156 MISCELLANEOUS OBJECTIONS TO THE [CHAP. VII. 



rendered higher. Natural selection will not necessarily lead to 

 absolute perfection ; nor, as far as we can judge by our limited 

 faculties, can absolute perfection be everywhere predicated. 



On the theory of natural selection we can clearly understand 

 the full meaning of that old canon in natural history, " Xatura 

 non facit saltum." This canon, if we look to the present inhabi- 

 tants alone of the world, is not strictly correct ; but if we include 

 all those of past times, whether known or unknown, it must on 

 this theory be strictly true. 



It is generally acknowledged that all organic beings have been 

 formed on two great laws Unity of Type, and the Conditions of 

 Existence. By unity of type is meant that fundamental agree- 

 ment in structure which we see in organic beings of the same 

 class, and which is quite independent of their habits of life. On 

 my theory, unity of type is explained by unity of descent. The 

 expression of conditions of existence, so often insisted on by the 

 illustrious Cuvier, is fully embraced by the principle of natural 

 selection. For natural selection acts by either now adapting the 

 varying parts of each being to its organic and inorganic conditions 

 of life ; or by having adapted them during past periods of time : 

 the adaptations being aided in many cases by the increased use or 

 disuse of parts, being affected by the direct action of the external 

 conditions of life, and subjected in all cases to the several laws of 

 growth and variation. Hence, in fact, the law of the Conditions 

 of Existence is the higher law ; as it includes, through the inheri- 

 tance of former variations and adaptations, that of Unity of Type. 



CHAPTER VII. 



MISCELLANEOUS OBJECTIONS TO THE THEORY OF NATURAL 

 SELECTION. 



Longevity Modifications not necessarily simultaneous Modifications appa- 

 rently of no direct service Progressive development Characters of small 

 functional importance, the most constant Supposed incompetence of 

 natural selection to account for the incipient stages of useful structures 

 Causes which interfere with the acquisition through natural selection of 

 useful structures Gradations of structure with changed functions Widely 

 different organs in members of the same class, developed from one and the 

 same source Reasons for disbelieving in great and abrupt modifications. 



I WILL devote this chapter to the consideration of various miscel- 

 laneous objections which have been advanced against my views, 

 as some of the previous discussions may thus be made clearer ; but 

 it would be useless to discuss all of them, as many have been 



