Figure 7.

Stages 15 and 16: Anterior–posterior axis reads left to right in both images. Scale bar = 1 mm. Stage 15 (2 ¾ days). Stage 16 (3 days). Abbreviations: af, amniotic fold; at, atrium of heart; bc, bulbus cordis; cf, choroid fissure; di, diencephalon; ep, epiphysis; fgl, foregut lumen; flb, forelimb bud; hlb, hindlimb bud; lbf, lateral body of foregut; le, lens vesicle; mm, mesomere; ms, mesencephalon; mt, metencephalon; my, myelencephalon; opc, optic cup; ot, otic vesicle; pa, pharyngeal arch; rp, Rathke’s pouch; sc, spinal cord; sm, somite mesoderm; sto, stomodeum; tb, tailbud; te, telencephalon; tf, tail fold; tr, truncus arteriosus; vt, vitelline artery; vv, vitelline vein. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]