HEREDITY WITH VARIATION.
That an offspring always inherits from its parents many of their characteristics is well known; that it always varies, more or less, from them is also equally well known. Heredity and variation are twin forces that play upon every creature, holding it rigidly true to the parental type or compelling more or less divergence therefrom, according to the strength of the one or other power; so that every creature is the resultant of the activities of these two great parallel forces. Variation is coextensive with heredity, and every living creature gives evidence of the existence of variations.
Examples of Variations. No two leaves on a plant are exactly alike; no two children of the same parents give a perfect resemblance; no two individuals of the same species are molded in precisely the same pattern; of the thousands and thousands of faces that we observe in a city in the course of a year, each has some distinctive peculiarity.
The trained eye of the gardener recognizes each hyacinth among hundreds of bulbs; of the shepherd, each sheep in his flock; of the Laplander, each reindeer crowded in his herd like ants on the anthill. In a flock of 1,000 sheep each mother can even recognize a variation in the voice of her own lamb, all alike to us.
Every part of an animal is subject to variations, not only in bodily structure, but also in habits and instincts, and these variations are large in amount, numerous and diverse in character. Many observations, experiments and measurements that have been made at various times attest the truth of this assertion. Not only do variations take place in animals and plants under domestication, but also in the wild state.
Illustrations of Heredity. Mental heredity can be illustrated by studying the genealogies of such persons as Aristotle, Goethe, Darwin, Coleridge, Milton, etc. Probably the Bach family, of Germany, supply one of the best illustrations of the inheritance of intellectual character that we know of. The record of this family begins in 1550, lasting through eight generations to 1800. For about two centuries it gave to the world musicians and singers of high rank. The founder was Weit Bach, a baker of Presburg, who sought recreation from his routine work in song and music. For nearly two hundred years his descendants, who were very numerous in Franconia, Thuringia, and Saxony, retained a musical talent, being all church singers and organists.
When the members of the family had become very numerous and widely separated from one another, they decided to meet at a stated place once a year. Often more than a hundred persons—men, women and children—bearing the name of Bach were thus brought together. This family reunion continued until nearly the middle of the eighteenth century. In this family of musicians twenty-nine became eminent.