REACTIONS TO LIGHT AND GRAVITY IN DROSOPHILA vl 
TABLE 10 
Group A. Temperature 23° 
GRAVITY LIGHT 
Males Females Males Females 
Third test, before wing removal........ 46.6 30.0 88.3 84.1 
Hourchtest-patuern removal. s-..cs-e eee - 43.3 40.0 116 6.6 
der method I, the age of the insects being unknown. The appa- 
ratus was exactly the same as that described in connection with 
the effect of removing the wings at different times after hatching. 
Five groups of flies were employed in the first series of tests. 
In the case of the first two groups only half of the wings were 
removed throughout the tests, while in the case of the last three 
groups one or two tests were given with half the wing removed, 
and then a second operation was performed in which three-fourths 
of the total wing was taken. Table 11 summarizes the results. 
It appears that though the insects are very erratic and vary 
much from time to time, those animals which had had the wing 
completely removed, with one single exception, made lower rec- 
ords than any made by flies with only half of the wings removed. 
These experiments are unsatisfactory, however, in failing to show 
what, if any, effect the removal of half the wing has. Later on, 
therefore, another set of experiments was devised to answer this 
question. In this case method II was used with the improved 
apparatus. Likewise, the alternating gravity trials were intro- 
duced as a control. In short, the general method was precisely 
similar to that employed in the proof that wing removal has 
a specific effect on the reaction to light (table 9). 
Four groups of flies were selected at random from the bottles 
and run through the tests. The flies were then etherized and 
treated in the following way. Group I, which contained nine 
males and ten females, had made the lowest record and was re- 
stored to the vials without operation. Group II, which con- 
tained ten males and eleven females, and had made next to the 
lowest record, had only the tip ends of the wings removed. 
Group III, which contained ten males and nine females and had 
the second best record, had one-half of the wings cut off, and 
