SEA-CUCUMBERS. 



3*3 



the animal has become flattened, and the tube-feet restricted to three out of the 

 five ambulacra, and by these three the animal creeps about, or holds itself fixed to 

 the rock. A similar modification is carried to excess in the deep-sea holothurians 

 known as Elasipoda. Here, as in the illustrated Scotoplana, there are a couple of 

 rows of thick tube-feet, forming little stumps, with which the animal moves, as a 

 centipede moves by its legs. In front there is a sort of funnel or scoop formed by 

 the short tentacles, while a few of the tube-feet form long horns or feelers on the 

 upper side. In the deep-sea Psychropotes, on the other hand, mouth, vent, and 

 tube-feet are confined to a flat sole; while the posterior part of the body is 



a deep-sea holothurian, Scotoplana (nat. size). 



extended in a long tail. Some holothurians live in mud ; and by reason of 

 constantly keeping both mouth and vent above the surface their bodies have 

 become curved in U-fashion, as seen in the U-shaped Ypsilothuria (illustrated on 

 p. 312). This is carried still further in the club-like Mhopalodina (illustrated 

 on p. 314), a form shaped like a cherry, with a thick stalk ; the openings of both 

 mouth and vent being at the top of this stalk. A yet stranger modification is the 

 holothurian described under the name Pelagothuria, which lives in the Easl 

 Pacific, on the surface of the ocean. It has no calcareous spicules, the longitudinal 

 muscles being mostly changed into a jelly tissue. Around the mouth the body is 

 extended into a kind of disc, prolonged into thirteen to sixteen feelers. The 

 animal swims by the movements of this disc. 



Holothurians have no means of offence, but protect themselves for the most 

 part by assuming the colour of their surroundings. The huge Synapta besseli, 

 which reaches a length of 6 feet, has a habit, when taken in the hand, of squeezing 

 the fluid contents of its body towards the portion that is grasped, till it becomes 

 too big to hold. Some, when much irritated, seem to fade away and dissolve by 



