130 MAMMALIAN DESCENT. [Lect. V 



As to apparent uniformity, they are in contrast with, 

 the Marsupials, whose outward form and adaptive 

 modification of teeth and limbs are much greater. But 

 in that which lies deeper than teeth or limbs 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 present hving 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 

 back again all those types that nature has wasted and 

 buried. If aU those hidden treasures of the secret 

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

 their traces even there, could 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 intelligence. But as in the rude forefathers 

 of the hamlet we have the quiet and unambitious 

 progenitors of the men who, when their time comes, 

 turn the world upside down, so in those Eocene and 

 early Miocene quadrupeds — the equivalents of our 

 little living Insectivora — we have the rough unhewn 

 forms from which our noblest types have arisen. In 

 those days the Mammalia, generally, had not only 



