Before revision:  The probability of existence of accessible paths between two genotypes at a distance linear in L displays a sharp transition from 0 to 1 at a threshold value \beta^\ast of the fitness difference between the initial and final genotype.
After revision:  The probability of existence of accessible paths between two genotypes at a distance linear in L displays a sharp transition from 0 to 1 at a threshold \beta_c for the fitness difference between the initial and final genotype.