28 Journal of Comparative Neurology. 



the brain wall ; (2) from the origin and connection of the epiphy- 

 sis with the optic region of the brain, especially with the optic 

 thalamus ; (3) from the morphological similarity of the organ 

 to a primitive optic vesicle ; (4) from the similarity of the per- 

 ipheral relations of the vesicles in selachians, ganoids, and Petro- 

 myzon, and from a peripheral position in amphibians outside of 

 the skull on a level with the eye ; and (5) from the primitive connec- 

 tion of the epiphysis with the nerve bundles (Van Wihje); that 

 the glandula pinealis is the rudiment of an unpaired eye. He 

 adds that if this view is correct, then the epiphysis as a rudi- 

 mentary parietal eye is analogous in function to the unpaired 

 eye of tunicates and perhaps also of Amphioxus. 



Van Wihje 1 (po-84) correcting his earlier statement that 

 in selachians the anterior neuropore corresponds to the pineal 

 gland, says that in birds the neuropore completely disappears in 

 the stage with twenty-eight somites, and the rudiment of the 

 epiphysis appears when twenty-nine somites are present. 



Hoffmann 1 (36-8$) states that in representatives of nearly 

 all classes of vertebrates the epiphysis arises as an evagination 

 of the roof of the thalamencephalon. 



De Graaf (29-86) summarized his work on amphibians and 

 reptiles as follows : 



/. Amphibia. Material. — Siredon pisciformis, Triton cris- 

 tatus, Triton alpestris, Triton taeniatus, Salam. maculosa, Rana 

 esculenta, Rana temporaria, Alytes obstetricans, Bombinator 

 igneus, Bufo cinereus, Hyla arborea. 



(1) The epiphysis arises as a vesicular evagination from 

 the roof of the thalamus where the latter joins the mesencephalon; 

 at the place where it bends around into the roof it is constrict- 

 ed into a stalk. 



(2) Shortly after its appearance the plexiform fundament 

 of the plexus choroideus of the third ventricle is developed 

 from the roof im mediately between the epiphysis and the fore- 

 brain. 



(3) In the Urodela the epiphysis becomes fungiform in the 



'Fide Spencer. 



