1923] Allen: Studies on Marine Diatoms and DmoflageUates 44:i 



light conditions for brown algae to be from five to twenty meters 

 below the surface, suggest the possibility that the influence of light 

 tends to best production of diatoms within those limits. Maximum 

 catches (average and individual) at twenty meters in 1922 at both 

 of our stations may indicate that the influence of light was not offset 

 by that of other factors to such an extent as to prevent it from 

 determining the maximum at or above the twenty meter level. 



Hydrographic observations in 1922, as in 1921, were made on a 

 plan somewhat different from that of the biological observations and 

 there is still no fully satisfactory basis of detailed comparison for the 

 results of the two types of studies. Inasmuch as salinities, specific 

 gravities, and other items of hydrographic record follow very much 

 the same trend of variation from day to day as that taken by tem- 

 perature, it seems to be sufficient for present purposes to confine atten- 

 tion mainly to temperature (figs. 3 and 4. Station I and Station II). 



"Whether it be direct or indirect, there seems to have been in 1922 

 some very definite connection between changes in temperature and 



