136 ELEPHANTS 



have developed (they had come into existence a good 

 deal earlier), and we find the remains of ancestral forms of 

 the living kinds of cattle, pigs, horses, rhinoceroses, tapirs, 

 elephants, lions, wolves, bears, etc., embedded in the suc- 

 cessive layers of Tertiary deposits. Naturally enough, 

 those most like the present animals are found in late 

 Pliocene, and those which are close to the common 

 ancestors of many of the later kinds are found in the 

 Eocene, whilst we also find, at various levels of the Ter- 

 tiary deposit, remains of side-branches of the mammalian 

 pedigree, which, though including very powerful and remark- 

 able beasts, have left no line of descent to represent them 

 at the present day. We have been able to trace the great 

 modern one-toed horses, zebras, and asses, with their com- 

 plicated pattern of grinding-teeth back by quite gradual 

 steps (represented by the bones and teeth of fossil kinds 

 of horses), to smaller three-toed animals with simpler 

 tuberculated teeth, and even, without any marked break in 

 the series, to a small Eocene animal (not bigger than a 

 spaniel) with four equal-sized toes on its front foot, and 

 three on its hind foot. We know, too, a less direct series 

 of intermediate forms leading beyond this to an animal 

 with five toes on each foot and " typical " teeth. In fact, 

 no one doubts that (leaving aside a few difficult and 

 doubtful cases) all such big existing mammals, as I 

 mentioned above, as well as monkeys and man, are derived 

 from small mammals intermediate in most ways between 

 a hedgehog and a pig which flourished in very early 

 Eocene times, and had five toes on each foot, and " a 

 typical dentition." Even the elephants came from such a 

 small ancestral form. The common notion that the extinct 

 fore-runners of existing animals were much bigger than 

 recent kinds, and even gigantic, is not in accordance \vith 

 fact. Some extinct animals were of very great size 

 especially the great reptiles of the period long before the 



