. Fresh-water biology. Freshwater biology. 294 FRESH-WATER BIOLOGY 187 (190) Stalk retractile. 1S8 (i? Zooids contracting independently. Bodies bell-shaped. Central muscle interrupted at the union of the stalk and the branch. Ciliated spiral forming about one and a half circles. Nu- cleus horseshoe-shaped. . Carchesium Ehrenberg. Representative species. Carchesium polypinum Kent 1882. Colonies often reaching a lieight of one-eighth of an inch. At- tached to the under surfaces of stones or floating sticks in fresh- water pools or running streams. The colony may be the temporary host of Ampkilep
. Fresh-water biology. Freshwater biology. 294 FRESH-WATER BIOLOGY 187 (190) Stalk retractile. 1S8 (i? Zooids contracting independently. Bodies bell-shaped. Central muscle interrupted at the union of the stalk and the branch. Ciliated spiral forming about one and a half circles. Nu- cleus horseshoe-shaped. . Carchesium Ehrenberg. Representative species. Carchesium polypinum Kent 1882. Colonies often reaching a lieight of one-eighth of an inch. At- tached to the under surfaces of stones or floating sticks in fresh- water pools or running streams. The colony may be the temporary host of Ampkileptus meleagris. Length of zooids S° f- . Some interesting work has been done on the nucleus of this species by Miss M. Greenwood. (The Journal of Physiology, Vol. XX, pp. 427-454.) It was found that the normal activity causes a drain on the organism which, if not offset by sufficient repair due to the lack of nutrition, results in the more fluid char- acter of the macrosomes of the nucleus. Fig. 542. Carchesium polypinum. Terminal branch with two zooids; tnactif macronucleus. X 500. (After Kent.). 189 (188) Zooids contracting together. Bodies very similar to Carchesium but central muscle continuous, causing all of the zooids to contract together. . Zoothamnium Stein. Representative species. . Zoothamnium adamsi Stokes 1885. Bodies about twice as long as broad, tapering to the pedicel; finely striated transversely. Length of zooids 60II. Reported from Niagara River. Attached to 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 Ward, Henry Baldwin, 1865-1945; Whipple, George Chandler, 1866-1924. joint author. New York, John Wiley & sons, inc. ; [etc. ,etc. ]
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