DIFFICULTIES of the THEORY. 149 



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 

 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. 



Long 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 believe that natural selection 

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

 tance, such as the tail of a giraffe, 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 

 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, 



