1923] Allen: Studies on Marine Diatoms and Dino flagellates 445 



the difference in temperature between the surface and the other two 

 levels is much greater than the fluctuations at any level during the 

 period of collecting yet most of the species seemed to thrive at all 

 levels even when their optimum was indicated at one. With such 

 points in mind it seems possible, if not probable, that the lower 

 temperatures from June 11 to June 22 at Stations I and II and at 

 the pier indicate an extensive drift movement of water rather than 

 an upwelling, such as we have usually assumed to be responsible for 

 lowered temperatures. If local upwelling were responsible, the tem- 

 peratures at twenty meters and forty meters ought to be much more 

 nearly the same than usual and the surface should show less difference 

 from the other two. Presumably, also, local upwelling should force 

 the main diatom population close to the surface. 



Chemical records are still insufficient to attempt to trace the 

 influence of given chemical factors upon distribution of the micro- 

 plankton population. In the case of hydrogen ion concentration, 

 for example, it is practically impossible to say to what degree its 

 fluctuation in this period is due to temperature, to flow of currents, 

 to upwelling, or to fluctuations in the numbers and activities of 

 photosynthetic and nonsynthetic organisms, or to what degree it 

 influences fluctuations of other factors of the ecologic complex. 



CONCLUSION 



The conclusions stated for 1921 (Allen, 1923, p. 79) hold equally 

 well for 1922. It may be worth while to note that the similarities 

 of the records of collections from the three levels convincingly indi- 

 cate that the methods employed are correct. 



LITERATURE CITED 

 Allen, W. E. 



1923. Studies on catches of marine phytoplankton made by aid of the Kofoid 

 bucket in 1921. Ecology, 4, 74-80. 

 Shelford, V. E., and Gail, F. W. 



1922. A study of light penetration into sea water made with the Kunz photo- 

 electric cell with particular reference to the distribution of plants. 

 Publ. Puget Sound Biological Station, 3, 141-176. 



