Great Black-Stone Trepang; Peach-blossom Trepang; Great White-Stone Trepang; The Bald Trepang; The Scarlet Trepang; Great Clear-Ball Trepang; The Middle Ash-Bald Trepang, &c., &c. The illustration on Plate 11 gives a good idea of the typical form of the Holothuriadæ. It represents a species of the genus Cucumaria, _C. communis_, or common Sea-Cucumber. Its length is from four to eight inches; but, like all its kindred, it possesses the power of considerably extending or contracting its body at will. The Tentacula are ten in number, pinnate and plumose, stalked and rather large. The body is five-sided, with numerous suckers on the angles, but more on the sides, which are papilose. The colour is yellow, or brownish-white, although specimens found on the Irish coast exhibit a purplish hue. This, the most common species of its genus, is an inhabitant of deep water, and is therefore most frequently taken with the dredge. Occasionally, specimens may be found after violent storms stranded on various parts of the shores of the United Kingdom. The Sea-Cucumbers possess the singular power of disembowelling themselves upon the slightest provocation, and also of throwing off their Tentacula entire. There is one species, indeed, that exhibits a still more wonderful phenomenon. At certain times members of this species will divide their body into a number of parts, each of which will in due course become a new and completely-formed animal. After this the reader will be prepared to learn, that to build up a new inside, or create a new set of branchiæ, is to a Holothuria a very trifling and insignificant task. CHAPTER XXI. The Aplysia, or Sea-Hare. 'The origin and the source of the smallest portion of the universe overpowers our comprehension. How little can the acutest senses, the profoundest judgment, the widest view, embrace! It is as nothing; it is as less than nothing. We are capable of doing no more than surveying the edifice and adoring the Architect.' SIR J. DALYELL. XXI. At several parts of the Scottish coast, and especially at North Berwick, may be found specimens of that curious gasteropod named the Aplysia, or Sea-Hare, the _Lepus marinus_ of the ancients. On visiting North Berwick during summer, I have been astonished to discover, in almost every pool, from two to twenty of these creatures. At rest, the Aplysia is not by any means inviting, but when in motion, elevating and depressing the fleshy mantle that covers over the fringed and lobed branchiæ, its appearance is exceedingly graceful. Striding across a pool on the look-out for some Gobies, whose forms darting beneath a large stone had not escaped my glance, I perceived the water in the rocky basin gradually lose its crystal brightness, and become changed to crimson. The Gobies were therefore allowed to rest in peace, while I proceeded to investigate a phenomenon that, at the moment, seemed somewhat singular.