IN a previous note in NATURE1 we pointed out the association of a Labyrinthula-like organism with the wasting disease of the eelgrass along the American Atlantic coast. Since the publication of this announcement, we have performed a number of experiments in the laboratory and in the natural beds themselves, which indicate that this organism is a true parasite of Zostera marina. Communications from other investigators and examinations of specimens submitted from various points show also that this parasite is uniformly present in the infected beds on the Atlantic coasts of both Europe and America.