26 ARTHUR DENDY. 



half of the '' pineal body " being supplied by fibres which come 

 from the habennlar ganglion of the opposite side. This 

 may be true in certain types, but as Cameron himself 

 recoo-nises, there is no evidence for any sucli decussation 

 in the Lampreys, where each of the parietal sense organs is 

 undoubtedly innervated from the habenular ganglion of its 

 own side. 



By no means the least interesting evidence in favour 

 of the paired origin of the parietal sense organs is that 

 afforded by the study of fossil fishes, the history of which 

 affords a curious illustration of the influence of what we 

 may call the " Cyclopean theory " of the pineal eye. The 

 following quotation from Bashford Dean's work (11) on 

 'Fishes, Living and Fossil' will serve to make this clear, 

 and at the same time to indicate the character of the 

 palseontological evidence in question: ''The evidence, how- 

 ever, that the median opening in the head shields of ancient 

 fishes actually enclosed a pineal eye is now felt by the 

 present writer to be more than questionable. The remarkable 

 pineal funnel of the Devonian Dinichthys (fig. 134) is evi- 

 dently to be compared with the median foramen of Ctenodus 

 and Palasdaphus (= SSirenoids,' p. 122); but this can no 

 longer be looked upon as having possessed an optic function, 

 and thus practically renders worthless all the evidence of a 

 median eye presented by fossil fishes. Tt certainly appeared 

 that in the characters of the pineal foramen of Dinichthys 

 there existed strong grounds for believing that a median 

 visual organ was present. . . . But the function of this 

 pineal foramen, unfortunately for speculation, could not have 

 been optical. It occurs in a fish (Titanichthys) closely 

 related to Dinichthys, and, as the writer has recently found, 

 is of a distinctly paired character, its visceral and 

 outer openings bearing grooves and ridges which demon- 

 strate 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 nnist, 

 for the present, be concluded, accordingly, that the pineal 



