PARASITIC ROUND WORMS 535 



79 (78) Anterior region not much slenderer than posterior region and equal 

 to it in length or shorter Capillaria Zeder 1800. 



In North American aquatic host. 



Capillaria ransomia Barker and Noyes 1915. 



Length 19 to 20 mm.; breadth of male o.oi to 0.03 mm., of female 0.022 to 0.065 mm. 

 Bursa of male small, with 2 lateral lobes. Spicule 1.36 mm. long, 0.007 mm. broad. Vulva 

 in anterior fourth of body. Eggs 0.05 by 0.02 mm. with prominent plugs. 



Duodenum of muskrat. Nebraska. 



GORDIACEA 



The Gordiacea are familiar to all as the hairworms or "hair 

 snakes" frequently found in the country in drinking troughs, 

 springs, brooks, ponds, or indeed any body of water, large or small. 

 In general appearance these worms are very much like the nema- 

 todes but the more fully their internal organization has become 

 known by study the less they seem to resemble that group in de- 

 tail, and the present tendency is to separate them as an independ- 

 ent class. Some even make the group an independent phylum. 



The body resembles a bit of fine wire or a tough root fiber in 

 appearance. It is nearly cylindrical, usually with blunt or rounded 

 anterior end and a caudal extremity of modified form, often swollen, 

 lobed, or curled in a loose spiral. 



Certain nema todes, especially Mermis which occurs free in soil 

 in the adult stage, resemble the hairworms so much externally that 

 they are often confused with them. The two differ greatly in 

 internal structure and somewhat in less important external fea- 

 tures; but by their pointed anterior end, tapering body, and 

 smooth, finely striated and somewhat transparent cuticula the 

 true nematodes are usually easily distinguished from the Gordi- 

 acea with blunt head, cylindrical body, and roughened, ordinarily 

 also papillate, irregular cuticula. Mermis in particular is most 

 readily distinguished by the pointed posterior end and when alive 

 by the active anterior region. 



In the Gordiacea a single orifice serves as the common outlet of 

 the reproductive and alimentary systems, alike in both sexes; it is 

 located near the posterior end. There are no lateral lines and the 

 male never possesses spicules. 



These animals are so opaque that little or no internal structure 

 is visible on examination either with the naked eye or with the 



