ClipArt ETC
"A transverse section before the union of the amnion folds, and a longitudinal median section after the union of the fold. a., Anterior end of blastoderm; p.,. posterior end of blastoderm; a.f., in the left-hand figure, the beginning of the amnion fold; am., amnion; a.c., amniotic cavity; s., serosa; ec., ectoderm; ll., lower germinal layer; y., yolk. The amniotic cavity marks the future ventral region of the embryo, so that the yolk mass is dorsal." -Thomson, 1916

Insect Embryo

"A transverse section before the union of the amnion folds, and a longitudinal median section after…