. Comparative embryology of the vertebrates; with 2057 drawings and photos. grouped as 380 illus. Vertebrates -- Embryology; Comparative embryology. FORMATION OF PROTECTIVE EMBRYONIC MEMBRANES 911 However, in the pig and many other mammals, the allantoic diverticulum is a large, spacious structure (see figure 370D and E). Respiratory devices thus arise as diverticula from two general areas of the vertebrate body, viz.: (1) the pharyngeal area (see Chapter 14) and (2) the hindgut area. e. Yolk Stalk, Allantoic Stalk, Belly Stalk, and Umbilical Cord As the embryo increases in size (see figures 3
. Comparative embryology of the vertebrates; with 2057 drawings and photos. grouped as 380 illus. Vertebrates -- Embryology; Comparative embryology. FORMATION OF PROTECTIVE EMBRYONIC MEMBRANES 911 However, in the pig and many other mammals, the allantoic diverticulum is a large, spacious structure (see figure 370D and E). Respiratory devices thus arise as diverticula from two general areas of the vertebrate body, viz.: (1) the pharyngeal area (see Chapter 14) and (2) the hindgut area. e. Yolk Stalk, Allantoic Stalk, Belly Stalk, and Umbilical Cord As the embryo increases in size (see figures 370C-E; 372B-D), the yolk- sac connection with the mid-gut area of the embryo becomes relatively smaller. The constricted area of entoderm and mesoderm which connects the yolk sac with the midgut is called the vitelline duct or yolk stalk. Similarly, the constricted area of the allantois which connects the allantoic diverticulum with the hindgut area is called the allantoic stalk. As the embryo continues to enlarge, the yolk stalk and allantoic stalk are brought closer together and their mesoderms fuse. The closely associated yolk and allantoic stalks form the belly stalk in the area where they attach to the belly (ventral) wall of the embryo (fig. 370E). The narrowing ring-like area between the ventral body. Fig. 371. Brood compartments for care of young. (A) Pregnant female of the lizard, Chalcides tridactylus (Seps chalcides), showing uterine compartments containing develop- ing eggs. (Redrawn from Needham, 1942, Biochemistry and Morphogenesis, Cambridge University Press, London.) (B) Dorsal brood pouch in the anuran, Gastrotheca pygmaea. (C) Dorsal brood pouch in Gastrotheca marsupiata. Observe small dorsal opening of pouch. (D) Dissection of vocal (brood) pouch in male of Rhinoderma darwinii. (B-D, redrawn from Noble, 1931, The Biology of the Amphibia, McGraw- Hill, N. Y.). Please note that these images are extracted from scanned page images that may have been digitally enh
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