236 Merkel Henry 'Jacobs 



VII EFFECT OF DESICCATION ON THE LIFE PROCESSES OF 



PHILODINA 



It has been seen that recovery is possible in the case of rotifers 

 which have attained a considerable degree of desiccation. It 

 remains to consider in more detail the effect of this desiccation 

 on the hfe processes of the animal. Are the latter brought to a 

 complete standstill or are they merely retarded .^ Is the dried 

 rotifer dead or alive — or neither .^ Does the process of desicca- 

 tion have any injurious effects and if so what is the nature of these 

 effects .^ Questions such as these have occupied the attention of 

 physiologists for manyyears and in the following section an attempt 

 will be made to at least partially answer them. The last one — 

 having to do with the injurious effects of desiccation — will be con- 

 sidered first since it appears to throw some Hght on the others. 



I Injurious Effects of Desiccation 



It has been the testimony of practically all observers that desic- 

 cation is always more or less injurious. This is shown by the fact 

 that when large numbers of individuals are used some deaths 

 always occur, even under the most favorable conditions of drying, 

 and by the further fact that desiccation may not be repeated indefi- 

 nitely. Spallanzani was the first to observe the latter point. He 

 found that in certain rotifers experimented on by him all were 

 killed after the sixteenth drying. In the course of this work Spal- 

 lanzani's experiment was repeated with a small number of rotifers, 

 the latter being dried once a day with a small quantity of sand. 

 The following table shows the number of dead and alive on each 

 successive day: 



TABLE I 



Date Alive Dead 



December 31 n o 



January i 8 3 



January 2 5 ^ 



January 3 2 9 



January 4 2 9 



January 5 2 9 



