66 SAKYO KANDA. 



The question, however, arises: Is there any maximum or 

 minimum of resistance or weight which makes the snails crawl 

 either up or down? This question will be answered later. 



Although differences exist between Tables II. and III., the 

 results in the latter table in general show a fair uniformity with 

 Table II. The hydrostatic pressure, 1 therefore, seems seldom, 

 if ever, to affect the negative reaction of the animals to gravity. 

 These two tables also show a fair agreement with the results 

 obtained by Loeb (8, pp. 6-8), Davenport and Perkins (2, pp. 

 100-105), and Frandsen (3, p. 198), that is, a steady increase in 

 negative geotropism with increase in the angle of inclination. 

 Davenport and Perkins's view in this respect is fully confirmed 

 (2, p. 105). 



3. What Determines Whether the Head End Will be Directed 



Up or Down? 



Experiment A, Instead of the plain glass plate used for ex- 

 periments hitherto, a ground-glass plate was employed for the 

 following experiments, for two reasons: (i) Since the animals 

 live along a rocky seashore, the plain glass plate may not be a 

 proper support for them; and (2) the animals being positively 

 stereotropic, it was thought well to test the effect of contact 

 stimuli upon their geotropism. Light was excluded in these 

 experiments as usual. In the results given in Table IV. it is 

 interesting to note, as expected, a decided decrease in the number 

 of negatively geotropic and an increase of "positively geotropic" 

 individuals with decrease in the angle of inclination. Moreover, 

 below the 45, no individuals were in their original position. 



The animals can stick better to the ground plate than they do 

 to the plain glass. In consequence, they can resist the pull of 

 gravity better on the former than they do on the latter. If so, 



1 On preparing Mr. Kanda's Ms. for publication it strikes me that the chief 

 difference between the experiments shown in Tables II. and III. lies in the buoyancy 

 rather than the pressure factor. Remembering that the air pressure must be added 

 to that due to any depth of water, the difference in pressure in Table II. as contrasted 

 with III. is almost negligible. But the weight of the animal in water is much less 

 than in air. The slight difference between Tables II. and III. is to me strong evidence 

 against the buoyancy theory as playing any large part. Mr. Kanda is in Japan 

 and I cannot call his attention to these points, so I venture to add this footnote. 

 E. P. LYON. 



