rudimentary or absent, and li! more or less projeetable eheilo 

 stom rugae are present. Cliromadorids differ from micro- 

 laims only in tliat the amjihids are moved anteriad, usually to 

 the level of the cephalic setae, and vary from unispire (OtJon- 

 lijnrma) to reniform (Pn)chniiniiilora) . The C'yatliolaimidae. 

 and Tripyloididae, differ from luicrolaimids aud cliromadorids 

 in having an undivided external circle. In all forms studied 

 by the writers there are four small and six large (dd., el., and 

 vv.) papillae or setae in the external circle. De C'oninck 

 (193.5) characterizes cyatholaimids as having two circles of six 

 papillae and an external circle of ten setae. Since he specifies 

 no form as exemplifying this condition we must judge by our 

 own observations. In some cyatholaimids particularly members 

 of the Choanolaiminae such as HalicJioanolaimiis robtistiis, the 

 fiber trunk of each of the papillae of the internal circle shows 

 in optical cross section much like a papilla but then it bends 

 nearly at right angles over the stomatal cavity before reach- 

 ing the true sensory terminus. Thus, by optical illusion one 

 may see more papillae than exist. Rudimentary lips and 

 heavy stomatal rugosities (usually 12) are conspicuous fea- 

 tures of most members of the Oyatholaimidae (Gammnnema. 

 Ealichrianolaimus, Paracanthotichns and Pomponema) while 

 three well developed lips occur in members of the Tripyloidi- 

 dae. Both circular and unispire amphids are known in these 

 families but multispire are the rule. 



Dcsmodnroulra. Like microlaimids and cliromadorids mem- 

 bers of this superfamily have an internal circle of six papillae 

 and a subdivided external circle of six papillae or short setae 

 and four long setae (laterodorsal and lateroventral). Mono- 

 posUiia hcralata and Spirina parasitifera are typical exam- 

 ples. Somatic setae arc quite apt to become nearly cephalic 

 in position as in Mrtachroinailnra ontjxoidc.t and Croconema 

 mammilla turn but by careful study one can usually segregate 

 the two types. Helmet formation is often a conspicuous des- 

 modoroid feature but this has been previously mentioned with 

 the cuticle. Amphids in desmodoroids are primarily spiral, the 

 unisjiire prevailing {Epsiloncma, Spirina) but closed unispire 

 (Milachromailora oni/jroidcs), circular (Moiwposlliia hcxalata), 

 multi.spire (Richtersia hcauforii) and elongate or shepherd's 

 crook amphids (Ceramnnema) also occur. True lips are rudi- 

 mentary, sometimes indicated by six rudiments and stomatal 

 rugae often replace them but these also disappear with reduc- 

 tion in stoma. 



Desmoscolecoirlca. The amphids of desmoscolecoids are a 

 characteristic feature, usually being described as vesiculate. 

 They are rather bubble like but internally one may distinguish 

 evidences of a unispire character. Due to their small size the 

 head of only one species, Desmnscolex americanus, has been 

 studied en face. In this form there are six minute lips each 

 bearing at least one (?two) papillae. Four large cephalic 

 setae are known in all forms. Thus we may ])resnme a possible 

 desmodoroid relationship. 



Enoplina. Members of the suborder Enoplina may have 

 three, six or no lips, cephalic papillae or cephalic setae, but 

 they are all similar in having cyatliiform amphids. 



Tripyloidea. Included in this group (Fig. 62) are many 

 forms which show relationships to other groups. The Monon 

 chidae, with six lips, an internal circle of six papillae and an 

 external circle of ten papillae, seem clearly related to doiy- 

 laimoids. The family Tripylidae includes closely related forms 

 with diverse symmetry. Tlie genus Tripi/la is characterized by 

 three lips, an internal circle of six papillae and a subdivided 

 external circle of six papillae or short setae and four papillae 

 or long setae (Id. and Iv.). Trilobiis lo7ifiii.i and Prisma! olai- 

 mnx intrrmeiliiis have six small lips (apical lobes), an inter- 

 nal circle of six papillae and an externa! circle of 10 setae, 

 four being short •■md six long (Id., el., and vv.). De Coninck 

 places these forms in the Bastianiidae close to PJcctiis but we 

 cannot agree with this placement on the basis of eso))hageal 

 characters. Undoubtedly the Tri])yloidea is the most primi- 

 tive groujj of the order Enoplida, and hence most closely re- 

 lated to the I'lectoidea but it is customary to i)lace primitive 

 groups with tlie forms that they gave rise to rather than with 

 other primitive groups. 



The family Ironidae includes forms which may {Ironiix. 

 IroneVa) or may not (Crypt onchus') have cephalic setae. If 

 such are present the external circle is subdivided with six 

 anterior papillae or setae and four posterior setae (Id. .-ind 

 Iv.). Lips may be moderately distinct but .are usually rudi- 

 mentary or absent. 



Jinopldidra. With the except ion of the (Jxystomiiiinae the 

 Knoploidea (Fig. tiS ) hold quite closely to a six-ten symmetry 

 with an undivided external circle of which there are four small 

 and six large setae (d<l., el., and vv.). In the single excep- 

 tional group, tlie external circle is subdivided, with six large 



anterior and four large posterior setae (Huhilaiiiiii/i carnlinicn- 

 sis and Oxiisfnmina iiliilia). Lips are seldom well developed in 

 enoploids but one finds three massive apical lobes in E)uyploidcs 

 and Endid-ilnimiis. three small apical lobes in Etuiphis, Jnti- 

 roiiia and Antiplttsioma. Si.x small apical lobes are general in 

 the Oncholaiminae but even such lobes are not apparent in 

 forms such as Bolbilla lenitidens and Enchelidium pauli. 



In most enoploids the amphids are typically cyathiform but 

 in the Oxystomininae they are longitudinally elongate (Oxii- 

 stamina alplia, Halalaimiis caroliniensis). De Coninck (1936) 

 considers the oxystomins related to the genus Aratolaimus 

 and derives the amphids by elongation. This point requires 

 more critical study. If the o.xystomin amphid is a modified 

 spiral, then it must be an open groove while if it is an elon- 

 gate pocket, it is open only at its anterior end. Thus far such 

 information has not been presented. 



DoRYL.\iMiNA. Like the Enoplina, the suliorder Dorylainiina 

 (Fig. 64) is characterized by cyathiform amphids but in para- 

 sitic members of this group the amphids may become externally 

 pore like. The cephalic papillae of dorylaimins, like those of 

 mononchids and phasmidians, never take the form of setae. 



Dorylaimoidca. Members of this group for the most part, 

 have six rather well developed lips; sometimes the lips are 

 set off from the remainder of the body as in mononchs and 

 rhabditids. The full component of cejihalic papillae are recog- 

 nizable, there being an internal circle of six and an external 

 circle of 10. Members of the latter circle are usually of two 

 slightly different sizes and at two different levels on the lips. 

 The large cyathiform amphids are situated just posterior to 

 the labial region. Thorne (193.5) described the amphids of 

 diptherophorids as ere.scentic with reminiscences of spiral fea- 

 tures. 



Mermithoidva. Functional lijis do not occur in mermithoids, 

 the original lips being represented only by fiber tracts of the 

 six papillary groups. These fiber tracts are {Mesomermis 

 bursata, Hoxamermis albicans) usually referred to as "papil- 

 lae" in the literature. Careful study shows each of the four 

 submedian "papillae"' end in three tactile sensory organs 

 (true papillae) while each of the laterals end in two; this 

 corresponds exactly to the normal papillary symmetry with 16 

 papillae. The amphids may be associated with the lateral lip 

 rudiment (Hcxanirrmis albicans) or they may be quite separate 

 from it (Mfsonicris biirsiita). One finds all manner of am- 

 phidial t.ypes from large cyathiform as in Mesomermis to ex- 

 ternally minute pore-like structures as in some Hexamermis. 

 In addition, instances are known in which the amphids are 

 joined dorsally by a fiber tract, a condition particularly com- 

 mon in the genus Pnramertnis. A shift of the oral opening 

 ventrally is not uncommon in mermithoids {Eumermis, Lim- 

 nomermis) and this migration is not accompanied by a shift 

 of cephalic papillae, though the anqiliids may assume a more 

 dorsal position. 



I'richiiroidea. Cephalic papillae and amphids have been stud- 

 ied in only one member of this superfamily, Tricliuris suis. In 

 this instance lips are absent, six papillae and externally pore 

 like amphids were observed. The position of the lateral papil- 

 lae (presumably of the external circle) in a true lateral posi- 

 tion seems distinctly to indicate aphasmidian relationships. 



DIOCTOPHYMATINA. Dioctojihymatoids are well known for 

 their cephalic symmetry or lack of it. Lips are absent in all 

 members of the group. The oral opening in the Pioctophyma- 

 tidae is surroiindeil by a cuticular circumoral membrane while 

 in the Soboliiihyniatidae the body extends anteriad beyond 

 the true oral opening forming an oral sucker. Presence of 

 modified somatic muscle tissue and body cavity in this sucker 

 is distinct evidence that the true oral opening should be re- 

 garded as the base of the sucker cavity; presumably, the 

 cephalic papillae are on its infernal surface. 



"Cephalic jiapillae" are so numerous in members of the 

 Dioctophymatidae (Eustron-gylides ignotus, Dioctophyma re- 

 nale) as to completely confuse one first observing them. The 

 total number and arrangement varies within the species but 

 certain iiaiiillae remain constant (Fig. 64). These latter are 

 the true cephalic papillae; the others are considered as somatic 

 jiaiiillae extending anteriorly from the lateral areas. There 

 is an intern.'il circle of six pajiillae and an external circle of 

 four small (Id. and Iv.) and six large jiapillae (dd., el. and vv.). 

 This symmetry is the same as that to be found in a large part 

 (if the Dorylaiinoidea and Enoploidi'a. If is in definite op- 

 position to fli:if founrl in ]diasmidians such as the Si)iruroidea 

 to which these nomas are sometimes compared. The amphids 

 of dioctophymatids are posterior to the externolateral jiapillae, 

 sometimes ajipearing to be narrow, cyathiform, sometimes 

 l>ore-like. 



64 



