For this sort of parallelism, the Lamarckian and Darwinian types of evolution by addition can offer no rational explanation. It could, perhaps, be accounted for upon the Batesonian hypothesis of evolution by loss of inhibition, that is to say, the coincident appearance of convergent characters in collateral lines might be interpreted as being due to a parallel loss in both lines of the inhibitive genes, which had suppressed the convergent feature in the primitive or common stock. We say that the convergence _might_ be so interpreted, because the interpretation in question would, at best, be merely optional and not at all necessary; for in the third, or adaptational, type of convergence, we shall see instances of parallel modifications occurring in completely independent races, whose morphology and history alike exclude all possibility of hereditary connection between them. Hence, even in the present case, nothing constrains us to accept the genetic interpretation. (2) Radical convergence, which Woods styles heterogenetic homœomorphy, is described by him as follows: “Sometimes two groups of individuals resemble each other so closely that they might be regarded as belonging to the same genus or even to _the same species_ (italics mine), but they have descended from different ancestors since they are found to differ in development (ontogeny) or in their palæontological history; this phenomenon, of forms belonging to different stocks approaching one another in character, is known as convergence or heterogenetic homœomorphy, and may occur at the same geological period or at widely separated intervals. Thus the form of oyster known as _Gryphaea_ has originated independently from oysters of the ordinary type in the Lias, in the Oölites, and again in the Chalk; these forms found at different horizons closely resemble one another and have usually been regarded as belonging to one genus (_Gryphaea_), but they have no direct genetic connection with one another.” (“Palæontology,” 5th ed., 1919, p. 15.) Comment is almost superfluous. If even _specific_ resemblance is no proof of common origin, then what right have we to interpret any resemblance whatever in this sense? With such an admission, the whole bottom drops out of the evolutionary argument. When the theory of descent is forced to account for heterogenetic resemblance at expense of all likelihood and consistency, when it cannot save itself except by blowing hot and cold with one breath, one is tempted to exclaim: “Oh, why bother with it!”