BIOLOGY 



selves are not very abundant, and the creeping rotifers 

 have found a better home among the weed in the lakes. 



Among the mosses the animals lead even a harder life 

 than they do in the lakes. In the lakes, when they do 

 melt, the rotifers enjoy a period of some weeks when they 

 can move and feed and multiply. Among mosses they 

 feel at once the lowest temperatures of the air. They are 

 frozen during the greater part of the year. They are 

 frozen even in summer for the greater part of every day. 

 Only for a few hours daily, for a short time in the height 

 of summer, the moss is thawed by the sun's rays. One 

 wonders when the beasts get any time to grow. Yet they 

 are there in abundance. They are all of different kinds 

 from the lake dwellers. None of the rotifers were recog- 

 nised, but some of the water-bears were. 



Biological Problems 



By what means do the rotifers sur^dve freezing? It 

 is not, as with higher animals, that they can keep warm 

 in spite of the cold. They are too small for that. Their 

 very blood, as the watery fluid filMng the body cavity may 

 be called, freezes very soon after the surrounding water. 



Whence is the microscopic fauna derived? Are the 

 rotifers and water-bears survivors from the remote time 

 when a milder climate prevailed in Antarctica, when the 

 country was covered with a vegetation of the higher 

 plants and the coal-beds were in course of formation? Or 

 are they colonists from the temperate regions, which have 

 migrated across the stormy Antarctic Ocean under 

 present-day conditions? 



Some of the facts favour both theories. The small 

 number of species, and the fact that the majority of them 

 are widely distributed over the world, point to recent 

 immigration. 



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