1920] Allen: Planktan of the San Joaquin River 85 



Those taken to be most typical of this miscellaneous assemblage 

 were found on the bodies and appendages of Entomostraca, especially 

 Cyclops. Most of these were large enough to be fairly accurately 

 counted. In view of the miscellaneous character of the forms in- 

 cluded, it is undesirable to draw definite conclusions. There is, how- 

 ever, a clear suggestion of preference for sewage and quiet water. 

 Higher temperatures are also distinctly favorable for the assemblage 

 and this is in marked contrast to nearly all the other ciliates. 



The following forms were recorded only once or twice or else 



were thought to be observed in fresh material. 



Aspidisea sp. 



Bursaria sp. Twice I, onoe. III. 



Carehesium sp. 



Climacostomum virens St. 



Conilylostoma vorticella Ehrbg. 



Diilinium balbianii Btschli. 



Enchelys sp. Twice, T, once, IIJ. 



Epistylis sp. Twice, 11. 



Frontonia sp. Twice, I, once. III. 



Gastrostyla sp. 



Glaucoma sp. Once, I. 



Lacrymaria sp. 



Loxophyllum sp. Twice, I. 



Mesodinium acarus St. 



Pyxidium cothurnoides Kent. 



Rhabdostyla brevipes CI. & L. Once, I. 



Spirostomum sp. 



Trachelius ovum Ehrbg. Twice, I. 



Urocentrum turbo Ehrbg. 



Suctoria 



station I station II Station III Daily Hourly 

 Number of forms recorded 3 3 3 .... 1 

 Number of indi- 

 viduals per cubic meter 762 8,99.5 8,039 1,969 



Only three forms were recorded from this group and they oc- 

 curred at all three stations but mainly in the last three or four months 

 of the year. In no case were the numbers very large. While genera 

 could not be identified with much confidence, it yet seemed clear that 

 the forms recorded were Suctoria and that the generic designation 

 was probable. Inasmuch as none of the three forms appeared to be 

 a true planktont and the numbers were few, it seems hardly neces- 

 sary to attempt detailed discussion. The most notable suggestion 

 that can be made is that sewage seems unfavorable to all three forms. 

 The following are the three forms recorded. See tables 1-5. 



Acineta sp. Podophrya sp. Sphaerophrya sp. 



