38 A NEW THEORY OF EVOLUTION. 



animals, by their classification, to the natur- 

 alist. The expert could also explain each 

 successive step in development, and point 

 out the changes in the structure, just as the 

 morphologist can specify the higher, or in 

 some cases the lower specialisation of the dif- 

 ferent organisms that succeeded each other. 



Taking a wide, tall, spreading tree as an 

 illustration, the expert might show how 

 the piston and cylinder, like the stem of 

 the tree, have developed in size and char- 

 acter ; how the cylinder got its power first 

 from atmospheric pressure only, then from 

 air and steam combined, and later from 

 steam only ; while at the same time the 

 stem threw off branches on all sides- 

 represented by the condenser, the super- 

 heater, the fly-wheel, governor, and other 

 improvements, that again on their part 

 developed in character and efficiency. 



The expert might then invite attention 

 to the manner in which the changes were 

 effected : how the first engines were simplest 

 in construction ; how the design of an exist- 

 ing type of engine was utilised, so far as 

 it would serve, for the new ; how some 

 organ of the old engine was transformed 

 into something different in the new ; and 

 how occasionally a fragment of some member 



