674 HOLOTHURIDEA. 



tern has been detected in many of the species. Some of them 

 have the bodies raised upon a footstalk, the base of which is 

 fixed ; others have no pedicle, and can move freely, though 

 slovvjy along the bottom. Of the latter kind the Star-fish, Aste- 

 rias, is an example, which drags its slow pace along with the 

 aid of more than eight hundred sucker-like feet. In these, at 

 the extremity of the rays are dots, which, according to Ehren- 

 burg, are eyes. The Echinoderms usually have the mouth 

 armed with hard bony teeth. Both the mouth and the gullet are, 

 in the Star-fish, extremely dilatable, and admirably fitted for se- 

 curing the Crustaceans and Shell-fish upon which they feed. 

 When the prey is over large, the gullet, together with part of the 

 stomach, can be protruded and turned over so as to draw the de- 

 sired food into the cavity. In this way, shell-fish are swallowed 

 whole by these animals ; living specimens have sometimes been 

 taken out of the cavity. 



The sudden and violent dismemberment by which mnnyofthe 

 Echinoderms save their central disk at the expense of their rays 

 or arms, is a striking peculiarity ; the length of time during 

 which these severed parts still continue to be endowed with mo- 

 tion, is also remarkable. These animals have great power of 

 reproducing lost parts, but they do not seem to be able to increase 

 individuals by gemmation, as in the Acalephs and Protozoa. 



FIRST ORDER. HOLOTHURIDEA, (Gr. oloOovgiov, holothourion.) 

 SEA-SLUGS, or SEA-CUCUMBERS. 



These animals have a more or less lengthened and sometimes 

 worm-like body ; it i soft, leathery and contractile, with earthy 

 matter deposited about the mouth, but without any outer shell. 

 When irritated, the contractile power of the body seems to be 

 increased. The general form is quite variable. Over the body 

 are spread numerous pores for the secretion of mucus, and per- 

 forations for the exit of the sucker-like feet. When not generally 

 distributed, these latter organs are arranged in five rows or fur- 

 rows, representing what are fancifully termed ambulacra or ave- 

 nues. The mouth is bordered with tentacles which can be 

 withdrawn. Mariners have named these animals Sea-Cucum- 

 bers, from the resemblance of their form and prickly surface to 

 the garden cucumber. Of the genus Cucumaria, there are sev- 

 eral species, differing in quality, known among the Malays un- 

 der the name of Trepang, or Biche-de-mer. Commodore Wilkes, 

 (Exploring Expedition,) says "the most esteemed kinds are found 

 on the reefs in water, one or two fathoms deep, and are caught 



