SPECIES AND THEIR ORIGIN 321 



The same dangers beset the path of the unwary 

 who argue from the Lamarckian standpoint. The 

 need for a useful organ is evident, but we are by no 

 means justified in assuming that the " need " 

 brought about the existence of the organ. Even 

 man cannot " by taking thought, add one cubit to [ 

 his stature." The Lamarckian argument rests upon 

 the transmission, in heredity, of the results of environ- 

 mental influences upon the soma ; in other words, the 

 "inheritance of acquired characters." On a priori 

 grounds, Weismann sought to show that this was 

 impossible, since the germ-plasm gives rise to the 

 soma and is unaffected by its accidents. Moreover, , 

 the greatest variety of experiment has been attempted 

 for many years, in an effort to secure the hereditary 

 transmission of any sort of such acquired characters, 

 with universally negative results. 1 One of the 

 most elaborate of these was carried out by a Ger- 

 man botanist who transplanted some 2500 different 

 kinds of mountain plants to the lowlands and 

 studied them for several years in comparison with 

 their lowland relatives. He found that the alpine 

 environment had made no permanent change in 

 their habit or structure. 



It is not even necessary to assume such a dis- 

 tinction as that between germ-plasm and soma- 

 plasm, a distinction that is sometimes difficult to 

 maintain, in order to appreciate the improbability 

 of the inheritance of environmental effects. Ani- 

 mals and plants are complexes of matter whose 



1 With one very doubtful exception. 

 Y 



