PAPERS OX BIOLOGY AND AGRICULTURE 141 



other medium sized animal. On the western plains the 

 coyote breeds and raises a family almost within the lim- 

 its of towns of fifteen thousand. Smaller forms, such as 

 mink, muskrats, and foxes, now find few localities where 

 they can live in anything like their natural conditions. 



A study of the life of a longer period will show changes 

 in which man has had no part and has been no factor. 

 It is of this period that this paper gives a sketch. If we 

 go back into Tertiary times we find the Americas popu- 

 lated with a strange assemblage, a small part of which 

 foreshadows the life of the present day. Ancestral 

 horses, camels, the rhinoceroses, tapirs, and many other 

 interesting forms were working out their evolution in 

 different parts of the country. The horse went through 

 his evolution from the five to the one toe, sending 

 migrants to Europe at some stage of his development, 

 which was a fortunate thing for us, since our magnificent 

 horse fauna died out long before America was discovered 

 by Columbus, and we have been forced to replenish our 

 horses from those same European migrants of an earlier 

 day. It is difficult to imagine the reason for the extinc- 

 tion of this horse group, for they lived here in abundance 

 and in many forms that were suited to live under many 

 different conditions. It has been suggested that we place 

 the blame for their extermination on some of the proto- 

 zoan parasites that continue their work even to the pres- 

 ent day. The American horses were of all sizes and 

 types. Forms as large as the draft horses of the present 

 day, and ponies of many types were scattered over the 

 plains of the latter part of the Tertiary. 



The camels, a pure American product, also went 

 through their evolution on the plains of the middle west 

 and western America. They adjusted their bones to the 

 running adaptation with joined metacarpals to form the 

 cannon bone. A large fauna, varying from delicate deer- 

 like types to the great giraffe camel of a later day, scat- 

 tered their bones in profusion over the land in which they 

 lived. The camels of the present day are the end form 

 of this great population. A migration to Europe is rep- 

 resented by the camels now found in the east, while a 



