Fig. 3. src64 is not required for membrane invagination during cellularization. For both wild-type and src64 embryos, the progress of membrane invagination was measured from the cell apices to the cellularization front and plotted at five minute intervals starting at the beginning of cycle 14 (time=0 minutes) at 25°C. Maximum cellularization depth is obtained just before gastrulation begins in the interval between 55 minutes and 60 minutes. During early cellularization, the s.e.m. values are between 0.1 µm and 0.6 µm, whereas during late cellularization, the s.e.m. values are between 0.5 µm and 1.0 µm.