Spiral or triiiisvcrse riiKos'tics of tho protostoni are eoiifinod 

 to tlio sulifaiiiily Ascanipsinae. Similar runiisitios aro known 

 only in tin' k''""" I'li<iiiiii<iii.Kln>iiii!ihi.i <if tlii' StronKylidao. 

 Basal oncliia (lanrcts) an- known only in l!icliihiii<i, prcsint 

 ing rcniarkalili' (■onvi'r>;cni'i' witli tlic Stroncyliilai'. Careful 

 coi:siili'ration of tlu' stoniatal formation in tlii'la/.iiils is essential 

 to an umierstanilinK of the stomata of other spiruroiils. The 

 larva of PhuxoccphalKs has six prostomatal oneliia and no lips 

 like the adult . I xcd ro/>s. Durinp later development the cireu 

 moral membrane is apparently lost at the same time the prostom 

 is everteil. This results in the six prostomatal teeth cominK to 

 occupy an external position and they form the basis of two 

 lateral trilobed pseudolabia. The writers interpret the stomata 

 of other families of spiruroiils as of this everted type. Later 

 ilevelopmeuts of the prorhabdions ( pseudolabia) have been 

 discussed with other labial structures. 



Members of the Spiruridae tend to have a rather wide, 

 cylindrical well scleroti/.ed nu'sostoui which may beconu' lateral 

 ly flattened in sonu" genera (Spinim, Proto.vpinira) but ex- 

 treme development of i)seudolabia and interlabia may obscure 

 the stoma {Ti-lramrrcs male and Uedniri.i). Acuariids are 

 rather uniform in the possession of a long narrow cylindrical 

 niesostoni. 



Passing to the (Jnathostomafidae and I'hysalopteridae we 

 see the first and only tendency toward vestibule formation in 

 the Spirnroidea. The genera Spiroj-i/s and Harlcrtia (Gnathos- 

 tomatiilae) are the only representatives which retain a sclero- 

 tizeil mesost(]m and in these forms the stonui is much short- 

 ened and surrounded by esojihageal tissue. Thnhunavii (Physa- 

 lopteridael retains a laterally compressed vestibule while 

 Physahipti ra. Abbrtviata, Skrjabinoptcra (Physalopteridae\ 

 TaiKjuii and dnathdstoma (Gnatliostomatidae) have completely 

 rudimentary stomata, the esophageal tissue proceeding unin- 

 terrupted to the base of the pseudolabia. At the anterior end, 

 in such forms, the esophageal lumen becomes dorsoventral be- 

 fore connecting with the labial bases. 



The Filarioidea (Fig. .19) might be considered the "astoma- 

 tous" twin of the Spiruroidea. A few genera, however, are 

 known to have rather distinct, sclerotized stomata. It is in- 

 teresting to note that such forms are not dissimilar to thela- 

 ziids. Drstnidoccrca is a striking counterpart for it not only 

 has a cylindrical stoma but also a pair of lateral prostomatal 

 onchia which may be homologous to those of the spiruroids. 

 Litnmosn has a short stoma practically identical with that of 

 Thclazia while LHomosoides has a cylindrical stoma with 

 separate distinct stomato-rhabdions. Even in such forms as 

 Dirofilaria immitis one must assume a cylindrical stoma in the 

 not too dim ancestry because such a stoma, although weakly 

 sclerotized, is present in the third stage larva. 



P.. APHASMIDIA 



As in the Phasmidia, stoniatal morphology in the Aiihasmidia 

 is of no value as an ordinal character. Forms with a rudimen- 

 tary stoma occur in each large group and in man3- of the 

 groups series extend from the cylindroid type, through various 

 modifications ending in instances of convergence. 



II0XHY.STERIXA. Members of the Monhysterina (Fig. 60) 

 have one character in common and opposed to the related 

 rhromadorina, namely, that the chcilorhabdions do not take 

 the form of twelve sclerotized longitudinal ridges, (odontia), 

 replacing lips. However, in axonolaimids and monhysterids one 

 may sometimes note a longituilinal sclerotization which is ap- 

 parently the homologue, or even predecessor of the chromado- 

 roid type. 



Plecliiiiira. AnapUctu.i (ininiijosii.t provides us with the 

 aphasmidian version of Rliabililis not only in esophagus and 

 lips but also in the stoma. The cheilostom is hexangular, the 

 proto-stom, subtriangular in cross section, f'heilorhabdions and 

 protorhabdions are well sclerotized, telorhabdions only faintly 

 sclerotized. Anaplcclus is unusual in that the protostoni has 

 parallel walls; in most plectoids the walls converge posteriorly. 

 In Leptdlaimiix mnrimiis the stoma is extremely long and nar- 

 row, protorhabdions distinct while in some related forms the 

 stoma collai)ses forming a greatly elongate vestibule. AiioncJiii/i 

 viirabilix and Trrdtiici phnhix rorniiliis exemplify shortening 

 and dilation of the stoma with distinct .ioints at .iunction of 

 pro- and nicsorhabdions. In Trrntocrphaliis the i)rotorhabdions 

 are further modified taking the form of six inwardly acting 

 teeth or odontia. 



The family Camacolainiidae is characterized by a diminu 

 tion in stomata in all forms. In AphaiKihiiiiiiix aqiuiliriix the 

 stoma is minute, cylindroid, with practically non-sderotized 

 protorh.'ibdions while in Camacnlaimiin pruHicrchi only the dor- 

 sal stomatal wall is sclerotized and it projects anteriorly as an 

 onchium. An-ffuinftidrs stffhisiini is a further examjile of the 



same tendency, in this instance the dorsal onchium is .separate 

 thrcnighout its length teriiiinatiKi; i)osteriorly in two knobs. 

 Ani/iiiiiiiiih .1 is a striking paralhd to Dilj/linchuii dipnuci of the 

 Tylenchoidea but we must classify the spear as an onchiostyl 

 in this instance. 



Passing to the liastianiidae, we may .judge that the "asto- 

 matous" Hiixliania arose from some such form as Oilonlnhtinuis 

 whi(h has a greatly elongate, narrow stoma. 



Concluding our resume of the Plectoidea we note that non 

 muscul.'ir esophageal tissue extends beyond the mesorhabdions 

 in such members of the genera AnnpU ctus and Pled us as have 

 been studied. Comparing with lOinlnlilin, we would consider 

 this as a more advanced evolution.iry devidopinent. Such a 

 view is borne out by the somatic musculature of the forms 

 studied. Since there are representatives in the Plectoidea 

 { Animrhiis), .Axonolaimoidea I Axandldimux) and Monhysteroi 

 (lea (Ualaniinchus) in which esophageal tissue does not exteiul 

 anteriad, we must conclude Ana phcl 11,1 while i>rimitive, does 

 not fulfill all oblig;ifions of the Aph:ismidian ancestor. Com- 

 bining cephalic characters and general stomatal outline of 

 Anaplecliis with the more primitive stomatal and somatic mus- 

 cle characteristics of Ananchns we may, perhaps, have the 

 proper picture. 



Axoni)luiiiiiiiiha. Primarily axonolaimoids have a cylindroid 

 or conoid i)rotostoni. In the .Vxoncilaiminae the protostoni is 

 conoid, the nu'sostom surrounded by esophageal tissue; the chei- 

 lostom is anteriorly conoid. Thus in Axonolaimus we have a 

 close parallel with PIrctiis. Twelve weak longitudinal .sclero- 

 tizafions of the cheilostom are usually evident in Axoiuihiiiiiiis 

 species. In Oddnloplmni iinpiisiddimo these 12 .sclerotizations 

 arc anteriorly fused forming six large outwardly acting odon- 

 tia. As we shall later see in dealing with the Chromadorina, 

 the 12 odontia replacing lips in that group probably originated 

 in a form near AxonoUiimiix. The same tendency of the chcilo- 

 rhabdions, with multiplication of elements may be seen in the 

 Monhysteroidea. 



Inconspicuous, weakly sclerotized, cylindroid stomata occur 

 in the subfamily Cylindrolaiminae which includes forms in 

 which esophageal tissue extends to the anterior end of the 

 protostoni {Aracolaimns zostcrar) and forms in which this is 

 not the case (Ci/liii-droUiiinus comiiiiini.s. Aii/ialiHilaiiinis tie- 

 (jans). Cylindroid or collapsed stomata occur in representatives 

 of the Campylaiminae (Pxeiidohlhi iirantilifrra) and Biplopel- 

 tinae (Didelta maculata). In the former type the protorhab- 

 dions terminate anteriorly in three small teeth, a parallel to 

 Dori/laimopsis. 



The Comesomatidae have stomata of two general types. In 

 the first the stoma is cylindroid, the protorhabdions are well de- 

 veloped and terminated anteriorly by three equal teeth (Dory- 

 laimopsis mctatypiciix and Laimella iiiindrisetosa) ; the entire 

 protostoni is surrounded by esophageal tissue. In the second, 

 the protostoni is collapsed, the rhalidions are non-sclerotized, 

 the esophageal tissue transforms the stomatal region to a 

 vestibule (Sabalieria lon<iicaiidata, Comesoma minimum). In 

 both instances the chcilorhabdions are short and do not con- 

 verge anteriorly as in AxnnotaimiiK. 



Monhysteroidea. Stomatal diversity in this superfamily has 

 thus far prevented adequate revision of the group into com- 

 pact small units. In the ina.iority of instances, when the stoma- 

 torhabdions are well sclerotized esophageal tissue does not sur- 

 round them (except Tripj/Uum carcinicohim). We may presume 

 that when the .stoma is rudimentary as in Theri.itti.^ or Ci/tn- 

 laimium, it reached this condition through shortening rather 

 than vestibule formation and collajisc. A few forms with a 

 large consjiicuous stoma arc retained in this group; such are 

 Bhynchdncma cinctum with an extremely long cylindrical sto- 

 ma, Halandnfhns macramphidum, Omieronema Utorium and 

 Sphaerolaimiis sp, with wide, heavily .sclerotized stomata. In 

 Spliaerolaimus the chcilorhabdions consist of innumerable scler- 

 otized rugae. These same rugae are retained though the pro- 

 tostom has disappeared in Theri.'ttu.s .ictosit.i, Stcineria sp. and 

 other typical monhysterids. In Seaptrella cincta. on the con- 

 trary, one finds the cheilorhabdions transformed into six out- 

 wardly acting odontia .-is in Odontdplioni of the .\xonolaimoiilea. 

 Many linhomoeids {.Tersrlielliti/jia punticn. Mnnhyxleriiim Iran- 

 .litan.'i) have no distinctly sclerotized rliabdioiis and in the re- 

 mainder one notes degrees in shortening and reduction. Thus 

 in I.inhomoeii.i elnnt/atii.i and Ilalinrma .'ipinosiim the entire 

 stoma is short and wide. In the former one notes subequal 

 cheilorhabdions and |)rorhabdions with posteriorly converging 

 nu'sorhabdions. Paralinliiimneiis Jeptiiriis and Metalinhomneiifi 

 typicu.i seem to be further steps in stoniatal reduction of this 

 series. 



Siphonolaims are ;i group apart, having the entire protostoni 

 transformed into a stomiitosfyl as in the Tylenchoidea but there 

 is little or no resemblance in the org.'in itself. 



<V.< 



