722 



THE COMMON SEA-URCHIN. 



them. The structure of these spines is very remarkable, and under the microscope they 

 present some most interesting details. Moreover, each spine is movable at the will of the 

 owner, and works upon a true ball-and-socket joint, the ball being a round globular pro- 

 jection on the surface of the shell, and the socket sunk into the base of the spine. When 

 the creature is dead and dried, the membrane which binds together the ball-and-socket 

 joint becomes very fragile, so that at a slight touch the membrane is broken and the 

 spines fall off. The beautiful specimen from which the drawing is taken is in the pos- 

 session of Mr. Sowerby, and is remarkable for the fact that the spines are all perfect 

 and in their place. 

 Other peculiarities of structure will be noted in connection with the different species. 



COMMON SEA-URCHIN. Echinus sphsera. 



The Common Sea-urchin is edible, and in some places is extensively consumed, fully 

 earning its title of Sea-egg, by being boiled and eaten in the same manner as the eggs 

 of poultry. 



The fishing for these creatures in the Bay of Naples is graphically and quaintly 

 described by Mr. R. Jones : " I had not swum very far from the beach before I found 

 myself surrounded by some fifty or sixty human heads, the bodies belonging to which 

 were invisible, and interspersed among these, perhaps, an equal numbers of pairs of feet 

 sticking out of the water. As I approached the spot, the entire scene became sufficiently 

 ludicrous and bewildering. . . . Down went a head, up came a pair of heels down 

 went a piir of heels, up came a head : and as something like a hundred people were all 

 diligently practising the same manoeuvre, the strange vicissitude from heels to head and 

 head to heels, going on simultaneously, was rather a puzzling spectacle." 



