XIV PREFACE. 



animal of which the one fossil skeleton is the remains 

 belonged to the Equine family of the order Pachy- 

 dermata, and that it had a simple stomach, with all 

 the other general peculiarities of organisation which 

 characterise that group ; whilst the animal of which 

 the other fossil skeleton is the remains belonged to 

 the order Ruminantia> and that it had a compound 

 stomach, with all the other general peculiarities of 

 organisation which characterise animals that chew 

 the cud. 



Whilst then it is a simple matter of comparison 

 and induction to infer from an examination of the 

 fossil skeleton of an extinct animal the anatomical 

 structure of the other organs of its body which have 

 disappeared from decay, it is the merest assumption 

 to assert that a comparison of the observable mode 

 of the embryonic development of an individual 

 animal, with the various persistent forms throughout 

 the zoological scale, supplies facts from which the 

 doctrine of Evolution may be legitimately deduced. 



In regard to the three-toed Hipparion form, we 

 can recognise, with Mr. Huxley, in its bones and 

 teeth, characters indicating a near alliance to the 

 horse. We may also, on the other hand, recognise 

 in the embryo of the horse indications transitory 

 indications of the phalanges of a would-be three-toe 

 development, but to say, for that reason, that the 



