A most significant fact in regard to the linkage shown by the Drosophila mutants is that the number of linked groups corresponds to the number of pairs of the chromosomes.
"Sex-linked Inheritance in Drosophila"
Thomas Hunt Morgan Calvin B. Bridges
No mutants or Roving Intelligences allowed.
"Sympathetic Magic"
Paul Cameron Brown
In many cases, their children were mutants-not monsters, although there were many of them, too, which did not survive-but humans who were immune to radioactivity."
"Flight From Tomorrow"
Henry Beam Piper