Abstract
The ultrastructure of the seminiferous tubule in the testis of magnesium-deficient rats is described. The boundary tissue was normal. Cells in the basal compartment were shrunken with large intercellular spaces except where desmosome-like junctions occurred. Cellular relations in the intermediate and adluminal compartments appeared normal but the SER in spermatids was less organised than in the control. There is extensive vesiculation of the SER in Sertoli cells. The role of the Sertoli cell in the maintenance of differences in the ionic compartments of the extratubular and intratubular milieu is discussed.