Smith and Stoker1 have noted that the deoxyribonucleic acid of Q-fever rickettsiae (R. burneti) grown in embryonated eggs is closely similar in composition to that of chick embryos, the only significant difference being lack of 5-methyl cytosine from the former. To account for this similarity, they mention the possibility that rickettsiae may incorporate nucleic acid directly from their host. This hypothesis could be tested, they point out, by analysis of the same organism grown in a different host.