THE HEDGEHOGS HOLE. 57 



the survival of such lowly organised groups 

 in the presence of more highly evolved and 

 better-endowed races. In the first place, 

 these straggling survivors are generally found 

 in out-of-the-way places, far from the fierce 

 competition of great continents or of thickly 

 populated districts. Thus the ornithorhyn- 

 chus and the echidna, the two lowest mammals 

 or quasi-mammals, live in Australia, long 

 isolated from the Asiatic mainland, and with no 

 higher animals of any sort than the kangaroos. 

 The marsupials are similarly confined to the 

 Australian region, with the solitary exception 

 of the opossum. The edentates, another low 

 and early group, including the sloths and 

 armadilloes, belong to South America, for 

 ages a separate island, and only lately invaded 

 by higher types across the newly-raised 

 isthmus of Panama. The lemurs, lowest of 

 the monkey tribe, are almost confined to 

 Madagascar, as are also some other primitive 

 forms. Among the insectivores themselves, 

 the greater number belong to such places as 



