70 A NATURAL HISTORY OF THE SEAS 



In spring the female produces masses of pinkish ova 

 ranged on the inside of the shell, and this has a pleasant 

 flavour. When ripe they are discharged into the water 

 as minute larvae, which pass through many complex 

 metamorphoses before attaining the parent form. A single 

 Sea Urchin may produce 20 million young. 



Many foreign species have enormously long spines, 

 whilst in one family the spines are stout, cigar-shaped 

 structures. 



The Heart- or Sand-Urchin {Echinocardium cordatuni) has 

 a flattened heart-shaped shell with five curved spines, 

 but no trace of the " lantern " or jaws and teeth. The 

 spines may be used to shovel the creature below the sand, 

 where it makes a burrow about nine inches deep connecting 

 with the sea floor by a narrow opening. Certain of the 

 tube feet act as respiratory organs, whilst those used for 

 catching food may be extended to several times the length 

 of their owner. Many Sea Urchins do considerable 

 damage to oyster and scallop beds, smothering the bivalves 

 or drilling holes through their shells by means of their 

 sharply-pointed " teeth." 



Certain Urchins known as Shelled Urchins in this 

 country are much flattened and not more than \ inch 

 from back to front. Owing to their compressed form they 

 cannot right themselves when inverted, and it thus happens 

 that many thousands are cast ashore during gales. In 

 America these Urchins are known as " Sand Devils " 

 and are sometimes pounded down to make an indelible 

 writing fluid. 



Although its representatives are only related to the 



