PLATE I 
EXPLANATION OF FIGURES 
1. Wax reconstruction of epithelium of cesophagus, showing vacuoles. a, 
human embryo of 19 mm., series 819. 6, embryo of 22.8 mm., series 871. X 89. 
2 Wax reconstruction of epithelium of cesophagus (region immediately below 
bifurcation of trachea). Human embryo of 37 mm., series 820. Showing single 
dorsal fold. 89. 
3. Same, human embryo of 42 mm., series 838. Showing dorsal and ventral 
folds and beginnings of lateral folds. X 89. 
4. Same, human embryo of 55 mm., embryo 249. Showing Greek cross stage. 
X 89. 
5. Same, human embryo of 120 mm., embryo 342. Showing four primary and 
four secondary folds. Maltese cross stage. > 89. 
