THE ANCESTRY OF THE HORSE 171 



developing more and more speed ; for it is a 

 rule that the fewer the toes the faster the ani- 

 mal : the fastest of birds, the ostrich, has but 

 two toes, and one of these is mostly ornamen- 

 tal ; and the fastest of mammals, the horse, 

 has but one. 



All breeders of fancy stock, particularly of 

 pigeons and poultry, recognize the tendency 

 of animals to revert to the forms whence they 

 were derived and reproduce some character of 

 a distant ancestor ; to " throw back," as the 

 breeders term it. If now, instead of repro- 

 ducing a trait or feature possessed by some 

 ancestor a score, a hundred, or perhaps a thou- 

 sand years ago, there should reappear a char- 

 acteristic of some ancestor that flourished 

 100,000 years back, we should have a seeming 

 abnormality, but really a case of reversion ; 

 and the more we become acquainted with the 

 structure of extinct animals and the develop- 

 ment of those now living, the better able are 

 we to explain these apparent abnormalities. 



Bearing in mind that the two splint bones 

 of the horse correspond to the upper portions 

 of the side toes of the Hippotherium and 



