THE SEASONAL INFESTATION OF NASSA OBSOLETA (SAY) WITH LARVAL TREMATODES

¹ WASHINGTON UNIVERSITY, SAINT LOUIS

From the data resulting from the examination of almost nine thousand specimens of Nassa obsoleta Say it seems clear that there is a semi-annual rise and fall in the larval trematode infestation. In view of the fact that none of the adults of these larvæ are known it is difficult to explain these phenomena. In all probability migrations of the definitive hosts, and the degree of their infestation, affect the seasonal fluctuations; and other factors are probably the life span of Nassa, and the effect of parasitism upon it. The relative importance of these factors is not clear.