WOEMS. 



123 



Nematodes (Thread-Worms or Eound- Worms). — These are for 

 the most part parasitic, and infest plants as well as animals ; the 

 common Eound- Worms living parasitically in man (Ascaris, Sfron- 

 aijlus, Trichoceplialus) belong to this Order (50-72). Sometimes they 



Fig. 14. 



Fie;. 15. 



Fig. 16. 



Fig. 14. Diagram of the structure of a Turbellarian : ng, nerve- (cerebral) 



ganglia; lib, nerve-branches; yg, yolk-glands; t, testis; o, ova; oi», ovary; 



c, cirrus ; m, mouth ; ph, pharynx. 

 Fig. 15. Diagram of a Nemertine : h, brain ; m, mouth ; n, renal organs ; 



id, diverticula of intestine ; g, gonads ; sn, side nerve-trunk ; pr, proboscis in 



its dorsal sheath. 

 Fig. 16. Diagram of the structure of a Nematoid ; m, mouth ; pli, pharj^nx ; 



a, anus ; o, orifice of genital tube. 



are parasitic in their early stages and later live a free life — such are 

 Gordkis and 3Iermis. A specimen of a Mantid is exhibited from which 

 half the body of the infesting Gordkis (70) has already protruded 

 (Fig. 17). One of the most remarkable Gordii is the great elongated 



