30 Viiivtrfiitij uf Culifoniiu rublications in Zuvlugy L^oi-. 22 



content as being a deciding factor. Apparently, most of the species 

 recorded liere are to be regarded as normal constituents of the local 

 plaiditon. 



With tlie exception of thi'ec or four specimens of Gamnianis 

 found on two different dates, anil of a few miscellaneous forms, 1lic 

 Entoiiiostraca are far the largest of the local planktonts. \Vl:ilc much 

 less nunu'rous on the whole than they were in the Illinois River, they 

 undoubtedly play a large part in the life of our waters. Copepoda, 

 through larval forms, are distinctly in the ascendant, with Clado- 

 cera somewhat scattering and Ostracoda barely I'cpresented. Most of 

 tlie forms found aiii)ear to be true planktonts. In fact, ('ijpris. the 

 sole mend)er of the Ostracoda, is the only geinis wliicii is evidently 

 adventitious. 



Turbellaria, Oligochaeta, Ilexajwda, Hydrachnida, Gastrotricha 

 and l>r'yozoa barely find repi'esentation at any station. Thi'ir infiu- 

 ence in the plankton is negligible. 



TOTALS OF MAJOR GROUPS 



The following table of averages (text table I) will serve to indi- 

 cate in some measure the proportionate representation in the San 

 Joaquin plankton of the most typical constituent groups. As already 

 noted elsewhere, lt)13, was a comparatively dry year so that the 

 production in most ea.ses was probably below normal. Tlie figures 

 given are the result of the count of individuals, except in the case of 

 colonial forms such as Ba-cillaria, Synura and Scenedesmus where the 

 colonies only were counted. The small numbers as compared with 

 Kofoid's similar table (1908) for the Illinois plankton of 1898 is 

 mainly due to the fact that all San Joaquin enumerations are from 

 silk net collections, whereas many of his were from filter paj)er 

 catches. Our table includes all recorded forms whether satisfactorily 

 identified or not. It should be noted that in the total of synthetic 

 organisms Schizophyceae are included because they do some of that 

 work. All of the Mastigophora are also included because there was 

 not sufficient ac(|uaintance with them to distinguish synthetic and 

 analytic fomus and it was understood that most of them found here 

 were synthetic. The averages are computed on the basis of 104 

 catches for Station I, 52 for Station II and 51 for Station III. The 

 daily and hourly series are not included in the general di.scu.ssion 

 except as incidentally referred to. They require separate discussion. 



