. The biology of the frog. Frogs. THE DEVELOPMENT OF THE FROG 101 derm on either side are brought near each other in the mid- dorsal line. The free ventral edges of the masses or sheets of mesoderm extend ventrally until they meet below and come to surround the archenteron, except for a short space along the dorsal side. The sheets of mesoderm soon be- come split into an inner or splanchnic layer, which lies next. Fig. 31.—Sagittal section through a frog embryo. B, blastocoel; BP, dorsal lip of blastopore; BP', ventral lip of blastopore ; EE, epi- dermic layer of ectoderm; EN, inner or nervous
. The biology of the frog. Frogs. THE DEVELOPMENT OF THE FROG 101 derm on either side are brought near each other in the mid- dorsal line. The free ventral edges of the masses or sheets of mesoderm extend ventrally until they meet below and come to surround the archenteron, except for a short space along the dorsal side. The sheets of mesoderm soon be- come split into an inner or splanchnic layer, which lies next. Fig. 31.—Sagittal section through a frog embryo. B, blastocoel; BP, dorsal lip of blastopore; BP', ventral lip of blastopore ; EE, epi- dermic layer of ectoderm; EN, inner or nervous layer of ectoderm ; H, hypoblast or entoderm; T, mesenteron or gastrula cavity; Y, yolk plug. (After Marshall.) to the archenteron, and an outer, parietal, or somatic layer, which lies next to the ectoderm. The space between these two layers of mesoderm is the beginning of the ccelom, or body cavity. It is at first small, but as development pro- ceeds, it widens out more and more (Fig. 33, C). The cells just above the mid-dorsal wall of the archenteron form a thickening which soon becomes marked off sharply. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Holmes, Samuel J. (Samuel Jackson), 1868-. New York : The Macmillan company
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Keywords: ., bookauthorholmessamueljsamuelja, bookcentury1900, bookdecade1920
