dogma, and whoever ventures to disturb its foundations must be burnt as a heretic. [19] Oscar Hertwig, _Zeit- und Streitfragen der Biologie_, Jena, 1894. [20] Nor will those, who demand a demonstration of "how the biophores and determinants are constituted in every case, and must be arranged in the architecture of the germ-plasm." (O. Hertwig, _loc. cit._, p. 137). As if any living being could have the temerity even so much as to guess at the actual ultimate phenomena in evolution and heredity! The whole question is a matter of symbols only, just as it is in the matter of "forces," "atoms," "ether undulations," etc., the only difference being that in biology we stumble much earlier upon the unknown than in physics. [21] "Beitraege zur Kritik der Darwin'schen Lehre," _Biologisches Centralblatt_, Vol. X., p. 449. 1890. [22] Poulton has adverted to the fact that this is nevertheless not always the case; for example, it is not so with the teeth, whose shape it had also been sought to reduce to the mechanical effects of pressure and friction. See "The Theory of Selection" in _The Proceedings of the Boston Society of Natural History_, Vol. XX., page 389. 1894. [23] As the highest stage of selective processes must be regarded that between the highest biological units, the colonies or cormi--a stage, however, which is not essentially different from personal selection. In this stage the persons enact the part that the organs play in personal selection. Like their prototypes they also battle with one another for food and in this way maintain harmony in the colony. But the result of the struggle endures only during the life of the individual colony and can be transmitted through the germ-cells to the following generation as little as can histological changes provoked by use in the individual person. Only that which issues from the germ has duration. [24] This statement has often been declared extravagant, and it is so if it is taken in its strict literalness. On the other hand, it would also seem, by a more liberal interpretation, as if there existed non-adaptive characters, for example, rudimentary organs. Adaptiveness, however, is never absolute but always conditioned, that is, is never greater than outward and inward circumstances permit. Moreover, an organ can only disappear gradually and slowly when it has become superfluous; yet this does not prevent our recognising every stage of its degeneration as adapted when compared with its precursor. Further, it does not militate against the correctness of the above proposition that there are also characters whose fitness consists in their being the necessary accompaniments of other directly adapted features, as, for instance, the red color of the blood. [25] Semper, _Die natuerlichen Existenzbedingungen der Thiere_, Leipsic, 1880, pp. 218-219.