. Text book of zoology. Zoology. Pig. 30. Different stages in the development of the ovum of a Water-snail (Planorbis). 1—2 Stages in the segmentation, 3 section of a blastula (the large hypoblast cells are seen below), 4 gastrula, en hypoblast, hh segmentation cavity, m mesoblast, o blastopore, r polar-bodies.—After Eabl. The early development of a large number of animals takes place in one of these ways; Coelentera (for these see also p. 45), Porifera, Echinoderma, many Worms, Molluscs, one Vertebrate (Amphioxus), Tunioata. 3. In some cases (Fig. 31) which otherwise adhere to the order descr
. Text book of zoology. Zoology. Pig. 30. Different stages in the development of the ovum of a Water-snail (Planorbis). 1—2 Stages in the segmentation, 3 section of a blastula (the large hypoblast cells are seen below), 4 gastrula, en hypoblast, hh segmentation cavity, m mesoblast, o blastopore, r polar-bodies.—After Eabl. The early development of a large number of animals takes place in one of these ways; Coelentera (for these see also p. 45), Porifera, Echinoderma, many Worms, Molluscs, one Vertebrate (Amphioxus), Tunioata. 3. In some cases (Fig. 31) which otherwise adhere to the order described under (2), the cells which form the hypoblast are very. Pig. 31. Section through the egg of a Chsetopod (Nereis) at different stages of development. In 3, the gastrula is fully formed, but the blastopore (below, to the left) is still open ; in 4 it is closed, and the formation of the mouth (s) has begun, elc epiblast en hypoblast, / oil globules, m mesoblast, s developing mouth. The vitelline membrane is removed in the first three figures, present in the last.—After 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 Boas, J. E. V. (Johan Erik Vesti), 1855-1935; Boas, J. E. V. (Johan Erik Vesti), 1855-1935. Lehrbuch der Zoologie. London, Sampson Low, Marston
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1896
