He had always held that the "non-transmissability of acquired traits" was not established by any number of curtailed mice or crop-eared rats.

"A mutilation is not an acquired trait," he protested.

"An acquired trait is one gained by exercise; it modifies the whole organism.

It must have an effect on the race.

We expect the sons of a line of soldiers to inherit their fathers' courage--perhaps his habit of obedience--but not his wooden leg." To establish his views he selected from a fine family of guinea-pigs two pair; set the one, Pair A, in conditions of ordinary guinea-pig bliss, and subjected the other, Pair B, to a course of discipline.