1890 LETTER ON WEISMANN'S THEOEY 253 



To Professor Poulton. 



18 Cornwall Terrace, Eegent's Park, N.W. : January 27, 1890. 



My dear Poulton, — Many thanks for your letter, 

 with its very clear and cogent reasoning. But I am 

 not sure that the latter does not hit Weismann 

 harder than it hits me. For the cases you have in 

 view are those where very recently acquired charac- 

 ters are concerned; and where, therefore, according 

 to my views, ' the force of heredity ' is weak and thus 

 quickly ' worn out.' In such cases (as I say in the 

 last passages of enclosed, which I return for you to 

 hand me on Friday) ' cessation will (quicMy) ensure 

 the reduction of an unused organ below fifty per cent, 

 of its original size, and so on down to zero ; but this 

 it does because it is now assisted by another and co- 

 operating principle — viz. the eventual failure of 

 heredity.' 



Now it is just this co-operating principle that 

 Weismann is debarred from recognising by his dogma 

 about ' stability of germ-plasm.' And it is a principle 

 that must act the more energetically (i.e. ' quickly ') 

 the shorter the time since the now degenerating organ 

 was originally acquired. In the 'Nature' articles I 

 was speaking of ' rudimentary organs ' which in 

 Darwin's sense are very old heirlooms. All this to 

 make you reconsider whether there is any disagree- 

 ment between us upon this point. 



It is, indeed, a terrible thing about Aubrey Moore, 

 and also a loss to Darwinism on its popular side. 



Q. J. E. 



