EXPERIMENTS ON LIGIA IN BERMUDA

VII. FURTHER EFFECTS OF SODIUM, AMMONIUM AND MAGNESIUM

¹ From the Osborn Zoölogical Laboratory, Yale University, and the Bermuda Biological Station

1. Filter paper moistened with M NaCl is approximately six times as repellent to Ligia as sea water paper.

2. An equal distribution of isopods occurs between filter papers containing 3.7/8 M MgCl₂ and distilled water.

3. Of all ions tested, the most pronounced aversion is shown for NH₄Cl paper (in concentrations of 1/30 M and above).

4. The tendency of Ligia to collect on a filter paper containing distilled water when the other paper contains sea water is not prevented by the removal of the antennae or by removal of the mechanism for flushing the gills (seventh legs and uropods).

5. Young isopods immediately after release from the brood pouch have a marked aversion for filter paper containing 5/8 M NaCl or sea water. Their tolerance for immersion in sea water is greater than that of adults.

6. The distribution of Ligia on filter paper containing distilled water, sea water, or other salt solutions is probably determined by two factors: (a) the salt requirements of the organism and (b) the stimulating effect of salt on the leg movements.

7. The survival of Ligia in 50 per cent sea water is prolonged by oxygenation.