434 Wort/man — Studies of Eocene Mammalia in the 



arose, the inhabitants of the region had choice of one of three 

 alternatives; migration, modification to fit the new conditions, 

 or extinction. And I may add that paleontological study con- 

 cerns itself almost exclusively with deciphering the record of 

 the successes and failures of animal species along these lines. 



In the case of the Primates, their structure at the beginning 

 of the Wasatch had been fully adapted to an arboreal exist- 

 ence, as their prehensile extremities so fully demonstrate. 

 Being exclusively dependent on these conditions, they were 

 bound to follow in whatever direction the limits of the tropical 

 forests shifted ; and that the recession and gradual retreat of 

 these forests was from within the Arctic Circle in the North to 

 the vicinity of its present confines in the South, during the 

 interval between the Middle Cretaceous and the Glacial epoch, 

 is supported by an overwhelming abundance of evidence. It 

 thus becomes possible, it seems to me, to locate the place 

 of the origin of a large number of the higher Mammalia. 

 Whether a similar series of changes took place at the South 

 Pole, giving rise to its own peculiar types of mammals, is as yet 

 uncertain, but at the same time not improbable. At all events, 

 the Primates belong to the North, and it is within the Arctic 

 Circle that they had their beginning. *. 



The second inquiry with which we are at present concerned 

 is the kind and character of mammal from which the Primates 

 were probably derived. Unfortunately the evidence necessary 

 for a final solution of this problem is very far from complete. 

 The question of the oldest known Primates has not yet been 

 settled with satisfaction. Certain species from the lower Ter- 

 tiaries of this country, notably the Puerco and Torrejon beds, 

 have been variously referred to the Primates and Creodonta by 

 investigators who have studied them — Cope, Scott, Osborn, 

 Earle, and Matthew. These animals are known almost exclu- 

 sively from the teeth, and in a few instances only are any of the 



* In this connection I wish to call attention to the admirable work of Hon. 

 G. Hilton Scribner, New York, 1883, " Where did Life Begin?" ' It is now 

 quite impossible to state by whom this view was first entertained, but the 

 late Professor Asa Gray, in a private letter to Mr. Scribner in 1884, dis- 

 tinctly claimed the credit of having been the author of the migration on 

 north and south lines. Reference to Gray's published writings, however, as 

 well as to those of Saporta, Nathorst, and Dawson, fails to show that any 

 attempt was ever made by any of these eminent investigators to put forward 

 the proofs and formulate the view into a distinct hypothesis of the Polar 

 origin of life. In this Mr. Scribner was clearly the first, and so ably and 

 logically was the Polar Origin theory presented, that Dr. Gray in comment- 

 ing upon it was led to remark that Mr. Scribner's position was " simply 

 incontestable." In the light of the great mass of evidence now at hand, 

 it is easy to recognize and to appreciate fully the extreme probability of 

 such a view ; but when we recall the almost total lack of evidence in its 

 favor at the time Mr. Scribner's book appeared, his work becomes all the 

 more noteworthy, and in my judgment is entitled to a high rank among 

 intellectual performances of a similar kind. This should thus be known as 

 the Scribnerian Theory of the place of the origin of life. 



