. Zoology : for students and general readers . Zoology. THE POLTZOA. 181 The simpler form of Polyzoon is a worm-like creature enclosed in a minute, deep, horny cell, with the alimentary canal bent on itself and terminating in a vent situated near the mouth, the latter surrounded, in the fresh-water Fig. 125.—Branching marine Polyzoon. Corm of Myriozoum subgradle, natural size. with a horseshoe-shaped crown, or in the marine species a circle of slender ciliated tentacles. The animal when dis- turbed withdraws into its tube or shell, which is often trans- parent, allowing it to be examin
. Zoology : for students and general readers . Zoology. THE POLTZOA. 181 The simpler form of Polyzoon is a worm-like creature enclosed in a minute, deep, horny cell, with the alimentary canal bent on itself and terminating in a vent situated near the mouth, the latter surrounded, in the fresh-water Fig. 125.—Branching marine Polyzoon. Corm of Myriozoum subgradle, natural size. with a horseshoe-shaped crown, or in the marine species a circle of slender ciliated tentacles. The animal when dis- turbed withdraws into its tube or shell, which is often trans- parent, allowing it to be examined when alive. The cells are rarely single, but a cornius, polyzoarium or polyzoon-stock is formed by the bud- ding of numerous cells from the one first formed. The single polyzoon is called & polypide, and its cell a cystid. In Pedicellina, the simplest polyzoon, tlie polypide has no cystid or cell. The cells are, in the marine forms, usually closed, and independent of each other. The wall forming the cell is called the endocyd; it com- prises the ectoderm proper, with a portion (parietal layer) of the mesoderm forming the soft lining of the 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. New York : Henry Holt
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1879
