68 STUDIES IN ANIMAL LIFE. 



Never do these oval bodies become active crawling 

 Eotifers; never do they expand their wheels, and 

 set the oesophagus at work. No ; the Rotifer once 

 dried is dead, and dead forever. 



But if, like a cautious experimenter, you vary 

 and control the experiment, and beside the glass 

 slide place a watch-glass containing Rotifers with 

 dirt or moss, you will find that the addition of wa- 

 ter to the contents of the watch-glass will often (not 

 always) revive the animals. What you can not ef- 

 fect on a glass slide without dirt, or with very httle, 

 you easily effect in a watch-glass with dirt or moss ; 

 and if you give due attention you will find that in 

 each case the result depends upon the quantity of 

 the dirt. And this leads to a clear understanding 

 of the whole mystery ; this reconciles the conflict- 

 ing statements. The reason why Rotifers ever re- 

 vive is because they have not been dried — they 

 have not lost by evaporation that small quantity 

 of water which forms an integral constituerit of their 

 tissues ; and it is the presence of dirt or moss which 

 prevents this complete evaporation. No one, I sup- 

 pose, believes that the Rotifer actually revives after 

 once being dead. If it has a power of remaining in 

 a state of suspended animation, like that of a frozen 

 frog, it can do so only on the condition that its or- 

 ganism is not destroyed; and destroyed it would 

 be if the water were removed from its tissues ; for, 

 strange as it may seem, water is not an accessory, 

 but a constituent element of every tissue; and this 



