298 Darwin, and after Darwin. 



sustains their standard structure' — i.e. solely by the cessation 

 of selection. Obviously, there is here a flat contradiction. If 

 Professor Weismann now believes that a rudimentary organ 

 'must finally disappear solely' through the withdrawal of 

 selection, he has abandoned his previous belief that 'the 

 complete disappearance of a rudimentary organ can only take 

 place by the operation of selection. ' And this change of belief 

 on his part is a matter of the highest importance to his system 

 of theories as a whole, since it betokens a surrender of his 

 doctrine of the 'stability' of germ-plasm— or of the virtually 

 everlasting persistence of the force of heredity, and the 

 consequent necessity for a reversal of this force itself (by natural 

 selection placing its premium on minus instead of on plus 

 variations), in order that a rudimentary organ should finally 

 disappear. In other words, it now seems he no longer believes 

 that the force of heredity in one direction (that of sustaining 

 a rudimentary organ) can only be abolished by the active influence 

 of natural selection determining this force in the opposite 

 direction (that of removing a rudimentary organ). It seems he 

 now believes that the force of heredity, if merely left to itself 

 by the withdrawal of natural selection altogether, will sooner or 

 later become exhausted through the mere lapse of time. This, 

 of course, is my own theory of the matter as originally published 

 in these columns ; but I do not see how it is to be reconciled 

 with Professor Weismann's doctrine of so high a degree of 

 stability on the part of germ-plasm, that we must look to the 

 Protozoa and the Protophyta for the original source of congenital 

 variations as now exhibited by the Metazoa and Metaphyta. 

 Nevertheless, and so far as the philosophy of degeneration is 

 concerned, I shall be very glad if (as it now appears) Professor 

 Weismann's more recent contemplation has brought his principle 

 of panmixia into exact coincidence with that of my cessation 

 of selection." 



Before passing on it may here be noted that, to any one 

 who believes in the inheritance of acquired characters, there 

 is open yet another hypothetical cause of degeneration, and 

 one to which the final disappearance of vestigial organs may 

 be ailiibuLcd. Roux has shown in his work on The Struggle 



