243 THE EVOLUTION THEORY 



was only too glad to have any sort of principle of interpretation 

 ready to work with. But Charles Darwin, too, attributed a not 

 inconsiderable influence to this principle, although the transmission of 

 'acquired' characters which it took for granted was not accepted 

 without reflective hesitation. He even directed his own particular 

 theory of heredity, as we shall see, especially to the explanation 

 of this supposed form of inheritance, and we can very well under- 

 stand this, after what I have said as to the impossibility of explain- 

 ing the disappearance of organs which have become superfluous by 

 the Darwin- Wallace theory of Natural Selection. Darwin needed 

 the Lamarckian principle for the explanation of these phenomena, and 

 it was this that decided him to assume the transmission of ' acquired ' 

 characters, although the proofs of it can hardly have satisfied him. 

 For when we are confronted with facts which we see no possibility of 

 understanding save on a single hypothesis, even though it be an 

 undemonstrable one, we are naturally led to accept the hypothesis, at 

 least until a better one can be found. It is in this way, obviously, 

 that we are to understand Darwin's attitude to the Lamarckian 

 principle ; he did not reject it, because it seemed to him to ofl'er the 

 only possible explanation of the disappearance of characters which 

 have become useless ; he adhered to it, although the transmission of 

 acquired characters which it assumed must have seemed, and, in point 

 of fact, did seem to him doubtful, or at least not definitely proved. 

 Doubts, some faint, some stronger, as to this assumed form of 

 inheritance were hardly expressed till somewhat late in the day — 

 almost twenty years after the appearance of the Origin of Species 

 — first by Francis Galton (1875), then by His, who definitely declared 

 himself at least against any inheritance of mutilations, and by 

 Du Bois-Reymond, who, in his address Ueber die Uebung in 1881, 

 said : ' If we are to be honest, we must admit that the inheritance of 

 acquired characters is a hypothesis inferred solely from the facts 

 which have to be explained, and that it is in itself quite obscure.' 



This is how it must appear to every one who examines it simply 

 in respect of its theoretical possibility, its conceivability. This is how 

 it appeared to me when I attempted, in 1883, to arrive at clearness 

 on the subject, and I then expressed my conviction that such a 

 form of inheritance was not only unproved, but that it was even 

 theoretically unthinkable, and that we ought to try to explain the 

 fact of the disappearance of disused parts in some other way, and 

 I attempted to give an explanation, as will be seen later. 



Thus war was declared against the Lamarckian principle of 

 the direct effect of use and disuse, and there arose a strife which 



