324 THE STORY OF THE EAETH AND MAN. 



derivable from some primitive material. It is trui 

 that this is contrary to experience. The chemist 

 holds that matter is of different kinds, that one 

 element cannot be converted into another; and he 

 would probably smile if told that, even in the lapse 

 of enormous periods of time, limestone could be 

 evolved out of silica. He may think that this is 

 very different from the idea that a snail can be 

 evolved from an oyster, or a bird from a reptile. 

 But the zoologist will inform him that species of 

 animals are only variable within certain limits, and 

 are not transmutable, in so far as experience and 

 experiment are concerned. They have their allotro- 

 pic forms, but cannot be changed into one another. 



But if we grant this second demand, the evolutionist 

 has a third in store for us. We must also admit that 

 by some inevitable necessity the changes of things 

 must in the main take place in one direction, from 

 the more simple to the more complex, from the lower 

 to the higher. At first sight this seems not only to 

 follow from the previous assumptions, but to accord 

 with observation. Do not all living things rise from 

 a simpler to a more complex state ? has not the 

 history of the earth displayed a gradually increasing 

 elevation and complexity? But, on the other hand, 

 the complex organism becoming mature, resolves 

 itself again into the simple germ, and finally is dis- 

 solved into its constituent elements. The complex 

 returns into the simple, and what we see is not an 

 evolution, but a revolution. In like manner, in 



