EFFECT OF ORGANIC SUBSTANCES ON OYSTERS 



175 





Figure 7. — Relation between activity of oysters and variations in carbohydrate concentrations at two temperature 

 ranges. Upper figure at temperatures approximating 25° C, lower figure approximating 27 C; salinity ranges 17° 

 to 20%o The carbohydrate threshold for the oyster at 25° C. (upper figure) apparently approximates 6 mg./l. 

 Testing periods are shown as intervals A and B, phase III as C and D. Lower figure (27 C.) shows four similar 

 testing periods A, B, C, and D; on the fifth test, E, the carbohydrate concentration had increased sufficiently to 

 induce phase-Ill pumping, interval F. This oyster, at the higher temperature, apparently had a much higher 

 threshold level (approximating 12 mg./l.) than that of the oyster at 25° C. Reproductions of actual records. Paper 

 speed 2 inches an hour; vertical lines at quarter-hour intervals. 



