240 



Merkel Henry 'Jacobs 



is not the case as the above figures show. The difference between 

 the effects of drying with a small quantity of sand and with none 

 at all is usually not so great as would appear from the table, 

 since in the first experiment the mortality is unusually high. As 

 a rule, almost the same result is obtained in the two cases. 



The effect of the rapidity of drying is brought out in a striking 

 manner in the following experiment. Two lots of rotifers from 

 the same culture were dried at the same time at room temperature, 

 the one in a calcium chloride desiccator and the other in a partly 

 covered dish containing a piece of moist filter paper. In the first 

 dish the drying required twenty-five minutes; in the second about 

 twelve hours. The drops of water in the two cases were as 

 nearly the same size as possible and neither contained any sand. 

 After the drying had taken place both were kept for three days 

 in the desiccator, attaining presumably the same degree of dryness. 



TABLE IV 



E^ect of rapidity of drying 



It is seen from these figures that by allowing the drying to pro- 

 ceed slowly enough a large percentage of the rotifers may recover 

 even when dried for several days in a perfectly clean glass dish. 

 This result is opposed to most of the observations that have been 

 made and is not in accord with Davis' theory. It must also be 

 noticed that even where the drying was extremely rapid a certain 

 number recovered when by using a covered dish rather than an 

 ordinary slide they could be kept a sufficiently long time after the 

 application of water. 



Any method of retarding evaporation seems to have the same 

 effect. Rotifers dried on small pieces of filter paper in which 

 evaporation is necessarily slow may be preserved in good condi- 

 tion for very long periods. Even after a month movements appear 



