Some effects of centrifugal force upon the egg of the grasshopper, Melanoplus differentialis, have been reported by Bodine and Boell (1936). It was thought advisable to extend these observations to the embryo of this species since with data on both the egg and contained embryo, conclusions might be derived as to which parts in the egg (embryo or extra-embryonic materials) were being most affected. The present paper, therefore, is based upon a study of the O2 consumption of eggs and embryos subjected to various centrifugal forces as developed by the air-driven ultracentrifuge of Beams (1930)