Ueber Den Geotropismus Niederer Organismen

Ueber Den Geotropismus Niederer Organismen

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1892 edition. Excerpt: ... seems however to be nothing known to suggest this possibility. The evident result of the positive chemotaxis of Paramoecium toward ' CO, is the gathering together of the infusoria into dense collections, but what purpose is served by these collections does not appear. The attraction of Paramoecia toward self-excreted CO, seems to throw light on a general question proposed by Pfeffer; namely, whether it is necessary, in order that a substance should act as an attractive stimulus, that it should be taken into the organism. As the CO, in the water was first produced within the Paramoecia, and acts as a stimulus after it has been given off to the outside, it appears that the stimulus must be an external one; Pfeffer's question, in accordance with this, is to be answered in the negative. 6. SUMMARY. 1. Paramoecium aurelia is strongly positively chemotactic to a solution of carbon dioxide in water. Carbon dioxide is excreted by the Paramoecia in quantities sufficient to be detected with proper reagents. By this excreted CO, the infusoria are attracted; hence they tend to gather into dense groups. This positive chemotaxis to the carbon dioxide excreted by themselves plays a very large part in the normal activities of Paramoecia. 2. Paramoecium is also positively chemotactic toward all weak acids and all solutions having an acid reaction, so far as tested. Toward strong solutions of all acids, including CO, the infusoria are negatively chemotactic. 3. Paramoecium aurelia is negatively chemotactic to the fluid (water containing decaying vegetable matter) in which it lives and thrives. This fluid has an alkaline reaction. Paramoecium is likewise negatively chemotactic, so far as tested, to all solutions having an alkaline reaction. It...show more

Product details

  • Paperback | 112 pages
  • 189 x 246 x 6mm | 213g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236835247
  • 9781236835246