Observations on some tumours found in two species of planaria—Dugesia etrusca and D. ilvana

Since the description by Pallas in 1774 of their remarkable capacity for regeneration the planarians have been of interest to the biologist (cf. Brøndsted's excellent review—Brøndsted, 1955). Dubois (1949) has shown that regeneration in planaria is due to undifferentiated totipotential cells referred to as neoblasts, which are the only cells known to divide mitotically. When the animal is cut or similarly injured, some neoblasts in the region of the wound rapidly differentiate to form a new epidermis, while other neoblasts divide and migrate towards the wound surface where they continue to divide and/or differentiate into various cell types. The finding of spontaneous growths or tumours in this simple material (Goldsmith, 1939) suggests that it may be of interest to study the nature of such tumours. Material for the present studies includes the species Dugesia etrusca and D. ilvana obtained from the laboratory of Professor Mario Benazzi of the University of Pisa, Italy.