CLASS-BOOK OF ZOOLOGY. 155 



many quadrupeds, birds, and fishes. These worms are a 

 fruitful source of disease. 



§ 669. The class of Worms may be divided into the 

 following five Orders, viz. : 



1st Order. — Gelatinous Worms, (Zoophyta, Lin. :) the 

 body of which is gelatinous, transparent, and not com- 

 posed of jointed limbs ; as the Infusory Animalcules, the 

 Polypes, the Sea-blubber, etc. 



2d Order. — Corals, (Corallia, Lin. :) which are im- 

 moveable stony or horny dwellings of minute animals, 

 similar to Polypes ; as Madrepores, Sea-fans, etc. 



3d Order. — Shellfish, (Testacea, Lin. :) the body of 

 which is partly or entirely enclosed in a calcareous shell ; 

 as Oysters, Snails, and Cuttlefish. 



4th Order. — Prickly Worms, (Echinodermata, Cuv. :) 

 the body of which is cartilaginous, in some cases with a 

 calcareous crust, and covered with prickles ; as Sea- 

 stars, and Sea-urchins, (the Sea-eggs of the cabinets.) 



5th Order. — Long-bodied or True Worms, (Intestina, 

 Lin. :) which have a skin composed of jointed links, and 

 are without any external organs of motion ; as Earth- 

 worms, Leeches, and Tape-worms. 



1st Order. — Gelatinous Worms. 



Fig. 38. 



The Hydra.— {Hydra fusca) 



