Measurements of the static capacity per cm.2 of membrane for the red corpuscle as changed when the cells are made spherical by the addition of lecithin or rose bengal, show a slight increase of capacity, indicating a thinning of the membrane, although the change is not large enough to make it certain that it is real. Furthermore, the membrane capacity shows a slight decrease when spherical cells are swollen in hypotonic saline, indicating a thickening of the membrane, although the change is hardly outside the experimental error. The fact that there is no increase in capacity lends support to the theory that as the cell swells the membrane does not stretch but new material comes from the interior of the cell to make a new portion of the membrane.