94 



Journal of Comparative Neurology. 



in embryos. The plexus development is excessive but follows 

 familiar lines. The roof of the diencephalon cephalad of the 

 supracommissure is wholly modified in this way. The caudal 

 part follows the epiphysis closely while the cephalic portion 

 forms a distinct sac with numerous plexiform diverticles. From 

 its lateral aspect a rich plexus is thrust into the ventricle. 



The whole structure becomes so complex that it is little 

 wonder that Stieda thought the whole organ a mass of plexus 

 and considered the epiphysis absent. 







Description of Figure. Portion of a transection of the brain of Phrynosonia 

 at the supracommissure. The curved epiphysis, Pp. II, is twice cut while the 

 paraphysis, Pp. I, occupies the concavity left by the curvature. Par n, parietal 

 nerve springinglfrom the supracommissure ; III. third ventricle; op. tr. optic 

 tract. 



TJie Jiabcna and related stnictures require closer analysis 

 than is customary. We have elsewhere shown that the body 

 frequently so-named is compound. The habena proper consists 



