It is suggested that the constituent quarks entering the SU(6)-scheme of hadrons have an explicit internal spin structure in terms of quarks and gluons. The gluonic contribution to the nucleon spin can be calculated in terms of gA/gV, which gives 25%. The gluonic sea is positively polarized. The recent experimental results of polarized electroproduction can be understood. Predictions about leptoproduction off neutron targets are made.