Abstract
In this study, experiments are described in which part cr all of the occipital somites were removed from chick embryos of 8 to 25 somites. The embryos were reincubated and sacrificed 6 to 9 days after the operation. Adequate extirpations of somites 2 through 6 resulted in absence or depletion of one or more of the hypoglossal muscles, thus demonstrating their somtic origin from these levels. Somite 1 disappears early and does not make a contribution to the hypoglossal muscles. The optimal stages for operation are between 8 to 15 somites.