THE HEDGEHOGS HOLE. 59 



without leaving a very false impression as to 

 these outcasts of animal life. Though they 

 all represent low and little developed types, 

 they are yet as a rule highly specialised 

 representatives of those types. They have 

 survived because they could fill some vacant 

 place or other : and for that place they have 

 become fully specialised. Thus, though the 

 brain, the skeleton, and the other organs of 

 an ornithorhynchus or an echidna are lowly 

 and poor, as judged by a general mammalian 

 standard, yet their external form is very much 

 more specialised than the external form of the 

 primitive mammal could possibly have been. 

 He could not have had the broad duck-bill, 

 the webbed feet, the burrowing and water- 

 haunting adaptations of the ornithorhynchus 

 on the one hand, nor the spiny coat and 

 curious digging paws of the echidna on the 

 other. So with the insectivores. The 

 hedgehog represents the primitive insecti- 

 vorous type, plus the familiar sharp prickles, 

 which exactly recall those of the echidna : 



