The purpose of this paper is to describe the development of the amebocytes in the testicular cavities and epididymal ducts ofDina lineata.The samples used in this study were healthy and sexually mature. Testicular amebocytes are found to enter the testicular cavities arising from the submesothelial connective tissue, and they proceed towards the spermatogonial morulae, to which they attach by means of tight junctions. When the amebocytes come out of the morulae, they increase in size and develop the cellular features of a macrophage. These cells remove residual cytophores and can eventually fuse to enclose entire morulae.