"A Holothuroidea may be regarded in one light as a soft Sea Urchin, in another as a radiated animal, approximating the An nalides." " In common language they are generally known by the appellation of Sea cucumbers ;' and in fact, to a casual observer, the resemblance which they bear to those productions of the vegetable kingdom, both in shape and general appearance, is sufficiently striking. The integument which covers, or rather forms the body, is entirely destitute of those calcareous pieces which encase the Echini and Star-fishes ; but appears to consist of a dense fibrous cutis of considerable thickness, covered exter nally with a thin epidermic layer. Beneath the cutis is another tunic composed of strata of tendinous fibres crossing each other in the midst of a tissue of a semi-cartilaginous nature, which is capable of very great distention and contraction, and serves by its elasticity to retain the shape of the body. Within this dense covering are seen muscular bands running in different directions, which by their contraction give rise to the various movements of the creature. But although the calcareous shell of the Echinus is thus totally lost, the locomotive suckers or feet already de scribed are still the principal agent employed in progression. In many species, these organs are distributed over the whole sur face of the animal, and are protruded through countless minute orifices which perforate the integument. In other cases, they are arranged in five series, resembling the ambulacra of an Echinus ; and in some instances they are only found upon the middle of the ventral surface of the body, that forms a flattened disc upon which the animal creeps somewhat in the manner of a snail. The ambulacral feet themselves precisely resemble in all the details of their structure those of the Asterias, and their pro trusion and retraction are effected in the same manner. The mouth is a round aperture, as wide as a goose-quill, placed in the centre of a raised ring at the anterior extremity of the body. Around the oral orifice is placed a circle of tentacula, which are apparently extremely sensible, and serve perhaps not only as in struments of touch, but as prehensile organs used for the cap ture of prey, or for assisting in deglutition." " Sir John Graham Dalyell stated in 1840 that he had observed the Holothurim lose the tentacula, with the cylinder (dental ap paratus), mouth, oesophagus, lower intestinal parts, and the ovarium, separating from within and leaving the body an empty sac behind. Yet it does not perish. In three or four months all the lost parts are regenerated, and a new funnel, composed of new branches as long as the long body of the animal, begins to exhibit the same peculiarities as the old one, though longer time be required to attain perfection. Other species of the Holothu
ria divide spontaneously through the middle into two or more parts, all becoming ultimately perfect by the development of new organs. Yet the anatomical structure of the whole genus is so complex as to defy the skill of anatomists in discovering the proper functions of some of the parts. A single Holothuria has produced 5000 ova in the course of a night. Of one genus, the Trepang, many species are eaten. In Mr. F. D. Bennett's interesting Account of a Whaling Voyage round the Globe,' we are told that there are two kinds of Trepang abundant on the rocks at Raiatia, and they are very indolent animals. When handled,' says Mr. Bennett, 'the Trepang contracts its body in a longitudinal direction, and should its tentacles be expanded they are instantly concealed ; but no noise or agitation of the sur rounding water will excite these symptoms of alarm, or cause any attempt to escape. They usually lie exposed in the shallow waters, though we have very often seen them buried in beds of coral sand, their plumy tentacles being alone exposed, and float ing in the water above, apparently as a lure for prey. Some may also be observed lying on the rocks, their bodies completely encrusted with coral sand, which may either have been accumu lated by a previous burrowing, or thus used as a disguise. It would appear to be partly the instinct of the animal to take its prey in ambush ; but what that prey is, as well as the entire economy of these Moluscs, remains a perplexing mystery. Their intestines invariably contain many hard and solid masses of madreporic rock or tree-coral, some of them more than an inch in length, and all moulded as pellets to the calibre of the intes tinal canal. It is difficult to say how these stony bodies have been obtained by the Trepang, though it is easy to conceive that they may be rendered serviceable as nutriment by the assimila tion of the animal matter they contain. It is this animal which the Malays of the Oriental Isles seek so diligently, for the supply of the China market, where it obtains a good price when well preserved. It is employed by the Chinese in the preparation of nutritious soups, in common with an esculent sea-weed, Shark's fins, edible bird's nests, and other materials, affording much jelly.' Jaeger says the intestines are extracted, the animal then boiled in sea-water, and dried in smoke."