AN INVESTIGATION INTO THE CAUSE OF THE SPONTANE- 

 OUS AGGREGATION OF FLAGELLATES AND INTO THE 

 REACTIONS OF FLAGELLATES TO DISSOLVED OXYGEN. 



Part II. 



By H. MUNRO fox. 



{From the Laboratory of the Marine Biological Association, Plymouth, England, and 

 the Biological Laboratory of the School of Medicine, Cairo, Egypt.) 



(Received for publication, September 21, 1920.) 



Previous Work. 



As far as I am aware, the only workers who have attempted to 

 find the causes of the spontaneous aggregation of flagellates are 

 Jennings and Moore. ^ They used a flagellate called Chilomonas 

 Paramecium and came to the conclusion that the organisms are 

 attracted by the carbonic acid produced by themselves. Where by 

 chance the flagellates are more crowded together in the liquid on a 

 slide, more carbonic acid is produced than elsewhere and in conse- 

 quence yet more flagellates are attracted into these regions. The 

 experimental evidence on which they based their conclusion was as 

 follows. They found: (1) that when a dilute mineral acid was let 

 in under the cover-slip by means of a capillary pipette into a sus- 

 pension of the flagellates the latter were attracted by the drop; and 

 (2) when a bubble of carbon dioxide was introduced in the same man- 

 ner the organisms crowded around it, whereas they did not collect 

 around an air bubble. Therefore, Jennings and Moore concluded, in 

 the formation of spontaneous collections the flagellates are attracted 

 to regions which become more acid than the remainder of the liquid, 

 through the accumulation of the carbonic acid produced by the indi- 

 viduals already there. 



^ Jennings, H. S., and Moore, E. M., Studies on reactions to stimuli in unicellu- 

 lar organisms, VIII. On the reactions of Infusoria to carbonic and other acids, 

 with especial reference to the causes of the gatherings spontaneously formed, 

 Am. J. Physiol, 1902, vi, 233. 



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