We conclude from these experiments that in running sea water a 

 toxic effect beoanes apparent after 48 hours if 5 ml. or more of oil 

 mixed with sand are placed in the immediate vicinity of Tubularia . 



4, Relative toxicity of different types of oil in standing water } 



Samples of oil received from the Navy for testing comprised the 

 following types t crude oil. Navy Grade Special fuel oil, lubricating 

 oil (SAE 20), and Diesel oil. In conducting the test, 5 ml. of each 

 of these oils, with a sufficient amount of carbonized seuad to anchor 

 them, were placed on the bottom of each of four finger bowls containing 

 200 ml. of sea water. One finger bowl of the same size and capacity 

 served as a control. The test was continued for 25 hours, during which 

 time the number of remaining live hydranths was counted at the 6th, 17th, 

 and 25th hour. The results, summarized in table 11, show that lubricating 

 oil was least toxic, while crude oil appeared to be the most toxic. 

 There was considerable mortality in the control (27 out of 50) but the 

 loss of hydranths in the water contaminated with oil was much greater, 

 with ttie exception of that iriih the lubricating oil, 



EXPERIMENTS WITH BARNACLES, BALANUS BALANOIDES (Ag.) 



Among the common invertebrates of the inshore region, barnacles 

 occupy a prcminent position as one of the principal fouling organisms, 

 attaching themselves to ship bottoms and covering the shells used by 

 oystermen as cultch for the catching of oyster spat. Many toxicologioal 

 studies have been conducted with the view of combating fouling by pre- 

 venting, or at least minimizing, the attachment and growth of barnacle 

 larvae. The adult orgarism also can be conveniently used in toxico- 

 logioal tests. Being sessile, the barnacles can be easily arranged in 

 a desired position in the experimental set-up. The effect of a toxio 

 substance can be studied by observing and timing the sweeping of their 

 oirri. 



Keeping the barnacles in the laboratory presents no difficulty. 

 In running sea water or in containers in idiich the water is renewed 

 daily, they remain active and apparently in good condition for many 

 days and weeks. 



In Hie present experiments, specimens of Balanus balanoides 

 growing on rocks were obtained from Woods Hole Barbor close to the 

 low tide mark. Stones with 25 to 50 individuals were placed in finger 

 bowls containing 250 ml. of sea water. One finger bowl served as 

 control, while to each of three others were added 5 ml., 10 ml., and 20 ml. 

 of crude oil mixed with carbonized sand in quantities sufficient to 

 anchor the oil on the bottcm. It was found that the water in the 

 control bowl was rapidly fouled by abundant discharge of fecal material. 

 TMs was not the case, however, in the experimental containers in which 



17 



