. The elements of embryology . Embryology. III.] THE HYPOBLAST. 51 result in the formation of the three layers of the blasto- derm. The upper layer, which is the epiblast already spoken of (Fig. ), takes at first but little share in these changes. In the lower layer, however, certain of the cells begin to get flattened horizontally, their granules become less numerous, and the nucleus becomes distinct; the cells so altered cohere together and form a membrane. The membrane thus formed, which is first completed in FiQ. Transverse Section through the Blastoderm of a Chick BEFORE THE APPEA
. The elements of embryology . Embryology. III.] THE HYPOBLAST. 51 result in the formation of the three layers of the blasto- derm. The upper layer, which is the epiblast already spoken of (Fig. ), takes at first but little share in these changes. In the lower layer, however, certain of the cells begin to get flattened horizontally, their granules become less numerous, and the nucleus becomes distinct; the cells so altered cohere together and form a membrane. The membrane thus formed, which is first completed in FiQ. Transverse Section through the Blastoderm of a Chick BEFORE THE APPEARANCE OF THE PRIMITIVE StRBAK. The epiblast is represented somewhat diagrammatically. The hyphens shew the points of junction of the two halves of the section. The hypoblast is already constituted as a membrane of flattened cells, and a number of scattered cells are seen between it and the epiblast. the centre of the pellucid area, constitutes the hypoblast. Between the hypoblastic membrane and the epiblast there remain a number of scattered cells (Fig. 13) which cannot however be said to form a definite layer altogether distinct from the hypoblast. They are almost entirely confined to the posterior part of the area pellucida, and 4,-2. 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 Foster, M. (Michael), Sir, 1836-1907; Balfour, Francis M. (Francis Maitland), 1851-1882; Sedgwick, Adam, 1854-1913; Heape, Walter, 1855-1929. London ; New York : Macmillan
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Keywords: ., bookcentury1800, bookdecade1880, bookpubli, booksubjectembryology
