Abstract
Chick embryo cells in tissue culture were infected with RPL-12 lymphomatosis virus, and H3-thymidine was put in the medium at various stages of cellular growth. Large intranuclear inclusions were induced, previously shown to have a strong positive Feulgen reaction. Histo-autoradiographs of these cultures indicated that thymidine was incorporated into the nuclear inclusions induced by the virus. The incorporation was independent of cell division, and continued for at least 56 hours after infection. Chromosomal deoxyribonucleic acid (DNA) played no major role in the formation of inclusions. Apparently DNA synthesis is an essential part of the reproduction of this virus.