The Water Relations of Earthworms

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Abstract
1. Suitable media have been found for maintaining the activity of the nephridiostome cilia of two earthworm species for about 24 hr. at 18° C. or below. 2. The nephridiostome cilia of Lumbricus terrestris are less resistant to hypotonic media, and more resistant to hypertonic media, than those of Allolobophora chlorotica. 3. When the medium is suddenly diluted, the nephridiostome cilia of L. terrestris and A. chlorotica have a period of hyperactivity and/or increased amplitude of the beat followed by a return to normal activity. The temporary effect after a change to a hypertonic medium takes the form of decreased activity or inhibition. 4. In hypotonic solutions, vesicles are formed on the marginal cells and later disappear provided the dilution has not been too great. 5. A change in the osmotic concentration of the medium is responsible for the vesicles and the temporary effects on the cilia, whereas the inorganic ion concentration is responsible for the long-term effects. 6. There is no axial gradient affecting the activity of the nephridiostome cilia in relation to the osmotic concentration of the medium. 7. No differences were detected between garden and Lake Windermere specimens of A. chlorotica.