Secondary nucleation by seeding in stagnant and agitated aqueous sodium chlorate solutions was investigated with the purpose of determining the origin of nuclei - i.e. the crystal seed or the superstaurated solution - and elucidating the mechanism of nuclei breeding. Sodium chlorate crystallizes in two enantiomeric (chiral) forms. Seeds of one chirality were used and the chirality of the secondary nuclei was determined. At low supercooling all nuclei were of the same chirality as the seed pointing to the seed as their origin. At relatively high, but still lower than the critical value for spontaneous nucleation, supercoolings many nuclei with opposite chirality to that of the seed were formed. This phenomenon points to the solution around the seed as the origin of the nuclei and it was predicted by the Embryos Coagulation Secondary Nucleation (ECSN) mechanism previously proposed by the authors. This mechanism explains the above findings as well as data obtained in non-seeded nucleation and in heterogeneous nucleations on Teflon shavings. It also accounts for the observed random fluctuation, from run to run, in the total number of nuclei and in the percentage of nuclei with chirality opposite to that of the seed.