498 



SPONTANEOUS AGGREGATION OF FLAGELLATES 



center of the slide, a circular band of flagellates is formed surrounding 

 a region of reduced hemoglobin. As would be expected, aggregation 

 and band formation take place much more slowly in the presence of 

 oxyhemoglobin than in plain water for much more oxygen is available. 



In a typical case two preparations were made simultaneously from 

 the same culture; (a) without blood, and (b) with blood. During the 

 mixing of (b) with blood, (a) was exposed to the air in exactly the 

 same way as (b). The times for the ring to become established in its 

 stationary position were; (a) 1 hour, 15 minutes, and (b) 3 hours, 

 40 minutes. 



In the preparations containing hemoglobin the circular Bodo zone 

 surrounding the central clear area, when once formed, grows in the 

 usual way, becomes square, and takes up its stationary position some 



Fig. 11. Preparation kept in darkness with flagellate band in equilibrium 

 position interrupted by a piece of moss, a, glass rod supporting cover-glass; 

 b, moss. 



distance inside the edge of the cover-slip. The whole central area 

 within the band contains reduced hemoglobin while the edges outside 

 it show the bright scarlet of oxyhemoglobin. The flagellate band 

 itself lies just within the region of reduced hemoglobin. 



A demonstration of the effect of oxygen on the equilibrium position 

 of the Bodo band can be arranged as follows. Some suspension of 

 Bodo is let in with a pipette under a cover-glass supported at its 

 corners, and a piece of some aquatic green plant, such as a frond of 

 moss, is pushed into the liquid from the middle of one side of the cover- 

 glass. The slide is placed in the dark and when the band of flagellates 

 becomes established in its stationary position it will cut straight across 

 the moss (Fig. 11). The preparation is now exposed to diffuse sun- 

 light, so that oxygen is produced by the plant in photosynthesis. 



