Weismann s theory of Evolution (189 [). 93 



Professor Hoffmann has published an abstract of 

 a research, which consisted in subjecting plants with 

 normal flowers to changed conditions of life through 

 a series of generations. In course of time, certain well- 

 marked variations appeared. Now, in some cases such 

 directly-produced variations were transmitted by seed 

 from the affected plants ; and therefore Weismann 

 acknowledges, — " I have no doubt that the results are, 

 at any rate in part, due to the operation of heredity." 

 Hence, whether these results be due to the trans- 

 mission of somatogenetic characters (" representative 

 changes"), or to the direct action of changed conditions 

 of life on the germ-plasm itself (" specialized changes"), 

 it is equally certain that the hereditary characters 

 of the plants were congenitally modified to a large 

 extent, within (at most) a few generations. In other 

 words, it is certain that, if there be such a material as 

 germ-plasm, it has been proved in this case to have 

 been highly unstable. Therefore, in dealing with 

 these and other similar facts, Weismann himself can 

 only save his postulate of continuity by surrendering 

 for the time being his postulate of stability \ 



If to this it be replied that Hoffmann's facts are 

 exceptional — that Gartner, Nageli, De Candolle, Peter,, 



1 What he says is: — "It was only after a greater or less number 

 of generations had elapsed that a variable proportion of double flowers 

 appeared, sometimes accompanied by changes in the leaves and in the 

 colours of the flowers. This fact admits of only one interpretation : — 

 the changed conditions at first produced slight and ineffectual changes 

 in the idio-plasm of the individual, which was transmitted to the following 



generation Now, the idio-plasm of the first ontogenetic graae 



(viz., germ-plasm) alone passes from one generation to another, and 

 hence it is clear that the germ-plas??i itself must have been gradtcally 

 changed by the conditions of life, until the alteration became sufficient to 

 produce changes in the soma, which appeared as visible characters in 

 either flower or leafy — Essays, pp. 426-7 ; italics mine. 



