MANUAL OF NATURAL HISTORY. 319 



the body ; eyes sessile on the neck ; mucous 

 glands on sides of body. Terrestrial. 



II. ORDER. HELMINTHOID- ANNELIDS (Rhabdocoela). 



Alimentary tube simple, cylindrical or conical ; 

 oral aperture and anus variously disposed. 



I. SUB-ORDER. AMPHISTEREANS (Amphisterea). 



Neither oral nor anal aperture terminal, but both 

 either superior or inferior. 



1. FAMILY. Turbellas (Vorticidse). Body gene- 



rally tapering, covered with vibratile cilia ; 

 eyes two or four. 



2. FAMILY. Leptoplanas (Leptoplanidse). Body 



depressed, membranaceous ; intestinal canal 

 simple ; eyes one or many, on the neck. 



II. SUB-ORDER. MONOSTEREANS (Monosterea). 

 Oral or anal aperture terminal. 



3. FAMILY. Gordians (Gordiidse). Oral orifice ter- 



minal, anal inferior ; body tapering, filiform, 

 elastic, often coiled up in knots ; caudal ex- 

 tremity bifid ; eyes none, 



4. FAMILY. Short-tailed Worms (Micruridse). Oral 



orifice terminal, anal inferior ; body tapering, 

 filiform, elastic ; tail simple ; eyes six or more. 



5. FAMILY. Long -mouthed Worms (Derostomati- 



dse). Anal orifice terminal, oral inferior ; body 

 tapering ; eyes none. (Ghilophorina, Ehrenb.) 



