DISCOVERIES OF CONNECTING LINKS. 1 09 



Species " could bring to its aid. A few synthetic 

 types were at that time known ; but they were so 

 little understood as to have no particular meaning. 

 Darwin, realizing as he did that one of the weakest 

 points in his theory was the impossibility of finding 

 the many links which it demanded, was only able 

 in the first edition of his book to claim that Owen 

 had shown that Ruminants and Pachyderms were 

 connected by fossils. To-day it would take pages 

 to enumerate the different fossils found to connect, 

 in a more or less direct manner, the living with ex- 

 tinct animals and with each other. 



It may, perhaps, be well to mention a few of these 

 instances. The best-known history is that of the 

 horse family. The earliest representative was the 

 eohippus of the Eocene rocks, which had on its fore 

 feet the representations of five toes, and was a small 

 animal about the size of a fox. From this starting- 

 point the history has been carefully followed. The 

 animal becomes larger ; it loses one toe, then a 

 second ; and coming on later, two of the three re- 

 maining toes become smaller, and finally all that is 

 left of them are the so-called splint bones. Accom- 

 panying these changes are others, so that almost 

 every step in the history of this family from its five- 

 toed ancestor, is known. And not only this, but 

 the even-toed Ungulates have been similarly traced 

 back to a five-toed ancestor. Indeed, by means of 

 the numerous fossils found of late years, almost all 

 of the orders of mammals have been traced back- 

 wards by converging lines. And Cope has dis- 

 covered a very early animal which presents such 



