WATER EELATIOjSTS OF OTHER SPECIES 



143 



This variability is no greater than the frog's (see table 12), though 

 the turnover is almost twice as great. 



Negative increments of water are set up by evaporation from 

 worms placed in air ; positive increments by intraperitoneal injec- 

 tion of water. After each load has been established, the worms are 

 allowed to recover in fresh water (fig. 88). The control worms of 

 this series happened gradually to lose net weight ; in positive loads 

 the net loss is linear with time but slightly faster than in zero load. 

 In negative loads the net gain is at first very rapid, and far from 

 linear with time. 



-20 -10 ^10 



Total Water Load 



Fig. 89. Eates of total water exchange (% of BoAour) in relation to mean total 

 water load (% of Bo). Equilibration diagram of earthworm in fresh water at 18° C. 

 Each point represents 5 to 22 tests. Data were either in initial or later periods of 

 one hour. First it was ascertained that the total turnover is 2.7% of Bo/liour (Wolf, 

 '40a). Since in the turnovers later determined the output is 2.0%/hour greater than 

 the intake (fig. 88), 1.0%Aour is subtracted from all outputs and added to all intakes 

 on the right of zero load; and the abscissae are moved 1.0% to the left. New data of 

 Wolf and Adolph. 



Since total gain and total loss at diverse loads were measured in 

 the same individuals, a complete equilibration diagram is available 

 (fig. 89). In the initial hour, compensation of each deficit is eight 

 times as rapid as correction of equal excess. Most of the modifica- 

 tion is in the rate of intake through the skin. Like the frog's, this 

 gain does not diminish in excesses ; in excesses the small modifica- 

 tion of nephridial output alone allows slow recovery. 



The earthworm, as was said, recovers from water deficits chiefly 

 by faster intake through the skin. The rate of intake increases 



