PLATE 1 



EXPLANATION OF FIGURES 



1 Seventeen-day albino rat fetus, showing eye not yet covered by lids. 

 Orth's fixation; photographed in 80 per cent alcohol. X 3. 



2 Section across eye region of seventeen-day albino rat fetus, showing eye- 

 lids represented by ridges above and below. Wistar Institute collection, no. 

 15370. X 30. 



3 Eighteen-day albino rat fetus, showing eye covered by lids. Fixation in 

 10 per cent formaldehyde solution; photographed in same. X 3. 



4 Sections across eye region of eighteen-day albino rat fetus, showing lids 

 covering eye and fused together by their epithelial margins. Wistar Institute 

 Collection, no. 15371. X 30. 



5 Section across eye region of another eighteen-day albino rat fetus, showing 

 lids not yet in continuity, but their epithelial margins extending out as narrow 

 ridges and closely approximated. The upper lid is thicker and shorter, while 

 the lower is thinner and longer. X 30. 



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