REACTIONS TO LIGHT AND GRAVITY IN DROSOPHILA 79 
right angles was nevertheless near its foot. It was recognized 
that this method was unreliable when we attempted to compare 
the gravity reaction of flies which were phototropic with that 
of those which were not. Thus, two sets of flies, one photo- 
tropic and the other not, but possessing an equal amount of 
Fig. 2. A, Normal insect. B, Specimen of ‘curled’ stock. C, Specimen of ‘vestigial’ 
stock. D, Specimen of ‘strap’ stock. 
