The communication is an abstract of our observations on the Bionomics of Convoluta Roscoffensis , the green Turbellarian peculiar to the coast of Brittany. A detailed illustrated account of these observations will be published shortly. The work was begun at Roscoff in 1901, and has been carried on since at Trégastel (Côtes du Nord), and in the laboratories of Owens College, Manchester, and University College, Reading. It contains the following sections:— 1. Food; 2, Development of the Green Cells; 3, Tropisms; 4, Ecology.