IV.] MINUTE MODIFICATIONS. 125 



left on each side. In the machairodus there is no upper 

 true molar at all, while the premolars are reduced to two, 

 there being only these two teeth above, on each side, 

 behind the canine. 



DENTITION OF THE SABRE-TOOTHED TIGER (mACHAIRODUS). 



With regard to these instances of early specializa- 

 tion, as also with regard to the changed estimate of the 

 degrees of affinity between forms, it is not pretended for a 

 moment that such facts are irreconcilable with " Natural 

 Selection." Nevertheless, they point in an opposite direc- 

 tion. Of course not only is it conceivable that certain 

 antique types arrived at a high degree of specialization 

 and then disappeared ; but it is manifest they did do so. 

 Still the fact of this early degree of excessive specialization 

 tells to a certain, however small, extent against a progress 

 through excessively minute steps, whether fortuitous or 

 not ; as also does the distinctness of kinds formerly sup- 

 posed to constitute connecting links. For, it must not 

 ,be forgotten, that if species have manifested themselves 

 generally by gradual and minute modifications, then the 

 al)sence, not in one but in all cases, of such connecting 

 links, is a phenomenon which remains to be accounted for. 



