240 APPENDIX TO NEMATODA 



Appendix to Nematoda. 



A. Earn. DRILONEMIDAE Pierantoni, 1910. 



We place here five aberrant and little-known genera parasitic 

 in Earthworms, whose organization is so modified that their 

 position in the system is very uncertain. They have been 

 made into three separate families — Onycidae, Cephalonemidae 

 and Drilonemidae — by Pierantoni, but several of the genera 

 appear to be based on unsatisfactory characters, and we regard 

 them as synonyms. All the remaining genera seem to us to 

 have certain characters in common, and it ajjpears possible 

 to regard them as aU belonging to a single family, for which 

 Pierantoni 's name Drilonemidae may be retained. 



The family may be defined as foUows : — Small forms with 

 or without a pair of chitinoid hooks overhanging the mouth. 

 Oesophagus short and simple, or absent. Male with two 

 spicules and an accessory j^iece, or without any such organs. 

 Female genital tube single, running anteriorly from the vulva, 

 then turning posteriorly and extending to the hinder part of 

 the body. Oviparous. Parasitic in the coelomic cavity or 

 musculature of Earthworms. 



1. Drilonema Pierantoni, 1916. 



Syn. Mesonema Pierantoni, 1916 ; Opistonema Pierantoni, 

 1916. 



Head narrower than neck. Mouth unarmed, terminal. 

 Oesophagus short, cylindrical or slightly club-shaped, appar- 

 ently muscular, followed by a much wider intestine. Male 

 much smaller than female, with a blunt tail which may be 

 of great relative length. Spicules absent. Testis reflexed. 

 Vulva in front of or behind the middle of the body. 



Hab. Free in coelomic cavity of Earthworms. 

 Genotype : D. ivendessiamim Pierantoni, 1916. 



Pierantoni, 1916, Boll. Soc. Nat. Napoli, xxviii, 152, 154, 

 155. 



The generic separation of Meso7iema and Opistonetna from 

 Drilonema does not appear to be justifiable. Mesonema 

 includes, according to Pierantoni, two species of which the 

 males are unknown, and the females difi:er from those of the 

 species of Drilonema almost solely in having the vulva situated 

 somewhat further back. In the three sijecies of Opistonema 

 the vulva is still further back, but there appears to be no other 

 ground for the erection of a separate genus. 



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