52 L. W. SACKETT 



of the whole form physiologically improbable if not impossible. 

 Add to this the fact that the forms were empty forms without 

 a constant background and the case is more evident. 



The second question for discussion is answered in part by 

 the first for the two are, in a large measure, alternative. The 

 suspicion that the porcupines might be observing only the 

 boundary line led to the use of the irregular forms in the pair- 

 wise study. Suspicions become almost, if not wholly, convic- 

 tions during the tests with the irregular forms four-wise wherein 

 discrimination must be a part of the form only. In choosing 

 these forms the porcupine would run his line of regard, or visual 

 axis, around the form till he came to the part which differen- 

 tiated it from the others. He would often give a quick start 

 as of surprise when he reached such a part, hold the eye and 

 face steady for a moment as if to reassure vision, sometimes 

 stretch the neck and body toward the point of interest and 

 then pass on. When he reached the circle he would again trace 

 the edge of the form with the eye and as he came to the starting 

 place, usually the base, without any interruption, he would 

 enter and secure the food. 



The kinaesthetic elements which enter in this explanation 

 will be classed as secondary visual factors and not as separate 

 criteria in themselves. This conclusion was not what was ex- 

 pected when the apparatus was designed and the experiment 

 begun. The animal's behavior before the regular forms, five 

 of which were symmetrical in regard to the central point was 

 not sufficient to bring out the phenomenon. It was more than 

 that of throwing the line of regard from side to side in rapid, 

 irregular movements without any of the definite exploitation 

 which occurred with the irregular forms. 



It remains to be determined whether the reaction is anything 

 above a simple percept of the whole, a part, or a quality, ac- 

 companied by a memory of a sufficiently high character to 

 bring about a positive rather than a negative reaction toward 

 it. For instance, when the animal refused to enter the wrong 

 forms 15 to 20 times and ended by reacting definitely and posi- 

 tively to the circle the first time he encountered it in the search 

 can it be said that he knew what he was searching for while 

 he was searching, or that he went about it with an indefinite 

 image of the thing toward which he reacted positively when he 



