Gedanken über Vererbung

Abstract

THE author thinks that clearnessis gained if we regard the organism as a continually changing mechanical system with a life-cycle extending from the arbitrarily chosen moment of oogenesis to the post-mortem death of the last scrap of decaying tissue. An acquired character is the result of a reaction of the system to external influences, and presupposes a definite heritable structure capable of reacting, so that there is no sharp boundary between acquired and inherited characters. What is called a heritable character may be due to a coincidence of successive reactions. The concept of heredity strictly applies only to the germcells; it is simply “the process which leads to the formation of germ-cells whose structure is the same as or like the parental germ-cells.” Development is the expression of this structure, and the formative causes of development lie in the relation between the system and its environment. An animate system can only exist in definite conditions, which can only oscillate within definite limits. Life is an adjustment between the amplitudes of variation in the animate system and in the environment, and involves a progressive limitation of the organismal variability. Those variations the causes of which lie in the oscillations of the germ-cell structure may be called gametogenous or endogenous as contrasted with exogenous variations (modifications) which are acquired in the course of life. This distinction will hold even if we abandon the theory of the continuity of the germ-plasm, and simply suppose that the germcells are those cells which through chemical reactions have attained the same structure as the parental germcells. When this sameness is not attained variations result, the amplitude of which may be trivial or fatal, or it may be that a new pattern of system results which we call a mutation. So far as we can see, the author simply re-states familiar facts and ideas in a slightly novel way, and we do not share his confidence that clearness is gained by so doing. Gedanken über Vererbung. Dr. Alexander Petrunkewitsch. Pp. 83. (Freiburg, i. B.: Speyer and Kaerner, 1904.) Price 1.80 marks.