Abstract
We used the electron microscope to study the evolution of the stria vascularis from a single layer of cuboidal ectodermal cells resting on spiral ligament fibroblasts to a composite epithelium of several layers of three different kinds of cells. In the process, complicated interdigitations form between neighboring cells which greatly increase surface area and would seem to increase fluid transport capacity. The number of microvilli decreases and each marginal cell's kinocilium disappears during the second week after birth. However, there is an increase in the number of clear, fluid-containing vesicles in the superficial part of the marginal cells.