,30 Vnmersity of California PubUcations in Zoology [Vol.22 



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

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

 plankton. 



With the exception of three or four specimens of Gammarus 

 found on two different dates, and of a few miscellaneous forms, the 

 Entomostraca are far the largest of the local planktonts. While much 

 less numerous 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 represented. Most of 

 the forms found appear to be true planktonts. In fact, Cypris, the 

 sole member of the Ostracoda, is the only genus which is evidently 

 adventitious. 



Turbellaria, Oligochaeta, Hexapoda, Hydrachnida, Gastrotrieha 

 and Bryozoa barely find representation at any station. Their influ- 

 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, 1913, was a comparatively dry year so that the 

 production in most cases was probably below normal. The figures 

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

 colonial forms such as Bacillaria, 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 paper 

 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 acquaintance with them to distinguish synthetic and 

 analytic forms 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 discussion 

 except as incidentally referred to. They require separate discussion. 



