394 ON THE BRAIN IN THE EDENTATA. 



generally a small size of body, they were able to survive without that high degree of 

 brain-development which became a vital necessity to the Ungulate, the Carnivore, and 

 especially the Primate. 



It is not improbable that the Xenarthra are more nearly related to the primitive 

 Camivora of the Eocene epoch than are the Rodents. Otherwise it is difficult to under- 

 stand the features of the brain of Myrmecophaga. But if this is so, the Xenarthrotis 

 stem branched off from the Carnivore stock at an early epoch, and almost immediately 

 it widely diverged into a number of distinct branches. The Armadillos separated them- 

 selves from the others at a very early period, and underwent extreme bodily modifications 

 of a protective nature in order that they might be able to escape extinction, because their 

 brains had become reduced to the lowly standard of the Insectivora. 



The Sloths and Ant-eaters also diverged soon afterwards, and, althovigh their brains are 

 of no mean order, they would not be able to exist if it were not for the safe modes of 

 life which they lead, and the peculiar specializations of limb and body which so admirably 

 fit them for such habits. 



"We may conclude that the evidence of the brain clearly demonstrates that the 

 Edentata are much more nearly related to the ordinary placental mammals than is 

 commonly supposed to be the case. Not only so, but the brain has also reached a fairly 

 high stage of development in all the rejiresentatives of this extremely heterogeneous 

 group, and may certainly be placed upon a plane at least as high as that of the Rodentia. 



The features of the brain conclusively show that Orycteropus is no more nearly related 

 to the American forms than the Sheep is to the Dog. 



The gradual loss of teeth, and the associated modifications of skull and limbs, do not 

 necessarily imply a retrograde or degenerative process so much as extreme specialization 

 and adaptation to particular modes of life. 



