204 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



TABLE IX. 



Comparison of Responses of Individuals when poorly nourished and 



avhen well nourished. 



both instances (Nos. 1 and 2) the animals were rather dry, and they 

 were not noticeably different in this respect after being well fed. No. 2 

 was less active and less precise in response after it had had plenty of 

 food. I think these experiments too few to warrant laying much stress 

 upon them, but I have given them here because they at least point in the 

 direction of what we might reasonably expect, since the natural desire of 

 the animal to escape from its narrow prison and the impulse to seek 

 food would both tend to make it go up, if given the opportunity. 



Another element which may alter the slug's inherent geotaxis is 

 probably the state of fear. This element may be combined with the 

 impulse to seek food, as is perhaps the case in the instances just given, or 

 it may operate by itself. Animals which had just been captured were al- 

 ways kept in a small tin box. The captured animals would thrust them- 

 selves between the box and lid, which was not perfectly tight, in their 

 endeavors to escape, and they had to be frequently pushed back. When 

 they were transferred to the large box mentioned at page 187, it was 

 always found that they had all collected in the upper part of the smaller 

 box. This may have been solely for the purpose of getting air, but such 

 animals put on a glass plate were exceedingly active and restless^ and 

 usually exhibited a decided negative geotaxis. I have not made any care- 

 ful set of experiments to find out whether these negatively geotactic 

 animals afterwards became positive. In one instance, I confined over 

 night in a small flower-jar a slug (not a freshly captured one) which had 

 shown a very decided positive geotaxis. In the morning it was found at 

 the top of the jar, and, when placed on a glass plate, showed great activ- 

 ity, as though it sought to escape. In every one of the tests which I 

 then made, it responded negatively. From these few observations, it 



