Weismanri s theory of Evolution (1891). 99 



impossible to suppose that in millions and millions of 

 sister-buds, which through years and years exhibit no 

 variation, a highly peculiar admixture of germ-plasm 

 (which was originally present in the parent-seed) 

 should have" been latent ; that it should then suddenly 

 become so patent in a single bud, after which it never 

 occurs in any other bud, save in the progeny of the 

 sporting one. 



On the whole, then, while it thus seems impossible 

 to attribute all cases of bud-variation to mixtures of 

 germ-plasms in sexual propagation, the theory of 

 germ-plasm is unable to entertain any other explana- 

 tion, on pain of surrendering its postulate touching 

 the unalterable stability of germ-plasm, on which the 

 Weismannian theory of evolution is founded. 



So much for Weismann's evidence touching the 

 extreme, or virtually everlasting, stability of germ- 

 plasm. We have seen that this evidence is not merely 

 of a very poor character per se, or on antecedent 

 grounds ; but that it is directly negatived as evidence 

 by the a-sexual origin of species in the plants alluded 

 to by Professor Vines ; by certain facts which prove so 

 high a degree of instability on the part of this hypo- 

 thetical substance, that in some cases it admits of 

 being very considerably modified in the course of 

 only two or three generations by exposure to changed 

 conditions of life ; while in other cases it may " sport," 

 so as to produce {; hereditary individual variations," 

 which are much more pronounced than any of those 

 that ordinarily result from a blending of hereditary 

 qualities in an act of sexual union. 



It will be well to conclude our examination of 



H 2 



