the toes (fig. 203, C.) Fig. 203.— Feet of Carnivora. (after Owen). A, Plantigrada, Foot of Bear; B, Pinnigrada, Hind-feet of Seal ; C, Digitigrada, Foot of Lion. SECTION I. PINNIGRADA or PINNIPEDIA. — This section of the Carnivora comprises the amphibious Seals and Walruses, which differ from the typical Carnivores merely in points con- nected with their semi-aquatic mode of life. The body in 532 MANUAL OF ZOOLOGY. these forms is elongated and somewhat fish-like in shape, covered with a short dense fur or harsh hairs, and terminated behind by a short conical tail. All the four limbs are present, but are very short, and the five toes of each foot are united together by a membrane, so that the feet form powerful swimming-paddles. The hind-feet are of large size, and are placed far back, their axis nearly coinciding with that of the body (figs. 203, 204). From this circumstance, and from the fact that the integument often extends between the hind-legs and the sides of the short tail, the hinder end of the bocly forms an admirable swimming-apparatus, similar in its action to the horizontal tail-fin of the Cetacea and Sirenia. The tips of the toes are furnished with strong claws, but their powers of terrestrial locomotion are very limited. The ears are of small size, and are mostly only indicated by small apertures, which the animal has the power of closing when under water. The bones are light and spongy, and beneath the skin is a layer of fat or blubber. The dentition varies, but teeth of three kinds are always present, in the young animal at any rate. The canines are always long and pointed, and the molars are generally furnished with sharp cutting edges. , Fig. 204.— The Greenland Seal (Phoca. Grcenlandica.) The section Pinnigrada includes the two families of the Seals (Phocida) and Walruses (Trichecida). The Seals are distinguished by having incisor teeth in both jaws, and by the fact that the canine teeth are not disproportionately developed. They form a very numerous family, of which species are found in almost every sea out of the limits of the tropics. They abound, however, especially in the seas of the Arctic and Antarctic regions. They live for the most part upon fish, and CARNIVORA. 533 when awake, spend the greater part of their time in the water. The body is covered with a short fur, interspersed with long bristly hairs ; and the lips are furnished with long whiskers, which act as organs of touch. The Seals are very largely captured for the sake of their blubber. The only common British Seal is the Phoca mtulina, which occurs not uncommonly on the northern shores of Scotland. It is yellowish-grey in colour, and measures from three to five feet in length. Other Seals attain a much greater length — the Great Seal measuring from eight to ten feet, and the Bottle- nosed Seal reaching a length of from twenty to twenty-five feet. The only Seals which possess external ears constitute the genus Otaria, and are almost exclusively confined to the seas of the southern hemisphere. The second family of the Pinnigrade Carnivores is that of the Trichetidce, comprising only the Walrus or Morse (Trick- ecus rosmarus). The chief peculiarity by which the Walrus is Fig. 205.— Skull of the Walrus (Trichecus rosmarus (after Owen), z Tusk-like upper incisors. distinguished from the true Seals is found in the dentition. According to Owen, there are six incisors in the upper jaw and four in the lower ; but these are only present in the young animal, and soon disappear, with the exception of the outer- most pair of upper incisors. The upper canines are enor- mously developed, growing from persistent pulps, and consti- 534 MANUAL OF ZOOLOGY. tuting two large pointed tusks, which attain a length of over fifteen inches (fig. 205). The direction of the tusks is down- wards and slightly outwards, and they project considerably below the chin. The adult animal has usually three simple molars with flat crowns behind the tusks in the upper jaw; and four similar teeth on each side of the lower jaw ; but the first of these has been regarded as a lower canine. Except as regards its dentition, the Walrus agrees in all essential respects with the Seals. It is a large and heavy animal, attaining a length of from ten to fifteen feet or up- wards. The body is covered with short brownish or yellowish hair, and the face bears many long stiff bristles. There are no external ears. The chief use of the tusk -like canines appears to be that of assisting the unwieldy animal to get out of the water upon the ice ; but they doubtless serve as weapons of offence and defence as well. The Walrus is hunted by whalers, both for its blubber, which yields an excellent oil, and for the ivory of the tusks. It is found, living in herds, in the Arctic seas, being especially abundant at Spitzbergen and Nova Zembla. SECTION II. PLANTIGRADA. — The Carnivorous animals be- longing to this section apply the whole or the greater part of the sole of the foot to the ground (fig. 203, A) ; and the por- tion of the sole so employed is destitute of hairs in most instances (the sole is hairy in the Polar Bear). The typical family of the Plantigrade Carnivora is that of the Ursida or Bears, in which the entire sole of the foot is ap- plied to the ground in walking. The Ursidcz are much less purely carnivorous than the majority of the order, and in ac- cordance with their omnivorous habits, the teeth do not exhibit the typical carnivorous characters. The incisors and canines have the ordinary carnivorous form, but the " carnassial " or sectorial molar has a tuberculate crown instead of a sharp cutting edge. The dental formula is — 3—3 i— i 4—4 3—3 The claws are large, strong, and curved, but are not retrac- tile. The tongue is smooth ; the ears small, erect, and rounded ; the tail short ; the nose forms a movable truncated snout ; and the pupil is circular. As shown by their smooth tongues and tuberculate molars, the Bears are not peculiarly or strictly carnivorous. They eat flesh when they can obtain it, but a great part of their food is of a vegetable nature. CARN1VORA. 535 The Bears are very generally distributed over the globe, Australia alone having no representative of the family. The common Brown Bear ( Ursus Arctos) was at one time an inhabit- ant of this country, and also existed over the whole of Europe. At the present day the Brown Bear is only found in the great forests of the north of Europe and in Asia. It feeds on roots, fruits, honey, insects, and, when it can obtain them, upon other Mammals. It attains a great age, and hybernates during the winter months. Very nearly allied to the Brown Bear is the Black Bear of America ( Ursus Americanus). Both are of some commercial value, being hunted for the sake of their skins, fat, and tongues. A much larger American species is the Grizzly Bear ( Ursus ferox\ found in many parts of the Ameri- can continent. It is about twice as large as the ordinary Bear, but it is said to subsist to a great extent upon vegetable food, such as acorns. The most remarkable, however, of the bears is the great White Bear (Thalassarctos maritimus], which is exclusively a native of the Arctic regions. It is a very large and powerful animal, the fur of which is quite white. The paws are very long, and the soles of the feet are covered with coarse hair, giving the animal a firm foothold upon the ice. The Polar Bear differs from the other Ursida in being exclu- sively carnivorous, since vegetable food would be wholly un- attainable. It is as much at home in the water as on land, and lives chiefly upon seals and fish, and upon the carcases of Cetaceans. It is a singular fact that the bones of a bear — the Ursus spelmis or Cave Bear — have been found in Britain and in many parts of Europe, along with the bones of other Carnivora, such as the Cave Lion and Cave Hyaena. The Ursus spelceus was a larger and more powerful animal than even the Polar Bear, and there can be no doubt that it existed in the earlier portion of the human period. Nearly allied to the true bears are several small animals, of which the Racoons (Procyoii), the Coati (Nasud), the Wah (Ailurus\ and the Kinkajou (Cercoleptes) are the best known. The Racoons are natives of tropical and northern America, and have a decided external resemblance to the Bears. They have tolerably long tails, however, and sharp muzzles. The commonest species is the Procyon lotor of North America, which derives its specific name from its habit of washing its food before eating it. The place of the Racoon is taken in India by the Wah (Ailurus fulgens), which inhabits northern Hindo- stan. It is about the size of a large domestic cat, and is very prettily coloured, being chestnut brown above, and black in- 536 MANUAL OF ZOOLOGY. feriorly, with a white face and ears. The Kinkajous (Cerco- leptes) are inhabitants of South America, and as is the case with so many of the animals of this continent, they are adapted for an arboreal life, to which end their tails are prehensile. The Coatis (Nasua) are very closely allied to the Racoons, and are exclusively confined to the American continent. All the above-mentioned little animals (with the exception of the Wah) present a singularly close resemblance to the Lemurs of the Old World, and appear to be their representatives in the western hemisphere. The only remaining family of the Plantigrada is that of the Melidce or Badgers, characterised by their elongated bodies and short legs, and by the fact that the carnassial tooth has a partly cutting edge, and is not wholly tuberculate as in the Bears. The common Badger (Meles taxus), which may be regarded as the type of this group, occurs in Britain, and is one of the most inoffensive of animals. It is nocturnal in its habits, and is a very miscellaneous feeder, not refusing anything edible which may come in its way, though living mainly on roots and fruits. The Badger burrows with great ease, and can bite very severely. The Glutton (Gulo Arcticus\ often called the Wolve- rine, is of common occurrence in the northern parts of Europe, Asia, and America. It is from two to three feet in length, and though doubtless a tolerably voracious animal, it is certainly not so much so as to deserve the name of Glutton. The Ratels or Honey-badgers (Mellivord) are much like the com- mon Badger in their habits and appearance, but they get their name from their fondness for honey. They are natives of southern and eastern Africa. SECTION III. DIGITIGRADA. — In this section of the Carnivora the heel is raised above the ground, with the whole or the greater part of the metacarpus, so that the animals walk more or less completely on the tips of the toes (fig. 203, C). No absolute line, however, of demarcation can be drawn between the Plantigrade and Digitigrade sections of the Carnivora, since many forms (e.g., Mustelidce and Viverridce] exhibit transi- tional characters, and it has even been proposed to place these in a separate section, under the name of Semi-plantigrada. The first family of the Digitigrada is that of the Mustelidce or Weasels, including a number of small Carnivores, with short legs, elongated worm-like bodies, and a peculiar gliding mode of progression (hence the name of Vermiformes, sometimes applied to the group). Amongst the best known of the Mus- telidce. are the common Weasel (Mustela vulgar is) , the Pole-cat (Mustela putorius\ and the Ferret, the last being only an albino CARNIVORA. 537 variety of one of the Pole-cats. Many of the Mustelidce are of great commercial importance, furnishing beautiful and highly- valued furs. Amongst these are the Ermine (Mustela erminea) and the Sable (Mustela zibellina). Almost all the Weasels have a very disagreeable odour, pro- duced by the secretion of greatly-developed and modified sebaceous glands, placed in the neighbourhood of the anus, and known as the anal glands. In this respect, however, the nearly-allied genus Mephitis, comprising the American Skunk, is facile princes. The Skunk is a pretty little animal, with a long bushy tail, and when unmolested, it is perfectly harmless. If pursued or irritated, however, it has the power of ejecting the secretion of the anal glands to a greater or less distance with considerable force. The odour of this secretion is so powerful and persistent that no amount of washing will remove it from a garment, and its characters are said to be of the most intensely disagreeable description. Also belonging to the family of the Mtistelidce and very nearly allied to the Weasels, are the Otters (Lutrd), distinguished by the possession of webbed feet adapted for swimming. The common Otter (Lutra vulgaris) is a native of Britain, frequent- ing the banks of streams and lakes. It lives upon fish, and is highly destructive to Salmon. The second family of the Semi-plantigrade Carnivores is that of the Viverridcz, the Civets and Genettes. They are all of moderate size, with sharp muzzles and long tails, and more or less striped, or banded, or spotted. The carnassial molar is trenchant ; the canines are long, sharp, and pointed ; and the tongue is roughened by numerous prickly papillae. The claws are semi-retractile, and the pupils can contract, on exposure to light, till they resemble a mere line. In most of their charac- ters, therefore, the Civets are much more highly carnivorous than are any of the preceding families, and they approach in many respects'very close to the typical group of the Digitigrada (viz., the FelidcR] ; having especially very close affinities with the Hyaenas. All the species of the family are furnished with anal glands, which secrete the peculiar fatty substance known as " civet." The true Civet-cat is the Viverra civetta, a native of Africa, It is a small nocturnal animal, which climbs trees with facility, and feeds chiefly upon small mammals, reptiles, and birds, but also upon roots and fruits. It furnishes the greater part of the " civet " of commerce, which was formerly in great repute both as a perfume and as a medicinal agent. The Genette ( Viverra genetta) is very closely related to the preceding, and is a native 53$ MANUAL OF ZOOLOGY. of Africa and southern Europe, being not uncommonly do- mesticated and kept like a cat. Another nearly-allied species is the Ichneumon (Herpestes), which is kept as a domestic ani- mal in Egypt, and lives upon Snakes, Lizards, the eggs of the Crocodile, and small Mammals. Forming a transition between the Viverrida and the Felidce. is the family of the Hycenida, distinguished by the fact that, alone rof all the Carnivora, both pairs of feet have only four toes each. The hind-legs are shorter than the fore-legs, so that the trunk sinks towards the hind-quarters, and the tail is short. The tongue is rough and prickly. The head is extremely broad, the muzzle rounded, and the muscles of the jaw extremely powerful and well developed. The claws are non- retractile. All the molars are trenchant except the last upper molar, which is tuberculate. There are two well-known species of Hyaena, and the whole group is exclusively confined to the Old World. The best known species is the Striped Hyaena (Hy&na striatd), which is found in North Africa, Asia Minor, Arabia, and Persia. It is an ill-conditioned ferocious beast, but will not attack man unless provoked. The Spotted Hyaena (H. crocutd) occurs solely in Africa, being especially abundant in Cape Colony. If the so-called Aardwolf (Pretties} is to be placed amongst the Hyaenas, as is generally done, then the characters to be drawn from the feet are not invariable; since this singular animal has the fore-feet furnished with five toes, whilst the hind-feet are tetradactylous (as is the case in the Dogs). An extinct Hyaena, considerably larger than either of the living forms, formerly existed in Britain and in various parts of Europe. It is known as the Cave Hyaena (H. speltzd), its remains having been principally found in caves. The next family is that of the Canida, comprising the Dogs, Wolves, Foxes, and Jackals. The members of this family are characterised by having pointed muzzles, smooth tongues, and non-retractile claws. The fore-feet have five toes each, the hind-feet have only four. The molar teeth are • — , 7 — 7 sometimes —^-, and of these, two or three on each side are tuberculate. The true Dogs (/. are almost certainly referable to the Marsupialia; the latter seeming to be most nearly related to the living Myrmecobius, whilst the former finds its nearest living ally in the Opossums of America. The Stereognathus of the Stonesfield Slate is in a doubtful position. It may have been Marsupial, but, upon the whole, Professor Owen is inclined to believe that it was placental, hoofed, and herbivorous. (cfe Fig. 214. — Oolitic Mammals, natural size. i. Lower jaw and teeth of Phascolotheriunt / 2. of Triconodon ; 3. of Amphitherium ; 4. of Plagiaulax. With the occurrence of small Marsupials in England within the Oolitic period, it is interesting to notice how the fauna of that time approached in other respects to that now inhabiting Australia. At the present day, Australia is almost wholly tenanted by Marsupials ; upon its land-surface flourish Arau- carice and Cycadaceous plants, and in its seas swims the Port- Jackson Shark ( Cestracion Philippt) ; whilst the Molluscan genus Trigonia is nowadays exclusively confined to the Aus- tralian coasts. In England at the time of the deposition of the Stonesfield Slate, we must have had a fauna and flora very closely resembling what we now see in Australia. The small VOL. II. 2 N 562 MANUAL OF ZOOLOGY. Marsupials, Amphitherium and Phascolotherium, prove that the Mammals were the same in order ; cones of Araucarian pines, with tree-ferns and fronds of Cycads occur throughout the Oolitic series ; spine-bearing fishes, like the Port- Jackson Shark, are abundantly represented by genera such as Acrodus and Strophodus ; and, lastly, the genus Trigonia, now ex- clusively Australian, is represented in the Stonesneld Slate by species which differ little from those now existing. In the Middle Purbeck beds (Upper Oolite), where fourteen species of Mammals are known to exist, it is probable that all were Marsupial. All the Purbeck Mammalia were of small size, the largest being no bigger than a pole-cat or hedgehog. They form the genera Plagiaulax, Triconodon, and Galestes, of which Plagiaulax is believed to be most nearly allied to the living Kangaroo-rat (Hypsiprymnus) of Australia. In the Tertiary series of rocks Marsupials are of rare occur- rence j but an Opossum, closely allied to the existing American forms, has been discovered in the Eocene Rocks of France (Gypseous series of Montmartre), and has been named the Didelphys gypsorum. The next occurrence of Marsupials is in the later Tertiary (Pliocene) and in the Post-tertiary epoch ; and here they are represented by some very remarkable forms. The remains in question have been found in the bone-caves of Australia — the country in which Marsupials now abound above every other part of the globe ; and they show that Australia, at no distant geological period, possessed a Marsupial fauna, much re- sembling that which it has at present, but comparatively of a much more gigantic size. In the remains from the Australian bone-caves almost all the most characteristic living Marsupials of Australia and Van Diemen's Land are represented ; but the extinct forms are usually of much greater size. We have Wombats, Phalangers, Flying Phalangers, and Kangaroos, with carnivorous Marsupials resembling the recent Thyladnus and Dasyurus. The two most remarkable of these extinct forms are Diprotodon and Thylacoleo. In most essential respects Diprotodon resembled the Kangaroos, the dentition, especially, showing many points of affinity. The hind-limbs, however, of Diprotodon were by no means so disproportionately long as in the Kangaroos. In size Diprotodon must have many times exceeded the largest of the living Kangaroos, since the skull measures three feet in length (fig. 215.) Thylacoleo was a carnivorous and predacious Marsupial, equally gigantic when compared with living forms. Thylacoleo, in fact, must have been, on a moderate estimate, at least as large as a Lion; DISTRIBUTION OF MAMMALS IN TIME. 563 the largest living carnivorous Marsupial being no larger than a shepherd's dog. The flesh-tooth or earnassial molar of Thylacoleo measures two inches and a quarter across, or very nearly double the measurement of the same tooth in the largest existing Lion. Order III. Edentata. — The Edentates, like the Marsupials, are singularly circumscribed at the present day. No member of the order is at^the present Fig. 2iS.- day indigenous in Europe. Tropical Asia and Africa have the Scaly Ant-eaters or Pangolins ; and in Africa occurs the Edentate genus Orycteropus. South America, however, is the metropolis of the Edentata, the order being there represented by the Sloths, the Armadillos, and the true Ant-eaters. It is also in South America that by far the greater number of extinct Edentates have been found ; and, as in the case of the Australian Marsupials, the fossil forms are gigantic in size compared with their living representatives. The Sloths (Bradypodida) of the present day were repre- sented in Post-tertiary times by a group of gigantic forms referable to the genera Mylodon, Megalonyx, and Megatherium. Fig. 216.— Megatherium. From the Upper Tertiaries of South America (Pleistocene). \ Of these, Mylodon attained a length of eleven feet, and Mega- therium (fig. 216) was eighteen feet in length, with bones as massive, or more so, than the Elephant. In the same way, the little banded Armadillos of South America were formerly represented by gigantic species, con- stituting the genus Glyptodon. The Giyptodons (fig. 217) differed from the living Armadillos in having no bands in their armour, 564 MANUAL OF ZOOLOGY. so that they must have been unable to roll themselves up. It is rare at the present day to meet with any Armadillo over two or three feet in length ; but the length of the Glyptodon clavipes, from the tip of the snout to the end of the tail, was more than nine feet. Fig. 217. — Glyptodon clavipes. Pleistocene deposits of South America. All these gigantic South American Edentates occur in Post- tertiary deposits. Older, however, than any of these is the Macr other ium. This is a gigantic Edentate, intermediate in some respects between the Pangolins and Orycteropus, and found in certain lacustrine deposits of France, of Miocene age. Order IV. Sirenia. — This order contains only the living Manatees and Dugongs, and is of little geological importance. The Halitherium, however, of the Eocene, Miocene, and Plio- cene Rocks is a large form, intermediate between the African Manatee and the Dugong. Order V. Cetacea. — The Cetacea, also, are of little geological importance. Remains of Dolphins (Ziphius) and of Whales (Balanodori) are found in Miocene deposits; and numerous ear-bones of Whales occur in the Red Crag of Suffolk (Plio- cene). The most remarkable, however, of the extinct Cetacea is the Zeuglodon of the American and Maltese Miocene de- posits. This was an enormous toothed Whale, about seventy feet in length ; but unlike any of existing Cetaceans, it had the posterior teeth implanted by two distinct fangs or roots. By Owen, Zeuglodon is regarded as the type of a distinct family, intermediate between the Cetacea and the Sirenia. Order VI. Ungulata. — The Hoofed Mammals are repre- sented in past time by so many extinct forms that it will be wholly impossible here to do more than merely allude to some of the more important genera. The earliest-known Ungulates occur in the Eocene Rocks, where the order is represented by very numerous and interest- ing forms, the more important of which are Pliolophus, Palczo- therium, and Anoplotherium. DISTRIBUTION OF MAMMALS IN TIME. 565 Of the section of the Ungulates comprising the living Horse, Zebra, and Ass (Solidungula), the earliest fossil example is the Hipparion of the Miocene Rocks. This genus differed from the existing Equidcz in the presence of two small toes with hoofs, one on each side of the single functional toe, which alone remains in living horses. In the Pliocene period appear, for the first time, remains of horses which, like the present form, possessed only a single toe encased in a single hoof. It is interesting to observe that one of the Pliocene horses (Equus curvidens) occurs in South America; though this continent cer- lainly possessed no native horse at the time of its discovery by the Spaniards. QfiheJtAmv&rufa, a hornless species (Acerotheriuni) occurs in Miocene and Pliocene strata ; but the best-known fossil species is the two-horned woolly Rhinoceros (R. tichorhinus). This curious species occurs in Post-pliocene deposits, and must have ranged over the greater part of Europe. It was adapted to a temperate climate, and, like the Mammoth, possessed a thick covering of mixed wool and hair. This has been demonstrated by the discovery of a frozen carcass in Siberia. Of the Hippopotamida the earliest-known species is the Hippopotamus major of the Pliocene period. This form agreed in all essential respects with the living H. amphibius of Africa, but it must have ranged over the whole of southern Europe. Of the Suida, or Pig tribe, various extinct forms are known from the Eocene and Miocene Rocks, where the family is represented by the genera Cheer opotamus, Anthracotherium, Hyopotamus, and Hippohyus. As regards the past existence of the Ruminants, the Cervidce, or Stag tribe, is represented, for the first time in the Miocene period, by the genus Dorcatherium. The best-known species, however, of this family is the Megaceros Hibernicus, or so-called Irish Elk (fig. 218), which is not a true Elk, but is intermediate between the Fallow-deer and Reindeer. Of the Giraffe family — represented at the present day by a single African species — a form has been discovered in the Pliocene Rocks of Greece, and has been described under the name of Helladotherium. Somewhat similar forms have been found in the Pliocene de- posits of the Sivalik Hills of India. The earliest-known Antelopes are Miocene, but the largest and most extraordinary fossil examples of this family are two gigantic four-horned Antelopes, which occur in the Pliocene strata of the Sivalik Hills of India, and have been described under the names of Sivatherium and Bramatherium. The Bovidcz, or Ox tribe, has hitherto only occurred in rocks 566 MANUAL OF ZOOLOGY. not older than the Pliocene or Post-pliocene. At this latter period England alone possessed four oxen — viz., the Lithua- Fig. 218.— The Irish Elk (Megaceros Hibemicus). nian Aurochs (Bos bison or Bos priscus\ the Wild Bull or Urus (Bos primigenius), the Bos antiquus, and a small aboriginal species, the Bos longifrons, believed by Owen to be " the source of the domesticated cattle of the Celtic races before the Roman invasion." Order VII. Hyracoidea. — This little order, represented at the present day by no more than the single genus Hyrax, is not known to have any fossil representatives. Order VIII. Proboscidea. — This order, including no other living forms than the Elephants, came into existence in the Miocene period, where it is represented by all its three sec- tions, Deinotherium, Mastodon, and Elephas. The Deinotherium (fig. 202) was a gigantic Miocene Mam- mal, probably something like the living Elephants, but having no incisors in the upper jaw. In place of these, the lower jaw was furnished with two long tusk -like incisors, which were bent downwards. In most essential respects the Mastodons (fig. 219) resemble the Elephants, but the molar teeth were furnished with nipple- shaped eminences. Usually there are two tusk-shaped upper incisors, but sometimes lower incisors are present as well. Four Mastodons occur in the Miocene of Europe, and three in that of India. No Elephant has yet been discovered in the Miocene Rocks DISTRIBUTION OF MAMMALS IN TIME. 567 of Europe, but six species are known from Miocene strata in India. In the Pliocene period, Europe possessed its Elephants (viz., E. friscus and E. meridiotialis] ; but the best known of Fig. 219. — Skeleton of Mastodon. the extinct Elephants, as well as the most modern, is the Mammoth (E. primigenius, fig. 220). The Mammoth enjoyed Fig. 220.— Skeleton of the Mammoth (Elephas primigenius). a very extended geographical distribution, remains of it occur- ring in Britain, continental Europe, Siberia, and throughout a large portion of North America. There can also be no ques- tion but that the Mammoth existed in the earlier portion of the human period. Order IX. Carnivora. — If the little Microlestes of the Upper Trias be Marsupial, as is most probably the case, then the order Carnivora is comparatively modern, the earliest un- doubted remains having been found in the Eocene Rocks. The tribe of the Felida is represented in the Miocene period by the large Machairodus, with sabre-shaped upper canines. 568 MANUAL OF ZOOLOGY. Species of this genus must have been as large as a Lion. In the later Pliocene and Post-pliocene deposits occur the remains of a large Lion — the Cave-lion or Fdis spelcea — along with which, in Britain and continental Europe, are the bones of a large Hyaena (H. spelaa) and a gigantic Bear ( Ursus spelaus). Remains of Wolves, Foxes, Badgers, Otters, Pole-cats, Weasels, and other Carnivora are also found in various later Tertiary deposits, and in bone-caves. Order X. Rodentia. — No Rodent animal is as yet known to have occurred earlier than the Eocene period. Here are found forms allied to the living Dormouse and Squirrel. In the Miocene Rocks occur numerous small Rodents. In the Plio- cene and Post-pliocene deposits the order is also well repre- sented, the most remarkable form being the great Beaver (Trogontherium), which appears to have survived into the his- torical period. Order XL Cheiroptera. — The earliest-known indications of Bats are in the Eocene period, but the order is of no geological importance. Order XII. Insectivora. — The Insectivorous Mammals, r like- wise, commenced their existence, so far as is known, in the Eocene period ; and they, also, are of no importance from a geological point of view. Order XIII. Quadrumana. — The earliest-known remains of Quadrumana occur in the Miocene period. Several genera are known, but the most important are Pliopithecus and Dryo- pithecus, both of which are European, and both of which belong to the section of the Catarhine Monkeys which are at present characteristic of the Old World. They appear to be most nearly allied to the recent Gibbons. It is interesting to notice that the American fossil Monkeys — from the later Tertiary deposits of South America — belong to the division of the Quad- rumana now peculiar to that continent — to the section, namely, of the Platyrhine Monkeys. GEOGRAPHICAL SUCCESSION OF ORGANIC FORMS. A few words may be said here on a law which may be called the " law of the geographical succession of organic forms," and which is illustrated more completely by the Mammalia than by any other extinct animals. An examination, namely, of the facts of the geological distribution of Mammals leads to the striking generalisation that " the present distribution of organic forms dates back to a period anterior to the origin of existing species" (Lyell). In other words, though the extinct Mam- DISTRIBUTION OF MAMMALS IN TIME. 569 mals of the later geological deposits of any given country differ specifically from those now existing in the same country, they are nevertheless referable to the same orders, and are in every respect more closely allied to the present Mammalian fauna than to that of any other country. A few examples will render this perfectly clear. Australia at the present day is an altogether peculiar zoolo- gical province, characterised by the abundance and variety of Marsupials which inhabit it. In the Post-tertiary deposits of Australia, however, we are presented with proofs that Marsu- pials were just as characteristic of Australia during late geolo- gical epochs as they are now. In the Post-pliocene period we know that Australia was occupied by Kangaroos, Kangaroo- rats, Wombats, Phalangers, and Carnivorous Marsupials, in every way representing the living Marsupials in zoological value, but specifically distinct, and generally of gigantic size. In the same way, South America at the present day is espe- cially characterised by a Mammalian fauna, containing many peculiar forms, the Edentata being especially conspicuous, and having a larger representation than in any other region. Simi- lar but distinct forms, however, are found to have existed in South America anterior to the creation of any existing species. Thus, the modern Sloths of South America are represented by the colossal Mylodon, Megalonyx, and Megatherium. The little armour-plated Armadillos are represented by the equally colos- sal Glyptodon. The Llamas — representing in South America the Camels of the Old World — are represented by the curious extinct genus Macrauchenia. The Platyrhine Monkeys have their extinct representatives. Fossil Tapirs take the place of the two existing species ; and the Peccaries are represented by at least five extinct species of Dicotyles. Similarly, India is at present the only country in which four- horned Antelopes occur ; and it is in the Sivalik Hills that there have been found the two gigantic four-horned Antelopes, which constitute the genera Sivatherium and Bramatherium. In Europe, again, the Mammalian fauna of the later Tertiary periods is much more closely allied to that now characterising the Old World, than to that of the New. We have the Lion, Bear, Wolf, Fox, and other well-known Carnivora. Elephants, Rhinoceroses, and Hippopotami, then as now, are characteristic Old World forms. The Ruminants are equally characteristic of the eastern hemisphere, though not exclusively confined to it, and they have numerous and varied representatives in later Tertiary deposits. The Giraffe is represented by the Hellado- therium, and the Bactrian Camel by the Merycotherium of the 57O MANUAL OF ZOOLOGY. Siberian Drift. The fossil Quadrumana^ too, of Europe, all belong to the Catarhine section of the order. It is unnecessary to pursue the subject further, but no law is more firmly established than this : " That with extinct as with existing Mammalia, particular forms were assigned to particular provinces; and that the same forms were restricted to the same provinces at a former geological period as they are at the present day " (Owen). It is to be borne in mind, however, that the law, as just stated, holds good for the later Tertiary period only, and does not apply, in any manner that admits of being traced, to the earlier geological epochs. TABULAR VIEW OF THE CHIEF SUB-DIVISIONS OF THE SUB-KINGDOM VERTEBRATA. SUB-KINGDOM VI.— VERTEBRATA. CLASS I. PISCES. Order i. Pharyngobranchii. 2. Marsipobranchii. 3. Teleostei. 4. Ganoidei. 5. Elasmobranchii. 6. Dipnoi. CLASS II. AMPHIBIA. Order i. Labyrinthodontia. 2. Ophiomorpha. 3. Urodela. 4. Anoura. CLASS III. REPTILIA. Order i. Chelonia. 2. Ophidia. 3. Lacertilia. 4. Crocodilia. 5. Ichthyopterygia. 6. Sauropterygia. 7. Anomodontia. 8. Pterosauria. 9. Deinosauria. CLASS IV. AVES. Order i. Natatores. 2. Grallatores. 3. Cursores. 4. Rasores. TABLE OF VERTEBRATA. 5/1 Sub-order a. Gallinacei. b. Columbacei. 5. Scansores. 6. Insessores. Sub-order a. Conirostres. b. Dentirostres. c. Tenuirostres. d. Fissirostres. 7. Raptores. 8. Saururae. CLASS V. MAMMALIA. Division A. Ornithodelphia. Order i. Monotremata. Division B. Didelphia. Order 2. Marsupialia. Division C. Monodelphia. Order 3. Edentata. 4. Sirenia. 5. Cetacea. 6. Ungulata. Section Perissoaactyla. a. Multungula. b. Solidungula. Section Artiodactyla. a. Omnivora. b. Ruminantia. 7. Hyracoidea. 8. Proboscidea. 9. Carnivora. a. Pinnigrada. b. Plantigrada. c. Digitigrada. 10. Rodentia. 11. Cheiroptera. 12. Insectivora. 13. Quadrumana.^ a. Strepsirhina. b. Platyrhina. c. Catarhina. 14. Bimana. GLOSSARY. ABDOMEN (Lat. abdo, I conceal). The posterior cavity of the body, contain- ing the intestines and others of the viscera. In many Invertebrates there is no separation of the body-cavity into thorax and abdomen, and it is only in the higher Annulosa that a distinct abdomen can be said to exist. ABERRANT (Lat. aberro, I wander away). Departing from the regular type. ABNORMAL (Lat. ab, from ; norma, a rule). Irregular ; deviating from the ordinary standard. ABOMASUM. The fourth cavity of the complex stomach of the Kuminants. ABRANCHIATE (Gr. a, without ; bragchia, gills). Destitute of gills or bran- chiae. AcALEPH-E (Gr. akalepJie, a nettle). Applied formerly to the Jelly-fishes or Sea-nettles, and other Kadiate animals, in consequence of their power of stinging, derived from the presence of microscopic cells, called " thread- cells," in the integument. ACANTHOCEPHALA (Gr. acantha, a thorn ; kephale, head). A class of parasitic worms in which the head is armed with spines. ACANTHOMETRINA (Gr. akantha ; and metra, the womb). A family of Protozoa, characterised by having radiating silicious spines. ACANTHOPTERYGIA (Gr. akantha, spine; pterux, wing). A group of bony fishes with spinous rays in the front part of the dorsal fin. ACARINA (Gr. akari, a mite). A division of the Arachnida, of which the Cheese-mite is the type. ACEPHALOUS (Gr. a, without ; kephah, head). Not possessing a distinct head. ACETABULA (Lat. acetabulum, a cup). The suckers with which the cephalic processes of many Cephalopoda (Cuttle-fishes) are provided. ACETABULUM. The cup-shaped socket of the hip-joint in Vertebrates. ACRITA (Gr. akritos, confused). A term sometimes employed as synony- mous with Protozoa, or the lowest division of the animal kingdom. ACTINOMERES (Gr. aktin, a ray ; meros, a part). The lobes which are mapped out on the surface of the body of the Ctenophora, by the ctenophores, or cornb-like rows of cilia. ACTINOSOMA (Gr. aktin ; and soma, body). Employed to designate the entire body of any Actinozoon, whether this be simple (as in the Sea- anemones), or composed of several zooids (as in most Corals). ACTINOZOA (Gr. aktin ; and zoon, an animal). That division of the Ccelen- terata of which the Sea-anemones may be taken as the type. ADELARTHROSOMATA (Gr. addos, hidden ; arthros, joint ; soma, body). An order of the Arachnida. AGAMIC (Gr. a, without ; gamos, marriage). Applied to all forms of repro- duction in which the sexes are not directly concerned. ALLAN TOIDEA. The group of Vertebrata in which the foetus is furnished with an allantois, comprising the Reptiles, Birds, and Mammals. ALLANTOIS (Gr. alias, a sausage). One of the "membranes" of the foetus in certain Vertebrates. GLOSSARY. 573 ALVEOLI (Lat. dim. of alvus, belly). Applied to the sockets of the teeth. AMBULACRA (Lat. ambulacrum, a place for walking). The perforated spaces or " avenues" through which are protruded the tube-feet, by means of which locomotion is effected in the Mchinodermaia. AMBULATORY (Lat. ambulo, 1 walk). Formed for walking. Applied to a single limb, or to an entire animal. AMETABOLIC (Gr. a, without ; metabole, change). Applied to those insects which do not possess wings when perfect, and which do not, therefore, pass through any marked metamorphosis. AMNION (Gr. amnos, a lamb). One of the foetal membranes of the higher Vertebrates. AMNIOTA. The group of Vertebrata in which the foetus is furnished with an amnion, comprising the Reptiles, Birds, and Mammals. AMCEBA (Gr. amoibos, changing). A species of Rhizopod, so called from the numerous changes of form which it undergoes. AMCEBIFORM. Resembling an Amoeba in form. AMORPHOZOA (Gr. a, without ; morphe, shape ; zoon, animal). A name some- times used to designate the Sponges. AMPHIBIA (Gr. amphi, both ; bios, life). The Frogs, Newts, and the like, which have gills when young, but can always breathe air directly when adult. AMPHICCELOUS (Gr. ampki, at both ends ; Jcoilos, hollow). Applied to verte- brae which are concave at both ends. AMPHIDISCS (Gr. amphi, at both ends ; diskos, & quoit, or round plate). The spicula which surround the gemmules of Spongilla, and resemble two toothed wheels united by an axle. AMPHIOXUS (Gr. amphi, at both ends ; oxus, sharp). The Lancelet, a little fish, which alone constitutes the order Pharyngobronchii. AMPHIPNKUSTA (Gr. amphi, both ; pneo, I breathe). Applied to the "peren- nibranchiate" Amphibians which retain their gills through life. AMPHIPODA (Gr. amphi, and pous, a foot). An order of Crustacea. ANAL (Lat. anus, the vent). Connected with the anus, or situated near the anus. ANALLANTOIDEA. The group of Vertebrata in which the embryo is not fur- nished with an allantois. ANALOGOUS. Applied to parts which perform the same function. AN AMNIOTA. The group of Vertebrata in which the embryo is destitute of an amnion. ANARTHROPODA (Gr. a, without ; arthros, a joint ; pous, foot). That division of Annulose animals in which there are no articulated appendages. ANCHYLOSIS or ANKYLOSIS (Gr. ankulos, crooked). The union of two bones by osseous matter, so that they become one bone, or are immovably joined together. ANDROGYNOUS (Gr. aner, a man ; gune, a woman). Synonymous with her- maphrodite, and implying that the two sexes are united in the same in- dividual. ANDROPHORES (Gr. aner, a man ; and phero, I carry). Applied to medusiform gonophores of the Hydrozoa, which carry the spermatozoa, and differ in form from those in which the ova are developed. ANNELIDA (a Gallicised form of Annulata). The Ringed worms, which form one of the divisions of the Anarthropoda. ANNULATED. Composed of a succession of rings. ANNULOIDA (Lat. annul us, a ring ; Gr. eidos, form). The sub-kingdom com- prising the Echinodermata and the Scolecida (=Echinozoa). ANNULOSA (Lat. annulus). The sub-kingdom comprising the Anarthropoda and the Arthropoda or Articulata, in all of which the body is more or less evidently composed of a succession of rings. ANOMODONTIA (Gr. anomos, irregular; odous, tooth). An extinct order of Reptiles, often called Dicynodontia. ANOMURA (Gr. anomos, irregular ; oura, tail). A tribe of Decapod Crustacea, of which the Hermit-crab is the type. 5/4 GLOSSARY. ANOPLURA (Gr. anoplos, unarmed ; our a, tail). An order of Apterous Insects. ANOURA (Gr. a, without ; oura, tail). The order of Amphibia comprising the Frogs and Toads, in which the adult is destitute of a tail. Often called BatracJiia, ANTENNA (Lat. antenna, a yard-arm). The jointed horns or feelers possessed by the majority of the Articulata. ANTENNULES (dim. of Antennas). Applied to the smaller pair of antennae in the Crustacea. ANTIBRACHIUM (Gr. anti, in front of ; brachion, the arm). The fore-arm of the higher Vertebrates, composed of the radius and ulna. ANTLERS. Properly the branches of the horns of the Deer tribe (Cervidce), but generally applied to tbe entire horns. ANTLIA (Lat. antlia, a pump). The spiral trunk or proboscis with which. Butterflies and other Lepidopterous Insects suck up the juices of flowers. APHANIPTERA (Gr. aphanos, inconspicuous; pteron, a wing). An order of Insects, comprising the Fleas. APLACENTALIA. The section of the Mammalia, comprising the two divisions of the Didelphia and Monodelphia, in which the young is not furnished with a placenta. APODA (Gr. a, without ; poda, feet). Applied to those fishes which have no ventral fins. Also to the footless Coedlice amongst the Amphibia. APODAL. Devoid of feet. APODEMATA (Gr. apodaio, I portion off). Applied to certain chitinous septa which divide the tissues in Crustacea. APTERA (Gr. a, without ; pteron, a wing). A division of Insects, which is characterised by the absence of wings in the adult condition. APTEROUS. Devoid of wings. APTERYX (Gr. a, without ; pterux, a wing). A wingless bird of New Zealand, belonging to the order Cursores. ARACHNIDA (Gr. arachne, a spider). A class of the Articulata, comprising Spiders, Scorpions, and allied animals. ARBORESCENT. Branched like a tree. ARCH.EOPTERYX (Gr. archaios, ancient; pterux, wing). The singular fossil bird which alone constitutes the order of the Satirurce. ARCHENCEPHALA (Gr. archo, I overrule ; egkephalos, brain). The name ap- plied by Owen to his fourth and highest group of Mammalia,, comprising Man alone. ARENACEOUS. Sandy, or composed of grains of sand. ARTICULATA (Lat. articulus, a joint). A division of the animal kingdom, comprising Insects, Centipedes, Spiders, and Crustaceans, characterised by the possession of jointed bodies or jointed limbs. The term Arthropoda is now more usually employed. ARTIODACTYLA (Gr. artios, even ; daJctulos, a finger or toe). A division of the hoofed quadrupeds ( Ungulata) in which each foot has an even number of toes (two or four). ASCIDIOIDA (Gr. 'askos, a bottle ; eidos, form). A synonym of Tunicata, a class of Molluscous animals, which have the shape, in many cases, of a two-necked bottle. ASEXUAL. Applied to modes of reproduction in which the sexes are not concerned. ASIPHONATE. Not possessing a respiratory tube or siphon. (Applied to a division of the Lamellibranchiate Molluscs.) ASTEROID (Gr. aster, a star ; and eidos, form). Star-shaped, or possessing radiating lobes or rays like a star-fish. ASTEROIDEA. An order of Echinodermata, comprising the Star-fishes, charac- terised by their rayed form. ASTOMATOUS (Gr. a, without ; stoma, mouth). Not possessing a mouth. ATLAS (Gr. the God who holds up the earth). The first vertebra of the neck, which articulates with and supports the skull. ATRIUM (Lat. a hall). Applied to the great chamber or " cloaca,*' into which the intestine opens in the Tunicata, GLOSSARY. 575 AUEELIA (Lat. aurum, gold). Applied to the chrysalides of some Lepidoptera, on account of their exhibiting a golden lustre. ATJRICLE (Lat. dim. of auris, ear). Applied to one of the cavities of the heart, by which blood is driven into the ventricle. AUTOPHAGI (Gr. autos, self; phago, I eat). Applied to birds whose young can run aboiit and obtain food for themselves as soon as they escape from the egg. AVES (Lat. avis, a bird). The class of the Birds. AVICULARIUM (Lat. avicula, dim. of avis, a bird). A singular appendage, often shaped like the head of a bird, found in many of the Polyzoa. Axis (Gr. axon, a pivot). The second vertebra of the neck, upon which the skull and atlas usually rotate. AZYGOS (Gr. a, without ; zugos, yoke). Single ; without a fellow. BACTERIUM (Gr. baJcterion, a staff). A kind of staff-shaped filament which appears in organic infusions after they have been exposed to the air. BALANID.E (Gr. balanos, an acorn). A family of sessile Cirripides, com- monly called "Acorn-shells." BALEEN (Lat. balcena, a whale). The horny plates which occupy the palate of the true or " whale-bone" Whales. BATIDES (Gr. batos, a bramble). The family of the Elasmobranchii compris- ing the Rays. BATRACHIA (Gr. batrachos, a frog). Often loosely applied to any of the Am- phibia, but sometimes restricted to the Amphibians as a class, or to the single order of the Anoura. BIFID. Cleft into two parts ; forked. BILATERAL. Having two symmetrical sides. BIMANA (Lat. bis, twice ; manus, a Land). The order of Mammalia compris- ing Man alone. BIPEDAL (Lat. bis, twice ; pes, foot). Walking upon two legs. BIRAMOUS (Lat. bis, twice ; ramus, a branch). Applied to a limb which is divided into two branches (e.g., the limbs of Cirripedes). BIVALVE (Lat bis, twice ; valvce, folding-doors). Composed of two plates or valves ; applied to the shell of the Lamellibranchiata and Brachiopoda, and to the carapace of certain Crustacea. BLASTOIDEA (Gr. blastos, a bud ; and eidos, form). An extinct order of Echi- nodermata, often called Pentremites. BRACHIOPODA (Gr. brachion, an arm ; pous, the foot). A class of the Mol- luscoida, often called " Lamp-shells," characterised by possessing two fleshy arms continued from the sides of the mouth. BRACHIUM (Gr. brachion, arm). Applied to the upper arm of Vertebrates. BRACHYURA (Gr. brachus, short ; oura, tail). A tribe of the Decapod Crusta- ceans with short tails (i.e., the Crabs). BRACTS. (See Hydrophyllia.) BRADYPODID.E (Gr. bradus, slow; poda, feet). The family of Edentata com- prising the Sloths. BRANCHIA (Gr. bragchia, the gill of a fish). A respiratory organ adapted to breathe air dissolved in water. BRANCHIATE. Possessing gills or branchiae. BRANCHIFERA (Gr. bragchia, gill ; and phero, I carry). A division of Oastero- podous Molluscs, in which the respiration is aquatic, and the respiratory organs are mostly in the form of distinct gills. BRANCHIO-GASTEROPODA (= Branchifera). BRANCHIOPODA (Gr. bragchia; and pous, foot). A legion of Crustacea, in which the gills are supported by the feet. BRANCHIOSTEGAL (Gr. bragchia, gill ; stego, I cover). Applied to a membrane and rays by which the gills are protected in many fishes. BREVILINGUIA (Lat. brevis, short j lingua, tongue). A division of the Lacer- tilia. BREVIPENNAT2E (Lat. brevis, short ; penna, a wing). A group of the Natato- rial Birds. 576 GLOSSARY. BRONCHI (Gr. brogckos, the windpipe). The branches of the windpipe (trachea), by which the air is conveyed to the vesicles of the lung. BRUTA (Lat. brutus, heavy, stupid). Often used to designate the Mamma- lian order of the Edentata. BRYOZOA (Gr. bruon, moss ; zoon, animal). A synonym of Polyzoa, a class of the Molluscoida. BUCCAL (Lat. bucca, mouth or cheeks). Connected with the mouth. BCRSIFORM (Lat. bursa, a purse ; forma, shape). Shaped like a purse ; sub- spherical. BYSSIFKROUS. Producing a byssus. BYSSUS (Gr. bussos, flax). A term applied to the silky filaments by which the Pinna, the common Mussel, and certain other bivalve Mollusca, attach themselves to foreign objects. CADUCIBRANCHIATE (Lat. caducus, falling off; Gr. Iragchia, gill). Applied to those Amphibians in which the gills fall off before maturity is reached. CADUCOUS. Applied to parts which fall off or are shed during the life of the animal. CJECAL (Lat. ccec^ls, blind). Terminating blindly, or in a closed extremity. CAECUM (Lat. ccecus). A tube which terminates blindly. C^ESPITOSE (Lat. ccespes, a turf). Tufted. CAINOZOIC. (See Kainozoic. ) CALCAR (Lat. a spur). Applied to the " spurs " of Rasorial birds ; and also to the rudiments of the hind-limbs in certain Snakes. CALCAREOUS (Lat. calx, lime). Composed of carbonate of lime. CALICE. The little cup in which the polype of a coralligenous Zoophyte (A ctinozoon) is contained. CALYCOPHORHLE (Gr. kalux, a cup ; and pltero, I carry). An order of the Oceanic Hydrozoa, so called from their possessing bell-shaped swimming organs (nectocalyces). CALYX (Lat. calyx, a cup). Applied to the cup-shaped body of Vorticella (Protozoa), or of a Crinoid (Echinodermata). CAMPANULARIDA (Lat. campanula, a bell). An order of Hydroid Zoophytes. CANINE (Lat. can-is, a dog). The eye-tooth of Mammals, or the tooth which is placed at or close to the prsemaxillary suture in the upper jaw, and the corresponding tooth in the lower jaw. CAPITULUM (Lat. dim. of caput, head). Applied to the body of a Barnacle (Lepadidce), from its being supported upon a stalk or peduncle. CARAPACE. A protective shield. Applied to the upper shell of Crabs, Lob- sters, and many other Crustacea; also to the case with which certain of the Infusoria are provided. Also the upper half of the immovable case in which the body of a Chelonian is protected. CARINAT^E (Lat. carina, a keel). Applied by Huxley to all those birds in which the sternum is furnished with a median ridge or keel. CARNIVORA (Lat. caro, flesh ; voro, I devour). An order of the Mammalia. CARNIVOROUS (Lat. caro, flesh ; voro, I devour). Feeding upon flesh. CARNOSE (Lat. caro). Fleshy. CARPOPHAGA (Gr. karpos, fruit ; phago, I eat). A section of the Marsupialia. CARPUS (Gr. karpos, the wrist). The small bones which intervene between the fore-arm and the metacarpus. CATARHINA (Gr. Jcata, downwards ; rhines, nostrils). A group of the Quadru- mana. CAUDAL (Lat. cauda, the tail). Belonging to the tail. CAVICORNIA (Lat. cavus, hollow; cornu, a horn). The "hollow-horned" Ruminants, in which the horn consists of a central bony " horn-core " sur- rounded by a horny sheath. CENTRUM (Gr. kentron, the point round which a circle is described by a pair of compasses). The central portion or " body " of a vertebra. CEPHALIC (Gr. kephale, head). Belonging to the head. CEPHALO-BRANCHIATE (Gr. kephale; and oragchia, gill). Carrying gills upon GLOSSARY. 577 the head. Applied to a section of the Annelida, which, like the Serpulce, have tufts of external gills placed upon the head. CEPHALOPHORA (Gr. kephale; aodttfero, I carry). Used synonymously with Encephala, to designate those Moliusca which possess a distinct head. CEPHALOPODA (Gr. kei>hale; and poda, feet). A class of the Moliusca, com- prising the Cuttle-fishes and their allies, in which there is a series of arms ranged round the head. CEPHALOTHORAX (Gr. kephale; and thorax, chest). The anterior division of the body in many Crustacea and Arachnida, which is composed of the coalesced head and chest. CERE. The naked space found at the base of the bill of some birds. CERVICAL (Lat. cervix, neck). Connected with the region of the neck. CESTOID EA (Gr. kestos, a girdle). An old name for the Tvcniada, a class of Intestinal Worms with flat bodies like tape (hence the name Tapeworms). CESTRAPHORI (Gr. kestra, a weapon ; phero, I carry). The group of Elasmo- branchii represented at the present day by the Port Jackson Shark. CETACEA (Gr. ketos, a whale). The order of Mammals comprising the Whales and Dolphins. CH.ETOGNATHA (Gr. chaite, bristle ; gnathos, jaw). An order of the Anarlhro- poda, comprising only the oceanic genus Sagitta. CHEIROPTERA (Gr. cheir, hand ; pteron, a wing). The order of Mammals com- prising the Bats. CHELAE (Gr. chele, a claw). The prehensile claws with which some of the limbs are terminated in certain Crustacea, such as the Crab, Lobster, &c. CH ELATE. Possessing chelae ; applied to a limb. CHELICER^: (Gr. cltele, a claw ; and keras, a horn). The prehensile claws of the Scorpion, supposed to be homologous with antenna?. CHELONIA (Gr. c/telone, a tortoise). The order of Reptiles comprising the Tortoises and Turtles. CHELONOBATRACHIA (Gr. chelonc, a tortoise ; batrachos, a frog). Sometimes applied to the Amphibian order of the Anoura (Frogs and Toads). CHILOGNATHA (Gr. cheilos, a lip; and gnathos, a jaw). An order of the Myriapoda. CHILOPODA (Gr. cheilos ; and poda, feet). An order of the Myriapoda. CHITINE (Gr. chiton, a coat). The peculiar chemical principle, nearly allied to horn, which forms the exoskeleton in mauy Invertebrate Animals, espe- cially in the Arthropoda (Crustacea, Insecta, &c. ) CHLOROPHYLL (Gr. chloros, green ; arid phyllos, a leaf). The green colouring matter of plants. CHROMATOPHORES (Gr. chroma, complexion, or colour ; and phero, I carry). Little sacs which contain pigment-granules, and are found in the integu- ment of Cuttle-fishes. CHRYSALIS (Gr. chrusos, gold). The motionless pupa of butterflies and moths, so called because sometimes exhibiting a golden lustre. CHYLAQUEOUS FLUID. A fluid consisting partly of water derived from the exterior, and partly of the products of digestion (chyle), occupying the body-cavity or perivisceral space in many Invertebrates (Annelidas, Echino- derms, &c. ), and sometimes having a special canal-system for its conduction (chylaqueous canals). CHYLE (Gr. chulos, juice). The milky fluid which is the result of the action of the various digestive fluids upon the food. CHYLIFIC (Gr. chulos, juice [chyle] ; and Lat. facio, I make). Producing chyle. Applied to one of the stomachs, when more than one is present. The word is of mongrel origin ; and " chylopoietic" is more correct. CHYME (Gr. chumos, juice). The acid pasty fluid produced by the action of the gastric juice upon the food. CHYME-MASS. The central, semi-fluid sarcode in the interior of an Infusorian. CILIA (Lat. cilium, an eyelash). Microscopic, hair-like filaments, which have the power of lashing backwards and forwards, thus creating currents in the surrounding or contiguous fluid, or subserving locomotion in the animal which possesses them. VOL. II. 2 O 578 GLOSSARY. CILIOGRADA (Lat. cilium; and gradior, I walk). Synonymous with Cteno- phora, an order of Actinozoa. CINCLIDES (Gr. kigklis, a lattice). Special apertures in the column-walls of some Sea-anemones (Actiniae), which probably serve for the emission of the cord-like "craspeda." CIRRI (Lat. cirrus, a curl). Tendril-like appendages, such as the feet of Bar- nacles and Acorn-shells (Cirripedes), the lateral processes on the arms of Brachiopoda, &c. CIRRIFEROUS or CIRRIGEROUS. Carrying cirri. CIRRIPEDIA, CIRRHIPEDIA, or CiRRHOPODA (Lat. cirrus, a curl ; and pes, a foot). A sub-class of Crustacea with curled jointed feet. CIRROSTOMI (Lat. cirrus, a tendril ; Gr. stoma, mouth). Sometimes used to designate the Pharyngobranchii. CLADOCERA (Gr. Jclados, a branch; Jceras, a horn). An order of Crustacea with branched antennae. CLAVATE (Lat. clavus, a club). Club-shaped. CLAVICLE (Lat. clavicula, a little key). The " collar-bone," forming one of the elements of the pectoral arch of Vertebrates. CLOACA (Lat. a sink). The cavity into which the intestinal canal and the ducts of the generative and urinary organs open in common, in some In- vertebrates (e.g., in Insects), and also in many Vertebrate animals. CLYPEIFORM (Lat. clypeus, a shield ; and forma, shape). Shield-shaped ; ap- plied, for example, to the carapace of the King-crab. CNID^E (Gr. knide, a nettle). The urticating cells, or " thread-cells/' where- by many Ccelenterate animals obtain their power of stinging. COCCOLITHS (Gr. kokkos, a berry ; lithos, stone). Minute oval or rounded bodies, which are found either free or attached to the surface of cocco- spheres. COCCOSPHERES (Gr. koJckos ; and sphaira, a sphere). Spherical masses of saroode, enclosed in a delicate calcareous envelope, and bearing coccoliths upon their external surface. Both coccospheres and coccoliths are im- bedded in a diffused plasmodium of sarcode, the whole constituting a low Rhizopodic organism. COCCYGEAL. Connected with the coccyx. COCCYX (Gr. kokkux, a cuckoo). The terminal portion of the spinal column in man, so called from its resemblance to a cuckoo's beak. COCOON (French cocon, the cocoon of the silkworm ; connected with Fr. cogue, shell, which is derived from the Lat. concha). The outer covering of silky hairs with which the pupa or chrysalis of many insects is protected. CODONOSTOMA (Gr. Jcodon, a bell ; stoma, mouth). The aperture or mouth of the disc (nectocalyx) of a Medusa, or of the bell (gonocalyx) of a medusi- form gonophore. C(ELENTERATA (Gr. koilos, hollow ; enteron, the bowel). The sub-kingdom which comprises the Hydrozoa and Actinozoa. Proposed by Frey and Leuckhart in place of the old term Radiata, which included other animals as well. CCENENCHYMA (Gr. Icoinos, common ; enchuma, tissue). The common cal- careous tissue which unites together the various corallites of a compound corallum. CCENCECIUM (Gr. Jcoinos, common ; oikos, house). The entire dermal system of any Polyzoon : employed in place of the terms polyzoary or polypidom. CCENOSARC (Gr. koinos, common ; sarx, flesh). The common organised medium by which the separate polypites of a compound Hydrozoon are connected together. COLEOPTERA (Gr. koleos, a sheath ; pteron, wing). The order of Insects (Beetles) in which the anterior pair of wings are hardened, and serve as protective cases for the posterior pair of membranous wings. COLDBRINA (Lat. coluber, a snake), A division of the Ophidia. COLUMBACEI (Lat. columba, a dove). The division of Rasorial birds compris- ing the Doves and Pigeons. COLUMELLA (Lat. dim. of columna, a column). In Conchology, the central GLOSSARY. 579 axis round which the whorls of a spiral univalve are wound. Amongst the Actinozoa, it is the central axis or pillar which is found in the centre of the thec89 of many corals. COLUMN. Applied to the cylindrical body of a Sea-anemone (Actinia) ; also to the jointed stern or peduncle of the stalked Crinoids. COMMISSURAL (Lat. comniitto, I solder together). Connecting together ; usually applied to the nerve-fibres which unite different ganglia. CONCHA (Lat. a shell). The external ear by which sounds are collected and transmitted to the internal ear. CONCHIFERA (Lat. concha, a shell ; fe.ro, I carry). Shell-fish. Applied in a restricted sense to the bivalve Molluscs, and used as a synonym for Lanielli- branckiata. CONDYLE (Gr. kondulos, a knuckle). The surface by which one bone articu- lates with another. Applied especially to the articular surface or surfaces by which the skull articulates with the vertebral column. CONIROSTRES (Lat. comes, a cone ; rostrum, a beak). The division of Perching birds with conical beaks. COPEPODA (Gr. kope, an oar ; poda, feet). An order of Crustacea. CORACOID (Gr. korax, a crow ; eidos, form). One of the bones which enters into the composition of the pectoral arch in Birds, Reptiles, and Mono- tremes. In most Mammals it is a mere process of the scapula, having, in man, some resemblance in shape to the beak of a crow. CORALLIGENOUS. Producing a corallum. CORALLITE. The corallum secreted by an Actinozob'n which consists of a single polype ; or the portion of a composite corallum which belongs to, and is secreted by, an individual polype. CORALLUM (from the Latin for Red Coral). The hard structures deposited in, or by, the tissues of an Actinozoo'n — commonly called a " coral." CORIACEOUS ( Lat. corium, hide). Leathery. CORPUS CALLOSUM (Lat. the "firm body"). The great band of nervous matter which unites the two hemispheres of the brain in the Mammals. CORPUSCULATED (Lat. corpusculum, a little body or particle). Applied to fluids which, like the blood, contain floating solid particles or "corpuscles." CORTICAL LAYER. The layer of consistent sarcode, which in the Infusoria encloses the chyme-mass, and is surrounded by the cuticle. Sometimes called the " parenchyma of the body." COST^E (Lat. costa, a rib). Applied amongst the Crinoidea to designate the rows of plates which succeed the inferior or basal portion of the cup (pelvis). Amongst the Corals the "costae" are vertical ridges which occur on the outer surface of the theca, and mark the position of the septa within. COSTAL (Lat. costa, a rib). Connected with the ribs. CRANIUM (Gr. kranion, the skull). The bony or cartilaginous case in which the brain is contained. CRASPEDA (Gr. kraspedon, a margin or fringe). The long, convoluted cords, containing thread-cells, which are attached to the free margins of the mesenteries of a Sea-anemone. CREPUSCULAR (Lat. crepusculum, dusk). Applied to animals which are active in the dusk or twilight. CRINOIDEA (Gr. kriuos, a lily ; eidos, form). An order of Echinodermata, comprising forms which are usually stalked, and sometimes resemble lilies in shape. CROCODILIA (Gr. krokodeilos, a crocodile). An order of Reptiles. CROP. A partial dilatation of the gullet, technically called " ingluvies." CRUSTACEA (Lat. crusta, a crust). A class of articulate animals, comprising Crabs, Lobsters, &c., characterised by the possession of a hard shell or crust, which they cast periodically. CTENOCYST (Gr. kteis, a comb ; knslis, a bag or cyst). The sense-organ (pro- bably auditory) which occurs in the Ctenophora. CTENOID (Gr. kteis, a comb ; eidos, form). Applied to those scales of fishes, the hinder margins of which are fringed with spines or comb-like projections. 580 GLOSSARY. CTENOPHORA (Gr. Ictds, a comb ; andphero, I carry). An order of Actinozoa, comprising oceanic creatures, which swim by means of " ctenophores," or bands of cilia arranged in comb-like plates. CuRSORES (Lat. curro, I run). An order of Aves, comprising birds destitute of the power of flight, but formed for running vigorously (e.g., the Ostrich and Emeu). CUSPIDATE. Furnished with small pointed eminences or " cusps." CUTICLE (Lat. cuticula, dim. of cutis, skin). The pellicle which forms the outer layer of the body amongst the Infusoria. The outer layer of the integument generally. CUTIS (Lat. skin). The inferior vascular layer of the integument, often called the cutis vera, the corium, or the derma. CYCLOID (Gr. kukloi, a circle ; eidos, form). Applied to those scales of fishes which have a regularly circular or elliptical outline with an even margin. CYCLOSTOMI. Sometimes used to designate the Hag-fishes and Lampreys, forming the order Marsipobranchii. CYST (Gr. kustis, a bladder or bag). A sac or vesicle. CYSTICA. The embryonic forms (scolices) of certain intestinal worms (tape- worms), which were described as a distinct order, until their true nature was discovered. CYSTOTDEA (Gr. kusiis, a bladder ; and eidos, form). An extinct order of Echinodermala. DECAPODA (Gr. deka, ten ; poda, feet). The division of Crustacea which have ten ambulatory feet ; also the family of Cuttle-fishes, in which there are ten arms or cephalic processes. DECIDUOUS (Lat. decido, I fall off). Applied to parts which fall off or are shed during the life of the animal. DECOLLATED (Lat. decollo, I behead). Applied to univalve shells, the apex of which falls off in the course of growth. DEINOSAURIA (Gr. deinos, terrible; saura, lizard). An extinct order of Reptiles. DENDRIFORM, DENDRITIC, DENDROID (Gr. dendron, a tree). Branched like a tree, arborescent. DENTIROSTRES (Lat. dens, a tooth ; rostrum, a beak). The group of Perching Birds in which the upper mandible of the beak has its lower margin toothed. DERMA (See " Cutis "). DERMAL (Gr. derma, skin). Belonging to the integument. DERMOSCLERITES (Gr. derma, skin ; skleros, hard). Masses of spicules which occur in the tissues of some of the A Icyonidce (Actinozoa). DESMIDLE. Minute fresh-water plants, of a green colour, without a siliceous epidermis. DEUTEROZOO'IDS (Gr. deuteros, second ; zoon, animal ; eidos, form). The zooids which are produced by gemmation from zooids. DEXTRAL (Lat. dextra, the right hand). Right-handed ; applied to the direc- tion of the spiral in the greater number of univalve shells. DIAPHRAGM (Gr. diaphragma, a partition). The " midriff," or the muscle which in Mammalia forms a partition between the cavities of the thorax and abdomen. DIASTEMA (Gr. dia, apart ; histemi, to place). A gap or interval, especially between teeth. DIASTOLE (Gr. diastello, I separate or expand). The expansion of a contrac- tile cavity siich as the heart, which follows its contraction or "systole." DIATOMACEJS (Gr. diatemno, I sever). An order of minute plants/which are provided with siliceous envelopes. DIBRANCHIATA (Gr. dis, twice ; bragchia, gill). The order of Cephalopoda (comprising the Cuttle-fishes, &c.) in which only two gills are present. DICYNODONTIA (Gr. dis, twice ; kuon, dog ; odous, tooth). An extinct order of Reptiles. DIDELPHIA (Gr. dis, twice ; delphus, womb). The subdivision of Mammals comprising the Marsupials. GLOSSARY. 58l DIGIT (Lat. dif/itus, a finger). A finger or toe. DIGITIGRADA (Lat. dig it us ; gradior, I walk). A subdivision of tbe Carrdvora. DIGITIGRADE. Walking upon the tips of the toes, and not upon the soles of the feet. DIMEROSOMATA (Gr. dis ; meros, part; soma, body). An order of Araclmida, comprising the true Spiders, so called from the marked division of the body into two regions, the cephalothorax and abdomen. The name Araneida is often employed for the order. DIMYARY (Gr. dis, twice ; muon, muscle). Applied to those bivalve Molluscs (Lamellibranchiata) in which the shell is closed by two adductor muscles. DIOECIOUS (Gr. dis, twice ; oikos, house). Having the sexes distinct ; applied to species which consist of male and female individuals. DIPHYOZOOIDS. Detached reproductive portions of adult Calycophoridce^ an order of oceanic Hydrozoa. DIPHYODONT (Gr. du, twice; phuo, I generate; odous, tooth). Applied to those Mammals which have two sets of teeth. DIPNOI (Gr. dis, twice ; pnoe, breath). The order of fishes represented by the Lepidosiren. DIPTERA (Gr. dis, twice ; pteron, wing). An order of Insects characterised by the possession of two wings. DISCOID (Gr. diskos, a quoit ; eidos, form). Shaped like a round plate or quoit. DISCOPHORA (Gr. diskos, a quoit ; phero, I carry). This term is applied to the Medusae, or Jelly-fishes, from their form ; and is sometimes used to designate the order of the Leeches (Hirudinea), from the suctorial discs which these animals possess, DISSEPIMENTS (Lat. dissepio, I partition off). Partitions. Used in a restricted sense to designate certain imperfect transverse partitions, which grow from the septa of many corals. DISTAL. Applied to the quickly growing end of the hydrosoma of a Hydro- zob'n; the opposite, or ".proximal," extremity growing less rapidly, and being the end by which the organism is fixed, when attached at all. DIURNAL (Lat. dies, day). Applied to animals which are active during the day. DIVERTICULUM (Lat. diverticulum, a bye-road). A lateral tube with a blind extremity, springing from the side of another tube. DORSAL (Lat. dorsum, back). Connected with the back. DORSIBRANCHIATE (Lat. dorsum, the back ; Gr. Iragchia, gill). Having ex- ternal gills attached to the back; applied to certain Annelides and Molluscs. The term is of mongrel composition, and " notobranchiate " is more correctly employed. ECDERON (Gr. ek, out ; deros, skin). The outer plane of growth of the ex- ternal integumentary layer (viz., the ectoderm or epidermis). ECDYSIS (Gr. ekdusis, a stripping off). A shedding or moulting of the skin. ECHINOCOCCI (Gr. echinos, a hedgehog ; kokkos, a berry). The larval iorms (scolices) of the tapeworm of the dog (Tcenia eddnococcus], commonly known as "hydatids." ECHINODERMATA (Gr. echinos ; and derma, skin). A class of animals com- prising the Sea-urchins, Star-fishes, and others, most of which have spiny skins. ECHINOIDEA (Gr. echinos ; and eidos, form). An order of EcldnodermaM, com- prising the Sea-urchins. ECHINULATE. Possessing spines. ECTOCYST (Gr. ektos, outside ; kustis, a bladder). The external investment of the ccencecium of a Polyzob'n. ECTODERM (Gr. ektos, and derma, skin). The external integumentary layer of the Coelenterata. ECTOSARC (Gr. ektos; sarx, flesh). The outer transparent sarcode-layer of cer- tain Rhizopods, such as the A mcela. EDENTATA (Lat. e-} without; dens, tooth). An order of Mammalia often called Bruta. 582 GLOSSARY. EDENTULOUS. Toothless, without any dental apparatus. Applied to the mouth of any animal, or to the hinge of the bivalve Molluscs. EDRIOPHTHALMATA (Gr. hedraios, sitting; ophthalmos, eye). The division of Crustacea in which the eyes are sessile, and are not supported upon stalks. ELASMOBRANCHII (Gr. elasma, a plate ; bragchia, gill). An order of Fishes, including the Sharks and Rays. ELYTRA (Gr. elutron, a sheath). The chitinous anterior pair of wings in Beetles, which form cases for the posterior membranous wings. Also ap- plied to the scales or plates on the back of the Sea-mouse (A phrodite). EMBRYO (Gr. en, in ; bi~uo, I swell). The earliest stage at which the young animal is recognisable in the impregnated ovum. ENCEPHALON (Gr. eycephalos, brain). The portion of the cerebro-spinal ner- vous axis contained within the cranium. ENCEPHALOUS (Gr. en, in ; kephale, the head). Possessing a distinct head. • Usually applied to all the Mollusca proper, except the Lamellibranchiata. ENCYSTATION (Gr. en, in ; kustis, a bag). The transformation undergone by certain of the Protozoa, when they become motionless, and surround them- selves by a thick coating or cyst. ENDERON (Gr. en, in ; deros, skin). The inner plane of growth of the outer integumentary layer (viz., the ectoderm, or epidermis). ENDOCYST (Gr. endon, within; kustis, a bag). The inner membrane or integu- mentary layer of a Polyzob'n. In Cristatella, where there is no " ectocyst," the endocyst constitutes the entire integument. ENDODERM (Gr. endon; and derma, skin). The inner integumentary layer of the Ccelenterata. ENDOPODITE (Gr. endon; and pous, foot). The inner of the two secondary joints into which the typical limb of a Crustacean is divided. ENDOSARC (Gr. endon; and sarx, flesh). The inner molecular layer of sarcode in the Amoeba, and other allied Rhizopods. ENDOSKELETON (Gr. endon, and skeletos, dry). The internal hard structures, such as bones, which serve for the attachment of muscles, or the protection of organs, and which are not a mere hardening of the integument. ENSLFORM (Lat. ensis, a sword ; forma, shape). Sword-shaped. ENTOMOPHAGA (Gr. entoma, insects ; phago, I eat). A section of the Marsu- pialia. ENTOMOSTRACA (Gr. entoma, insects ; ostrakon, a shell). Literally Shelled Insects, applied to a division of Crustacea. ENTOZOA (Gr. entos, within ; zob'n, animal). Animals which are parasitic in the interior of other animals. EOCENE (Gr. eos, dawn ; kainos, new or recent). The lowest division of the Tertiary Rocks, in which species of existing shells are to a small extent represented. EPIDERMIS (Gr. epi, upon ; derma, the true skin). The outer non-vascular layer of the skin, often called the scarf-skin or cuticle. EPIMERA (Gr. epi, upon ; meron, thigh). The lateral pieces of the dorsal arc of the somite of a Crustacean. EPIPODIA (Gr. epi, upon ; pous, the foot). Muscular lobes developed from the lateral and upper surfaces of the " foot " of some Molluscs. EPIPODITE (Gr. epi, upon ; pous, foot). A process developed upon the basal joint, or " protopodite," of some of the limbs of certain Crustacea. EPISTERNA (Gr. epi, upon ; sternon, the breast-bone). The lateral pieces of the inferior or ventral arc of the somite of a Crustacean. EPISTOME (Gr. epi; and stoma, mouth). A valve-like organ which arches over the mouth in certain of the Polyzoa. EPITHECA (Gr. epi; and theke, a sheath). A continuous layer surrounding the thecse in some Corals, and being the external indications of tabulae. EPIZOA (Gr. epi, upon ; zob'n, animal). Animals which are parasitic upon other animals. In a restricted sense, a division of Crustacea which are parasitic upon fishes. EQUILATERAL (Lat. (equus, equal ; latus, side). Having its sides equal. Us- ually applied to the shells of the Brachiopoda. When applied to the spiral GLOSSARY. 583 shells of the Foraminifera, it means that all the convolutions of the shell lie in the same plane. EQUIVALVE (Lat. cequus, equal; valvce, folding doors). Applied to shells which are composed of two equal pieces or valves. ERRANTIA (Lat. erro, I wander). An order of Annelida, often called Nereidea, distinguished by their great locomotive powers. EURYPTERIDA (Gr. eurus, broad ; pteron, wing). An extinct sub-order of Crustacea. EXOPODITE (Gr. exo, outside ; pous, foot). The outer of the two secondary joints into which the typical limb of a Crustacean is divided. EXOSKELETON (Gr. exo, outside ; skeletos, dry). The external skeleton, which is constituted by a hardening of the integument, and is often called a " dermoskeleton." FASCICULATED (Lat. fasciculus, a bundle). Arranged in bundles. FAUNA (Lat. Fatini, the rural deities of the Romans). The general assem- blage of the animals of any region or district. FEMUR. The thigh-bone, intervening between the pelvis and the bones of the leg proper (tibia and./i&a/a). FIBULA (Lat. a brooch). The outermost of the two bones of the leg in the higher Vertebrata; corresponding to the ulna of the fore-arm. FILIFORM (Lat. filum, a thread ; forma, shape). Thread-shaped. FISSILINGUIA (Lat../ittdo, I cleave ; lingua, tongue). A division of Lacertilia, with bifid tongues. FISSION (L&t.Jindo, I cleave). Multiplication by means of a process of self- division. FISSIPAROUS (Lat. findo; and^an'o, I produce). Giving origin to fresh struc- tures by a process of fission. FISSIROSTRES (Lat. Jindo, I cleave ; rostrum, beak). A sub-order of the Perching-birds. FLAGELLUM (Lat. for whip). The lash-like appendage exhibited by many In- fusoria, which are therefore said to be " flagellate." FLORA (Lat. Flora, the goddess of flowers). The general assemblage of the plants of any region or district. FOOT- JAWS. The limbs of Crustacea, which are modified to subserve mastica- tion. FOOT-SECRETION. The term applied by Mr Dana to the sclerobasic corallum of certain Actinozoa. FOOT- TUBERCLES. The unarticulated appendages of the Annelida, often called parapodia. FORAMINIFERA (Lat. foramen, an aperture ; fero, I carry). An order of Pro- tozoa, usually characterised by the possession of a shell perforated by numerous pseudopodial apertures. FRUGIVOROUS (Lat. frux, fruit ; voro, I devour). Living upon fruits. FURCULUM (Lat. dim. of furca, a fork). The " merry-thought " of birds, or the V-shaped bone formed by the united clavicles. FUSIFORM (Lat. fusus, a spindle; and forma, shape). Spindle-shaped, or pointed at both ends. GALLINACEI (Lat. gallina, a fowl). Sometimes applied to the whole order of the Rasorial Birds, but properly restricted to that section of the order of which the common Fowl is a typical example. GANGLION (Gr. gagglion, a knot). A mass of nervous matter containing nerve- cells, giving origin to nerve-fibres. GANOID (Gr. ganos, splendour, brightness). Applied to those scales or plates which are composed of an inferior layer of true bone covered by a superior layer of polished enamel. GANOIDEI. An order of Fishes. GASTEROPODA (Gr. gaster, stomach ; pous, foot). The class of the Mollusca comprising the ordinary univalves, in which locomotion is usually effected by a muscular expansion of the under surface of the body (the " foot "). 584 GLOSSARY. GEMMJE (gemma, a bud). The buds produced by any animal, whether de- tached or not. GEMMATION. The process of producing new structures by budding. GEMMIPAROUS (Lat. gemma, a bud ; pario, I produce). Giving origin to new structures by a process of budding. GEMMULES (Lat. dim. of gemma). The ciliated embryos of many Coelenterata ; also the seed-like reproductive bodies or "spores " of Spongilla. GEPHYREA (Gr. gephura, a bridge). A class of the Anarthropoda, comprising the Spoon-worms (Sipunculus) and their allies. GIZZARD. A muscular division of the stomach in Birds, Insects, &c. GLADIUS (Lat. a sword). Applied to the horny endoskeleton or "pen" of certain Cuttle-fishes. GLENOID (Gr. glene, a cavity; eidos, form). A shallow cavity; applied espe- cially to the shallow articular cavity in the shoulder-blade to which the head of the humerus is jointed. GNATHITES (Gr. gnathos, a jaw). The masticatory organs of Crustacea. GONOBLASTIDIA (Gr. gonos, offspring ; blastidion, dim. of blastos, a bud). The processes which carry the reproductive receptacles, or " gonophores," in many of the Hydrozoa. GONOCALYX (Gr. gonos; and kalux, cup). The swimming-bell in a medusiform gonophore, or the same structure in a gonophore which is not detached. GONOPHORE (Gr. gonos, and phero, I carry). The generative buds, or recep- tacles of the reproductive elements, in the Hydrozoa, whether these become detached or not. GONOSOME (Gr. gonos ; and soma, body). Applied as a collective term to the reproductive zooids of a Hydrozoon. GONOTHECA (Gr. gonos; and theke, a case). The chitinous receptacle within which the gonophores of certain of the Hydrozoa are produced. GRALLATORES ( Lat. grallce, stilts). The order of the long-legged Wading Birds. GRANIVOROUS (Lat. granum, a grain or seed ; voro, I devour). Living upon grains or other seeds. GRAPTOLITID.S; (Gr. grapho, I write ; lithos, stone). An extinct sub-class of the Hydrozoa. GREGARINIDA (Lat. gregarius, occurring in numbers together). A class of the Protozoa. GUARD. The cylindrical fibrous sheath with which the internal chambered shell (phragmacone) of a Belemnite is protected. GYMNOL.&MATA (Gr. gumnos, naked ; laima, the throat). An order of the Polyzoa in which the mouth is devoid of the valvular structure known as the " epistome." GYMNOPHIONA (Gr. gumnos, naked; ophis, a snake). The order of the Am- phibia comprising the snake-like Ccecilice. GYMNOPHTHALMATA (Gr. gumnos; and ophthalmos, the eye). Applied by Ed- ward Forbes to those Medusce in which the eye-specks at the margin of the disc are unprotected. The division is now abandoned. GYMNOSOMATA (Gr. gumnos; and soma, the body). The order of Pteropoda in which the body is not protected by a shell. GYNOPHORES (Gr. gune, woman ; phero, I carry. The generative buds, or gonophores, of Hydrozoa, which contain ova alone, and differ in form from those which contain spermatozoa. GYRENCEPHALA (Gr. guroo, I wind about; egkephalos, brain). Applied by Owen to a section of the Mammalia in which the cerebral hemispheres are abundantly convoluted. (Gr. haima, blood). Connected with the bloodvessels, or with the circulatory system. H.«;MATOCRYA (Gr. haima, blood ; cruos, cold). Applied by Owen to the "cold-blooded" Vertebrates — Viz., the Fishes, Amphibia, and Reptiles. H^BMATOTHERMA (Gr. haima, blood ; thermos, warm). Applied by Owen to the "warm-blooded" Vertebrates — viz., Birds and Mammals. HALLUX (Lat. allex, the thumb or great toe). The innermost of the five GLOSSARY. 585 digits which normally compose the land foot of a Vertebrate animal. In man, the great toe. HALTERES (Gr. halt?res, weights used by athletes to steady themselves in leaping). The rudimentary filaments or "balancers" which represent the posterior pair of wings in the Diptera, an order of Insects. HAUSTELLATE (Lat. haurio, I drink). Adapted for sucking or pumping up fluids ; applied to the mouth of certain Crustacea and Insecta. HECTOCOTYLUS (Gr. hekaton, a hundred ; kotulos, a cup). The metamor- phosed reproductive arm of certain of the male Cuttle-fishes. In the Argonaut the arm becomes detached, and was originally described as a parasitic worm. HKLMINTHOID (Gr. helmins, an intestinal worm). Worm-shaped, vermi- form. HEMELYTRA (Gr. hemi, half ; elutron, a sheath). The wings of certain insects, in which the apex of the wing is membranous, whilst the inner portion is chitinous, and resembles the elytron of a beetle. HEMIMETABOLIC (Gr. hemi, half ; metaljole, change). Applied to those Insects which undergo an incomplete metamorphosis. HEMIPTERA (Gr. hemi; and pteron, wing). An order of Insects in which the anterior wings are sometimes "hemelytra." HERMAPHRODITE (Gr. Hermes, Mercury; Aphrodite, Venus). Possessing the characters of both sexes combined. HETEROCERCAL (Gr. heteros, diverse; kerkos, tail). Applied to the tail of Fishes when it is unsymmetrical, or composed of two unequal lobes. HETEROGANGLIATE (Gr. heteros, diverse ; gagglion, a knot). Possessing a nervous system in which the ganglia are scattered and unsymmetrical (as in the MoUusca, for example). HETEROMORPHIC (Gr. heteros; morphe, form). Differing in form or shape. HETEROPHAGI (Gr. heteros, other ; phago, I eat). Applied to Birds the young of which are born in a helpless condition, and require to be fed by the parents for a longer or shorter period. HEXAPOD (Gr. hexa, six ; pous, foot). Possessing six legs ; applied to the Insecta. HILUM (Lat. hilum, a little thing). A small aperture (as in the gemmules of sponges), or a small depression (as in Noctiluca). HIRUDINEA (Lat. hirudo, a horse-leech). The order of Annelida comprising the Leeches. HISTOLOGY (Gr. histos, a web ; logos, a discourse). The study of the tissues ; more especially of the minuter elements of the body. HOLOCEPHALI (Gr. hoJos, whole ; kephale, head). A sub-order of the Elasmo- branckii comprising the Chimcerce. HOLOMETABOLIC (Gr. holos, whole; metalole, change). Applied to Insects which undergo a complete metamorphosis. HOLOSTOMATA (Gr. holos, whole ; stoma, mouth). A division of Gasteropodous Molluscs, in which the aperture of the shell is rounded, or "entire." HOLOTHUROIDEA (Gr. holotliourion ; and eidos, form). An order of Echinoder- mata comprising the Trepangs. HOMOCERCAL (Gr. homos, same ; kerkos, tail). Applied to the tail of Fishes when it is symmetrical, or composed of two equal lobes. HOMOGANGLIATE (Gr. homos, like ; gagglion, a knot). Having a nervous sys- tem in which the ganglia are symmetrically arranged (as in the Annulosa, for example). HOMOLOGOUS (Gr. homos; and logos, a discourse). Applied to parts which are constructed upon the same fundamental plan. HOMOMORPHOUS (Gr. homos; and morphe, form). Having a similar external appearance or form. HUMERUS. The bone of the upper arm (brachium) in the Vertebrates. HYALINE (Gr. hualos, crystal). Crystalline or glassy. HYDATIDS (Gr. hudatis, a vesicle). The vesicle containing the larval forms (Echinococci) of the tapeworm of the dog. HYDRAFORM. Resembling the common fresh-water polype (Hydra} in form. 586 GLOSSARY. HYDROCAULUS (Gr. hudra, a water-serpent, and kaulos, a stem). The main stem of the coenosarc of a Hydrozoon. HYDROCYSTS (Gr. hudra ; and kustis, a cyst). Curious processes attached to the coenosarc of the Physophoridce, and termed " feelers " (fiikler and taster of the Germans). HYDRCECIUM (Gr. hudra ; and oikos, a house). The chamber into which the coenosarc in many of the Calycophoridce can be retracted. HYDROIDA (Gr. hudra; and eidos, form). The sub-class of the Hydrozoa, which comprises the animals most nearly allied to the Hydra. HYDROPHYLLIA (Gr. hudra ; and phyllon, a leaf). Overlapping appendages or plates which protect the polypites in some of the Oceanic Hydrozoa (Calycophoridce and Physophoridce). They are often termed " bracts," and are the " deckstucke " of the Germans. HYDRORHIZA (Gr. hudra ; and rhiza, root). The adherent base or proximal extremity of any Hydrozoon. HYDROSOMA (Gr. hudra; and soma, body). The entire organism of any Hydrozoon. HYDROTHECA (Gr. hudra; and theke, a ease). The little cbitinous cups in which the polypites of the Sertularida and Campanularida are protected. HYDROZOA (Gr. hudra ; and zob'n, animal). The class of the Ccelenterata, which comprises animals constructed after the type of the Hydra. HYMENOPTERA (Gr. humen, a membrane ; pteron, a wing). An order of In- sects (comprising Bees, Ants, &c.) characterised by the possession of four membranous wings. HYOID (Gr. U; eidos, form). The bone which supports the tongue in Ver- tebrates, and derives its name from its resemblance in man to the Greek letter U. HYPOSTOME (Gr. hupo, under ; stoma, mouth). The upper lip, or " labrum," of certain Crustacea (e.g., Trilobites). HYRACOIDEA (Gr. hurax, a shrew ; eidos, form). An order of the Mammalia constituted for the reception of the single genus Hi/rax. ICHTHYODORULITE (Gr. ichtlms, fish ; dorus, spear ; lithos, stone). The fossil fin-spines of Fishes. ICHTHYOMORPHA (Gr. ichthus ; morpJie, shape). An order of Amphibians, often called Urodela', comprising the fish-like Newts, &c. ICHTHYOPHTHIRA (Gr. ichthus ; phthfir, a louse). An order of Crustacea com- prising animals which are parasitic upon Fishes. ICHTHYOPSIDA (Gr. ichthus ; opsis, appearance). The primary division of Verlebrata, comprising the Fishes and Amphibia. Often spoken of as the Branchiate Vertebrata. ICHTHYOPTERYGIA (Gr. ichthus ; pterux, wing). An extinct order of Reptiles. ICHTHYOSAURI A (Gr. ichth us; sa^'Jra, lizard). Synonymous with Ichtkyopterygia. ILIUM. The haunch-bone, one of the bones of the pelvic arch in the higher Vertebrates. IMAGO (Lat. an image or apparition). The perfect insect, after it has under- gone its metamorphoses. IMBRICATED. Applied to scales or plates which overlap one another like tiles. INCISOR (Lat. incido, I cut). The cutting teeth fixed in the intermaxillary bones of the Mammalia, and the corresponding teeth in the lower jaw. INEQUILATERAL. Having the two sides unequal, as in the case of the shells of the ordinary bivalves (Lamellibranchiata). When applied to the shells of the Foraminifera, it implies that the convolutions ot the shell do not lie in the same plane, but are obliquely wound round an axis. INEQUIVALVE. Composed of two unequal pieces or valves. INFUNDIBULUM (Lat. for funnel). The tube formed by the coalescence or apposition of the epipodia in the Cephalopoda. Commonly termed the "funnel," or "siphon." INFUSORIA (Lat. infusum, an infusion). A class of Protozoa, so called be- cause they are often developed in organic infusions. INGUINAL (Lat. inguen, groin). Connected with, or situated upon, the groin. GLOSSARY. 587 INOPERCULATA (Lat. in, without ; operculum, a lid). The division of pul- monate Gasteropoda in which there is no shelly or horny plate (operculum) by which the shell is closed when the animal is withdrawn within it. INSECTA (Lat. inseco, I cut into). The class of Articulate animals commonly known as Insects. IXSECTIVORA (Lat. insectum, an insect ; voro, I devour). An order of Mammals. INSECTIVOROUS. Living upon Insects. INSESSORES (Lat. insedeo, I sit upon). The order of the Perching Birds, often called Passeres. INTERAMBULACRA. The rows of plates in an Echinoderm which are not per- forated for the emission of the " tube-feet." INTERMAXILL.E, or PR^EMAXILL^E. The two bones which are situated between the two superior maxillso in Vertebrata. In man, and some monkeys, the prse- maxillse anchylose with the maxillse, so as to be irrecognisable in the adult. INTUSSUSCEPTION (Lat. intus, within ; suscipio, I take up). The act of taking foreign matter into a living being. INVERTEBRATA (Lat. in, without ; vei'tebra, a bone of the back). Animals without a spinal column or backbone. ISCHIUM (Gr. ischion, the hip). One of the bones of the pelvic arch in Ver- tebrates. ISOPODA (Gr. isos, equal ; poda, feet). An order of Crustacea in which the feet are like one another and equal. JUGULAR (Lat. jiigulum, the throat). Connected with, or placed xvpon, the throat. Applied to the ventral fins of fishes when they are placed beneath or in advance of the pectorals. KAINOZOIC (Gr. Icainos, recent ; zoe, life). The Tertiary period in Geology, comprising those formations in which the organic remains approximate more or less closely to the existing fauna and flora. KERATODE (Gr. Jceras, horn ; eidos, form). The horny substance of which the skeleton of many sponges is made up. KERATOSA. The division of Sponges in which the skeleton is composed of keratode. LABIUM (Lat. for lip). Restricted to the lower lip of Articulate animals. LABRUM (Lat. for lip). Restricted to the upper lip of Articulate animals. LABYRINTHODONTIA (Gr. labyrinthos, a labyrinth; ^do^ls, tooth). An extinct order of Amphibia, so called from the complex microscopic structure of the teeth. LACERTILIA (Lat. lacerta, a lizard). An order of Reptilia comprising the Lizards and Slow-worms. L.EMODIPODA (Gr. laima, throat ; dis, twice ; poda, feet). An order of Crus- tacea, so called because they have two feet placed far forwards, as it were under the throat. LAMELLIBRANCHIATA (Lat. lamella, a plate; Gr. bragcfiia, gill). The class of Mollusca, comprising the ordinary bivalves, characterised by the possession of lamellar gills. LAMELLIROSTRES (Lat. lamella, a plate ; rostrum,, beak). The flat-billed Swimming Birds (Natatores), such as Ducks Geese, Swans, &c. LARVA (Lat. a mask). The insect in its first stage after its emergence from the egg, when it is usually very different from the adult. LARYNX. The upper part of the wind-pipe, forming a cavity with appropri- ate muscles and cartilages, situated beneath the hyoid bone, and concerned in Mammals in the production of vocal sounds. LENTICULAR (Lat. lens, a bean). Shaped like a biconvex lens. LEPIDOPTERA (Gr. hpis, a scale ; pteron, a wing). An order of Insects, com- prising Butterflies and Moths, characterised by possessing four wings which are usually covered with minute scales. LEPIDOTA (Gr. lepis, a scale). Formerly applied to the order Dipnoi, con- taining the Mud-fishes (Lepidosiren). 588 GLOSSARY. LEPTOCARDIA (Gr. leptos, slender, small ; cardia, heart). The name given by Miiller to the order of Fishes comprising the Lancelot, now called Pharyn- gobranchii. LIGAMENTDM NUCHJ3 (Lat. nucha, the nape of the neck). The band of elastic fibres by which the weight of the head in Mammalia is supported. LIGULA (Lat. Ligula, a little tongue). The upper flexible portion of the labium or lower lip in Insects. LINGUAL (Lat. lingua, the tongue). Connected with the tongue. LISSENCEPHALA (Gr. lissox, smooth ; eakepheUot, brain). A primary division of Mammalia, according to Owen, in which the cerebral hemispheres are smooth or have few convolutions. LITHOCYSTS (Gr. lithos, a stone ; kustis, a cyst). The sense-organs or " mar- ginal bodies " of the Lucernarida or Steganopldhalmate Medusce. LONGIPENNAT.E (Lat. longus, long ; penna, wing). A group of the Natatorial birds. LONGIROSTRES (Lat. longus ; rostrum, beak). A group of the Wading birds. LOPHOPHORE (Gr. lophos, a crest ; andphero, I carry). The disc or stage upon which the tentacles of the Polyzoa are borne. LOPHYROPODA (Gr. lopJwuros, having stiff hairs ; and poda, feet). An order of Crustacea. LORICA (Lat. a breast-plate). Applied to the protective case with which certain Infusoria are provided. LORICATA (Lat. lorica, a cuirass). The division of Reptiles comprising the Chelonia and Crocodilia, in which bony plates are developed in the skin (derma), LUCERNARIDA (Lat. lucerna, a lamp). An order of the Hydrozoa. LUMBAR (Lat. lumbus, loin). Connected with the loins. LUNATE (Lat. luna, moon). Crescentic in shape. LYENCEPHALA (Gr. luo, I loose ; egkephalos, brain). A primary division of Mammals, according to Owen. MACRODACTYLI (Gr. maJcros, long ; daktulos, a finger). A group of the Wading birds. MACRURA (Gr. makros, long; oura, tail). A tribe of Decapod Crustaceans with long tails (e.g., the Lobster, Shrimp, &c.) MADREPORIFORM. Perforated with small holes, like a coral ; applied to the tubercle by which the ambulacral system of the Echinoderms mostly com- municates with the exterior. MALACOSTRACA (Gr. malakos, soft ; ostrakon, shell). A division of, Crustacea. Originally applied by Aristotle to the entire class Crustacea, because their shells were softer than those of the Mollmca. MALLOPHAGA (Gr. mallos, a fleece ; pliago, I eat). An order of Insects which are mostly parasitic upon birds. MAMMALIA (Lat. mamma, the breast). The class of Vertebrate animals which suckle their young. MANDIBLE (Lat. mandibulum, a jaw). The upper pair of jaws in Insects ; also applied to one of the pairs of jaws in Crustacea and Spiders, to the beak of Cephalopods, the lower jaw of Vertebrates, &c. MANTLE. The external integument of most of the Mollusca, which is largely- developed, and forms a cloak in which the viscera are protected. Techni- cally called the " pallium." MANUBRIUM (Lat. a handle). The polypite which is suspended from the roof of the swimming-bell of a Medusa, or from the gonocalyx of a medusiform gonophore amongst the Hydrozoa. MANUS (Lat. the hand). The hand of the higher Vertebrates. MARSIPOBRAXCHII (Gr. marsipos, a pouch ; Iragchia, gill). The order of Fishes comprising the Hag-tishes and Lampreys, with pouch-like gills. MARSUPIALIA (Lat. marsupium, a pouch). An order of Mammals in which the females mostly have an abdominal pouch in which the young are carried. MASTAX (Gr. mouth). The muscular pharynx or "buccal funnel" into which the mouth opens in most of the Rotifera. MASTICATORY (Lat. mastico, I chew). Applied to parts adapted for chewing. GLOSSARY. 589 MAXILLA (Lat. jaws). The inferior pair or pairs of jaws in the Arthropoda ([nsects, Crustacea, &c.) The upper jaw-bones of Vertebrates. MAXILLIPKDES (Lat. maxillce, jaws ; pes, the foot). The limbs in Crustacea and Mynapoda which are converted into masticatory organs, and are com- monly called "foot-jaws." MEDULLA (Lat. marrow). Applied to the marrow of bones, or to the spinal cord, with or without the adjective Aocoa PlNNlGRADA (Lat. pinna, a feather ; gradior, I walk). The group of Carni- vora comprising the Seals and Walruses, adapted for an aquatic life. Often called Pinnipedia. PINNULE (Lat. dim. of pinna}. The lateral processes of the arms of Crinoids. PISCES (Lat. piscis, a fish). The class of Vertebrates comprising the Fishes. PLACENTA (Lat. a cake). The "after-birth," or the organ by which a vascu- lar connection is established in the higher Mammalia between the mother and the foetus. PLACENTAL. Possessing a placenta ; or connected with the placenta. PLACOID (Gr. plax, a plate ; eidos, form). Applied to the irregular bony plates, grains, or spines which are found in the skin of various fishes (Elas- mobranchii). PLAGIOSTOMI (Gr. plagios, transverse ; stoma, mouth). The Sharks and Rays, in which the mouth is transverse, and is placed on the under surface of the head. PLANAEIDA (Gr. plane, wandering). A sub-order of the Turbellaria. PLANTIGRADE (Lat. planta, the sole of the foot ; gradior, I walk). Applying the sole of the foot to the ground in walking. PLANULA (Lat. planus, flat). The oval ciliated embryo of certain of the Hy- drozoa. PLASTRON. The lower or ventral portion of the bony case of the Chelonians. PLATYELMIA (Gr. plains, broad ; and helmins, an intestinal worm). The division of Scolecida comprising the Tapeworms, &c. PLATYRHINA (Gr. plains, broad ; rhines, nostrils). A group of the Quadrumana. PLEURA (Gr. the side). The serous membrane covering the lung in the air- breathinsr Vertebrates. PLEURON (Gr. pletiron, a rib). The lateral extensions of the shell of Crustacea. PLUTEUS (Lat. a pent-house). The larval form of the Echinoidea. PNEUMATIC (Gr. pneuma, air). Filled with air. PNEUMATOCYST (Gr. pneuma, air; and kustis, cyst). The air-sac or float of certain of the Oceanic Hydrozoa (Physophoridce). PNEUMATOPHORE (Gr. pneuma, air; and phero, I carry). The proxima dilatation of the coenosarc in the Physophoridce which surrounds the pneumatocyst. PNEUMOSKELETON (Gr. pneuma; and sJceletos, dry). The hard structures which are connected with the breathing organs (e.g., the shell of Molluscs). PODOPHTHALMATA (Gr. pous, foot ; and ophthalmos, eye). The division of Crustacea in which the eyes are borne at the end of long foot-stalks. PODOSOMATA (Gr pous* foot ; soma, body). An order of Arachnida. POEPHAGA (Gr. poe, grass ; pliago, I eat). A group of the Marsupials. POLLEX (Lat. the thumb). The innermost of the five normal digits of the anterior limb of the higher Vertebrates. In man, the thumb. POLYCYSTINA (Gr. polus, many ; and kustis, a cyst). An order of Protozoa, with foraminated siliceous shells. POLYGASTRICA (Gr. polus ; and gaster, stomach). The name applied by Ehrenberg to the Infusoria, under the belief that they possessed many stomachs. POLYPARY. The hard chitinous covering secreted by many of the Hydrozoa. POLYPE (Gr. polus, many ; pous, foot). Restricted to the single individual of a simple Actinozoon, such as a Sea-anemone, or to the separate zob'ids of a compound Actinozoon. Often applied indiscriminately to any of the Ccelen- teraia, or even to the Polyzoa. GLOSSARY. 595 POLYPIDE. The separate zooid of a Polyzoon. POLYPIDOM. The dermal system of a colony of a Hydrozoon, or PolyzoSn. POLYPITE. The separate zooid of a Hydrozoon. POLYSTOME (Gr. polus, many ; and stoma, mouth). Having many mouths ; applied to the Acinetce amongst the Protozoa. POLYTHALAMOUS (Gr. polus ; and thalamos, chamber). Having many cham- bers; applied to the shells of Foraminifera and Cephalopoda. POLYZOA (Gr. polus ; and zoon, animal). A division of the Molluscoida, com- prising compound animals, such as the Sea-mat. Sometimes called Bryozoa. POLYZOARIUM. The dermal system of the colony of a Polyzoon (= Poly- pidom). PORCELLANOUS. Of the texture of porcelain. PORIFERA (Lat. porus, a pore ; and Jero, I carry). Sometimes used to desig- nate the Foraminifera, or the Sponges. POST-ANAL. Situated behind the anus. POST (ESOPHAGEAL. Situated behind the gullet. POST-ORAL. Situated behind the mouth. PR^I-MAXILL^E (see Interrnaxitlce). PR^MOLARS (Lat. prce, before ; molares, the grinders). The molar teeth of Mammals which succeed the molars of the milk set of teeth. In man, the bicuspid teeth. PR^E-CESOPHAGEAL. Situated in front of the gullet. PR^E-STERNUM. The anterior portion of the breast-bone, corresponding with the manubrium sterni of human anatomy, and extending as far as the point of articulation of the second rib. PRESSIROSTRES (Lat. pressus, compressed; rostrum, beak). A group of the Grallatorial Birds. PROBOSCIDEA (Lat. proboscis, the snout). The order of Mammals comprising the Elephants. PROBOSCIS (Lat. or Gr. the snout). Applied to the spiral trunk of Lepidopter- ous Insects, to the projecting mouth of certain Crinoids, and to the central polypite in the Medusae. PROCCELOUS (Gr. pro, front; Icoilos, hollow). Applied to vertebrae, the bodies of which are hollow or concave in front. PROGLOTTIS (Gr. for the tip of the tongue). The generative segment or joint of a Tapeworm. PRO-LEGS. The false abdominal feet of Caterpillars. PRONATION (Lat. pronus, lying on the face, prone). The act of turning the palm of the hand downwards. PROPODIDM (Gr. pro, before ; pous, foot). The anterior part of the foot in Molluscs. PROSCOLEX (Gr. pro, before ; skolex, worm). The first embryonic stage of a Tapeworm. PROSOBRANCHIATA (Gr. proson, in advance of ; bragchia, a gill). A division of Gasteropodous Molluscs in which the gills are situated in advance of the heart. PROSOMA (Gr. pro, before ; soma, body). The anterior part of the body. PROTHORAX (Gr. pro ; and thorax, chest). The anterior ring of the thorax of insects. PROTOPODITE (Gr. protos, first ; and pous, foot). The basal segment of the typical limb of a Crustacean. PROTOPHYTA (Gr. protos; and phuton, plant). The lowest division of plants. PROTOPLASM (Gr. protos; and plasso, I mould). The elementary basis of or- ganised tissues. Sometimes used synonymously for the "sarcode" of the Protozoa. PROTOZOA (Gr. protos; and zoon, animal). The lowest division of the animal kingdom. PROVENTRICULUS (Lat. pro, in front of; ventriculus, dim. of venter, belly). The cardiac portion of the stomach of birds. PROXIMAL (Lat. prommus, next). The slowly-growing, comparatively-fixed extremity of a limb or of an organism. GLOSSARY. PSALTEEIUM (Lat. a stringed instrument). The third stomach of Ruminants. (See Omasum.) PSEUDEMBRYO (Gr. pseudos, false ; embruon, embryo). The larval form of an Echinoderm. PSEUDOBRANCHIA (Gr. pseudos, false ; bragchia, gill). A supplementary gill found in certain fishes, which receives arterialised blood only, and does not, therefore, assist in respiration. PSEUDOH^EMAL (Gr. pseudos, false ; and haima, blood). Applied to the vas- cular system of Annelida. PSEUDO-HEARTS. Certain contractile cavities connected with the atrial system of Brackiopoda, and long considered to be hearts. PsEUDO-NAViCELLyE (Gr. pseudos, false ; and Navicula, a genus of Diatoms). The embryonic forms of the Gregarinidce, so called from their resemblance in shape to the Navicula. PSEUDOPODIA (Gr. pseudos; and pous, foot). The extensions of the body- substance which are put forth by the llhizopoda at will, and which serve for locomotion and prehension. PSEUDOVA (Gr. pseudos; Lat. ovum, egg). The egg-like bodies from which the young of the viviparous Aphis are produced. PTEROPODA (Gr. pteron, wing ; and pous, foot). A class of the Mollusca which swim by means of fins attached near the head. PTEROSAURIA (Gr. pteron, wing ; saura, lizard). An extinct order of Reptiles. PUBIS (Lat. pubes, hair). The share-bone ; one of the bones which enter into the composition of the pelvic arch of Vertebrates. PULMONARIA. A division of Arachnida which breathe by means of pulmo- nary sacs. PULMONATE. Possessing lungs. PULMONIFERA (Lat. pulmo, a lung ; and fero, I carry). The division of Mollusca which breathe by means of a pulmonary chamber. PULMOGASTEROPODA (= Pulmonifera). PUPA (Lat. a doll). The stage of an insect immediately preceding its appear- ance in a perfect condition. In the pupa-stage it is usually quiescent — when it is often called a " chrysalis " — but it is sometimes active — when it is often called a "nymph." PYLORUS (Gr. puloros, a gate-keeper). The valvular aperture between the stomach and the intestine. PYRIFORM (Lat. pyrus, a pear; and/orma, form). Pear-shaped. QUA.DRUMANA (Lat. quatuor, four; manus, hand). The order of Mammals comprising the Apes, Monkeys, Baboons, Lemurs, &c. EADIATA (Lat. radius, a ray). Formerly applied to a large number of animals which are now placed in separate sub-kingdoms (e.g., the Ccelenterata, the Echinodermata, the Infusoria, &c. ) RADIOLARIA (Lat. radius, a ray). A division of Protozoa. RADIUS (Lat. a spoke or ray). The innermost of the two bones of the fore- arm of the higher Vertebrates. It carries the thumb, when present, and corresponds with the tibia of the hind-limb. RAMUS (Lat. a branch). Applied to each half or branch of the lower jaw or mandible of Vertebrates. RAPTORES (Lat. rapto, I plunder). The order of the Birds of Prey. RASORES (Lat. rado, I scratch). The order of the Scratching Birds (Fowls, Pigeons, &c.) RATITLE (Lat. rates, a raft). Applied by Huxley to the Cursorial Birds which do not fly, and have, therefore, a raft-like sternum without any median keel. RECTUM (Lat. rectus, straight). The terminal portion of the intestinal canal, opening at the surface of the body at the anus. REPTILIA (Lat. repto, I crawl). The class of the Vertebrata comprising the Tortoises, Snakes, Lizards, Crocodiles, &c. RETICULARIA (Lat. reticulum, a net). Employed by Dr Carpenter to desig- GLOSSARY. 597 nate those Protozoa, such as the Foraminifera, in which the pseudopodia run into one another and form a network. RFTICULUM (Lat. a net). The second division of the complex stomach of Ruminants, often called the "honeycomb bag." EEVERSED. Applied to spiral univalves, in which the direction of the spiral is the reverse of the normal — i.e., sinistral. RHIZOPHAGA (G-r. rhiza, root ; pJuigo, I eat). A group of the Marsupials. RHIZOPODA (Gr. rhiza, a root ; and pous, foot). The division of Protozoa com- prising all those which are capable of emitting pseudopodia. RHYNCHOLITES (Gr. rkunchos, beak ; and lithos, stone). Beak-shaped fossils, consisting of the mandibles of Cephalopoda. RODENTIA (Lat. rodo, I gnaw). An order of the Mammals ; often called Glires (Lat. glis, a dormouse). ROSTRUM (Lat. rostrum, beak). The "beak" or suctorial organ formed by the appendages of the mouth in certain insects. ROTATORIA (= Rotifera). ROTIFERA. (Lat. rota, wheel ; and fero, I carry). A class of the Scolecida (Annuloida) characterised by a ciliated "trochal disc." RUGOSA (Lat. rugosus, wrinkled). An extinct order of Corals. RUMEN (Lat. the throat). The first cavity of the complex stomach of Rumi- nants; often called the "paunch." RUMINANTIA (Lat. rumlnor, I chew the cud). The group of Hoofed Quadru- peds (Ungulata) which " ruminate" or chew the cud. SACRUM. The vertebrae (usually anchylosed) which unite with the haunch- bones (ilia] to form the pelvis. SAND-CANAL (= STONE-CANAL). The tube by which water is conveyed from the exterior to the ambulacral system of the Echinodermata. SARCODE (Gr. sarx, flesh ; eidos, form). The jelly-like substance of which the bodies of Protozoa are composed. It is an albuminous body containing oil- granules, and is sometimes called "animal protoplasm." SARCOIDS (Gr. sarx; and eidos, form). The separate amcebiform particles which in the aggregate make up the "flesh" of a Sponge. SAURIA (Gr. saura, a lizard). Any lizard-like Reptile is often spoken of as a "Saurian;" but the term is sometimes restricted to the Crocodiles alone, or to the Crocodiles and Lacertilians. SAUROBATRACHIA (Gr. saura ; batrachos, frog). Sometimes applied to the order of the tailed Amphibians (Urodela}. SAUROPSIDA (Gr. saura; and opsis, appearance). The name given by Huxley to the two classes of the Birds and Reptiles collectively. SAUROPTERYGIA (Gr. saura; pterux, wing). An extinct order of Reptiles, called by Huxley Plesiosauria, from the typical genus Plesiosaurus. SAURUR^E (Gr. saura; oura, tail). The extinct order of Birds comprising only the Archceopteryx. SCANSORES (Lat. scando, I climb). The order of the Climbing Birds (Parrots, Woodpeckers, &c.) SCAPHOGNATHITE (Gr. skaphos, boat ; and gnathos, jaw). The boat-shaped appendage (epipodite) of the second pair of maxillae in the Lobster ; the function of which is to spoon out the water from the branchial chamber. SCAPULA (Lat. for shoulder-blade). The shoulder-blade of the pectoral arch of Vertebrates ; in a restricted sense, the row of plates in the cup of Crinoids, which give origin to the arms, and are usually called the "axillary radial s." SCLERENCHYMA (Gr. skleros, hard ; and enchuma, tissue). The calcareous tissue of which a coral is composed. SCLERITES (Gr. skleros}. The calcareous spicules which are scattered in the soft tissues of certain A ctinozoa. SCLERO BASIC (Gr. skleros, hard ; basis, pedestal). The coral which is produced by the outer surface of the integument in certain Actinozoa (e.g., Red Coral), and forms a solid axis which is invested by the soft parts of the animal. It is called " foot-secretion" by Mr Dana. GLOSSARY. SCLERODERMIC (Gr. sJcleros ; and derma, skin). Applied to the corallum which is deposited within the tissues of certain Actinozoa, and is called "tissue- secretion " by JVlr Dana. SCLEROTIC (Gr. sJcleros, hard). The outer dense fibrous coat of the eye. SCOLECIDA (Gr. skolex, worm). A division of the Annuloida. SOOLEX (Gr. skolex). The embryonic stage of Tapeworm, formerly known as a "Cystic Worm." SCUTA (Lat. scutum, a shield). Applied to any shield-like plates ; especially to those which are developed in the integument of many Reptiles. SELACHIA or SELACHII (Gr. selachos, a cartilaginous fish, probably a shark The sub-order of Elasmobranckii comprising the Sharks and Dog-fishes. SEPIOSTAIRE. The internal shell of the Cuttle-fish, commonly known as the "cuttle- bone." SEPTA. Partitions. SERPENTIFORM. Resembling a serpent in shape. SERTULARIDA (Lat. sertum, a wreath). An order of Hydrozoa. SESSILE (Lat. sedo, I sit). Not supported upon a stalk or peduncle ; attached by a base. SET^E (Lat. bristles). Bristles, or long stiff hairs. SETIFEROUS. Supporting bristles. SETIGEROUS (= Setiferous). SETOSE. Bristly. SILICEOUS (Lat. silex, flint). Composed of flint. SINISTRAL (Lat. sinistra, the left hand). Left-banded; applied to the direc- tion of the spiral in certain shells, which are said to be " reversed." SINUS (Lat. sinus, a bay). A dilated vein or blood-receptacle. SIPHON (Gr. siphon, a tube). Applied to the respiratory tubes in the Mollusca; also to other tubes of different functions. SIPHONOPHORA (Gr. siphon; and phero, I carry). A division of the Hydrozoa, comprising the Oceanic forms (Calycophoridce and Physophoridce). SIPHONOSTOMATA (Gr. siphon; and stoma, mouth). The division of Gas- teropodous Molluscs, in which the aperture of the shell is not " entire," but possesses a notch or tube for the emission of the respiratory siphon. SIPHUNCLE (Lat. siphunculus, a little tube). The tube which connects together the various chambers of the shell of certain Cephalopoda (e.g., the Pearly Nautilus). SIPUNCULOIDEA (Lat. siphunculus, a little siphon). A class of Anarthropoda (Annulosa). SIRENIA (Gr. seiren, a mermaid). The order of Mammalia comprising the Dugongs and Manatees. SOLIDUNGULA (Lat. solidus, solid ; ungula, a hoof). The group of Hoofed Quadrupeds comprising the Horse, Ass, and Zebra, in which each foot has only a single solid hoof. Often called Solipedia. SOMATIC (Gr. soma, body). Connected with the body. SOMATOCYST (Gr. soma ; and kustis, a cyst). A peculiar cavity in the ccenosarc of the Calycophoridce (Hydrozoa). SOMITE (Gr. soma/. A single segment in the body of an Articulate animal. SPERMARIUM. The organ in which spermatozoa are produced. SPERM ATOPHORES (Gr. sperma, seed ; phero, I carry). The cylindrical cap-, sules of the Cephalopoda, which carry the spermatozoa ; sometimes called the " moving filaments of Needham." SPERMATOZOA (Gr. sperma, seed ; and zoon, animal). The microscopic fila- ments which form the essential generative element of the male. SPICULA (Lat. spiculum, a point). Pointed needle-shaped bodies. SPINNERETS. The organs by means of which Spiders and Caterpillars spin threads. SPIRACLKS (Lat. spiro, I breathe). The breathing-pores, or apertures of the breathing-tubes (tracheae) of Insects. Also the single nostril of the Hag- fishes, the " blow-hole " of Cetaceans, &c. SPLANCHNOSKELETON (Gr. splagchna, viscera ; skeletos, dry). The hard GLOSSARY. 599 structures occasionally developed in connection with the internal organs or viscera. SPONGE-PARTICLES. (See Sarcoids. ) SPONGIDA (Gr. spoygos, a sponge). The division of Protozoa commonly known as sponges. SPORES (Gr. spora, seed). Germs, usually of plants; in a restricted sense, the reproductive "gemmules" of certain Sponges. SPOROSACS (Gr. spora, seed; and sakkos, a bag). The simple generative buds of certain Hijdrozoa, in which the medusoid structure is not deve- loped. SQUAMATA (Lat. squama, a scale). The division of Reptiles comprising the Ophidia and Lacertilia in which the integument develops horny scales, but there are no dermal ossifications. STATOBLASTS (Gr. statos, stationary ; blastos, bud). Certain reproductive buds developed in the interior of Polyzoa, but not liberated until the death of the parent organism. STEGANOPHTHALMATA (Gr. steyanos, covered ; and orhthalmos, the eye). Applied by Edward Forbes to certain Medusae, in which the sense-organs ("marginal bodies") are protected by a sort of hood. The Steyanojth- thalmata are now separated from the true Medusidce, and placed in a sepa- rate division under the name Lucei'narida. STELLERIDA (Lat. stella, star). Sometimes employed to designate the order of the Star-fishes. STELLIFORM. Star-shaped. STEMMATA (Gr. stemma, garland). The simple eyes, or "ocelli," of certain animals, such as Insects, Spiders, and Crustacea. STERNUM (Gr. sternon). The breast-bone. STIGMATA. The breathing-pores in Insects and Arachnida. STOLON (Gr. stolos, a sending forth). Offshoots. — The connecting processes of sarcode, in Foraminifera ; the connecting tube in the social Ascidians; the processes sent out by the coenosarc of certain Actinozoa. STOMAPODA (Gr. stoma, mouth ; poos, foot). An order of Crustacea. STOMATODE (Gr. stoma). Possessing a mouth. The Infusoria are thus often called the Stomatode Protozoa. STREPSTPTERA (Gr strepho, I twist ; and pteron, wing). An order of Insects in which the anterior wings are represented by twisted rudiments. STREPSIRHINA (Gr. strepho, I twist ; rhiues, nostrils). A group of the Quadrumana, often spoken of as Prosimice. STROBILA (Gr. strobilos, a top, or fir-cone). The adult tapeworm with its generative segments or proglottides ; also applied to one of the stages in the life-history of the Lucernarida. STYLIFORM (Lat. stylus, a pointed instrument ; forma, form). Pointed in shape. SUB-CALCAREOUS. Somewhat calcareous. SUB-CENTRAL. Nearly central, but not quite. SUB-PEDUNCULATE. Supported upon a very short stem. SUB-SESSILE. Nearly sessile, or without a stalk. SUPINATION (Lat. supinm, lying with the face upwards). The act of turning the hand with the palm upwards. SUTURE (Lat. suo, I sew). The line of junction of two parts which are immovably connected together. Applied to the line where the whorls of a univalve shell join one another ; also to the lines made upon the exterior of the shell of a chambered Cephalopod by the margins of the septa. SWIMMERETS. The limbs of Crustacea, which are adapted for swimming. SYMPHYSIS (Gr. sumphusis, a growing together). Union of two bones in which there is no motion or but a very limited amount. SYNAPTICUL^: (Gr. sunapto, I fasten together). Transverse props sometimes found in Corals, extending across the loculi like the bars of a grate. SYSTOLE (Gr. sustello, I contract). Applied to the contraction of any con- tractile cavity, especially the heart. 6OO GLOSSARY. TABULA (Lat. tabula, a tablet). Horizontal plates or floors found in some Corals, extending across the cavity of the " theca," from side to side. TACTILE (Lat. tango, I touch). Connected with the sense of touch. T^ENIADA (Gr. tainia, a ribbon). The division of Scolecida comprising the Tapeworms. T.&NIOID (Gr. tainia; and eidos, form). Kibbon-shaped, like a tapeworm. TARSO-METATARSUS. The single bone in the leg of Birds produced by the union and anchylosis of the lower or distal portion of the tarsus with the whole of the metatarsus. TARSUS (Gr. tarsos, the flat of the foot). The small bones which form the ankle (or "instep" of man), and which correspond with the wrist (carpus) of the anterior limb. TECTIBRANCHIATA (Lat. tectus, covered ; and Gr. Iragchia, gills). A division of Opisthobranchiate Gasteropoda in which the gills are protected by the mantle. TEGUMENTARY (Lat. tegumentum, a covering). Connected with the integu- ment or skin. TELEOSTEI (Gr. teleios, perfect; osteon, bone). The order of the "Bony" Fishes. TELSON (Gr. telson, a limit). The last joint in the abdomen of Crustacea; variously regarded as a segment without appendages, or as an azygos appendage. TENUIROSTRES (Lat. tennis, slender; rostrum, beak). A group of the Perching Birds characterised by their slender beaks. TERGUM (Lat. for back). The dorsal arc of the somite of an Arthropod. TERRICOLA (Lat. terra, earth ; and colo, I inhabit). Employed occasionally to designate the Earth-worms (Lumbricidte). TEST (Lat. testa, shell). The shell of Mollusca, which are for this reason sometimes called "Testacea;" also, the calcareous case of Echinoderms; also, the thick leathery outer tunic in the Tunicata. TESTACEOUS. Provided with a shell or hard covering. TESTIS (Lat. testis, the testicle). The organ in the male animal which pro- duces the generative fluid or semen. TETRABRANCHIATA (Gr. tetra, four ; bragchia, gill). The order of Cephalopoda, characterised by the possession of four gills. THALASSICOLLIDA (Gr. thalassa, sea; kolla, glue). A division of Protozoa. THECA (Gr. theke, a sheath). A sheath or receptacle. THECOSOMATA (Gr. theke; and soma, body). A division of Pteropodous Molluscs, in which the bodv is protected by an external shell. THERIOMORPHA (Gr. iher, beast; morplie, shape). Applied by Owen to the order of the Tail-less Amphibians (Anoura.) THORAX (Gr. a breastplate). The chest. THREAD-CELLS. (See Cnidae.) THYSANURA (Gr. tkusanoi, fringes ; and oura, tail). An order of Apterous Insects. TIBIA (Lat. a flute). The shin-bone, being the innermost of the two bones of the leg, and corresponding with the radius in the anterior extremity. TOTIPALMAT^J (Lat. totus, whole; palma, the palm of the hand). A group of Wading Birds in which the hallux is united to the other toes by mem- brane, so that the feet are completely webbed. TRACHEA (Gr. tracJieia, the rough wind -pipe). The tube which conveys air to the lungs in the air-breathing Vertebrates. TRACHEAE. The breathing-tubes of Insects and other Articulate animals. TRACHEARIA. The division of Arachnida which breathe by means of tra- cheae. TREMATODA (Gr. trema, a pore). An order of Scolecida. TRICHOCYSTS (Gr. thrix, hair ; and kmtis, a cyst). Peculiar cells found in certain Infusoria, and very nearly identical with the "thread-cells" of Coelenterata. TRILOBITA (Gr. treis, three ; lobos, a lobe). An extinct order of Cmstaceans. TRITOZOOIDS (Gr. tritos, third ; zb'on, animal ; and eidos, form). The zob'id GLOSSARY. 60 1 produced by a deuterozooid ; that is to say, a zooid of the third genera- tion. TROCHAL (Gr. trochos, a wheel). Wheel-shaped ; applied to the ciliated disc of the Rotifera. TROCHANTER (Gr. trecho, I turn). A process of the upper part of the thigh- bone (femur) to which are attached the muscles which rotate the limb. There may be two, or even three, trochanters present. TROCHOID (Gr. trockos, a wheel ; and eidos, form). Conical with a flat base ; applied to the shells of Foraminifera and Univalve Molluscs. TROPHI (Gr. trophos, a nourisher). The parts of the mouth in insects which are concerned in the acquisition and preparation of food. Often called " instrumenta cibaria." TROPHOSOME (Gr. trepho, I nourish ; and soma, body). Applied collectively to the assemblage of the nutritive /obids of any Hydrozoon. TRUNCATED (Lat. trunco, I shorten). Abruptly cut off; applied to univalve shells, the apex of which breaks off, so that the shell becomes "decol- lated." TOBICOLA (Lat. tuba, a tube; and colo, I inhabit). The order of A nnelida which construct a tubular case in which they protect themselves. TUBICOLOUS. Inhabiting a tube. TUNICATA (Lat. tunica^ a cloak). A class of Molluscoida which are enveloped in a tough leathery case or " test." TURBELLARIA (Lat. turbo, I disturb). An order of Scolecida. TURBINATED (Lat. turbo, a top). Top-shaped ; conical, with a round base. ULNA (Gr. olene, the elbow). The outermost of the two bones of the fore- arm, corresponding with the fibula of the hind-limb. UMBELLATE (L»t. umbella, a parasol). Forming an umbel — i.e., a number of nearly equal radii all proceeding from one point. UMBILICUS (Lat. for navel). The aperture seen at the base of the axis of certain univalve shells, which are then said to be "perforated" or "um- bilicated." UMBO (Lat. the boss of a shield). The beak of a bivalve shell. UMBRELLA. The contractile disc of one of the Lucernarida. UNCINATE (Lat. uncinus, a hook). Provided with hooks or bent spines. UNGUICULATE (Lat. unguis, nail). Furnished with claws. UNGULATA (Lat. ungula, hoof). The order of Mammals comprising the Hoofed Quadrupeds. UNGULATE. Furnished with expanded nails constituting hoofs. UNILOCULAR (Lat. unus, one ; and loculus, a little purse). Possessing a single cavity or chamber. Applied to the shells of Foraminifera and Mollmca. UNIVALVE (Lat. unus, one ; valvce, folding doors). A shell composed of a single piece or valve. URODELA (Gr. oura, tail ; delos, visible). The order of the tailed Amphi- bians (Newts, &c. ) URTICATING CELLS (Lat. urtica, a nettle). (See Cnidae). VACUOLES (Lat. vacuns, empty). The little cavities formed in the interior of many of the Protozoa by the presence of little particles of food, usually surrounded by a little water. These are properly called "food-vacuoles," and were supposed to be stomachs by Ehrenberg. Also the clear spaces which are often seen in the tissues of many Ccelenterata. VARICES (Lat. varix, a dilated vein). The ridges or spinose lines which mark the former position of the mouth in certain univalve shells. VASCULAR (Lat. vas, a vessel). Connected with the circulatory system. VELUM (Lat. a sail). The membrane which surrounds and partially closes the mouth of the " disc" of Medusae, or medusiform gonophores. VENTRAL (Lat. venter, the stomach). Relating to the inferior surface of the body. VENTRICLE (Lat. dim. oftMfer, stomach). Applied to one of the cavities of the heart, which receives blood from the auricle. 602 GLOSSARY. VERMES (Lat. vermis, a worm). Sometimes employed at the present day in the same, or very nearly the same, sense as Annuloida, or as Anmdoida plus the A narthropoda. VERMIFORM (Lat. vermis, worm ; and forma, form). Worm-like. VERTEBRA (Lat. verto, I turn). One of the bony segments of the vertebral column or back-bone. VERTEBRATA. (Lat. vertebra, a bone of the back, from vertere, to turn). The division of the Animal Kingdom, roughly characterised by the possession of a back-bone. VESICLE (Lat. vesica, a bladder). A little sac or cyst. VIBRACULA (Lat. vibro, I shake). Long filamentous appendages found in many Polyzoa. VIBRIONES (Lat. vibro, I shake). The little moving filaments developed in organic infusions. VIPERINA (Lat. vipera, a viper). A group of the Snakes. VIVIPAROUS (Lat. vivus, alive; and pario, I bring forth). Bringing forth young alive. WHORL. The spiral turn of a univalve shell. XIPHISTERNUM (Gr. xipfios, sword ; sternon, breast-bone). The inferior or posterior segment of the sternum, corresponding with the " xiphoid carti- lage" of human anatomy. XIPHOSURA (Gr. xipfios, a sword ; and oura, tail). An order of Crustacea, comprising the Limuli or King-Crabs, characterised by their long sword- like tails. XYLOPHAGOUS (Gr. xulon, wood ; and pkago, I eat). Eating wood ; applied to certain Mollusca. Zoom (Gr. zoSn, animal ; and eidos, like). The more or less completely inde- pendent organisms, produced by gemmation or fission, whether these re- main attached to one another or are detached and set free. ZOOPHYTE (Gr. zodn, animal ; phuton, plant). Loosely applied to many plant- like animals, such as Sponges, Corals, Sea-anemones, Sea- mats, &c. ZOOSPORES (Gr. zob'n, animal ; and spora, seed). The ciliated locomotive germs of some of the lowest forms of plants (Protophyta). INDEX. AARDVABK, 502. Aardwolf, 538. Abdominalia (Cirripedia), 198 ; characters of, 2o3; (Fishes), 361. Abranchiata (Vertebrata), 337. Abyla, 91. Acalephce, 95, 99. Acanthocephala, 158, 165; characters of, 168, 169. Acanthometrina, 58. Acanthopteri, 3(53. Acanthopterygii, 358. Acanthospongia, 64. Acarida, 226. Acarina, 224 ; characters and families of, 225, 226. Accipitrince, 465, 466. Acephala (Molluscu), 278. Acerotherium, 565. Acervulina, 53. Acetabula, 299, 300. Achetina, 244. Achtheres, 199. Acicula, 297. Aciculidce, 294, 297. Acipenser, 378. ^4c/noea, 295. Acorn-Shells, 200, 201. Acrodus, 373. ^4cro. Hcematotherma, 338. Hag-fishes, 355, 356, 357. Haimeia, 120. Hair-worms, 169. Halcyornis, 469. Halicore, 503. Haliomma, 58. Haliotidce, 292, 295. Haliotis, 295. Halitherium, 564. Halteres, 235. Hamites, 314, 315. Hapale, 555. Hapalidce, 554. Harpa, 294. Haustellata, 198 (see Epizoa). Hawks, 465. Hectocotylus, 302, 305. Hedgehog, 550, 551. Helicidce, 294. Helicoidea, 54. Helicostega, 54. .ffefae, 296. Helladotherium, 524, 565, 569. Hemelytra, 235, 243. Hemicardium, 285. Hemimetabola (Insecta), 239, 241, 242. Hemiptera, 242, characters of, 243. Hermit-crab, 217. Heron, 449. Herpestes, 537. Heterocercal (tail of fishes), 348. Heterogeny, 35. Heteromastix, 72. Heterophagi, 439. Heteropoda, 291 ; characters of, 292 ; foot of, 293 ; shell of, 293 ; divisions of, 296 ; distribution of, in time, 313. Heteroptera, 243. Hipparion, 565. Hippobosca, 247. Hippocampidce, 364. Hippocrepian Polyzoa, 263. Hippohyus, 565. Hippopotamidce, 516, 565. Hippopotamus, 516, 565. Hippurites, 284. Hippuritidce, 284, 313. Hirudinea, 181 ; general characters of, 181, 182. Hirudo, 188. Hirundinidce, 463. Holocephali, 370 ; characters of, 371. Holocystis, 123, 132. Holometabola (Insecta), 239, 246. Holoptychius, 378. Holostomata (Gasteropoda), 290, 291, 294, 313. Holothuria, 153, 154. Holothuridoe, 155. Holothuroidea, 138 ; general characters of, 153-155; families of, 155 ; distribution of, in space, 155 ; in time, 158. Homocercal (tails of Fishes), 348. Homology, 16; serial, 16. Homomorphism, 16. Hortioptera, 243. Honey-eater, 462. Hoopoe, 462. Horn-bill, 460. Horse, 476, 478, 515. Humming-birds, 462, Hycena, 538, 568. Hycenidce, 538. Hyalea, 298, 313. Hyaleadce, 298. Hyalochostidce, 116. Hyalonemadce, 116, 123. Hybodut, 373. Hydatids, 161 163. Hydatina, 174. Hydra, 9, 25 ; structure of, 79 ; repro- duction of, 80, 81 ; thread-cells of, 76 ; development of, 81 ; distribution of, 107. Hydrachnidce, 226. Hydractinia, gonophores of, 82, 84. Hydra-tuba, 28, 29, 101, 102, 103. Hydrida, 79. Hydrocaulus, 86. Hydrochozrus, 543. Hydrocj;sts, 93. Hydroecium, 91. Hydroida, characters and divisions of, 78 ; reproduction of, 82-85 ; distinguished from Polyzoa, 258, 259. Hydroid Zoophytes (see Hydroida). Hydrophidce, 406. Hydrophyllia, 90, 92. Hydrorhiza, 79. Hydrosoma, 77. Hydrothecse, 81, 85, 86. Hydrozoa, 76 ; characters of, 76 ; termin- ology of, 77; divisions of, 78 ; reproduc- tion of, 82 ; Oceanic, 89 ; distribution of, in space and time, 107-109. Hyla, 382, 390. Hylobates, 557. Hymenocaria, 220. Hymenoptera, 249. Hyoid arch (Fishes), 344, 345. Hyopotamus, 565. Hyponome, 151. Hypostome, of Trilobites, 208. Hypsiprymnus, 493, 494. Hyracoidea, 487 ; general characters of, Hyrdx, 526, 527. Hystricidce, 543. Hystrix, 544. lanthina, 295. Ibis, 449. Ichneumon (Insecta), 235, 249. 612 INDEX. Ichthyodorulites, 361, 372, 379. Ichthyomorpha, 384. Ichthyophthira, 198, 199. Ichthyopsida, 338. Ichthyopterygia, 397; characters of, 416. Ichthyosauria, 416. Ichthyosaurus, 416, 417. Iguana, 408, 412. Iguanidce, 412. Iguanodon, 421, 422. Ilyanthidce, 113. Ilyanthus, 113. Imago, 239, 240. Imperforata (Foraminifera), 51, 54. Implacentalia (Mammalia), 484. Individuality, general definition of, 25, 77 ; in Sponges, 65. Infundibulum, of Cephalopoda, 299, 300. Infusoria, spontaneous generation of, 35, 36 ; characters of, 66 ; divisions of, 66 ; affinities of, 72 ; Ciliated, 66 ; Suctorial, 71 ; Flagellate, 71 ; compared with Eo- tifera, 176. Inia, 511. Innocua (Ophidia), 406. Inoceramus, 284. Inoperculata, 294, 296. Insecta, 191, 233 ; general characters of, 233-241 ; organs of the mouth of, 235 ; wings of, 234 ; digestive system of, 236 ; tracheae of, 238 ; circulation of, 237 ; metamorphoses of, 239; parthenogene- sis of, 30, 31 ; sexes of, 240 ; orders of, 241 ; distribution of, in time, 252. Insectivora, 484, 488; general characters of, 549; families of, 550; distribution of, in time, 568. Insessores, 443 ; characters of, 458 ; sec- tions of, 460. Integro-pallialia, 282, 283, 284. Invertebrata, general characters of, 324, 325. Ischiodus, 372, 380. Isis, 116, 122. Isocardia, 285. Isopoda, 198; characters of, 212; distri- bution of, in time, 220. lulus, 232. Ixodes, 226. JAGUAR, 541. Jelly-fishes, urticating powers of, 76 ; na- ture of, 97, 98 ; former classification of, 95, 96. Jerboa, 545. KANGAROO, 493. Kangaroo-rat, 493, 494. Kellia, 285. Keratode, 60. Keratosa (Sponges), 63. King-crabs, 209, 210, 222. Kinkajou, 535, 536. Koninckia, 274. Koninckiadce, 274. LABIUM, of Lobster, 197 ; of Arachnida, 222; of Insecta, 236. Labrum, of Lobster, 197 ; of Trilobita, 208 ; of Scorpion, 222 ; of Insecta, 235, 236. Labyrinthodontia, 391, 392. Lacerta, 411. Lacertidce, 411. Lacertilia, 387, 397 ; general characters of, 408, 409 ; families of, 409-413 ; distribu- tion of, in time, 413. Lcemodipoda, 198; characters of, 211, 212. Lagena, 52. Lagopus, 454. Lamellibranchiata, 253, 254 ; general characters of, 278-283; shell of, 279; digestive system of, 280; circulatory system of, 281 ; mantle of, 280 ; bran- chiae of, 281 ; reproduction of, 282 ; muscles of, 282; habits of, 283; divi- sions of, 283 ; families of, 284, 285 ; dis- tribution of, in time, 312. Lamellirostres, 446. Lamprey, 350, 355, 356, 357. Lamp-shells, 271. Lancelet, 334, 336, 341 ; anatomy of, 353- 355. Land-salamanders, 387. Laniidce, 461. Laomedea, 88. Laridce, 445. Lark, 460, 461. Larva, of Echinodermata, 136, 137; of Echinoidea, 138 ; of Asteroidea, 146 ; of Ophiuroidea, 147 ; of Crinoidea, 149 ; of Holothuroidea, 153 ; of Tceniada, 161, 162,163; ofTrematoda,164; ofNemer- tida, 167 ; of Acanthocephala, 168 ; of Ichthyophthira, 199; of Cirripedia, 201 ; of Brachyura, 217 ; of Limulus, 211; of Myriapoda, 231 ; of Insecta, 239, 240 ; of Tunicata, 269 ; of Brachiopoda, 273 ; of Lamellibranchiata, 282; of Gastero- poda, 289. Leech, 181. Lemuridce, 553. Leopard, 541. Lepadidce, 198, 200 ; characters of, 202 ; distribution of, in time, 220. Lepas, 201. Lepidoganoidei, 367, 378. Lepidoptera, 247 ; mouth of, 236 ; charac- ters of, 247. Lepidosiren, 351,352,356; characters of, 375-377. Lepidosteus, 342, 365, 367. Lepidota, 384 (see Dipnoi). Lepisma, 242. Leporidce, 543. Leptcena, 274. Leptocardia, 353 (see Pharyngobranchii). Lepus, 543. Lernoea, 34, 199. Libellulidee, 244. Lieberkuhnla, 50. Ligula, 236. Limacidce, 294, 296. Limacina, 298. Limacinidce, 298. Limax, 256, 296. Limnadia, 207. Limncea, 296, 313. Limnceidce, 294, 296. Limnoria, 213. Limulus, 209, 210, 211, 220. Lingua (Insects), 236. Lingual Ribbon (Mollusca), 287. Linguatulina, 225. INDEX. Lingula, 271, 275, 276, 277. Lingulidce, 274, 275. Lion, 531, 539, 540. Lissencephala, 484. Lithobius, 232. Lithocysts, 99, 104. Lithodomi, 283. Lithornis, 469. i Littorina, 291, 295. Littorinidce, 292, 295. Lituites, 310, 312. Lituolida, 54. Liver-fluke, 165. Lizards, 408-411. Llama, 520, 521. Lobster, morphology of, 193-198 ; general anatomy of, 214-217. Lob-worm, 187, 189. Loculi, of shell of Foraminifera, 50 ; of Corals, 115. Locustina, 244. Loligo, 306, 311. Longipennatce, 445. Longirostres, 448, 450. Lophiidce, 363. Lophobranchii, 363. Lophopea, 265. Lophopore, 263, 2(55. Lophopus, 261, 262. Lophyropoda, 204. Loricata, 395. Love-bird, 458. Loxiadce, 460, 461. Lucernaria, 100. Lucernariadce, 99, 100. Lucernarida, 78; general characters of, 99; umbrella of, 99; divisions of, 99; development of, 101 ; structure of re- productive zooids of, 103, 104. Lucina, 285. Lucinidoe, 284, 285. Luidia, 145. Lumbricidce, 182. Lumbricus, 183. Zwtra, 537. Lutraria, 285. Lyencephala, 484. Lynx, 541. MACACUS, 556. Maccaw, 458. Macellodon, 413. Machairodus, 567. Maclurea, 296, 313. Macrauchenia, 569. Macrobiotidce, 225. Macrodactyli, 448. Macropodidce, 493. Macrospondylus, 415. Macrotherium, 564. Macrura, 214; characters of, 214-217. Mactra, 285. Mactridce, 284, 285. Madreporidce, 134. Madreporiform tubercle of Echinodermata, 137; of Echinoidea, 139 ; of Asteroidea, 145 ; of Ophiuroidea, 147 ; of Holothur- oidea, 154. Malacodermata (Zoantharia), 111, 129. Malacopteri, 360. Malacopterygii, 358. Malacostraca, 198; characters of, 211. Mallophaga, 242. Malpighian tubes, of Insects, 237. Mammalia, 337, 338; general characters of, 471-483 ; osteology of, 472-480 ; teeth of, 479, 480 ; digestive system of, 481 ; circulatory system of, 481 ; respiratory system of, 481 ; nervous system of, 482; reproductive system of, 482; integu- mentary system of, 483 ; primary di- visions of, 484, 485 ; orders of, 484-486 ; distribution of, in time, 559-570. Mammoth, 528, 529, 567. Manatee, 472, 502, 503. Manatidte, 503. Manatus, 503. Mandibles, of Lobster, 196; of Arachnida, 222; of Myriapoda, 232 ; of Insecta, 235, 236 ; of Cephalopoda, 300, 308; of Verte- brates, 330. Manidce, 501. Jfanis, 479, 483, 498, 501. Mantle, of Tunicata, 266 ; of Brachiopoda, 272 ; of Lamellibranchiata, 280 ; of Gas- teropoda, 287 ; of Cephalopoda, 299 ; of Nautilus, 308. Manubrium, 82, 96. Marginal bodies, of Medusae, 96 ; of Z,«- cernarida, 99, 104. Marginella, 294. Marmoset, 554. Marmot, 546. Marsipobranchii, general characters of, 355-357; families of, 355; distribution of, in time, 378. Marsupial bones, 477, 489, 492. Marsupialia, 484, 485, 486 ; general char- acters of, 491 ; families of, 492-497 ; dis- tribution of, in space, 491 ; in time, 560. Marsupites, 156. Mastax, 173. Mastodon, 527, 529, 566. Maxillae, of Lobster, 196; of Arachnida, 222 ; of Insecta, 236. Maxillipedes, of Lobster, 196 ; of Centi- pedes, 232. May-flies, 244. Meandrina, 119. Measles, of Pig, 163 ; of Ox, 163. Medusidce, 95-99 ; structure of, 96 ; exact nature of, 97, 98. Megaceros, 523, 565. Megaderma, 549. Megalonyx, 563, 569. Megalosaurus, 421. Megalotrocha, 173. Megaptera, 508. Megatherium, 563, 569. Melania, 295. Melaniadce, 292, 295. Meleagris, 454. Meleagrince, 454. Meles, 536. Melicerta, 173, 174, 175. Melidce, 536. Meliphagidce, 462. Mellivora, 536. Membrana nictitans (of Birds), 439; of Mammals, 483. Menobranchus, 385, 386. Menopoma, 385, 386, 392. Mentum, 236. Mephitis, 537. 614 INDEX. Mergulus, 445. Meropidce, 463. Merostomata, 198 ; characters and divi- sions of, 209; distribution of, in time, 220. Merulidce, 461, 462. Merycotherium, 569. Mesenteries (of Actinozoa), 110, 112, 113, 115, 127. Mesopodinm, 287, 293. Mesothorax, 234. Metamorphosis, 33 ; of Myriapoda, 231 ; of Insecta, 239 ; incomplete, 239 ; com- plete, 240. Metapodium, 287, 293, 297. Metasoma, 299, 307. Metastoma, of Lobster, 216 ; of Euryp- terida, 210, 211. Metathorax, 234. Microconchus, 188. Microlestes, 559, 560. Miliola, 51. Miliolida, 54. Milleporidce, 134. Millipedes, 230, 232. Mites, 221. Mitra, 294. Modeeria, 97. Modiola, 284. Mole, 474, 477, 483, 550. Mollusca, 14 ; general characters of, 253- 257; digestive system of, 253; circula- tory system of, 254; respiratory organs of, 254 ; nervous system of, 255 ; sense- organs of, 255 ; reproduction of, 255 ; shell of, 255-257 ; divisions of, 257 ; dis- tribution of, in time, 275, 312. Mollusca Proper, 257; characters of, 278; divisions of, 278 ; distribution of, in time, 312. Molluscoida, 257 ; characters and divisions of, 258 ; distribution of, in space, 275 ; in time, 276. Monads, 35, 36. Monitor, 411. Monkeys, 475, 476, 482, 483. Monodelpkia, 485. Monodon, 511. Monomerosomata, 224, 225. Monomyaria, 283. Monostega, 54. Monothalamia, 52. Monotremata, 473, 474, 482, 484, 485, 486; general characters of, 489 ; distribution of, in space, 490 ; in time, 560. Mopsea, 133. Morphology, 11. Morse, 533. Mosasaurus, 413. Moschidce, 520, 522. Moschus, 522. Motacillince, 462. Mother-of-pearl, 256. Moths, 247. Mud-fish, 375. Mugilidce, 363. Mulleria, 284. Multivalve shells, 256, 286, 290. Murchisonia, 295. Murex, 294. Muricidce, 291, 294. Muridce, 544, 545. Mus, 545. Musca, 247. Musticapidce, 461. Musk-deer, 520, 522. Musk-ox, 526. Mustela, 536. Mustelidce, 536. Mutilata, 503. Mya, 283, 285. Myacidce, 284, 285. Mycetes, 555. Mylodon, 563, 569. Myochama, 285. My odes, 545. Myopotamus, 543. Myoxidce, 545. Myoxus, 545. Myriapoda, 191; general characters of, 230 ; development of, 231 ; distribution of, in time, 232. Myrmecobius, 495, 496. Myrmecophaga, 479, 501. Myrmecophagidce, 501. Myrmeleo, 244. Mytilidce, 283, 284. Mytilus, 284. Myxine, 356, 357. Myxinidce, 355. Myxinoids, 352, 350. NACREOUS shells, 256. Naididce, 182, 183. Nais, 183, 188. Naja, 406. Narwhal, 510, 511. Nassa, 294. Nasua, 535, 536. Natatores, 442; general characters of, 443, 444. Nathetes, 413. Natica, 294. Naticidce, 292, 294. Nautilidce, characters of, 309 ; sections of, 312; distribution of, in time, 314. Nautiloid shells (of Foraminifera), 53, 54. Nautilus, Paper, 299; shell of, 303; Pearly, 299 ; anatomy of, 307'; shell of, 304. Nebalia, 220. Nectocalyces, 89; structure of, 90; in Calycophoridce, 90 ; in Medusidce, 96 ; distinguished from the umbrella of Lucernarida, 99. Nectosac, 90. Needham, moving filaments of, 302. Nematelmia, 158 ; characters of, 168. Nematocysts, 76. Nematoda, 158, 168; characters of, 169 ; parasitic forms of, 169-171; free forms of, 171. Nematophores, 87. Nemertes, 167. Nemertida, 159 ; characters of, 167 ; de- velopment of, 167. Nereidce, 188. Nereidea, 185. Nereis, 189. Nerita, 295. Neritina, 295. Neritidce, 292, 295. Nervures, 234. Neuropodium, 179. INDEX. 6lS Neuroptera, 244, 252. Newts, 386, 387. Nidamental ribbon, 255. Noctiluca, 72. Nodosaria, 52, 53. Nothosaurus, 418. Notidanus, 380. Notochord, 323, 325. Notommatina, 175. Notonecta, 243. Notopodium, 179. Notornis, 449. Nucleobranchiata, 291 (see Heteropoda). Nucleolus of Paramcecium, 67. Nucleus of Protozoa, 42 ; of Amoeba, 47, 48 ; of Gregarina, 44 ; of Paramcecium, 67 ; of Vorticella, 69 ; of Echinoder- mata, 145 (see Madrepori/orm tubercle) ; of the shell of Mollusca, 256, 289. Nudibranchiata, 256, 288 ; characters of, 292 ; divisions of, 296. Numenius, 450. Numida, 454. Nummulites, 53, 56, 57. Nummulitic Limestone, 57. Sycticebidce, 553. Nymph, 239. Nymphon, 225. Oboto, 275. Oceanic Hydrozoa, 89 ; divisions of, 89 ; distribution of, in space, 108. Ocelli, of Medttsce, 97; of Echinoidea, 139; of Asteroidea, 146; of Planarida, 167 ; of Rotifera, 175 ; of Annelida, ISO ; of Chcetognatha, 189 ; of Limulus, 209; of Arachnida, 224; of M yriapoda, 231 ; of Insecta, 238 ; of Tunicata, 255, 268 ; of Lamellibranchiata, 255. Octopoda, 305, 811. Octopodidce, 305. Octopus, 302, 303, 311. Oculinidce, 134. Odontaspis, 380. Odontoceti, 505, 509. Odontophora, 278, 286. Odontophore, 287. Oedicnemus, 450. Oldhamia, 108, 276. Oligochceta, 182, 188. Ommastrephes, 311. Omnivora (Ungulata), 516. Onchuna, 199. Onchus, 379. Oncidiadce, 294, 296. Oncidium, 296. Oniscus, 213. Onychoteuthis, 300, 311. 1 Operculata, 294, 296. Operculum, of Balanidce, 202 ; of Gaster- opoda, 287 ; of Heteropoda, 293 ; of Pteropoda, 297 ; of Fishes, 344, 349. Ophidia, 397 ; general characters of, 402- 405 ; divisions of, 405 ; distribution of, in time, 407. Ophidobatrachia, 384. Ophwcoma, 157. Ophioderma, 157. Ophiolepis, 147. Ophiomorpha, 384. Ophiura, 147, 148. Ophiuridea, 148. Ophiuroidea, 137, 138 ; general characters of, 146 ; families of, 148 ; distribution of, in space, 155 ; in time, 157. Opisthobranchiata, 291, 292, 296. Opisthocoelia (Crocodilia), 415. Opossum, 495, 496. Orang-outang, 557. Orbitoides, 57. Orbitolites, 53. Oreaster, 157 Organ of Bojanus, 273, 282. Organ-pipe Coral, 120. Organs of the mouth of Insects, 235, 236. Ornithodelphia, 485, 489. Ornithorhynchus, 479, 482, 485, 489, 490. OrMis, 274. Orthisina, 274. Orthoceras, 310, 211, 312, 314. Orthoceratidce, 312, 314. Orthoptera, 242, 243, 244. Orycteropidce, 501. Orycteropus, 498, 501. Oscula, of Sponges, 60, 61 ; of Tape-worm, 161. OsteoUpis, 367, 378. Ostraciontidce, 363. Ostracoda, 198; characters of, 205; dis- tribution of, in time, 220. Ostracostei, 368. Osfrea, 283, 284. Ostreidce, 283, 284. Ostrich, 451, 452. Otaria, 533. O«i(to, 450. Otter, 537. Oudenodon, 419. Ovarian vesicles, of Sertularida, 87. Ofli&os, 526. O^idce, 524, 525. Ovipositor, 235, 249. O»is, 525. Ovulum, 294. Owls, 464, 465. Oxen, 518, 520, 525. Oxyuris, 170. Pachydermata, 511, 512. Paddle-fish, 368. Pcecilopoda, 209 (see Xiphosura). Paguridce, 217. Palceaster, 157. Palcechimis, 157. Palceocoryne, 108. Palceodiscus, 157. Palceophis, 407. Palceospongia, 64. Palceotherium, 515, 564. Palapteryx, 470. Pali (Corals), 115. Pallial line, 280, 281. Pallia! sinus, 282. Palliobranchiata, 270. Pallium (see Mantle). Paludicella, 263. Paludicellea, 265. Paludina, 295, 313. Paludinidce, 292, 295. Paludomus, 295. Palythoa, 117. Pamphagus, 49. Pangolin, 501. 6i6 INDEX. Panopea, 285. Panspermy, 35. Pantopoda, 225. Paper Nautilus, 299, 303, 305. Papio, 556. Paradiseidce, 460. Paramoecium, 66; structure of, 66, 67; reproduction of, 67. Parapodia, 179. Parince, 462. Parmacella, 296. Parmophorua, 295. Parra, 458. Parrakeets, 458. Parrots, 457. Parthenogenesis, 30-32; of Ostracode Crustaceans, 205 ; of Insects, 30-32, 250. Passerine Birds (Pa-sseres), 458. Patagium, 420, 488, 546. Patella, 289, 295. Patellidce, 292, 295. Pavo, 455. Pavonince, 454. Peachia, 112, 127. Pearly Nautilus, 299, 300, 303, 304, 307. Peccary, 517, 569. Pecten, 283, 284. Pectunculus, 284. Pedicellariae, 140. Pedicellina, 263. Pedicellinea, 265. Pediculus, 242. Pedipalpi, 227. Pelagia, 100, 101, 105. Pelagidce, 100, 101 ; structure of genera- tive zooids of, 103. PeUas, 405. Pelicanidce, 446. Pelonaia, 256. Pen, of Cuttle-fishes, 303. Penguin, 444. Peniculus, 199. Pennatula, 121. Pennatulidce, 120, 122, 123 ; distribution of, in time, 133. Pentacerotidce, 146. Pentacrinus, 149, 150. Pentamerus, 274. Pentastomida, 225. Pentatoma, 243. Pentremites, 153, 156. Perameles, 495. Perchers, 458. Percidce, 363. Perdix, 454. Perennibranchiata (Amphibia), 381, 382, 383. Perforata(Foraminiferd),51, 54 ; (Corals), 118. Pericardium, of Crustacea, 191, 197 ; of Nautilus, 309. Periderm, 87. Peridinium, 72. Perigastric space, ofPotyzoa, 263. Periostracum, 257. Perisehoechinidce, 157, Perissodactyla, 513. Peristome, of Vorticella, 68 ; of the shell of Gasteropoda, 290. Peristomial space of Actinia, 112. Peritoneum (Tunicata), 267. Perivisceral space,of J.ciinozoa, 110. Petaurus, 495. Petraster, 157. Petromyzon, 357. Petromyzonidce, 355. Petrospongiadce, 64. Pezophaps, 456, 470. Pezoporince, 458. Phacochcerus. 517. Phcenicopteridce, 447. Phcenicopterus, 447. Phalacrocorax, 446. Phalangers, 494, 495. Phalangidce, 227. Phalangistidce, 495, Pharyngobranchii, 353-355. Pharyngognathi, 363. Pharynx of Ascidians, 267, 268, 269; of Lancelet, 354. Phascolarctos, 494. Phascolomys, 492. Phascolotherium, 560, 561. Phasianidce, 454. Phasianus, 454. Pheasant, 454. Philine, 296. Phillipsia, 220. Pftoca, 533. Phoccena, 510. Phocidce, 532. Pholadidce, 256, 286. Pholadomya, 285. Pholas, 283, 286. Phorus, 295. Phosphorescence of the Sea, 72. Phragmacone, 256 ; of Spirula, 313, 306 ; of Belemnite, 307. Phragmoceras, 312. Phryganeidce, 244. Phylactolcemata, 265. Phyllidia, 296. Phyllidiadte, 292, 296. Phyllirrhoe, 296. Phyllirrhoidce, 292, 296. Phyllocyst, 90. Phyllopoda, 198; characters of, 207; dis- tribution of, in time, 220. Phyllostoma, 549. Phyllostomidce, 548, 549. Phyogemmaria, 94. P/a/sa, 296. Physalia, 76, 93. Physaliadce, 94. Physeter, 509. Physeteridce, 509. Physiology, 12. Physophora, 93. Physophoridce, 89 ; characters of, 92, 93 ; tentacles of, 93 ; reproduction of, 93 ; distribution of, in space, 108. Physostomata, 360. Picidce, 457. Pigeons, 455. Pigment-spot, of Ii\fusoria, 71 ; of /era, 175. Pileolus, 295. Pileopsis, 295. Pilidium, 167. Pinna, 283, 284. Pinnigrada, 531. Pinnipedia, 531. Pinnoctopus, 311. Pipe-fish, 364. INDEX. 6I7 Pipidce, 390. Pisces, 337, 338; general characters of, 340 ; scales of, 340 ; skeleton of, 341- 345; limbs of, 345; tail of, 348; diges- tive system of, 351 ; respiratory system of, 349 ; heart of, 350 ; swim-bladder of, 351 ; nervous system of, 352 ; repro- ductive system of, 352 ; orders of, 353- 377 ; distribution of, in time, 377-380. Placenta, 472, 484. Placentalia (Mammalia), 484. Placodus, 419. Placoganoidei, 367, 368, 378. Placoid (scales of Fishes), 341, 370. Placoidei, 370. Plagiaulax, 560, 562. Plagiostomi, 370, 371 ; characters of, 372- 374. Planarida, 166, 167, 176. Planorbis, 289, 296. Plantigrada, 531, 534. Planula, 101. Plastron, 398, 399. Plataleadce, 450. Platanista, 511. Platyelmia, 158, characters of, 159. Platyrhina, 552, 554. Plecotus, 548. Plectognathi, 363. Pleswsauria, 417. Plesiosaurus, 418. Pleura, of Lobster, 194 ; of Trilobite, 209. Pleur acanthus, 380. Pleurobrachia, 124; ctenophores of, 125; canal system of, 125, 126 ; development of, 127 ; homologies of, 127. Pleurobrachiadce, 128. Pleurobranchiadoe, 292, 296. Pleurobranchus, 296. Pleuronectidce, 362, 373. Pleuronema, 72. Pleurotoma, 294. Pleurotomaria, 295. Ptiolophus, 564. Pliopithccus, 568. Plotus, 446. Plough-share bone, 427. Plumaster, 157. Plurnularia, 87.' Pluteus, 137, 138. Pneumatic filaments of Physophoridce, 93. Pneumatocyst, 92. Pneumatophore, 92, 93, 94. Pneumodermon, 298. Podophthalmata, 198; characters of, 213. Podosomata, 225. Podura, 235, 242. Polyarthra, 175. Pblycoelia, 133. Polycystina, 58, 59. Polydesmus, 232. Polygastrica (of Ehrenberg), 67. Polynoe, 186. Polypary, 77, 81. Polype, 110. Polypide, 259, 260. Polypidom, 77. Polypite, 77. Polypterus, 367. Polystome Infusoria, 71. Polythalamia (Foraminifera), 52. Polytrema, 56. Polyxenia, 97 Polyzoa, 253, 254, 255 ; characters of, 258- 265 ; distinctions from Hydrozoa, 258, 259 ; typical polypide of, 260 ; avicularia of, 261 ; lophophore of, 263 ; nervous system of, 263 ; digestive system of, 263 ; reproduction of, 264; statoblasts of, 264 ; development of, 265 ; relations to Tunicata, 269 ; divisions of, 265 ; orders of, 265 ; distribution of, in space, 275; in time, 276. Polyzoarium, 258, 259. Pontobdella, 188. Porambonites, 274. Porcellanous shells, 256, Porcellia, 313. Porcupine, 544. Pores of Sponges, 60, 61. Parties, 132. Poritidce, 134. Porpoise, 505, 510. Portuguese man-of-war, 76, 89, 93. Potamides, 295. Poulpe, 302, 305. Praya, 91. Prayidce, 92. Pressirostres, 448, 450. Prestwichia, 220. Priapulacea, 179. Pristis, 374. Proboscidea, 484, 487 ; characters of, 527; distribution of, in time, 566, 567. Proboscis, of Medusae, 96 ; of Crinoidea, 149; of Planarida, 167; of Acantho- cephala, 168 ; of Gephyrea, 178 ; of Errantia, 186 ; of Lepidoptera, 236 ; of Proboscidea, 527. Procellaridce, 445. Proccelia (CrocodUia), 414, 415. Procyon, 535. Producta, 275. Production, 275, 276. Proglottis, 160. Pro-legs, 249. Promeropidce, 462. Pro-ostracum, 306, 307. Propodite, 196. Propodium, 287, 293. Proscolex, 161, 162. Prosimice, 553. Prosobranchiata, 291: divisions of, 291, 294. Prosoma, 299, 307. Prosoponiscus, 220. Prostomium, of Planarida, 167 ; of An- nelides, 180. Protaster, 157. Proteles, 538. Proteolepas, 204. Proteus, 336, 385, 390. Proteus-animalcule, 47. Prothorax, 234. Protoplasm, 4. Protopodite, 196. Protopteri, 375 (see Dipnoi). Protornis, 469. Protovirgularia, 133. Protozoa, 14 ; general characters of, 42, 43 ; classification of, 43, 44. Proventriculus, of Earthworms, 183 ; of Birds, 434. Proximal, 77. 6i8 INDEX. Psammobia, 285. Pseuderabryo, 138. Pseudobranchia, 366. Pseudohsemal system, ISO. Pseudo-hearts, 273. Pseudonavicellse, 45. Pseudopodia, 43, 46, 48. Pseudoscorpionidce, 227. Psittacidce, 457, Psolus, 158. Psorospermice, 46. Ptarmigan, 454. Pteraspis, 369, 378. Pterichthys, 368, 378. Pteroceras, 294. Pterodactyles, 419, 420. Pteromys, 546. Pteropidce, 549. Pteropoda, 253, 286; general characters of, 297, 298; foot of, 297; shell of, 297; di- visions of, 298 ; distribution of, in space, 298; in time, 313. Pteropus, 549. Plerosauria, 397; general characters of, 419 ; distribution of, in time, 420. Pterygotus, 210, 211. Ptilodictya, 276. Ptilograpsus, 106. Ptilopora, 276. Ptychoeeras, 310, 315. Pulicidce, 246. Pulmogasteropoda, 288, 290. Pulmonaria (Arachmda), 224, 227. Pulmonifera (Moliusca), 290, 293, 296. Puma, 541. Pupa, 239, 240. Pupa, 296, 313. Pupina, 297. Purples, of Wheat, 172. Purpura, 294. Pycnogonum, 225. Pygidium, 208. Pyramidella, 295. Pyramidellidce, 292, 295. Pyrosomidce, 270. Pyrula, 294. Python, 402, 406. QUADRATE Bone, 330, 402, 404. Quadrumana, 475, 476; 478, 484, 488; characters of, 552 ; sections of, 552 ; dis- tribution of, in time, 568. Quagga, 515. RABBIT, 542, 543. Racoon, 535. Radiata, 74. Radiolaria, 57; characters of, 58. Radiolites, 284. Raia, 374. Rallidce, 448. Rallus, 449. Ramphorhynchus, 419, 421. .Rtma, 390. Ranidce, 390. Raptores, 443 ; characters of, 464 ; sections of, 468. Rasores, 443 ; characters of, 453 ; sections of, 453. Rastrites, 106. Rat, 545. Ratel, 536. Ratitce, 442. Rays, 370, 373, 374, 380. Red Coral, 122, 129. Regnum Protisticum, 7. Rein-deer, 522, 523, 565. Reproduction, general phenomena of,23-33; sexual, 23 ; non-sexual, 24-33. Reptilia, 337, 393 ; general characters of, 393-397; jaw of, 394; teeth of, 395; cir- culation of, 396; respiration of, 397; orders of, 397. Respiratory tree, of Holothurians, 154. Respiratory tubes, of Rotifera, 174. Reticulosa, 51, 53 (see Foraminifera). Retiolites, 106. Reversed shells, 257. Rhabdocoela, 167. Rhabdoidea, 54. Rhabdopleura, 106, 263. Rhamphastidce, 457, 458. Rhea, 452. Rhinoceridce, 513, 565. Rhinoceros, 512, 513, 514, 565. Rhinolophidce, 548. Rhinolophus, 549. Rhizocrinus, 150, 155. Rhizophysiadce, 95. Rhizopoda, 44 ; characters of, 46 ; pseudo- podia of, 46; divisions of, 47. Rhizostoma, 104, 105. Rhizostomidce, 99 ; definition of, 101 ; de- velopment of, 101-103; structure of re- productive zooids of, 104, 105. Rhynchonelli, 274, 277. Rhynchonellidce, 272, 274. Rhynchosaurus, 419. Rhynchota (see Hemiptera). Rhytina, 479, 503, 504. Ribbon-worms, 167. Rissoa, 295. Rodentia, 475, 484, 487 ; general characters • of, 541 ; families of, 543 ; distribution of, in time, 568. Rorqual, 508. Rot, of Sheep, 165. Rotalina, 53. Rotatoria, 172 (see Rotifera). Rotifera, 135, 158; general characters of, 172 ; wheel-organ of, 173 ; water-vascular system of, 174; masticatory organs of, 173 ; affinities of, 176; vitality of, 5 ; dis- tinctions from Infusoria, 176. Round Worms, 169. Rugosa, 111, 124 ; characters of, 123 ; dis- tribution of, in time, 132; families of, 134. Ruminantia, 511, 512; characters of, 517; dentition of, 519; stomach of, 518; fa- milies of, 520 ; distribution of, in time, 565. Rupicapra, 525. Sabella, 184, 188. , , Sagitta, 189. Salamanders, 386, 387, 892. Salamandra, 387, 390. Salmonidce, 361. Salpa, 269. Salpidce, 270. Sand-pipers, 450. Sand-worms, 181, 185. Sanguisuga, 181, 182. Sarcode, 42; characters of, .43. INDEX. 619 Sarcoids, of Sponges, 61, 64. Sarcoptes, 226. Sarcnrhampus, 466. Sarsia, 28, 98. Sauria, 409. Saurillus, 413. Saurobatrachia, 384 (see Urodela). Sauropsida, 338, 393. Sauropterygia, 416; general characters of, 417 ; distribution of, in time, 418. Saururce, 441, 443 ; characters of, 467 ; distribution of, in time, 469. Saw-fish, 374. Saxicava, 286. Scalaria, 295. Scalpellum, 203. Scansores, 443 ; characters of, 457 ; fami- lies of, 457. Scaphites, 312, 314. Scaphognathite, 196. Scincidce, 410. Scincus, 411. Scissurella, 295. Sciuridce, 545. Sciurus, 545. Sclerenchyma, 115. Sclerobasica (Zoantharia), 113 ; divisions of, 116. Sclerobasic, corallum, 114, 115, 116. Sclerodermata (Zoantharia}, 117 ; divi- sions of, 118. Scleroclermic, corallum, 114, 115, 116, 117. Sclerogenidce, 363. Scolecida, 135 ; characters and divisions of, 158. Scolex, 161, 162. Scolites, 188. Scolopacidoe, 450. Scolopendra, 232. Scomberidce, 363. Scorpion-, 221, 222. Scorpionidce, 227; characters of, 227; dis- tribution of, in time, 230. Scyllcea, 296. Scyllaridce, 193. Scythrops, 457. Sea-anemones, 111, 129. Sea-cucumbers, 153. Seals, 531, 532. Sea-mouse, 186, 189. Sea- slugs, 292. Sea-spiders, 225. Sea-squirts, 8. Sea-worms, 177, 181, 185. Segmental organs, of Leeches, 182 ; of earth-worm, 183 ; of Errant Annelides, 186. Selaohii, 370 ; characters of, 373. Semnopithecus, 556. Sepia, 307, 312. Sepiadce, 306, 312, 315. Sepiostaire, 303, 306. Septa, of Corals, 115; of the shell of Tet- rabranchiate Cephalopods, 309, 310. Seriatoporidce, 134. Serpuia, 184, 185, 188. Sertularida, 79 ; characters of , 86 ; hydro- thecse of, 86 ; polypites of, 87 ; reproduc- tion of, 87; development of, 87 ; distri- bution of, in space and time, 107, 108. Setae, of Annelides, 179, 183, 184, 186. Sharks, 350, 370, 373, 380. Sheat-fishes, 361. Sheep, 518, 520, 525. Shell, of Brachiopoda, 271 ; of Lamelli- branchiata, 279 ; of Gasteropoda, 289 ; of Heteropoda, 293 ; of Pteropoda, 297 ; of Argonauta, 304 ; of Nautilus, 304 ; of Tetrabranchiate Cephalopods, 309. Shrew-mice, 550. Shrikes, 462. Siamang, 557. Sigaretm, 294. Suicea (Sponges), 63. Siluridce, 361. Simla, 557. iSVmoMwuf. 418. Sinupallialia, 284, 285. Siphonia, 65. Siphonida, 283, 284. Siphonophora, 78; characters of, 89; di- visions of, 89. Siphonostomata (Gasteropoda), 290, 291, 294, 313. Siphonotreta, 275. Siphons, of Lamellibranchiata, 281 ; of Gasteropoda, 288. Siphuncle, of the shell of Nautilus, 307, 308, 309; of Belemnites, 307 ; of Tetra- branchiata, 309 ; of Nautilidce, 309 ; of Ammonitidce. 310 ; of Orthoceras, 311. Sipunculacea, 179. Sipunculoidea,'lT7. Sipunculus, 178. Siredon, 385, 386. Siren, 385, 395, Sirenia, 472, 473, 477, 484, 486 ; charac- ters of, 502 ; distribution of, in time, 564. Sirenidce, 385. Sitta, 462. Sivatherium, 524, 565, 569. Slimonia, 220. Sloth, 472, 486, 498, 499. Snakes, 397, 402, 403, 404, 405, 407. Solarium, 295. Solaster, 146. Solecurtus, 285. Solen, 285. Solenidce, 284, 285. Solidungula, 511, 512, 515, 565. Solipedia (see Solidungula). Solitaire, 456. Solpugidce, 227. Somatic cavity, of Ccelenterata, 74, 75 ; of Hydrozoa, 76; of Hydra, 80; of Actin- ozoa, 109. Somatocyst, 89. Somite, 190; of Crustacea, 194; of Arach- nida, 221. Sorex, 550. Soricidce, 550. Soroidea, 54. Sparsispongia, 64. Spatangidce, 144. Spatularia, 368. Species, definition of, 19 ; origin of, 37-39. Spermatophores, 302. Sperm-whale, 505, 509. Sphceroma, 213. Sphceronectidce, 92. vrozoum, 59. 'lagodus, 379. ' 401. Spheniscidce. 444. 620 INDEX. Spicula, of Sponges, 60, 63 ; of Radiolaria, 58, 60; ofActinozoa, 115, 121. Spider-monkey, 555. Spiders, 228, 229, 230. Spinax, 371. Spiniferites, 65. Spinnerets of Spiders, 229; of Caterpillars, 248. ilis, 298. ?r, 274. ririferidce, 274, 276. nriferina, 274. Spirorbis, 185, 188. Spirula, 303, 306, 312. Spirulidce, 306. Spirulirostra, 312. Splanchnoskeleton, 303. Spondylus, 284. Spongida, 60-65 ; skeleton of, 60 ; sarcoids of, 61 ; aquiferous system of, 61 ; repro- duction of, 62; classification of, 63; dis- tribution of, in space, 64; in time, 64; affinities of, 65 ; individuality of, 65. Spongilla, 47 ; reproduction of, 62, 63 ; sarcoids of, 64. Spoon-bill, 450. Spoon-worm, 177, 178 Spores, of Sponges, 63. Sporosac, of Corynida, 82. Spring-tails, 242. Squamse, of Aphrodite, 186. Squamata (Reptilia), 395. Squids, 304, 306. Squilla, 214. Squirrel, 545. Staggers, of Sheep, 163. Statoblasts, 26, 264. Stauridce, 134. Stauridia, 84. Steganodictyum, 65. Steganophthalmata (Medusas), 96, 101, 105. Stem-muscle, of Vorticella, 68. Stem ma ta (see Ocelli). Stenaster, 157. Steneosaurus, 415. Stentor, 9, 70, 71. Stephanoceros, 173, 175. Stephana miadce, 94. Sterelmintha, 165. Stereognathus, 560, 561. Sternaspis, 178. Sternoptixince, 361. Sternum, of Crustacea, 194 ; of Arach- nida, 221 ; of Chelonia, 399 ; of Aves, 428 ; of Mammalia, 474. Stichostega, 54. Stigmata, of Physophoridce, 93; of Leeches, 182; of Arachnida, 224; of Insecta, 238. Stolons, ofForaminifera, 52 ; of composite Actinozoa, 118; of social Tunicata, 255. Stomapoda, 198; characters of, 214; dis- tribution of, in time, 220. Stomatodendra, 104. Stork, 449. Strepsiptera, 251. Strepsirhina, 552, 553. Streptospondylus, 415. Stripidce, 464. Stringocephalus, 274. Strobila, of Rhizostomidce, 102; of Tceni- ada, 162. Strombidw, 255, 291, 294. Strombus, 294. Strophatosia, 275. Strophomena, 274. Strophomenidce, 274, 276. Struthio, 452. Struthonidce, 451. Sturgeon, 367, 368. Sturionidce, 368, 378. Stiirnidce, 460, 461. Stylops, 250. Sub-brachiata, 362. Sub-kingdoms, 14. Suchosaurus, 415. Suctoria (Infusoria), 66, 71. Swcto, 516, 565. SwZa, 446. Surinam Toad, 390. Sws, 517. Suspecta(0phidia), 406. Swallow, 463. Swarm-spores, of Sponges, 63. Swifts, 463. Swim-bladder, of Fishes, 351. Swimmerets, of Lobster, 195, 196, 216. Swimming-bells, 90. Sylviadce, 461, 462. Synapta, 155. Synapticulse, 118. Synaptidce, 153, 155. Syndactyli, 463. Syndendrium, 104. Syngnathidce, 364. Syrinx, 178. Tabanidce, 247. Tabulae, of Corals, 117. Tabulata, 118, 133. Tacky petes, 446. Teenia, 160, 161, 162, 163, 164. Tceniada, 158; characters and develop- ment of, 159-164. Talitrus, 212. Talpa. 550. Talpidce, 550. Tank-worms, 171. Tantalince, 449. Tape-worm, 159, 160, 161, 162, 163, 164. Tapir, 513, 514. Tapiridce, 514. Tardigrada, 224, 225. Tectibranchiata, 292, 296. Teleosaurus, 415. Teleostei, characters of, 357-360; sub- divisions of, 360-364 ; distribution of, in time, 378, 380. Tellina, 285. Tellinidce, 285. Telson, of Crustacea, 192 ; of Lobster, 194 ; of Limulus, 209 ; of Scorpion, 227. Tentacles, of Hydra, 80; of Calycophoridce, 90 ; of Physophoridce, 93 ; of Medusidce, 96 ; of Hydra-tuba, 101 ; of Actinia, 112; of Alcyonaria, 119; of Pleuro- brachia, 125 ; of Holothuroidea, 154 ; of Polyzoa, 258, 262; of Tunicata, 267; of Cuttle-fishes, 300, 306. Tentaculites, 188, 313. Tenthredinidce, 249, Tenuirostres, 460, 462. Terebella, 185 ; development of, 184. Trebratella, 274. INDEX. 621 Terebratula, 256, 272, 273, 274. Terebratulidce, 274, 277. Terebratulina, 274. Teredo, 286. Terguin, of the exoskeletou of Crustacea, 194 ; of Arachnida, 221. Terricola, 182 (see Oligochceta). Termites, 244 ; communities of, 245. Test, of Foraminifera, 50, 51 ; of Echin- oidea, 138, 142 ; of Tunicata, 266. Testacella, 256, 296. Testudinidce, 401. Testudo, 401. Tetrabranchiata (Cephalopoda), 304; characters of, 307; divisions of, 309; distribution of, in time, 314. Tetranychus, 226. Tetrao, 454. Tetraonidce, 454. Teuthidce, 306, 311, 315. Thalassarctos, 535. Thalassemacea, 179. Thalassicolla, 59, 60. Thalassfcollida, 59. Theca, 298, 313. Theca, of sclerodermic corallum, 115. Thecaphora, 86, 88. Thecididce, 274. Thecidium, 274. Thecodontia, 415. Thecodontosaurus, 415. Thecosomata, 298. Thelyphonidce, 228. Theriomorpha, 387 (see .4«owra). Thoracica (Cirripedia), 198, 203. Thread-cells. 76. Thread-worms, 169, 170. Thylacinus, 497. Thylacoleo, 562. Thysanura, 242. Ticks, 225, 226. Tiger, 531, 539, 541. Tipula, 247. Toad, 390. Tongue, of Insects, 236 ; of Gasteropoda, 287 ; of Cephalopoda, 300 ; of Fishes, 344 ; of Snakes, 403 ; of Lizards, 409 ; of Crocodile, 414; of Birds, 433, 434, 440. Tornatella, 296. Tornatellidce, 292, 296. Torpedo, 374. Tortoise Encrinite, 156. Tortoises, 394, 395, 397, 401, 402. Tortrix, 402. Totipatmatce, 446. Toucan, 457, 458. Toxocerds, 310. Toxodon, 493. Tracheae, 223 ; of Arachnida, 223 ; of Myriapoda, 231 ; of Insecta, 288. Trachearia (Arachnida), 224. Trachyderma, 188. Trachynema, 98. Trachynemidce, 98. Transformation, 33. Trematis, 275. Trematoda, 158 ; general characters of, 164, 165 ; development of, 164 ; habitat of, 164. Tremoctopus, 311 ; reproduction of, 302. Triarthra, 175. Trichecidce, 532, 533. Trichecus, 533. Trichina, 170. Trichocysts, 71. Triconodon, 560, 562. Tridacna, 285. Tridacnidce, 284. Trigonia, 284. Trigoniadce, 283, 284. Trilobita, 198, 2u7; structure of the crust of, 208 ; distribution of, in time, 220. Tringidce, 450. Trionycidce, 401, 402. Trionyx, 401. Triton (Mollusca), 294 ; (Amphibia), 387. Tritonia, 296. Tritoniadce, 292, 296. Trochilidce, 462. Trochoceras, 310, 312. Trochoid shell, of Foraminifera, 53 ; of Gasteropoda, 289. Trochus, 295. Troglodytes, 462, 557. Trogontherium, 568 Trophi, of Insects, 235, 236. Trophosome, 78. Truncated Shells, 257. Tube-feet of Echinus, 141; of Asteroidea, 145; of Ophiuroidea, 147 ; ofCrinoidea, 149 ; of Holothuroidea, 153. Tubicola, 181 ; characters of, 184 ; deve- lopment of, 184; distribution of, in time, 188. Tubifex, 183, 188. Tubiporidce, 120, 124. Tubularia, 81, 85. Tubularida, 81 (see Corynida). Tubulosa, 118, 134. Tunicata, 254, 255 ; characters of, 265 ; respiratory process of, 268 ; circulation of, 268 ; reproduction of, 268 ; homolo- gies of, 269 ; divisions of, 270 ; distribu- tion of, in space, 276 ; in time, 276. Tunics, of Ascidians, 266. Turbellaria, 158 ; characters of, 166 ; di- visions of, 166. Turbinated Shells, 289. Turbinidce, 292, 295. Turkey, 454. Turrilites, 310, 311, 312, 315. Turritella, 291, 295. Turritellidce, 292, 295. Turtles, 398, 401. Tylenchus, 171. Tylodina, 296. Type, morphological, 14. UMBILICATED shell of Gasteropoda, 290. Umbo, 256, 279. Umbrella, 296. Umbrella of Lucernarida, 99. Ungulata, 484, 487; characters of, 511-513 ; divisions of, 513-526; distribution of, in time, 564-566. tfmo, 284. Unionidce, 283, 284. Univalve Shells, 256, 286, 289. Upupidce, 462. tTrwi, 445. Uraster, 146. Urnatella, 263. 622 INDEX. Vrodela, 382; characters of, 3S4. Ursidce, 534. Ursus, 535, 568. Urus, 5(36. VACUOLES, of Protozoa, 47, 48 ; of Infu- soria, 67, 70. Vaginicola, 70, 71. Vaginulus, 296. Valkeria, 262. Valvata, 295, 313. Varanidce, 411. Varanus, 411. Varices, 290. Veil, of gonophores, 83 ; of nectocalyces, 90 ; of naked-eyed Medusae, 96. Velella, 94. Velellidce, 95. Venenosa (Ophidia), 406. Veneridce, 284, 285; distribution of, in time, 313. Venerupis, 285. Ventriculites, 64. Fe/ms, 285. Venus' girdle, 128. Fermes, 135. Vermetus, 289, 295. Verrucidce, 198, 203 ; distribution of, in time, 219. Vertebra, structure of, 327-329. Vertebrata, 323; general characters of, 323-327 ; skeleton of, 327-332 ; digestive system of, 332; blood of, 334; respira- tion of, 335 ; nervous system of, 336 ; reproduction of, 337; development of, 324 ; divisions of, 337. Vesicle, contractile, of Protozoa, 43; of Amveba, 48; of Paramcecium, 67; of Epistylis, 70. Vesicles, of Medusae, 96, 97. Vespidce, 250. Vespertilio, 548. Vespertilionidce, 548. Vibracula, 261. Vibrios, 35, 36. Viperina, 405, 407. Virgularia, 121. Visceral arches, of the embryo of Verte- brates, 326. Vitrea (Sponges), 63. Viverra, 537. Viverridce, 536, 537. . Vogtia, 90. Valuta, 294. Volutidce, 291, 294. Vorticella,66; structure of, 68 ; reproduc- tion of, 69. Vorticlava, 81. Vulpes, 539. Vulturidce, 465, 466. WAH, 535. Waldheimia, 274. Walrus, 531, 532, 533. Warblers, 461. Wasps, 249, 250. Water-hen, 448. Water-vascular system, of Annuloida, 135; of Echinoidea, 141; of Asteroidea, 145; of Ophiuroidea, 147 ; of Critioidea, 151 ; of Holothuroidea, 154 ; of Scolecida, 158 ; of Tceniada, 159 ; of Trematoda, 164; of Turbellaria, 166; of Acantho- cephala, 168 ; of Nematoda, 169 ; of Rotifera, 174. Weasel, 536. Websteria, 133. Whales, 472, 473, 476, 479, 483, 504, 505. Wolverine, 536. Wombat, 492, 493. Wood-pecker, 457. Wrasse, 363. Wry-neck, 457. Xanthidia, 65. Xiphosura, 198; characters of, 209; dis- tribution of, in time, 220. Xylobius, 233. Xylophaga, 286. ZEBRA, 515. Zeuglodon, 564. Ziphius, 564. Zoantharia, 111; Malacodermata, 111, 129, 133; Sclerobasica, 113, 133; Scleroder- mata, 117, 124, 133. Zoanthidce, 113. Zoanthus, 113. Zoea, 218. Zonites, 313. Zooid, 78. Zoology, definition of, 1. Zootoca, 411. THE END. PRINTED BY WILLTAM BLACKWOOD AND SONS, EDINBURGH. MESSRS BLACKWOOD AND SONS' PUBLICATIONS. Lately published, TEXT-BOOK OP ZOOLOGY, FOR THE USE OF SCHOOLS. By H. ALLEYNE NICHOLSON, M.D., D.Sc., F.R.S.E., F.G.S., Lecturer on Natural History, and Vice- President of the Geological Society of Edinburgh, &c. In Crown Octavo, with numerous Engravings, 6s. EXTRACTS FROM REVIEWS. Lancet. If natural history, he says, is to be taught in schools, with any satisfac- tion to the teacher or any profit to the learner, it must be taught as systema- tically as mathematics and Greek have been taught for many generations. The author's text-book, regarded from this point of view, is a decided suc- cess ; it is just what was wanted. The subject has been treated in a scientific spirit, but at the same time so clearly and so well as to be quite within the comprehension of any young student who will bring ordinary attention to his task. Daily Review. His thorough acquaintance with natural history gives him a most won- derful power of condensing and compressing its most complicated principles, its most perplexing arrangements and descriptions, into such small space that not only is an immense deal of the student's time saved in his being able to comprehend almost at a glance what in old manuals it would take a good many glances to comprehend, but his memory is greatly relieved from the strain of remembering the long, tedious screeds of dry scientific descriptions of which the older manuals are not altogether free It is about the best of the new text-books we know of ; and as the older text-books are not of much use now, we hope Dr Nicholson's work will be found in the library of every student of medicine and science. Nonconformist. This is an excellent treatise for its purpose. Dr Nicholson's style is singu- larly intelligent ; he conveys much information in a small space, and is espe- cially clear in his explanations of the various zoological classes and their characteristics. The introductory chapter is a model of lucid writing on a difficult point, the distinctions between plants and animals We have only to add that Christian teachers and the adherents of a spiritual philosophy may safely put this book into the hands of their pupils. There is nothing theological in the book, but on the other hand there is nothing anti-theological. Manchester Examiner. We welcome this little book all the more because it aims not only at con- veying sound elementary knowledge, but is intended, in addition, to assist in making the study of zoology a valuable instrument in developing and training the mental faculties. MESSRS BLACKWOOD AND SONS* PUBLICATIONS. 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