94 ROBERT STANLEY McEWEN 
Furthermore a record was kept in such a way that it was possible 
to see in how many trials a given color came out first, second, 
or third. It is evident that in this scheme, since every color was 
used in every test, the effect of previous tests would not change 
the relative value for any color in any given test. On the other 
hand the possible effect of the arrangement of colors in any given 
test is overcome by altering the arrangement every test. Finally, 
the method of recording gives not only the average of all the trials, 
but an analysis of individual trials. It, therefore, seems that a 
tolerably clear-cut result obtained in this way may reasonably 
be supposed of some significance. 
This method was now applied in testing a series of mutant eye 
colors as well as the normal stock. The eye colors were as fol- 
lows: white, an eye entirely lacking in pigment; tinged, almost 
white, but containing the lightest shade of red; eosin, a reddish 
yellow somewhat darker in the females; vermilion, a very good 
sample of this color; normal; and sepia. The last named color 
is virtually maroon on hatching, but grows darker with age until 
at five days it is practically black. The results from the tests 
on these stocks are summarized in tables 23 to 28. Graph 5 is 
based on the results for each eye color as indicated in groups A 
and B combined. Since there is no apparent sex differentiation 
as regards reaction to varied wave lengths, the graph has been 
constructed from the average male and female indices in every 
case. 
It is evident from these tables that in the case of all colors 
lighter than normal, the general tendency is for the order of ef- 
fectiveness to be violet, green, red. There are, however, three 
exceptions. First in group A of white eyed males, the red is 
ahead of the green both in the average index and in the number 
of tests in which this occurs. This case is more than oftset, 
however, by group B, so that in the average of the two the order 
of colors is as stated above. It should be mentioned, moreover, 
that white eyed insects are extremely erratic even for Dro- 
sophila. It is quite usual for them after making a few con- 
sistent trips up the tube to become very much excited and to 
simply buzz about convulsively. The second exception is that 
