412 PROGRESSION AND VARIATION. chap. xxi. 



is always most severe between those which are most closely 

 allied and which fill nearly the same place in the economy of 

 nature. Hence, when the conditions of existence are modi- 

 fied, the original stock runs great risk of being superseded 

 by some one of its modified ofishoots. The new race or 

 species may not be absolutely superior in the sum of its 

 powers and endowments to the parent stock, and may even be 

 more simple in structure and of a lower grade of intelligence, 

 as well as of organization, provided, on the whole, it happens 

 to have some slight advantage over its rivals. Progression, 

 therefore, is not a necessary accompaniment of vai'iation and 

 natural selection, though, when a higher organization hap- 

 pens to be coincident with superior fitness to new conditions, 

 the new species will have greater powder and a greater chance 

 of permanently maintaining and extending its ground. One 

 of the principal claims of Mr. Darwin's theory to acceptance 

 is that it enables us to dispense with a law of progression 

 as a necessary accompaniment of variation. It will account 

 equally well for what is called degradation, or a retrograde 

 movement towards a simpler structure, and does not require 

 Lamarck's continual creation of monads; for this was a 

 necessary part of his system, in order to explain how, after 

 the progressive power had been at work for myriads of ages, 

 there were as many beings of the simplest structure in exist- 

 ence as ever. 



Mr. Darwin labors to show, and with no small success, 

 that all true classification in zoology and botany is, in fact, 

 genealogical, and that community of descent is the hidden 

 bond which naturalists have been unconsciously seeking, 

 w^hile they often imagined that they were looking for some 

 unknown plan of creation. 



As the '' Origin of Species"* is in itself a condensed 



■•■ Origin of Species, p. 121, 



