336 THE MICROSCOPIST. 



18. Echinorrhynchus. Inhabits the intestine of several 

 vertebrates. One found in a leucaemic child. 



2d Order. Nematode*. Threadworms. Bodies round, 

 threadlike, with mouth and intestine. Armament, when 

 present, of papillae or spikelets and hooks within the 

 mouth. Development by single metamorphosis, yet many 

 young forms have an abode altogether different from that 

 of their parents, and often the young and sexually mature 

 inhabit different organs or different animals. Some live 

 parasitically in plants. 



1st Sub- order. Strong yloidce. Nernatodes with anus. 



1st Family. Ascarides. Mouth with three lips or pa- 

 pillae. Sometimes teeth in the throat. Most lay hard- 

 shelled eggs. 



19. Ascaris Lumbricoides. Roundworm. Cylindrical 

 body. Male 250 mrn. by 3 mm. Female 400 mm. by 5.5 

 mm. Tail of male conical and hooked. 



20. A. Mysto.x. Smaller than the preceding. Identical 

 with the common round worm of cats. 



21. Oxyuris Vermicidaris. Threadworm. Body fila- 

 mentous, white. Three lips on the head. Inhabit chiefly 

 the rectum and large intestine, but may wander to vagina. 



2d Family. Strong yloidce. Mouth generally armed with 

 a horny surface or hooks. 



22. Strongylus Gigas. Long red worm. Viviparous. 

 In the pelvis of the human kidney. 



23. S. Longevaginatus. Filamentous, white. 



24. 8. Armatus. Cause of the so-called colic of the 

 horse, which is really aneurism of the intestinal arteries. 



25. S. Duodenalis. Body cylindrical. Mouth wide, 

 with two claw-shaped hooks. In Italy and Egypt found 

 in the intestines by thousands. Gives rise to anaemia, etc. 



3d Family. Trichotrachelidce. Moderately large, longi- 

 tudinally striated worms. 



26. Trichocephalas Dispar. Long threadworm. Body 

 short, 2 cent, long by 1 mm. thick, with filiform neck, 



