It is as though every dead fore-parent back to the dimmest horizon of time, were liable to put a ghostly finger in the pie, to mend or mar it.
Let us now use a simple illustration of the workings of heredity, variation, and atavism, or breeding back.
There is no need to trouble ourselves with the scientific explanations. What we have to understand is that children inherit qualities from their ancestors; that children vary from their ancestors and from each other; and that old types or old qualities may crop out suddenly and unexpectedly in a new generation. Knowing, as we do, that children inherit from their parents and fore-parents, the rest may be made, quite plain without a single scientific word.
In our illustration we will take for parents and children bottles, and for hereditary qualities beads of different colours.
THE MYSTERY OF DESCENT MADE EASY
Now, take a bottle of red beads, and call it male. Take a bottle of blue beads, and call it female.
From each bottle take a portion of beads; mix them in a third bottle and call it "child."
We have now a child of a red father and a blue mother; and we find that this child is not all red, nor all blue, but part red and part blue.
It is like the father, for it has red beads; it is like the mother, for it has blue beads.
It is unlike the father, for the father has no blue, and it is unlike the mother, for the mother has no red.