. Zoology. Zoology. Fig. 15.—Development of a sponge (Fiycon ciliatum). A, B, morula seen in sec- tion; c, segmentation cavity; C, blastula stage ; D. gastrula about to be- come stationary, with a few spicules; £, sponge become stationar}', with spicules. Highly magnified. cells; the sponge, then, has myriads of mouths and stom- achs (Fig. 14). Sponges develop, like all the higher animals, from true eggs. The egg, after fertilization, begins to grow, and divides into two, four, eight, sixteen, and more spheres, until it looks like a mulberry, which seen in section is as in Pig. 15, .^4, i?. Th
. Zoology. Zoology. Fig. 15.—Development of a sponge (Fiycon ciliatum). A, B, morula seen in sec- tion; c, segmentation cavity; C, blastula stage ; D. gastrula about to be- come stationary, with a few spicules; £, sponge become stationar}', with spicules. Highly magnified. cells; the sponge, then, has myriads of mouths and stom- achs (Fig. 14). Sponges develop, like all the higher animals, from true eggs. The egg, after fertilization, begins to grow, and divides into two, four, eight, sixteen, and more spheres, until it looks like a mulberry, which seen in section is as in Pig. 15, .^4, i?. This is the segmentation stage or morula. The cells farther multijjly, and arrange themselves into a single fig. le.—ciliated embryo or bias- 1 1 ii 1, • 11 J tula of a sponge (&';/cant/7Tf ?'a- layer, when the embryo is called phanus). (Hifhiy magnified.) a blastula. Some of the cells are ciliated, and as a blastula the embryo leaves the parent sponge and swims about in the sea (Fig. 16 and Fig. 15, C).. 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 Packard, A. S. (Alpheus Spring), 1839-1905. N. Y. , Holt
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1897
