268 Adjustment to Conditions of Aquatic Life 



The water-fleas and many of our rotifers are hibernating 

 as winter eggs. The bryozoans and sponges are hiber- 

 nating as statoblasts. Doubtless many of the simpler 

 organisms whose ways are still unknown to us have their 



Fig. 167. Ceriodaphnia, molted skin and liberated ephippium 

 of the same individual shown in the preceding figure. This 

 photograph was taken only a few minutes after the other. 

 The female after molting immediately swam away. 



own times and seasons and modes of passing a period of 

 rest. It is doubtless due, also, to the ease and safety 

 with which they may be transported when in such 

 condition that they all have a wide distribution over the 

 face of the earth. In range, they are cosmopolitan. 



