46 Vniversiiy of Califoriiiu Piihlicationx in Zooloyy [Vol.22 



Selenastrum hibrainum Reinsch. 



Identification satisfactory. Recorded five times from Station I in 

 small numbers. Once at Station III. Evidently too small to be held 

 by the net. 



The following forms were recorded only once or twice in small 

 numbers or else were noticed in living material. 



Botiyocoocus sp. Once at Stations II and III. May have been overlooked. 

 Bulbooliaete sp. 



Chodatella eiliata. Lemm. Once at Station III. 

 Crucigenia quadrata Morr. Once in daily series. 

 Crucigenia reetaugularis Cliod. 

 Crucigenia sp. Once at Stations II and III, 

 Diniorpliococcus lunatus A. Br. 

 Draparn.ildia pluniosa Ag. 



Golenkinia radiata Cliod. Once at Stations I and III. 

 Lagerheimia wratislavieuse Scliroed. Once at Station I. 

 Lauterborniella elegantissima Schmidle. Once at Stations I and II. 

 Monostroma sp. One* at Station III. 

 Nephrocytium agardhianum Naeg. 

 ■ Pleuroeoccus sp. 



Sorastrum spinulosum Naeg. 



Stigeoclonium (?) sp. Twice at Stations I and II. 



Tetrastrum sp. Onc« at St-ation III. 



Ulothrix sp. Twice at Station I. Doubtful identification. 



Bacillarmceas 



Plates 7-9 



station I Station II Station III Daily Hourly 



Number of forms recorded 44 58 53 25 32 



Av. number per eu. meter 22,609,062 39,478,317 36,826,859 28,055,459 29,029,248 



The diatoms are distinctly the most abundant frroup of orfjanisms 

 in San Joaquin plankton so far as present methods show. According 

 to these records they outnumber Schizophyceae 14, 33 and 18 to 1 ; 

 Chlorophyceae 12, 28 and 21 to 1, and Mastigophora 6, 14 and 7 to 1 

 at Stations I, II and III respectively, thus making tliem api)ear to 

 have a still more prominent place in the plankton than they had in 

 Illinois. There were always some diatoms in every collection at all 

 stations throughout the year. 



There was only one very distinct pulse at each station. At Station 

 I this appeared in May, while at the other stations, where it was larger 

 but less abrupt, it came in August. There is no way of telling from 

 these records whether this difference was due to better temperature or 

 to more stable conditions at those times. The fact that Smith Canal 



