1 86 STUDIES FOR STUDENTS 



interpretation of climatic and land-mass conditions in the Ter- 

 tiary time. Throughout the book evidence is constantly adduced 

 to show the strength of the author's position. I shall quote 

 merely enough of the introduction to give an idea of the 

 theory. 



Upon page J the author says: "There is a considerable 

 probability that at least a very large proportion of the animals 

 that have populated the globe in the later geological epochs 

 originated high up in the northern hemisphere, if not, indeed, in 

 the neighborhood of the pole itself (which is known to have 

 enjoyed a genial climate during the Tertiary period), and that 

 they gradually migrated southwards in a series of waves, proba- 

 bly under pressure of the development of new and higher types 

 in high latitudes ; and it is to such southerly migrations that the 

 present marked differentiation of the fauna of different parts of 

 the earth's surface is chiefly due. Whether such a northerly 

 origin held good for the terrestrial life of the Secondary epoch, 

 there are no means of determining; but it would appear that the 

 higher animals (which were chiefly reptiles) of that epoch were 

 very similar throughout the world, and that the differentiation of 

 faunas had scarcely, if at all, commenced." .... "With mam- 

 mals the case is very different. The earliest known forms, which 

 date from the Triassic and Jurassic rocks, are chiefly marsupials 

 and forms apparently allied to the monotremes, and it is proba- 

 ble that most of the descendants of these, as is more fully indi- 

 cated in the sequel, migrated southwards during the early part 

 of the Tertiary epoch, to find in Australasia a refuge from the 

 competition of higher forms. Of the higher placental mam- 

 mals, none of the modern types make their appearance before 

 the Oligocene and Miocene periods, while many do not antedate 

 the Pliocene. Their southern migrations accordingly took place 

 later on in the Tertiary period, one of the earliest movements 

 being the wandering of lemuroids, insectivores, and civet-like 

 carnivores into South Africa and Madagascar. On the other 

 hand, many other higher types, such as the hippopotami, giraffes, 

 and antelopes, which were abundant in Europe and southern 



