Page:The Science of History and the Hope of Mankind.djvu/28



The operation of the manifold forces of nature, the attempts of each organism to utihse the environment according to its own needs, and the modification of its organs through the assimilation of the surrounding substances—all contribute their quota to its special growth and development. The life and individuality of each single organism are controlled and influenced by the sum-total of all those processes and products of Nature that arise out of the needs of every other organism for growth and development. And the modifications in the living world owing to the mutual alliance and rivalry of the organisms as well as the new forces that are being perpetually created by the eternal struggle for existence in the universe have their part to play in moulding the life-history