J. 65 Hours (33 somites) K. 76 Hours (38 somites) 
pie roth 
<P 
Cuards o 
1 MOVE) aie ta 0 
Heh saa a \ 
- 
ALV. -7 \ 
V 0.M.M> 7 
Z. 100 Hours (45 somites) 
structures in the embryo. These figures are arranged and lettered to correspond 
with the detailed drawings of the hearts shown in the plates. J to VJ, aortic 
arches I to VI, respectively; A.C.V., anterior cardinal vein; A.J.P., anterior in- 
testinal portal; Al.V., allantoic vein; Ao., aorta; At., atrium (d., right), (s., left); 
Au.P., auditory pit; Aw.V., auditory vesicle; Bul., bulbus cordis; Cuv. d., duct of 
Cuvier; Endc., endocardium; F.G., foregut; Hep.s., stubs of some of the larger 
hepatic sinusoids; 7.C.A., internal carotid artery; L.B.W., lateral body wall; 
Myc., myoepicardium; Myc*., cut edge of myoepicardium; P.C.V., posterior car- 
dinal vein; Sin.-at., sino-artrial region of heart before its definite division; S.V., 
sinus venosus; Vent., ventricle; V.ao.r., ventral aortic roots; V.C., visceral cleft; 
V.C.M., omphalomesenteric veins; V.C.M.M., fused omphalomesenteric veins; 
V.V., vitelline veins. 
379 
