PLATE 2 



EXPLANATION OF FIGURES 



10 Horizontal section through the gill pouches of a grebe embryo of forty-six 

 hours, showing the position of the developing fifth and sixth aortic arches. 

 X 66. 



11 Medial view of a wax reconstruction of the third visceral pouch of a grebe 

 embryo of seven days. X ISSj. 



12 Medial view of a wax reconstruction of the fourth visceral pouch of the 

 same embryo. X 133g. 



13 Postero-ventral view of a wax reconstruction, showing the fifth and sixth 

 visceral pouches in their relations to the fourth pouch and the pharynx, in a 

 grebe embryo of five days. X 133^. 



ABBREVIATIONS 



Ao. 3,4,5,6, third, fourth, fifth, sixth Thy. Ill, IV, thymus of the third and 



aortic arches the fourth visceral pouch 



Par.///,/ F, parathyreoid of the third V.v.III,IV,V,VI, third, fourth, fifth, 



and the fourth visceral pouch sixth visceral pouches 



Drawings by G. H. Childs 



40 



