Engrams may be associated simultaneously in space, such as those of sight. But they may also be associated in succession, such as those of hearing and of ontogeny. Simultaneous engrams are associated in every direction with the same intensity. Successive engrams, on the contrary, are associated more strongly forwards than backwards, and have only two poles. In the succession _a b_, _a_ acts more strongly on _b_ than _b_ on _a_. In the successions of engrams it often happens that two or more analogous engrams are associated in a manner more or less equivalent to a preceding engram. _Semon_ calls this phenomenon dichotomy, trichotomy, etc. But in the successions, two engrams cannot be ecphoriated simultaneously. Hence the phenomenon which _Semon_ names _alternating ecphoria_; that is sometimes one, sometimes the other of the constituent engrams, for example, of a dichotomy, which arrives at ecphoria. Similarly, the engram of the ecphoriated dichotomy is most often that which has been previously most often repeated. In the laws of ontogeny and heredity alternating ecphoria plays an important part. The branch less often repeated remains latent and the other only is ecphoriated. But certain combinations which reënforce the latent branch or paralyze the other may induce ecphoria of the first to the second generation. _Semon_ also shows that the phenomena of regeneration in the embryo, as well as those of the adult, obey the law of the mneme. _Homophony._--The terms engram and ecphoria correspond to the well-known introspective phenomena in psychology of memory and the association of ideas. Engrams are thus ecphoriated. At the time of such phenomena every mnemic irritation of the engrams vibrates simultaneously with the state of synchronous irritation produced by a new irritation. This simultaneous irritation is named by _Semon_ _homophony_. When a partial discord is produced between the new irritation and the mnemic irritation, the organism always tends to reëstablish homophony (harmony). This is seen in psychological introspection by activity of attention; in embryology by the phenomenon of regeneration; and in phylogeny by that of adaptation. Relying on these convincing facts, _Semon_ shows that irritative actions are only localized at first in their zone of entry (primary zone); but that afterward they irradiate or vibrate, gradually becoming weaker in the whole organism (not only in the nervous system, for they also act on plants). By this means, engraphia, although infinitely enfeebled, may finally reach the germinal cells. _Semon_ then shows how the most feeble engraphias may gradually arrive at ecphoria, as the result of numerous repetitions (in phylogeny after innumerable generations). This is how the mnemic principle allows us to conceive the possibility of an infinitely slow heredity of characters acquired by individuals, a heredity resulting from prolonged repetition.