A moment’s reflection, however, will make it clear that, in thus confounding the definition proper with its theoretical interpretation, the modern biologist is guilty of a logical atrocity. Homology, after all, is a simple anatomical fact, which can be quite adequately defined in terms of observation; nor is the definition improved in the least by having its factual elements diluted with explanatory theory. On the contrary, the definition is decidedly weakened by such redundancy. And as for those who insist on defining homology in terms of atavistic assumption instead of structural affinity, their procedure is tantamount to defining the clear by means of the obscure, an actual effect by means of a possible cause. Moreover, this attempt to load the dice in favor of Transformism by tampering with the definition of homology ends by defeating its own purpose. For, if homology is to serve as a legitimate argument for evolution, then obviously evolution must not be included in its definition; otherwise, the conclusion is anticipated in the premise, the question is begged, and the argument itself rendered a vicious circle. Having formed a sufficiently clear conception of homology as a static fact, we are now in a position to consider the problem of its causality with reference to the solution proposed by evolutionists. Transmutation, they tell us, results from the interaction of a twofold process, namely, the conservative and similifying process called _inheritance_, and progressive and diversifying process known as _variation_. Inheritance by transmitting the ancestral likeness tends to bring about uniformity. Variation by diverting old currents into new channels adjust organisms to new situations and brings about modification. Homology, therefore, is the effect of inheritance, while adaptedness or modification is the product of variation.