THE HISTORY OF ANIMAL LIFE 415 



one occurs in North Carolina, one in China and one in Tasmania. 

 The wide separation of the Uving members of these groups is un- 

 doubtedly due to their great antiquity and to the obliteration of 

 other intermediate representatives. 



(3) Food Supply: Animals penetrate and persist in regions 

 which provide adequate food and avoid regions that are sterile. 



(4) Number of Offspring: Animals which reproduce rapidly 

 and in large numbers distribute more widely than do those which 

 reproduce less rapidly. 



(5) Climate: Animals penetrate and persist in regions in which 

 climatic conditions are favorable. Changes in climate bring about a 

 corresponding withdrawal and redistribution. 



These facts are in themselves simple and obvious. The addition of 

 another fact is necessary to account for the present distribution of 

 animals, namely, that modern forms are derived by evolution from 

 ancestral forms. This fact becomes equally obvious when the pres- 

 ent-day fauna of an area is compared with the fossil records of 

 that region, for present-day animals native to a continent show dis- 

 tinct relationships to extinct forms found on the same continent. 

 This is illustrated by the faunas of all the major land areas. In fact, 

 the geological records which indicate the probable time of separa- 

 tion of the continents are in agreement with the fossil records of 

 the animals that existed before and after the separation. The island 

 of Madagascar affords an interesting illustration. This island is 250 

 miles off the east coast of Africa and geologists inform us that it 

 has been separated from Africa since the Tertiary Era. Its modern 

 animals do not include the large mammals of the mainland of 

 Africa, but only those forms which existed on the mainland during 

 the Tertiary, that is, when it was still connected with the continent, 

 lemurs, insectivors, and a few other forms. Fossil remains of these 

 are common to both Madagascar and to the mainland, but the 

 modern types are peculiar to the island and show the evolutionary 

 changes in an isolated group over a long period. 



