OBSERVATIONS ON CERCARIÆUM LINTONI MILLER AND NORTHUP AND ITS METACERCARIAL DEVELOPMENT

¹ From the Department of Zoölogy, University of Pittsburgh, the Marine Biological Laboratory, Woods Hole, Mass. and the Department of Biology, Kent State College

The description of Cercariæum lintoni Miller and Northup as given by earlier workers is supplemented and emended in the light of knowledge obtained by comparing the cercariæum with its metacercarial stage, developed in experimental animals. The true nature of the digestive and reproductive systems is made clear.

Cercariæum lintoni penetrated the parapodia of Nereis virens, encysted, and developed into the metacercarial stage. Although the cercaria would penetrate and encyst in other invertebrates, the clam worm was the only form in which development was secured. Nereis virens appears to be a natural host. The metacercaria develops adult features as the larval characters disappear.

It is difficult to determine the relationship of this species to other trematode groups; the digestive system is similar to that of the species of the family Haploporidæ, but the arrangement of the reproductive organs is very different and resembles that of the Zoogonidæ. palombi's suggestions concerning the relations of the species are discussed.