Chat. Yl.J DIFFICULTIES OF THE THEORY. 207 



CHAPTEE 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 Labits in the same species — Species with habits 

 widely different from those of their allies — Organs of extreme 

 perfection — 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 Conditions" of Existence embraced by the theory of Natural 

 Selection. 



Loxg before the reader has arrived at this part of my 

 work, a crowd 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 

 staggered ; but, to the best of my judgment, the 

 greater number are only apparent, and those that are 

 real are not, I think, fatal to the theory. 



These difficulties and objections may be classed under 

 the following heads :— First, why, if species have 

 descended from other species by fine gradations, do we 

 not everywhere see innumerable transitional forms ? 

 Why is not all nature in confusion, instead of the species 

 being, as we see them, well defined ? 



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 



