Appendix /. 297 



organ is due to reversed selection. And I cannot doubt that if 

 Professor Weismann had sufficiently considered the matter, he 

 would not have committed himself to the statement that ' the 

 complete disappearance of a rudimentary organ can only take 

 place by the operation of natural selection.' 



"According to my view, the complete disappearance of a rudi- 

 mentary organ can only take place by the cessation of natural 

 selection, which permits the eventual exhaustion of heredity, 

 when heredity is thus simply left to itself. During all the earlier 

 stages of reduction, the cessation of selection was assisted in its 

 work by the reversal of selection ; but when the rudiment 

 became too small for such assistance any longer to be supplied, 

 the rudiment persisted in that greatly reduced condition until 

 the force of heredity with regard to it was eventually worn 

 out. This appears to me, as it appeared in 1873, the only 

 reasonable conclusion that can be drawn from the facts. And 

 it is because this conclusion is fatal to Professor Weismann's 

 doctrine of the permanent 'stability' of germ-plasm, while 

 quite in accordance with all theories which belong to the family 

 of pangenesis, that I deem the facts of degeneration of great 

 importance as tests between these rival interpretations of the 

 facts of heredity. It is on this account that I have occupied so 

 much space with the foregoing discussion ; and I shall be glad 

 to ascertain whether any of the followers of Professor Weismann 

 are able to controvert these views. 



" GEORGE J. ROMANES." 



"P.S. Since the above article was sent in, Professor Weismann 

 has published in these columns (February 6) his reply to a criti- 

 cism by Professor Vines (October 24, 1889). In this reply 

 he appears to have considerably modified his views on the 

 theory of degeneration ; for while in his Essays he says (as in 

 the passage above quoted) that ' the complete disappearance of 

 a rudimentary organ can only take place by the operation 

 of natural selection' i.e. only by the reversal of selection, in 

 his reply to Professor Vines he says, ' I believe that I have 

 proved that organs no longer in use become rudimentary, and 

 must finally disappear, solely by "panmixia"; not through the 

 direct action of disuse, but because natural selection no longer 



