THE SEA-URCHINS. 165 
apparatus consists of no less than thirty pieces. The teeth are 
long, sharp, curved, and very hard. They can cut the hardest 
substances. However, in spite of their adamantine character, they 
would soon be worn down by work; but Nature has wisely pro- 
vided for their renewal. They grow from the base as they are 
worn down at the points, like the incisors of beavers, hares, or 
rats; so that they are always sharp, and always in good working 
order. 
The urchins live upon sea-weeds, worms, mollusks, and even 
fishes. Professcs Rymer Jones saw one of these creatures seize a 
THE BUCCAL APPARATUS OF AN ECHINUS, MAGNIFIED. 
(Aristotle's lantern.) 
live crab, which appeared perfectly paralysed, and attempted no 
resistance. At another time, an urchin caught a Galatea by its 
buccal appendages; but the galatea, happily for itself, opened its 
pincers, cut off the part held by the urchin, and so escaped. 
Many of these urchins, though defended by a calcareous 
shell, and by sharp, pointed spines, do not consider themselves - 
sufficiently secure ; for they hollow out holes in the hardest rocks 
in which they ensconce themselves. To effect this really difficult 
task, they fix themselves by their tentacles to the surface of the 
¢ rock; they then make an incision by means of their powerful 
