E PI BLAST 



PERI BLA ST 



ENTODERM OR PRiMARY 

 HYPOBLAST 



MESODERM 



EPIDER MAL 



ECTODERM 



NEURAL ECTODERM 



NOTO CHORD 



PRE-CHORDAL PLATE 

 DORSAL BLASTOPORAL LIP 



Fig. 181. Presumptive organ-forming areas of the blastoderm of the trout, Salmo 

 irideus. (A) Schematized section through blastoderm just previous to gastrulation. Pre- 

 sumptive entoderm (hypoblast) shown in black at caudal end of the blastoderm. Observe 

 that entoderm is not exposed to surface. Cf. (B). (B) Surface view of presumptive 

 organ-forming areas of the blastoderm just before gastrulation. 



^^cy^^ 



Fig. 182. Late blastoderms of Gymnophiona. (Modified from Brauer, 1897.) (A) 

 Late blastoderm of Hypogeophis alternans. Entoderm cells in black lie below. (B) Be- 

 ginning gastrula of H. rostratus. Observe blastocoelic spaces in white between the ento- 

 derm cells. 



369 



