Basophilic cells in the guts of female ticks are derived from the basal remnants of type 2 secretory cells. As viewed by electron microscopy, these cells have microvilli uniformly distributed on the luminal surface, but they lack the abundant pinocytotic vesicles and lysosomes characteristic of digest cells. The cytoplasm is filled with well organized rough endoplasmic reticulum, Golgi complexes and secretory granules. Infoldings of a basal labyrinth extend the contact of the cell with the underlying haemolymph, and there are many mitochondria in the cell processes between folds. This morphology appears to fit the cell for functioning in active water transport across the gut wall. Subsequent to a final rapid phase of engorgement, the basophilic cell reorganizes its cisternae of rough endoplasmic reticulum into whorls and parallel arrays and resumes a secretory role.