122 THE WONDER OF LIFE 



of woods and forests, of moors and meadows, of links and 

 dunes — each with its characteristic fauna and flora. There 

 are pecuhar regions like steppes and prairies, tundra and 

 desert, and the circum-polar areas so far as these can be 

 called terrestrial. 



Under Ground. — It is interesting to think of the large 

 number of animals that have taken to a subterranean 

 mode of life as burrowers in the ground. There must have 

 been long ago a golden age for the race of earthworms 

 when they discovered the possibility of colonizing a new 

 world below the surface. Ages probably passed before 

 they were followed by the Centipedes who are their invet- 

 erate enemies, by some of the burrowing beetles, and by 

 carnivorous slugs (Testacella). Long ages passed before 

 the moles followed the earthworms into the recesses of 

 the soil, and became equally well adapted to the pecuUar 

 conditions of that strange mode of Ufe. 



Over and over again the same story has been re-enacted, 

 e.g. by burrowing amphibians (Csecilians), burrowing 

 Uzards (Amphisbaenids), and biirrowing snakes (Typhlops, 

 etc.) : a temporary safety has been secured by a change 

 of habitat, and then new enemies and difficulties have been 

 encountered. 



Cave Animals. — Caves and grottos have come to be 

 tenanted by a diverse array of animals, more or less adapted 

 to the conditions of life — darkness and constant temperature, 

 absence of green plants, and a humid atmosphere, for 

 thoroughly dry caves have never more than casual tenants. 

 The cave-fauna includes many bats, a few peculiar mice, 

 the Amphibian Proteus of the great caves of Carniola and 

 Dalmatia, and three American salamanders, a good many 

 small fishes, numerous beetles and a few other kinds of 



