178 K.E. VON BAER. PHILOSOPHICAL FRAGMENTS. 



than the Vibriones, are less active, but very much surpass in 

 this respect the globular Volvoces with their allies. The lower 

 animals teach us, what we have already learnt from the chaotic 

 dwellers in the Mussels, that the kind of movement (which is 

 here almost the only manifestation of life) depends upon the 

 form of the body ; thence a duplex movement where the body, 

 as in the Cercarice, is composed of two forms. On this account 

 indeed, Miiller's characters for the genera of the Infusoria, which 

 are taken, not from the general figure of the body, but from 

 non-essential organs, hairs and spines, are so little fitted to 

 yield natural groups, and leave us in want of an altogether 

 new nomenclature, and of new definitions of the genera. 



In order to obtain a just insight into the mutual affinities of 

 animals,it is before all things necessary to distinguish the different 

 types of organization from the different grades of development, 

 The general neglect of this distinction seems to us to have led to 

 the strangest approximations. We have theCephalopods supposed 

 to form a transition to Fishes, and the Echinoderms connecting 

 Polypes with Intestinal Worms. But metamorphose a Cepha- 

 lopod as you will, there is no making a fish out of it, save by 

 building up all the parts afresh. Granting that the Cephalopoda 

 are the most developed Mollusks, and that the Fishes are the 

 least developed Vertebrata ; and that therefore there is a certain 

 approximation between them, so far as regards the degree of 

 development ; yet to the unprejudiced eye they present no closer 

 affinity, L e. agreement in formation. Can it be denied that a 

 Pike is infinitely more similar to Man than a Sepia ? As little 

 can we recognise any affinity between the Starfish and the Tape- 

 worm. In the former the repetition of structure is successive 

 in a circle, in the latter in a longitudinal direction. That is the 

 sole agreement. But even in this there lies a contrast. 



Our persuasion, that the grades of development must be 

 distinguished from the types of organization, is founded upon 

 the following considerations : We know that all the functions of 

 the perfect animal body contribute to a general result, to the 

 life of the animal ; but also that the general mass manifests the 

 total life (for animal life is always a totality) ; that the albuminous 

 jelly of the Polype digests, breathes, contracts, feels, and pro- 

 pagates ; that, however, all these functions go on as it were in 



