Fig. 1. Timeline showing major morphogenetic events at 10°C in Boltenia villosa between late gastrulation, approx. 14 hours after fertilization (AF), when notochord cells begin to divide for the final time, and tailbud stage when notochord cells have completed their rearrangements to form a stack of coins. We analyzed at least 6 and typically more than 10 embryos at each time point. Labeled segments associated with a given event span the period in which we observed that event in one or more embryos. The actual intervals in which that event occurs may be shorter.