1923] Allen: Studies on Marine Diatoms and Dmo flagellates 441 



(over 1,000,000 to the liter at Station I, twenty meters, on June 20; 

 over 300,000 at Station II, twenty meters, on June 19, followed by 

 over 200,000 on June 20; and over 58,000 at Station II, forty meters, 

 on June .19, followed by over 20,000 on June 20). This diatom is 

 very easily recognized, so that there is no question as to its identity. 

 On June 21, in a non-serial catch from the twenty-five meter level 

 at the entrance to San Diego Bay, this species was found in numbers 

 of about 2,720,000 cells to the liter. 



The six other species which deserve mention were Chaetoceras 

 decipiens CI., prominent at the surface only at both stations, Dactylio- 

 solen tenuis CL, at forty meters only at Station I, Lauderia borealis 

 Gran., at forty meters at Station II in September only, Skeletonema 

 costatum Grev., at forty meters, Station I, in September only, Thalas- 

 siothrix acuta Karst., at the surface, Station I, only in May-June, 

 and Thalassiosira subtilis (?) Ostf., at forty meters, Station I, only 

 in May-June. 



Five of the ten species mentioned above had somewhat similar 

 prominence in June-July, 1921, but Chaetoceras scolopendra CL, 

 which then was first at twenty meters at Station I, was not among 

 the first five in any case in 1922. 



At two different times surface catches were taken at a point 

 fifteen miles seaward from the pier. In both cases the catches were 

 smaller than they were on the same days at the ten mile station. 

 Occasionally surface catches were taken at points between the regular 

 stations or farther inshore. From these there is some indication that 

 slightly larger surface catches may be expected as the shore is 

 approached. There were, however, some exceptions to this which 

 show that uniform increase is not to be expected any more than is 

 uniform distribution. 



Catches taken on a round trip to San Diego in June not only 

 indicated heavier production inshore but much heavier production 

 at the entrance to San Diego Bay. At the whistling buoy near Point 

 Loma, a large catch was made at the surface, but one at ten meters 

 was still larger, and another at twenty-five meters much larger. The 

 extraordinary numbers of Eucampia zoodiacus Ehr. in all three of 

 these catches make it very probable that this may have been an 

 unusually concentrated swarm. Since, however, Eucampia was also 

 unusually abundant at the regular stations for a day or two at about 

 the same time, it may be supposed that it merely found exceptionally 

 favorable conditions near Point Loma. This view is supported by 



