LIST OF ILLUSTRATIONS XV PLATE XVII. To face p. 397. a. Microniscus calani, Sars. b. Cyproniscus cypridinæ (Sars). A female (with a male in the normal position) affixed to the body of a Cypridina norvegica. The right valve of the host has been removed. Sars c. Adult ovigerous female of the Cyproniscus, detached, and viewed from above d. Younger female, not yet ovigerous, in lateral view e. Male, probably adult, with the anterior extremity carrying two root-like processes, and embedded in the skin of the Cypridina ƒ. Larva in the last stage of development, seen from above PLATE XVIII. Portunion mænadis, Giard, on Carcinus mænas (Pennant). Portunion Kossmanni, Giard and Bonnier. Giard and Cancricepon elegans, Giard and Bonnier. Lateral view of 397 407 408 413 414 Gigantione Moebii, Kossmann. Dorsal and ventral view of female. Kossmann. PLATE XIX. Helleria brevicornis, von Ebner The head from above, the head and pleon from below; the antenna; mandible, lower lip; first maxilla, second maxilla, maxilliped; first leg; rudimentary first pleopod with opercular plate of the second, stilet of the second pleopod, fourth pleopod showing the opercular plate broadside and edgeways, and the peduncle with the branchial plate; uropod. Von Ebner ་ ILLUSTRATIONS IN THE TEXT 1. The lady in the chair.' [Herbst] . 3. Corystes cassivelaunus (Pennant). [Herbst] 5. Huenia proteus, de Haan, adult male. [de Haan] Page 48 53 10. Dorippe japonica, von Siebold. [de Haan] 131 11. Ranina scabra (Fabricius). [de Haan] 141 12. Zanclifer caribensis (de Freminville). [Henderson] 144 13. Lomis dentata (de Haan). [de Haan] 154 14. Spiropagurus spiriger (de Haan). [de Haan] 165 15. Porcellana longicornis (Linn.), young form. [Stebbing]. 172 16. Ibacus incisus (Péron). [Desmarest] 194 17. Astacus americanus (Milne-Edwards), larval form. [S. I. Smith] 204 18. Astacus americanus (Milne-Edwards), larval form. [S. I. Smith] 19. Astacus americanus (Milne-Edwards), larval form. [S. I. Smith] 20. Sergestes atlanticus, Milne-Edwards. The petasmata [Spence Bate] 21. Procletes biangulatus, Spence Bate. 22. Mysis relicta, Lovén. First maxilla. [G. O. Sars] LIST OF ILLUSTRATIONS xvii Page 23. Mysis relicta, Lovén. Second maxilla. [G. O. Sars] 272 24. Diastylis stygia, Sars. First maxilliped. [G. O. Sars] 297 25. Diastylis Goodsiri (Bell). 26. Diastylis Goodsiri (Bell). Second maxilliped. [Hansen] 298 27. Diastylis Goodsiri (Bell). Female. [Hansen] 310 310 334 28. Eisothistos vermiformis, Haswell. Male. [Haswell] 29. Eisothistos vermiformis, Haswell. Female. [Haswell]. 334 30. Gnathia asciaferus (Hesse). [Hesse] 338 31. Ceratocephalus Grayanus, Woodward. [Haswell] 32. Eurycope gigantea, Sars. [Hansen] The names in italics indicate the sources from which the figures have been copied or adapted. The Brachyura of the Challenger were described by Mr. E. J. Miers, the Anomura by Dr. J. R. Henderson, the Macrura by the late Mr. C. Spence Bate, the Cumacea by Professor G. O. Sars, the Isopoda by Mr. F. E. Beddard. The other pictorial authorities are Gesner's Historia Animalium,' Herbst's 'Naturgeschichte der Krabben und Krebse,' Desmarest's 'Considérations générales sur la classe des Crustacés,' de Haan's • Crustacea ' in von Siebold's Fauna Japonica,' and various papers of modern date by G. O. Sars, S. I. Smith, C. W. S. Aurivillius, H. J. Hansen, C. Bovallius, C. Chilton, MM. Giard and Bonnier, R. Kossmann, W. A. Haswell, and Victor von Ebner. For the text, as distinct from the illustrations, many other authorities would have to be named, but the text will speak for itself. As to the reproduction, on a scale suitable to these pages, of figures so numerous and so diversified from originals neither equal in merit nor uniform in style, I am indebted to Mr. James D. Cooper for the care and skill exhibited in carrying out a task of no mean difficulty. It is conceivable that by origin all the animals of the globe belong to a single family. They now exhibit very great divergence. Between a star-fish and a crocodile, for example, the cousinship is obscure and remote. Yet almost all species may be included within a few principal clans, and these are united one to another by a small number of intermediate forms of life. For the whole series the details of classification will vary with the increase of knowledge. No system has yet been accepted as final. One, which is sufficiently good for our present purpose, distributes animals among nine leading divisions. These are (1) the Protozoa, primitive animals, such as the Foraminifera and Infusoria; (2) the Cœlenterata, in which the bodycavity serves alike for circulation and digestion, a tribe which includes sponges, corals, and jelly-fish; (3) the Echinodermata or prickly-skinned animals, embracing the sea-lilies, star-fishes, sea-urchins, sea-cucumbers, and a |