According to our observations this system consists of 

 not less than three, usually four cells in such diverse 

 forms as Rhahditis strongyloides, Oesophago^tomvin 

 dentaticm, KaUeephnlus sp. and Metastrongylus elonr/atus. 

 The terminal duct is narrow, elongate and tubular in 

 adult rhabditids as well as larval strongylins while it 

 becomes folded and thick-walled (Fig. 113 K) in adult, 

 strongylins. Its nucleus lies just posterior to the end 

 of the cuticular lining in these forms and corresponds 

 to the carrying cell of the excretory vesick described by 

 Looss (1905) in Ancylostoma. It has been clearly identi- 

 field in Oesophagostonmm, Metastrongtihis and Strongu- 

 lus. More posteriad, the excretory canal widens into the 

 transverse excretory sinus into which the paired sub- 

 ventral glands open. The excretory sinus contains a 

 large conspicuous nucleus (Fig. 113 L) which may be 

 medial (Rhabditis strongyloides, R. coarctnia. Oisoph- 

 agostomum) or left (Metastrongylus) in position. Thin- 

 walled branching tubules extend posteriorly from the 

 sinus into each of the subventral glands. The lateral 

 canals may connect directly with the excretory sinus as 

 in Rhabditis and Metastrongylus or they may connect 

 indirectly by way of the subventral gland cells as in 

 Oesophaqostomum, Ancylostoma (vide Looss) and 

 Strongylns (vide Schneider's description of double lateral 

 canals). In the latter instance one finds two pairs 

 of lateral canals in each chord extending nearly to the 

 caudal extremity before they unite (Fig. 113 R). In 

 other forms the lateral canals are tubular, delicate and 

 usually extend nearly to the two extremities; often 

 vacuoles may be seen in the wall of living specimens; 

 each canal ends blindly at its terminus, often in a small 

 ampulla. Thus far no one has identified nuclei in the 

 lateral canals but this may be due to lack of critical 

 study. Tn a complete series of cross sections of a male 

 Strongylus the writers observed onlv one possible canal 

 nucleus (Fig. 113 S) which was situated very close to 

 the junction of the canals posteriorly; since it could not 

 be verified in the corresponding canal in the other chord 

 nor in other series, it may easily have been an artifact. 

 Ordinarily the lateral canals in nemas are considered 

 "outgrowths" of the cell which we have hei-ein called 

 the sinus cell. In the organization of Oescphagnstnmum 

 and Strongylus such a relationship is seemingly pre- 

 cluded since the canals do not empty into the sinus 

 directly, but through the subventral glands. One may 

 conceive the Rhabditis strongyloides type (Fig. 112 I) 

 to be most primitive, and transformation to the Strongylus 

 type to have taken place by a posterior shifting of the 

 canal union. In Rhabditis and Strongylus the sinus nu- 

 cleus plus the subventral gland nuclei are therefore to 

 be considered homologous to the sinus nucleus of oxyur- 

 oids and Rhabditis dolichura. 



Maupas (1900) apparently first noted contraction in 

 the lateral canals of Rhabditis biciaiiii and in 1916 the 

 same author noted a contractile ampulla at the end of 

 the terminal excretory duct in R. ierricola. Similar ob- 

 servations were made concerning larvae of R. pellio by 

 Auljcrtot (1926) and Rhabditella nxei by Raven and 

 StekhoVien (1934). The latter authors observed only 

 one gland cell and presumed there would be two am- 

 pullae if there were that many gland cells. This is 

 not necessarily the case. The ampulla corresponds ap- 

 parently to the excretory sinus and may act a^ a central 

 contractile bladder in which the various contents empty. 



Plurality of lateral canals in the lateral chords has 

 been recorded by Schneider (1866), Leuckart (1876), 

 Poeppel (1897) and Looss (1902), the cases referring 

 to strongyloids. Ultimately these canals have always 

 been found to join and not to represent a real duplica- 



tion or branching of the canals. However, in females of 

 some species of rhabditids this is not the case. As first 

 noted by Maupas (1916) there may be an auxiliary 

 excretory system with paired openings dorso- or ventro- 

 laterally posterior to the vulva. Maupas recorded such 

 a system in R. terricola, R. lucianii, R. axei, R. pellio, R. 

 seitrati, R. sergenti and Ayigiostonia Umacis. It was 

 many years before the writers had the pleasure of seeing 

 this system, and then only in Rhabditis terricola, R. 

 coarctafa, R. cylindrica, Rhabditella axei and Rhabditoides 

 paraelongata. It does not seem to be present in R. 

 strongyloides. Whether it may occur abnormally in that 

 species or whether Maupas misidentified his species, we 

 cannot say. The system as seen by us in R. terricola 

 consists of two tubes, one in each lateral chord, connected 

 by a ventrolateral pore near the vulva. The canals ex- 

 tend posteriorly to the caudal region, and are much 

 coiled at the blind end (Fig. 113 F-G.) In R. coarctata a 

 large nucleus seems to be associated with the terminal 

 duct of the auxiliary system but it is not certain that 

 the nucleus is in the duct wall. In R. sergenti Maupas 

 found both an anterior and a posterior branch, each 

 bifurcate (Fig. 113 A). 



3. The .'^scaridid or inverted U-type. Historically one 

 nf the systems most commoiily studied and referred to, 

 it is not confined to ascaridids but occurs in spiruroids 

 pnd in at least one group of rhaTsditoids (Cephalobidae). 

 As pointed out by Toi'nquist (1931) polyphyletic origin 

 of the inverted U type from the H form occurs even 

 within genera and this system cannot be regarded as 

 separate and distinct from la. The essential parts are 

 an elongate, cuticularly lined terminal duct, a sinus, and 

 two posterior lateral canals. By custom Ascaris lunibri- 

 coides is retained in this classification though distinct 

 rudiments of anterior canals are present (Fig. 112 H). 



The system as described in Ascaris lumbricoides and 

 Parascaris cquoruvi by Goldschmidt (1906) consists of 

 three cells, one nucleus in the wall of the terminal duct, 

 another in the protoplasmic part of the "anterior bridge" 

 and a third, the giant excretory nucleus in the left 

 lateral chord. Mueller (1929) by means of injections 

 showed Goldschmidt in error relative to the existence 

 of both an anterior and posterior "bridge" (sinus). As 

 found by Mueller and verified in sections by the writer, 

 the terminal duct leads to the left lateral canal with 

 which it connects very close to the anterior extremity of 

 the canal; the right lateral canal extends further an- 

 terior than the left, indeed nearly to the level of the 

 excretory pore. The excretory sinus is quite variable, 

 its lumen liranching and anastomosing (Fig. 114 A-B & 

 E). The wj'iters found a single nucleus (Fig. 114 F) 

 definitely within the wall of the terminal duct about 

 half way along its length. The gigantic sinus nucleus of 

 Ascaris is moved to the left lateral chord and is sur- 

 rounded by branching capillaries of the left lateral 

 canal. These branchings become less marked posteriorly 

 and finally fuse formine a typically simple canal. The 

 canal may give off minute tubules (Fig. 114 C) as were 

 previously noted in Cucullnnus but no additional nuclei 

 have thus far been observed in the canal walls. Gold- 

 schmidt (1906) thought the tubules extended into the 

 adjacent areas of the chords and they were the actual 

 secreting part or glandular structure. Subsequent work 

 has disproved this hypothesis. 



The camallanid inverted U system is essentially the 

 same as the H system found in that group and requires 

 no esoecial comment. In filarioids, spiruroids and dracun- 

 culoids the inverted U system is apparent in totomounts 

 used for taxonomic study (Fig. 14 I & L) but has not 

 been subjected to critical analysis. The same is equally 

 true of cephalobids such as Panagrolaimus subelongatus. 



Pig. 114. 



A-F — Ascaris lumbricoides (A — Analine blue-black injected speci- 

 men showing terminal duct, sinus and associated tubules ; B — 

 Details of same region showing sinus nucleus ; C — Right lateral 

 chord showing canal branches ; D-E — Left lateral chord in sinus 

 region, D — at level of sinus nucleus ; E — anterior to that level ; F — 

 Terminal duct nucleus) : G-J & O — Anisalfis simplex (G — Detail of 

 tubule branching and terminal acini ; H-J — Cross sections through 

 sinus cell at level of nucleus. H of a young specimen, I of an 

 older specimen. O and J of a senescent specimen) : K — Loa loa 

 (Excretory pore and cell in microfilaria) ; L-M — CnniUa-nus sp. (L — 

 Lateral chord and canal near sinus : M — same in posterior part of 

 body) : N — Mcrviis hrevis (Lateral view of anterior end of adult, 

 .showing excretory cell): P-R — Pkmiodermopsis longisetae (P — 

 Excretory pore and terminal ampulla: "Q — -TESophageal region : R — 

 Cross section at level of excretory cell) ; S-U— ^EnopJus communis 



(S — Cross section at level of excretory nucleus; T — cross section 

 posterior to S ; V — Ventral view of excretory cell as seen in 

 toto) : V-W — Anaplectiis prajiulosus (V — Cross section at level of 

 ventral gland cell: W — Ventral view of excretory system and 

 associated structures as seen in toto) : X — Chromadora quadrilinea 

 (Esophageal region): Y — Spitophorella paradoxn (Cross section at 

 level of excretory cell) : Z-CC — CnmnUanlls mierocephalus (Z — 

 Terminal duct showing first nucleus : AA — Terminal duct showing 

 second nucleus : BB — End of terminal duct connecting with sinus ; 

 rc — Sinus with its nucleus). A-B. After Mueller, 1929, Ztschr. 

 Zellforsch, v. 8 (3) ; G-J & O. After Mueller. 1927. Ztschr. Zell- 

 forsch. V. 5 (4) ; K. After Fuelleborn. 1929. Handb. Path. Micro- 

 organ, v. 6 (2) ; N. After Hagmeier, 1912. Zool. Jahrb. v. 32 

 (6) : U. After de Man, 1886, Nordsee Nematoden. Remainder 

 original. 



130 



