The developing primordial germ cells and spermatogonia are located in the peripheral region of the testis while the other stages are more central in position in Bilorchis mehrai species studied. Cytology of spermatogenesis in the digenea has attracted much attention of various investigators, but most accounts are restricted to the routine features of processes. The mitochondria and other cytoplasmic components of the male and the female germ cells have received less attention. However, recently, the utilization of the electron microscope and other advanced techniques have led the scientists to investigate the ultra-structure and biology of various components involving gametogenesis.The 2-celled, 4-celled, 8-celled, 16-celled and 32-celled clusters show clear rosette formation having conical cells with nice tapering towards the centre of the rosette. The author concludes that the nature of the rosette formation in the whole Digenea depends upon the duration of spermatogonial and spermatocyte stages.