ANATOMY OF THE DOMESTIC FOWL 



FIG. 83. 



A. Longitudinal section of chick, 4 days incubation, i, Cephalic fold. 2, 

 Caudal fold. 3, True amniotic cavity. 4, Epiblast. 5, Somatic mesoblast. 6, 

 Visceral mesoblast. 7, Hypoblast. 8, Future anua still closed. 9, The allan- 

 toic vessicle. 10, The mesentery, n. Intestine. 12 and 13, Yolk sac. 14, 

 Cavity of true amnion. 15, The mouth. 16, Pleuro-peritoneal cavity. 17, 

 Fore gut. 



B. Membranes of the chick at the third day of incubation, i. Membrane 

 surrounding albumin. 2, Amnion. 3, Allantois. 4, Vitellicle. 



C. The fore part of an embryo chick at the second day. i, Mesencephalon. 

 2, The eye. 3, Olfactory organ. 4, Mandibular arch. 5, Maxillary arch. 

 6, Maxillary arch. 7, Hyoidean arch. 8, Scapular arch. 9, Depression organ 

 of hearing, n, Process from encephalon for union with nerve of hearing. 



D. Primitive blood-vessels at second day of incubation (Owen), i, Meso- 

 cephalon. 2, The right anterior longitudinal vein. 3, The eye. 4, The man- 



