CLASSIFICATION. 209 



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 

 saUum. They called their system la chaine dcs etres" 



The classification of Cuvier, based on internal organization : 

 instead of external appearance, was a great advance. lie 

 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 Yertebrata 

 Cl. 1. Mammalia. 



Cl. 2. Birds. 

 Cl. 3. &EPT1LIA. 



Cl. 4. Fishes. 



Second Branch. Animalia Molltjsca. 

 Cl. 1. Cephalapoda. 

 Cl. 2. Pteropoda. 

 Cl. 3. Gasteropoda. 

 Cl. 4. Acephala. 

 Cl. 5. Brachiopoda. 

 Cl. 6. Cirrhopoda. 



Third Branch. Animalia Artictjlata. 

 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. Acalephje. 

 Cl. 4. Polypi. 

 Cl. 5. Infusoria. 



