Figure 3. Proposed model of relationship between rate of vacuole inflation and rate of cellular rearrangement. (A) Cartoons of cross section and dorsal views of a hypothetical notochord consisting of a single row of vacuolated inner cells. (B) Cartoons of cross section and dorsal views of a zebrafish notochord consisting of two rows of inner vacuolated cells. (C) Cartoons of cross section and dorsal views of a hypothetical notochord consisting of three rows of vacuolated inner cells. (D) Cartoon depicting the organization of the notochord before vacuole inflation as a single stack of intercalated sheath and vacuolated cells. During development the sheath cells leave the midline to surround the vacuolated cells at a rate of k_r while the vacuoles inflate simultaneously at a rate of k_i. (E) Graph of the relationship between the rate of cell rearrangement (k_r) and rate of vacuole inflation (k_i). We hypothesize a balance between the two rates is seen with an organization of two rows of vacuolated cells.