SEA-CUCUMBEKS. 139 



settled by naturalists. The first perforation is most likely 

 effected by means of the teeth, and then the rock softened by 

 some secreted solvent. 



On our coasts the common egg-urchin affords the poor a some- 

 what scanty repast, and throughout the Mediterranean its greater 

 size, and also that of its allies (Echinus melo, sardicus), render 

 them, when 'in egg,' conspicuous objects in the fish markets; 

 but as articles of food and trade they are far surpassed by the 

 holothurise, or sea-cucumbers, which are caught by millions, 

 and give employment to thousands of fishermen on the Indian 

 Ocean, or among the isle-clusters of the Pacific. These animals 

 may be regarded, in one light, as soft sea-urchins ; and, in an- 

 other, as approximating to the annelides or worms. Their 

 suckers are similar to those of the true star-fishes and sea- 

 urchins. Besides progression by means of these organs, they 

 move like annelides, by the extension and contraction of their 

 bodies. The mouth is surrounded by plumose tentacula, the 

 number of which is always a multiple of five. They all have 

 the power of changing their shapes in the strangest manner, 

 sometimes elongating themselves like worms, sometimes con- 

 tracting the middle of their bodies so as to give themselves the 

 shape of an hour-glass ; and then again puffing themselves up 

 with water so as to be perfectly globular. Under the influence 

 of terror they dismember themselves in the strangest manner. 

 Having no legs or arms to throw off, like their relations the 

 brittle-stars, they simply disgorge their viscera and manage to 

 live without a stomach, no doubt a much greater feat than if they 

 contrived to live without a head. The loss is, however, made up 

 in course of time by a wonderful power of regeneration, even if 

 the process of disgorgement was so complete as to leave but an 

 empty sack behind. 



Nothing can be more curious than the developmental history 

 of the echinoderms, for here the embryonic mass is converted, not 

 into a larva, which subsequently attains the adult form by a 

 series of metamorphoses, but into a peculiar zooid 9 which seems 

 to exist for no other purpose than to give origin to the 

 echinoderm by a kind of internal germination, and to carry it 

 to a distance by its active locomotive powers so as to prevent 

 the spots inhabited by the respective species from being over- 

 crowded by the accumulation of their progeny. 



