92 An Examination of Weismannism. 



such that it may endure, not merely for such a com- 

 parative!}* small number of generations as these facts 

 imply, but actually for any number of generations, 

 or through the practically infinite series of generations 

 that now intervene between the higher metazoa and 

 their primeval parentage in the protozoa. Clearly, 

 the ratio between these two things is such that no 

 argument derived from the facts of atavism can be 

 of any avail for the purposes of this Weismannian 

 doctrine. 



Lastly, as regards vestigial organs, the consideration 

 that, surprisingly persistent as they unquestionably are, 

 nevertheless they do eventually disappear, seems to 

 prove that the power of heredity does in time become 

 exhausted, even in cases most favourable to its con- 

 tinuance. That it should thus become finally ex- 

 hausted is no more than Darwin's theory of perishable 

 gemmules. or Galton's theory of a not absolutely 

 stable stirp, would expect. But the fact is irre- 

 concilable with Weismann's theory of an absolutely 

 stable germ-plasm. 



Hence, we can only conclude that there is no 

 evidence in favour of the hypothesis that germ-plasm 

 has been unalterably stable "since the first origin 

 of sexual propagation"; while the suggestion that 

 it may have been so is on antecedent grounds im- 

 probable, and on inductive grounds untenable. It 

 only remains to add that the degree of stability 

 has been proved in not a few cases to be less than 

 even the theory of gemmules might anticipate. Many 

 facts in proof of this statement might be given, but it 

 will here suffice to quote one, which I select because 

 it has been dealt with by Professor Weismann himself. 



