49. _Mimonectes loveni._ A FEMALE SPECIMEN SEEN FROM THE SIDE AND FROM BELOW, SHOWING THE DISTENDED-BALLOON-LIKE FORM OF THE ANTERIOR PART OF THE BODY. × 3 145 50. THE ZOËA LARVA OF A SPECIES OF _Sergestes_, TAKEN BY THE "CHALLENGER" EXPEDITION. × 25 146 51. THE NAUPLIUS LARVA OF A SPECIES OF BARNACLE OF THE FAMILY LEPADIDÆ, SHOWING GREATLY-DEVELOPED SPINES. FROM A SPECIMEN TAKEN IN THE ATLANTIC OCEAN, NEAR MADEIRA. × 11 147 52. _Calocalanus pavo_, ONE OF THE FREE-SWIMMING COPEPODA OF THE PLANKTON. ENLARGED 148 53. _Copilia quadrata_ (FEMALE), A COPEPOD OF THE FAMILY CORYCÆIDÆ, SHOWING THE PAIR OF LARGE "TELESCOPIC" EYES. × 20 153 54. _Phronima colletti_, MALE. FROM A SPECIMEN TAKEN IN DEEP WATER NEAR THE CANARY ISLANDS. × 12 154 55. THE BRINE SHRIMP (_Artemia salina_) 164 56. _Chydorus sphæricus_, A COMMON SPECIES OF WATER-FLEA. × 50 166 57. A WATER-FLEA (_Daphnia pulex_), FEMALE, WITH EPHIPPIUM CONTAINING TWO "RESTING EGGS." × 20 167 58. _Bythotrephes longimanus_, FEMALE, WITH EMBRYOS IN THE BROOD-SAC. × 12 169 59. _Diaptomus coeruleus_, FEMALE. × 25 171 60. _Asellus aquaticus_, FEMALE. × 4 173 61. MAP SHOWING THE DISTRIBUTION OF CRAYFISHES 175 62. A WELL SHRIMP (_Niphargus aquilex_). × 7. 185 63. THE SEA-SLATER (_Ligia oceanica_). ABOUT TWICE NATURAL SIZE 200 64. STRUCTURE OF THE BREATHING ORGANS OF _Porcellio scaber_ 202 65. _Armadillidium vulgare._ × 2-1/2 203 66. TWO BRANCHES OF A CORAL (_Seriatopora_) SHOWING "GALLS" INHABITED BY THE CRAB _Hapalocarcinus marsupialis_. ON THE RIGHT THE FEMALE CRAB, EXTRACTED FROM THE GALL AND FURTHER ENLARGED 211 67. _Hyperia galba_, FEMALE. ENLARGED 213 68. A, THE CRAB _Melia tessellata_ CLINGING TO A BRANCH OF CORAL, AND CARRYING IN EACH CLAW A LIVING SEA-ANEMONE; B, ONE OF THE CLAWS FURTHER ENLARGED TO SHOW THE WAY IN WHICH THE ANEMONE IS HELD 216 69. THE COMMON PEA CRAB (_Pinnotheres pisum_), FEMALE. NATURAL SIZE 217 70. _Cirolana borealis._ ABOUT TWICE NATURAL SIZE 219