250 INGENUITY IN BUILDING NESTS. 
me as very ingenious. The same expedient was, more- 
over, repeated under similar circumstances by the 
slaves belonging to my nest of Polyergus. 
The facility or difficulty with which ants find their 
way, while it partly falls within the section of the 
subject dealing with their organs of sense, is also 
closely connected with the question of their general 
intelligence. 
Partly, then, in order to test how far they are 
guided by sight, partly to test their intelligence, I 
made various observations and experiments, the ac- 
companying woodcuts being reduced copies of tracings 
of some of the routes followed by the ants during the 
course of the observations. 
I may here note that the diagrams Figs. 12-17 are 
careful reductions of large tracings made during the 
experiments. Though not absolutely correct in every 
minute detail of contour, they are exact for all practical 
purposes. As the ants pursued their way, pencil-mark- 
ings in certain instances, and coloured lines in others, 
were made so as to follow consecutively the paths 
pursued. 
Experiment 1.—February. On a table communi- 
cating with one of my nests (see Fig. 12)I placed upright 
a common cylindrical lead pencil } inch in diameter 
und 7 inches long, fastened with sealing-wax to a 
penny piece. Close to the base of the pencil (4) I 
brought the end of a paper bridge (B) leading to the 
nest, and then placed a shallow glass with larve at c, 
