Since this work began, 4, 679 samples have been tested, 250 being 

 classified as "toxic. " Thus far, 200 of these have been rechecked at concen- 

 trations ranging from 0.0001 to 0.04 p. p.m., and 88 continue to test toxic. 

 This reduction from 200 is an indication of the effect of the errors mentioned. 

 The major chemical groups involved and the minimum effective toxicity range 

 of the 88 compo\ands that continued to test toxic, are as follows: 



(The "total toxic" columns do not add up to give the "number of compounds 

 toxic at the level shown, " since sorae of the compounds tested contained 

 more than one group each. ) 



Samples are still being received for evaluation. However, their 

 incoming rate has decreased to a point where we will soon be in a position to 

 commence the second phase of our work. This will consist of checking the 

 selectivity of the more toxic samples. The method used will be somewhat 

 similar to that employed for determining the relative toxicity of the samples 

 of G. breve, in this case, however, the test organisms will consist of com- 

 mercially important species. The facilities of our recently completed re- 

 circulating sea-water system will be of great benefit to us in this particular 

 phase of the work because it will enable us to hold large numbers of com- 

 mercially important organisms. 



60 



