Locations of stripes of the pair rule genes ftz, eve and prd. The locations of stripe borders along the a/p axis were computed at 16 locations around each embryo; the measurements for all embryos were averaged. The results are displayed as orthographic projections in which the anterior of the embryo is to the left and the dorsal midline to the top. Pair-wise comparisons of the expression of (a) eve and ftz and (b) eve and prd are shown. The error bars give the 95% confidence intervals for the means. The relationship between eve and ftz stripes was constant, but prd stripes shifted their registration relative to eve's along both the a/p and d/v axes. The data for eve expression were derived from n = 215 embryos at stage 5:50-100%, ftz from n = 155, and prd from n = 17. Egg length (EL).