SEA-URCHINS AND SEA- CUCUMBERS. 295 



at your eye, over the shell, you perceive that the spines, 

 though all formed on a common model, differ considerably 

 in the detail of their form. I have shown you what may 

 be considered the average shape ; but in some, especially 

 the finer ones that clothe the sides, the club is slender and 

 pointed ; in others, as in those behind the mouth, which 

 are the largest and coarsest of all, the club is dilated into 

 a long flat spoon ; while in the long, much-bowed spines 

 which densely crowd upon the back, the form is almost 

 uniformly taper throughout and pointed. 



The animal sinks into the sand mouth downwards. The 

 broad spoons behind the mouth come first into requisition, 

 and scoop away the sand, each acting individually, and 

 throwing it outwards. Observe how beautifully they are 

 arranged for this purpose ; diverging from the central line, 

 with the curve backwards and outwards. Similar is the 

 arrangement of the slender side-spines ; their curve is still 

 more backwards, the tips arching uniformly outwards. 

 They take, indeed, exactly the curve which the fore-paws 

 of a mole possess (only in a retrograde direction, since 

 the Urchin sinks backwards), which has been shown to be 

 so effective for the excavating of the soil, and the throwing 

 of it outwards. Finally, the long spines on the back are 

 suited to reach the sand on each side, when the creature 

 has descended to its depth, and by their motions work it 

 inward again, covering and concealing the industrious and 

 effective miner. 



Thus we have another instance added to the ten thousand 

 times ten thousand, of the wondrous wisdom of God dis- 

 played in the least and most obscure things. " All Thy 

 works shall praise Thee, Lord ! " (Ps. cxlv. 10.) 



There is an order of animals which naturalists put in 

 the same category as the Sea- Urchins, but which an un- 

 scientific observer would regard as possessing little or no 

 affinity with them. Some are like long, soft, and fleshy 

 worms, and others, which come the nearest to the crea- 



