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THE GERM LAYER DERIVATIVES 



Telencepholon 



Trigeminal ganglion 

 Acuslico-faciolis gangli 

 Glossophoryngeal gangi 



,Vogu5 ganglion 

 Medullofy p'ote 



Mesencepholon 



Optic lobes 



Cerebellum 



Cranial nerve I 



E«ternol nares 

 Nasol tube 

 Lateral appendu 

 Epiptiysis 

 II 

 Eye 



Endolymptiatic duct 

 OtiC capsule 



Vagus (X) 



Lateral line nerve (Xl 



Origin and derivatives of the cranial ganglia. (A) Origin of the cranial 

 ganglia: frontal section. (B) Relation of the crest segments and placodes: 

 transverse section. (C) Relation of the sense organs to the cranial ganglia. 

 (D) Brain, sense organs, and cranial nerves of the 12 mm. tadpole. 



Embryologically the rudiments of all of the cranial nerves are more 

 complex than are the rudiments of the spinal nerves. They are made 

 up of cell masses from the neural crests, from ectodermal patches on 

 the surface of the head, and from cell processes extending out from 

 the ventro-lateral brain neuroblasts. The spinal nerves do not have 

 the surface ectodermal constituent. Following is a summary of the 

 cranial nerves of the frog embryo: 



