THE EOUNDWORMS OF DOMESTIC SWINE. 41 



CLASSIFIED LIST OF ROUND WORMS PARASITIC IN DOMESTIC 



SWINE. 



Specific descriptions are omitted from the following list as these 

 have already been given in the key to the roundworms of swine. 

 Arranged according to their respecive orders, families, and genera, 

 the roundworms reported as parasitic in domestic swine are as follows: 



Class Nemathelminthes: Cylindrical worms without a prebuccal ciliary apparatus 

 provided with a variable nervous system, not forming a ventral 

 chain. Generally dioecious. 



Order Nematoda. Nemathelminthes: Provided with a complete digestive tube. 

 Family Angiostomidae. Nematoda: Having two heterogenetic generations, 

 one of free-living males and females and one of hermaphroditic 

 or parthenogenetic forms which are parasitic. 



Genus Strongyloides. Angiostomidse : Parasitic form with mouth 

 opening directly into the relatively very long subcylindrical 

 esophagus. Vulva posterior of the middle of the body. Uterus 

 double. Two ovaries. Free-living form with mouth opening into 

 a vestibule or pharynx, followed by an esophagus whose anterior 

 portion is fusiform and posterior portion globular. 



Strongyloides suis. 



Family Gnathostomidae. Nematoda: Body furnished throughout its length, 

 or only anteriorly, with chitinous blades or wings, serrated posteri- 

 orly. Head subglobular, covered with simple spines. 

 Genus Gnathostoma: With the characteristics of the family. 



Gnathosloma hispidum. 



Family Trichinellidae. Nematoda: Esophagus consisting of a chain of single 

 cells, the lumen of the esophagus passing through the center of 

 each cell. Anterior portion of body containing the esophagus 

 usually very slender; posterior portion containing the intestine 

 and reproductive organs more or less swollen. One testicle, one 

 ovary. 



Subfamily Trichinellinse. Trichinellidae : Male without spicule. Female 

 ovo viviparous. Adulte in intestine of host produce larvae which 

 penetrate into the muscles, become encysted, and develop to 

 maturity when the flesh of this animal is eaten by another animal. 

 Genus Trichinella. Trichinellinse : Very small worms with capillary 

 bodies. Progressively increasing in diameter posteriorly. Male 

 with two conical posterior appendages forming a copulatory bursa. 

 Vulva of the female in the anterior fifth part of the body. 



Trichinella spiralis. 



Subfamily Trichurinse. Trichinellidae: Male with spicule. Female 

 deposits eggs characterized by the presence of an opening at each 

 pole closed by a pluglike operculum. Egga do not hatch until 

 swallowed by a suitable host. Development, so far as is known, 

 direct, without an intermediate host. 



Genus Trichuris. Trichurinae: Anterior portion of body very long 

 and slender. Posterior portion of body containing the intestine 

 and reproductive organs relatively thick and much shorter than 

 the anterior portion. Posterior portion of male rolled dorsally 

 into a spiral. Spicule surrounded by a prepuce-like sheath. 

 Posterior portion of body of female slightly curved. Vulva near 

 the beginning of the posterior portion of body Trichuris suis. 



