Effects of Desiccation on the Rotifer 24I 



on the addition of water in five to seven minutes and creeping 

 individuals are sometimes observed in ten or fifteen. 



These experiments, therefore, seem to show that the rapidity 

 with which the first part of the drying occurs is of great importance 

 in determining the ultimate effect of the desiccation on the animal. 

 They also serve to explain the discrepancies that appear in the 

 accounts of various observers. Spallanzani, Pouchet, Davis, 

 Hudson, Leidy, Zacharias, Faggioli and others state very posi- 

 tively that a few hours drying on a clean slide is invariably fatal. 

 Doyere, on the other hand, is just as positive that such treatment 

 is not necessarily harmful. When we examine the accounts given 

 by these experimenters of their method of procedure we find that 

 Doyere dried his animals very slowly while the others did not take 

 this precaution, hence the disagreement in their results. 



When we compare rotifers dried slowly with those dried rapidly 

 we can see why the latter method of procedure should be injurious. 

 A rotifer dried slowly, although shrunken to a fraction of its former 

 size, preserves perfectly its original form and shows no irregular 

 wrinkles on the surface of the body. The body wall fits tightly 

 about the internal organs and the muscles adhere to it closely. 

 One dried rapidly, on the other hand, is very irregular in appear- 

 ance. The internal organs are more or less shrunken away from 

 the cuticle which itself is often very much distorted, and sometimes 

 has the appearance of an irregular gelatinous secretion. Fre- 

 quently when water is added it may be seen that some of the mus- 

 cles have been torn by the stresses set up by the rapidity of the dry- 

 ing and it is to be supposed that under these conditions the deli- 

 cate internal organs would also suffer greatly. The injurious 

 effect of the rapid drying therefore seems to be a mechanical one. 

 Even those individuals which are not permanently injured by the 

 first drying, since they are very susceptible to changes in moisture, 

 if kept exposed to ordinary atmospheric conditions would be far 

 more likely to be harmed than those which at the start contracted 

 into a compact and symmetrical mass. This may explain the 

 fact that rotifers dried without sand cannot be kept for such long 

 periods of time as those dried under more favorable conditions. 



