1903 - 4 .] Origin of the Epiphysis Cerebri in the Chick. 
165 
(2) The right primary evagination blends with the left at an 
early stage of development to form a unified structure. 
(3) These observations correspond for the most part with those 
already made by the author in the case of the Amphibia. They 
also agree in many ways with those of Beraneck, Dendy, Gaskell, 
Hill and Locy in other classes of the Yertebrata. As a result of 
this, it is evident that in the four lower Vertebrate classes the 
epiphysis cerebri arises as a bilateral, and not as a mesial structure. 
(4) It is probable that the ancestors of Vertebrates possessed a 
pair of parietal eyes, and not a single unpaired structure. 
(4) Literature. 
Literature consulted in connection with the present research 
(1) Balfour, F. M., Comparative Embryology , vol. ii., 1881. 
(2) Beard, J., “ The Parietal Eye in Fishes,” Nature , vol. 
xxxvi., 1887, pp. 246 and 340. 
(3) Beard, J., “ The Parietal Eye of the Cyclostome Fishes,” 
Quart. Jour. Micr. Sci., vol. xxix., 1888, p. 55. 
(4) Beraneck, E., “ Sur le nerf parietal et la morphologie 
du troisieme oeil des Vert6bres,” Anal. Anz., Bd. vii., 1892, 
s. 674. 
(5) Beraneck, E., “ L’individualite de l’ceil parietal,” Anat. 
Anz., Bd. viii., 1893, s. 669. 
(6) Burckhardt, B., “ Die Homologien des Zwischenliirndaches, 
und ihre Bedeutung fur die Morphologie des Hirns bei niederen 
Vertebraten,” Anat. Anz., Bd. ix., 1894, s. 152. 
(7) Burckhardt, B., “Die Homologien des Zwischenliirndaches 
bei Beptilien und Vogeln,” Anat. Anz., Bd. ix., 1894, s. 320. 
(8) Cameron, J., “On the Origin of the Pineal Body as an 
Amesial Structure, deduced from the Study of its Development in 
Amphibia,” Anat. Anz., Bd. xxiii., 1903, s. 394. Also in Proc. 
Roy. a Soc. of Edin., vol. xxiv., 1903, p. 572 ; and in Proc. Scot. 
Micr. Soc., vol. iii., 1903. 
(9) Cameron, J., “ On the Bilateral Origin of the Epiphysis in 
Amphibia,” Proc. of Brit. Assoc., 1903, Section D. 
(10) Dendy, A., “Summary of the Principal Besults obtained in 
a Study of the Development of the Tuatara ( Sphenodon punctatus ),” 
Proc. Roy. Soc., vol. lxiii., 1898, p. 440. 
