VITAL LIMIT OF EXSICCATION. 37 



percentage of water lost. Results of these experiments on the 

 vital limit of exsiccation are summarized in Tables I.-XII. 



Water Content Determination. 



It was thought hy the writer to be of interest to ascertain the 

 amount of water normally present in the species that were used in 

 the exsiccation experiments. The water content was determined 

 by drying the animals in a drying oven and weighing at intervals 

 until the weight became constant. The oven was kept at 99 C. 

 The percentage of water in relation to the body weight for sev- 

 eral species was as follows: meal worm (Tcnebrio nwlitor}, 49.8 

 per cent, (average of 60 individuals) ; leech (Placobdella para- 

 sitic a} , 76.4 per cent, (average of 10 individuals) ; house mouse 

 (Mus musculus), 70.8 per cent, (average of 7 individuals) ; frog 

 (Rana pipiens), 80.8 per cent, (average of 2 individuals). 

 Schmidt (1918) found the water content of the earthworm, Al- 

 lolobophora fcetida, to be 84.1 per cent, (an average of 13 individ- 

 uals). 



III. EXPERIMENTAL RESULTS. 



Earthworm. 



The species used in this experiment was the Allolobophora chlo- 

 roticus (Savigny). The worms were collected near Lake Men- 

 dota during the summer of 1919. They were placed between 

 moist filter paper in flat glass jars and kept for several days be- 

 fore using. They were rolled on dry filter paper in order to re- 

 move surface moisture and weighed in small flat dishes before 

 being subjected to exsiccation. Several individuals were exsic- 

 cated at a time. Individual worms were removed at intervals. 

 Directly following removal from the exsiccating chamber they 

 were placed on moist filter paper for recovery. 



When the worms were exsiccated they became contracted, as- 

 sumed a dark brown color, and lost all mobility. AS exsiccation 

 approached the vital limit the worms lost all elasticity of the body 

 and a mucus-like covering was secreted. It was found that 

 worms after exsiccation, if placed in a refrigerator at a tempera- 

 ture of 10 to 14 C., recovered after a greater loss of water than 

 those that were kept at ordinary room temperature. Perhaps 



