178 



. epiphysis. He takes the view that the pineal eye is the highly 

 differentiated distal end of the epiphysis. 



Beraneck has recently described and figured the nerve of the 

 pineal eye in Anguis. He shows in this form, that the eye-capsule 

 is entirely distinct from the epiphysis, and that it has an independent 

 nerve supply, arising from the brain, but in no way connected with 

 the epiphysis. He draws the conclusion that the pineal eye and the 

 epiphysis are independent structures. 



In Elasmobranchs, as several investigators have shown, there is 

 no eye-capsule at all, but the distal end of the epiphysis is enlarged. 

 Between this condition and the condition in Anguis we have in some 

 one animal or another, nearly every gradation represented. 



It has been shown in several forms that there are at least two 

 epiphysial outgrowths (Letdig, Selenka, Hoffmann and Hill). Hill 

 has shown the way in which two vesicles arise in Teleosts, and, further, 

 that in Coregonus albus, the posterior one persists while the anterior 

 one disappears. 



Now can these different observations be harmonized and reduced 

 to a basis of agreement on any evidence so far adduced ? I think 

 the suggestion for uniformity of interpretation is contained in the facts 

 I have made known. I have shown the presence in embryonic deve- 

 lopment of two clearly defined accessory vesicles. Their presence in 

 such a distinct form has some significance. Whether in the adult, they 

 are highly differentiated, rudimentary or even disappeur does not ex- 

 press so much as their actual presence on the cephalic plate. There 

 presence so clearly marked is evidence, that they must, sometime, have 

 been of use, either in ontogeny or phylogeny. We have two pairs of 

 these embryonic organs, in addition to the lateral eyes, and we have 

 thus actually present, in this animal, the material to supply two distinct 

 outgrowths both visual in character. 



Beraneck, after reviewing the evidence, can find no reasonable 

 explanation for and epiphysis, distinct and independent from the pineal 

 eye, and he, therefore, draws the conclusion that the epiphysis is an 

 independent structure of whose function we know nothing. He says: 

 "L' 6piphyse derive aussi d' une evagination du cerveau intermediäre; 

 eile ne represent pas le pödicule optique de l'ceil parietal. C'est un 

 organe sui g6n6ris dont les functions premieres sont encore inconnues; 

 il ne revele pas de characteres sensoriels marques, meme chez les 

 Selaciens chez lesquels il est tres developp6" *). 



de Klinckowström 2 ), in criticising his position, has shown, by 



1) 1. c, p. 689. 



2) Anat. Anz., Vol. VIII, March 1893, p. 289. 



