September 9, 1898.] 



SCIENCE. 



319 



like areas, filled up inland seas or shallow 

 gulfs" (p. 328). Towards the close of the 

 Tertiary the great mountain ranges of Asia 

 and Europe, the Alps, Pyrenees, Caucasus, 

 Himalayas, as well as the Atlas, and the 

 Cordillera of North and South America, 

 were upheaved. The old Tertiary num- 

 mulitic beds were, in the western Alps, 

 raised to a height of 11,000 feet, and the 

 Himalayas to a horizon 16,000 feet above 

 the sea, while there were corresponding 

 elevations in western North America and 

 in the Eocky Mountain region. 



The evidence from fossils show, what has 

 not been disputed, that the climatic zones 

 were by this time established. In Europe 

 the older Tertiary was decidedly tropical, 

 in the Miocene subtropical, but the climate 

 of Europe was somewhat lowered late in the 

 Miocene, as shown by the absence of palms.* 

 At the end of the Tertiary, i. e. , during the 

 Pliocene the earth's climate was but slightly 



*Jaeger suggests that the occurrence, in the later 

 geological periods, of warm-blooded vertebrates, pro- 

 tected by feathers or hair, was due to the fact that the 

 earth then became cooler than in the preceding ages. 

 His explanation of the origin of feathers and hair is 

 as follows : " If the average temperature of an animal 

 body is considerably higher than that of the surround- 

 ing media, oscillations of these media have a stimu- 

 lating effect upon the skin of the animal. This leads 

 to a tendency to form papillary chorian [sic] cells, 

 and these afterwards produce hair or feathers, which 

 represent two of the most characteristic features of 

 warm-blooded animals. He adds that this "stimu- 

 latory effect upon the skin can only be due to low 

 temperatures." The body temperature of the birds 

 and mammals being high, and the covering of the 

 hair or feathers rendering them proof against the ex- 

 tremes of heat or cold, we can see that there is a coin- 

 cidence between this and the fact that these classes 

 began to increase in numbers towards the end of the 

 Mesozoic, and especially at the opening of the Ter- 

 tiary, when the climatic zones began to be established. 

 So also in the case of whales the loss of hair is com- 

 pensated for by the blubber. Why, however, feathers 

 developed in birds, rather than hair, is a problem no 

 one has attempted to solve, though feathers, of course, 

 better adapt the bird to flight; no flightless birds hav- 

 ing such well developed feathers as those capable of 



warmer than at present. It should here be 

 noticed that while Greenland, Iceland, 

 Spitzbergen and Grinnell Land under 81° 

 north latitude were during the late Tertiary 

 ' abnormally warm ' the Tertiary floras of 

 northeastern Asia, including those of 

 Kamtschatka, Amurland and Saghalien 

 and that of Japan, ' show no sign of a 

 similar warmth, but rather point to a cli- 

 mate colder than that of the present day ' 

 (Kayser, p. 354).* 



The Tertiary was apparently also a time 

 of more or less inter-continental migrations 

 or interchange of life-forms, which crossed 

 the oceans over so-called continental 

 bridges. Bering Strait was at one time 

 such a bridge, and to explain the geo- 

 graphical distribution of certain forms there 

 is thought to have been a more or less con- 

 tinuous land-connection between India and 

 Africa, and between Africa and South 

 America, and possibly in the Eocene be- 

 tween Australia and southwestern Asia. 



However hypothetical these continental 

 bridges may be, we do know that Central 

 America and the Isthmus of Panama were 

 elevated at the end of the Miocene, and that 

 the bridge thus formed between North and 

 South America became an avenue for the 

 interchange of mammals and other animals 

 which materially modified the distribution 

 of life in the southern and northern parts 

 of our continent. 



extended flight. (See G. Jaeger, Problems of Nature, 

 Translated by Henry G. Schliehter, D.S.C., London, 

 1897, p. 66.) 



It might be suggested that the broad vane-like sur- 

 face which characterizes feathers as compared with hairs 

 may have been due to the fact that they would better 

 support the body in flight; this difference from scales, 

 as well as their greater lighfaess, giving this sort of . 

 armature an advantage over scales on the one hand 

 and hairs on the other. 



*It has also been claimed by J. W. Gregory that the 

 fossil plants of the Greenland Miocene beds may have 

 been drifted from the southward, and that the tempera- 

 ture of the Polar region was not so elevated as Heer had 

 been led to suppose. [Nature, Vol. 56, p. 353, 1897.) 



