240 ESSAY ON CLASSIFICATION 



animal organs prevail, and the same distinction is again drawn among 

 the Vertebrata. Each of these embraces two circles founded upon the 

 development of one particular system of organs, etc. It cannot be 

 expected that the systems founded upon such principles should pre- 

 sent a closer agreement with one another than those which are based 

 upon anatomical differences; yet I would ask, what becomes of the 

 principle itself, if its advocates cannot even agree upon what anatom- 

 ical systems of organs their classes are founded? According to Oken, 

 the Mollusks (Acephala, Gasteropoda, and Cephalopoda) represent 

 the system of circulation; at least in the last edition of his system 

 he views them in that light, whilst Fitzinger considers them as repre- 

 senting the system of sensibility. Oken identifies the Articulata 

 (Worms, Crustacea, and Insects) with the system of respiration, Fitz- 

 inger with that of motion, with the exception of the Worms, includ- 

 ing Radiata, which he parallelizes with the system of reproduction, 

 etc. Such discrepancies must shake all confidence in these systems, 

 though they should not prevent us from noticing the happy com- 

 parisons and suggestions to which the various attempts to classify 

 the animal kingdom in this way have led their authors. It is almost 

 superfluous to add that, great as the disagreement is between the sys- 

 tems of different physiophilosophers, we find quite as striking dis- 

 crepancies between the different editions of the system of the same 

 author. 



The principle of the subdivision of the classes among Invertebrata is here exemplified 

 from the Radiata (Echinodermata). Each series contains three orders. 



1st Series. 2d Series. 3d Series. 



Evolutio prasvalens Evolutio prasvalens Evolutio praevalens 



systematis digestionis, systematis circulationis. systematis respirationis. 



Scytoderinata 

 Asteroidea. Echinodea. (Holothurioids). 



1. Encrinoidea. 1. Aprocta. 1. Synaptoidea. 



2. Comatulina 2. Echinina. 2. Holothurioidea. 



3. Asterina. 3. Spatangoidea. 3. Pentactoidea. 



In Vertebrata, each class has five series and each series three orders; so in Mammalia, 



for example: — 



1st Series. 2d Series. 3d Series. 4th Series. 5th Series. 



Evolutio Evolutio Evolutio Evolutio Evolutio 



praevalens praevalens prasvalens prievalens praevalens 



sensus tactus. sensus gustus. sensus sensus sensus visus. 



olfactus. auditus. 



