38 Univirsitij of California I'lihliciitioiis in Zooh/gij | \'oi.. 22 



Phormidium spp. 



Klutimi I Slutimi IT Station III Diiil/ Hourly 

 Averago 121,571 31,248 80,171 25,.i9o 



Probably includes more than one species. Genus uncertain also. 



Occurrence occasional through the year. Most abundant at Station 



I. Maximum in Sei)teinber. Not a very prominent planktont. 



Stigoncma sp. 



Station I Station II Station III Daily Hourly 

 Average 1,;!17 4.'5,fifi.5 8,8.'U 



Identification very doubtful. Filaments always fragmentary. 

 Nothing but vegetative cells seen. Referred to Stigonema jiartly on 

 account of occasional lateral arrangement of two cells in the fila- 

 ment. Never very prominent. Maximum in June at Station II 

 where it was most often found. Apparently of little importance. 

 Probably adventitious. 



The following forms were recorded but once, at one or more sta- 

 tions, or else are listed because thought to be present in living 

 material : 



Calothrix sp. Recorded once at Station I. 



Clathrocystis aeruginosa Kg. 



Cylindrospermum eomalum Wood. 



Dactylococcopsis rhaphidioides Hausg. Recorded once at Station I. 



Gloeocapsa gelatinosa Kiitz. 



Lyngbya sp. Recorded once at Stations I and II. 



Oncobyrsa rivularis Kutz. Recorded once at each station. 



Rivularia sp. Recorded once at Station I. 



Symplocastrum sp. Recorded once at Station III. 



Chlorophyccae 



Station I St.ifion II Station III Daily Hourly 



Number of forms 15 14 17 8 8 



Av. numbers per eu. meter 1,811,722 1.499,479 1,789,041 2.179..378 1.703.88.3 



These averages indicate only about one-thirtieth of the number 

 found by Kofoid (1908) in Illinois. Since, however, the main con- 

 tribution here was made by Actinastrum, Coclastrum, Pcdiaslrum 

 and Sccncdrsmus it may be readily understood that losses through the 

 net account for most of the ditFerenee. The group was represented 

 through the entire year, though the numbers were often very few. 

 Station I showed the peculiarity of a great increase in numbers in 

 May and June, a decline in July and August, and another well sus- 

 tained increase in September, October and November. Stations II 

 and III showed only one consjiicuous rise in numbers, covering about 

 four months, from July to October inclusive. The numbers occur- 



