Summary. 113 



into ever more and more intricate as well as more and 

 more diverse relations with the external world ; — all 

 this is, I repeat, well nigh incredible. At any rate, 

 speaking for myself, I should require some enormous 

 weight of evidence to balance so enormous an ante- 

 cedent improbability, or before I could regard such 

 a doctrine as meriting any serious attention. 



What, then, is the evidence that has been adduced ? 

 We have found that this evidence is nil. On the 

 other hand, we have found that the evidence against 

 the doctrine is abundantly sufficient to annihilate the 

 doctrine — and this quite apart from all the antecedent 

 considerations just alluded to. For not only have we 

 the sundry facts of bud-variation, a-sexual origin of 

 species, &c, which contradict the doctrine ; but we 

 have also the results of direct experiment, which 

 prove that the alleged stability of germ-plasm may be 

 conspicuously upset by slight changes in the external 

 conditions of life. So that both from within and from 

 without the stability which is alleged in theory admits 

 of being overturned by facts. 



And here, in order to avoid all possible confusion, 

 I must ask it once more to be noted that there is not, 

 and never has been, any question touching the high 

 degree of stability which is exhibited by whatever 

 substance it is that constitutes the material basis of 

 heredity. But this is a widely different thing from 

 supposing the stability absolute, so that it can never 

 have been affected in any degree since the first origin 

 of multicellular organisms, or in any of the millions of 

 species into which these organisms have ramified. 

 And the fact that in some cases we are actually 

 able to observe a change of congenital characters as 



I 



