The conception of “prospective potency” was defined by its author H.Driesch as “the sum of the possible modes of development of a given part of the embryo”. However, in the language of science the word “potency” usually means “power”, not “possibility”. Therefore this conception from the beginning possessed a certain ambiguity, that it retained up to the present. The distinction of “active” and “passive” potency, introduced by Roux, has found no general acceptance. It appeared necessary to submit the conception of (...) “potency” to a profound analysis. In the first place it is shown, that the ambiguity of this conception vanishes, if we understand by the word “potency” those fundamental properties of the embryonic material, that are responsible for its various developmental possibilities. We can distinguish among these properties the “reactive powers”, by which the embryonic material reacts to inductive stimulations, and its own “developmental tendencies”. These faculties only differ by their strength; a “reactive power” may change into a “tendency”, when its intensity increases during development; conversely, a “tendency” may change into a mere “reactive power” by a decrease of its strength. The determination of the material results from the conflict of its tendencies. The inductive actions interfere by strengthening or weakening different tendencies, and by activating new tendencies by reinforcement of the “reactive powers” of the embryonic material.La conception de „prospektive Potenz” fut définie par son auteur H.Driesch comme „l'ensemble des modes de développement possibles d'une certaine partie de l'embryon”. Cependant, le, mot „Potenz” dans le langage de la science répond plutôt à la „puissance” qu'à la „possibilité”. De là résulte, que cette conception dès son origine avait une certaine ambiguïté, qui se fait sentir jusqu'à présent. La distinction entre „potentialité active” et „potentialité passive”, proposée par Roux, n'est pas acceptée généralement. Il se trouvait nécessaire, que la conception de „Potenz” fût soumise à une. analyse profonde. D'abord il est démontré, que l'ambiguïté de cette conception disparaît, si on entend par le mot „Potenz” les propriétés fondamentales du matériel embryonnaire, qui sont à la base de ses diverses possibilités de développement. On peut distinguer parmi ces propriétés les „pouvoirs réactifs”, en vertu desquels le matériel embryonnaire répond à des inductions morphogénétiques, et les „tendances propres” du matériel. Ils ne diffèrent que par leur intensité; un „pouvoir réactif” peut se changer en „tendance” par suite d'un renforcement au cours du développement, une „tendance” peut se changer en „pouvoir réactif” par une diminution d'intensité. La détermination du matériel se réalise par une „lutte” entre les tendances. Les actions inductives influent sur cette lutte en renforçant ou en diminuant l'intensité des diverses tendances, et en activant de nouvelles tendances par le renforcement de „pouvoirs réactifs”. (shrink)

The conception of “prospective potency” was defined by its author H.Driesch as “the sum of the possible modes of development of a given part of the embryo”. However, in the language of science the word “potency” usually means “power”, not “possibility”. Therefore this conception from the beginning possessed a certain ambiguity, that it retained up to the present. The distinction of “active” and “passive” potency, introduced by Roux, has found no general acceptance. It appeared necessary to submit the conception of (...) “potency” to a profound analysis. In the first place it is shown, that the ambiguity of this conception vanishes, if we understand by the word “potency” those fundamental properties of the embryonic material, that are responsible for its various developmental possibilities. We can distinguish among these properties the “reactive powers”, by which the embryonic material reacts to inductive stimulations, and its own “developmental tendencies”. These faculties only differ by their strength; a “reactive power” may change into a “tendency”, when its intensity increases during development; conversely, a “tendency” may change into a mere “reactive power” by a decrease of its strength. The determination of the material results from the conflict of its tendencies. The inductive actions interfere by strengthening or weakening different tendencies, and by activating new tendencies by reinforcement of the “reactive powers” of the embryonic material. (shrink)