ON BIOLOGY. 47 



spised, and the light their careful study has thrown upon 

 many problems touching the origin of their kind 

 is simply incalculable. Many hundreds of them 

 are in our possession, and the number is con- 

 stantly being added to each year. Bearing in 

 mind what has already been said relative to 

 the geographical distribution of existing mammals, what 

 would we naturally look for among the fossil forms of the 

 present geological era in any given locality? Naturally, 

 the fossil and sub-fossil specimens of the existing mam- 

 mals of that locality; and do we find them? It is exactly 

 what we do find, and the fossilized bones as they are dis- 

 covered are ascertained to have belonged to individuals 

 of identically the same species of those now living, or in 

 the case of the extinct types to very closely related 

 species, genera, families and so on. In other words, all 

 over the world the fossil florae and faunae of the Recent 

 epoch of the Psychozoic era are of species still living over 

 the regions where such material is discovered. 



To some extent this is also characteristic of 

 the next preceding geologic system or of the 

 Quarternary; but, and still adhering to the mammalia 

 as our example, we meet with some very remarkable 

 differences. Now it is a well-known fact that during 

 the Quarternary period, in all the high- latitude regions, 

 the earth's crust experienced many profound oscillations 

 which were accompanied by great climatic changes. 

 Mammals, as a class, culminated during those times, and 

 the pristine types of men appeared early on the scene. 

 The geologic history of the world passed through the 

 Glacial, Champlain and Terrace epochs During the first 

 the earth's crust, everywhere in high latitudes, was 

 elevated to a height of 2,000 feet or more above its present 

 level. This area was sheeted over with a great mantle of 

 ice, which sloped away far down into the temperate 

 zone. An arctic climate prevailed. The reverse move- 

 ment took place during the Champlain epoch and the 

 entire region was again depressed, and that to such an 

 extent that the seas stood upward of a 1,000 feet above 

 their present levels. Lastly, the Terrace epoch was 

 characterized by the whole region to which we refer 

 gradually coming to assume its present physical aspects. 

 So there was, during this time, a gradual rising of the 

 land of the high latitudes, accompanied by a gradual ap- 

 proach to our present climate. Many of the events and 

 profound physical changes enacted during those three 

 epochs have been carefully worked out, and in detail, 



