The antennæ are extremely variable in form, generally of eleven joints, sometimes of fewer, rarely of twelve or more. The thorax is composed of a pro- meso- and meta-thorax, but when the elytra are closed, only the prothorax and a little plate ("scutellum ") belonging to the meso thorax are visible. The tarsus is generally composed of five joints, sometimes fewer, never more, and its last joint is usually furnished with two hooked claws. The larvæ of Coleoptera are generally composed of thirteen segments, including the head. The body is generally soft and fleshy, the head horny, and the mouth adapted for mastication. The antennæ are small, usually of three or four joints, with ocelli at their base. They have three pairs of legs attached to the thorax, and rarely anal pro-legs or fleshy tubercles; or they may be devoid of feet. The pupa is sometimes enclosed in a cocoon, and the parts of the perfect insect are always distinctly recognisable in the pupa. Fig. 178.-a Rose-chafer (Cetonia aurata) and larva. The order Coleoptera includes all those insects commonly known as "Beetles," and comprises an enormous number of genera and species. They are remarkable, as a general rule, for their hard polished integument, their glittering, often metallic colours, and their voracious habits. The order Coleoptera was divided by Latreille into four sections, in accordance with the number of the joints in the tarsi; and though the resulting arrangement is not strictly natural, this classification is generally followed. The four sections founded by Latreille are : I. TRIMERA.-Tarsus three-jointed. Ex. Lady-birds (Coccinellida). 2. TETRAMERA.-Tarsus four-jointed. Ex. The Longicorn Beetles (Longicornia), the Weevils (Rhynchophora), &c. 3. HETEROMERA.-Tarsus of the two anterior pairs of legs five-jointed, of the posterior pair four-jointed. Ex. The Blister Beetles (Cantharida), and the great family of the Tenebrionida. 4. PENTAMERA.-Tarsus five-jointed in all the legs. Ex. Soldier beetles (Telephorus), Glow-worm (Lampyris), the Elaterida (the larvæ known as "wire-worms"), the beautiful Buprestide, the great group of the Lamellicorn Beetles (such as the Stag-beetle, Cockchafer, Dung-beetle, &c.), the Burying beetles (Necrophorus), the Devil's-coach-horses (Staphylinida), the Water-beetles (Hydrophilide and Dyticida), the Whirligigs (Gyrinida), the Groundbeetles (Carabida), and the Tiger-beetles (Cicindelida). LITERATURE. GENERAL. I. "Glieder-füssler: Arthropoda," in Bronn's Klassen und Ordnungen des Thier-Reichs.' Gerstaecker. 2. હૂં છે. 3. "Règne Animal.” Cuvier. "Sur un nouveau rapprochement à etablir entre les classes qui composent le règne animal." Cuvier. 'Annales du Muséum. 1812. 4. "Histoire naturelle des animaux sans vertèbres." Lamarck. 1835-45"Handbuch der Zoologie." Carus und Gerstaecker. 1863. in CRUSTACEA. 6. Article "Crustacea," in Encyclopædia Britannica,' 9th Ed. vol. vi. Henry Woodward. ་ 1877. 7. Article "Crustacea." Todd's Encyclopædia of Anatomy and Physi ology.' Milne-Edwards. 1835. 8. "Histoire Naturelle des Crustacés." Milne-Edwards. 1834-40. 9. History of British Stalk-eyed Crustacea.' Bell. 1853. IO. II. 12. 13. History of British Sessile-eyed Crustacea." Spence Bate and J. O. Report on the present state of our Knowledge of Crustacea." Spence "Crustacea of the United States' Exploring Expedition." Dana. 1852-53. 'Facts and Arguments for Darwin." Fritz Müller. English translation of "Für Darwin" by W. S. Dallas. 14. "Monograph of the Cirripedia. 1869. "Ray Society. "Lepa 'Palæontographical So 'Palæontographical So "Natural History of British Entomostraca." Baird. 'Ray Society.' 1850. 'Naturgeschichte der Daphniden.' Leydig. 1860. "Die frei-lebenden Copepoden," &c. Claus. 1863. Monograph of the Recent British Ostracoda. G. S. Brady. Översigt af Norges marine Ostracoder." G. O. Sars. 1865. 22. "On the Anatomy and development of the American King Crab." Owen. 'Trans. Linn. Soc.' 1872. 23. "Development of Limulus polyphemus.' A. S. Packard. 'Mem. Boston Soc. Nat. Hist.' 1871. 24. 25. "Zur Embryologie und Morphologie des Limulus polyphemus." Dohrn. Jenaischen Zeitschr.' 1871. "Recherches sur l'hist. nat. et Anat. des Limules." Van der Hæven. 1838. 26. "On the Relation of the Xiphosura to the Eurypterida." Henry 28. "Report on the Structure and Classification of Fossil Crustacea." Henry Woodward. Rep. Brit. Assoc.' 1871. 29. "Monograph of the British Trilobites." Salter. 'Palæontographical Society. 1862-64. 30. "Monograph of Trilobites.” Bohême. 1852. Barrande. In 'Système Silurien de Brongniart and Des 31. "Organisation of Trilobites.' Burmeister. Ray Society.' 1846. 32. "Histoire Naturelle des Crustacés fossiles." marest. 1822. 33. "Catalogue of the British Fossil Crustacea." Henry Woodward. 1877. 34. "Fossil Estheriæ." 1862. Rupert Jones. Palæontographical Society." Rupert Jones. 35. "British Tertiary Entomostraca." Rupert Jones. 'Palæontographi cal Society.' 1856. 36. "On the Development of the Decapod Crustacea." 'Phil. Trans.' 1858. Spence Bate. 37. "Malacostraca Podophthalma Britannica." Leach. 1815-75. (Completed by G. B. Sowerby). 41. Bau und Entwickelungs-geschichte der Pentastomiden." Leuckart. 43. "Mémoire sur les Tardigrades." Doyère. 'Ann. Sciences Nat.' 44. "Recherches sur l'organisation et la développement des Linguatules." Van Beneden. 'Nouv. Mém. de l'Acad. de Belg.' 1849. 45. "Beiträge zur Anatomie der Milben." Pagenstecher. 1860. "Ueber Entwickelung und Bau der Pycnogoniden.' Dohrn. In 'Ueber Bau und Entwickelung der Arthropoden.' 1870. 47. "Monograph of the British Species of Phalangiidæ.' 'Ann. Nat. Hist.' 1855. "Die Arachniden." Koch. 1831-48. 49. "Uebersicht des Arachniden Systems." Koch. 1850. 51. "Histoire Naturelle des Insectes Aptères." Walckenaer. 1837. "On the Genera of European Spiders." Thorell. 1870. 54- History of the Spiders of Great Britain and Ireland." 86 'Ray Society.' 1861-64. 55. "De Generatione Aranearum in Ovo." Herold. 1824. 57. MYRIAPODA. 59. "Guide to the Study of Insects." Packard. 1872. 60. "On the Organs of Reproduction and the Development of the Myriapoda.' Newport. Phil. Trans.' 1841. 61. Article "Myriapoda." Rymer Jones. 'Todd's Cyclopædia of Anat. and Physiology.' 1839-47. 62. "On Pauropus, a new Type of Centipede." Sir John Lubbock. 'Trans. Linn. Soc.' 1868. 63. "Ueber den Bau von Peripatus Edwardsii." Grube. 'Archiv 64. "On the Structure and Development of Peripatus Capensis." H. N. Moseley. Proc. Roy. Soc. 1874; and Ann. Nat. Hist.' 1874. 65. "On Peripatus Novo-Zelandia." Capt. F. W. Hutton. 'Ann. Nat. Hist.' 1876. 66. "Embryologie der doppelt-füssigen Myriapoden.” 'Siebold und Kölliker's Zeitschrift.' 1874. 67. "Embryologisches über Geophilus." Kölliker's Zeitschrift.' 1875 Metschnikoff. Metschnikoff. 'Siebold und INSECTA. 68. "Introduction to the Modern Classification of Insects." Westwood. 1839-40. 69. "Introduction to Entomology." Kirby and Spence. 1828. "Handbuch der Entomologie.' Burmeister. 1832-47. 70. 71. "Guide to the Study of Insects." 72. Article "Insecta." Newport. and Physiology.' 1836-39. Packard. 1872. 'Todd's Cyclopædia of Anatomy 73. "Mémoires pour servir à l'histoire des Insectes." De Geer. 1752-78. 74. "Mémoires pour servir à l'histoire des Insectes." Reaumur. 1734-42. 75. Systema Entomologiæ. Fabricius. 66 1775. 76. "Histoire naturelles des Crustacés et des Insectes." 1802-05. 77. "British Entomology." Curtis. 78. "British Butterflies. IIumphrey and Westwood. 1841. 79. "British Moths." Humphrey. 1843-45. 80. "British Moths and Butterflies. Newman. 1874. Latreille. 81. "Insects of North America." Say. (Ed. by Le Conte.) 1869. 82. 83. Origin and Metamorphoses of Insects." Sir John Lubbock. 1874, "On the Thysanura.' Sir John Lubbock. 'Trans. Linn. Soc.' 84. Monograph of the Collembola." Sir John Lubbock. 'Ray Society.' 85. "Transformations of Insects." Martin Duncan. 1875. MOLLUSCA. CHAPTER XLI. SUB-KINGDOM MOLLUSCA. SUB-KINGDOM MOLLUSCA.-The Mollusca may be defined as including soft-bodied, unsegmented animals, which are usually provided with an exoskeleton. The intestinal canal is bounded by its own proper walls, and is completely shut off from the perivisceral cavity. The alimentary canal is situated between the hæmal system, which lies dorsally, and the neural system, which is situated towards the ventral aspect of the body. The nervous system (fig. 179) in its highest development consists of three principal ganglia, which are reduced to one in the lower forms. Usually there is a distinct propulsive organ by which the circulation is carried on, but this is occasionally ab n sent. Distinct respiratory Fig. 179.-Diagram of a Mollusc. organs may or may not be present. Reproduction is sexual, though gemmation a Alimentary canal; Heart; f Foot; " Cerebral ganglion; Pedal ganglion; "" Parietosplanchnic ganglion. is also occasionally superadded. The higher Mollusca are all simple animals, but many of the lower forms are capable of forming colonies by continuous gemmation. The digestive system in all the Mollusca consists of a mouth, gullet, stomach, intestine, and anus-though in some of the Brachiopoda, and in a few other forms, the intestine ends cæcally. In some the mouth is surrounded by ciliated tentacles (Polyzoa, fig. 182); in others it is furnished with two ciliated arms (Brachiopoda, fig. 187); in the bivalves (Lamellibranchiata) it is mostly furnished with four membranous processes or palpi (fig. 191); in others it is provided with a com |