WORM PARASITES. 61 



Some are marine, some freshwater, others live in 

 decaying matter, many are terrestrial. Those, how- 

 ever, with which we have to deal are parasitic in 

 their habits. There are three great sections of 

 Vermes : — 



(i.) The ringed or segmented Worms = the Anne- 

 lida, such as the Earthworm and Leech, which are 

 seldom parasites, those that have this habit beino- 

 external parasites such as the Horse-leech. No 

 Annelids are found to prey upon Poultry, so they 

 can at once be dismissed. 



(ii.) The Platyhelminths or c Flat Worms,' most 

 of which are parasitic in habits. These are all 

 hermaphrodites — that is, they have male and female 

 oro-ans in the same individual. 



(iii.) The Nemathehmnths or "' Round Worms/ or 

 Thread-worms, again mostly parasitic. But round 

 in shape, and tapering to a point at each extremity. 



These two latter groups are generally known as 

 Entozoa, on account of their parasitism being internal. 

 All the Entozoa have but feeble respiratorv powers, 

 respiration being carried on through the skin. They 

 are found in all manner of organs and in all kinds of 

 animals, man being subject to a great number, 

 although serious consequences in our country from 

 their presence are very exceptional. 



The Flat Worms are again divided into three 

 groups, two only of which are of importance to us 

 here. 



