CHAPTER XXIII 

 NEMATODA. SUBFAMILY III. STRONGYLIN^ 



Worms of the Large and Small Intestines; Other Strongyles 



These worms are parasitic in the digestive tract, rarely in the respi- 

 ratory organs. The buccal capsule is present. The bursa of the male 

 is well developed and has one or two dorsal rays and two lateral ray 

 systems of six rays each. There are two spicules. The vulva of the 

 female is usually posterior to the middle of the body, but may be anterior 

 to the middle. There are two ovaries. 



The eggs are segmented at the time they are deposited. The embryos 

 are rhabditiform. The development, so far as known, is direct. In 

 some forms the development is complex, involving a nodular phase or 

 larval migration. 



Based mainly upon the formation of the bursal rays and the location 

 of the vulva, the Strongylinse have been grouped by Railliet and Henry 

 into five tribes, as follows : 



Tribe I. OEsophagostomese 



Tribe II. Strongyleae (Ankylostomese) 



Tribe III. Bunostomese 



Tribe IV. Cylicostomese 



Tribe V. Syngameae 



I. (Esophagostomeae. Strongyhnae (p. 280). — The bursa of the male 

 has two lateral lobes united by a smaller median lobe. In each lateral 

 lobe there are six rays. The ray of the median lobe divides into two 

 main branches, each of which again divides into two. The vulva of 

 the female is situated a short distance in front of the anus; uteri diver- 

 gent. The tribe includes three genera, as follows : 



Genus I. (Esophagostomum 

 Genus II. Chabertia (Sclerostomum) 

 Genus III. Agriostomum 



II. StrongyleaB. Strongylinse (p. 280). — The ventral and latero- 

 ventral rays of the lateral bursal lobes are close together and parallel. 

 The medio-lateral and postero-lateral rays are not close together and 

 parallel. The dorsal raj^ ends in tridigitate terminations. The vulva 

 of the female is situated in the posterior third of the body; uteri diver- 

 gent. The tribe includes four genera, as follows: 



Genus I. Strongylus 



Genus II. Ankylostoma 



Genus III. Uncinaria 



Genus IV. Characostomum 



