250 Merkel Henry Jacobs 



the body is thoroughly saturated with water, destructive metab- 

 oUsm would necessarily be far more rapid than in the cases men- 

 tioned. If death does not occur in the former case it would be 

 far less likely in the latter. The death of rotifers kept for four 

 days in a moist atmosphere, therefore, cannot be explained as 

 being due to destructive metabolism alone. It might be objected 

 that the process of drying in some way lowers the vitahty of the 

 animals so that they are more readily injured by changes of this 

 sort. That this is not the case is shown by the following experi- 

 ment. Thirty-nine rotifers were dried in the same way as those 

 used in the last mentioned experiments. The dish containing 

 them was then inverted over another dish of water in such a way 

 that the moisture could condense on it in small droplets. In this 

 way each rotifer became surrounded by a minute drop of water 

 which, however, in most cases was too small to permit creeping, 

 although allowing a certain amount of movement. They were 

 allowed to remain in this condition for four days, during which 

 time, of course, no food could have been obtained even though 

 feeding movements had been possible. When water was added, 

 all began to creep at once and seemed perfectly normal in every 

 respect. The experiment was repeated with twenty-eight rotifers 

 and again lOO per cent of the animals recovered, creeping move- 

 ments beginning almost immediately. It will be observed that 

 in these two cases the animals had been dried and by the addition 

 of a very small amount of water placed in conditions favorable to 

 metabolism. Although no food was present all of the animals 

 recovered. Of those dried in the same way and kept for the same 

 time at the same temperature with only so much water as they 

 could absorb from the air, only 38 per cent recovered— and this 

 was a somewhat higher percentage than was obtained in other 

 similar experiments. 



We have to deal, therefore, with an interesting condition. Roti- 

 fers dried and kept dry recover normally; those dried and placed 

 in a small quantity of free water do hkewise; those dried and kept 

 in an intermediate state are mostly killed. What is the cause of 

 this condition ? It we examine a rotifer that has been placed in a 

 moist atmosphere after being dried we find that although in appear- 



