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SPONTANEOUS AGGREGATION OF FLAGELLATES 



The phenomenon of spontaneous aggregation is best studied as 

 follows: A square cover-glass supported by wax feet at its four 

 corners, or, better still, by short pieces of glass rod previously cemented 

 to the corners, is placed on a dry slide. Some liquid from a Bodo 

 culture is then run in from a pipette beneath the cover-glass until 

 it just fills the space between the latter and the slide. At first the 

 flagellates are evenly scattered throughout the preparation (Fig. 1) 

 but they do not remain so for an indefinite time. At the end of an 



Fig. 1. Slide and supported cover-glass at beginning of an experiment, showing 

 flagellates evenly scattered through the liquid beneath the cover-glass. In all 

 diagrams the density of the dots represents the density of distribution of the 

 flagellates, a, wax support to cover-glass. Figs. 1 to 5 are successive stages of 

 one experiment. 



Fig. 2. Formation of central aggregation of flagellates. 



interval which may be 2 minutes or 2 hours they begin to collect 

 into one or more groups towards the center of the cover-glass, the 

 size of these aggregations increasing until they contain most of the 

 Bodo present in the liquid (Fig. 2). The flagellates in the aggrega- 

 tions are in intense movement. There is no solid body forming the 

 center of a collection and indeed the presence of any such object is 

 purposely avoided by filtering the suspension of Bodo through fine 

 bolting-silk before making the preparation. Under a square cover- 

 glass measuring | inch X | inch, which was the size used in the 



