Student Project Figures Figure 19 A schematic diagram showing the formation of a lesion at the site where two allogeneic (same species) colonies meet. The colonies are not compatible so the tunics are only partially fused. Hemocytes (blood cells), that originate from the ampullae, aggregate at the point of contact between the colonies (the movement of the hemocytes is depicted by the red arrows). The hemocytes disintegrate and their constituents react with the tunic matrix, forming electron-dense fibers. The fibers compound and form a rejection lesion between the colonies. Adapted and redrawn from Hirose, 2003.  Figure 18 Figure 19