138 THE HARMONIES OF NATURE. 



of the shell and spines covered with a delicate skin, which, in 

 spite of their close connexion, penetrates into the intervals of 

 the several pieces. This membrane secretes the chalk of which 

 the shell is composed, and deposits fresh layers on the edges of 

 the plates, so that in this manner the shell continually widens 

 until the animal has attained its perfect size. The spines are 

 secreted in the same manner by the soft integument which 

 effects their union with the shell at the circumference of their 

 articulation, and exhibit under the microscope an admirable 

 beauty and regularity of structure. So bountifully has the 

 Great Architect of worlds provided for the poor insignificant 

 sea-urchin ! 



Besides the spines there exist on his external surface multitudes 

 of exceedingly minute and* beautifully formed pincers, which as 

 long as the animal lives are in perpetual motion, bending about 

 from side to side, and opening and shutting their three-forked 

 apex continually. These most singular organs, which are also 

 found on IT, any of the star-fishes, (where, 

 however, they are simply forked like 

 the claws of a crab in miniature,) are 

 called by naturalists pedicellariae, and 

 were formerly regarded as parasitic 

 creatures; but from the accurate ob- 

 servations of Mr. Grosse, there can be 

 no doubt that, though their uses are still wholly unknown, 

 they are truly and essentially organic parts of the animal. Both 

 the suckers and the spines serve the sea-urchin as organs of 

 locomotion. With the former he firmly moors himself to the 

 ground, and with the latter some species are able even to en- 

 tomb themselves, pholas-like, in stone. Thus the Echinus 

 lividus inhabits circular cavities evidently formed by himself, 

 and so deep as to embrace two-thirds of his bulk. The burrow 

 is large enough to admit of the creature rising a little, but 

 not of its coming out easily. The echinus adheres so firmly 

 to this cavity by his suckers, as to be forced from it with extreme 

 difficulty when alive. On the coasts of the county of Clare thou- 

 sands may be seen lodged in the rock, their purple spines and 

 regular forms presenting a most beautiful appearance on the 

 bottoms of the grey limestone rock pools. How the boring is 

 performed has, like many other secrets of creation, not yet been 



