Fig. 2. Comparison of allantoic lengths in 20-and 6-hour regenerates and unoperated controls. Bar graphs of the length (in µm) of (A) unfused and fused allantoic regenerates, and control unoperated allantoises after 20 hours in culture, and (B) allantoic regenerates and control unoperated allantoises after 6 hours in culture, measured in the dissection microscope. Allantoic lengths were plotted against the developmental stage at which the culture period began. In B, the single regenerate created at 6-somite pairs was so small that it could not be accurately measured in the dissection microscope; thus, no bar is seen at this time point. The total number of allantoises scored in each category is indicated at the base of each column of the graph; vertical lines at the apex indicate the s.e.m.s; and asterisks in A indicate significant differences in length between unfused allantoic regenerates and unoperated control allantoises for each time point (P<0.05). Abbreviations: EB, neural plate/early allantoic bud stage; LB, neural plate/late allantoic bud stage; EHF, early headfold stage; LHF, late headfold stage; 1-6-s, 1- to 6-somite pairs.