284 THE OCEAN WORLD. 
Pedicellaria, which surround the mouth, and are fashioned like 
nippers, are also to be met with, They appear to be altogether 
destitute of organs of sight. It has sometimes been argued that 
five red points at the summit of the dorsal surface are eyes; but 
this opinion has not been maintained, nor has any crystalline lens 
been found in these spots to justify it. Captain de Condé states 
that he examined a sea-urchin with long spines in a pool of water, 
which he tried to catch, when he saw it direct itself towards his 
hand, all its spines being erect. Surprised at this manceuvre, he 
tried to seize it from another quarter; its spines were instantly 
directed to the other side. “I have thought from that time that the 
urchin saw me, and prepared to resist my attack. In order, however, 
to satisfy myself whether or not the movement in the water caused by 
my approach might have produced the effect described, I repeated 
the experiment with greater caution. But the creature always directed 
its spines in the direction of the object which threatened it, whether 
it was in the water or out of it.” He satisfied himself that these 
animals certainly could see, and that their spines served them as a 
means of defence. 
These wonderful spines, this calcareous envelope, this armour so 
marvellously studded, with which Nature has so bountifully provided 
the Echinidz, appear to have been insufficient, inasmuch as these 
very spines, in order to secure the safety of the animal, are gifted with 
the power of hollowing a dwelling for themselves out of solid rocks of 
the hardest material, such as granite and sandstone. They fix them- 
selves to its surface by means of their tentacles ; they make an incision 
by means of their strong teeth, removing the débris with their spines 
as fast as it is produced. When the hole is large enough, they 
entrench themselves in it, with their spines like threatening pikes 
levelled to protect them from all external assaults. To M. Caillaud, 
the conservator of the Museum of Nantes, we are indebted for an 
excellent account of the manner in which this buccal apparatus is 
made to operate. “The Lantern of Aristotle,” says this author, 
“forms the mandibulary apparatus; the teeth are five in number, 
and they may as well receive the denomination of a series of saws and 
picks as of teeth, for they are surprisingly adapted to the excavation 
of holes in the hardest rock. These five picks are about the eighth 
of an inch long, and they serve the sea-urchin at once as masticators, 
and excavating implements. In opening the jaws, these five teeth 
strike the stone forcibly rather than scrape it.” This property of 
hollowing their dwelling out of the solid rock appears, however, to 
belong to only a small number of the Echinide ; most of them are 
