CANADA PORCUPINE 57 



out the feeding period lifting the apparatus from right to left 

 and vice versa after each test. After the animal had eaten his 

 food, he turned, passed in front of the experimenter and about 

 three feet beyond, with his face turned from the experimenter, 

 while the selection was being made. The space between the 

 successive positions of the apparatus was sufficient for a new 

 adjustment of the animal's moA'ements before he made the 

 next choice and the distance from the experimenter was greater 

 than that at which the porcupine was ever known to react from 

 a visual stimulus of a still object. 



The experiment was begun by presenting the blue and the 

 green boxes, with food in the blue. No. 3 was given 14 series 

 of 20 each and No. 10, 20 series. The results were negative. 

 Neither porcupine appeared to be making progress and No. 3 

 renewed his habit of going to a particular position as he had 

 previously done in the form tests. Experiments with colors were 

 temporarily discontinued and white and black boxes (Nendel's 

 grays 1-50) were substituted. The standard of excellence 

 arbitrarily determined was 100% correct choices in any one 

 series of 20 tests. On this basis No. 10 learned to choose the 

 black in 13 series while No. 3 required 13 series to break up 

 his place habit. After that there was improvement and he 

 made the 20th series perfect. Light gray was then substituted 

 for the white, thus varying the comparison box and leaving 

 the food box constant. No. 10 was very much confused but 

 No. 3 was not confused in the least. When gray 21 was insert- 

 ed in place of gray 11, porcupine No. 10 was even more con- 

 fused than before, but No. 3 was again not disturbed. When 

 grays 32 and 41 were successively introduced No. 10 was thrown 

 off each time but No. 3 was still master of the conditions. Up to 

 this point the conditions of the experiment were identical for 

 the two animals. It was thought best, however, to modify the 

 method for the different animals. No. 3 was given gray 45 as a 

 comparison box but failed in 17 series. Table IX shows that he 

 was no nearer the mastery at the end than he was at the begin- 

 ning and was so confused that when he was given gray 41 again 

 as a comparison he failed with that. Porcupine No. 10 was 

 given new boxes with grays 41 and 50 but was not certain of 

 them after 13 series. In seeking an explanation for this it was 

 discovered that Bradley black had previously been used instead 



