DIATO:\I MOTION. 1^3 



■-39 Rested six minutes. The iris diaphragm 



was then opened wide, and the whole 

 field flooded with light. No resumption 

 of motion occurred in four minutes, and 

 the experiment terminated. 



FiGURK III, R. CvDibclla oastroides, Kutz. 



Revolved on one end. 



At X, the diatom turned through about go*^ 

 on its centre. 



Reversed motion. 



At 8.04 the diatom had not returned to the 

 field. On moving the slide it was found 

 at a point about half the diameter of the 

 field 'from the last position, and still pro- 

 ceeding in the direction lo — 1 1. 



