220 



METABOLIC HORMONES 



(§ 5.322), since, like salt excretion (§ 5.312), it tends to dilute the 

 blood-salts (Table 25). Such hormones are well-established in 

 Arthropoda as well as in Vertebrata. In the latter, the hormones 

 tending to concentrate the blood come from the adrenal cortex, and 

 those tending to dilute it from the neurohypophysis, as they do for 

 the control of Na+ and CI" (Fig. 5-15). 



5.321 Decrease in cell permeability and diuresis leading to con- 

 centration of the blood 

 Crustacea. Water uptake is a normal accompaniment of moult- 

 ing, and probably plays a crucial part in helping to force off the old 

 cuticle. In the crayfish, Cajnbarus, eyestalk removal induces both 

 precocious moulting and abnormally great water uptake (from 23 



8 10 12 

 Time, days 



14 16 18 20 



Fig. 5-17. Percentage increase in water content (ordinates), as 

 measured by changes in body weight in the crayfish, Cambarus 

 immunis and C. propinquas, during 16 days (abscissae) after eye- 

 stalk removal. Black circles show values for one specimen with two 

 SINUS GLAND implants (curve A). This specimen shows less water 

 uptake than the mean for eight eyestalkless controls with no implants 

 (open circles, curve B). (From Scudamore, 1947). 



to 50 per cent of the body weight) during premoult ; but this can 

 be reduced again to about the normal level by implantation of two 

 SINUS GLANDS (Scudamore, 1947; Fig. 5-17). Opinions diflPer as to 

 whether eyestalk removal has a significant eflFect upon the water 



