“276 THE OCEAN WORLD. 
at first, to find a reason for this designation. The corona or body of 
the sea-urchin is furnished with different kinds of spines. It forms a 
shell, nearly spherical, empty in the interior, its surface presenting 
reliefs remarkable for their regularity. In order to see the urchin 
with its spines it is necessary to seize it as it lives, in the water at the 
bottom of the sea, where it rolls and moves its little prickly mass ; it is 
then only that the real urchin—the prickly sea-urchin—is to be seen, 
bristling with prickles, and strongly resembling, to compare the physical 
with the mental, those amiable mortals whose character is so well 
depicted in the saying, ‘“‘ Whom they rub they prick.” 
In his book on “The Sea,” Michelet puts the following conver- 
sation into the mouth of a sea-urchin :— 
“‘T am born without ambition,” says the modest Echinoderm ; “I 
ask for none of the brilliant gifts possessed by those gentlemen the 
molluscs. I would neither make mother-of-pearl nor pearls; I have 
no wish for brilliant colours, a luxury which would point me out; still 
less do I desire the grace of your giddy Medusas, the waving charm of 
whose flaming locks attracts observation and exposes one to shipwreck. 
Oh, mother! I wish for one thing only: “ de—to be without these 
exterior and compromising appendages ; to be thickset, strong, and 
round, for that is the shape in which I should be the least exposed ; 
in short, to be a centralised being. I have very little instinct for 
travel. To roll sometimes from the surface to the bottom of the sea is 
enough of travel for me. Glued firmly to my rock, I could there 
solve the problem, the solution of which your’ future favourite, man, 
seeks for in vain—that of safety. To strictly exclude enemies and 
admit all friends, especially water, air, and light, would, I know, cost 
me some labour and constant effort. Covered with movable spines, 
enemies will avoid me. Now, bristling like a bear, they call me an 
urchin.” : 
Let us now look alittle more closely at the general structure of the 
sea-urchin—in zoological language, Echinus. 
The body of the sea-urchin is globular in form, slightly egg-shaped, 
or of a disc slightly swollen. It consists essentially of an exterior 
shell, or solid corona covered with spines, and invested in a delicate 
membrane furnished with vibratile cilia. This corona is formed of an 
assemblage of contiguous polygonal plates, adhering together by their 
edges. ‘Their arrangement is such that the test or shell may be 
divided into vertical zones, each springing from a central point on 
the summit, and terminating at a point of the spheroid diametrically 
opposite—namely, the circumference of the buccal orifice. These 
vertical zones are of two kinds, some larger and others straighter, 
