WALTER E. GARREY 115 



body in which the anterior and posterior ends of the insect meet in a 

 ring. 



Efect of Blackening Upper Half of One Eye and Lower Half of 

 Other Eye. — By blackening the upper half of one eye and the lower 

 half of the other eye of Proctacanthus , one obtains a combination of 

 'the effects described in the preceding experiments. This procedure 

 emphasizes the fact that different parts of the eye control the tonus 

 of entirely different groups of muscles on the two sides of the body. 

 The resulting tonus changes produce a most bizarre type of asymmetry 



Fig. 7. Robber fly with the upper part of the left eye and the lower part of the 

 right eye blackened. Body tilted to the right and twisted on its long axis. Head 

 rotated to the right. Left anterior leg and right posterior leg extended. Right 

 anterior leg and left posterior leg flexed. Moves in circles to the right. 



in the position of the legs at rest, and in the character of the move- 

 ments (Fig. 7). Thus with the lower half of the right eye and the 

 upper half of the left eye blackened, there is flexion of the anterior 

 leg of the right side and extension of its mate on the left side. There is 

 flexion of the posterior leg on the left side and extension of the right 

 posterior leg. The whole body is thus twisted on its long axis. The 

 head is depressed and rotated down on the right side, that is toward 

 the blackened area of the eye of that side, up on the left side so that 

 the sagittal plane of head is horizontal. The tail end is twisted down 

 on the left side. 



