POSITION OF OPTIC ANLAGE IN AMBLYSTOMA 



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Fig. 6 A diagrammatic cross section through the brain and optic cups of an 

 early embryo, with all of the median ventral medullary tissue represented as 

 being part of the optic stalks. The future fibers of the optic nerves, shown in red, 

 follow the optic stalks to the median plane where they cross and afterward enter 

 the brain to pursue their course as the optic tracts. The optic cross is entirely 

 beneath and outside the brain. 



Fig. 7 A sketch representing the actual outlines of a cross section through 

 the brain and eyes of a late fish embryo. The optic nerves cross below and out- 

 side the brain and are surrounded by cells derived from the original optic stalks. 



