PLATE 5 



EXPLANATION OF FIGURES 



12 Coronal section of the trachea in the region of its bifurcation, X 176. 

 176 hour chick embryo. 



13 Coronal section of the trachea in the region of its bifurcation, X 100. 

 200 hour chick embryo. 



14 Coronal section of the trachea in the region of its bifurcation, X 104. 

 248 hour chick embryo. 



210 



