Embryos lie motionless in the vitelline membrane and fail to hatch. Examination with polarised light reveals a lack of differentiated muscle. Myoblasts fail to fuse. At 13 to 14 hours of development the myoblasts lie in a segmental array. At 16 to 17 hours of development the myoblasts fall into two populations, stretched and rounded. Stretched myoblasts first appear at around 11 hours after egg laying, and eventually can span distances two or three times the length of normal muscles. They often occur at positions and in orientations reminiscent of wild type muscle precursors. Only very few fusions occur. Segregation and movement of slou-expressing founder cells and vg-expressing cells is normal.