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 Jour — Vertebrata ,• 
Mollusca ; Articulata ,- Radiata 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; Anmdosa, 
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. 
' .V. Diet. d'HisL Nat. ii. 25. * Ibid. %'-. 
■ Vol. III. p. 12—. 
2 B 2 
