326 



ANATOMY OF THE DOMESTIC FOWL 



FIG. 82. Embryological studies. 



A. i, The chorion and allantois. 2, The allantoic cavity. 3, The amnion. 



4, The yolk sac. 5, A small quantity of remaining albumin. 



B. Brain tube of a chick 25^ hours old showing partly closed brain tube with 

 eleven folds of neuromeres. 



C. The development of the alimentary tract, i, Trachea. 2, Lung. 3, 

 Esophagus. 4, Stomach. 5, Pancreas. 6, Bile duct. 7, V-shaped loop of mid- 

 gut. 8, Cloaca. 9, Vitello-intestinal duct. 



D. i to 6 inclusive, same as C. 7, Caeca. 8, Cloaca. 



E. Kidneys, Wolffian bodies, and testes of an embryo chick, i, The adrenals. 

 2, The genital. 3, Primitive oviduct. 4, Permanent kidney. 5, Ureters. 6, 

 Duct of primitive kidney which conducts the excretion into the cloaca. 



F. A transverse section of a chicks' head 48 hours of incubation, i, Fore- 

 brain. 2, Pigmented layer of retina. 3, Ectoderm. 4, Nervous part of retina. 



5, Optic stalk. 6, Invagination of ectoderm to form the lens rudiment. 



