FRANDSEN. — REACTIONS OF UMAX MAXIMUS, 189 



The column headed with the minus sign shows the number of times the 

 animal responded by moving away from the source of stimulus ; the one 

 headed with the plus sign, the number of times it moved towards that 

 source ; and the zero column, the number of times there was no response. 

 I found that the animal would respond very definitely and precisely to 

 stimuli two or three times in succession by immediately retracting the 

 tentacle touched and moving away from the stimulating influence. After 

 the third trial, however, it either refused to change its direction of loco- 

 motion or else moved directly towards the source of the stimulus. If a 

 respite of a few seconds before the next stimulation was then permitted, 

 the animal would again give a precise negative response for two or three 

 trials, and then, as before, it desisted. Out of the total 145 tests, there 

 was a negative response in two thirds of the trials. The remaining 

 trials — one third of the whole — were about equally divided between 

 the positive responses and refusals to respond at all. Sometimes five or 

 six tests were made in quick succession, so that the total negative 

 response is rather less than it would have been if a rest had been given 

 in each case after three tests. Out of the 21 cases of direct positive 

 response, 15 were cases where the right tentacle was touched, and the 

 remaining 6 were due to stimulation of the left tentacle. Similar, but 

 more marked, differences between the results of stimulating the right and 

 the left tentacles were observed in other experiments. This suggests that 

 either the right tentacle may be less sensitive to stimuli, or that its coun- 

 terirritancy may be more readily aroused. There is, however, a third 

 possible cause. The animal may have an innate tendency to go to the 

 right, and, if so, this tendency may diminish to some extent the force of 

 the stimulating agent when it impinges on the right side of the animal, 

 and correspondingly increase the response when the stimulus is directed 

 upon the left side of the animal. Something further will be said about 

 this point in a later part of the paper. 



A few thigmotactic experiments were next made on the sides of the 

 animal posterior to the head. The right and left sides were touched 

 alternately. The results are given in Table 11. 



Phenomena like those observed in stimulating the tentacles are seen 

 here, and they also agree with similar observations by Davenport and 

 Perkins ('97, p. 109.) After two or three trials, the animal begins to 

 show resistance, and if the finger is held against its side, will sometimes 

 try to displace the finger by pushing against and curling the body around 

 it. The frequency of the negative response is here somewhat less marked 

 than in the preceding experiments, which is as we should expect, owing 



