HOLOTHVROIDR&. 



" sea-cucumber" expresses with wonderful exactness the shape of the 

 animal, and its habitation, the sea ; and, again, it would puzzle the 

 most learned to explain the word Holothuria. The body of this 

 strange creature presents the form of an elongated and worm-like 

 cylinder ; its dimensions are so variable that, while some species are 

 only an inch or two in length, others attain thirty and even forty 

 inches. In general, the skin of the Holothuria is thick and leathery ; 

 it is provided with muscles, and is armed occasionally with small 

 projecting hooks or anchors, which enable the creature to hang for a 

 few seconds on to foreign bodies. From this coriaceous envelope 

 issue ambulacral feet analogous to those described in the sea-urchins 

 and sea-stars. 



When we open a Holothuria we find nearly the whole internal 

 cavity occupied with little white tubes. We know that the fabulous 

 cucumber spoken of in the " Arabian Nights " was stuffed with pearls 

 by the talking-bird. With our poor animal this, alas ! is not so. 

 These are no pearls, but simple prosaic caecal tubes. The mouth 

 opens at the extremity of the body ; it forms a sort of funnel, and is 

 surrounded like a crown, with an elegant circle of tentacula. In the 

 living animal, when it feels itself in security, these tentacles expand 

 themselves like the corolla of a flower. When the fisherman seizes a 

 Holothuria in the water this crown of tentacles ceases to appear, for 

 the animal has the power of withdrawing it quite suddenly, and now 

 it resembles nothing so much as a common leech. If, however, it is 

 preserved in fresh sea-water, and left in peace if we treat it, in short, 

 with the regard due to its elegant crown of tentacles this elegant 

 ornament will be expanded in all its glory. Immediately below the 

 mouth is a muscular pharynx, which is contained in a long intestine, 

 with many convolutions, which terminate in the posterior part of the 

 body in an orifice whence is thrown from time to time a little jet of 

 water. The terminal portion of the intestinal canal in these animals 

 is enlarged, introducing us to a system of numerous tubes which 

 branch oft" into the visceral cavity, receiving the water from without 

 while breathing by its posterior extremity ; the animal can at will 

 fill this reservoir or eject the water, and it is by these alternate 

 movements of inspiration and its reverse that it renews the oxygen 

 necessary for respiration. The circulation appears to form a com- 

 plete circle, there being no heart or central organ ; but a ring round 

 the gullet, from which issue five principal nervous chords, represents 

 the nervous system. 



The Holothuria are of separate sexes, and they differ from the sea- 

 urchins and star-fishes in this : that the ova are developed in many 



