Figure 21.

Stages 43 and 44: Anterior–posterior axis reads left to right in both images. Scale bar = 1 mm. Stage 43 (11 days). Stage 44 (12 days). Abbreviations: al, alula; cl, cloaca; el, eyelid; er, opening to ear; et, egg tooth; fl, forelimb; gp, gape flange; hal, hallux; hl, hindlimb; ica, internal carotid artery; le, lens vesicle; md, mandibular process; mx, maxillary process; na, nail; nar, nares; pft, pin feathers; tbt, tibiotarsus; tl, tail; tmt, tarsometatarsus. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]