224 NATURE'S TEACHINGS. 



rapidity, that a strong navvy, armed with the best spade, would 

 not be able to keep pace with a black man armed only with his 

 "katta," or digging-stick. 



In Africa the Digging-stick is used in exactly the same 

 manner, and is generally made more weighty and effective by 

 having a perforated stone fastened on the handle. 



HERB, again, man has been anticipated by Nature, and the 

 savage of Australia or Africa digs in exactly the same manner 

 as the common Heart-urchin of our shores, sometimes called the 

 Hairy Urchin, in consequence of the number and fineness oi 

 the spines, which look just like hairs to the naked eye. The 

 scientific name of this creature is Amphidotm cordatus. 



Mr. Gosse, in his "Evenings at the Microscope," gives so 

 admirable an account of the mode of digging employed by the 

 Hairy Urchin that I cannot do better than employ his own 

 words. After describing the variety of structure of the different 

 spines with which the shell is so thickly set, he proceeds a^ 

 follows : 



" But what is the need of so much care being bestowed upon 

 the separate motion of these thousands of hair-like spines, that 

 each should have a special structure, with special muscles for 

 its individual movement ? The hairs of our head we cannot 

 move individually : why should the Heart-urchin move his ? 



" Truly, these hairs are the feet with which he moves. The 

 animal inhabits the sand at the bottom of the sea in our shallow 

 bays, and burrows in it. By going carefully, with the lens 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 s^oon ; 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 

 hard spoons behind the mouth come first into requisition, 

 scooping away the sand, each acting individually, and throwing 

 it outwards. Observe how beautifully they are arranged for 



