PAPERS OX BIOLOGY AND AGRICULTURE 



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the floor of the brain at the chiasma of the two normal 

 optic nerves. This relationship will be discussed in more 

 detail in the section of the nervous system in the sequel. 



Fig 10 



It is quite evident that these accessory external sen- 

 ary appendages have developed through a fusion of the 

 embryonic structures in such a way that the left organ 



sor 



