110 THE EVOLUTION THEORY 



existence, expands, and increases to a new being whose individual 

 parts are still itself and flesh of its flesh, it reproduces what it 

 experienced as part of a great whole. This is just as wonderful as 

 when an old man suddenly remembers his earliest childhood, but it 

 is not more wonderful than this.' 



But I think it is more wonderful. There exist demonstrably in 

 the brain thousands upon thousands of nerve-elements, whose activity 

 is a definite and limited one, because each particular visual impression, 

 for instance, only excites to activity certain definite nerve-elements, 

 and can leave memory-pictures in these alone. According to m}^ con- 

 ception of it, the germ-plasm is quite as complex in its composition, 

 and does not consist of homogeneous elements, but of innumerable 

 different kinds, which are not related to the parts of the complete 

 organism indiscriminately, but only to particular parts. But is it 

 allowable to assume that there are invisible nerve-connexions, 

 not only to every germ -cell, but also within the germ-plasm, to 

 every determinant, like the nerve-paths which lead from the eye 

 to the nerve-cells in the optic-area of the brain? For if it 

 were otherwise, how could we conceive of the modification of an 

 organ — as, for instance, the ear-muscles in Man — communicating 

 itself to the precise determinants of these muscles in the germ- 

 plasm ? I have often been met with the reproach that my conception 

 of the composition of the germ-plasm is much too complex — but the 

 complexity of Hering's suggestion seems to me to go a long way 

 beyond mine. 



Hering's ideas, which are not only ingenious but very stimu- 

 lating, might be accepted as the first indication of an understanding 

 of the assumed inheritance of functional modifications, if it could be 

 proved that such inheritance is a fact ; but, as we have seen, that is 

 not the case. The assumption might be permitted, perhaps, if it 

 could be shown that certain groups of phenomena left no other pos- 

 sibility of explanation open except this assumption, but that also, as far 

 as I can see, is not the case. Of course, others hold a different opinion, 

 but chiefly because they have rejected without much reflection the 

 sole explanation which presents itself for numerous phenomena — I 

 mean the processes which we are about to study under the name of 

 ' germinal selection.' But, in any case, Hering's ideas seem to me very 

 valuable, because they make it apparent that, however much we know 

 of the organism, we only know it in a general way, and that numberless 

 delicate processes go on in it which leave no trace for our microscope, 

 and that we can only recognize the final results of numerous invisible 

 and often, in their subtlety, also unimaginable factoivs. This ought to 



