56 



TROPISMS 



legs on the side of the blackened eye are more extended 

 than normally and spread farther apart. 9 - The body may 

 tilt as far toward the side of the unblackened eye as to 

 press the legs to the table (Fig. 20). There is sometimes a 





Fio. 20. —Robber fly with right eye blackened, seen from above as in Fig. 19. The 

 body tilts over to the left side so that only the right eye is visible from above. Position of 

 legs changed in such a way as to make motion toward left possible, toward right impossible. 

 (After Garrey.) 



tendency on the part of the body of the animal to become 

 slightly concave toward the side of the unblackened eye. 



Garrey found also that the same changes take place 

 when one eve receives a stronger illumination than the 



a Figs. 19 to 22 and 27 were drawn from photographs kindly given to 

 the writer for this purpose by Professor Garrey. The draughtsman was 

 unfortunately not familiar with the anatomy of insects, which accounts for 

 shortcomings in the drawings, which, however, have no bearing on the prob- 

 lem for which the drawings are intended. 



