. A manual of elementary zoology . Zoology. 480 MANUAL OF ELEMENTARY ZOOLOGY form a tube which will become the nerve cord. Its hollow is the neural canal, and the blastopore, which is now known as the neurenteric canal, leads from it to the gut. Eventually the neurenteric canal closes. An opening, known as the neuropore, long remains at the front end of the neural canal and puts it into communication with the olfactory pit 7 ect. Fig. 359.—Stages in the gastrulation of Amphioxus. Modified.— After Hatschek. In 7 a half blastula is shown ; 8-11 are sections. ach., Archenteron; Up., blastopore; d
. A manual of elementary zoology . Zoology. 480 MANUAL OF ELEMENTARY ZOOLOGY form a tube which will become the nerve cord. Its hollow is the neural canal, and the blastopore, which is now known as the neurenteric canal, leads from it to the gut. Eventually the neurenteric canal closes. An opening, known as the neuropore, long remains at the front end of the neural canal and puts it into communication with the olfactory pit 7 ect. Fig. 359.—Stages in the gastrulation of Amphioxus. Modified.— After Hatschek. In 7 a half blastula is shown ; 8-11 are sections. ach., Archenteron; Up., blastopore; d,, future dorsal side; eel., ectoderm; end., endoderm ; «./., neural plate. The position-is not the same as in Fig. 358, the large cells being to the right instead of below. (p. 338). Meanwhile the hypoblast under the neural plate has also been undergoing a folding, by which it gives rise to the notochord and to the mesoderm, which at this stage is known as mesoblast. The notochord is formed by a median longitudinal groove (Fig. 364, 15) which becomes constricted off from the gut from before backwards, its cells eventually rearranging themselves to form a rod (Fig. 362) and becoming. 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 Borradaile, L. A. (Lancelot Alexander), 1872-1945. London : H. Frowde, Hodder & Stoughton
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectzoology, bookyear1920
