APPENDIX. 



IN Chapter II. we saw that many of the valuable and 

 carefully reasoned results which Weismann had ob- 

 tained are accompanied by much detailed specula- 

 tion based upon an extremely limited fact basis. In 

 his later writings especially, the reader who searches 

 for the facts and reasoning which refer to such ques- 

 tions as the non-transmission of acquired characters 

 will find everywhere an abundant commingling with 

 speculations concerning the mechanical process of 

 heredity. I have ventured in the appendix to sketch 

 shortly this speculation of Weismann's, and to give 

 my own estimation of its value. 



Weismann was not the first to speculate or found 

 a mechanical theory of heredity; Darwin himself pub- 

 lished a theory of " pangenesis," and this was, I 

 beHeve, the only piece of speculation of which Darwin 

 was ever guilty. That he might picture to himself, 

 by means of material particles, the views that he held 

 of heredity, Darwin supposed that during their life- 

 time every cell of the parent disengages small living 

 particles gemmules which find their way to and 

 are stored up in the generative cells, ready to develop 

 in the next generation into cells similar to those from 

 which they came. This theory was actually framed 

 to support those cases where Darwin supposed that 

 acquired characters are transmitted, for he says in 



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