41 8 THE POPULAR SCIENCE MONTHLY. 



become fixed. Finally, this principle extends into the field of psychol- 

 ogy and throws light even upon the origin of our ethical aspirations. 

 In short, in lieu of final causes we would have in organic nature a 

 most complex but blindly acting mechanism ; and the cosmic problem 

 would be reduced to the two enigmas : " What are matter and force ? " 

 and, "How can these think?" 



The objections to this doctrine of natural selection are esseritially 

 three in number : 



The first group of its opponents simply question the facts on which 

 the theory is based, namely, the tendency to variation, the transmissi- 

 bility of varieties, the fecundity of hybrids, the mutability of species ; 

 above all, Darwin's very ingenious explanation of the dying out of 

 intermediate forms. These opponents, however, urge but little be- 

 yond the arguments on which the doctrine of the old systematic school 

 rested, and which have been shown by Darwin to be untenable. Still, 

 there is one objection which possesses undoubted weight. I myself 

 early called attention to it in my lectures, in which I believe I was the 

 first public expositor of the new doctrine in Germany. The objection 

 was not printed till much later, so far as I know, and then by Prof. A. 

 W. Volkmann. It is this, that the minute variations in which new 

 species are supposed to have their rise can not be of any material ad- 

 vantage to the individual in which they appear. Still, in my opinion, 

 this objection applies only in certain cases, and perhaps only provision- 

 ally. In the case of electrical organs, for instance, it still seems to be 

 unanswerable, for we can not assign any possible use for the so-called 

 pseudo-electrical organs. But, as concerns wings, we see in the example 

 of the flying opossum, the flying lemur, and of the flying frog, dis- 

 covered by Wallace, how difficult it is to say of a rudimentary organ 

 whether it is or is not of advantage to an animal. In short, the ques- 

 tion is not whether this or that definite structure, but whether any 

 adapted structure whatever, can be explained in the way pointed out 

 bj^ Mr. Darwin. In many cases of adaptation by mimicry, and of sexual 

 selection, this is admitted by the great majority of naturalists ; and 

 this, as we shall see, is for the present enough. 



The second group of opponents do not question the general correct- 

 ness of the principle or the validity of natural selection in certain cases. 

 But they object that the principle does not explain all structures. To 

 suppose that it must, implies a misapprehension. It never was pre- 

 tended that natural selection could, by itself alone, account for the 

 fashioning of organic nature ; laws of organic structure have always 

 been supposed to act simultaneously with it. Mr. Darwin himself has 

 dwelt on this aspect of the problem, but, as was natural, it has no para- 

 mount place in his treatise, despite its importance. If I mistake not, 

 in the innumerable essays which have been written on the Darwinian 

 theory, sufficient stress has not been laid on the fact that the laws of 

 organic structure must account for whatever in organisms is either not 



