(Ic) The elongate, vesicular terminal duct is another 

 modification of type la; it is confined, so far as known, 

 to the Kathlaniidae occurring in such forms as Spironoura 

 ttffine and Cissophylus roseus. Whether or not it is a 

 character of the entire family is not known. As Mackin 

 (1936) observed, the anterior and posterior canals unite 

 with their mates and empty into a great elongate sinus 

 which separates anterior and posterior canals (Fig. 

 112 D). This is distinctly different from other forms 

 in which the two anterior and two posterior canals all 

 come together at practically the same level. Apparently 

 this sinus combines the functions of terminal duct and 

 sinus since there is a delicate cuticular ventral lining- 

 connected with the excretory pore; thus we might say 

 the dorsal side is sinus and the ventral side is terminal 

 duct. The excretory pore is at the anterior end of the 

 excretory region (Fig. 113 NN) and near this regijn 

 two small subventral nuclei are present; these we attribute 

 to the terminal duct. The dorsal side of the sinus 

 contains three equal, rather large nuclei (Fig. 113 MM). 

 The tissue in which they are situated is continuous wi h 

 the tissue of the lateral canals and in the latter ko 

 nuclei have been observed. On the basis of present 

 information the Spironoura system contains five nucki, 

 three belonging to the canal system (sinus) and two tj 

 the duct. 



(Id) The typical oxyurid excretory system is a notable 

 feature in most representatives of the Oxyuridae, Thelas- 

 tomatidae, and Atractidae. Due to the clarity of the 

 oxyurid body and to the rather large diameter of the 

 lateral canals, this form has become synonymous in thv? 

 literature with the H system even though it is but one 

 variant. 



Leidy (1853), Eberth (1863), Schneider (1866), Biitschli 

 (1871), Cobb (1890), Martini (1916), Rauther (1918), 

 Thapar (1925), Chitwood (1931) and Chitwood and 

 Chitwood (1933) have studied the system as seen in 

 Thebistoma, Passalurus, O.vyuris (sensu lato), Leidynema 

 and Hammerschmidtiella, Enterobius vermicularis, Ox- 

 yiiris equi, Mucracis monhyslera and Thelandros alatiis, 

 various reptilian oxyurids (Pharyngodoninae), Hystrig- 

 nathus and Macracis, and Cephalobellits respectively. Sub- 

 sequently extension of observations has shown the system 

 to be practically universal in the families mentioned. 

 The four lateral canals come together at about the 

 same level forming, with the sinus, an X (Fig. 112 C). 

 The sinus nucleus may be medial as in Hy'^trigiiathus 

 and Macracis or on the left side as in Cephalohellus; it is 

 not proportionately very large. Chitwood (1931) de- 

 scribed regularly arranged nuclei in the lateral canals of 

 Macracis monhystera (Fig. 113 FF-GG). In other forms 

 no such nuclei appear to be present. Constancy and 

 recognition of the sinus nucleus in Macracis argue against 

 the concept that the canal nuclei are derivatives of the 

 sinus nucleus. 



The excretory vesicle, bladder or reservoir is a most 

 interesting structure showing considerable variety in 

 oxyuroids. As in types lb and Ic the terminal duct is 

 in open connection with the excretory sinus (Fig. 113 V, 

 Cephalohellus), its cuticular lining forming the ventral 

 part of the sinus wall. As observed by Rauther (1918) 

 in Macracis, the terminal duct wall contains two nuclei 

 or is composed of two cells, these cells may both be 

 situated anterior to the excretory pore or one may be 



anterior and one posterior. The conspicuous rounded 

 vesicle seen in totomounts is apparently not a storage 

 structure (see figs. 113 BB-OC) but more on the order 

 of a valve; i. e., the sinus cavity functions as the reservoir 

 while the terminal duct is shortened. Sometimes (Fig. 

 113 Y-Z) there is a distinct circular sphincter muscle 

 near the junction of sinus and duct. In representatives 

 of the Atractidae the wall of the terminal duct is radially 

 striated from the excretoi'y pore giving the appearance of 

 a sucker. 



Martini (1916) saw structures which he considered 

 might be rudimentary cilia near the blind ends of the 

 excretoi-y canals of O.vyuris equi. The writers have not 

 observed such structures in the species studied. 



(2) The Rhabditoid System (Fig. 112 I). The €s.^en- 

 tiai features of this system include (a) a terminal 

 elongate cuticular duct, (b) an excretory sinus connected 

 with paired lateral canals, and (c) paired subventral 

 excretory glands also connected with the excretory sinus. 



Mehlis (1831) supposedly observed the subventral 

 glands (strand-like organs) in strongyles and thought 

 they opened anteriorly as salivary glands. He may 

 have confused the subventral excretory glands (coi'vical 

 glands of Looss) with the amphidial glands (cephalic 

 glands of Looss, fig. 12 G-I). In 1841 von Siebold observed 

 the pore and vessels in Osicaldocruzia (Strongylus auricu.- 

 laris) and shortly thereafter Dubini (1843) associated 

 the subventral glands of Ancylostoma duodenale with 

 the esophagus and Bilharz (1852) observed the junction 

 of subventral glands and excretory pore but did not see 

 the lateral vessels. It was Schneider (1858-1866) wlio 

 first observed the full gross morphology of the system 

 by noting all three of the essential components (see 

 above) and by joining them. However, he erred in one 

 respect, by considering the gland cells as non-glandular 

 attachments of the sinus (or bridge). Schneider's ob- 

 servations were made in reference to Rhabditis strongy- 

 loides (Fig. 112 I), Cylicostormim tetracanthum, Strongy- 

 lus armafus and other strongyloids. Biitschli (1873) 

 found Rhabditis terricola to have the same type of ex- 

 cretory system as that described by Schneider for R. 

 strongyhides. Leuckart (1876) did the same in i-egard 

 to Ancylostoma duodenale. Since that time papers dealing 

 with the excretory system as seen in rhabditids and 

 strongylins have been published by Rzewuski (1887), 

 Metastrongylus elongatus; Stadelmann (1891), Ostertagia 

 ostertagi; Augstein (1894), Dictyocaulus filaria; Looss 

 (1895), Trichostrongylus colubriformis; Poeppel (1897), 

 Strongylus vulgaris; Looss (1905), Ancylostoma duo- 

 denale; Maupas (1916), Rhahdias spp.; Cobb (1925), R. 

 icosiensis; Aubertot (1926), R. pellio; Stekhoven (1926), 

 Ancylostoma and Necafor; Chitwood (1930, 1931), Rhab- 

 ditis spp., and Oesophagostonmm dentatum; Eisma (1932), 

 Ancylostoma; and Raven and Stekhoven, (1934), 

 Rhabditis spp.* 



*As already noted, the "rhabditoid" excretory system does not 

 occur in all rhabditoids, but is merely characteristic of a liiDitcd 

 group centered around Rliabilitis strongyloides. The majority of 

 rhabditoids. including RhahiUtis doUvhuro and other RJuibditis sen:iu 

 lato have an H-shaped (o.xyuroid) system. Raven and Steithoven 

 (1934) denied the existence of lateral canals in RhabfUtella oxei, 

 but the writers have re-examined this species and can confirm 

 the previous observation of Chitwood (19.30) that the system in 

 this form Is of the "rhabditoid" type — an H system with distinct 

 sinus nucleus and two subventral glands 



Fig. 113. 



A — Rhabditis sergenti (Female with both ordinary and auxiliary 

 excretory systems shown in outline) ; C — Rhabditis seurati (Female 

 excretory systems shown in outline) ; B, D, S E^Rhabditis icosiensis 

 (B — Posterior part of female showing auxiliary excretory system- 

 D — Terminal duct of auxiliary system : E — Blind end of auxiliary 

 system, all drawings semi-diagrammatic) ; F — Rhabditis courrtata 

 (Auxiliary canal, regions drawn camera lucida from living speci- 

 men ; the large nucleus could not be seen in the canal on the opposite 

 side and it may not actually be within the duct wall) ; G — Rhabditis 

 terricola (Blind end of auxiliary canal as seen in living specimen i ; 

 H — Ditylenchus dipsaci (Cross section showing sinus nucleus iii 

 lateral chord) ; I-P — Oesophagostomum dentatum, cross sections 

 (I — Near base of esophagus showing subventral glands, lateral 

 canals, and amphidial glands ; J — Subventral gland at level of 



nucleus; K — Terminal duct at excretory pore; 1^ Sinus with its 



nucleus ; M-0 — Approach and fusion of lateral and transverse 

 canals ; P — Lateral chord with lateral canal in mid-region of 

 body) ; Q — Metastrongylus elongatus (Cross section at level of 

 sinus, with its nucleus and connection with subventral glands) • 

 R-S — Strongylus eguinus (R — Cross section of laleral chord in 

 posterior region of female showing two lateral canals, one in 

 cross section, the otlier longitudinal ; S — Cross section of lateral 

 canals about to fuse in preanal region of male ; note round body 

 which stained like a nucleus) ; T — Bictularia colorudiensis (Terminal 



duct at level of nucleus) ; U-V — Cephalobellus papilliger (V- — ■ 

 Excretory sinus ; V — sagittal section through terminal duct),: ^W-AA — 

 Hystrignathus rigidus (W-Z — Serial sections through terminal duct 

 and sinus ; AA — Cross section of another specimen at same level 

 as that shown in W) ; BB-GG — Macracis monhystera (BB — Longi- 

 tudinal section through terminal duct ; CC — Cross section through 

 excretory sinus ; DD — Cross section of entire specimen at level 

 of t'C ; FF — Lateral canal in chord showing nucleus in its wall ; 

 GO — Same as FF. seen in longitudinal sectiou) ; HH — f'ucullanus 

 serratus (Lateral canal showing bacillary layer or possible cilia) ; 

 II-LL & RR — Heterakis gallinae (II — Terminal duct; .IJ — Second 

 terminal duct nucleus, at level of sinus ; KK — Sinus w-ith possible 

 constrictor nucleus; LL — Sinus nucleus; RR — Terminal duct with 

 first terminal duct nucleus); MM-XN — Spironoura affine (MM — 

 Cross section at level of first sinus nucleus; NN — Sagittal section 

 through sinus) ; OO-PP — Goc^ia annulatus (00 — Entire excretory 

 system; PP — Blind end of system) ; QQ — Panagrolaiinus Slibelong- 

 atus (Blind end of lateral canal). A-E, After Maupas, 1916. Compt. 

 Rend. Soc. Biol. v. 79 ; 1-J. After Chitwood. 1931. Ztschr. Morph. 

 v. 23 (Vi); U-V. After Chitw. & Chitw.. 1933, Ztschr. Zellforsch. 

 V. 19 (2) ; HH — After Toernquist, 1931, Goeteborgs Kungl. -Vetensk. 

 o. Vitterhets. Handl. s. B., v. 2 (3) ; OO-PP. After Hamann, 1895, 

 Die Nemathelminthen v. 2. Remainder original. 



128 



