Abstract
A wild gray house mouse (Mus musculus) bearing a small ventral spot was captured at Akhissar, Turkey. It was outcrossed and its progeny inbred. Pied segregates from this source were selected to produce a strain true-breeding for Akhissar spotting. Its range of variation in pure-breeds, its manifestation in hybrids, its recombination ratios in the F2 and backcross generations, and its linkage with recessive hairless prove it to be due to the gene which produces the recessive piebald variation commonly found in laboratory mice.