Page:Popular Science Monthly Volume 85.djvu/323

Rh, epilepsy and insanity are inherited, and that there is often a hereditary basis for nervous and phlegmatic temperaments, for emotional, judicial and calculating dispositions. Nor can it be denied that strength or weakness of will, a tendency to moral obliquity or rectitude, capacity or incapacity for the highest intellectual pursuits, occur frequently in certain families and appear to be inherited. In spite of certain noteworthy exceptions, which may perhaps be due to remarkable variations, statistics collected by Galton show that genius is hereditary; while the work of certain recent investigators, particularly Goddard, Davenport and Weeks, proves that feeble-mindedness and epilepsy are also inherited; and the careful work of Mott and of Rosanoff leaves no room for doubt that certain types of insanity are hereditary. It frequently happens that families in which hereditary insanity occurs also have other members afflicted with epilepsy, hysteria, alcoholism, etc., which would indicate that the thing inherited is an unstable condition of the nervous system which may take various forms under slightly different conditions. Woods has collected data concerning "Heredity in Royalty" which seem to show that very high or low grades of intellect and virtues may be traced through the royal families of Europe for several generations.

The general trend of all recent work on heredity is unmistakable, whether it concerns man or lower animals. The entire organism, consisting of structures and functions, body and mind, develops out of the germ, and the organization of the germ determines all the possibilities of development of the mind no less than of the body, though the actual realization of any possibility is dependent also upon environmental stimuli.

There are many limitations or exceptions to the general rule that children resemble their parents. Sometimes these differences are due to new combinations of ancestral characters, sometimes they are actually new characters not present so far as known in any of the ancestors, though even such new characters must arise from new combinations of the elements of old characters, as we shall see later.

1. New Combinations of Characters.—In all cases of sexually produced organisms new combinations of ancestral characters are evident. Usually a child inherits some traits from one parent and other traits from the other parent, so that it is a kind of mosaic of ancestral traits. Such inheritance, bit by bit, of this character from one progenitor and that from another was described by Galton as "particulate" (Fig. 47). On the other hand Galton supposed that in some instances a child might inherit all or nearly all of his traits from one parent; such inheritance he called "alternative" (Fig. 47).

In other cases the traits of the parents appear to blend in the offspring,