five animals, Tubularia was the most sensitive, while the hard shell 

 clam was apparently the most resistant of the group. 



EXPERIMENTS WITH TUBULARIA CROCEA 



colonies of Tubularia orocea were collected in the vicinity of the 

 Cape Cod Canal and, after being brought to the laboratory, were immediately 

 placed in running sea water. Pieces of the colonies having a readily 

 countable number of hydranths were cut with sharp scissors 8aid placed in 

 finger bowls or in experimental dishes. Inasmuch as preliminary experi- 

 ments have shown that Tubularia cannot be kept in the laboratory for more 

 than a week, all the tests were completed within one or two days. Weakened 

 or dying polyps of Tubularia lose their dark pink color and become slightly 

 opacfue. Their tentacles fail to respond to touch and, finally, the entire 

 hydramth, with its whorl of filliform tentacles, separates and drops off, 

 leaving dense tufts of tangled stems. This characteristic change makes it 

 convenient to employ colonies of Tubularia as test animals. The death 

 point of an individual hydranth may be taken as the time when it drops off 

 the stem and the progress of mortality in the group can be easily expressed 

 in the number of lost hydranths. 



The tests made with Tubularia consisted in determining the survival 

 of this organism in standing or in running sea water containing known 

 cfuantitie» of mixtures of various oils and carbonized sand, and in its 

 survival in water to which an extinct of orude oil was added. 



1. Effect of oil and carbonixed sand mixture in standing water ; 



In these experiments, the concentration of the substances presumably 

 released frcm oil and sand mixtures was allowed to build up in steuiding 

 water. The Tubularia were placed in 200 ml. of laboratory sea water in 

 finger bowls, and the specified amount of oil combined with sand was placed 

 on the bottom of each bowl in such a way that no hydranth was in direct 

 contact with the mixture. The water was not agitated or aerated. Since 

 there was no visible oil slick on the surface of water, the gaseous ex- 

 change over the surface of water was not impeded. 



The ratios of oil to sea water varied from 1:20 to 1:1,000. The 

 results of four separate tests, summarized in tables 2 to 5, show 

 different degrees of toxicity, depending on the quantity of oil used. 

 In high concentrations of 1:20 emd 1:40, nearly all the hydranths perished 

 within twenty-four hours. In the weakest concentration of 1:1,000 

 (table 3), 17 hydranths out of 50 died within one day, while in the 

 control, only 5 out of 60 succumbed during this time. Some mortality of 

 hydranths in the control dishes occurred in all the tests, but the number 

 of dead was much smaller than that among the Tubularia exposed to oil. 

 From the results of these tests we conclude that under the conditions of 

 the experiments sufficient quantities of toxic material were leached from 

 oil and sand mixtures to have a marked deleterious effect on Tubularia. 



6 



