CHAPTER VI 

 Difficulties of the Theory 



Difficulties of the theory of descent with modification — Absence or 

 rarity of transitional varieties — Transitions in habits of life — 

 Diversified habits in the same species — Species with habits widely 

 different from those of their allies — Organs of extreme perfec- 

 tion — Modes of transition — Cases of difficulty — Natura non facit 

 saltum — Organs of small importance — Organs not in all cases 

 absolutely perfect — The law of Unity of Type and of the Con- 

 ditions of Existence embraced by the theory of Natural 

 Selection. 



LONG before the reader has arrived at this part of my 

 work, a crow^d of difficulties will have occurred to him. 

 Some of them are so serious that to this day I can 

 hardly reflect on them without being in some degree stag- 

 gered; but, to the best of my judgment, the greater number 

 are only apparent, and those that are real are not, I think, 

 fatal to theory. 

 r These difficulties and objections may be classed under the 

 \ following heads; — First, why, if species have descended from 

 V" other species by fine gradations, do we not everywhere see 

 's innumerable transitional forms? Why is not all nature in 

 }$■ confusion, instead of the species being, as we see them, well 

 I defined? 



L- Secondly, is it possible that an animal having, for instance, 

 the structure and habits of a bat, could have been formed by 

 the modification of some other animal with widely different 

 habits and structure? Can we believe that natural selection 

 could produce, on the one hand, an organ of trifling impor- 

 tance, such as the tail of a girafife, 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 the instinct which 



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