526 



THE EYE IN EVOLUTION 



Fig. 696.- — Fkontal Section of the Cerebral Ganglion and Optic Lobes of 



THE Locust, Locust a. 



Showing descending tracts to the nerve cord (reconstructed). C, central body ; 

 CP, corpora pedunculata ; CV, corpora ventraha ; D, deuterocerebrum ; DF, 

 descending tract from deuterocerebrum ; EF and EFX, ipsilateral and contra- 

 lateral fibres from optic lobes ; LG, lamina ganglionaris ; ME, external medulla ; 

 MI, internal medulla ; ON, ocellar nerve ; PF and PFX, ipsilateral and contra- 

 lateral fibres from corpora pedunculata ; TF, descending tract from tritocerebrum. 



With the incisions indicated by numbered black pointers, the following effects 

 on the visual responses were noted : 1, in the ventral region and posterior aspect of the 

 optic peduncle, the crossed responses were abolished ; 2, on the dorsal and anterior 

 aspect of the optic peduncle, the ipsilateral responses were weaker ; 3, between the 

 two halves of the protocerebrum ventrally, the crossed responses were abolished bi- 

 laterally; 4, between the two halves of the protocerebrum dorsally, no effects on the 

 visual responses were found (R. C. Satija, J. Physiol.). 



ganglia was well demonstrated by Jordan (1910) who showed in the crab 

 that the circus movements ceased if the cut end of the connective were 

 electrically stimulated. 



The exaggeration of reflex reactions after removal of the cerebral ganglion is seen 

 in the elicitation of responses to stimuli normally vs^ithout effect and the continuation 

 of movements (such as cleaning movements of the legs) uninterruptedly for hours 

 (Bethe, 1897 ; Roeder, 1937 ; and others). In decapitated females of Bomhyx, 

 oviposition can be induced mechanically before mating and persists until all the eggs 

 have been laid, merely by pressing the ovipositor (McCracken, 1907) ; the same type 

 of response is seen in the stinging reflex of the bee (v. Buddenbrock, 1937). In the 

 same way when the female praying mantis devours her doomed mate head-first, his 

 copulatory activity increases manyfold in violence and apparent enthusiasm when 

 she has disposed of his cerebral and sub-cesophageal ganglia (Roeder, 1935). 



The .' tivities of Arthropods are essentially reflex in nature, controlled 

 with ainaz >; precision by the ganglionic centres ; when the eye of the 



