"The Dead dominate the Living" for our physical
and mental inheritance is a mosaic made by our ancestors.
Variations which may or may not be inheritable do arise spontaneously, we know not how, and by variations all living things evolve.
A child resembles his parents more than strangers, not because they made cells "after their own image" but because both he and they got their factors from the same source.
Man's physical and mental, and the basis of his moral, qualities depend entirely on the types of ancestral plasm combined in marriage. Man may control his environment; his heritage is immutable. To suppress an undesirable trait the germ-cell must unite with one that has never shown it—one from a sound stock. An unsuitable mating in a later generation, however, may bring it out again (for factors are indestructible), and the individual showing it will have "reverted to ancestral type".
To give an instance: Does the son of a drunkard inherit a tendency to drink? No! The father is alcoholic because he lacks control, consequent upon the factors which make for control having been absent from his germ-plasm. He passes on this lack; if the mother does the same, the defect occurs—in a worse form—in the son. If the mother gives a control factor, the son may be unstable or apparently stable, this depending entirely on chance, but if the mother's plasm contains a strong control-factor, the defect will lie dormant in her son, who will have self-control, though if he marries the wrong woman he will have weak-willed children.
If the son becomes a toper, therefore, it is because he, like his father before him, was born with a defect—weak control—which might have made of him a drug-fiend, a tobacco-slave, a rake, or a criminal; in his home drink would naturally be the temptation nearest
to hand, and he would show his lack of control in drunkenness.
The way a lily-seed is treated makes a vast difference to the plant which arises. If sown in poor soil, and neglected, a dwarf, sickly plant will result; if sown in rich soil, and given every care that enthusiasm, money and skill can suggest or procure, the result will be magnificent.
So with man. A well-nourished mother, free from care and disease, may have a finer child than a half-starved woman, crushed by worry and work, but neither starvation nor nourishment alter the inborn character of the child.