. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 526 K. KAWAMURA AND M. NAKAUCHI cd ^ oa. 18 19 sto 20 22 23 FIGURE 3. Developing buds of stage 9. (Left) Serial sections from dorsal to ventral. (Right) Living animals viewed from dorsal side (A) and ventral side (B). aa, atrial aperture; ac, atrial chamber; ae, atrial epithelium; be, branchial chamber; bp, bud primordium; cd, ciliated duct; dg, dorsal ganglion; dt, digestive tract; e, epidermis; enp, endostylar placode; g, gonad; int. intestine; nc, neural complex; oa, oral aperture; p, pericardium; pep, posterior end of pe
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 526 K. KAWAMURA AND M. NAKAUCHI cd ^ oa. 18 19 sto 20 22 23 FIGURE 3. Developing buds of stage 9. (Left) Serial sections from dorsal to ventral. (Right) Living animals viewed from dorsal side (A) and ventral side (B). aa, atrial aperture; ac, atrial chamber; ae, atrial epithelium; be, branchial chamber; bp, bud primordium; cd, ciliated duct; dg, dorsal ganglion; dt, digestive tract; e, epidermis; enp, endostylar placode; g, gonad; int. intestine; nc, neural complex; oa, oral aperture; p, pericardium; pep, posterior end of peribranchial wall; sto, stomach. Bars = mm. of the inner vesicle, is the first organ rudiment to appear. Cells situated between the right and left PEP anlagen became also thickened. They were the presumptive do- main of the gut rudiment. Stage 6 At the beginning of stage 6, the pharyngeal (atrial) folds originating from the con- cavities of the inner vesicle grow posteriorly (Fig. IE), and the PEP anlagen become more discernible during this stage (Fig. 2C, VI). In living specimens, cells of the inner epithelial wall appeared squamous on each side of the body (Fig. 2VI). However, fixed whole mounts disclosed thickening of the right anterior region of the presump- tive atrial epithelium at this and subsequent stages (Fig. IE, F). The neural complex took on a rod-like shape (Fig. 2C1-5). Both its ends were open to the cavity of the inner vesicle. Stage 7 Stage 7 is recognized by the appearance of the gut rudiment (Figs. IF, 2VII) be- tween the two projections developing into the right and left ends of the posterior peribranchial wall. The pharyngeal folds continued to grow toward the posterior pro- •ctions (Figs. 2D:5-9, 2D:14-18, 4B). A small vesicle, the eventual pericardium, >ears in sections near the gut rudiment (Fig. 4B). In no case did we see the pericar- rudiment to be formed as an evagination of the inner vesicle. The dorsal ganglion ot yet established. S the peri
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
