INDEX 280 LIST OF ILLUSTRATIONS IN THE TEXT FIG. PAGE 1. THE COMMON LOBSTER (_Homarus gammarus_), FEMALE, FROM THE SIDE 7 2. ONE OF THE ABDOMINAL SOMITES OF THE LOBSTER, WITH ITS APPENDAGES, SEPARATED AND VIEWED FROM IN FRONT 9 3. THIRD MAXILLIPED OF LOBSTER 11 4. WALKING LEGS OF LOBSTER 12 5. APPENDAGES OF LOBSTER IN FRONT OF THIRD MAXILLIPED 13 6. DISSECTION OF MALE LOBSTER, FROM THE SIDE 16 7. GILLS OF THE LOBSTER, EXPOSED BY CUTTING AWAY THE SIDE-FLAP OF THE CARAPACE (BRANCHIOSTEGITE) 18 8. FIRST LARVAL STAGE OF THE COMMON LOBSTER. × 4 28 9. SIDE-VIEW OF ROSTRUM OF (A) COMMON LOBSTER (_Homarus gammarus_) AND (B) AMERICAN LOBSTER (_Homarus americanus_) 32 10. THE "FAIRY SHRIMP" (_Chirocephalus diaphanus_), MALE. × 2 35 11. _Estheria obliqua_, ONE OF THE CONCHOSTRACA 36 12. _Daphnia pulex_, A COMMON SPECIES OF "WATER-FLEA." MUCH ENLARGED 37 13. SHELLS OF OSTRACODA. MUCH ENLARGED 38 14. _Cyclops albidus_, A SPECIES OF COPEPOD FOUND IN FRESH WATER 39 15. _Nebalia bipes._ ENLARGED 44 16. _Mysis relicta_, ONE OF THE MYSIDACEA. ENLARGED 47 17. _Gnathophausia willemoesii_, ONE OF THE DEEP-SEA MYSIDACEA. HALF NATURAL SIZE 48 18. _Diastylis goodsiri_, ONE OF THE CUMACEA. ENLARGED 49 19. _Apseudes spinosus_, ONE OF THE TANAIDACEA. ENLARGED 50 20. A WOODLOUSE (_Porcellio scaber_), ONE OF THE ISOPODA. ENLARGED 51 21. AN AMPHIPOD (_Gammarus locusta_). ENLARGED 53 22. TWO SPECIES OF CAPRELLIDÆ 54 23. _Paracyamus boopis_, THE WHALE-LOUSE OF THE HUMPBACK WHALE 55 24. _Meganyctiphanes norvegica_, ONE OF THE EUPHAUSIACEA. TWICE NATURAL SIZE 56 25. LARVAL STAGES OF THE COMMON SHORE CRAB (_Carcinus mænas_--SEE PLATE IX.) 68 26. LAST LARVAL STAGE OF THE COMMON PORCELAIN CRAB (_Porcellana longicornis_--SEE FIG. 41, P. 113). × 9 70 27. FIRST LARVAL STAGE OF _Munida rugosa_ (SEE PLATE VI.) × 10 71