[Occurrence of circulating immunocytes in the process of graft rejection in nemertines of the genus Lineus (acelomate invertebrates)].

Performed upon bispecific Lineus chimaeras of a suitable constitution, the grafting of tissues excised from nemerteans of a third Lineus species resulted in a confrontation between graft cells, fixed cells from one chimaera component and mobile cells which originate from the second chimaera component. Survival of such grafts was dependent only upon compatibility in the "graft cells/mobile cells of recipient" interspecific combination. This result shows evidence for the existence of circulating immunocompetent cells which are responsible for the specific immune response to tissue transplantation in nemerteans of the genus Lineus.