Chap. VI. DIFFICULTIES OF THE TIIEOKY 1(J7 



CHAPTER YI. 



DIFFICULTIES OF THE TIIEOKY. 



Difflcnilies of the Theory of Descent with Modification— Transitions— Ahsence or 

 Karlty of Transitional Varieties— Transitions in Habits of Life— Diversified Hab- 

 its iu the same Specios— Species with Habits widely different from those of their 

 Allies — Orj^iiis of Extreme Perfection— Modes of Tranh-ition— Cases of Ditflcully 

 — Natura nou fucit saltnm— Ort'ans of small Importance— Organs not in all Cases 

 absolutely perfect- The Law of XJniiy of Type aud of the Conditions of Existence 

 embraced by the Theory of Natural Selection. 



Loxr, before havins; anivcd at this part of my ^-ork, a 

 crowd of dilFiculties will have occurred to the reader. Some 

 of them are so serious that to this day I can hardly reflect on 

 them without bein<i; stapffrered ; but, to the best of my judf^- 

 ment, the prreater number arc only «pparcnt, and those that are 

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



These dilliculties and objections may be classed under the 

 followiuf^ heads : First, Avhy, if species have descended from 

 other species by insensibly line p;radations, do Ave not every- 

 where see ir.numcrable transitional fonns? 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 liavino", for instance, 

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

 the modification of some animal Avith Avidely-difl'erent structine 

 and habits ? Can Ave believe that natural selection could pro- 

 duce, on the one hand, organs of trifling importance, such as 

 the tail of a giraffe, Avhich serA'cs as a tly-fiapper, and, on the 

 other hand, organs of sucli wonderful structure, as the eye, of 

 Avhich we hardly as yet fiillv imderstand the inimitable perfec- 

 tion ? 



Thirdly, can instincts be acquired and modified through 

 natural selection ? What shall Ave say to so marvellous an 

 instinct as that Avhich leads the bee to make cells, Avhich has 

 jiracticall}^ anticipated i\m discoveries of profound mathema- 

 ticians ? 



