294 
THE OCEAN WORLD. 
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. In general, the skin of the Holothuria is thick and 
leathery ; it includes muscles, and is armed occasionally with small 
projecting hooks or fangs, which enable the creature to hang for a 
few seconds .on to foreign bodies. From this coriaceous envelope 
issue tentacular feet analogous to those described in the sea-urcbw 
and sea- star. 
When we open a Holothuria we find nearly the whole internal 
cavity occupied with little white tubes. Wc 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, hut simple prosaical tubes containing the ova- 
The mouth opens at the extremity of the body; it forms a sort of 
funnel, and is surrounded, as by a glory, 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 v, ' e 
treat it, in short, with the regard due to its elegant crown of tentacula-' 
this elegant ornament will be expanded in all its glory. Immediately 
below the mouth is a muscular pharynx, which is contained in a 1 ° a £ 
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 111 
these animals is enlarged, introducing us to a system of numerous 
tubes which branch off into the visceral cavity, receiving the water 
from without while breathing by its posterior extremity ; the anim a 
can at will fill this reservoir or eject the water, and it is by these alter 
nate movements of aspiration and its reverse that it renews the oxjS en 
necessary for respiration. Tho circulation appears to form a coniplef® 
circle, there being no heart or central agent ; but a ring round t e 
gullet from which issue five principal nervous chords, which represeu 
the nervous system. 
The Holothiirias are of separate sexes, and they differ from the sea 
urchins and asterias in this : that their larvae are converted bodily i 11 
