Fig. 5. Scanning electron micrographs of E15 (A-H) and E16 (K, L) eyelids from Fgf10^+/– (A,C,E,G,K) and Fgf10^–/– (B,D,F,H,L) fetuses. C,E,G and D,F,H are higher magnifications of A and B, respectively. (C,D) The inner canthus region, (E,F) the lower eyelid margin, and (G,H) the outer canthus region. Clumps of rounded periderm cells are observed in the inner canthus of the Fgf10^–/– mutant (D), but rarely seen in the outer canthus (H). (E) The arrowheads indicate a regular accumulation of epithelial cells, with the future periderm cells lined up on the eyelid margin of the heterozygote. (F) In the homozygote, rounded periderm cells are scattered away from the eyelid margin. (I,J) Transmission electron micrographs of the eyelid tip epithelium from wild-type (I) and Fgf10^–/– (J) E15 fetuses. Section near the outer canthus region. Insets show higher magnifications of filopodia of a leading edge cell (indicated by an arrowhead). (I) Numerous filopodia are produced. (J) In the Fgf10^–/– mutant leading edge, epidermal cells still produce filopodia, although these are distinctly fewer and shorter. co, cornea. (K,L) Fgf10^+/–eyelids are fused, whereas Fgf10-null ones are wide open. Scale bars: 380 µm (A,B); 60 µm (C-H); 5 µm (I,J); 300 µm (K); 500 µm (L).