170 THE SEA SHOES 



outgrowths of a system of water tubes similar to that of the urchin, 

 there being a circular tube round the mouth, from which branch 

 five radial tubes, one for each row. 



The mouth of the sea cucumber is surrounded by plumed 

 tentacles which can be retracted at will, and which are used in 

 capturing the smaller living things that form its food. Like the 

 earthworm, it will often swallow large quantities of sand, from 

 which it digests the organic matter contained. 



The body-wall of the Holothuroidea is strong and muscular, 

 and is strengthened by the presence of numerous spicules of 

 carbonate of lime, often in the form of little anchors, wheels, and 

 crosses, while the outer surface is rough and slimy, and often of 

 a colour so closely resembling the surroundings of these animals 



FIG. 115. THE SEA CUCUMBER 



that they are not easily observed. This feature is one of great 

 value to the creatures, since they have no means of defence from 

 their enemies, and seem to owe their safety entirely to their 

 protective colouring. 



There are several species of sea cucumbers on our coasts, but 

 all inhabit deep water and are seldom to be seen above low-water 

 level. They are, as a rule, easily obtained from fishermen, who 

 will bring them in when requested to do so. Live specimens may 

 be kept for a considerable time in the indoor aquarium, and seem 

 to prefer a rocky bottom on which they can hide under stones at 

 times, and a bed of sand on which they will occasionally crawl. 

 They will readily devour small molluscs and crustaceans, and 

 will partake of dead organic matter in a partially decomposed 

 state. 



