134 ARTHUR DENDT. 



the hinder part of the roof of the thalamencephalon. This 

 vesicle, according to Hoffmann, becomes divided by a con- 

 striction into two parts, anterior and posterior, of which the 

 anterior develops into the parietal eye and the posterior into 

 the '' eigentlichen Epiphyse" (= parietal stalk). Later on 

 the parietal eye vesicle no longer lies in the same plane as the 

 "epiphysis," but somewhat obliquely in front and to the 

 right of it. 



As a representative of the second school I may mention 

 Beraneck, who in his later papers (5 and 6) has contended very 

 vigorously for what he terms the individuality of the parietal 

 eye. He maintains that the two vesicles, observed by all who 

 have investigated the subject, originate independently of one 

 another from the brain, and that therefore the parietal eye is 

 not formed from the " epiphysis." In support of this view 

 he lays special stress upon the fact that the nerve of the 

 parietal eye is developed independently of the so-called 

 epiphysis or parietal stalk, and not at the expense of the latter 

 as was formerly supposed. 



In spite of the arguments advanced against Beraneck by de 

 Klinckowstrora (19), who has investigated the development of 

 the parietal eye and " epiphysis " in Iguana, I must declare 

 myself strongly in favour of the "individuality" of the parietal 

 eye, Beraneck (6) has thoroughly argued the question in his 

 reply to de Klinckowstrom, and I think he has hit upon the 

 true explanation of the diversity of opinion in the following 

 passage : — " Ces divergences assez importantes s'interpretent 

 facilement avec l^hypothese que Toeil parietal et Tepiphyse 

 sont des evaginations distinctes du thalaraencephale. En effet, 

 ces deux organes peuvent avoir un developpement simultaue a 

 successif, suivant certaines conditions embryogeuiques, sans 

 que leurs caracteres morphologiques en soient pour cela 

 alteres.^^ 



I have already given my arguments for believing that in 

 Sphenodon the parietal stalk and eye originate indepen- 

 dently. Beraneck (6) believes that the primitive evagination 

 of the brain described by Francotte in Anguis corresponds 



