The important problem now presents itself: What is the material, the matter, which is handed down from generation to generation as the basis of inheritance? Weismann, as we know, regarded it as a very complicated structure, part of which by its disintegration became the foundation of individual embryology. We have disproved, on the authority of many facts, the latter part of this assumption; but of course the first part of it may turn out to be true in spite of this. We have no means at present to enable us to say a priori anything positive or negative about the important question of the nature of that matter, the continuity of which in inheritance is in some sense a self-evident fact, and we therefore shall postpone the answer until a later point of our analytical discussion.
On Certain Theories which Seek to Compare Inheritance to Memory
It will be advisable first to study some other theoretical views which have been put forward with regard to inheritance. The physiologist Hering, as early as 1876, compared all heredity to the well-known fact of memory, assuming, so to say, a sort of remembrance of all that has happened to the species in the continuity of its generations; and several German authors, especially Semon, have lately made this hypothesis the basis of more detailed speculation.
It is not clear, either from Hering’s paper[121] or from Semon’s book,[122] what is really to be understood here by the word “memory,” and, of course, there might be understood by it very different things, according to the author’s psychological point of view. If he is a “parallelist” with regard to so-called psychical phenomena, he would use the word memory only as a sort of collective term to signify a resultant effect of many single mechanical events, as far as the material world of his parallel system comes into account, with which of course the problem of inheritance alone deals; but if he maintains the theory of so-called psycho-physical interaction, the psychical would be to him a primary factor in nature, and so also would memory. As we have said, it is by no means clear in what sense the word “memory” is used by our authors, and therefore the most important point about the matter in question must remain in dubio.
But another topic is even more clear in the theory of inheritance, as stated in Hering’s and Semon’s writings. The hypothetical fact that so-called “acquired characters” are inherited is undoubtedly the chief assumption of that theory. Indeed, it would be difficult to understand the advantage of the ambiguous word memory, had it not to call attention to the hypothetic fact that the organism possesses the faculty of “remembering” what once has happened to it or what it once has “done,” so to speak, and profiting by this remembering in the next generation. The zoologist Pauly indeed has stated this view of the matter in very distinct and clear terms.
As we soon shall have another occasion to deal with the much-discussed problem of the “inheritance of acquired characters,” we at present need only say a few words about the “memory-theory” as a supposed “explanation” of heredity. Undoubtedly this theory postulates, either avowedly or by half-unconscious implication, that all the single processes in individual morphogenesis are the outcome either of adaptations of the morphological type, which happened to be necessary in some former generation, or of so-called contingent “variations,” of some sort or other, which also happened once in the ancestral line. Such a postulate, of course, is identical with what is generally called the theory of descent in any of its different forms. This theory is to occupy us in the next lectures; at present we only analyse the “memory-theory” as a theory of heredity in itself. In any case, to regard memory as the leading point in inheritance, at least if it is to signify what is called memory in any system of psychology, would be to postulate that either adaptation or contingent “variation” has been the origin of every morphogenetic process. Indeed, the American physiologist Jennings did not hesitate to defend such a view most strongly, and many others seem to be inclined to do the same.
But such an assumption most certainly cannot be true.
It cannot be true, because there are many phenomena in morphogenesis, notably all the phenomena akin to restitution of form, which occur in absolute perfection even the very first time they happen. These processes, for the simple reason of their primary perfection, cannot be due either to “learning” from a single adaptation, or to accidental variation. We shall afterwards employ a similar kind of argument to refute certain theories of evolution. It therefore may be of a certain logical interest to notice that at present, combating the memory-theory of inheritance, and hereafter, combating certain theories of descent, we select not “adaptation” or “variation” as the central points to be refuted, but the assumed contingency of both of them.
The word “memory,” therefore, may be applied to the phenomena of inheritance only in a very figurative meaning, if at all. We do not wholly deny the possibility of an inheritance of acquired characters, as will be seen later on, and to such a fact there might perhaps be applied such a term as “memory” in its real sense, but we simply know that there is something in inheritance which has no similarity whatever to what is called “memory” in any species of psychology. A primary perfection of processes occurring quite abnormally proves that there is a “knowing” of something—if we may say so—but does not prove at all that there is a “remembering.”
The Complex-Equipotential System and its Rôle in Inheritance[123]