IMPORTANCE OF SCENT. 259 
then twisted as shown in Fig. 19. The bricks and tunnel 
being also rearranged so that they were exactly in the 
same direction as before, but the board having been moved, 
the line d e was now outside them. This change, however, 
did not atall discom- Fig. 19. 
pose the ants; but 
instead of going, as 
before, through the 
tunnel and between 
the rows of bricks 
to a, they walked 
exactly along the 
old path to e. 
I then arranged 
matters as before, 
but without the tunnel and with only three pairs of 
bricks (Fig. 20). When an ant had got quite used to the 
path d to e, I altered Fig. 20, 
the position of the 3 
bricks and food, as di 
shown in Fig. 21, mak- I | 
ing a difference of 8 
inches in the position HH 
of the latter. The ant HL 
came as before, walked 
up to the first brick, 
touched it with her antennz, but then followed her old 
line to a. From there she veered towards the food, and 
very soon found it. When she was gone, I altered it, 
