262 G. T. CAI.mVKI.L. 



because of the impossibility to detect always the exact end- 

 points; in some instances the vari.it ion was as much as 2 per cent 

 and throughout the work the variation was greater with the 

 shorter respiration periods than with the longer. The animal 

 was then weighed and placed immediately into the respiration 

 chamber of the desiccator. The normal respiration time of the 

 control was determined and its weight recorded while the experi- 

 mental animal was being desiccated. This was repeated at 

 intervals, usually until the experimental animal showed no signs 

 of life. The intention was to obtain the rates of carbon dioxide 

 excretion at approximate stages of from 5 to 10 per cent, loss in 

 body weight. The time necessary for a loss in body weight of 

 about 10 per cent, was previously determined with animals of 

 similar weight. 



IV. EXPERIMENTAL RESULTS. l 

 A. Xerophilous Animals. 



Meal Worm, Larva of Tenebrio molitor Linn. These worms 

 were kept in the laboratory in open Mason jars partially filled 

 with air dried wheat bran. Five series of experiments were 

 performed. Three worms w r ere used in each experiment to reduce 

 the respiration time. The controls of four of the five series were 

 not fed. The controls of the fifth series were fed throughout the 

 experiment. The first readings were the most difficult to obtain 

 on account of the activity of the animals. A dark chamber was 

 the only means used to keep the animals quiet, although it was 

 found that animals placed with their bodies in contact with both 

 the bottom and side of the animal' chamber not only remained 

 quiet but also were less inclined to aggregate. After 10 hours in 

 the desiccator the meal worms were inactive when undisturbed. 

 In the first four series, carbon dioxide determinations were made 

 regularly at 24-hour intervals for six days. In the fifth series 

 determinations were made at shorter intervals. Evaporation 

 from the meal worm is very slow even in dry air. Hall (1922) 

 found that it required 1 ,084 hours to desiccate a meal worm to 

 52.6 per cent, of its body weight. While this loss was a greater 

 percentage of body weight than the average percentage of water 

 contained in the body, the worm lived two days after desiccation. 



1 Complete experimental data are on file in the University of Chicago Libraries. 



