e it 
Fig. 2 <A series of tracings made from the sections with the Edinger appa- 
ratus, X 200, and reduced to 663 diameters in reproduction. The solid color 
marks the otie plate and the acousticofacial ganglion and optic anlage; the 
rest of the nervous system, including the neural crest and the ectoderm, are 
stippled, the outer boundary of the pharynx is indicated by a heavy line and 
the myoepicardium marked by horizontal lines. The mesenchyme is not shown 
except where it was shrunken and then its outer limits are drawn. a. Mall 
embryo no. 391—eight somites—section 45. b. H87—eight somites—section 64 
(cf. figs. 3 and 4). c. Eternod ‘Du Ga’—nine somites—section 49. d.N.Y.U. 
embryo no. 4—fourteen somites—section 32. e. Pfannenstiel III—fourteen 
somites—section 41. f. Mall embryo no. 470—sixteen somites—sl. 2-1-7. 4a.1.p., 
anterior intestinal portal; ao., aorta; d.r.v., dorsal second aortic ramus; op.swl., 
optic sulcus; pe.c., pericardial cavity; ph., pharynx; VIII sul.; otic sulcus. In 
this and all other figures of sections the right side of the embryo appears at the 
observer’s left. 
206 
