PLANKTON DIATOMS OF THE GULF OF CALIFORNIA 



OBTAINED BY 

 ALLAN HANCOCK PACIFIC EXPEDITION OF 1937* 



(With 12 Plates) 

 E. E. Cupp and W. E. Allen 



Scripps Institution of Oceanography, University of California 

 La JoUa, California 



Our knowledge of biological conditions in the Gulf of California, 

 although still very limited, is being increased from time to time. Until 

 1937, only three series of phytoplankton samples had been collected in 

 the Gulf, one in 1921, between April 7 and July 11, by the Expedition 

 of the California Academy of Sciences (Allen, 1923) ; a second in 

 November, 1935, by the Templeton Crocker Expedition on the Zaca 

 (Allen, in press) ; and a third by the Allan Hancock Expedition of 

 1936, from February 8 to March 26 (Allen, 1937). A fourth series 

 of collections, to be discussed in the present paper, was made by the 

 Allan Hancock Expedition of 1937, between March 1 and April 4. 



In 1937, seventy-three phytoplankton samples were collected, seven 

 on the southward run in the open ocean from Point San Eugenio to 

 Cape San Lucas, sixty-six in the Gulf. (Map 1) Several catches were 

 collected farther north in the Gulf than any previous samples and more 

 were collected on the eastern side of the Gulf. Most of the collecting 

 was done on the northward run along the west side of the Gulf. In 

 1921, samples were collected as far north as Georges Bay; in 1936, to 

 the north end of Angel de la Guardia Island; and in 1935, only as 

 far as Topolobampo Bay. 



The method of collecting was the same as that used in 1936. A 

 measured quantity of water (13 liters for catches 1 to 35, 8 liters for 

 catches 36 to 73) was simply dipped from the surface and filtered 

 through a net of No. 25 silk bolting cloth (200 meshes to the inch). 

 A small quantity of formalin was used as the preservative. In the labora- 

 tory counting was done by use of a Sedgwick-Rafter counting cell. 

 Records were kept of cells in good condition and of cells in poor con- 

 dition. The designation "poor condition" was used to indicate cells 

 in which no chromatophores or chromatophore material remained. 



* Contributions of the Scripps Institution of Oceanography. New Series, No. 14. 



C 61 ] 



