118 



ANIMAL KINGDOM. 



jaws or mandibles, has a circle of five of them ; and the nervous sys- 

 tem, when distinct, is circular in arrangement. 



III. Mollusks. — The structure, essentially : (1) a soft fleshy bag, 

 containing the stomach and viscera, (2) without a radiate structure, 

 and (3) without articulations or jointed appendages. The animals of 

 the Oyster and Snail are examples. Similar parts are repeated on 

 the right and left sides of a median plane, as in Articulates and Ver- 

 tebrates, and not around a vertical axis, as in Radiates. They are 

 essentially simple in fundamental structure, and not multiplicate in 

 successive parts, like an Articulate. 



Figs. 147-149. 



IP 





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Radiates.— Fig. 147, an Echinus without its spines, — the Clypeus Hugi of the Oolyte; 148, the 

 living Pentacrinus Caput-Medusse of the West Indies (XK); a > b , c i d i outlines of the stems of 

 different species of Pentacrini ; 149, plates composing the body of the Orinid, Batocrinus longi- 

 rostris (wrongly reversed in copying from Hall). 



Figs. 150 to 159 represent some of the kinds of Mollusks. Figs. 

 150, 153, 154, 155, are shells of different species; 156, the shell of a 

 Snail, with its animal ; 158, another shell, the Nautilus, with its 

 animal ; 152, a magnified view of a minute coral, with the living 

 animals projecting from the cells, which, although apparently radiated 

 like a polyp, are still Mollusks, because this radiation is only external, 

 as is apparent in Fig. 152 a, which represents one of the animals 

 taken out of the cell and more magnified. Fig. 159, on the next 

 page, is another Mollusk, — a Cephalopod, — having some resem- 

 blance to a Radiate in the position of the arms, but none beyond this. 

 The name Mollusk is from the Latin mollis, soft. The shells are for 

 the protection of the soft, fleshy bodies. 



IV. Articulates. — Consisting (1) of a series of joints or segments ; 

 (2) having the legs, when any exist, jointed ; (3) having the viscera 



