64 ASCAROIDEA 



frequently bent S-wise. Uterine branches opposed. Ovi- 

 parous. 



Hab. Adults, in soil or fresh water. Larvae, at first in soil 

 or fresh water, afterwards becoming parasitic (until nearly 

 full grown) in body-cavity of Arthropods (chiefly insects) or 

 MoUusca. 



1. Mermis Dujardin, 1842. 



For synonyms see discussion below. 



With the characters of the family. 



Genotype : M. nigrescens Dujardin, 1842. 



Dujardin, 1842, Compt. rend. Acad. Sci., Paris, xv, 117; 

 Hagmeier, 1912, Zool. Jahrb., Syst., xxxii, 521 ; Daday, 1913, 

 Math.-natw. Ber. Ungarn, Leipzig, xxvii, 214; Cobb, in 

 Ward and Whipple, 1918, Fresh-water Biology ; Steiner, 1923, 

 Journ. Hered., Washington, xiv, 147. 



Attempts have been made to split up Mermis into a consider- 

 able number of genera. The characters available for this 

 purpose are very slight and do not appear to be of sufficient 

 importance to justify the erection of genera. Purely for the 

 sake of convenience, it might be useful to retain the various 

 names proposed as subgenera, but even this appears to us 

 somewhat unnecessary at present. The following key, which 

 is taken in a modified form from Cobb's article on the Mermi- 

 thidae in Ward and Whipple's Fresh-water Biology (1918), 

 indicates the nature of the classification adopted by some 

 recent authors. To the genera included in the key must be 

 added Agamermis Cobb, Steiner and Christie, 1923 (Journ. 

 Agric. Res., Washington, xxiii, 926), the only important 

 character of which is that the parasitic larva, on entering its 

 host, sheds a large portion of its body at a preformed 

 " node." Some further genera have been still more recently 

 proposed. 

 I. Subcutieula with only two longitudinal fields. 

 Cuticle with criss-cross fibres. 

 Spicules paired Neomermis v. Linstow, 1904. 



II. Subcutieula with more than two longitudinal fields. 

 A. Longitudinal fields six. 



A. Cuticle without criss-cross fibres. 



rt. spicules paired. . . Mesomermis Daday, 1911. 

 h. spicule single. 



a. Vagina of adult S-shaped 



Limnomermis Daday, 1911. 

 /3. Vagina of adult not S-shaped 



Pseudomermis de Man, 1903. 



B. Cuticle with criss-cross fibres. 



a. Vagina of adult S-shaped. 



a. spicule single . Paramermis v. Linstow, 1898. 

 p. spicules paired. . Mermis Dujardin, 1842. 



b. Vagina of adult not S-shaped 



Bathymermis Daday, 1911. 



