1889.] NEW-YORK MICROSCOPICAL SOCIETY. 7 



the necessary and inevitable result of all experiments, I hold 

 that Mr. Darwin's hypothesis would be utterly shattered." 



Of course, after making this very frank avowal, Professor 

 Huxley went on to say that the fatal negative evidence referred 

 to had not been produced and that, for his part, he saw reason 

 to believe that the much-desired positive evidence on the 

 other side would some day be forthcoming ; so that he was able 

 to maintain his faith in the Darwinian theory of the origin of 

 species, although evidently he could not at that time have looked 

 upon it as entirely beyond doubt. But that, I believe, was 

 twelve or fifteen years ago, and I think that since Professor 

 Marsh made his discoveries of Orohippus and other fossil- 

 horses, and the equally important Odontornithes, Professor Hux- 

 ley has considered that all really necessary " links " heretofore 

 missing have been supplied, and that he has declared the evolu- 

 tion theory to stand upon as complete and secure a foundation 

 as the Copernican theory of the motions of the heavenly bodies; 

 so that the problem of hybridism no longer has the place in his 

 mind that it occupied before the confirmatory evidence just 

 spoken of had been obtained. 



All this gees to show that to a logical mind like Professor 

 Huxley's no hypothesis is entirely satisfactory as long as it seems 

 likely to remain an hypothesis, and that such a mind, if it is in- 

 terested in the subject at all, naturally seeks for an assurance 

 that the theory is, as Mill says, " of such a nature as to be 

 either proved or disproved by comparison with observed facts." 



Professor Haeckel is not as logical as Professor Huxley, and 

 therefore to the former a point is proven by much less evidence 

 than is necessary to completely convince the latter. Haeckel 

 never attached any importance to the doubts about hybridism, 

 which at one time so much troubled Huxley, but has asserted 

 from the beginning that artificial selection can produce, and has 

 produced, genuinely new species. 



In view of the existence of these widely differing estimates 

 of the quality and quantity of proof required to establish the 

 doctrine of descent and the principle of natural selection, it is 

 almost unnecessary to say that there is at least equal divergence 

 of opinion as to the evidence needed to place the general theory 

 of evolution upon an unassailable logical basis ; for the longer 

 the line of works, the more weak points will it present to the enemy. 



