CLASSIFICATION. 299 



suys Agassiz, *'were bent upon establishing one continual 

 uniform series to embrace all animals, between the links of 

 which it was supposed there were no unequal intervals. 

 The watchword of their school was : Natura non facit 

 mltum. They called their system la chains des etres,'' 



The classification of Ouvier, based on internal organization 



instead of external appearance, was a great advance. He 



asserted that there are four principal forms, or four general 



plans, on which animals are constructed ; and in pursuance 



' of this assertion, he drew out the following scheme. 



First Branch. Animalia Vertebrata 

 Cl. 1. Mammalia. 

 Cl, 2. Birds. 

 Cl. 3. Reptilia. 

 Cl. 4. Fishes. 



Second Branch. Animalia Mollx/sca. 



Cl. 1. Cephalapoda. 



Cl. 2. Pteropoda. 

 Cl. 3. Gasteropoda. 

 Cl. 4. Acephala. 

 Cl. 5. Brachiopoda. 

 Cl. 6. Cirrhopoda. 



Third Branch. Animalia Articulata. 

 Cl. 1. Annelides. 

 Cl. 2. Crustacea. 

 Cl. 3. Arachnides. 

 Cl. 4. Insects. 



Fourth Branch. Animalia Radiata. 

 Cl. 1. Echinoderms. 

 Cl. 2. Intestinal Worms, 

 Cl. 3. Acaleph^. 

 Cl. 4. Polypi. 

 Cl. 5. Infusoria, 



