Differences between the eggmasses of Alderia modesta and Limapontia depressa

The eggmasses of the sacoglossan slugs Alderia modesta (LovéN) and Limapontia depressa A. & H. have often been described, but the differences between them have never been pointed out. ENGEL, GEERTS & VAN REGTEREN ALTENA (1940) even have written, that it was impossible to distinguish the spawnmasses of Alderia modesta from those of Limapontia depressa. During a stay at the Zoological Station at Den Helder in summer 1953, however, it appeared to me that there are clear differences between the eggmasses of the two species.