712 Mutations 



dom before sinking to the bottom of the sea, and 

 later producing the vast number of diverse 

 forms which now adorn the sea and land. 



All these evolutions, however, must have been 

 very rapid, especially at the beginning, and to- 

 gether cannot have taken more time than the 

 figures given above. 



The agency of the larger streams, and the 

 deposits which they bring into the seas, afford 

 further evidence. The amount of dissolved 

 salts, especially of sodium chloride, has been 

 made the subject of a calculation by Joly, and 

 the amount of lime has been estimated by 

 Eugene Dubois. Joly found fifty-five and Du- 

 bois thirty-six millions of years as the probable 

 duration of the age of the rivers, and both fig- 

 ures correspond to the above dates as closely 

 as might be expected from the discussion of evi- 

 dence so very incomplete and limited. 



All in all it seems evident that the duration of 

 life does not comply with the demands of the 

 conception of very slow and continuous evolu- 

 tion. Now it is easily seen, that the idea of 

 successive mutations is quite independent of 

 this difficulty. Even assuming that some thou- 

 sands of characters must have been acquired in 

 order to produce the higher animals and plants 

 of the present time, no valid objection is raised. 

 The demands of the biologists and the results of 



