ch. iv.] THE LAW OF EVOLUTION 331 



If now we contemplate in a single view the general 

 principles above illustrated, we shall seem for a moment to 

 have got into difficulties. Unavoidably, in using the word 

 Evolution, we have suggested the idea of increase in structural 

 complexity ; and such increase of course implies a con- 

 siderable amount of permanent internal rearrangement as 

 consequent upon the primary process of integration. Yet 

 under the conditions thus far studied, we find that " on the 

 one hand, a large amount of secondary redistribution is 

 possible only where there is a great quantity of contained 

 motion ; and, on the other hand, these redistributions can 

 have permanence only where the contained motion has 

 become small — opposing conditions which seem to negative 

 any large amount of permanent secondary redistribution." 

 We must therefore search for some more peculiar and special 

 combination of conditions before we can understand how 

 Evolution may result in great structural complexity. 



It is in the case of organic bodies " that these apparently 

 contradictory conditions are reconciled ; and that, by the 

 reconciliation of them, permanent secondary redistributions 

 immense in extent are made possible." The distinctive 

 peculiarity of organic bodies " consists in the combination or 

 matter into a form embodying an enormous amount of motion 

 at the same time that it has a great degree of concentration." 

 Let us enumerate the several ways in which organic bodies 

 are enabled to retain vast quantities of molecular motion, 

 without losing their high degree of concentration. The facts 

 to be contemplated are among the most beautiful and striking 

 facts which the patient interrogation of nature has ever 

 elicited. 



In the first place, while one of the four chief components 

 of organic matter is carbon, a solid substance which cannot 

 be fused by the greatest heat that man can produce, the other 

 chief components — oxygen, hydrogen, and nitrogen — are 

 gases which human art is unable to liquefy. At a temperature 



