H. MUNRO FOX 



487 



If a preparation such as has been described, in which the square- 

 shaped band of Bodo is established with its sides parallel to the edges 

 of the cover-glass, is kept in a moist chamber and examined again 

 on the following day, it will be found that the band has retreated 

 somewhat from the edges of the cover-slip. On the following day 

 again the band will be further in still and will have taken on a circular 

 instead of a square form. Later on all the flagellates will be clumped 

 in one mass at the center of the slide, after which they will gradually 

 dissipate to become evenly scattered throughout the liquid again. 

 In fact the Bodo band goes through the same series of changes which 



Fig. 7. Main flagellate band reaches its equilibrium position having left 

 behind an inner ring surrounding air bubble. 



Fig. 8. Flagellates around air bubble advance to its surface . 



it originally underwent in its formation but in the reverse order. 

 Through all the series of changes the organisms continue in full 

 motile activity. The retiral of the band from the outside may be 

 hastened by placing the slide in an ice chest. In the course of a 

 few hours only, the square band will have become a circular band 

 situated near the center of the preparation. The swimming activity 

 of the Bodo is, incidentally, not noticeably decreased by the low 

 temperature. If, on the other hand, the moist chamber containing 

 the preparation is kept at a higher temperature than that of the 

 laboratory, the band retires from the edges much more slowly, if at 



