40 



SPINY ANIMALS. 



instances where a protective coat of spines must have 

 been acquired quite independently. 



This independent origin is still more clearly indicated 

 when we come to the consideration of the hedgehog and its 



FIG. 16. The Hedgehog. 



allies, which bear precisely the same systematic relation- 

 ship to the porcupines as is presented by the true moles to 

 the mole-voles, as described in our last chapter. That is to 

 say, whereas the hedgehogs and true moles belong to the 

 insectivorous order, the porcupines and the mole- voles 

 are herbivorous rodents. In spite, then, of the general 

 similarity of appearance between a hedgehog and a porcu- 

 pine, or, still better, a spiny mouse, we shall find, as 

 already mentioned, that whereas the two latter have the 

 ordinary chisel- like rodent teeth, the former has several 

 narrow and somewhat irregularly- shaped teeth in the 

 front of the jaws, while its back teeth are crowned with 

 numerous sharp cusps, instead of having nearly smooth 

 grinding surfaces. Accordingly, from the purely systematic 

 point of view there is no justification for calling the 



