ABSTRACT
The evolution of all life, plant as well as animal, depends upon the action of the following great forces, —heredity, reproduction, variation and environment. The older views were advanced by Lamarck and Darwin. Lamarck believed that organisms could be modified by environment, and such modifications occurring during the life of the animal could be passed along by organic inheritance. The only characteristics that can be passed along by organic inheritance are such as have been contained in the germinal substance of the egg and the sperm cell. The direct implication from this doctrine is that the condition of the body as a whole, apart from the germ cells, has no influence upon inheritance. Pearson, another authority, believes that parents have relatively more influence than grandparents, as indicated in the ratio, although accepting the general principle of the law of ancestral inheritance.
