Printed in Great Britain STUDIES ON THE AUTONOMY OF

This autoradiographic study was designed to elucidate the relationship between the macro-nucleus and pellicular DNA in Paramecium. The capacity of the cell to synthesize pellicular DNA in the absence of the macronucleus was established by demonstrating the incorporation of tritiated thymidine into DNase-sensitive material in the pellicles of amacronucleate cells. Moreover, using a technique which leads to selective labelling of the macronucleus in normal paramecia, we have looked for evidence of transfer of labelled DNA from the macronucleus to the pellicle with time. Finding none, we conclude that labelled pellicular DNA is not of macro-nuclear origin, and that labelled pellicular DNA synthesis is not directly dependent on the presence of the macronucleus