give a fair idea of the numbers present outside ; but the results 

 give a fairly satisfactory idea of the relative quantities of the 

 species which get into the tanks, as the curves correspond in 

 general shape to those of other investigators. The numbers they 

 represent are too high, however, although such a condition is very 

 desirable for the purposes for which the tank water is used 

 ordinarily. 



The method used could no doubt be adapted satisfactorily 

 for determining the depths at which various species of diatoms 

 occur normally when undisturbed by storms, and far enough 

 from the shore to be unaffected bv breakers^ 



