234 Merkel Henry 'Jacobs 



time for moisture to be absorbed from the atmosphere. That only 

 a small amount of water is sufficient to give the appearance he 

 describes may be proved by pressing under a cover glass small 

 shreds of filter paper or pieces of apparently dry plant tissues. 

 There is also a possibility that what Davis imagined to be water 

 was only a thin film of air which under certain conditions arising 

 in microscopic work closely resembles water. 



The fact that desiccation is often very complete may be shown 

 by chemical means as in the following experiment. A number of 

 rotifers, stained intra vitam with neutral red, were allowed to dry 

 under the most favorable conditions possible and were then placed 

 in a desiccator over night. One lot was moistened and found to 

 be normal in every respect. A second lot was exposed to ammonia 

 fumes rendered as dry as possible by means of calcium chloride 

 and a third lot exposed to the same fumes after having been allowed 

 to remain in a moist atmosphere for five minutes. The third 

 lot changed color from red to yellow almost instantly; the second 

 lot retained their red color. That the effect in the latter case was 

 not due to the inabihty of the ammonia to penetrate the cuticle 

 was shown by the fact that a number of the rotifers which had been 

 purposely crushed also retained their color. The failure of the 

 characteristic reaction between ammonia and neutral red in the 

 case of rotifers dried in a desiccator must be considered to indicate 

 that they retain very little water. 



There is also much indirect evidence that the desiccation is a 

 real one. Some of this evidence will be mentioned later but it 

 may not be out of place to refer at this point to the resistance shown 

 by dried rotifers to high temperatures. Gavarret and others have 

 found that rotifers in water are killed by a temperature of 51° C, 

 giving all the evidences of heat coagulation. When partially 

 dried and in a moist atmosphere they are killed at 81° C. and after 

 thorough drying they may resist temperatures of ioo°-iio° C. 

 Doyere even found a rotifer which after being dried in the sun for 

 several weeks was not killed by a very short exposure to 153° C. 

 How can such results be explained on Davis' theory that the body 

 fluids are retained within a watertight cyst .^ Does the protoplasm 

 at the time of the formation of this cyst undergo some mysterious 



