CHAPTER II 
PARASITES OF THE ALIMENTARY TRACT 
VERMES 
THE Vermes are non-vertebrate animals, possessing soft 
contractile bodies, devoid of an endo-skeleton, but con- 
stituted of a number of segments. They possess no 
articulated limbs. The organs comprising the secretory 
system are arranged in pairs. With the exception of 
the leeches, all the members of the Vermes under this 
heading which we are about to discuss are classed as 
Entozoa, or intestinal worms. Their natural habitat is 
to be found in some portion of the alimentary tract of 
a larger animal, apart from which but few can maintain 
their existence. They have no respiratory system, and 
hence need no circulatory system. 
The Vermes are divided into two chief groups : 
1. Annelida. 
2. Helminthes. 
1. ANNELIDA. 
The only members of the Annelida which are parasitic 
are the leeches, of which Hemopfis sanguisuga, the horse- 
leech, serves as an example. The Annelides are the 
only invertebrates which have red blood circulating in 
a double system of bloodvessels. The body is soft, fiat 
or cylindrical, and shows distinct transverse rings. 
Hemopis sanguisuga is a member of the Hirudine. 
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