NEMATOIDS. ROUND WORMS. {Nema cord, eidos form). 



Cylindroid form ; digestive apparatus ; sexes apart in different individu- 

 als ; water vascular canals ; nerves from glanglia at gullet ; oviparous, vivi- 

 parous, or ovoviviparous ; most, without alternate generation, develop 

 from ovum to maturity in one host. Division : Trichosoma, trichocepha- 

 lus, filaria, spiroptera, dispharagus, ascaris, heterakis, oxyuris, strongylus, 

 sclerostoma, uncinaria, ossophagostoma, stephanurus, physaloptera, globo- 

 cephalus, syngamus, gnathostoma, ollulanus, trichina, rhabdonema. 



The true round worms are easily distinguished by their cylin- 

 droid form, by the possession of true digestive organs and by the 

 separation of the sexes in different individuals. They have a set 

 of water vascular canals, two on each side of the body communi- 

 cating at the level of the oesophagus, also a nervous system com- 

 posed of two ganglia situated on the two sides of the gullet, 

 connected by two transverse branches, and sending nerves for- 

 ward into the head and backward on the two sides of the body. 

 They are oviparous, viviparous or ovoviviparous. The embryos 

 generally develop in the higher animals without any alternate 

 generation, such as takes place in the cestoids and trematoids, 

 yet in certain species (trichina, sclerostoma, enstrongylus) the 

 young sexually immature worms may live for a time in the blood- 

 vessel or encysted in solid tissues of the same host or another. 

 The characteristic features of the different groups and genera of 

 round worms may be given as follows : 



SECT. I. WHIP- WORMS CHARACTERS. 



Body long ; in two distinct parts of unequal thickness ; mouth 

 very small, round, anus almost terminal. Spiculum single. 

 Ovum with round end-extension. 



Genus: Trichosoma (trix hair, soma body), Hair body. Thick- 

 ness to length as 1:150 to 1:400. Short thick anterior 

 part containing oesophagus and anterior part of in- 

 testine ; caudal, hair-like part has intestine and genera- 

 tive organs. Anus terminal. One spiculum with exten- 

 sible membranous sheath. Vulva at junction of thick 

 and thin parts of body. Ova elliptical with clear trans- 

 lucent button-shaped enlargement at each end. 

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