72 University of California Publications in Zoology [Vol.22 



Peridinium sp. 



Identification of genus satisfactory. Species different from P. 

 cinctum but not placed. Recorded four times at Station II three 

 times at Station III. 



Phacus pleuronectes Ntz. 



Station I Station II Station III Daily Hourly 



Average 25,375 1,048 1,131 



Identification questionable. Loss through net probably very heavy. 

 Occurrence twice at Station II and thrice at Station III in small num- 

 bers. Recorded with only five exceptions at Station I through last 

 three months of year. May have been overlooked before. Kofoid 

 (1908) designates this genus and this species as a summer planktont. 

 The failure of the record here to support fully this view may be due 

 to small size and consequent inaccuracy with silk net catches. 



Platydorina caudata Kofoid. 



Station I Station II Station III Daily Hourly 



Average 431 3,569 5,020 206 48,290 



Identification positive. Loss through net considerable. Occur- 

 rence quite distinctly limited both by temperature and sewage. Re- 

 corded only six times at Station I, all at variable intervals from Au- 

 gust 2 to November 1 and in very small numbers. Nine occurrences, 

 mainly in August and September at each of the other stations. No case 

 of occurrence in temperature less than 17° C. Maximum at Station 

 I on September 2, Stations II and III on September 13. Considering 

 the small numbers and the short period of occurrence, the similarity 

 of occurrence at the three stations is most remarkable. All stages of 

 development were found and special collections were made for Pro- 

 fessor Kofoid in order that he might study some features of develop- 

 ment. 



Pleodorina californica Shaw. 



Station I Station II Station III Daily Hourly 



Average 123 21,231 6,282 413 67,751 



Identification certain. Probably most of the matured colonies 

 were retained by the net. Recorded only twice (in August) at Sta- 

 tion I. Evidently strong sewage is deterrent though Kofoid (1908) 

 mentions sewage as probably a factor leading to larger numbers in 

 1897 than in 1898. Station II showed the only consistent develop- 

 ment of this organism. After being recorded in mid-June it was not 

 found until three weeks later when it began an eight weeks period of 



