1. On the Nature and Functions of the “Yellow Cells” of Radiolarians and Cœlenterates

Abstract

It is now nearly forty years since the presence of chlorophyll in certain species of Planarians was recognised by Schultze. Later observers recognised that the green colour of certain Infusorians, of the common fresh-water hydra (Hydra viridis), and of the freshwater sponge (Spongilla fluviatilis), was due to the same pigment, but little more attention was paid to the subject until Ray Lankester applied the spectroscope to its investigation.