356 



ANIMALS IN INLAND WATERS 



located in places which are exposed to the scorching sun's rays during 

 the day and to extreme cooling by night. These changes can easily 

 be endured without damage by the animal inhabitants while they are 

 in a latent condition, for then they possess very remarkable resist- 

 ance against high or low temperatures; they have been seen to revive 



Fig. 104.— Tardigrades from moss: left to right, Macrobiotus; Milnesium; 



Echiniscus. After Richters. 



in mosses which had been heated to a temperature of 80°, some even 

 to 150°, or had been cooled in liquid helium to — 272°. 97 



The moss fauna is surprising in its cosmopolitan composition. 

 The slight weight of the dried-up animals favors their distribution 



S*& 



& 





4i 



Fig. 105. — Eggs of tardigrades: left. Macrobiotus granulatus; right, M. coronifer. 



After Richters. 





by the wind. Close selection by unfavorable environmental factors 

 prevents the competition of other local animals with the moss animals. 

 Some of these animals have a very wide horizontal and vertical dis- 

 tribution. Seven of twelve antarctic rotifers (Bdelloidea) have been 

 found elsewhere. Most of the Tardigrada which were brought back 



