So, instead of trying to find the ideal type or the ideal average, he'd always look for the exception. So, in this example, which is an example of what's called Bateson's Rule, he has two kinds of mutations of a human thumb.
Entonces, en vez de buscar el tipo ideal o el promedio ideal, siempre buscaba la excepción. En este ejemplo de la Regla de Bateson hay dos tipos de mutaciones de un pulgar humano.