Transfer to chick embryos of incompatible DNA.

After the transfer of chicken DNA to chick embryos incompatible at the B locus a retardation of growth was observed. Retarded differentiation of muscle fibres was histochemically detected in hatched chicks by the demonstration of enzymatic activities. The manifestations of apparent weakness of the dorsal muscles resembled a "myasthenia-like" syndrome. Infection with Marek's disease virus was not responsible for the damage caused by transferred DNA.