THE factor of crude oil waste has naturally been considered in connexion with the remarkable disappearance of Zostera marina, and a comparative analysis of samples of mud is being undertaken. There are three reasons, however, which render it difficult to believe that excessive oil-pollution is the cause of the phenomenon: (1) the suddenness of the disappearance of the plant over such a very wide area ; (2) its general disappearance over this wide area irrespective of the degree of oil-pollution ; and (3) the continued existence of Zostera beds for many years in areas believed to be heavily polluted. An instance is quoted by Dr. H. F. Lewis, moreover, of Zostera marina remaining unharmed in an area in the St. Lawrence where an oil tanker had been wrecked and heavy crude oil pollution occurred. It is of interest to note that in Europe, as in the United States, Zostera nana is still abundant and apparently quite healthy.