File:Aasar1931 text-fig01.jpg

B.H P. Buccal hypophysis primordium.

BR.F. Brain flexure.

BR.PL. Brain plate.

BR. W. Brain wall.

C.FL. Cephalic flexure.

CH. Notochord.

CH.PL. Chorda plate.

CL.M. Cloacal membrane.

E.H T. Endothelial heart tube.

END. Endoderm.

FG. Fore-gut.

F.FG. Floor of fore-gut.

F.PC.C. Floor of pericardial coelom.

H F.B. Head-fold bay. P.PL.M. Prochordal mesoderm.

I.Z. Cranial remains of head process.

M.B. Medial boundary of pericardio-peritoneal coelom.

M.S. Mesodermal somite.

O.PL.X. Angle where ectoderm runs into endoderm.

O.PL. Oral plate.

PAR. M. Paraxial mesoderm.

P.C0E. Pericephalic coelom.

P.EN D. Horseshoe-shaped or pericephalic zone of thickened endoderm.

P.PL. Prochordal plate.

P.K T. Primitive knot.

P.ST. Primitive streak.

P.ST. M. Primitive streak mesoderm.

PP.C’. Pericardio-peritoneal coelom.

P. M. Pre-axial mesoderm.

PC.C. Pericardialcoelom.

PR. G. Pre-oral part of fore-gut.

R.PC'.C'. Roof of pericardial coelom.

S. P. Seessel’s pouch.

T.OH. Free tip of notochord.

W .PG. Anterior wall of pre-oral part of foregut.