With the purpose to pursue the property of phagocytes in ascites observations were carried on vital stainings of the ascites cells at the time of stimulation and after removal of the greater omentum as well as vital stainings of subcutaneous histiocytes and monocytes in the bone marro and blood; and also studied vital staining of the ascites cells stained after a certain period of culture. 1. At the time of stimulation the newborn cells in ascites are weak and immature, possessing characteristics very much like those of monocytes, and pre-existing phagocytes reveal an advanced degeneration. 2. In the case where dye was added in the course of culture, it has been confirmed that those cells transformed like fibrocytes, fibroblasts or histiocytes are none other than one of modified forms of phagocytes. 3. By excision of the greater omentum, it has been observed that phagocytes mature in the steps of a small type ➝ intermediate type ➝ large type. Moreover, it has been verified that phagocytes are derived from milky spots on the greater omentum. 4. After precise scrutiny of subcutaneous histiocytes and monocytes in the bone marrow and blood, the similarity of phagocytes to monocytes as already stated in Part 1 has been verified. From these data it is bilieved that ascites phagocytes are either monocytes or the cells very closely related to monocytes.