56 



PINEAL EYE 



character, its visceral and outer openings bearing grooves 

 and ridges which demonstrate that the pineal structures 

 must not only have been paired, but must have entered 

 the opening in a way which precludes the admission of 

 the epiphysis. It is now, therefore, that the pineal fora- 

 men which has been described in Siluroids * becomes 

 of especial interest, since its contained structures are ap- 

 parently connected with the lateral line system of paired 

 nerves. 



It must for the present be concluded, accordingly, that 

 the pineal structures of the true fishes do not tend to con- 

 firm the theory that the epiphysis of the ancestral verte- 

 brates was connected with a median unpaired eye ; it would 

 appear, on the other hand, that both in their recent and 

 fossil forms, the epiphysis was connected in its median 

 opening with the innervation of the sensory canals of 

 the head. This view, it is now interesting to note, seems 

 essentially confirmed by ontogeny. The fact that three 

 successive pairs of epiphysial outgrowths have been noted 

 in the roof of the thalamencephalon, appears distinctly 

 ^adverse to the theory of a median eye. 



* Dean, N. Y. Rep. of Fisheries., 1891, and Klinckowstrom, Anat. Anz.., 

 1893, vi"> P- 561- 



