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INVERTEBRAL ANIMALS. 



[. GANGLIATA. — Brain surrounding the gullet, and 

 sending out nervous filaments, which in their course ex 

 pand into ganglia. 



5 Class I. Mollusca. — Brain surrounding the gullet, and send- 

 ing out filaments, which separate irregularly. 



v Class. II. Annulosa. — Brain surrounding the gullet, and send- 

 ing out a knotted tilament to the posterior extremity of 

 the body. 



II. RADIATA. — Nervous system obscure, disseminated, 

 not appearing in the form of a collar round the gullet, 

 nor of a longitudinal cord. 



Although the Radiata appear here as the last of the Invertebral Animals, 

 it is my intention to proceed to the consideration of the species which belong 

 to the division immediately after the enumeration of the Mollusca. This 

 course I am induced to follow, because an intimate relationship appears to 

 subsist between certain groups of radiated and molluscous animals. Besides, 

 by such an arrangement, the whole of the Annulose animals will remain con- 

 nected, and occupy exclusively the second volume of this work. 



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