the water remained clear, presumably because the presence of oil depressed 

 the functioning of the intestinal tract of barnacles. TO avoid undesirable 

 effects, the water in the control was renewed daily. 



The oil and carboniced ssind mixture in the water had pronounced effect 

 on the behavior of the barnacles. At first their cirri continued to beat 

 at the normal rate. As the exposure in oil-contaminated water continued, 

 there was a slowing of the beat and a reduction in the extent of each 

 sweep. With the progress of poisoning, both the rate and the extent of 

 sweep were further reduced until the test animals came to rest and stopped 

 their movement, the cirri half extended. In contrast, the control barnacles, 

 when coming to rest, were tightly closed with the cirri completely with- 

 drawn. At the earlier stage of poisoning, the barnacles would respond to 

 touch by withdrawing their cirri eoid closing their shells. The reaction 

 ceased as the eoiimals succumbed to the poison. This effect of oil on the 

 behavior of barnacles is similar to that of other poisons which were 

 studied by Clarke (1947). During the 70 hours of observations there was 

 no change in the behavior and no death among the control barnacles. In 

 ■tile oil-contaminated water the first symptons of poisoning, shown by 

 slowing down of the sweeping of the cirri, became apparent after six hours 

 of exposure. The poisoning progressed in proportion to the concentration 

 of oil, all the barnacles passing through the same stages characterized 

 by incomplete sweep of cirri, opening of shells, failure to react to touch, 

 and death (table 12). 



The test very clearly demonstrates the toxic effect of crude oil and 

 sand mixtures placed in the immediate vicinity of barnacles. 



EXPERIMEITTS WITH TOADFISH EMBRYOS, OPSANUS _mu LINN 



Toadfish embryos present excellent material forbioassay; they are 

 large, fairly transparent, and are attached by egg membranes to pieces 

 of wood, stone, shells, and similar objects. They can be easily handled 

 in the laboratory without being injured. The fish itself, a very ccxnmon 

 bottom dweller along the coast of North America south of Cape Cod, is 

 hardy and resistant to unfavorable environment. Around Woods Hole the 

 eggs are laid early in May and may be found until the middle of July. 

 They can be kept in good condition in the laboratory tanks in running 

 sea water if care is exercised in removing dead or dying eggs. After 

 hatching, the larvae still remain attached to the substratian by their 

 yolk sacs. At this stage they somewhat resemble tadpoles eaid exhibit 

 actiye movements of their tails and gills. The beating of their hearts 

 and the circulation of blood can be easily observed with adequate 

 illiuai nation 8md suitable optical equipment* 



For the test we used larvae from 8 mm. to 10 mm. long which were 

 detached from the substratum and placed on the bottom of finger bowls 

 together with known quantities of oil and sand mixtures. The embryos. 



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