Sorensen, Study of Epiphysis and Roof of Diencephalon. 3 1 



the two structures beyond peradventure. If we recall, further 

 that in the Stegocephala (Labyrlnthodonta) from the Carbon- 

 iferous, Permian and Trias, in Branchiosaurus gracilis Cred., B. 

 salamandroides Fritsch, Peleosaurus laticeps Cred., Archego- 

 saurus latirostris Jordan, Dolichosoma longissimum Fritsch, 

 Acanthostoma vorax Cred., etc., an aperture is present in the 

 parietal suture, which in its position corresponds perfectly to 

 that of the sauriens of the present day, we are driven to the 

 conclusion that the epiphysis in the progenitors of the present 

 animals must have played an important role and perhaps has 

 functioned as an organ of sense still unknown to us. 



W. Baldwin Spencer (83-86) in his interesting paper 

 on the "Pineal Eye in Lacertilia, " draws the following conclu- 

 sions from his work : 



(1) Our present knowledge is not great enough to allow 

 us in Amphioxus, to homologize any structure either with the 

 tunicate azygos eye or with the epiphysis. 



(2) The epiphysis of higher Chordata is the homologue 

 of the larval tunicate eye. 



(3) The pineal eye is produced as a secondary differentia- 

 tion of the distal part of the epiphysis. 



(4) There is not sufficient evidence to prove or disprove 

 the existence of the organ within the group Pisces ; it was pres- 

 ent in extinct Amphibia, and is found among living forms only 

 in Lacertilia. 



(5) In all forms at present existing it is in a rudimentary 

 state, and though its structure is better developed in some than 

 in others, it is perfectly functional in none. 



(6) It was present most highly developed in (1) Extinct 

 Amphibia (Labyrinthodonta), and (2) The large group of extinct 

 forms (as Icthyosaurus, Plesiosaurus, Iguanodon, etc.) which 

 may be regarded as ancestors alike of living Reptilia and Aves. 



(7) The pineal eye may probably be most rightly consid- 

 ered as peculiarly a sense organ of pre-Tertiary period. 



Beard (ga-'SS) studied the parietal eye from the morpho- 

 logical standpoint and made the following important observa- 

 tions : In Ammoccetes he found black pigment in the parietal 



