234 SEASIDE DIVINITY. 



spine is furnished with a socket, into which the 

 little point or prominence fits, so that the spine 

 revolves upon it precisely in the manner of what 

 is called by engineers a universal joint, a kind 

 of mechanism exemplified in the shoulder joint 

 of the human frame, with this difference, that in 

 the human arm the convex part of the apparatus 

 revolves in the socket, whereas, in the case now 

 referred to, the spine with the socket revolves 

 upon the stationary convexity or point. 



The spines thus adjusted are put in motion by 

 a set of appropriate muscles, acted on by nerves 

 obeying the instincts of the animal. From each 

 of the holes already mentioned issues a sucker, 

 by which the urchin either attaches itself to one 

 place or changes its position. Among the spines 

 are likewise numbers of minute pincers, called by 

 naturalists pedicellarice, consisting of a stalk with 

 a knob at the end furnished with three hard 

 teeth, some obtuse and others elongated. The 

 use of these pincers does not appear to have 

 been ascertained ; but whatever be the special 

 use for which they are intended, they are beyond 

 doubt, like all the understood portions of the 

 complex structure, adapted with inimitable skill 

 to the purpose intended. 



If, again, we examine the mouth of the urchin, 

 we shall find its mechanism to be extremely com- 

 plex. It is scarcely possible, indeed, to convey a 

 suitable notion of it without pointing out its parts 

 in a living specimen ; but sufficient may be said to 

 incite the reader to examine for himself. The 



