(A-C) Pax6; (D,E) Pax3/7; (F-K) Pax2/5/8. Stages are indicated by St#. Note the artefact in vitreous humour in the eye (asterisk). E, F and J are similar cutting planes, E, being the most anterior. Scale: 150 μm. The retina (arrow) is devoid of Pax6 (A,B), Pax3/7 (D) and Pax2/5/8 (G, H) expression although surrounding tissues express Pax6 and/or Pax3/7. At stage 24, the brachial cord (circle) expresses Pax6 (C) and Pax2/5/8 (I). The arm epidermis also expresses Pax6 but not Pax2/5/8 (double-arrow). The anterior suboesophageal mass expresses Pax3/7 (ASM in E) and Pax2/5/8 (ASM in F). The middle suboesophageal mass expresses Pax2/5/8 (MSM in F). The optic tractus (J) and the stellate ganglia (sg in K) express Pax2/5/8, as the dermal part of the skin (arrowhead). iy: internal yolk sac. ol: optic lobe. SPM: supraoesophageal mass.