There is sufficient reason to believe that ax^Jand ax represent the same mutation. The kreisler stock was imported to The Jackson Laboratory from Edinburgh in 1952. The ax^J mutation arose at The Jackson Laboratory in the kreisler stock in 1953 and was originally called paralytic. Mary Lyon, also in Edinburgh, reported the ataxia mutation shortly thereafter. Paralytic heterozygotes were sent to Mary Lyon and found to be allelic with her ataxia mutant. Thus the name was changed from paralytic to ataxia. The Jackson Laboratory investigated the possibility that ax and ax^J were really the same strain. Examination of the original shipping records and pedigree numbers showed that the original kreisler male and female mice shipped to the laboratory in 1952, were potentially heterozygote for the ax mutation (J:58683).