& 



12 THE GKRM-PIASM 



ph3-siological units — but rather bodies of a highly complex 

 constitution, each containing all the primary constituents which 

 are necessary to the formation of an organism. Each ancestral 

 germ-plasm seemed to me to be of a ' special kind." and just as 

 many ' different kinds of idioplasm ' are removed by the reducing 

 division • from the ovum as are afterwards introduced by the 

 sperm-nucleus' on fertilisation. It will be seen that 1 retain this 

 essential basis of the theory of the germ-plasm in its further 

 development as presented here, and I trust that I may now suc- 

 ceed in refuting the objections which have been urged against 

 the ' ancestral germ-plasms." or, as I now call them, the 'ids' 

 In any case it cannot be denied that they help to throw an 

 important light on the subject. 



De Vries has so far been my most powerful opponent as re- 

 gards the ancestral germ-plasms, but his opposition is founded 

 on the misunderstanding 1 have already referred to. for he looks 

 upon them as the ultimate vital particles — an idea which was 

 foreign to me from the beginning. Of this, however, I do not 

 complain, as at that time I had left the question as to the 

 construction of the ancestral germ-plasms unanswered.* This 

 omission is supplied in the present book, and it will be shown 

 that, although each ancestral germ-plasm is in my opinion a 

 bearer of all the primary constituents required for the construc- 

 tion of an organism, my assumption does not exclude the possi- 

 bilitv of its being composed of these constituents in the form of 

 minute vital particles. The 'ancestral germ-plasm' is indeed a 

 unit, but one of a higher order. For this reason alone it can- 

 not be compared with Spencer's ' physiological units,' because 

 the latter, as ultimate vital particles, compose the whole body ; 

 while the ancestral germ-plasms only form the nuclear matter, 

 and merely serve the mechanical purpose of the processes of 

 heredity. 



De Vries has in a significant manner developed a theory of 



* De Vries is also mistaken in ascribing to me the opinion that ' there is 

 only one hereditary substance — only one material bearer of the hereditary 

 tendencies in each individual.' The sentence quoted by him (' On the 

 Number of Polar Bodies,' p. 355) does not deal with this question ; it runs 

 as follows : — From several reasons already stated ' at least one certain 

 result follows, viz., that there is an hereditary substance, a material bearer 

 of hereditary tendencies, and that this substance is contained in the nucleus, 

 of the germ-cell,' &c. 



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