Marine Microbiology 249 



finest membrane filters may result from the recovery of fragments 

 of fragile algae that are broken during filtration. From experi- 

 mental results in dark bottle C^^ uptake, small heterotrophic 

 organisms such as bacteria did not seem to be responsible for 

 the liigher recoveries of assimilated C^^ on the finest membrane 

 filters. The algae which accounted for the bulk of the C^"* 

 assimilation observed in this study were smaller than 30 /».. The 

 possible existence in the sea of minute autotrophic organisms 

 ( < 1 /'. ) cannot be ignored, and this possibility should be exam- 

 ined further. 



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