Chap. VI.] DIFFICULTIES OF THE THEORY. 207 



CHAPTEE VI. 



DIFFICITLTIES OF THE THEOBY. 



Difficulties of the theory of descent with modiflcation— 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 Natu- 

 ral Selection. 



Long before the reader has arrived at this part of my 

 work, a crowd of difficulties will have ocdurred 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 spe- 

 cies 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 



