Cell motility, cell migration and phagocytosis are distinct, though frequently sequential, processes. They are fundamental for the maintenance of homoeostasis in single cells as well as in pluricellular organisms. Like vertebrates, invertebrate immune functions are strictly dependent on cell motility, chemotaxis and phagocytosis. Several comparative immunobiology experiments have tested the effects of mammalian factors on cell migration and phagocytic activity in invertebrate immune-competent cells. The discrepancies that were found suggest various hypotheses, e.g. species-specific reactions to heterologous factors. Here, we reconsider data concerning the effects of POMC (proopiomelanocortin)-derived peptides, cytokines and growth factors on molluscan immunocytes in the light of recent findings that also encompass the effects of experimental conditions.