339 
1 can: corroborate this in principal. In a great number of expe- 
riments taken with a siskin I endeavoured to remove every possible 
mark which might have led the bird to the right box. To this 
purpose I covered the frontside of the boxes, as also the bottom of 
the cage in front of them with strips of cardboard, which were 
constantly renewed. Husks of the eaten seed were carefully cleared 
away each time and the flaps of the boxes were renewed each time, 
in order that the bird might not be able to tell it by scratches it 
might have made with its beak. In spite of these precautions, the 
bird, once having learned that its food was placed in oue particular 
box, rarely lifted the flap of another by mistake. As a positive 
proof, in connection with the supposition that the birds were led by 
other characteristics than the fixed place of the food box, I relate 
the following experiment: When the siskin had duly learned to go 
for its food to one particular box, I took a second cage, in all respects 
similar to the one in which the experiments had been made. This cage 
was perfectly new and the siskin had never been in it before. 
To this cage I had four new foodboxes attached, exactly like the 
four which up till that moment had been used for the experiments. 
The siskin had never eaten from these boxes, nor had they ever 
contained any seed. I now removed the siskin for ashort time, on different 
days, from cage 1 to cage 2. No seed had been put into any of 
the boxes in order to avoid that the bird should smell the seed behind the 
flaps. It was evident that the bird felt strange in its new cage; it 
flew about continually, coming up close to the food boxes, without 
however lifting up any of the flaps. After it had quieted down a 
little, the bird, though it certainly made more mistakes in its new 
cage than in the usual experimental cage, nevertheless sometimes imme- 
diately after leaving cage 1 for cage 2, flew to the right box and tipped 
up the flap. 
From this series of experiments I believe I am justified in forming 
the conclusion that the place the food-box takes is undoubtedly of 
great significance in the formation of habits. At the same time 
however [ thought it possible that other impressions contributed 
to the result as well. 1 therefore decided to find out in how far it 
_ was possible to train the birds by means of another factor of impressions. 
Other factors which may assist in forming a habit. 
I have endeavoured to eliminate the factor of place entirely from 
the series of experiments, which I will now proceed to give. This 
was done by filling a different box with food each time, and thus 
