50 



FIB8T LESSONS IN ZOOLOGY. 



to which the spines are attached. The sand-cake urchin 

 (Pig. 51) is very flat, with minute spines. 



On placing an Echinus in sea-water the movements of 

 the animal, especially its mode of drawing itself along by 



— 'iimi nitniiiiiiiiiiiiiiiiiiiiiiiiiiiiiiw iiii iiiiiiii iiiiiiiiiiiiiiiiiiiiiiiiiiMiiiiiiiiii— nM 



Fig. 53.— Echinus on its back. 



its numerous long suckers, and how it covers itself by 

 drawing together bits of sea-weed and gravel, may be ob' 

 served. 



Of course the sea-urchin is a heavier, clumsier creature 

 than the starfish, and when turned over on its back feeble 



Flo. 63.— Echinus extending its suckers on beginning to right Itself. 



ones cannot right themselves; but a fresh, vigorous urchin 



can turn itself over in the manner indicated by Figs. 52-55. 



Sea-urchins live in nooks and crannies in the rocks, away 



from the wash of the waves, as they are clumsy creatures, 



