502 LIFE OF PROFESSOR HUXLEY chap, xxxi 



on the front limb and three on the hind limb. Judging 

 from the completeness of the series or forms so far, he 

 ventured to indulge in a prophecy. 



Thus, thanks to these important researches, it has become 

 evident that, so far as our present knowledge extends, the his- 

 tory of the horse-type is exactly and precisely that which could 

 have been predicted from a knowledge of the principles of 

 evolution. And the knowledge we now possess justifies us com- 

 pletely in the anticipation that when the still lower Eocene 

 deposits, and those which belong to the Cretaceous epoch, have 

 yielded up their remains of ancestral equine animals, we shall 

 find, first, a form with four complete toes and a rudiment of the 

 innermost or first digit in front, with, probably, a rudiment of 

 the fifth digit in the hind foot; while, in still older forms, the 

 series of the digits will be more and more complete, until we 

 come to the five-toed animals, in which, if the doctrine of evo- 

 lution is well founded, the whole series must have taken its 

 origin. 



Seldom has prophecy been sooner fulfilled. Within two 

 months, Professor Marsh had discovered a new genus of 

 equine mammals, Eohippus, from the lowest Eocene de- 

 posits of the West, which corresponds very nearly to the 

 description given above. 



He continues : — 



That is what I mean by demonstrative evidence of evolu- 

 tion. An inductive hypothesis is said to be demonstrated when 

 the facts are shown to be in entire accordance with it. If that is 

 not scientific proof, there are no merely inductive conclusions 

 which can be said to be proved. And the doctrine of evolution, 

 at the present time, rests upon exactly as secure a foundation 

 as the Copernican theory of the motions of the heavenly bodies 

 did at the time of its promulgation. Its logical basis is of pre- 

 cisely the same character — the coincidence of the observed facts 

 with theoretical requirements. 



He left New York on September 23. " I had a very 

 pleasant trip in Yankee-land," he writes to Professor Baynes, 

 " and did not give utterance to a good deal that I am re- 

 ported to have said there." He reached England in good 

 time for the beginning of his autumn lectures, and his 



