PINEAL EYE IN LACERTILIA. 173 



rudiment is situated where the "Zwichenhirn" and the "Mittel- 

 hirn " unite. He states further : '' Die vordere Ausbruch- 



^" tung der Epiphysis schniirt sich volstandinge von den Hirndach 

 ab ; sie bildet eine kleine, runde, selbstandige Blase von platt- 

 gedruckter Form und stellt die Anlage des sogenannten Ley- 



> digschen Organes von Strahl hat dieses zuerst erkannt und Ji 

 ich kann seinen Befund bestatigen." ->- 



The most recent, as well as most interesting work upon the 

 pineal gland is that of de Graaf / to whom is certainly due the 

 merit of having first clearly shown that in one particular 

 animal (Anguis fragilis) the pineal gland actually is 

 modified into a structure comparable to an Inverte- 

 brate eye. He says: " Dem zufolge gleicht bei Anguis 

 fragilis das ganze abgeschniirte Stiick etwa dem Auge eines 

 hoher entwickelten wirbellosen Thieres, wie uns z. B. Cephalo- 

 poden, Pteropoden und Heteropoden bekannt ist." 



According to de Graaf the Epiphysis, in Amphibia and 

 Reptiles (Lacertilia), arises as a hollow outgrowth of the 

 thalamencephalon,^ never passing much beyond this stage in 



J Urodeles (PI. %, figs. 13 — 18), but in Anura and Lacertilia 

 becoming divided into two parts. In the former, growth 

 results in the formation of a distal bladder-shaped portion and 

 a solid stalk connecting this with the brain-roof (PI. 3, figs. 

 22 — 29) ; the distal part is gradually constricted ofi" from the 

 stalk and comes to lie excerebrally and finally without the 

 cranium and close beneath the skin ; the stalk, on the other 

 hand, lies permanently within the brain membranes and thus 

 enclosed in the skull cavity. 



In the adult, he says, the cut-off portion of the epiphysis 

 (" Stieda's gland ") lies embedded in the cutis close beneath 

 the epidermis, is surrounded by a specially close-woven case, 



1 (a) " Zur Anatomic und Entwickelung der Epiphyse bei Amphibian 

 und Reptilien," ' Zool. Anzeig.,' 29th March, 1886. {b) ' Bijdrage tot de 

 liennis van den bouw en de ontwickkeling der epiphyse bij Amphibien en 

 Heptiiien,' van Henri W. de Graaf, Leiden, 1886. 



2 He thus differs from Goette in regarding the epiphysis as a secondary 

 outgrowth, having nothing to do with the neuropore. 



