114 TJmversitxj of California Puilications in Zoology [Vol. 22 



year, with llic exception of May and June, the time of the mnnntain 

 floods. Tlie decrease in number of forms at this time strengthens 

 the view that flood waters dilute the sewage and reduce the food 

 supply, thus reducing reproductive and growth activities. There is 

 also considerable loss through washing out, evm with the rather low 

 waters of lOl:! The 1914 collections sliouhl certainly tlirow some 

 additional lif^ht on this question. 



THE DAILY SERIES 



As noted elsewhere, the daily series was undertaken in the hope 

 that it would give definite information concerning the problems of 

 recurrent pulses and the incident conditions. This hope was partly 

 realized, although the thirty-one days constituting the .series was not 

 enough, and it is evident that more faithful adherence to a uniform 

 hour of collection is desirable. Since this last would involve very 

 marked diiferences in condition of tide, it is i)robable that Stockton 

 is not a good locality for such a test. It wouhl be much better to try 

 it in a locality free from tidal influence. It is also probable that 

 the large amount of traffic past the point at which this series was 

 taken might affect the results. At any rate, these two factors, at least, 

 might be eliminated in some other locality. However unimportant 

 they might later be proven to be, they do make the problem need- 

 lessly complex. 



Under the circumstances it does not seem desirable to discuss 

 individually even the more conspicuous species. Generalizations to 

 be reached by such discussion in this series do not differ materially 

 from those to be obtained from consideration of the larger gi'oups. 

 Species records are given in table 4. 



Although the thirty-one days did not give a series of sufficient 

 length to be wholly satisfactory, there are some points of decided 

 interest. These are graphically indicated in plates 1, 6, and 3. In 

 plate 1, .showing volumes, there was a prominent pulse a]iex on July 

 13, another maximum for the series on July 18, and another almost 

 as large on July 27. Explanation of this is afforded in part by 

 plate 6, where it is shown that chlorophyll bearers and Protozoa and 

 Rotifera all had pulse culminations near July 13 and July 27, while 

 the Entomostraca showed a pulse culmination nuiximum for the series 

 on July 22. It is evident that the median position of the volumetric 

 maximum is due to its dependence on the entomostraean inimci'ical 



