264 ERNST IIAECKEL AND CAUL GEGENBAUR 



servativc principle. . . . Adaptation is commenced by a 

 change in the function of organs, so that the physiological 

 relatio)is of organs play the most important part in it. Since 

 adaptation is merely the material expression of this change 

 of function, the modification of the function as much as its 

 expression is to be regarded as a gradual process. In 

 Adaptation, the closest connection between the function and 

 the structure of an organ is thus indicated. Physiological 

 functions govern, in a certain sense, structure; and so far 

 what is morphological is subordinated to what is physio- 

 logical" (Elements, pp. 8-9). Gegenbaur recognised also that 

 morphological differentiation depended largely on the 

 physiological division of labour (Grundziigc, p. 49). 



It is clear that Gegenbaur realised vividly the importance 

 of function, and in this respect, as in others, he is far 

 beyond Haeckel. The same thing comes out markedly in 

 his treatment of correlation. Haeckel had no slightest 

 feeling for the true meaning of correlation. For him, as for 

 Darwin, it reduced itself to a law of correlative variation, 

 according to which " actual adaptation not only changes 

 those parts of the organism which are directly affected by 

 its influence, but other parts also, not directly affected by 

 it." 1 Such " correlative adaptation " was due to nutrition 

 being a "connected, centralised activity." 



Gegenbaur, on the contrary, had a firm grasp of the 

 Cuvierian conception, and expressed it in unmistakable 

 terms. " As indeed follows from the conception of life as 

 the harmonious expression of a sum of phenomena rigorously 

 determining one another, no activity of an organ can in 

 reality be thought of as existing for itself. Each kind of 

 function (Verrichtung] presupposes a series of other functions, 

 and accordingly every organ must possess close relations 

 with, and be dependent on, all the others" (Grundziige } p. 71). 

 The organism must be regarded as an individual whole 

 which is as much conditioned by its parts as one part is 

 conditioned by the others. For an understanding of cor- 

 relation a knowledge of functions, and of the functional 

 relations of the organism to its environment, is clearly indis- 

 pensable. 



1 History cf Creation, i., pp. 241-2. 



