. Text-book of zoology for junior students. Zoology. 1S8 IX^: AXnrALS. each consisting iif a numbev of distinct but similar zouids, produced by gemmation from a single primordial individual. The colonies thus i>roduceil are very generally j)rotected l.)y a horny or chitinous integument, and tliey are so like the Hydroid Zoophj-tes that they were long described as sucli. Indeed, the only absolute distinction between the two classes is to be fo\ind in the internal structure of the zoijids of each. The separate beings or zooids which collec- tively constitute the colony of any J'n
. Text-book of zoology for junior students. Zoology. 1S8 IX^: AXnrALS. each consisting iif a numbev of distinct but similar zouids, produced by gemmation from a single primordial individual. The colonies thus i>roduceil are very generally j)rotected l.)y a horny or chitinous integument, and tliey are so like the Hydroid Zoophj-tes that they were long described as sucli. Indeed, the only absolute distinction between the two classes is to be fo\ind in the internal structure of the zoijids of each. The separate beings or zooids which collec- tively constitute the colony of any J'nji/:i}iiii are spoken of as " poly- pides "—the ienn po/>/pi/i/ lieing only used in connection with the Jfi/drnzo'i, and the ternj /ic/i/j)' being similarly restricted to the Artiiioznii. Each jiolypide in a ty|iical J'(i/i/:i«in has the following structure (fig. 132, 2) : The body of tlie animal is enclosed in a double-walled sac, of which the outer layer is usually chitinous or calcareous, and constitutes a "cell" in wliicli the ZDiiid is contained. This outer layer is known as the "ectucyst" to it from the ecto-. 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 Nicholson, Henry Alleyne, 1844-1899. New York, American Book Co
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1885
