(Mononchus gerhichei). Monanchiis tiinhridgcnsis has all of the 

 family ehaiacteristics except that the stoma is of moderate 

 length and cylindioid. Such a form would be the presumptive 

 ancestor of the family. 



In the Tripylidae, onchia, if present, are basal. The weakly 

 sclerotized protorhabdions may be many .jointed {Trilobus 

 longus), or not .iointed (Prismatolaimiis intermedius). The 

 stoma may be subcylindrical (Prismatolaimiis), conoid (Trilo- 

 bus) or collapsed (Tripyla). Dorsal or subventral asymmetri- 

 cally placed denticles are sometimes present. 



In the Ironidae the long subcylindrical to prismoidal stoma 

 is always surrounded by esophageal tissue and sometimes set 

 off as a stomatal swelling (Irnnella prismatolaima) . Except 

 in Cryptonchiis the cheilorhabdions take the form of outwardly 

 acting odontia (fossores). In Iro7ius ignaviis the dorsal odon- 

 tium is double and the subventrals simple while in Ironella 

 prixmatdlaima the reverse is the case. SyringDlaimiis smargidiis 

 and DolicliolainiKS obtiisiis have three double equal odontia. 



Enoploidca (Fig. 63). The families Oncholaimidae and 

 Enoplidae are separable through the fact that only the sto- 

 matal base is surrounded b.v esophageal tissue in the Oncholai- 

 midae while the mesostom and often the prostom is surrounded 

 by muscular esophageal tissue in the Enoplidae. 



In the Oncholaiminae the stoma is typically capacious to 

 subglobular, and armed with three unequal conoid mesosto- 

 matal onchia which act as orifices of the eso]ihageal glands. 

 One of the subventral onchia usually being the largest (Mc- 

 foncholaimvs prislivnis). Sometimes the onchia are multiple 

 (Polydont IIS mariniis) and sometimes there is but one, the large 

 subventral ( OncholaimeHiis clavndisciis). A small residue of 

 more primitive species with cylindroid stoma persist as in so 

 many other groups (Pseiidopelagonema elegans, Anoplostoma 

 vivipanim). 



The subfamilies Eurystomininae and Enchelidiinae appear 

 as slightly modified oncholaims. The stoma is more elongate, 

 the stomatorhabdions are usually .jointed and the onchia at- 

 tenuated to a needle-like point. In these groups one subventral 

 onchium is highly developed while the other two are minute if 



present (Bolbdla lenuidcns). In addition the cheilorhabdions 

 or prorhabdions may bear minute denticles (Evrystomina 

 americana). Sexual dimorphism in stoniata makes its ajipear- 

 ance in enchelidiids in a most surjirising manner. The adult 

 male has a completely rudimentary stoma while the female has 

 a highly developed stoma (Enchclidiiim paiiU). 



In the Enoplidae .stomata are definitely on the wane, being 

 rudimentary in the Oxystomininae and Phanodermatinac, rep- 

 resented chiefly by three mandibles in Enoplinae and usually 

 quite inconspicuous in the Leptosomatinae. In both, EnopUis 

 communis and EnopUndcs amphioxi, the mandibles are the only 

 sclerotized parts of the esophageal lining; these latter are an- 

 teriorly bifid and axially hooked. At their bases one finds the 

 three esophageal gland orifices. In some enoplids it is said that 

 small onchia corresponding to those of ilctoncholaimiix arc 

 present at the base of the mandibles. 



In Bhabdodi' mania minima (Leptosomatinae) we have an 

 example showing the maximum of stomatal development in the 

 Enoplidae; the protosom is wide, the mesostom conoidal, the 

 walls are moderately .sclerotized. Three mesostomatal onchia 

 are present. In other leptosomatids such as Anticoma litnris 

 and Pscudocclla sp. the stoma is completely collapsed and on- 

 cilia, if present, are minute. 



1)0RYL.\IMIN'.\. The suborder is characterized by the pres- 

 ence of a protrusible onehiostyl at least in the larval stages. 

 It now seems that this structure persists to the adult stage 

 in many forms in which its presence is not suspected. The 

 group also differs from the Enoplina in that the esophageal 

 glands never empt.v into the stoma or rudiment thereof. 



Dorylaimoidca (Fig. 64). Oncliiostyls are always well de- 

 veloped and a conspicuous feature of adult dorylaimoids. Ac- 

 cording to the observations of Thome (1930, 1935) the onehio- 

 styl originates as a subventral tooth such as one notes in 

 Xygolaimus brachyuris or Sectonema rentralis. Such an onehio- 

 styl is described as mural. Further development of a ventral 

 groove finally results in a hollow cylinder through which food 

 passes (Dorylaimus siagnalis, Actinolaimus sp.) in which 

 case the stylet is a.rial. Evidence of its original formation is 



Cephalic regions in the Dorylainiina ami 'J'o;;'"l'l'>'"^- 

 tina A-D F & R— Dorylaimidae. K, H-I— Diphlhero- 



K-L N Q— Mermithidae. O— Trichinellidae. P— Trithuri- 

 dae' A— Don/la im II « stagnalw: B— SfOlo/wmd vnitraltt: 

 V^Slliinliiiiiiiii hnivhlliirlH; V>—Aeti,u,Uiiiiiu« sp ; y.—Diph- 

 Iherovhora perplexanti (dorKal on riRht Bide) ; V—Tvlenchn- 

 UimMH aequalis (median view) ; C — Kustroupylides iffrwttui. 

 H—Trichndnrun <ih(iM»»; l—Diptilherophnra commvnw; 

 J — T^eplonchim ijrnnulnsun ; K — Einiirrwm hrhmngi: L, 

 MfnomrnniK biirKnIn; M—Dioclophumi< rrimle (1st stage 

 larva)- N — Mermis mhniiireiieenti (1st stage larva): <)— 

 Trichinelln i>pirnli« (1st staEe larva); V—Tru-hosommdei- 

 eratmeauda (Ist stage larva); Q— Hf.rni;if rmw nlhiran« ; 



H — Xiphinenia aiiifricnnuni. A — After Tliiirm- & Swanger, 

 1936, Capita Zool., v. 6 (4). B-C — After Tliorne. 1930, J. 

 Agric. Res., v. 41 (6). E & H — After Cobli, 1H13, J. 

 Wash. Acad. Sc, v. 3. F— After Colib, IHIH, U. .S. D. A.. 

 B. P. I., Agric. Tech. Circ. 1. I — After de Man. 1884, 

 Die frei in der reinen Erde . . . Nematoden. J — After 

 fobh, 1920, ('(intrih. Sc. Nemnt. 9. K-L — After St*iner, 

 1929, Znnl. Jahrh. Atit. Syst., v. ^7. M — After Lukasiak. 

 1930 Arch. Biol. .Snc.^ Sc. & I>ettres Varsovie. v. 3 (3). 

 N — After Cohh, 1920, ,T. Parnsit.. v. i;i. O-P — After Fuel- 

 lehorn, 1923, Arch. Schiffs. & Tropenhyg., v. 27. Q— After 

 Rauther. 1906. Zool. .lahrb. Aht. Anat.. v. 23, Remainder 

 original. 



