Transactions of The Royal Society of Canada 



SECTION V 



Series III MAY, 1921 Vol. XV 



Significant Alterations in the Positions of Certain Neurohlast-Nuclei 

 of the Embryonic Retina: a Stîidy in Bio-Dynamics 



By John Cameron, M.D., D.Sc, F.R.S.E., F.R.S.C. 



(Read May Meeting, 1921) 



The histological material upon which the present research is 

 founded was prepared by the writer in 1902 while engaged in a study 

 of the histogenesis of the amphibian retina in the laboratory of the 

 late Professor Wm. His at Leipzig. During 1905 three papers(l) 

 were published, dealing with the results of these researches, in which 

 attention was directed mainly to a study of the myelospongium net- 

 work and the visual elements. During this investigation some 

 peculiar phenomena manifested by the neuroblast-nuclei, particularly 

 of the ganglionic layer, were detected. However, the interpretation 

 of these threatened to carry the research so far beyond the limitations 

 originally imposed upon it that it was decided to postpone the pub- 

 lication of the nuclear changes to a later date. Meanwhile, in 1916 

 Dr. R. J. Gladstone and the writer (2) pointed out that in the cell- 

 elements of the blastoderm, the nascent endoplasm immediately 

 investing the nuclei was a derivative of nuclear metabolism. Further, 

 in 1917 the writer (3) published in these Transactions a paper in 

 which it was afifirmed that in developing striated muscle the achro- 

 matic material which undergoes fibrillation was, partly at least, a 

 product of the metabolic activity of the nuclei of the myosyncytium. 

 With the publication of these later papers the writer feels that the 

 time is now ripe to make known the results of his observations on the 

 neuroblast-nuclei of the embryonic retina, more particularly as these 

 results are confirmatory of his earlier conclusions. 



The material for this research was chosen from Amphibia, as the 

 comparatively large size of the nuclei in this vertebrate class makes 

 them ideal for cytological study. Avian and mammalian types were 

 likewise studied, but owing to exigencies of space the results of the 

 examination of the amphibian forms will be alone referred to. 



^ An extensive amount of experimental research upon the adult 

 retina has been carried out, especially within recent years, and a 



