. Amphioxus and the ancestry of the vertebrates. Amphioxus; Sea squirts; Hemichordata. INTERNAL ANATOMY. Th which has been observed in some craniate Vertebrates as described above, is therefore probably of the same nature as the ectodermic openings of the tubules in Fig- 35-—-"^- Schematic transverse section through pharyngeal region of Am- phioxus. On the left is a branchial bar, cut lengthwise, and on the right a gill-slit. B. Schematic transverse section through Selachian embryo. (After Bo\'KRI.) Atrial chamber, Pronephric duct, Nephrostome of pronephric t
. Amphioxus and the ancestry of the vertebrates. Amphioxus; Sea squirts; Hemichordata. INTERNAL ANATOMY. Th which has been observed in some craniate Vertebrates as described above, is therefore probably of the same nature as the ectodermic openings of the tubules in Fig- 35-—-"^- Schematic transverse section through pharyngeal region of Am- phioxus. On the left is a branchial bar, cut lengthwise, and on the right a gill-slit. B. Schematic transverse section through Selachian embryo. (After Bo\'KRI.) Atrial chamber, Pronephric duct, Nephrostome of pronephric tubule, Cross-section of excretory tubule in Amphioxus. Opening of excretory tubule into atrium in Amphioxus. Gonadic cavity (perigonadia! coelom) in A\ compared by Boveri with the mesonephric tubule, in B. gl. Glomerulus, ca:. Coelom. Endostylar ccelom. Branchial artery in A; sub-intestinal vein in B. Other letters as in previous figures. — In B the future opening of the mesonephric tubule into the pronephric duct is indicated by dotted lines on the right. The vessel connecting the sub- intestinal vein with the aorta is placed on the left of the alimentary canal for com- parison with Fig. A. It is really only present on the right side, although a rudiment occurs on the left. (See Note 6.) The glomeruli of the tubules in Amphioxus are supplied by blood-vessels which connect the dorsal aorta with the branchial artery. It should be remembered that the bran- chial artery represents the anterior portion of the sub-. 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 Willey, Arthur, 1867-. New York, London, Macmillan
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