136 NATURE'S TEACHINGS. 



" I have counted one hundred and thirty-six plates on one 

 ribbon. There are two ribbons on each thoracic segment, and 

 there are seven such segments. Hence, we may compute the 

 total number of prehensile comb-like plates on this portion of 

 the body to be about one thousand nine hundred, each of which 

 is wielded by muscles at the will of the animal ; while, as 

 each plate carries on an average five teeth, there are nearly ten 

 thousand teeth hqoked into the lining membrane of the cell, 

 when the animal chooses to descend. 



" Even this, however, is far short of the total number, be- 

 cause long ribbons of hooks of a similar structure, but of smaller 

 dimensions, run across the abdominal segments, which are 

 more numerous than the thoracic. No wonder, with so many 

 muscles wielding so many grappling-hooks, that the descent is 

 so rapidly effected." 



Lastly, we come to the Walrus, whose strangely elongated 

 upper canine teeth can be used for just the same purposes as 

 the scaling-fork or climbing-spur. As, however, reference has 

 already been made to these tusks, in connection with another 

 department of this work, there is no necessity for occupying 

 space with a second description. 



DEFENCE OF FORT. 



So much for attack ; now for defence. 



The simplest mode of defending a fort, or even a mountain 

 pass, is by throwing or rolling rocks and heavy stones against 

 the enemy. 



Simple as it may appear, it is a very effective one, as can be 

 well understood by those who have rolled a huge stone down a 

 long and steep slope. The stone goes gently enough at first, 

 but rapidly gains speed, until at last it makes great bounds 

 from the earth, tearing and crashing through everything as if 

 it had been shot from a cannon. 



I have seen a stone which was too heavy to be lifted, and 

 had to be prised over the edge with levers, spring completely 

 through the topmost branches of a high tree, scattering the 

 boughs in all directions, and then, alighting on another stone, 

 split into many fragments, just like the pieces of a burst shell. 

 That one stone would have swept off a whole party of soldiers 

 had they encountered it while trying to ascend the slope. 



