NO. 6 CLASSIFICATION OF NEMATODES FILIPJEV 1 7 



the form of a hollow tube cut obliquely (fig. 23), a "goose feather." 

 The genital region of the male resembles that of Mononchus in hav- 

 ing numerous papillae, tubular in some species, and a strong bursal 

 musculature (fig. 24). 



Subfamilies and Genera of the Family Mermitidae 

 Subfamily Tetradonematinae. 



Genera: Aproctonema Keilin, 1917; Tetradoneina Cobb, 1919. 

 Subfamily Mermitinae. 



Genera: Neomermis Linstow, 1904 (syn. Octomermis Steiner, 1929); 

 Mermis Dujardin, 1842; Allomermis Steiner, 1924; Pseudomermis 

 de Man, 1904; Tetramermis Steiner, 1927; Agamermis Cobb, Steiner 

 and Christie, 1923; Hexamennis Steiner, 1924; Bathymermis Daday, 

 1913; Eumerniis Daday, 1913; Paramermis Linstow, 1901 ; Limno- 

 mermis Daday, 1913 ; Hydromermis Corti, 1903 ; Gastromermis Mico- 

 letzky, 1925; Mesomerrnis Daday, 1913; Eomermis Steiner, 1929; 

 ?Bolbinium Cobb, 1920; ?Colpurella Cobb, 1920; Usolaimiiwi Cobb, 

 1920. 



KEY TO subfamilies OF MERMITIDAE 



1. (2) Musculature weak; head papillae feebly developed; 



amphids obliterated; body soft; adult stage par- 

 asitic in midges, Sciara spp Tetradonematinae 



2. (i) Musculature, head papillae and amphids well devel- 



oped; adult stage free-living Mermitinae 



The writer agrees with Steiner (1917) who considers the Mer- 

 mitidae as descendants of the Dorylaimidae. The most suggestive 

 evidences, as expressly pointed out by him, are the presence of a ty- 

 lencholaimoid spear in the larvae and the resemblance in the struc- 

 ture of the esophagus. Some other hints in the same direction are 

 to be seen in the structure of the adults. On the head (fig. 26) one 

 can clearly see the pocketlike amphid common to these forms and to 

 the other members of the Enoplata, and absent in any other nema- 

 tode group. The tail of the male (fig. 25) with its numerous pre- 

 anal papillae is also similar in a general way to that of the Dory- 

 laimidae. 



There are two different groups in the family. The Tetradonema- 

 tinae are parasitic until the end of their life ; therefore the cuticle of 

 the body becomes soft, and the musculature and cephalic sense 

 organs reduced. Nevertheless they can be compared with the Mer- 

 mitidae because of their elongated body, general appearance of the 

 longitudinal chords, and especially because of their esophagus, the 

 "tetrads "of which can be compared with the large esophageal cells 

 of the true mermitids. 



