330 University of California Publications in Zoology [Vol.22 



INTRODUCTION 



Beginning in 1901 and continuing from that time to the present 

 under the active leadership of Dr. William B. Ritter, the San Diego 

 Marine Biological Station, succeeded by the Scripps Institution for 

 Biological Research of the University of California, has carried on 

 varied and extensive investigation of oceanic phenomena. Under the 

 pressure of explorational and other fundamental work little attention 

 was given to the ecological study of phytoplankton until 1917, when 

 the present writer was asked to develop the work along that line. The 

 report covering preliminary operations of 1917 and 1918 has been 

 published (Allen, 1921a) ; hence the present paper deals only with the 

 work of 1919 after the beginning of standardized operations at the 

 Scripps Institution. 



( hying partly to shortage of ecpiipment, no boat work was done 

 by the Scripps institution in 1919. As a consequence the collection 

 of phytoplankton was limited to such work as could be done at the 

 outer end of the pier, about 1000 feet from shore. Through the first 

 eight months of the year daily hauls were made with a tow net. 

 Efforts to make statistical studies of such material showed, however, 

 that it was not very satisfactory for that purpose. Hence it became 

 necessary to change the method of collecting which, after some experi- 

 ment, was done on September 1, 1919. 



The inadequacy of tow net catches was mainly clue to the fact that 

 at times in seasons of light production scarcely any phytoplankton 

 was taken by a standard run of the net. Enumeration of such catches 

 gave very little more information than was obtainable from casual 

 inspection, i.e.. that there was very light production of a very few 

 forms. But tow net catches were also very unsatisfactory because it 

 was impossible to say, even approximately, how much water had been 

 traversed or filtered. Hauls were made over a measured distance but 

 there was no way of knowing how strength and direction of currents, 

 quantity of plankton, viscosity of the water, and abundance of 

 sediment affected one catch as compared with another. For such 

 reasons it was derided to preserve the tow net catches for qualitative 

 reference and to confine quantitative studies to catches taken by the 

 changed method. In this way the scope of this report is limited to 

 the series of collections taken from the pier in the last four months 

 of 1919. 



