. Outlines of zoology. Zoology. Fig. 182.—Early stages in the development of Ampkioxus. —After Hatschek. 1. Ovum with germinal vesicle ; 2. four-cell stage; 3. external appearance of blastula ; 4. blastula in section ; 5. beginning of gastrula stage ; 6. section of completed gastrula. forms the medullary tube, which opens into the gut by the neurenteric canal, and to the exterior by the anterior neuro- pore (Fig. 183). The cavity of the gastrula—the archenteron—becomes the gut of the adult, and gives rise to the coelomic pouches (seep. 417). The notochord arises along the mid-dorsal line of th
. Outlines of zoology. Zoology. Fig. 182.—Early stages in the development of Ampkioxus. —After Hatschek. 1. Ovum with germinal vesicle ; 2. four-cell stage; 3. external appearance of blastula ; 4. blastula in section ; 5. beginning of gastrula stage ; 6. section of completed gastrula. forms the medullary tube, which opens into the gut by the neurenteric canal, and to the exterior by the anterior neuro- pore (Fig. 183). The cavity of the gastrula—the archenteron—becomes the gut of the adult, and gives rise to the coelomic pouches (seep. 417). The notochord arises along the mid-dorsal line of the archenteron; its forward extension is secondary. During the early part of larval life the ectoderm cells, including those forming the medullary canal, are 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 Thomson, J. Arthur (John Arthur), 1861-1933. Edinburgh, Glasgow and London, H. Frowde and Hodder & Stoughton
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Keywords: ., bookauthorth, bookcentury1800, bookdecade1890, booksubjectzoology
