. Elements of comparative anatomy. Anatomy, Comparative. 120 COMPARATIVE ANATOMY, ectoderm, and are the ova (o). They gradually form a layer of cells placed apparently between the ectoderm and endoderm, and give to the whole bud the appearance of an ovary. While these processes of differentiation are going on in the endoderm, a growth of cells from the ectoderm at the tip of the bud is extending inwards (A); as these cells become separated off from the ectoderm (B), they form a thin lamella, which grows around the ovarian layer, but which has no further function except in another kind of bud.
. Elements of comparative anatomy. Anatomy, Comparative. 120 COMPARATIVE ANATOMY, ectoderm, and are the ova (o). They gradually form a layer of cells placed apparently between the ectoderm and endoderm, and give to the whole bud the appearance of an ovary. While these processes of differentiation are going on in the endoderm, a growth of cells from the ectoderm at the tip of the bud is extending inwards (A); as these cells become separated off from the ectoderm (B), they form a thin lamella, which grows around the ovarian layer, but which has no further function except in another kind of bud. In the male bud, in fact, the ectoderm has the same characters, but the endoderm does not undergo any change, and simply forms a layer of cells, investing the gastric cavity without being differen- tiated into ova. The depressed portion of the ectoderm being developed to a great size, forms by constriction a layer between the ectoderm and endoderm (Fig. 48, ABC), the cells of which give rise, later on, to the morphological elements of the sperm. In this B. 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 Gegenbaur, C. (Carl), 1826-1903; Bell, F. J. (Francis Jeffrey), 1855-1924; Lankester, E. Ray (Edwin Ray), Sir, 1847-1929. London, Macmillan and Co.
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectanatomycomparative
