52 FREDERICK TILNEY A XI) LUTHER F. WARREN 



calm. In the embryo of S<tl///<> fotitinali*, IIill IMJ found the 

 unlade of tlie ej)i])hyseal complex to be a double evaluation 

 which communicated with the third ventricle by means of a 

 common canal. Of the two sacs thus formed the posterior was 

 much the larger. This, the anlage of the pineal organ, was 

 situated immediately in front of the posterior commissure and 

 in the mid-line, while the anterior evagination was close to the 

 left as if both sacs were related to the roof-plate by a common 

 stalk and later the anterior one was detached from the connec- 

 tion. Hill concluded that there are two epiphyseal outgrowths 

 from the roof in teleosts of which the more anterior vesicle, both 

 in teleosts and in Aniia, is homologous with the parietal eye of 



PC Pp 



Fig. 19 Anlage of the epiphyseal complex in a 37-days old embryo of Salmo 

 fontinalis, according to Hill, 1894. 



Pp., parapineal organ; Pt>., pineal organ. 



Lacertilia. He thinks it probable that the two vesicles in their 

 primitive position were side by side and believes it likely that 

 the anterior vesicle is the homologue of the parapineal organ in 

 Pelromyzon. Hill also found this condition in embryos as well 

 as in a two-year-old salmon. 



Dendy 86 maintained that the double evagination in the epi- 

 physeal anlage occurs in Amia as well as teleosts. Of these two 

 vesicles the right gives rise to the epiphysis while the left sepa- 

 rates from the brain a.nd degenerates. Cattie, 60 examining the 

 adult condition in plagiostomes, ganoids, and teleosts, came to a 

 conclusion similar to the hypotheses of (loette 11 - and Van Wijhe- 107 

 that the pineal body was derived as the final product of closure 

 at the anterior neuropore where the ectoderm of the epidermis 



