=Heredity. The Mneme.=--The secret of heredity lies in the phenomena which have been just described. Hereditary influence preserves all its primary power and original qualities in the chromosomes, which enlarge and divide, while the vitelline substance, absorbed by the chromosomes and transformed by the vital chemical processes into the specific substance of the chromosomes, loses its specific and plastic vital energy, as completely as the food which we swallow loses its energy in forming the structure of our living organs. We do not acquire any of the characters of the ox by eating beefsteaks; and the spermatozoid, after eating much vitelline protoplasm, preserves its own hereditary energies, increased and fortified, but without change in their qualities. In this way the nuclear chromatin of our germinal cells becomes the carrier of all the hereditary qualities of the species (hereditary mneme), and more especially those of our direct ancestors. The uniformity of the intracellular phenomena in cell division and conjugation proves, however, that, without being capable of reproducing the individual, the other non-germinal cells of the body may also possess these hereditary energies, and that there exists, hidden behind all these facts, an unknown law of life, the explanation of which is reserved for the future. However, a recent work based on an idea of the physiologist, _E. Hering_, which looks upon instinct as a kind of memory of the species, opens up a new horizon. I refer to the book of _Richard Semon_: "The _mneme_ considered as the conservative principle in the transmutations of organic life." (_Die Mneme als erhaltendes Prinzip im Wechsel des organischen Geschehens_, Leipzig, 1904.) _Conception of Irritation._[1]--By the aid of the fundamental facts of morphological science, biological and psychological, _Semon_ proves that _Hering's_ idea is more than an analogy, and that there is a fundamental identity in the mechanism of organic life. In order to avoid the terminology of psychology which tends to be equivocal, _Semon_ employs some new terms to designate his new ideas, based on the fundamental conception of _irritation_ in its physiological sense. _Semon_ defines _irritation_ as an energetic action on the organism which determines a series of complicated changes in the irritable substance of the living organism. The condition of the organism thus modified, which lasts as long as the irritation, is called by _Semon_ the _state of irritation_. Before the action of irritation, the organism is in a condition which _Semon_ calls the _primary state of indifference_, and after its action, in the _secondary state of indifference_.