176 
Fam. CIDAEID.E. 
ECHINUS.— SEA. EGG. 
Echinus sph^ra, Muller. Common Sea-egg or Sea- 
vrchin . — A wisli has been expressed that I should in- 
clude the sea-egg’^ in my Edible Mollusca/ but I 
scarcely feel justified in doing so, as it is not a mollusk, 
and has no other claim to appear on these pages further 
than from its being fit for food. 
It belongs to another class of animals, the Radiata or 
Echmodermata, which includes the star-fishes and the 
Holoihuriadee. The Radiata are so called because all 
their parts radiate from a common centre. 
Echinus sphcera is generally of a reddish colour, or 
purplish, and has white spines, in some tinged with 
purple. 
Pliny states that the sea-urchin moves along by roll- 
ing like a ball, which is the reason that it is so often 
found with the prickles rubbed off ; also that these 
creatures foreknow the approach of a storm at sea, and that 
they take up little stones with which they cover them- 
selves, as a sort of ballast ; for they are very unwilling, 
by rolling along, to wear away their prickles. As soon as 
seafaring persons observe this, they at once moor their 
ship with several anchors.’^* By Aristotle it is called 
the migratory fish.^^ Professor Forbes, in his ^History 
of British Starfishes,^ observes that ‘‘it is with their 
spines that the Echini move themselves, seize their prey, 
and bring it to their mouths by turning the rays of their 
lower edge in different directions. The mouth is gene- 
rally turned to the ground, and the five teeth which 
project from it form part of a remarkable dental appa- 
* Pliny, Nat. Hist. vol. ii. bk. ix. c. 51, p. 427. 
