464 STEFAN KOPEC! 



development or, as I had several times observed, from the re- 

 generated eye. That is to say, when the eye is regenerated all 

 the layers of the imaginal optic ganglion layers are developed 

 quite normally also. 



The layer of the external chiasma (aussere Kreuzung) never was 

 found afterward in the operated specimens. The layer of the 

 internal chiasma and the external medullary layer (innere 

 Kreuzung and ausseres Marklager of Berger) w^ere often but 

 sUghtly developed. The internal medullary (inneres Marklager) 

 was thicker along the longitudinal axis of the brain, thinner along 

 the transverse axis. These anomalies set in a still clearer light 

 the influence exerted by the eye on the development of the imag- 

 inal brain or sensu stricto, of its optic ganglion during its 

 metamorphosis. In one of my previous papers I already urged 

 this opinion, but was unwilling to consider it as proved on account 

 of the small amount of experimental material then at my disposal 

 (cf. Kopec, '13, p. 457). ]My former conclusion as to the 

 dependence of the formation of the brain on the formation of the 

 imaginal eye in insects is now well founded and it finds perfect 

 confirmations in the important investigations of Herbst ('16) on 

 changes in the structure of the optic ganglion in certain Crustacea 

 deprived of the eyes. 



In connection with the results discussed here I wish to remark 

 briefly that in the development of both gangUa of the head a 

 certain mutual dependence may be observed. In microscopical 

 sections of brainless specimens we are at once struck by the ex- 

 ceedingly meager development of the suboesophageal nervous 

 gangha. Its normal development is evidently correlated to some 

 extent with the formation of the brain. The removal of the 

 larval suboesophageal ganglion, on the contrary, has no visible 

 effect on the formation of the imaginal brain. 



SUMMARY 



1. The eyes of the moths develop in complete independence of 

 the brain and the suboesophageal ganglion. The brain exerts 

 only a regulating influence on the direction of the nerve fibers 

 going from the retina of the eye to the optic ganglion. 



