. Animal biology. Zoology; Biology. Fig. 56.—Sketches illustrating nematocysts and their action. A, a cnidoblast contain- ing an undischarged neraatocyst and possessing a cnidocil. B, the same with the nemato- cyst discharged. (A and B from Dahlgren and Kepner, '"Pririciples of Animal Histology," after Schneider.) C. portion of a tentacle, showing the batteries of nematocysts. D, an insect larva covered with nematocysts as a result of capture by a hydra. (C and D from Jennings, "Behavior of the Lower Organisms," by the courtesy of Columbia University Press.) E, last segment
. Animal biology. Zoology; Biology. Fig. 56.—Sketches illustrating nematocysts and their action. A, a cnidoblast contain- ing an undischarged neraatocyst and possessing a cnidocil. B, the same with the nemato- cyst discharged. (A and B from Dahlgren and Kepner, '"Pririciples of Animal Histology," after Schneider.) C. portion of a tentacle, showing the batteries of nematocysts. D, an insect larva covered with nematocysts as a result of capture by a hydra. (C and D from Jennings, "Behavior of the Lower Organisms," by the courtesy of Columbia University Press.) E, last segment of the leg of a small aquatic animal, with nematocysts of a barbless type shown coiled about its spines; this impedes the movements of the animal. {From Hegner. "College Zoology," after Toppe.) {A, B, and E are by the courtesy of The Macmillan Company.) tend to be concentrated around the mouth and at the base of each ten- tacle, where they act like sphincters. The nerve cells seem to be most numerous around the basal disc and on the hypostome, which indicates a certain degree of localization of nervous activity. Owing to the more complete network formed by its nerve cells, the ectoderm is more active and its movements are more definitely coordinated than are those of the entoderm. The nematocysts seem to be stimulated directly by chemicals in the water, such as the secretions from the body of the animals which serve as prey, and not by the nervous 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 Wolcott, Robert Henry, 1868-1934. New York ; London : McGraw-Hill Book Company, Inc.
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