It may be well here to consider the objections raised by the Weissman theory that "acquired traits are not transmissible." To those who believe this it seems useless to try to improve a race by development of the young with a view to transmission. They hold that the child inherits a certain group of faculties, differing from the parents perhaps through the "tendency to vary," and that, although you may improve the individual indefinitely through education, that improvement is not transmissible to his offspring. The original faculties may be transmitted, but not the individual modification. Thus they would hold that, if two brothers inherited the same kind and amount of brain power, and one brother was submitted to the finest educational environment, while the other was entirely neglected, yet the children of the two brothers would inherit the same amount of brain development: the training and exercise which so visibly improved the brain of the educated brother would be lost to his children.
Or, if two brothers inherited the same physical constitution, and one developed and improved it by judicious care and exercise, while the other wasted strength and contracted disease, the children of either would inherit the original constitutional tendencies of the parent, unaffected by that parent's previous career.
This would mean that the whole tremendous march of race-modification has been made under no other influence than the tendency to vary, and that individual modification in no way affects the race.
Successive generations of individuals may be affected by the cumulative pressure of progress, but not the race itself. Under this view the Fuegian baby would be as valuable an investment as the English baby, unless, indeed, successive and singularly connected tendencies to vary had worked long upon the English stock and peculiarly neglected the Fuegian. In proof of this claim that "acquired traits are not transmissible," an overwhelming series of experiments are presented, as wherein many consecutive generations of peaceful guinea pigs are mutilated in precisely the same way, and, lo! the last guinea pig is born as four-legged and symmetrically-featured as the first.
If it had been so arranged that the crippled guinea pigs obtained some advantage because of their injuries, they might have thus become "fittest"; and the "tendency to vary" would perhaps have launched out a cripple somewhere, and so evolved a triumphant line of three-legged guinea pigs.
But, as proven by these carefully conducted scientific experiments, it does not "modify the species" at all to cut off its legs,—not in a score of generations. It modifies the immediate pig, of course, and is doubtless unpleasant to him; but the effect is lost with his death.
It has always seemed to me that there was a large difference between a mutilation and an acquired trait. An acquired trait is something that one uses and developes, not something one has lost.
The children of a soldier are supposed to inherit something of his courage and his habit of obedience, not his wooden leg.
The dwindled feet of the Chinese ladies are not transmitted; but the Chinese habits are. The individual is most modified by what he does, not by what is done to him; and so is the race.
Let a new experiment be performed on the long-suffering guinea pig. Take two flourishing pair of the same family (fortunately, the tendency to vary appears to be but slight in guinea pigs, so there is not serious trouble from that source), and let one pair of guinea pigs be lodged in a small but comfortable cage, and fed and fed and fed,—not to excess, but so as to supply all guinea-piggian desires as soon as felt,—them and their descendants in their unnumbered generations. Let the other pair be started on a long, slow, cautious, delicate but inexorable system of exercise, not exercise involving any advantage, with careful mating of the most lively,—for this would be claimed as showing only the "tendency to vary" and "survival of the fittest,"—but exercise forced upon the unwilling piggies to no profit whatever.