Sorensen, Study of Epiphysis and Roof of Diencephalon. 6 1 



of the primitive epiphysis but a special organ arising from a 

 diverticle developed directly from the roof of the diencephalon, 

 and is related to the epiphysis by position rather than by deri- 

 vation. He denies the homology of the distal part of the 

 epiphysis which forms" a diverticle in Cyclodus, with the parietal 

 eye of Lacerta, Anguis and other lizards, and also the homolo- 

 gy of the pineal eye with the distal vesicle of the epiphysis of 

 the selachians. In concluding Beraneck gives seven points of 

 which the following are the first and fifth. First : The parietal 

 eye cannot be considered as a simple diverticle of the pineal 

 gland. In the case of Lacerta and Anguis it constitutes an in- 

 dependent organ which proceeds from the thalamencephalon 

 like the epiphysis, but is developed parallel to it and not from 

 it. Fifth : The epiphysis is derived from an evagination of the 

 thalamus. It does not represent the stalk of the parietal eye. 

 It is an organ sui generis, whose first funtions are still unknown. 

 It does not reveal marked sensorial characteristics as in sela- 

 chians where it is highly developed. The epiphysis appears to 

 be continuous throughout the series of vertebrates and is phy- 

 logenetically as old as the parietal eye, for it appears as early if 

 not earlier in the ontogeny. In Anguis Beraneck discovered a 

 nerve entering the retina of the eye. Between the 9th and 14th 

 days a nerve unites the eye to the roof of the diencephalon. 

 In a later article (j-'93) Beraneck replied to Klinkowstrom's 

 article of the same year (^2-93) and maintains that in Lacerta 

 there are two diverticles from the thalamus, the anterior giving 

 rise to the parietal organ, while the posterior becomes the epiph- 

 ysis. He further states that in lizards the parietal organ is not 

 derived from the pineal gland, while in Anguis fragilis it is so 

 derived. 



C. von Kupffer (4.5-^4), whose article did not reach me in 

 time to give his description, figures the roof of the diencephalon 

 in Ammoccetes planed and shows the following relations : 



(1) Post commissure. (2) Pineal stalk with ep. 2 attached. 

 (3) Segment of the roof. (4) Supra-commissure. 2 (5) Segment 

 of the roof. (6) Supra-commissure. 1 (7) Epiphysis. 1 



