2 



K. MITSUKUBL 



KU 



gîass-plate A (Fig. 1) which happened to he semi-circular in shape with 

 the diameter of ahout one foot was placed on a tahle. This was made 

 slightly wet so that the mollusc could easily crawl over it. On this, a 

 glass-vessel B, ahout 10 cm. in diameter and 3 cm. in height was placed 

 and filled with water to the depth of ahout 1 cm. Various articles C, D., 

 P, and G- among which a small dissecting-dish C inverted and tilted 

 up by a small box D was very conspicuous were placed in the quarter 

 toward which the animals were expected to move. 



100 individuals* out of ahout 200 which had previously been used 



in a similar experiment were pick- 

 ed up at random and placed in 

 the glass-vessel B. Light was 

 shining from the two windows N 

 and E plaeed at a right angle to 

 each other. This was at 2 P.M. 

 (Aug 6). Almost immediately in- 

 dividuals started in the direction 

 of the arrow BH which represent- 

 ed the direction of the least light, 

 E climbed over the edge of the 

 glass-vessel Band crept over the 

 glass-plate A in the same direc- 

 tion. Before long the vessel B 

 was nearly empty. At 5 P.M. 

 three and half hours after the 

 Fig. 1. commencement of the experi- 



ment, the individuals were disposed as follows : — 



Remaining in the dish B 8 



At the spot a 1 



.. At the spot b 1 



At the spot c 6 . 



* It is possible that iu earlier experiments there was some mixture of the individuals 

 of f.. sitchana. 



