The Mental Life of the Monkeys 181 
which held in a catch at its top. This nail was fastened 
to a wooden knob (1 by 5 by .375) which lay in a depression 
at the top of the box. Only when the bolt had been 
drawn and the plug and knob pulled, could the door be 
opened. 
Box Gamma (wind) was 10 by 10 by 13 inches with its 
door held by a wire fastened at the top and wound three 
times about a screw eye in the top of the box. By unwind- 
ing the wire the door could be opened. 
Box Delta (push back) was 12 by 11 by 10 inches. Its 
door was held by a wooden bar projecting from the right 
two inches in front of it. This bar was so arranged that 
it could be pushed or pulled toward the right, allowing the 
door to fall open. It could not be swung up or down. 
Box Epsilon (lever or push down) was 12 by g by 5 inches. 
At the right side of its front was a hole $ inch broad by 1} 
inches up and down. Across this hole on the inside of the 
box was a strip of brass, the end of one bar of a lever. If 
this strip was depressed ¢ of an inch, the door at the extreme 
left would be opened by a spring. 
Box Zeta (side plug) was 12 by 11 by roinches. Its door 
was held by a round bar of wood put through a hoop of 
steel at the left side of the box. This bar was loose and 
could easily be pulled out, allowing the door to be opened. 
Box Theta was the same as KK except that the door 
could be opened as soon as the bolt alone was pulled or 
pushed up. 
Box Eta was like Alpha save that the object at the back 
of the box to be pulled was a brass ring. 
Apparatus QQ (chute) consisted of a lever mechanism so 
arranged that by pushing in a bar of wood } to } an inch, 
a piece of banana would be thrown down a chute into the 
cage. The apparatus was placed outside the cage in such a 
