. Comparative embryology of the vertebrates; with 2057 drawings and photos. grouped as 380 illus. Vertebrates -- Embryology; Comparative embryology. Fig. 237. Chick embryo of 17 to 19 pairs of somites. (Approximating Hamburger and Hamilton, '51, stage 13, 48 to 52 hours of incubation, sections indicated on outline drawing.) Head lies partly on left side; auditory pits are deep; cervical flexure is evident in region of rhombencephalon; cephalic flexure is marked; stomodaeum is a deep inden- tation touching foregut between the first pair of aortal arches; head fold of amnion reaches back to ante
. Comparative embryology of the vertebrates; with 2057 drawings and photos. grouped as 380 illus. Vertebrates -- Embryology; Comparative embryology. Fig. 237. Chick embryo of 17 to 19 pairs of somites. (Approximating Hamburger and Hamilton, '51, stage 13, 48 to 52 hours of incubation, sections indicated on outline drawing.) Head lies partly on left side; auditory pits are deep; cervical flexure is evident in region of rhombencephalon; cephalic flexure is marked; stomodaeum is a deep inden- tation touching foregut between the first pair of aortal arches; head fold of amnion reaches back to anterior part of rhombencephalon (hindbrain). (A) Anterior (telen- cephalic) portion of prosencephalon, showing closed neuropore; amnion is indicated. (B) Optic vesicles. (C) Anterior end of foregut, showing anterior extremity of sto- modaeal invagination and first (mandibular) pair of aortal arches; notochord ends and pre-chordal plate area begins at about this section. (D) Anterior end of heart (ventral aorta); observe thin roof plate of neural tube, characteristic of the later myelencephalic (medulla) portion of rhombencephalon or hindbrain. (E) Otic (auditory) pits and anterior region of ventricular portion of heart. (F) Caudal limits of forming heart, dorsal mesocardium, neural crest cells. (G) Caudal end of heart, showing converging (vitelline) veins of the heart, sclerotome given off to notochordal area, lateral meso- cardium forming. (H) Anterior trunk area, showing diff'erentiation of somite and typically flattened condition of ectoderm, mesoderm, and entoderm. (I) Caudal trunk area, showing undifferentiated somite (epimeric mesoderm), intermediate mesoderm (mesomere), and lateral plate mesoderm (hypomere). (J) Similar to (I). (K) Caudal trunk region, showing closing neural tube. (L) Area of Hensen's node. (M) Primi- tive streak. 487. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and
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