IO SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



The material upon which the foregoing work was done was col- 

 lected by the author in central Florida with the aid of a grant from 

 the Smithsonian Institution. 



The embryos were removed from the eggs, in the field, and fixed 

 in various ways. They were sectioned chiefly in the transverse and 

 sagittal planes and were stained, in most cases, with borax carmine 

 and Lyon's blue. 



REFERENCES 



1. Hertwig, O. : Handbuch der vergleichenden und experimentallen Ent- 



wicklungslehre der Wirbelthiere. Bd. 2; Jena, 1906. 



2. Lillie, F. R. : The Development of the Chick. New York, 1908. 



3. Miller, W. S. : The Structure of the Lung. Journ. Morph., Vol. 8, p. 



171, 1893. 



4. Reese, A. M. : Development of the Digestive Canal of the American 



Alligator. Smithsonian Misc. Coll., Vol. 56, No. 11, pp. 1-25, 1910. 



5. Weber, A., and Buvignier, A. : Les premieres phases du developpement 



du poumon chez les embryon de poulet. Comptes rendu hebt. des 

 seances de la societe de Biologic Vol. 55, pp. 1057-1058. Paris, 1903. 



LETTERING 



a, aorta. w», mesoblastic lung primordium. 

 aa, anterior appendage. ml, mesoblastic layer. 



cm, auricle. n, notochord. 



b, V , bronchi. cc, oesophagus. 

 bv, blood vessel. p, pharynx. 



c, last gill cleft. pi, pleural coelom. 

 ca, cartilage rings of trachea and pv, pulmonary veins. 



bronchi. r, rib. 



ce, centrum. s, stomach. 



co, coelom. sp, spinal cord. 



e, epithelial vestige. t, trachea. 



ep, epithelium. tg, thyroid gland. 



g, laryngo-tracheal groove. to, tongue. 



gl, glottis. tr, trunchus arteriosus. 



h, heart. ty, thymus gland. 



/' — I, 3 lung or lung diverticula. u, umbilical cord. 



la, larynx. v, ventricle. 



It, liver. Wt, Wolffian tubules. 



DESCRIPTION OF FIGURES 



Fig. 1. — An outline of an alligator embryo at the beginning of the formation 



of the lungs. 

 Figs. 2 to 6. — Transverse section through an embryo of the stage shown in 



figure 1. The planes of these sections are shown in the reconstruction, 



figure 7. 



