摘要: Abstract When single BHK21 cells exposed to polyoma virus were isolated in microdrops they gave rise normal, transformed, and mixed clones. Mixed clones constituted more than one-third of the total with transformed cells, when recloned pure cultures normal cells. propagated without recloning, rapidly replaced are probably due delayed transformation occurring up 7 or 8 generations after exposure cell virus. This late may be persistence intact some part it dividing