572 Proceedings of Royal Society of Edinburgh. [sess. 
On the Origin of the Pineal Body as an Amesial 
Structure, deduced from the study of its Develop- 
ment in Amphibia. 1 By John Cameron, M.B. (Edin.), 
M.R.C.S. (Eng.), Carnegie Fellow, Demonstrator of Anatomy, 
United College, University of St Andrews. Communicated 
by Dr W. G. Aitchison Robertson. (With a Plate.) 
(Read July 6, 1903.) 
CONTENTS. 
PAGE 
I. Description of the Research . . . .572 
II. List of Embryos examined . . . . .576 
III. Summary and Conclusions ..... 577 
IV. Literature . . . . . . .578 
V. Description of Illustrative Figures . . . 580 
I. Description op the Research. 
The pineal body or epiphysis has provided a favourite subject of 
study for many workers at research, and much discussion has 
arisen with regard to both its ontogeny and its phylogeny. Up 
to within recent years this structure proved a sort of enigma, and 
its true significance was not really understood until the researches 
of De Graaf (15) and Baldwin Spencer (27) during the eighties. 
Since then an extensive amount of work has been published on 
the subject, so that it almost appeared quite unnecessary for one 
to again enter upon this field of research. 
This paper was suggested to the author by an incidental observa- 
tion which was made over a year ago while examining some trans- 
verse sections of the thalamencephalon of a frog-tadpole’s brain. 
In this specimen it was noticed that the opening of communica- 
tion between the epiphysis and the thalamencephalon was not 
mesial m position, but was placed most distinctly to one side of 
the middle line. It therefore appeared advisable to make an 
1 The work which is embodied in this paper was undertaken by the author 
as a Research- Fellow of St Andrews University. 
