HOW SEA-URCHINS GROW. 93 
a stony network in which crabs and small fishes are 
entangled and so caught for food. 
Here we have then three types of prickly-skinned 
animals all bearing rays, and all having the same pecu- 
liar water-tubes, yet each of them has his own differ- 
ent life, the feather-star, scarcely yet caring for his 
freedom, feeding almost in the same way as the 
polyps do among the lasso-throwers ; the brittle-star 
with his active restless arms wriggling into cracks 
and seizing young crabs and shell-fish in his grasp ; 
and the gliding star-fish with its thousands of tube- 
feet, creeping over its victims and carrying havoc 
wherever it goes. 
But we have by no means yet exhausted the 
quaint designs of this ray-like structure; on the 
contrary, we come now to the most fantastic and 
whimsical creatures, not only among the tube-footed 
animals, but perhaps among all the inhabitants of 
the sea. 
Is it because the sea-urchins know themselves to 
be as grotesque as the goblins of fairy tales, and as 
uncanny as rolled -up hedgehogs seen in the dim 
moonlight, that they hide themselves so persistently 
in the cracks of rocky pools, or bore holes in the 
limestone in which to hide their prickly bodies, or 
wrap themselves up in seaweed packed deftly between 
their spines ? Or is it not more likely that they 
know too well the brittleness of their formidable 
looking spines, and either keep out of the way of the 
rolling waves and currents or protect themselves from 
their violence by a padding of soft seaweed ? 
Be this as it may, they are not always easy to 
