240 TRANSMISSION OF ACQUIRED CHARACTERS 



operate in an approximately similar way for many generations, 

 they will produce definite and slowly cumulative effects upon 

 the organisms subjected to them. He is by no means com- 

 mitted to the belief that every change of conditions will produce 

 appreciable hereditary effects in a few generations. The point 

 is not whether modifications are fully and completely transmitted, 

 but whether any trace of them may be transmitted. Still less 

 is the Neo-Lamarckian bound to admit that any given change of 

 conditions, more or less arbitrarily selected by any one as being 

 convenient for experimental purposes, will produce recognisable 

 results in the following generation. Thus the fact that most of 

 the experimental results are inconclusive or negative does not 

 disprove the Lamarckian belief. 



Interpretation.— As to the second method, that of the in- 

 terpretation of facts, it cannot be very conclusive either, since 

 both sides have to prove a negative in order to establish their 

 case. The Neo-Lamarckians have to show that- the phenomena 

 they adduce as illustrations of modification-inheritance cannot 

 be interpreted as the results of selection operating on germinal 

 variations. In order to do this to the satisfaction of the other 

 side, the Neo-Lamarckians must prove that the characters in 

 question are outside the scope of natural selection, that they are 

 non-utilitarian and not correlated with any useful characters — 

 a manifestly difficult task. The Neo-Darwinians, on the other 

 hand, have to prove that the phenomena in question cannot be 

 the results of modification-inheritance. And this is in most 

 cases impossible. Thus we seem to reach a logical dead-lock. 



Cases where the Theory of Modification -Inheritance is inap- 

 plicable. — It is true, however, that there are certain characters 

 of certain organisms, in regard to which it may be said with some 

 security that they could not have arisen by the inheritance 

 of acquired characters. Thus many insects and the like have 

 adaptive characters in their cuticular structures — knobs suited 

 for crushing, saws suited for cutting, gimlets suited for boring. 



