Figure 1. The relationship between the optic vesicle and brain ventricles in the developing Xenopus embryo are shown in these diagrams. The cross-sections, which are through the optic vesicles (dashed lines), compare stages 23, 26, and 27 in A, B, and C respectively. These drawings, were prepared based on [24,30], to illustrate that the brain ventricle and optic vesicle lumens are continuous at least at stage 23.