A mixture was prepared of 100 ml. of crude oil and a Quantity 

 of carbonized sand siifficient to remove all the oil from the surface 

 and submerge it. The mixture was then placed on the bottom of a 

 five liter tray containing experimental 03reters» The resultant ratio 

 was equivalent to 1 part of oil to 50 parts of sea water. A marked 

 depression in the rate of cloacal current (figure 9) indicates the 

 effect caused by a gradual release of the physiologically active 

 materials. By the end of the third hour aTter the introduction of 

 the mixture, the rate of current produced by the oyster was still 

 declining, while in the control oyster it was gradually increasing. 



In another experiment we tested a water extract prepared from an 

 oil and sand mixture. In this case 200 ml. of oil combined with 

 sufficient amount of sand were shaken for six hours in four liters of 

 sea water. A solution containing 50 percent of this extract in sea 

 water greatly depressed the rate of current (figure 10). 



From these experiments we conclude that anchoring of oil by 



carbonized sand does not prevent the release of physiologically active 



substances which depress the activity of the ciliated epithelium of the 

 gills of the oyster. 



b. Effects on the rate of pumping of water by the intact oyster 

 (apron method) : 



The apron method for measuring the rate of pumping of water by 

 oysters presents several advantages that are lacking in the cannine 

 oono technique. With the latter, the functioning of the adductor muscle 

 and the mantle of the oyster is prevented by the inserting of a glass 

 rod between the valves and the introducing of a rubber tube into the 

 cloaca. In the apron method the rate of pumping of the intact oyster 

 is measxa"ed. Partial wrapping of the oyster in thin rubber dem to 

 channel the cloacal current is the only deviation from a normal 

 condition. The functioning of the internal orgsins is not in any way 

 affected by this arrangement and, since the adductor muscle and the 

 mantle continue to react normally, there is no interference witii the 

 spontaneous movements of the shell, important for the well being of 

 the oyster. Thousands of observations made in our and other labora- 

 tories since the apron technique was suggested by Thurlow Nelson (1936) 

 show that this experimental prooedvire does not interfere with the normal 

 behavior of the oyster. In the vrork conducted by us since 1935, first 

 at the laboratory at Yorktown, Virginia (Galtsoff et al., 1947), and at 

 Woods Hole, Massachusetts, in connection with our studies on respiration, 

 we have accumulated several thousand records of oyster activities under 

 normal and altered conditions and found that oysters wrapped in the rubber 

 apron according to Nelson's method and kept in sea water naming freely 

 through Galtsoff »s constant- level tanks (Galtsoff, 1926) suffer no ill 

 effects. Using this method we have been able to obtain uninterrupted 

 records of shell movement and of rate of pumping of water by the oyster 

 kept under observation for fortnight periods and longer. The complexity 



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