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26A THE ORIGIN OF SPECIES 



lieve that natural selection could produce, on the one 

 hand, an organ of trifling importance, such as the tail of 

 a girafie, which serves as a fly-flapper, and, on the other 

 hand, an organ so wonderful as the eye ? 



Thirdly, can instincts be acquired and modified 

 through natural selection? What shall we say to tlie 

 instinct which leads the bee to make cells, and which 

 has practically anticipated the discoveries of profound 

 mathematicians ? 



Fourthly, how can we account for species, when 

 crossed, being sterile and producing sterile offspring, 

 whereas, when varieties are crossed, their fertility is 

 unimpaired ? 



The first two heads will here be discussed; some mis- 

 cellaneous objections in the following chapter; Instinct 

 and Hybridism in the two succeeding chapters. 



On the Absence or Rarity of Transitional Varieties 



As natural selection acts solely by the preservation of 

 proStable modifications, each new form will tend in a 

 fuUv-stocked country to take the place of, and finally to 

 exterminate, its own 1 ess ..iiU-P roved parent-form and other 

 Jess-iatored forms with which it comes into competition. 

 Thus exti nctio n and natural jSelection_go hand in hand. 

 Ht^nce, if we look at each species as descended from some 

 unknown form, both the parent and all the transitional 

 varieties will generally have been exterminated by the 

 verv process of the formation and perfection of the new 

 form. 



Bat, as by this theory innumerable transitional forms' 

 must have existed, why do we not find them imbedded 

 in countless numbers in the crust of the earth ? It will 



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