K. E. VON BAER. — PHILOSOPHICAL FRAGMENTS. 195 



marks which I have there made find their application here, and 

 since besides it is accessible to but few, I shall not hesitate to 

 prefix an extract from that essay for the purpose of building 

 further upon it. 



I wish befoi'e all things to draw attention to the distinction 

 between the grade of development of an animal and the type of 

 its organization. The grade of development of an animal con- 

 sists in the greater or less heterogeneity of its elementary parts 

 and of the separate divisions of a complex apparatus ; in a w^ord, 

 in its greater histological and morphological differentiation. The 

 more homogeneous the whole mass of the body is, so much the 

 lower is the grade of its development. The grade is higher 

 when nerves and muscles, blood and cell-substance, are sharply 

 distinguished. The more the elementary parts differ from one 

 another, so much the more developed is the life of the animal in 

 its various phsenomena ; or rather we should say, that the more 

 various the separate manifestations of animal life, the more 

 heterogeneous are the elementary parts by which that life is 

 brought about. 



It is the same with the separate divisions of an apparatus. 

 The organization is higher w^hen the divisions of a whole system 

 or apparatus are less like one another and possess more indivi- 

 duality, than when a greater similarity pervades them. It is a 

 higher grade of development, therefore, when the difference be- 

 tween the brain and spinal cord is greater, than when the original 

 similarity is less disturbed. If we carefully discriminate between 

 this relation of higher development and the relation of type, we 

 shall readily overcome a multitude of difficulties w hich stand in 

 our way, while we adopt the more or less generally predominating 

 theory of a single continual line of progressive development from 

 the Monad to Man. Let us take Fishes for an example. Be- 

 cause they possess a brain and spinal cord, together with an 

 internal skeleton, and everywhere exhibit the great vertebrate 

 type, they are raised above the heads of all the Invertebrata ; 

 and it is made a matter of wonderment that Bees, and the ma- 

 jority of insects w^hich undergo a metamorphosis, exhibit more 

 skill and a far more manifold vital activity. In Bees, however, 

 nerves and muscles are far more differentiated than in Fishes. 

 The single divisions of an apparatus or of an organic system are 



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