62 THE GERM-PLASM THEORY 



decide. There are flaws in the chain of evidence, 

 which require careful and detailed consideration. 

 For instance, the genus Equus appears in the Upper 

 Siwalik beds, which have been ascribed to the 

 Miocene age. It has, however, been maintained 

 that these beds are really Lower Pliocene or even 

 Upper Pliocene. It is clear that the decision of 

 this question is of the utmost importance. If 

 Equus really existed in the Upper Miocene, it was 

 antecedent to some of its supposed ancestors. 

 Again, in the series of equine forms, Mesohippus, 

 Miohippus, Desmathippus, Protohippus, which are 

 generally regarded as coming into the direct line 

 of equine descent, Scott points out that each 

 genus is, in some respect or other, less modernized 

 than its predecessor. In other words it would 

 appear that in the succession of North American 

 forms the earlier genera show, in some points, 

 closer resemblance to the modern Equus than to 

 their immediate successors. It is possible that 

 these difficulties and others of the same kind will 

 be overcome with the growth of knowledge, but 

 it is necessary to take note of them, for in the 

 search after truth nothing is gained by ignoring 

 such apparent discrepancies between theory and 

 fact." 



So much for the actual state of the case with 

 regard to the pedigree of the horse. We have not 

 yet wholly done with that animal. Apart from the 

 evidence of his skeleton there is another line of 

 argument which has constantly been based upon 

 the occasional occurrence of stripings on the skin 

 of the legs and withers, stripings which Darwin 



