Where did Life Begin? 47 



with the forethought and Intelligence of a 

 Columbus, while to claim that they were 

 coaxed and led along by favoring conditions 

 Is to assert that all the conditions of this long 

 northern journey to find a suitable crossing, 

 and afterward of an equally long southern trip 

 to their present homes, must have been, If 

 there has been any sort of uniformity in the 

 thermal system of the earth of an opposite 

 character, and therefore. If In one case they 

 were favorable to the movement. In the other 

 they must have been equally unfavorable ; but 

 plants never move, and animals rarely, against 

 conditions which are unfavorable to any ex- 

 tent. 



It Is true, so far as simple direction Is con- 

 cerned, that In the exceptional case of the 

 receding of the ice at the close of the glacial 

 period, plants and animals which had been 

 hurried southward by the cold moved again 

 to the northward, with the like exceptional 

 movement of a warm climate to the north- 

 ward. Both exceptions are, however, of just 

 such a character as to prove the rule. In 

 each case the whole movement of organic life 



