DARWIN AND CUVIER 2 -.9 



lation " a new signification, whereby they lost to a large 

 extent their true and original functional meaning. 



It is true that Darwin himself, as well as his successors, 

 believed that natural selection was all-powerful to account 

 for the evolution of the most complicated organs, but it may 

 be questioned whether he realised all the conditions of the 

 problem of which he thus easily disposed. He says, rightly, 

 in an important passage, that " It is generally acknowledged 

 that all organic beings have been formed on two great laws 

 Unity of Type, and the Conditions of Existence. By 

 unity of type is meant that fundamental agreement in 

 structure which we see in organic beings of the same class, 

 and which is quite independent of their habits of life. On 

 my theory, unity of type is explained by unity of descent. 

 The expression of conditions of existence, so often insisted 

 upon by the illustrious Cuvier, is fully embraced by the 

 principle of natural selection. For natural selection acts by 

 either now adapting the varying parts of each being to 

 its organic and inorganic conditions of life : x or by having 

 adapted them during past periods of time : the adaptations 

 being aided in many cases by the increased use or disuse of 

 parts, being affected by the direct action of the external 

 conditions of life, and subjected in all cases to the several 

 laws of growth and variation. Hence, in fact, the law of the 

 Conditions of Existence is the higher law ; as it includes, 

 through the inheritance of former variations and adaptations, 

 that of Unity of Type" (Origin, 6th ed., Pop. Impression, 

 pp. 260-1). It is clear that Darwin took the phrase 

 " Conditions of Existence" to mean the environmental 

 conditions, and the law of the Conditions of Existence 

 to mean the law of adaptation to environment. But that 

 is not what Cuvier meant by the phrase : he understood by 

 it the principle of the co-ordination of the parts to form the 

 whole, the essential condition for the existence of any 

 organism whatsoever (see above, Chap. III., p. 34). 



Of this thought there is in Darwin little trace, and that is 

 why he did not sufficiently appreciate the weight of the 

 argument brought against his theory that it did not account 

 for the correlation of variations. 



1 Italics mine. 



