272 THE WORLD OF LIFE 



amply suffice, yet there are conceivable cases in wbich they 

 might be insufficient, and these cases are now explained by 

 a very interesting combination of the effects of acquired 

 modifications of the individual with the selection of congenital 

 variations. The third is, I think, somewhat more important, 

 as indicating a real deficiency in the theory, as originally 

 stated, but which is now well supplied by an extension of 

 that theory from the body itself to the reproductive germs 

 from which its parts are developed. I will, therefore, en- 

 deavour to explain in as simple a manner as possible how 

 these three objections have been overcome. 



(1) The Beginnings of Organs 



The objection that the first slight beginnings of new organs 

 would be useless, and that they could not be preserved and 

 increased by natural selection, was one of the most frequent 

 in the early stages of the discussion of the theory, and was 

 answered by Darwin himself in the later editions of his book. 

 But the objection still continues to be made, and owing to 

 the great mass of controversial literature continually issued 

 from the press many of the objectors do not see the replies 

 made to them ; there is therefore still room for a somewhat 

 more general answer, wdiich will apply not only to certain 

 individual cases, but to all. The most general and therefore 

 the best answ^er I have yet seen given is that of Professor 

 E. B. Poulton in his recently published Essays on Evolution. 

 He says: 



" Organs are rarely formed anew in an animal, but they are 

 formed by the modification of pre-existing organs ; so that, instead 

 of having one beginning for each organ, we have to push the be- 

 ginning further and further back, and find that a single origin ac- 

 counts for several successive organs, or at any rate several functions, 

 instead of one." 



He then goes on to show that the four limbs of vertebrates 

 have been again and again modified, for running, for climbing 



to? 



