Effects of Desiccation on the Rotifer 225 



much wrinkled, the first change that occurs is a fiUing out of the 

 wrinkles, the amount of swelling apparently being slight since the 

 greater part of the shrinkage has occurred in the internal organs, 

 the cuticle having stuck fast to the slide or to a grain of sand. 

 That a considerable swelling occurs, however, is easily observed 

 when a group of rotifers has dried together, the individuals being 

 pushed apart as the water is absorbed. The usual time required 

 for all of the wrinkles to disappear is about five minutes, although 

 it may frequently be considerably less. 



The point at which the water enters may be determined by 

 staining rotifers intra vitam with neutral red before drying them 

 and then adding water which has been made weakly alkaline by 

 the addition of a small amount of sodium bicarbonate. As the 

 latter touches the organs which have been stained red it changes 

 them to a bright yellow color and thus furnishes a very exact 

 means of observing the method of penetration. Such an experi- 

 ment shows that the water enters largely at the two ends of the 

 animal and to a much less extent through the cuticle surrounding 

 the body. Its entrance is practically instantaneous. 



The time required for movements to appear varies greatly with 

 the circumstances attending the process of desiccation. The 

 times required under a number of different conditions are given 

 in another section of this paper. Under the most favorable con- 

 ditions they may appear in five minutes, as was the case with a 

 number of individuals which had been dried slowly on filter paper; 

 usually seven to ten minutes are required and sometimes an hour 

 or more. The first movements to appear are muscular contrac- 

 tions within the body, although sometimes the flame cells of the 

 nephridia begin to beat before muscular movements can be ob- 

 served. In any case the beginning of the activity of the nephridia 

 is one of the first signs of the return of the normal life processes. 

 Care must be taken not to confuse with true muscular movements 

 the jerky movements exhibited immediately after water has been 

 applied which are due only to changes in tension set up by the 

 imbibition of the water and are not indicative of life. In all cases 

 where the time required for movements to appear is mentioned it 

 is understood that it is the distinctively vital movements that are 

 meant. Soon after the first movements have appeared the foot 



