Plate XIX 



Fig. 20. Schematic outline of reconstruction of 20 millimeter embryo. Columbia 

 Collection, No. 325, to show levels of foregoing sections. 



Fig. 21. Reconstruction of the alveolingual region of a human embryo of 22 

 millimeters. Columbia Collection, No. 3, X 150, reduced 5. Left side, 

 ventral view. 



