246 



THE DEVELOPMENT OF THE CHICK 



QfiJ. 



2>.P. 



Ao.m.i 



FIG. 148. Median sagittal section of an embryo of eight days. 



a. A., Aortic arch. All., Allantois. An., Anus. A. o. m., Om- 

 phalomesenteric artery. B. F., Bursa Fabricii. b. P., Basilar plate. 

 C. A., Anterior commissure, c. C., Central canal. Ch. op., Optic 

 chiasma. C. p., posterior Commissure. Cl., Cloaca. Cr., Crop, 

 d Ao., Dorsal aorta. D. Hyp., Duct of the hypophysis. Ep., Epi- 

 physis. Fis. Bus., Fissura Eustachii. Hem., Surface of hemisphere 

 barely touched by section. Hyp., Hypophysis. L. t., Lamina ter- 

 mmahs. n. A. 8, neural arch of the eighth vertebra. Nas., Nasal 



