CLASSIFICATION 411 



ancestors were small animals, about the size of the aver- 

 age dog, with four hoofed toes on each foot. This type 

 became developed into many species, some of which, 

 like the graceful and swift gazelle camels and the exces- 

 sively long-necked giraffe camels, became extinct. Others 

 continued to exist, and migrating into South America, 

 evolved into the llama, guanaco, alpaca, and related 

 species. Still others crossed the ancient land bridge into 

 the Old World, and became transformed into the modern 

 type. Those remaining in North America died out long 

 ago. 



In addition to an increase in bodily size and several 

 other characteristic features of the group, the digits dis- 

 appeared with the exception of the third and fourth, the 

 hoofs became reduced to small, conical nails, and the 

 weight of the body was supported by fleshy pads. All of 

 these evolutionary changes are evidenced by a wealth of 

 fossil remains, and the history of the camel is accord- 

 ingly as well established as that of the horse. 



It is important to bear in mind that geologists are 

 agreed that the great rock masses in which these fossil 

 horses, camels, and other animals are entombed form an 

 unbroken series. The lowest strata were first formed, and 

 the uppermost are the most recent. The paleontologist 

 is equally positive that the fossils in the oldest deposits 

 are the most primitive and generalized, and that the 

 various species are more and more complex and specialized 

 as the latest strata are approached. To the open-minded 

 student of biology these facts present unmistakable evi- 

 dence of the reality of evolution. 



Classification. — The history of the camel family 

 illustrates two important facts. In the first place the one- 

 and two-humped camels, the llama, guanaco, and alpaca 

 are the descendants of a common ancestor. Secondly, 

 these are distinct species at the present time, owing to 

 the dying out of the intermediate stages or connecting 

 links. To express it graphically, the family history of 



