1923] Allen: Studies on Marine Diatoms and Dinoflagellates 439 



somewhat confused by the fact that average numbers at twenty meters 

 at Station I were much greater than average numbers at the surface 

 at Station II (table 1). 



In 1921 it was noted (Allen, 1923, p. 77) that greater numbers 

 of species were recorded at the twenty meter levels than at the surface. 

 In May -June, 1922, the number of species of diatoms at Station I 



STATION 2 • 



AVay - June 1922 

 Graph ho short hofdrihhms of numbers 



per lire>r of dial-oms in fCofoid buckeh ca/chos 



Surface ca/chos 



20 meher catches 



4-0 meter ca/ches o ooco<,o„oooo» 



r 



f hi i in n ii i n 1 1 i . 



I llll III III! II III III ili.iilii 



was nearly the same at all three levels, but the number was greatest 

 at twenty meters at Station II. In September the number of species 

 of diatoms was greatest at the forty meter level at both stations. 

 The number of species of dinoflagellates was greatest at the surface 

 at both stations in May-Jiuie and at Station II in September. The 

 limited evidence of the two seasons shows a tendency of the larger 

 number of species of diatoms to stay some distance below the surface 

 while the larger number of species of planktonic dinoflagellates tend 

 to remain at or near the surface. In considering this matter of dis- 



