224 NEMATHELMINTHES 



S. equinus Miill. The armed palisade worm. Male 20 to 30 mm. 

 long; female 23 to 55 mm. long, 2 mm. thick j body red or brown, straight 

 and rigid ; mouth with small teeth ; egg .09 by .05 mm. : common in the 

 caecum or colon of the horse, causing colic; the young worms live in 

 water and moist earth and pass directly in drinking water into the 

 horse; they are also found in the abdominal arteries where they cause 

 aneurisms.. 



7. Cttcullanus 0. F. Miiller. Small worms with 2 lateral chitinous 

 plates on the head and with rudimentary bursa; mouth ridged longi- 

 tudinally; male with a spicule; vulva in the middle of the body: several 

 species. 



C. elegans Zeder. Male 8 mm. long; female 13 mm. long; body 

 yellowish or reddish; mouth with 6 papillae: in the intestine of the 

 perch and other fish. 



Family 7. ASCAEIDAE. 



Body often rather stout and large; mouth surrounded by 3 promi- 

 nent lips, 1 dorsal and 2 ventral; oesophagus with 1 or 2 bulbs; hinder 

 end of male spirally curved and usually 1 or 2 spicules project from the 

 anus: several hundred species, almost all intestinal parasites in 

 vertebrates. 



Key to the genera of Ascaridae here described: 



ai Large nematodes with prominent lips 1. Ascaris 



02 Small nematodes with usually small lips. 



&i Male with a sucker before the anus 3. Heterakis 



&2 No sucker present 2. Oxyuris 



1. Ascaris L. Large worms in which the 3 lips are set off by a 



constriction, forming a distinct knob at the front end of the body; 



ossophagus without distinct bulb; male with 2 



•gi /fB^ ^^ equal spicules and numerous ventral caudal papil- 



/ t^y i\\ fix 1^® • several hundred species, which live in the 



v^i^i^fV 11 I I i I intestines of birds and mammals. 

 ^ & c A. lumbricoides L. Eelworm (Fig. 357). Male 



JcrffiS. VorB?a?nT '^'' *^ ^^ ^^' ^^^^ ^ ^^- *^^^^' ' ^^^^^^ ^^ *^ ^^ 



b! 6ort^i ZVotToll ^^- 1«^^?' ^ ^^- t^i^kj ^^S (^i^- 345, C) brown, 

 fro^n't end?''*'"''^ ""'^"^ °^ ^i*^^ roughened surface, about .06 mm. by .05 

 mm.; body with the appearance of an earth 

 worm : in the small intestine of man and domestic animals, sometimes in 

 considerable numbers, especially in children, when they are dangerous 

 parasites; occasionally found in the liver, trachea, and other organs; 

 development direct, the eggs pass out with the feces, and the young 

 larvae develop in water or moist earth; infection is got in drinking water 

 or from the ground or from the skin of raw fruits. 



