144 



PHYSIOLOGICAL EEGULATIONS 



many fold at deficits that do not even double the believed osmotic 

 pressure of the body fluids (Adolph, '27b, p. 56). Diminution of 

 water output through the usual channels contributes but a small 

 portion of the recovery from deficits ; in excesses it alone is avail- 

 able. In this there is no feature by which the annelid worm differs 

 from the frog or snake in its ability to compensate for unusual 

 water contents. 



§ 50. BiPALIUM 



Bipalium, a triclad turbellarian worm, is common in green- 

 houses where sources of water abound. Individuals weighing 0.3 

 to 2.4 gm. were desiccated by Kawaguti ( '32) and then placed in tap 



20 



-50 



-^o 



-30 -20 



Water Load 



-\0 



Fig. 90. Initial rate of water intake (% of Bo/hour) in relation to water load 

 (% of Bo). Gain was in first 1.0 hour. Worm Bipalium (triclad turbellarian), 6 in- 

 dividuals weighing about 1 gm. each, previously desiccated. On wet cotton at 30° C. 

 Data of Kawaguti ('32), 



water (fig. 90). No effect of body size is evident among the few 

 rates of exchange that he reported. An unusual feature is that the 

 velocity quotient (1/At) is greater at very low water contents (large 

 deficits) than in moderate ones. The course of the intake of water 

 is gradual, resembling the earthworm's, and apparently occurs 

 through the entire body surface. 



§ 51. Akbacia egg. Echinodeem eggs 



Unfertilized eggs of echinoderms furnish considerable informa- 

 tion about water exchanges. In the measurements of Lucke and 

 McCutcheon ('27) on sea-urchin Arbacia punctulata, eggs first 



