An Investigation into the Cause of the Spontane- Ous Aggregation of Flagellates and into the Reactions

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 consequence 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 suspension of the flagellates the latter were attracted by the drop; and (2) when a bubble of carbon dioxide was introduced in the same manner 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 individuals already there.