CHAPTEE VI 

 PHYLUM V.: ANNELIDA OR RINGED WORMS 



THIS group is one which used to be united with the Flat- 

 worms, Thread -worms, and Ribbon -worms in the one large 

 phylum Vermes, for there is a decided superficial resem- 

 blance between all these " worms." Examination, however, 

 of their internal structure has disclosed such marked differ- 

 ences that they are now grouped in four different phyla. 



The Annelida are here considered first, because they are 

 by far the best known, including as they do common Earth- 

 worms, Sea- worms, and Leeches. 



They all are characterised by the elongated ringed body, 

 the segmentation being not merely external, but extending to 

 many of the internal organs. The coelom is well developed 

 and segmented, definite blood-vascular and nervous systems 

 are present, as well as very peculiar and distinctive paired 

 excretory organs (nephridia) which may be repeated in each 

 segment. 



The only two classes of the Annelids that will be dealt 

 with here are the Chaetopoda (the Bristle-worms) and the 

 Hirudinea (the Leeches). 



Class I. : CHAETOPODA 

 (THE BRISTLE-FOOTED RINGED WORMS) 



Type, : The Earthworm (Lumbricus terrestris). 



Earthworms are very widely distributed, and 



this special genus, Lumbricus, is common to North 



America, Europe, and North Asia. They are also to be found 



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