8o SAKYO KAXDA. 



points. Haseman states: "Even more interesting is the fact 

 that when, with a vertical surface, a stone, upon which snails 

 were crawling at random, was raised out of the sea, the snails 

 always followed the vanishing film of water even when the vertical 

 surface was rotated through an angle of 180. In this case, the 

 rotation of the vertical surface would reverse the direction of 

 motion of the film of water and the snails would at once turn 

 around and follow it. But if most of the water was previously 

 removed from the surface of the stone, in order that the film 

 might entirely disappear before the snails (which were crawling 

 downward in the direction of the vanishing film) had reached the 

 lower surface and if, as the film was drying up, the vertical surface 

 was rotated through an angle of 180, the snails continued to crawl 

 for some time in the direction in which they had started. In other 

 words, the snails crawled upward instead of downward. They 

 continued to crawl thus until the rough surface, food and moisture 

 either deflected or stopped their movements. In the above 

 experiment, the mere turning of the moist but filmless surface 

 through an angle of 180 does not seem adequate to reverse at 

 once the reaction to gravity and light, if either of these have a 

 direct influence on the rhythmical movements of Littorina" 

 (4, p. 116). 



Certainly this is not a simple matter. In the first phase, 

 Haseman does not state, where "the above experiment" was 

 conducted, what condition of sunlight or diffuse daylight, there 

 was, and if the experiment was in sunlight, in what direction 

 the rays were falling and so on. His description as well as ex- 

 periment is not at all accurate. Judging from the above descrip- 

 tion, however, he seems to have conducted the experiment "in 

 nature," and so in sunlight. If so and if the sun were fairly 

 above, it is small wonder that 'Svhen the vertical surface was 

 rotated through an angle of 180," thus rotating the motion of 

 the film of water, " the snails would at once turnaround and follow 

 >ince the snails are negative to light, as has been shown. In 

 i In- case of Haseman where the film was reversed, in which "the 

 vertical surface was rotated through an angle of 180," and "the 

 snails continued to < r,i\vl for some time in the direction (upward) 

 in \\liieli they had st. tried," another explanation is possible. The 



