478 Trans. Acad. Sci. of St. Louis. 



irregularities are regrettably large, so that it is difficult to 

 compute an average. In fact, from a microscopic study of 

 the effect of such a solution on Pleonosporium, it was found 

 that if the concentration were very gradually increased with 

 this particular alga plasmolysis was a very evanescent phe- 

 nomenon. It would often happen that on approaching the 

 critical concentration the observation would show only tempor- 

 ary plasmolysis in a few of the many cells under observation. 

 The point of plasmolysis in such cases was soon passed, and 

 death of the cell quickly resulted, as shown by the diffusion 

 of color. 



The results obtained by the tests above outlined made it 

 seem desirable that studies should be directed toward a com- 

 prehensive knowledge of the possibly toxic action on 

 marine algae of certain of the constituent salts of sea water 

 when added to sea water. (A further study also, of the 

 permeability of the protoplasmic membranes to diverse solu- 

 tions was evidently important, but the latter has not yet re- 

 ceived further consideration.) 



A series of experiments was accordingly set up. At that 

 time practically no experiments bearing upon this general 

 matter had been reported, so far as could be ascertained. 

 More recently some data from the plant side as well as the 

 animal side have accumulated. A further study also of 

 the permeability of the protoplasmic membrane to diverse 

 solutions is important. 



TOXIC STUDIES. 



Materials and Methods. — After considerable experimenta- 

 tion, in order to get desirable forms for the determination of 

 the toxic relations, Daaya elegans^ Grinnellia Americana and 

 Cladophora gracilis were employed in the work at Woods 

 Hole. At Cette the season was unfavorable for any great 

 selection and favorable algae which could be necured in best 

 condition were used, these being Bryopsis plumoaa Callitham- 

 nion roseum^ Ceramium sp., and JVitophyllum punctatum. 

 Many algae are not suitable for studies of this nature. In 



