In the experiments with P32, we selected for structures with the properties of the protein membrane of the phage, and then looked for phosphorus associated with them. Different results might have been obtained if the protein itself had been labeled. Such experiments have now been carried out, again using the phage T4, but labeling with S35. The results indicate that noninfective, sedimentable particles which adsorb and precipitate with the specificity of the T4 phages are present in both premature and ordinary lysates. From the negative results obtained with P32 we conclude that these particles are phosphorus-free
