A butterfly with the genotype smiles can produce a stiles, smiley, or a smiler mutant. A stiles, in turn, can produce a smiles mutant. A smiler can produce a soiler or a smiley mutant. A smiley can produce a smiles or a smiler. A soiler can produce a soiled, boiled, or toiler mutant. A soiled can produce a soiler or a boiled. A boiled can produce a boiler or a soiler. This illustration shows that even if a mutation goes in an undesired direction, for example soiler to boiler, in the next generation a mutation in the desired direction (to toiler) may occur. Therefore, there are a number of routes, several indirect and one direct, to the desired form of toiler.