A high percentage of surviving clones of F1 and F2 generations was observed in intra- and inter-strain crosses of the studied Romanian strains. A similar survival was also found in the inter-strain crosses of the Romanian strains with the standard (324) strain of the species, and in the crosses of both Romanian strains with the strains from Spain. Hybrids of the inter-strain crosses did not show any cytological disorders in the nuclear apparatus. The results prove the absence of genetic barriers between the studied strains, coming from Romania and Spain, and the American one.
E.Przybos, Department of Experimental Zoology, Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Slawkowska 17, 31-016 Krakow, Poland