REACTIONS TO LIGHT AND GRAVITY IN DROSOPHILA 97 
TABLE 25 
Hosin eyed flies 
Group A 
AVERAGE 
SEX V G R 
[ Sex Violet Green Red 
Ist | 4 1 0 | Male..... ; 93 .5 87 9 70 .0 
Male..... 2de| Zar db 0 Female... 89 .5 85 .7 70.0 
3d | 0 0 6 
ise |S 0 0 
Hemalene< | 20) dat | 6b .0 Male 
30810 0 6 
fa. Tied once Feimale a. Tied once 
\b. Tied once ~~ \b. Tied once 
Group B 
lat} WhO OMUMele..... |. 2400.0 0 || Waodecen) |) 71.8 
Male..... 2de)|2a7| 6b) |) OF Hemale..- 96 .2 92.0 70.8 
Sada Olen Om 
Ist 5 1 0 . P 
Female..{|2d]}1 | 5 | 0 Malle {ies ae 
Sr Ome Ol 6 
Groups A and B combined 
Isr| 8 1 0 Male..... : 96.7 91.3 70.9 
Male..... 2d | 4a j1lb | 0 Female... 92.8 88.8 70.4 
sd |0 0 12 
(Gets ta |lOnmlp a 0 
Female ..<| 2d | 2a |11b| 0 Male 
3d | 0 QO |12 
fa. Tied three 
\b. Tied three 
fa. Tied once 
\b. Tied once 
Female 
In order to discover a possible cause for the phenomenon just 
described, sections of the eye were made and examined micro- 
scopically. As expected, these sections showed that the pigment 
which imparts to the organ its color, is simply the pigment 
usually found surrounding the rhabdomes in the compound eye 
of arthropods. This pigment so far as its function is known, is 
supposed to be of a protective nature, placed so as to absorb all 
rays of light which do not fall directly parallel to the axis of the 
rhabdome in question. Of course, in cases such as we have un- 
der consideration the pigment is not black but colored, and: will 
consequently reflect light of a certain wave length. At first, 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 25, No. 1 
