8 



PROCEEDINOS OF THE NATIONAL MUSEUM. 



VOL. 50. 



ov.- 



trttr- 



ami— 



m 



Life history. — The life history presents several possibilities : 

 First. The parthenogenetic female parasitic in the intestine pro- 

 duces eggs which are deposited in the epi- 

 thelial cells lining the crypts and covering 

 the villi in the small intestine. 

 From these eggs embryos develop 

 which transform to rhabditiform 

 larvae, escape to the lumen of the 

 intestine, and are passed out in 

 the feces; outside of the body 

 these become mature free-living 

 males and females, mate, and pro- 

 duce free-living rhabditiform 

 embryos; these transform into 

 free-living filariform larvae, and 

 these may enter the body of the 

 host by the mouth or through the 

 skin and develop into the par- 

 thenogenetic females. 



Second. The parasitic female 

 produces eggs, which give rise, as 

 above, to rhabditiform larvae, 

 which are passed out in the feces 

 and there transform into filari- 

 form larvae; these latter infect 

 the host animal, thus omitting the 

 free-living adult stage. 



Third. It is also thought that 

 the parasitic female may give rise 

 to rhabditiform larvae, which 

 transform to filariform larvae in 

 the intestine of the host, and by 

 subsequent development to adults 

 cause autoinfection. 



Hosts. — Oryctolagus cuniculus 

 {Lepus cuniculus).^ Epimys nor- 

 vegicus {Miis decu7nanus) , "and 

 other rodents." 



Location. — Small intestine. 



Localities. — Europe, United 

 States, ? South America. 

 In Ransom's (1911«) excellent monograph of the nematodes of 

 ruminants he has covered this species so well that I have been able 



i/i^.- 



Cnt- 



-e. 



. -ut 



Fig. 3. — Strongyloides papil- 

 Losus. Body of parasitic 



ADX7LT IN REGION OF VULVA. 



«., Egg; int., intestine; ov., 

 ovart; ut., uterus; vuL, 

 VULVA. X 300. After Ran- 

 som, 1911. 



Fig. .f.— Stron- 

 gyloides PA- 

 piLLosus. Fe- 

 male OF FREE 

 LIVING gene- 

 ration, an.. 

 Anus; 6., pos- 

 terior BULB 

 OF esopha- 

 gus; C.,EGGIN 

 uterus; es., 

 esophagus; 

 int., intes- 

 tine; nil., 

 vulva. xioo. 

 After Ran- 

 som, 1911. 



