142 



PHYSIOLOGICAL EEGULATIONS 



tents so as to equalize osmotic pressures between body and environ- 

 ment, for sooner or later animals like the teleosts and decapods are 

 studied that pump water, instead of (or as well as) pumping solute, 

 out of or into their bodies. 



§ 49. LUMBEICUS 



Earthworms live in an environment of earth mixed with fresh 

 water ; in the laboratory they are kept in water without earth. The 

 turnover of water is ascertained by the following steps : the worms 

 are handled until constant (basal) weight is attained, then left un- 

 touched for 1 to 5 hours ; reweighed, rehandled, and finally weighed. 



Hours 



Fig. 88. Course of water load (% of Bq) in earthworms immersed in fresh water 

 at 18° C. Each series consisted of 5 individuals just injected with water, or rendered 

 deficient by evaporation. Before each weighing, nephridial anl alimentary reservoirs 

 were emptied by rolling the worms repeatedly. New data of Wolf and Adolph, being 

 similar (in water deficits) to previous data of Wolf ('40a, his fig. 7). 



The loss of weight when rehandled represents a minimal value for 

 the water excreted in the period of time elapsed, the evidence being 

 that all of it is held in nephridial reservoirs and alimentary tract 

 while the worm is undisturbed. Nine-tenths of the fluid lost is 

 believed to issue through nephridia (Wolf, '40a) ; the total turnover 

 is 2.7% of Bo/hour. 



Variability of water content is about ± 2% of Bo, as ascertained 

 by weighing individuals at 24-hour intervals with reservoirs empty. 



