284 THE OCEAN WORLD. 



Pedicellaria, which surround the mouth, and are fashioned Hke 

 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 Conde 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 manoeuvre, 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, howe\er, 

 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 Echinidse, 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 debris 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 Echinidae ; most of them are 



