Mmt in the Light of Evolution 



*' Primary Factors of Evolution," chap, ii, pp. 

 74-171. 



Chart IV shows the succession In geological 

 appearance of the principal forms of animals. 

 The time of first appearance Is marked by a 

 cross opposite the geological period and under 

 the name of the group of animals. Our knowl- 

 edge of the first geological appearance of the 

 different orders of placental mammals Is very 

 defective. All the principal orders are repre- 

 sented In the Eocene period, and must have origi- 

 nated earlier, as remains of mammals have been 

 found in triassic rocks. The primitive amphibia 

 v/ere the Stegocephala. The earliest reptiles 

 were probably much like the recent Hatterla. 

 The Theromorpha were probably the ancestors 

 of mammals. Archasopteryx was the earliest 

 bird, with teeth and long tall.^ 



Chart V aims to show the successive origin of 

 organs.^ Their period of most rapid develop- 

 ment Is marked by a double cross. A single 

 cross marks slower Improvement. — means a 

 decline In relative Importance owing to the rise 



^ Compare Jordan and Kellogg: "Evolution of Animal 

 Life," p. 297; Metcalf, "Organic Evolution," p. 105. 



212 



