Effects of Desiccation on the Rotifer 261 



2 The tissues of the body become truly desiccated, as is shown 

 by the amount of shrinkage that occurs, by physical and chemical 

 tests for water, and by other more indirect methods. The desic- 

 cation, however, must not be considered an absolute one, it being 

 impossible to remove the last traces of water at ordinary tempera- 

 tures. 



3 The cuticle of Philodina under all conditions of desiccation 

 is freely permeable to water vapor and gases. No evidence of a 

 waterproof cyst can be found. 



4 The presence of sand, etc., is not necessary that recovery 

 shall occur as many have claimed. By proper conditions of dry- 

 ing almost all of the individuals recover after a desiccation of at 

 least four days in the absence of all sohd matter whatever. 



5 The process of drying is always more or less injurious under 

 any conditions, as is shown by the fact that some deaths almost 

 always occur and that it may not be repeated indefinitely. 



6 The chances of recovery of a given individual depend on 

 its previous condition as well as on the circumstances under 

 which drying occurs. 



7 The rapidity of the drying process has a very important 

 effect on the mortahty, rapid drying being more injurious than 

 slow drying. It is apparently immaterial by what means the 

 process of drying is slowed. 



8 The injurious effect of rapid drying seems to be due to 

 mechanical injuries to the vital organs and the cells composing 

 them caused by the rapid extraction of water. 



9 The final intensity of the desiccation makes little differ- 

 ence in the mortality provided it be attained gradually enough. 



10 Other things being equal, a fairly high temperature at the 

 time of drying is favorable, a low one unfavorable. 



11 Alternations of moisture and dryness are very injurious. 



12 Rotifers kept at a high temperature show a greater mor- 

 tality than those kept at a low one. 



13 Rotifers kept in a moist atmosphere show a greater mor- 

 tality than those kept in a dry one. 



14 MetaboHc changes in the tissues probably continue in 

 dried rotifers though very much retarded. The functions of the 

 various organs as such are suspended. 



