Cowing and Kenyon raise an important issue concerning Hox genes by suggesting that these genes may not only be expressed according to position but also according to cell lineage. This suggestion is based on two experiments in which the so-called M cell and two hypodermal V6 cells were manipulated to express a Hox gene,
mab-5, outside the posterior region of the Caenorhabditis elegans embryo. Here we propose a less radical interpretation of these data.