82 EVOLUTION OF TO-DA F. 



understand how these organs could have become so 

 much aborted by simple disuse ; or even more, to see 

 how they could have disappeared completely. Dar- 

 win has recognized the difficulty. " After an organ 

 has ceased being used, and has become in conse- 

 quence much reduced, how can it be still further re- 

 duced in size until the merest vestige is left ; and 

 how can it be finally quite obliterated ? It is 

 scarcely possible that disuse can go on producing 

 any further effect after the organ has once been 

 rendered functionless. Some additional explanation 

 is here requisite, which I cannot give." From this 

 passage it is evident that the theory of descent, at 

 least as understood by Darwin, has still something 

 to explain at this point. 



It must be noticed, however, that the difficulties 

 here mentioned are not necessarily difficulties for 

 evolution, but only for certain theories of evolution. 

 Pure Darwinism meets serious obstacles at these 

 points. The trouble is simply in our understanding 

 of. the manner in which organs could have become 

 rudimentary ; and although we may not yet compre- 

 hend this, the presence of rudimentary aborted 

 organs is just as significant an argument for descent 

 as it would be did these difficulties of method not 

 exist. 



Nascent Organs. 



The second class of rudimentary organs are those 

 which Agassiz has been pleased to call prophetic 

 organs, and which evolution would call nascent 

 organs. They are organs which, very simple in low 



