so 



ATLAS OF BIOLOGY. 



/./. Yolk-hearing lower-layer cells. 



>il. Mandihular arch. 



m.f. Medullary fold. 



.//. Medullary groove. 



ii'. />. Muscle plate. 



ma. Undifferentiated mesoblast. 



na. Nasal involution (anterior nostril). 



it.ii. Neural (cerebro-spinal) axis. 



lie. Nucleus. 



n.f. Neural canal. 



n.e. Nenrenteric canal. 



ce. (Esophagus. 



op. Optic cup (retina). 



op'. Optic stalk (optic nerve). 



prt. Proctodreura. 



//'/'. Aperture of involution of the same (cloacnl 



aperture). 



}il. Pulmonary sue (lung). 



/iji. Oral papillfe. 



iv. Prorenal Isegmental) duct. 



t. Head suckers. 



K'l. Stomodfenm. 



ml'. Aperture of involution of the same (oral 



aperture). 



KIII. Somatic mesohlast. 



*/'. Splanchnic mesoblast. 



tij. Tympano Eustachian cleft. 



tii' . Membrana tympani. 



r.r. Posterior cardinal vein. 



V 



