341 
5. Encouraged by the result of the series of experiments de- 
scribed so far, I resolved on employing a more subtle mark of 
distinction. I again employed white flaps for my purpose. The 
empty boxes had a black square, the food box a black disc of about 
the same size. The result of this series of experiments was not suf- 
ficiently convincing. Nevertheless I had the impression, when the 
siskin went to the box with the round disc, that this was not always 
entirely a matter of chance. 
SUMMARY. 
1. The result of my experiments is in corroboration with those 
of Buyrenpijk, that the place a food-box takes in the midst of other 
(empty) boxes, is of great importance for teaching birds to form 
the habit of eating from that box. 
2. In addition there are however numerous other visual factors 
which may tend to develop this habit. 
