248 THE WORLD OF LIFE 



species which show other stages in the reduction of the lower 

 jaw. 



We have here, therefore, a most remarkable and very rare 

 phenomenon, in which we are able to see progressive evolution 

 upon what seems to be a wrong track which, if carried further, 

 might be disastrous. Usually, in such cases, the too much 

 developed or injuriously developed form simply dies out, and 

 its place is supplied by some lower or less modified species which 

 can be more easily moulded in the right direction. But here 

 (owing probably to some exceptionally favourable conditions), 

 after first lengthening both lower jaw and lower tusks to keep 

 pace with the upper ones, a reversal of the process occurs, 

 reducing first the lower tusks, then the lower jaw, till these 

 tusks completely disappeared and the lower jaw was reduced 

 to the most useful dimensions in co-ordination with a greatly 

 lengthened and more powerful trunk. Although in this case 

 the gaps are still rather large, there can be no doubt that we 

 have here obtained a view of the line of development of the 

 most remarkable land mammals now living from a small gen- 

 eralised ungulate mammal, as indisputable and as striking as 

 that of the horses from the little five-toed Eohippus of the 

 American Eocene. 



It may be here mentioned that the huge American Mas- 

 todon has been found in the same deposits with stone arrow- 

 heads, and was undoubtedly hunted by early man; as was also 

 the huge mammoth whose beautifully curved tusks form its 

 chief distinction from the living Indian elephant (Eig. 86). 

 This species is abundant in the frozen mud at the mouths 

 of the Siberian rivers; and in some cases the whole body is 

 preserved entire, as in an ice-house, and the flesh has been 

 sometimes roasted and eaten by the natives. Remains of 

 skeletons have been found in our own country and over a large 

 part of Northern Europe and Asia ; while its portrait has been 

 drawn from life by prehistoric man, either upon the tusks 

 themselves or upon the flat portions of the horns of reindeer 

 which he hunted for food. 



