The stimulus exerts its influence unequally upon the specific activity of the motor elements of different parts of the surface of the cell body. This difference in response causes the axis of the freely moving organism to assume a different direction in which to move. It is _compelled_ to move in a definite direction and so, in this field, the apparently mysterious attraction and repulsion of living organisms toward stimuli has, by means of the most simple analysis, been robbed of its mystical character. [9] _Claude Bernard_: “Lecons sur les phénomènes de la vie communs aux animaux et aux végétaux.” Paris 1878. [10] _Ehrenberg_: “Die Infusionstiere als vollkommene Organismen.” Leipzig 1838. Finally, I should like to touch briefly upon a view of the irritability of living substance which has recently been brought forward by _Semon_.[11] It assumes the proportions of a whole system and is proclaimed as a basis for the comprehension of organic phenomena. It originated with an idea which _Hering_[12] developed many years ago and which later was accepted by _Haeckel_,[13] namely that heredity is a species of memory of the living substance. _Semon_ attributes to living substance, in contrast to non-living, a “_Mneme_.” By “_Mneme_” he understands the capability of living substance to assume, through the influence of a stimulus, a permanently altered condition. The latent alteration resulting from the stimulus he terms “_Engramm_.” These “_Engramms_” can later, however, not only be activated by the reapplication of the original stimulus, but also by other stimuli, so that the state of excitation once brought about by the original stimulus reappears. _Semon_ calls the reproduction of the state of primary excitation by a later stimulus “_Ekphorie_.” A great number of other new word formations, such as “_chronogene Engramme_,” “_phasogene Ekphorie_,” “_mnemische Homophonie_,” “_mnemisches Protomer_” and countless others are supposed to serve for the better understanding of a series of special facts, chiefly in the domain of the processes of heredity. That which is termed “_Mneme_” and “_Engramm_” is not further analyzed. _Semon_ expressly declines to discuss the kind of alterations in which the physical or chemical nature of an “_Engramm_” consists. Hence physiological analysis has not been advanced in any way by _Semon’s_ new formation of words applied to long-known facts. With a series of new expressions the originator of the “_Mneme doctrine_” deceives himself, as well as a number of his readers not endowed with the critical faculty, into supposing that he has achieved a serious analysis. Of such, however, there is not a trace. As can be conceived, this way of treating the manifestations of life has met with no further attention from the physiological side. For indeed, what physiologist would consider that the fact of muscle responding by a contraction to an induction shock, or to any other stimulus, is sufficiently