BRAIN AND EYES OF LEPIDOPTERA 461 



arrangement (fig. 2, c.n.h.). We get the impression that, in the 

 ontogenetic development of the eye, the brain or the optic gan- 

 glion has a determining influence on the direction of these 

 nervous bundles. These anomalies might, however, just as well 

 be attributed to different modes of growing together, which 

 took place. during cicatrization of torn larval nervous bundles. 

 The crucial fact here was the behavior of moths deprived of the 

 germs of their imaginal eyes, these germs being subsequently 

 regenerated. However, in these cases the larval nerve-bundles 

 underwent analogous tearing or concrescenses during operation, 

 yet the arrangement of the single as well as compound bundles 

 was quite normal. Consequently, during the formation of the 

 imaginal eye the brain (or the optic ganglion) has an influence on 

 the direction of the nerve-bundles proceeding from the retina to 

 the optic ganglion. 



The other layers situated under normal conditions between the 

 layer of nerve-bundles and the imaginal optic ganglion, which 

 are considered by Berger to be a modified part of the optic gan- 

 glion, arise through transformation of the larval optic ganglion 

 which was removed together with the larval brain. In view of 

 such anatomic-histological conditions it becomes quite clear that 

 only the nerve-bundle layer described above is present besides the 

 eye sensu stricto in the brainless moth. 



The simultaneous removal of brain and of the suboesophageal 

 ganglion has convinced me of a quite similar independence of the 

 evolution of the eye from the second ganglion situated in the 

 head. Stress must be laid on the fact that in no case was I 

 able to detect any processes of regeneration of the removed 

 brain or suboesophageal ganglion. Thus the development of the 

 imaginal eye of moths is quite independent of the presence of 

 the brain and the suboesophageal ganglion. 



