SYSTEM OF INSECTS. 371 



i. Lamarck divided the animal kingdom into two pro- 

 vinces, or subkingdoms as they are now called ; the one 

 consisting of all those animals whose skeleton is internal 

 and built upon a vertebral column, which are denomi- 

 nated Vertebrates ; and the second, of those whose ske- 

 leton or its representative is for the most part external, 

 including the muscles, these are called Invertebrates*. 

 Though this distinction is so marked as in general to 

 form a most striking characteristic, yet when these two 

 provinces approach each other, it begins to disappear. 

 Thus the vertebral column, forming one piece with 

 the shell b , becomes almost external in the Chelonian 

 reptiles, or tortoises and turtles, and almost disappears 

 in the cyclostomous fishes ; and there is the beginning 

 of an internal one in the Cephalopoda, or cuttle-fish be- 

 longing to the Invertebrates. Dr. Virey, assuming the 

 nervous system as his basis, long since divided the ani- 

 mal kingdom, without assigning names to them, into 

 three subkingdoms c ; M. Cuvier has four Vertebrata ; 

 Mollusca ; Articulata ; Eadiata d : and Mr. MacLeay, 

 finding Jive variations of that system, divides animals 

 into five provinces or subkingdoms, of which I formerly 

 gave you some account e ; viz. Vertebrata, in which the 

 nervous system has only one principal centre; Annulosa, 

 in which it is ganglionic, with the ganglions arranged 

 in a series, with a double spinal chord; Mollusca, in 

 which it is ganglionic, with the ganglions dispersed irre- 

 gularly but connected by nervous threads ; Radiata, in 

 which it isjilamentous, with the nervous threads radiating 



a VOL. III. p. 10. b Cuv. Anat. Comp. i. 173. 



- N. Diet. tfHist. Nat. \\. 25. d Ibid. 26-. 



e VOL. III. p. 12. 



2 B 2 



