Weismann s theory of Evolution (1891). 97 



However, it is but of little consequence whether or 

 not this is the meaning which Weismann intends to 

 convey. For the point we are coming to is. that, 

 whatever he intends to convey, " from the point of 

 view " of the theory of germ-plasm, there is only one 

 interpretation possible. It is not open to Weismann 

 (as it was to Darwin, or even to Galton,) to entertain 

 both the explanations, whether separately or in con- 

 junction. For germ-plasm (unlike gemmules, or even 

 stirp) must be held always and everywhere unalterably 

 stable : else the whole superstructure of Weismann's 

 theory of evolution falls to the ground. We cannot 

 consent to his retaining this theory on the one hand, 

 and, on the other, explaining bud-variation by "germ- 

 plasm of the first ontogenetic stage" becoming 

 altered " chiefly by changed conditions of develop- 

 ment." Even if it were true that " the alteration 

 must be very slight, if not quite insignificant," there 

 would here be a rift in the lute, which must finally 

 stop any further harping on the subject of Evolution. 



From the point of view of this theory, then, there 

 is only one interpretation open, — viz., that a bud- 

 variation is ultimately due to a peculiar admixture 

 of germ-plasms in the seed from which the bud was 

 ultimately derived. But the objections to entertaining 

 this as even a logically possible explanation of the 

 phenomena in all cases, is insuperable. 



In the first place, such a variation, when it does 

 arise, is usually a variation of an extremely pronounced 

 character ; therefore it is very far from supporting 

 Weismann's view, that the " alteration " of germ-plasm 

 which is needed to produce it " must be very slight, 

 and perhaps quite insignificant." In most cases where 



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