Gottfried sum from the ratioF2n/F2p

Experimental results obtained at the CERN Super Proton Synchrotron on the structure-function ratio ${\mathit{F}}_2^{\mathit{n}}$/${\mathit{F}}_2^{\mathit{p}}$ in the kinematic range 0.004<x<0.8 and 0.4<${\mathit{Q}}^2$<190 ${\mathrm{GeV}}^2$, together with the structure function ${\mathit{F}}_2^{\mathit{d}}$ determined from a fit to published data, are used to derive the difference ${\mathit{F}}_2^{\mathit{p}}$(x)-${\mathit{F}}_2^{\mathit{n}}$(x). The value of the Gottfried sum F(${\mathit{F}}_2^{\mathit{p}}$-${\mathit{F}}_2^{\mathit{n}}$)dx/x=0.240±0.016 is below the quark-parton-model expectation of 1/3.