(if tlic (l()is;il <'s(ipli;i|;cal kIhiuI. 'PIic iiiitoiior ladiiils ( Ki|{. 

 si I ill this r.isi' .iri' idcutcil in tlir i cntfr of tlii'ir soctois, ill 

 two groups of tliri'i', the reiiiiiiiiiiiK r;nlial k'"'M"' "^ "'c fofpus 

 arc tiroki'ii, i. i'., I'lii-h group of six is siilidiviiit'd into two 

 groups of thri'o, ono in earh srctor am! those nuch'i iiiav or inav 

 not heeonie eentrallv loeated aceoriliiig to the |)artieiilar genus. 

 Members of the Asearididai' liave only three esopliageal ghinil 

 nuelei and for that reason .Iscdiiilia, witli liiiitieleate sutiveii 

 tral ghinds, though the esolihagus is eylindrieal, must lie jilaeed 

 in the Ueterakidae. 



Whether or not thi' esophagus retains its gross separation 

 into corpus and Inilliar regions in the adult, the two regions 

 are histologieally separable the base of the corpus being in 

 dicated liy the basal eoinniissure of the nietaeoriius. In aseari- 

 diiis the esojihageal glands undergo many peculiar modifications 

 (see llsii, llfji', lil.'i.S^. The dorsal gland situated near the 

 base of the bulbar region is bilobed in .l.wvin.v liniiliricoidcii 

 the lobes are marginal and connected by a fine strand. In 

 this form lobes of tin' liorsal gl.'ind I'xtend int<i tin' siibventral 

 sectors of the corpus giving the appi'arance of fusion of tis- 

 sues. However, in such forms the subventral glainls do not 

 e.\tend into the anterior part of the esoph;igus. .\ccording to 

 H.sii, 193.^, the dorsal gl.ind nucleus completely surrounds the 

 esophageal lumen in .inisal'is and becomes ventrall.v situated 

 in Toxocara and Conlracaicam. Thus, though the ventrally 

 situated bulbar apjiendage in Contrncdcfiiiii rejiresents the two 

 subventral sectors of the esophagus and may or may not contain 

 small lobes of the subventral esophageal glainls, it is cliietly 

 formed }ty the much enlarged d<irs;il glanil (Pig. 7<i\ 



have arisen. There are two superfaniilics, raniallanoidea and 

 Draeunculoidea, the forinei being char;icteri/,ed by ndatively 

 well develoi>ed musculature usn.'illy having ciiticular attadi 

 Mient jioints for the radial muscles ami an esophago-intestinal 

 valve that is either Iriradiate or shows reminiscences of this 

 condition, while the latter group has enonnoiisly developed 

 esojihageal glands, relatively meager musculature in the glandu- 

 lar ri'gion, no atlaclinient jioints and a dorso vent rally llattened 

 esoph:i go-intestinal \al\'t'. 



Ksophagi of Caniallanoids have b('en studied by .Jiigerskiold 

 (litOin, Magath (Ull!!), Tornquist (l!i:tl), andll.sii (lit33). 

 ('tiiiKillunns iiiicroci phaliix has a so called "divided" esophagus 

 ( i'igs. 7fi & !t8 K-F). Here the dorsal gland orifice is some- 

 what posterior to the base of the stoma, the subventral gland ori- 

 fices at the .'interior end of the posterior part of the esoiihagus. 

 In the anterior part of the esojihagus there are IH radial nuelei 

 anil six marginal nuclei, the railials in four groups, two groups 

 of three anterior to the dorsal gland orifice and two groups of 

 six jiosterior to this level; the marginals are in two groups, 

 one situated near the level of the dorsal ghind orifice, the other 

 between the third and fourth radial grouiis. In the iiosterior 

 part of the esophagus there are likewise IH radials in four 

 groups and six marginals in two groups. Here the first group 

 of six radials is situated near the anterior end of this jiart 

 of the esoiihagus at the level of the subventral gland orifices, 

 the second group of six radials somewhat anterior to the mid 

 region of this part, and the third and fourth groups of three 

 radials near the ba.se of the esophiigus. One marginal group 

 is .lust posterior to the level of the siilt\t'iitral gland orifices 



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Spirurid.\. — The essentially different funn nt' the esopha 

 gus in the order Spirurida has tieen previously mentioned. The 

 fact that the esophagus is always histologically divisible into 

 a short muscular anterior part and a long glandular posterior 

 part is not of cour.se, noticeable in many forms with cylindroid 

 or even elavate esophagi. However, the fundamental signifi- 

 cance of this type of organization is evidenced by the absence 

 of any stages in the life history showing reminiscences of the 

 rhabditoid esophagus such as were mentioned for the Strongy 

 lina and Ascaridina. 



(■.\.\I.VLr,.\yix.\. — The sulionler Cainallaniiia i-oiitnins forms 

 in which the esophageal glands are primarily uninucleate; 

 secondarily a few forms with iiiultiniii'lente glands appear to 



while the other is near the level of the third group of radials. 

 It would appear obvious from the nuclear distribution (Fig. 

 ■SI) that the posterior or glandular region corresponds not 

 only to the bulbar region of Jfliahihlis or Ascari.i but also to 

 the metacorpus of Ulitihditis and part of the metacorpus region 

 of Axcari.i, since the bulbar region in these forms contains 

 only six marginal and 12 radial nuclei while the posterior part 

 of C(imtill(inu.i contains IS radial and six marginal nuclei. 

 This view is supported by the fact that the commissure of the 

 metacorpus is situated in the anterior part of the gl.-indular 

 region of the esophagus of Ciimnlliniiis. 



In ('iiciillaniix though the esophagus is davate instead of 

 being divided (Fig. 7<i) we observed essentially the same 



81 



