Effects of Desiccation on the Rotifer 213 



niable fact that rotifers, tardigrades, and anguillulids may be 

 obtained from apparently dry sand they explained in different 

 ways. Ehrenberg, on the one hand, contended that actual dry- 

 ing does not occur, the sand protecting them from loss of water 

 "as a woolen mantle protects the Arab from the intense heat of 

 the desert." He beUeved that in this state of apparent desicca- 

 tion all of the vital processes continued, even reproduction. Bory 

 St. Vincent, on the other hand, believed that the animals in ques- 

 tion could not survive a period of drying even when sand was 

 present and that their apparent revival was due to the hatching 

 of eggs concealed in the sand. "Nous avons quelquefois * * * 

 retrouve des Rotiferes * * * mais ils n'y ressuscitaient pas; 

 ils s'y developpaient comme les Daphnies et autres petits ento- 

 mostraces, dont les ovules sont demures dans le sol." 



The next worker to take up the subject in a scientific manner was 

 the French naturahst Doyere. So great was the authority of Ehren- 

 berg and Bory St. Vincent and so plausibletheir reasoning that he 

 had been led to doubt the accuracy of Spallanzani's observations or 

 at least to regard the matter as worthy of further investigation. He 

 accordingly undertook a series of experiments, published in 1842, 

 with the result that Spallanzani's conclusions were in the main 

 confirmed. He found, however, that the animals are not always 

 killed in the absence of sand, a certain proportion of those dried 

 on a clean slide recovering, although requiring a much longer time. 

 Furthermore, he showed that it is not the exposure to the air that 

 injures the rotifers and tardigrades in this case as Spallanzani 

 had supposed, since animals dried in the air and then placed in a 

 vacuum showed a lower mortahty than those dried directly in the 

 vacuum. He concluded that the rapidity of drying is an important 

 factor in the effect of the desiccation. He furthermore showed 

 that rotifers may be revived after an apparently almost perfect 

 desiccation. He found that they could endure a sojourn of 17 

 days in a desiccator followed by 28 days in an air pump with a 

 pressure of 5-6 centimeters of mercury and that after thorough 

 drying in the sunhght a temperature of 140° C. or more could be 

 resisted for a brief period. He concluded, therefore, that the last 

 traces of water might be extracted without destroying the power 



