Fig. 13. Dissociability of archenteron elongation and blastopore closure. (A) Plot of blastopore closure versus archenteron elongation for 97 normal embryos of various gastrula stages. (B,C) Embryos with highly similar archenterons and very different blastopores, indicated in A with pink points. (D,E) Embryos with highly different archenterons and very similar blastopores, indicated in A with purple points. The anterior limit of the archenteron is indicated with a red arrowhead. Nieuwkoop and Faber standard stages are presented for reference (Nieuwkoop and Faber, 1994), with the size of the circles approximately corresponding to the predicted variability.