Abstract
Till within recent years the epiphysis cerebri has been generally regarded as a mesial outgrowth from the roof of the thalamencephalon in Vertebrates. The researches of Béraneck (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 Ammocœtes. 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 corroborating the results which had been obtained in the Amphibia, and it was found that these received support in the case of the chick.