" DIE STAMME DES THIERREICHS " 73 



the American palaeontologist, Marsh, has made 

 known to us in the Western territories of the United 

 States another series of ancestors of the horse, 

 which can be carried back further than the European 

 series right up to the primitive and pentadactylar 

 types. Strange to say, the precursors of the Horse 

 in America differed from those of the old world, 

 and the singular conclusion has been drawn from 

 this that two series of fossil animals, entirely 

 different at their outset, have tended more and 

 more to assimilation until they unite in a com- 

 mon descendant. This convergence of two distinct 

 branches is, truth to say, highly improbable. It 

 is safer to suppose that, when dealing with such 

 similar series of intermittent forms, it becomes im- 

 possible to settle which, in the series of eventual 

 ancestral forms, is the real starting-point of the 

 branch. Let us assume, for instance, that the 

 evolution of the Equine series in the same direction 

 still continues ; it would, in the course of a few 

 million years, finally end in animals which had lost 

 all traces of the lateral toes, still present in a 

 rudimentary state in our existing Horse. The 

 palaeontologists of the epoch would then be able 

 to recognize the existence of an ancestor which 

 possessed somewhat the same characteristics as 

 our Horse, but would not be able to determine 

 whether it was the Horse, the Ass, the Zebra, or the 

 Quagga, that should be regarded as the true pre- 

 cursor of this new type.* 



* The genealogy of the horse is explained more satisfactorily by 

 intermittent and irregular migrations of the American types into the 

 Old World. 



