CANADA PORCUPINE 81 



other forms many times in succession but positively to the 

 circle at the first encounter in an experiment. 



14. The brightness discrimination of the porcupine is about 

 10 shades in Nendel's series of gray papers. Possibly a little 

 finer discrimination can be made at either end of the series 

 but a slightly greater ^'ariation seems to be required with the 

 middle grays. It is not certain that they cannot discriminate 

 shades of smaller difi^erence but they do not readily use such 

 distinctions in determining their behavior. 



15. The porcupine does not, and probably can not, discrim- 

 inate and react intelligently to color where colored papers are 

 employed as stimuli. 



16. No account of the area of acute vision of the eye of the 

 porcupine has been given in the literature, so far as the writer 

 knows. Even Slonaker's excellent treatise omits this animal. 



1 7 . The natural instinct of the porcupines to lay out runways 

 in the fall of the year to particular clumps of trees which they 

 use as feeding grounds in the winter, probably has much to 

 do with making these animals especially expert in threading 

 complicated mazes. Sliding the maze so as to change the foot- 

 ing and destroy the paths indicates that the paths are a result 

 rather than a cause of the animals taking the same general 

 direction to the feeding grounds. 



18. Rotating the maze 90 degrees thus changing the direc- 

 tion and slope of each of the alley ways confused the animal. 

 After relearning the second time, another rotation of 90 degrees 

 in the same direction had the same effect but relearning the 

 third time was more rapid. A third similar rotation caused 

 less confusion than the others while restoration to the initial 

 position appears to call out the initial responses. Kinaesthetic 

 sensations were, no doubt, modified in these variations and 

 may be also static sensations, if the porcupine possesses such 

 sense -modalities . 



19. After once learning the maze the porcupines were able 

 to follow it in 'the dark, or when darkness was absolute for 

 the human eye after two hours of adaptation. Learning under 

 these same conditions differs little from learning in daylight. 



20. Absence from the maze for 100 days at a time did not 

 materially affect the porcupine's ability to traverse it correctly. 



