SEA-FISHERIES LABORATORY. 391 



Port Erin Bay. The sea-water as it flowed from the supply 

 pipe into the carboys was filtered through the finest bolting 

 silk used for tow-nets, so as to free it from all plankton, 

 although, as shown in our previous paper, this amount of 

 foodstuff would be small, and, as is also shown in our 

 previous paper, the total amount of organic carbon in 

 such filtered water is infinitesimally small and cannot 

 possibly exceed one milligram per litre. 



As the carboys were being filled, samples of the water 

 were taken for titration for oxygen and carbon-dioxide. 



The oxygen was determined by Winkler's method, 

 and the level of the carbon-dioxide content by titration 

 with centinormal acid, or alkali, in presence of phenol- 

 phthalein (4 drops in 100 c.c). These methods are 

 described and discussed in the former paper. The normal 

 figures did not vary much throughout the experiment, 

 the oxygen figure standing at about 8'8 milligrams of 

 oxygen per litre, and the sea-water requiring 2-3 c.c. of 

 N/100 acid per 100 c.c. to give neutrality to phenol- 

 phthalein. 



Similar titrations at the end of each interval for the 

 contents of the carboys gave figures from which oxygen 

 consumed and carbon-dioxide discharged by the animals 

 could be calculated. The carbon-dioxide titration is not 

 nearly so delicate as that for the oxygen, but still the close 

 correspondence in the total figures, for the long interval, 

 between oxygen used and carbon-dioxide evolved, shows 

 that on the whole there is little error in the titrations, 

 for the respiratory quotient in all four cases is practically 

 coincident with unity. The temperature was taken daily 

 throughout the period and varied from a maximum of 

 15° C. nearly at the beginning in August, to 11° C. about 

 the middle of September. 



In changing the water, the carboy was in each case 



