NO. 2131. 



NEMATODE PARASITES OF RODENTS— HALL. 



201 



large specimens. It is a large conspicuous transverse aperture 

 limited by prominent lips. From this a short vagina extends to 

 the infundibuliform ovijector, which has a muscular wall and a 

 chitinous lining (lig. 202). The part nearest the vagina is the vesti- 

 bule and the part most remote is the sphincter. The chitinous lining 

 of the sphincter is in folds, forming oblique valves on the wall. The 

 free extremity of the valves is directed toward the vulva and the 

 vestibule, so that eggs may pass from the common trunk of the uterus 



200. 262. 



Figs. 260-202.— Spirura talpae. 2(;o, Anterior extremity, showing boss or struma. Enlarged. 

 After NiTzscH, 1829. 261, Posterior extremity of female. Enlarged. After Nitzscu, 1S29. 

 262, a, Ovijector; 6, sphincter of ovijector. After Seurat, 1912a. 



into the vestibule and out, but not back. The common trunk of the 

 uterus is a short tube, which promptly divides to form the two 

 divergent uteri. The eggs are roundly elliptical and are 48 to 52 jw 

 long by 30 to 38 [i thick. They are 10 to 30 in number. 



Life history. — Eggs from this worm, if ingested by cockroaches, 

 develop to larvae wdiich are found encysted in the body cavity in 

 lenticular capsules attaining a size of 2 by 3 mm. in diameter, the 

 cysts forming from the epithelium of the tracheae. The cyst is 

 formed of two separable membranes, the external fibrous, the in- 

 ternal structureless. The larva lies folded on itself inside of the 



