On Some Interactions of Organisms

Abstract

While the structural relations of living organisms, as expressed in a classification, can best he figured by a tree—the various groups, pest and present, being related to each other either as twigs to twigs, as twigs to branches,or as branches to the main stem—yet this illustration does not at all express their functional relations. While the anatomical characters of the various groups may show that they are all branches of a common stock, from which they have arisen by repeated divisions and continued divergences, the history of their lives will show that they are now much more intimately and variously bound together by mutual interactions then are twigs of the same branch—that with respect to their vital activities they occupy rather the relation of organs of the same animal body.