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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 50. 



Anus is 110 fi from the tip of the tail. The prominent vulva is situ- 

 ated immediately in front of the anus. The single uterus is pro- 

 vided with muscular ovijeetor. Eggs 90 by 75 [x in diameter, rela- 

 tively large and variable in size. 



Hosts. — Microtus arvalis {Arvicola arvalis), Apodemus sylvaticus 

 {Mus sylvaticus) ., Pitymys suhterraneus {Arvicola suhterraTwus) . 

 Location. — Small intestine. 

 Locality. — France (Kennes). 



The above description is from Dujardin (1845). Von Linstow 

 (1882) describes and figures what he regards as the same species 



collected from Talpa europaea. The 

 differences in the two descriptions seem 

 to the present writer to hardly warrant 

 combining them, especially in view of 

 the different hosts. Linstow's male is 

 only 990 fx long and 46 ^ wide. The cuticle 

 is very thick and has peculiar transverse 

 folds which form several longitudinal 

 rows on the body. The intestinal wall is 

 filled with refractive nuclei. I have 

 commented on this finding in the dis- 

 cussion of IleligTrhosommn vexillatuni. 

 The bursa has two lobes defined by the 

 narrow dorsal ray which bifurcates near 

 its distal extremity to form a fork in- 

 closing the shallow middorsal incision of 

 the bursa (fig. 199). The three lateral 

 rays and the latero-ventral ray form a 

 divergent system of thick rays. The 

 somewhat narrower ventro-ventral ray curves posteriorly away from 

 the latero-ventral. The narrow externo-dorsal rays lie a little nearer 

 the externo-lateral rays than to the dorsal rays. The spicules are 197 

 // long, filiform, and united at the tip. The male is spirally rolled 

 and invisible to the naked eye. It is, according to von Linstow, the 

 smallest of all known strong}des. 



It appears, then, that von Linstow's male specimens Avere less than 

 half the length of Dujardin's, whereas the spicules in the latter case, 

 instead of being more than twice as long were roughly 35 per cent 

 longer. In view of this and the difference in host animals, it seems 

 more likely that comparative study would show von Linstow's 

 species to be a new one than that the tAvo species would prove to be 

 identical. 



Fig. 199.— Heligmosomum minutum. 

 Posterior extremity of male. 

 Enlarged. After von Linstow, 

 1882. [Probably not H. minutum 

 (Dujardin). See text.] 



