1 88 DARWINISM TO-DAY. 



general reading. As directly continuing the last chapter we 

 may consider first those theories put forward, chiefly by 

 Darwinians, as auxiliaries or supports of the selection 

 theory. Then we may briefly take up those theories that 

 have been advanced, mostly in recent years, as more or less 

 nearly completely prepared to replace Darwinism as a suffi- 

 cient scientific causo-mechanical explanation of species- 

 forming and descent. 



The Weismannian Theories of Panmixia and Germinal 

 Selection.' Weismann has for years been the most con- 

 spicuous of the neo-Darwinians. that is, of 



Weismann's im- 

 portant contrilm- those who would free Darwinism from all taint 



tions to biology. of Lamarckism it should always be remem- 

 bered that Darwin was inclined to attribute some degree of 

 influence in species-forming to the Lamarckian factor of 

 the inheritance of individually acquired adaptive charac- 

 ters and to make selection the all-sufficient and, indeed, 

 sole factor in species-forming. His great services to biology 

 in general and to the clearer understanding of the problems 

 of heredity and descent in particular, are unquestioned and 

 unquestionable. His careful investigation and illumination 

 of the vexed question of the inheritance of acquired charac- 

 ters, his definitive exposition of that point of view which 

 distinguishes sharply in the individual between the germ- 

 plasm (that particular protoplasm in the body from which 

 the germ-cells, eventually new individuals, arise) and the 

 soma-plasm (that which develops into, or gives rise to, the 

 rest of the body), his development of the interesting and 

 suggestive combinations of fact and theory designated by 

 the phrase names "continuity of the germ-plasm" and "im- 

 mortality of the Infusoria," these products of his investi- 

 gating and philosophising mind prove him one of the ablest 

 of modern biological scholars. They also make him the 

 principal present-day champion of the selection theory. For 

 all these expositions of fact and theory are of a nature to- 



