338 



THE INHABITANTS OF THE SEA. 



It is large enough to admit of the creature's rising a little, but 

 not of its coming out easily. The echinus adheres so firmly to 

 this cavity by its suckers, as to be forced from it with extreme 

 difficulty when alive. On the coasts of the county of Clare 

 thousands may be seen lodged in the rock, their purple spines 

 and regular forms presenting a most beautiful appearance on 

 the bottoms of the grey limestone rock-pools. How the boring 

 is performed has, like many other secrets, not yet been settled by 

 naturalists. The first perforation is most likely effected bv 

 means of the teeth, and then the rock softened by some secreted 

 solvent. 



Sea-urchins are found in all seas, but as they are extremely 

 difficult to preserve, and many of them have such long and deli- 

 cate spines that it is almost impossible 

 to procure perfect specimens, probably 

 not one tithe of their species is known. 



On our coasts the common " egg-ur- 

 chin " affords the poor a somewhat scanty 

 repast ; but, throughout the Mediterra- 

 nean, its greater size, and also that of its 

 allies, Echmus melo and E. sardiem, 

 render them, when "in egg," important 

 articles of food. In Sicily these animals are in season about the 

 full moon of March ; there the E. esculentus is still called the 

 " King of Urchins ; " whilst the larger melon-urchin is popularly 

 considered to be its mother. The size and abundance of these 

 edible species are among the striking peculiarities of the fish 

 markets of the Mediterranean sea-board. 



The calcareous shell of the " sea-urchin " seems, at first sight, 

 to be composed of one simple crust, but proves, on nearer in- 

 spection, to be a masterpiece of mosaic 

 consisting of several hundred parts, 

 mostly pentagonal. These are so closely 

 united that their junctions are hardly 

 visible, but on allowing the shell to 

 macerate for some days in fresh water, 

 it falls to pieces. This complicated 

 structure is by no means a mere archi- 

 tectural fancy, a useless exuberance of ornament, but essen- 

 tially necessary to the requirements of the animal's growth. A 

 simple hard crust would not have been capable of distension, 



Mammillated Sea-Urchm. 



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Edible Sea-Urchm. 



