44 Where did Life Begin ? 



durlnof the acre of the movement of these coal- 

 plants, as it is that the coal-plants made it 

 themselves. And what is true of the course 

 of migration of plants and animals of their 

 age Avould, under uniform laws, causes, and 

 conditions, be true of such movements in all 



ages. 



VI. 



A GREAT variety of opinions have been en- 

 tertained and many interesting theories formed 

 in accounting for the similarity of species and 

 genera upon the Eastern and Western con- 

 tinents. If, as we have claimed, a zone around 

 the North Pole, sufficiently removed therefrom 

 to receive the minimum of the sun's influence 

 consistent with animal and vegetal life, has 

 necessarily, in its climatic progress, been in 

 condition to maintain successively all forms of 

 life which have ever existed on the earth, and 

 If a region of increasing cold surrounded by 

 this zone dispersed these various forms of 

 life in all directions down the Asiatic, the 

 European, and North American continents 



