130 MAMMALIAN DESCENT. [Lect. V 



As to ap})areiit luiiformity, tliey are in contrast witli 

 the Marsupials, whose outward form and adaptive 

 modification of teeth and limhs are much greater. But 

 in that which lies deeper than teeth or liml)S there 

 is evidence, in the Insectivora, that they are a group 

 whose organisation is full and fertile of the power of 

 adaptive change. 



Now if we compare our })resent living Insectivora 

 with the extinct Eutheria of the early Tertiary period, 

 these two Faunae are manifestly similar ; they would 

 indeed form one very uniform group if we could get 

 l)ack again all those types that nature has wasted and 

 buried. If all those hidden treasures of the secret 

 places of the earth, and all those that failed to leave 

 their traces even there, coidd be restored to us, even, as 

 it were, in " the valley of vision," then we should see 

 that our living Insectivora are only the waifs and strays 

 of countless groups of Pro-eutheria, of many a size 

 and shape, but with very simple tooth-crowns ; with 

 mostly pentadactyle feet ; with small brains ; and 

 with a low intelliojence. But as in the rude forefathers 

 of the hamlet we have the quiet and unambitious 

 progenitors of the men who, when their time conies, 

 turn the world upside down, so in those Eocene and 

 early Miocene quadru23eds — the equivalents of our 

 little livino; Insectivora — we have the rouGjh unhewn 

 forms from which our noblest types have arisen. In. 

 those days the Mammalia, generally, had not only 



