222 MISCELLANEOUS OBJECTIONS TO THE 



nearly but not quite the same purpose, became attached tc 

 the free ends of the caudicles — all these gradations being 

 of manifest benefit to the plants in question. With respect 

 to climbing plants, I need not repeat what has been so lately 

 said. 



It has often been asked, if natural selection be so potent, 

 why has not this or that structure been gained by certain 

 species, to which it would apparently have been advanta- 

 geous ? But it is unreasonable to expect a precise answer 

 to such questions, considering our ignorance of the past 

 history of each species, and of the conditions which at the 

 present day determine its numbers and range. In most 

 cases only general reasons, but in some few cases special 

 reasons, can be assigned. Thus, to adapt a species to new 

 habits of life, many co-ordinated modifications are almost 

 indispensable, and it may often have happened that the 

 requisite parts did not vary in the right manner or to the 

 right degree. Many species must have been prevented from 

 increasing in numbers through destructive agencies, which 

 stood in no relation to certain structures, which we imagine 

 would have been gained through natural selection from 

 appearing to us advantageous to the species. In this case, 

 as the struggle for life did not depend on such structures, 

 they could not have been acquired through natural selection. 

 In many cases complex and long-enduring conditions, often 

 of a peculiar nature, are necessary for the development of a 

 structure ; and the requisite conditions may seldom have 

 concurred. The belief that any given structure, which we 

 think, often erroneously, would have been beneficial to a 

 species, would have been gained under all circumstances 

 through natural selection, is opposed to what we can under- 

 stand of its manner of action. Mr. Mivart does not deny 

 that natural selection has effected something ; but he consid- 

 ers it as " demonstrably insufficient " to account for the phe- 

 nomena which I explain by its agency. His chief arguments 

 have now been considered, and the others will hereafter be 

 considered. They seem to me to partake little of the char- 

 acter of demonstration, and to havt little weight in compariv 

 ■on with those in favor of the power of natural selection, 

 aided by the other agencies often specified. I am bound to 

 add, that some of the facts and arguments here used by me, 

 have been advanced for the same purpose in an able article 

 lately published in the " Medico-Chirurgical Review." 



At the present day almost all naturalists admit ^olutioii 



