THIRD DIVISION. ARTICULATED ANIMALS. 
Tne Articulata have no internal skeleton, the articulated rings which 
surround the body, and usually the limbs, in some measure supplying its 
place. In the Annelides these rings are nearly the sole means of locomo- 
tion, as they have merely a soft and membranous body. The term arti/cu- 
lated signifies jyotnted, and the division embraces those animals, the various 
pieces of whose bodies are joined together by muscles or flexible membranes. 
Some of the families have a soft, membranous body, like the common 
earth-worm, and others have a hard, bony covering, like the lobster. There 
are four classes: Ist. The ANNELIDES, or Lted-blooded Worms; 2d. The 
Crustaceans, or Lobsters and Crabs; 3d. The Aracunipes, or Spiders ; 
and 4th. INsecra, embracing more species than any other class of the ani- 
mal kingdom. 
CLASS J. THE ANNELIDES. 
The class of the Annelides, or annulated worms, to which also our com- 
mon earth-worm and the leech belong, peoples the seas with by far the greater 
number of its genera and species. All of them are distinguished by an 
elongated and generally worm-like form of body, susceptible of great exten- 
sion and contraction. The body consists of a series of rings, or segments, 
joined by a common elastic skin; and each ring, with the exception of the 
first or foremost, which forms the head, and the last, which constitutes the 
tail, exactly resembles the others, only that the rings in the middle part of 
the body are larger than those at the extremities. The head is frequently 
provided with eyes, and more or less perfect feelers ; the mouth is armed, in 
many species, with strong jaws, or incisive teeth. The blood is red, and 
circulates in a system of arteries and veins. 
We are accustomed to associate with the idea of a worm all sorts of dis- 
gusting and revolting impressions ; and yet an examination of many of the 
Aquatic Annelides will show us that it is not without some reason that 
M. De Quatrefages remarks, — 
“Talk no more of the violet as the emblem of modesty. 
our Annelides, that, possessed of every shining quality, hide themselves 
Look rather at 
NO. XViIl. 
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