6 4 



SAKYO KANDA. 



pressure of gravity and the precision of orientation of the slug?" 

 (2, p. 100). An attempt was made by the writer to determine 

 experimentally the same question for Littorina littorea. The 

 experiments were conducted in sea-water. Light was excluded 

 by means of the cover-box. The results given in Table II. show 

 that the higher the angle the larger is the number showing 

 negative geotropism, and the lower the angle the larger the number 

 of (so-called) positively geotropic animals. 



TABLE II. 



GEOTROPISM OF SNAILS AT THE DIFFERENT ANGLES OF INCLINATION OF A GLASS 

 PLATE IN SEA-WATER IN TOTAL DARKNESS. 



At beginning of experiments each head pointing downward. Table shows re- 

 sults after one minute. 



As already pointed out, however, it is misleading to consider 

 that the negative geotropism of the snails reaches zero on the 

 horizontal surface of the earth. The force of gravity stimulates 

 the snails, when it happens to pull along the line of the dorso- 

 ventral axis of the animals, that is, on the horizontal surface, 

 as the preliminary experiment A has shown. But the larger the 

 angle the shorter the time required for orientation. This is 

 shown in the "horizontal" column, when the number of the 

 animals, most of which were "orienting" at the end of one minute, 

 decreases as the angle of inclination to the vertical increases. 



Experiment B. It has been supposed that hydrostatic pressure 

 affects the reaction of an animal to gravity. To decide this 

 question, a series of experiments was made in air. Light was 



