506 



SPONTANEOUS AGGREGATION OF FLAGELLATES 



the aperture commenced to swim actively and arranged themselves 

 in a band at a certain distance inside the aperture (Fig. 16). This 

 semicircular band gradually retreated inwards as the atmospheric 

 oxygen diffused in. The effect of the absence of oxygen is thus not 

 immediately injurious; it stills the motion of the flagellates but after 

 48 hours in the absence of oxygen they recover their full activity 

 as soon as they have access to oxygen again. 





Fig. 16. Experiment to test the effect of the absence of oxygen on flagellates. 

 Distribution of the flagellates in the preparation already shown in Fig. 14, when a 

 hole was made in the vaseline wall at the end of 48 hours, a, aperture in vaseUne. 



Minor Phenomena of Aggregation and Band Formation. 



There are several minor phenomena in the process of aggregation 

 and band formation which have not been mentioned up to the present 

 but which must now be described. 



1. It should be added to the general description of aggregation 

 and band formation that when very fev/ flagellates are present in the 

 liquid no central aggregation is formed, but after a certain time the 

 flagellates simply leave the central region of the preparation and 

 arrange themselves directly in the final stationary position of the 

 band. 



2. A vertical section of the Bodo band is not an upright wall but 

 has the shape shown in Fig. 17. The upper part of the band is 

 nearer to the center of the preparation than the lower part. Further, 

 there are more flagellates present in the upper and lower regions, 

 that is next the cover-glass and next the slide, than in the inter- 

 mediate region. The latter is curved in section, the concavity being 

 towards the edge of the preparation. The band assumes this shape 

 as soon as it forms and keeps the same shape when in its final station- 



