394 



Nachdruck verboten. 



On the Origin of the Pineal Body as an Amesial Structure, 

 deduced from the Study of its Development in Amphibia. 



By Dr. John Cameron, University of St. Andrews, Scotland. 



The following is a summary of the main conclusions which have 

 been arrived at in this research. A comparison with the results of 

 observers in other Vertebrate classes has also been given. 



1) The epiphysis in certain types of Amphibia (Rana, Bufo, Tri- 

 ton) arises in the form of two primary out-growths from the roof of 

 the fore-brain. These are placed, one on either side of the mesial 

 plane. 



2) The outgrowth which is situated to the right of the middle 

 line disappears at an early stage of development by blending with the 

 left outgrowth. 



3) The latter shows the most active growth, and the effect of 

 this in most cases is to cause the epiphysial opening to become si- 

 tuated to the left of the mesial plane. The left outgrowth is there- 

 fore the more important of the two in Amphibia. 



4) Dendy 1 ) describes right and left epiphysial vesicles in em- 

 bryos of Hatteria. The left gives rise to the pineal eye while the 

 right retains its attachment to the roof of the fore-brain, and forms 

 the epiphysial stalk. 



5) During the later stages of development evidences of the bi- 

 lateral origin of the Amphibian epiphysis are found; for the portion in 

 relationship to the superior commissure (fibres from which form the 

 nerve supply of the pineal eye), along with the part distal to this 

 together correspond to the pineal eye of Hatteria, while the remainder 

 of the proximal portion, which communicates with the thalamen- 

 cephalon, corresponds to the epiphysial stalk of Hatteria. 



6) The presence of right and left primary epiphysial outgrowths 

 has also been demonstrated by Beraneck 2 ) in Lacertilia and by Hill 3 ) 

 in Fishes; and Locy 4 ) describes the epiphysis of Elasmobranchs as 

 developing from a pair of united accessory optic vesicles. 



1) Quart. Journ. Microsc. Sc, Vol. 42, p. 111. 



2) Anatom. Anzeiger, Bd. 7, p. 674, und Bd. 8, p. 669. 



3) Journ. of Morphology, Vol. 5, p. 503, and Vol. 9, p. 237. 



4) Anatom. Anzeiger, Bd. 9, p. 169, 231 und 486. 



