C-type virus particles in the transplantable mouse bladder tumour FCB grown in vitro.

Electron microscopic studies were made on an in vitro cultured cell line obtained from the FCB transplantable murine bladder tumour. The cells exhibited a loss of differentiation compared with solid tumour and the presence of C-type virus particles, many in the process of budding. The possible relation of this virus to murine bladder carcinogenesis is discussed.