SHIP BARNACLES, 13 ACORN BARNACLES attached to Shell of the Limpet, 14 THE LIMPET, as seen from beneath, 15 LAMINATED NEREIS, 16 COMMON MUSSEL,--Shell open, 17 COMMON MUSSEL,--Shell closed, 18 THE BERÖE, 19 FAN AMPHITRITE, 20 TEREBELLA FIGULUS, 21 TEREBELLA LITTORALIS, 22 THE SEA-MOUSE, 23 DORIS, 24 YOUNG OF DORIS, 25 EOLIS, 26 THE PHOLAS, and Valves of its Shell, 27 THE BRITTLE STAR, 28 COMMON CROSS-FISH, 29 COMMON SUN-STAR (with 14 rays), 30 PURPLE-TIPPED SEA-URCHIN, 31 PURPLE-TIPPED SEA-URCHIN, Spine of, 32 PURPLE-TIPPED SEA-URCHIN, Suckers of, 33 THE APLYSIA, or SEA-HARE, 34 TEETH of the SEA-URCHIN (two views), 35 THE SEA-CUCUMBER, 36 SERPULÆ attached to piece of rock, 37 THE SOLEN, or RAZOR FISH, 38 THE BLENNY, 39 THE VIVIPAROUS BLENNY, 40 THE SPOTTED BLENNY, or GUNNEL-FISH, 41 THE MONTAGU SUCKER-FISH (three views), 42 THE MONTAGU SUCKER-FISH, Sucker of (magnified), 43 CHAPTER I. INTRODUCTORY. On the Pleasures derived from the Study of Marine Zoology. 'Woe to the man-- Who studies nature with a wanton eye, Admires the work, but slips the lesson by.' I. As every fresh branch of investigation in natural history has a tendency to gather around it a rapidly accumulating literature, some explanation may probably be looked for from an author who offers a new contribution to the public. And when, as in the present instance, the writer's intentions are of an humble kind, it is the more desirable that he should state his views at the outset. Nor can the force of this claim be supposed to be lessened, from the gratifying fact, that the present writer has already received a warm welcome from the public.