FRANDSEN. — REACTIONS OP LIMAX MAXIMUS. 203 



plished by moving toward the earth. In hunting for food, it must 

 naturally do some climbing. These facts lead us to expect a possible 

 difference between the geotactic response of the nighttime and that of 

 the daytime. My experiments in this matter, however, gave inconclusive 

 results. But the animals experimented on were not in their normal en- 

 vironment. There was no light and little change in temperature to assist 

 the instinct, if it exists, in divining night from day. Moreover they did 

 not have to seek food, for it was constantly supplied them. Such being 

 the case, the instinct of concealment would be the main environmental 

 influence on the animal, and this impels it toward the earth. 



These experiments have shown, then, that when the mechanical con- 

 ditions are favorable, most animals exhibit a positive geotaxis. This is 

 as we should expect. There were, however, a few exceptions. A few 

 animals went up when all the factors enumerated seemed to point to the 

 probability of a downward movement, and there were also a few animals 

 which went down when the mechanical difficulties were such as should 

 have impelled them upward. As previously noted, the upward-moving 

 animals sometimes displayed an unusual amount of activity, and the ex- 

 ceptional cases of positive geotaxis in the negative group were those of 

 animals usually slow and stupid. As the effort was constantly made to 

 select only fairly active animals in good condition for producing mucus, 

 there were not many of these exceptions. Knowing the habits of the 

 animal, we may naturally associate its activity with its food condition. 



The question then comes up, Does the state of the animal's nutrition 

 affect its tendency to move toward the earth ? Does a poorly nourished 

 animal respond to the stimulus of gravity differently from a well-nour- 

 ished individual ? To get an answer to this question, four animals were 

 put into a small box which contained nothing but moist earth. The slugs 

 were kept there for three days, and a series of geotactic tests was then 

 made upon them. Two of the four individuals were inactive, and so un- 

 satisfactory in response that no series was obtained. The other two were 

 rather restless, but precise in response. All the animals were then 

 returned to the box and supplied with fresh cabbage leaves. The next 

 morning another series of geotactic stimuli was given. The rather 

 meagre results given in Table IX. are perhaps not worth very much, since 

 only one individual (No. 1) out of the four resjjonded well in both cases. 



The ratios given in the second column (Table IX ) indicate that 

 slugs Nos. 1 and 2 belong with those of the positive half of Col. 8, 

 Table IV. I unfortunately neglected to control these experiments by 

 observing the geotaxis before the animals were deprived of food. In 



