The amoebocytes and fibroblasts of intact connective tissues of the common pond snail foot, as well as the amoebocytes of the burn wound were studied by means of electron microscope. The found transitional forms from the amoebocytes to the fibroblasts allowed to conclude that there were cells--precursors of fibroblasts among the amoebocytes migrating in the wound. A tentative scheme of histogenetic series of amoebocytes is given.