K. E. VON BAER. PHILOSOPHICAL FRAGMENTS. 22? 



foresee that this assertion will be regarded as too sweeping, since 

 only a few investigators of the present day declare themselves 

 for it openly and decidedly ; in fact, not a few have pronounced 

 decidedly against it. I must therefore devote a few lines to 

 show the correctness of my statement. 



That doctrine has, as I believe, far more unconscious than 

 conscious advocates. It seems to me, indeed, that a number of 

 conceptions, proceeding from the uniserial view, and belonging 

 to times long past, have propagated themselves, and without our 

 knowledge have given a colour to our view of organic affinities, 

 which is not the result of investigation. Are not the notions 

 that Cephalopoda or Crustacea are allied to Fishes, or even pass 

 into them, expressions of this fundamental view ? They could 

 hardly have proceeded from an immediate and free comparison 

 of their organisms. 



Just as incomprehensible is the alliance between Echinoderms 

 and Mollusks. 



Do not these attempts to build bridges between two distant 

 countries proceed from the endeavour to make each a link in a 

 chain? Having learnt, in fact, to understand the Crustacea 

 according to the type to which they belong, and regarding them 

 as the most developed forms of this type (with which I do not 

 agree), the next endeavour was to pass from them a step further. 

 In the same manner it was believed that a way led from the 

 highest Radiata to other regions. If, however, in accordance 

 with our view, we regard the separate forms or groups of forms 

 as variations upon a theme, we shall find that the transitions are 

 but few and isolated; consequences of the modifiability of a 

 form, but on that very ground not in themselves necessary and 

 determinate. We shall then not be misled into seeking agree- 

 ments between things which are heterogeneous, since we do not 

 regard the serial succession as the condition of the varieties of 

 animal forms. 



The controversy, whether the Articulata or the Mollusca are 

 the higher, seems to me also to depend upon this view of a 

 uniserial development. If we properly comprehend the essence 

 of the different types, it appears easy enough to comprehend 

 how the plastic formations predominate in the one, in the other 

 sensitive and motor organs. The heart and the liver of Mollusks, 



15* 



