EXPERIMENTS WITH COLOURED GLASSES. 189 
9, Green. Yellow. Red. Violet. 
60 35 €5 0 
10. Violet. Green. Yellow. Red. 
1 50 40 70 
ll. ~ Red. Violet. Green. Yellow. 
50 2 50 60 
12. Yellow. Red. Violet. Green. 
35 55 6) 70 
Adding these numbers together, there were, in the 
twelve observations, under the red 890, under the | 
green 544, under the yellow 495, and under the violet 
only 5. The difference between the red and the green 
is very striking, and would doubtless have been more 
so, but for the fact that when the colours were trans- 
posed the ants which had collected under the red 
sometimes remained quiet, as, for instance, in cases 
7 and 8. Again, the difference between the green and 
yellow would have been still more marked but for the 
fact that the yellow always occupied the position last, 
held by the red, while, on the other hand, the green 
had some advantage in coming next the violet. In 
considering the difference between the yellow and 
green, we must remember also that the green was 
decidedly more opaque than the yellow. 
The case of the violet glass is more marked and 
more interesting. To our eyes the violet was as opaque 
as the red, more so than the green, and much more so 
than the yellow. Yet, as the numbers show, the ants 
