224 Merkel Henry Jacobs 



from the latter. Although the animal is not necessarily injured 

 by this irregular shrinking it is more hkely to be than in the case 

 where it contracts regularly. 



Loss of water from the body is very rapid after the last trace of 

 the surrounding film has disappeared. Wrinkles appear almost 

 immediately in the case of individuals dried on a clean slide. In 

 one minute the body may have become fairly irregular in outline 

 and in two minutes assumed the characteristic appearance of desic- 

 cation. Although further loss of water and shrinkage occur the 

 change in size and appearance after two or three minutes is not 

 very noticeable since the cuticle has assumed its final wrinkled 

 form and further contraction is confined to the internal organs. 

 In rotifers dried more slowly the contraction is more evident since 

 the cuticle and hypodermis are pressed together against the inter- 

 nal organs and follow them in their shrinkage. That muscular 

 action is responsible for at least a part of the contraction is shown 

 by the fact that dead rotifers when allowed to dry assume very 

 irregular forms, the closing of the ends of the body above described 

 not occurring. 



The amount of shrinkage that occurs under favorable conditions 

 is very considerable. It may easily be followed by keeping single 

 individuals under the microscope during the drying process and 

 making camera drawings of them from time to time. In those 

 that are dried slowly and thus contract regularly it is easy to com- 

 pare approximately the volumes at the different times. Such an 

 examination shows that in the case of slow desiccation with sand, 

 which is one of the most favorable methods, the animal may shrink 

 to one-third or one-fourth of its original volume. 



When water is added to rotifers that have been dried for a time 

 a very rapid swelling occurs. In one minute the animal has dou- 

 bled in volume and in five or often less has reached its normal size. 

 From this time until movements appear the visible changes are 

 slight and consist in changes of form apparently due to the slow 

 relaxation of the muscles that have drawn in the ends of the body. 

 When those at the anterior end relax the animal becomes pear 

 shaped; the foot may be extended either before or after this occurs. 

 In rotifers which have been dried rapidly and which are therefore 



