Chap, in.] the Dogma of Constancy of Species. 153 



Darwin clearly perceived and consistently kept in view the 

 discordance between the systematic affinity of organisms and 

 their adaptation to the conditions of life, which De Candolle 

 had already but imperfectly recognised. The clear perception 

 of this discordance was in fact the one thing needed to mark the 

 true character of the natural system, and to make the theory of 

 descent appear as the only possible explanation of it. The 

 fact which morphologists and systematists had painfully 

 brought to light, but had not sufficiently recognised in its 

 full importance, that two entirely different principles are united 

 in the nature of every individual organism, that on the one 

 hand the number, the arrangement, and the history of the 

 development of the organs of a species point to corresponding 

 relations in many other species, while on the other hand the 

 manner of life and the consequent adaptation of the same 

 organs may be quite different in these allied species. This 

 fact admits of no explanation but the one given by the theory 

 of descent ; it is therefore the historical cause and the strongest 

 logical support of that theory, and the theory itself is directly 

 deduced from the results which the efforts of the systematists 

 have established. That the majority of systematists did at 

 first distinctly declare against the theory of descent can sur- 

 prise no one who observes that they were so little able to give 

 an account of their own mode of procedure, as appears in so 

 striking a manner from Lindley's theoretical speculations. 



One consequence of this want of clearness in combination 

 with the dogma of the constancy of species has been already 

 mentioned in the introduction ; namely, the notion professedly 

 adopted by Lindley, Elias Fries, and others, that an idea lies 

 at the foundation of every group of affinities, that the natural 

 system is a representation of the plan of creation. But the 

 question, how such a plan of creation could explain the strange 

 fact that the physiological adaptations of organs to the con- 

 ditions of life have nothing at all to do with their systematic 

 connection, was quietly disregarded j and in fact the notion, 



