The distribution pattern of some hydrolytic and oxidizing enzymes amongBotryllus schlosserihemocytes has been investigated histochemically. Signet‐ring cells, macrophages, and some hyaline amoebocytes were found to stain positively for phosphatases, glycosidases, and esterases, and morula cells and some granular amoebocytes for arylsulfatase, peroxidase, and phenoloxidase. Our results suggest two differentiation pathways for these blood cell types: one involves hyaline amoebocytes, signet‐ring cells, and macrophages and leads to phagocytic cells; the other involves granular amoebocytes and morula cells and leads to cells responsible for inflammatory responses.