EXPERIMENTAL CYTOLOGICAL EVIDENCE FOR AN OUTWARD SECRETION OF WATER BY THE NEPHRIC TUBULE OF THE CRAYFISH

¹ From the Department of Zoölogy, The Johns Hopkins University and the Department of Tropical Medicine, The Tulane University

The majority of the cells of the distal half of the nephric tubule of the crayfish exhibit large, clear apical vacuoles at their luminal borders when the animal is in freshwater, its normal medium.

If the crayfish remains in a saline medium which is initially slightly hypertonic to the blood, for twenty-four hours or more, these vacuoles completely disappear. The condition is reversible upon return of the animal to freshwater. (The crayfish can maintain its vigor indefinitely in 210 mM. Nacl per liter, which is initially slightly hypertonic to the blood.)