1 8 Where did Life Begirt? 



such life as we find on other parts of the earth. 

 Nothing, then, can be more obvious than that 

 the temperature of these now frigid zones, in 

 sHding gradually from the first extreme of heat 

 to the last extreme of cold, must have passed 

 slowly through all the grades of temperature 

 and climatic conditions which were exactly 

 suited at one time or another to all the varie- 

 ties of plants and animals which now live, or 

 ever have lived on the earth. 



There is no escape from this conclusion, ex- 

 cept by asserting that the usual climatic and 

 concurrent conditions did not in this case fol- 

 low along the line of lowering temperature. 

 But this is not only raising a groundless objec- 

 tion, one without a single fact to support it, 

 but it is also one which disturbs, contradicts, 

 and reverses the usual order of thiuQ^'s. Cer- 

 tainly the oiuis probandi should rest on him 

 who invokes the supposition. 



Of course the usual number in considering 

 this question will very properly ask whether 

 there was time enough for organic develop- 

 ment after the polar zones were cool enough 

 to maintain life, and before the other parts 



