EVOLUTION OF THE HORSE AND THE ELEPHANT 419 



beginning of horse life. It is often called the first horse, 

 but of course it was not a horse at all, in any proper 

 meaning of that word. The toes were already reduced 

 from the primitive number, but there were four on the 

 front foot, three on the hind. The teeth were short- 

 crowned, without a complicated enamel pattern. Such 

 an animal was well adapted to the warm, moist climate 

 of the period, feeding on soft food and traveling on soft 

 ground. Had conditions remained unchanged, there 

 would presumably have been no evolution of the horse. 



3. In the Rocky Mountains the rocks of the Ter- Lines of de- 

 tiary period have been unusually well preserved, and vel P ment 

 from them it has been possible to obtain a remarkably 

 complete series of fossils. Thus it is that the history 



of the horse has been made out, and although the family 

 belongs today to the Old World, we feel assured that it 

 developed in the New. Without going into many de- 

 tails, it will suffice to say that in successive deposits we 

 can trace a series of forms leading from the small 

 Eohippus to the horse of modern times. In the foot 

 there is a gradual reduction of the toes. In the teeth 

 the enamel pattern becomes increasingly complex, and 

 the crowns are lengthened. There is a steady, almost 

 regular increase in size. Thus the species of the horse 

 family, when found as fossils, are especially valuable to 

 the geologist as time markers. They indicate relative 

 time only, of course, like a clock the hands of which 

 moved, but on the face of which were no marks to indi- 

 cate the seconds, minutes, or hours. 



4. Naturalists, recording evolutionary processes such The theory 

 as that just described, have sometimes postulated what 



they called orthogenesis, the first part of the word mean- 

 ing "straight" or "regular," as in orthodox. This im- 

 plies that evolution follows a predetermined path, which 



