. Elementary text-book of zoology, general part and special part: protozoa to insecta. Animals. Fig. 108.—^, Blastosphere of Amphioxus ; B, invagination of the saint; C, gasliula, invagi- nation completed; O, blastopore (after B. Hatschek). aperture of invagination (hlastoijore, mouth of gastrula) becomes the endodermal layer (hypoblast) lining the gastrula cavity. The outer layer of cells constitutes the ectoderm or ejnblast. This mode of formation of the gastrula, which is very common, is found, , in Ascidians, and amongst the Vertebrata in Amphioxus (fig. 108). More rarely the gastrula
. Elementary text-book of zoology, general part and special part: protozoa to insecta. Animals. Fig. 108.—^, Blastosphere of Amphioxus ; B, invagination of the saint; C, gasliula, invagi- nation completed; O, blastopore (after B. Hatschek). aperture of invagination (hlastoijore, mouth of gastrula) becomes the endodermal layer (hypoblast) lining the gastrula cavity. The outer layer of cells constitutes the ectoderm or ejnblast. This mode of formation of the gastrula, which is very common, is found, , in Ascidians, and amongst the Vertebrata in Amphioxus (fig. 108). More rarely the gastrula arises by delamination. This process consists of a concentric splitting of the cells of the blastosphere into an outer layer (epiblast), and an inner (hypoblast) (fig. 109).. Fig. 109.—Transverse sections through three stages in the segmentation of Geryonia (after H. Fol.) A, stage with thirty-two segments, each segment is divided into an external finely granular protoplasm (ectoplasm) and an inner clearer layer (endoplasm); B, later stage; C, embryo after delamination; with ectoderm slightly separated from the endoderm, which is composed of large cells surrounding the segmentation cavity. Tlie central cavity of the gastrula in this case is derived fiom the original segmentation ca^^ty, and the gastrula mouth is only secondarily formed by perforation. This method of development. 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 Claus, Carl, 1835-1899; Metcalf Collection (North Carolina State University). NCRS. London, Swan Sonnenschein
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanimals, bookyear1892
