160 Proceedings of Roy al Society of Edinburgh. 
On the Origin of the Epiphysis Cerebri as a Bilateral 
Structure in the Chick. By John Cameron, M.B. 
(Edin.), M.R.C.S. (Eng.), Carnegie Fellow, Demonstrator of 
Anatomy, United College, University of St Andrews. Com- 
municated by Dr W. G. Aitchison Robertson. 
(MS. received January 4, 1904. Read same date.) 
CONTENTS. 
PAGE 
(1) Results of the present Research .... 160 
(2) Comparison of Results ..... 163 
(3) Summary and Conclusions . . . . .164 
(4) Literature . . . . . . .165 
(5) Explanation of Illustrations . . . .167 
(1) Results of the present Research. 
Till within recent years the epiphysis cerebri has been generally 
regarded as a mesial outgrowth from the roof of the thalamenceph- 
alon in Vertebrates. The researches of B6raneck (5), Dendy (11), 
Hill (17), and Locy (19), however, tend to demonstrate the fact that 
this structure arises in the form of two bilateral outgrowths ; while 
Gaskell (12) has drawn attention to its bilateral nature in 
Ammocoetes. Some observations which the author made on the 
development of the epiphysis in Amphibia (8 and 9) were found to 
agree in the main with those of the above-mentioned workers. The 
present research was therefore undertaken with the view of cor- 
roborating the results which had been obtained in the Amphibia, and 
it was found that these received support in the case of the chick. 
A number of early chick-embryos (chiefly between the 50th 
and 60th hours of incubation) were examined ; and although it was 
difficult in every instance to obtain distinct evidence of the bilateral 
nature of the epiphysis, still in the majority of cases this con- 
dition was distinctly marked. The reason for the difficulty of 
demonstrating in all cases the presence of the bilateral epiphysial 
condition will be explained later. 
