. Comparative embryology of the vertebrates; with 2057 drawings and photos. grouped as 380 illus. Vertebrates -- Embryology; Comparative embryology. ENTODERMAL TUBULATION DORSAL ARCHING MOVEMENT DERMATOME MYOTOME SCLEROTOME _ NEPHROTOME MESODERMAL TUBULATION DORSAL EVAGINATION OF ENTODERM ATERAL FOLDS OF AMNION EMBRYONIC COELOM EXTRA-EMBRYONIC COELOM. FUSION OF BODY LAYERS DISAPPEARANCE OF VENTRAL MESENTERY OR VENTRAL FUSION OF MESODERMAL LAYERS BELOW GUT TUBE Fig. 241. Formation of ventral body wail, differentiation of somites, formation of dorsal and ventral mesenteries, embryonic and extra-
. Comparative embryology of the vertebrates; with 2057 drawings and photos. grouped as 380 illus. Vertebrates -- Embryology; Comparative embryology. ENTODERMAL TUBULATION DORSAL ARCHING MOVEMENT DERMATOME MYOTOME SCLEROTOME _ NEPHROTOME MESODERMAL TUBULATION DORSAL EVAGINATION OF ENTODERM ATERAL FOLDS OF AMNION EMBRYONIC COELOM EXTRA-EMBRYONIC COELOM. FUSION OF BODY LAYERS DISAPPEARANCE OF VENTRAL MESENTERY OR VENTRAL FUSION OF MESODERMAL LAYERS BELOW GUT TUBE Fig. 241. Formation of ventral body wail, differentiation of somites, formation of dorsal and ventral mesenteries, embryonic and extra-embryonic coelom, etc., in chick embryo. (A) Dorsal upgrowth is evident as neural tube, somites, and forming ento- dermal (gut) tube are projected upward above the level of the extra-embryonic tissues. Observe heavy line at left, denoting general region of demarcation between embryonic and extra-embryonic tissues. (B) Separation of differentiating somite from nephro- tome; sclerotomic mesenchyme is migrating from somite to notochordal-neural area; lateral body folds are migrating mediad to form ventral wall of trunk region; lateral folds of amnion are migrating dorsad. (C-E) Dorsal upgrowth movement lifts em- bryonic body above extra-embryonic tissues below; fusion of ventral, body-wall layers begins. (C) Body layers are meeting in midventral line. (D, E) Fusion of ventral body-wall layers, disappearance of ventral mesentery. epimeric mesoderm on either side of the notochord gradually moves laterally and dorsally and comes to lie along the lateral aspects of the notochord and neural tube. During this migration, each epimere increases in thickness and becomes segmented into small oblong blocks of cells called somites (figs. 23IN; 233B; 234D; 245A). A somite which forms in the epimere on one side of the notochord always has a corresponding somite in the epimere on the other side of the notochord. Somites thus form in pairs, each pair representing a primitive segment of the develo
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