It li;is lu'i'ii soon in ;ill t'ri'i' living m'iii;itiuli's .sliiilic'd b.v tlic 

 writrrs. The protrai'tor imisi'li's iif tlio spii'iiU's t'uiiii a cdiii 

 I)lt'ti' loiiKitiuliiial nuisi'lo layer on tlie surface (if the poueli in 

 most parasitie nematinles l)iit in free-livini; iieiiiateiles these 

 imiseles are iiiiire euiiiiiuiiilv eonliiieil tii tlie ilcirscihiteral sides. 

 The piiueli aiiil aeeenipanvint; iiuiseles are iiiiist ediispieiuiiis in 

 Tri/u/hi and Triiihincltiiun iif the free living nematodes and 

 (livi' an appearanee ( FiR. lO^b") whieli is peeiiliar to tliese 

 Ki'nera and their rehitives. In the Stnmn.vlina and Dieetiipby- 

 matina the spieuhir poueh eommonly Joins the eloaea sonu' dis- 

 tanee anterior to the anus and in the Triehuroidea tliis tendeiuy 

 is carried to an extreme (Fig. 110 PD). In otlier groujis of 

 nematodes the spicules can scarcely ever lie said to lie within 

 the cloaca even for a short distance; actually they niercdy pass 

 thr<iuf;li a common eloaeo-siiicular orifice. Mueller (lil:2."i) and 

 Chitwciod and Chitwood (I'.KiH) found the spicules of PrcilifituK 

 and Ct phaldhcUiiS to have a .sejiarate aperture iniineiliately 

 posterior t<i the cloacal oiiening. 



The spieular pouch should under no circumstances Ije con 

 fused with the so-called spieular sheath of I'ricliiiris, which 

 was nanu'd the cirriin liy Kauther (190!l). It is a unique oc- 

 currence in the Nematoda tliat in Tricliiiri.i and relatives the 

 lining of the cloaca (cirrus) is itself everfilile anil often armed 

 with teeth (Fig. lOitL) ; this structure is capable of being 

 inserted with the spicule into the vagina during cojinlafion and 

 undoubtedl.v serves as a true jienis. It is in direct ccmtinuity 

 with the external cuticle ami when refracted there are three 

 layers (Fig. 110 AA) of cloacal lining. The feces must pass 

 through the cirrus for evacuation to take jilace. 



1>. Sl'ICT'LKS 



Nematodes usually have two spicules, each spicule being es- 

 sentially a tube covered by a sclerotized cuticle and containing 

 a central protoplasmic core. Its cuticular covering is continu- 

 ous with the cuticular lining of the spieular pouch and from 

 that standpoint the spicules may be regarded as evaginations 

 of the spieular pouch. The cuticle is often layered, the outer 

 layer (Fig. 109 CO being colorless and structureless while 

 the inner layer or layers arc tan to brownish and sometimes are 

 composed of numerous jirismoidal elements. In other cases the 

 spicules may ajijiear to be spongy or reticulated (Fig. 110 NN). 

 The prismoidal elements (Fig. lOSt CC) should not be confused 

 with the so called striation such as occurs in Stenunis (Fig. 

 .S3 K), Profo.itron.gylus (Fig. 110 EE), etc. Such striation is 

 due to the extension of the selcrotized ribs into a weak or non- 

 sclerotized flange. The central proto[ilasmic core of the spicule 

 may or may not contain the njclei of the spieular epithelium. 

 These cells and nuclei are often situated anterior to the proxi- 

 mal end of the spicules, surrounded by the retractor muscle. 

 Their number is variable, four being recorded in Ascaris (Fig. 

 108 G & K). Ordinarily one finds each spicule provided with 

 two retractor muscles and two jirotraetor muscles. Both pairs 

 of muscles are attached to the proximal end of the spicule. 

 The retractors extend anteriad and toward the lateral chord 

 wliere they may be attached to the body wall either sub- 

 dor.sally, dorsolaterally or ventrolaterally dependent upon the 

 species involved. The protractors tend to surround the spieu- 

 lar sheath and may be inserted postanally to the body wall or 

 to the dorsal side of the spieular pouch. In those groups in 

 which a single spicule is present, the retractor muscles extend 

 to both the right and the left body walls. In exceptional in- 

 stances the protractors and retractors are composed of numer- 

 ous cells which form a longitudinal muscle layer on the 

 .spieular pouch (Figs. lOS A, C & 110 DI) ) that is quite char- 

 acteristic of the groups involved (Triehuroidea and Dioctophy- 

 matoidea). As a rule each spicule may be divided into three 



sections, the he:id ( (•.■ipitnhini ), shaft (calomus), and blade 

 (lamin:t). The lie.'id is the modified portion of the |iroxiiiial 

 end; the sliiifl is the tube like part between the head and the 

 blade; the blade is the dist.'il portion which is usually tlangi'd 

 (Fig. 110 DD lOK). Tlieie may be one or two tiaiiges: if one. 

 it is ventral as seen in cross section and if two, one is dorsal 

 and one ventral (Fig. 110 MM). Though such dilTerentiation 

 of the spicule into regions is the rule, no such regions are 

 apparent in Dioctoplnjma or Tiir)iiiri.i. Extensive iliversity oc- 

 curs in the sjiicular form. 



Two is the basic number of spicules in neuuitodes and the.v 

 originate from a double spieular primordia as stated by .Seurat 

 (l!li;0). However a single spicule occurs in m.any groups of 

 nematodes. It is a characteristic of the Triehuroidea, Diocto 

 phyni.atoidea, Oxyuridae and Thelastomatidae •■ind also occurs 

 in isolated genera of tlie Desmoiloridae ( M iinopnHthia) , and 

 Mermithidae { Jl j/droincrmis) . In other groups it is not un 

 conim<in for tin* spicules to be dislall.v fused .and stages with 

 lu'arly conqilete fusi<in are known. Thus, in Ithubditi.'i strunfiii- 

 UudcK (Fig. 10i( EE, II-.I), R. ttrricola (Khabilitidae) and 

 Xi nialoiUrus axpitiosux (Triehostrongylidae) the distal ends 

 of the si)icules are fused. In the subfamily Ransomnematinae 

 of the Atraetidae, there is a complete series of stages in fusion, 

 including forms such as Canwi/a with two entirely separate 

 spicules. 111 III and Aiir/ra with nearly completely fused spic- 

 ules, and I'lilchroccphala with no siiicules. In the Mermithidae 

 there is a similar series from Mrrmit: with two sep.arate spic- 

 ules, to Paraini'rmis ilrf/an.s (Fig. lO'.l UK) with fiartially fuseil 

 spicules, and lljiilromirmis with a single sjiicule. (ienera and 

 species completely devoid of spicules are of sporadic occur- 

 rence but usu.-ill.v, if not always, such forms are confined to 

 groups characterized by a tendency toward spieular fusion or 

 presence of a single spicule. Tims we find TrichineUa of the 

 Triehuroidea, A.ipicidiiris, Dcrniatoxi/s and several but not all 

 species of Pharjingodon (all representatives of the Oxyuri- 

 dae), Uiistrinnnlhus of the Thelastomatidae and Piilchnicipltahi 

 of the Atraetidae characterized by the absence of spicules. 

 There have been two divergent views on the interpretation of 

 unpaired spicules. One group, led by Schneider (ISOO), main- 

 tains that it is a neotenie character resulting from a failure 

 of division of an originally unpaired spieular priniordium. As 

 has been previously noted, this view^ is based on the erroneous 

 assumption that in two-spicule nematodes the sjiicular prinior- 

 dium is originally single. Other authors have considcre<l the 

 single spicules as resulting from reduction by loss of one 

 spicule. In view of the .several series showing spieular fusion, 

 this theory seems hardly tenable. As Cobb (ISOS) iiointed 

 out, the retractor muscles of the single spicule fornij go to 

 both sides of the body wall, indicating the double character 

 of the spicule. 



Diversities in spieular morphology are too numerous to be 

 covered completely. The general form is often quite diagnostic, 

 being used as generic and specific characters throughout the 

 Nematoda. Unfortunately the shapes vary so much and are 

 sometimes so complicated that one must rely chiefly on illus- 

 trations. Cobb (1S<I8) provided some descriptive terms which 

 might well be more widely applied (Fig. 109 NN). As a rule 

 the spicules of free living nematodes are equal and similar. 

 In parasitie nematodes, jiarticularly the various groups of the 

 ■ Spiruroidea, Filarioidea, and some species of the Ileterakidae, 

 Cucullanidae, Camallanidae and Atraetidae the sjiicules are 

 unequal and dissimilar. Asymmetry in the form of the spic- 

 ules is given varying significance in the different groups. Usu- 

 ally the left spicule is longer than the right but in some forms 

 the converse is the case (Ileierakis galVinae) . The blade of 

 the longer s|)icule is generally alate (Fig. 109 T) and some- 

 times bears a distal hook. The shorter spicule is usually heav- 



FlG. 109 



A-C — HiiOHtronnithtu rubidrts (A — Lateral view of male tail: B — 

 ventral view; O — Detail of telanion, specimen cleared in phenol). 

 D-K — ^ff^ntun elegitns (D — Lateral view of male tail: E — tip of spic- 

 ules). F — Tetriiweres Ineriuiji (Full length of male, showing greatly 

 elongated left spicule). CJ — Oittprliipin rlrrmnrim'ta (Spicules and 

 eiihernaculuni) : H-,7 — XenuttatlirnM nutiinositx (H — Ventral view of 

 male tail, setaceous spicules distall.v fused: T & J — Lateral and ven- 

 tral view of spicule tips). K — Miirithidia fUphnsi (.Spicules). T>— - 

 TrirhnriM i-tit/ns (Tij) of cirrus and spicule). M-N — " Huhrimfnia" 

 sfiirnti (Tiyis of left and right spicules). O-I* — Cj/nthtilitiiinift orrt- 

 liitiiK (Spicules and gubernaculuiu) . Q-R — Parartitiflinnrhits raefus 

 (Spicules and gubernaculum) . S — Dfrnfilnria repenn (spicules). T — 

 OawiUdofilnrin sp. (Spicules). V — Trirlionlroniri/h" prnhnUnny 



(Spicules and gubernaculum). V — Dicheilonptim horridmr (Ventral 

 view of male tail, reversed sides). W-X — Oxiinritt fqiii (\V — Longi- 

 tudinal section of female rectum: X — Dorsal view- of female rectum). 

 y-Z — Stpnunis mlnnr (Lateral and ventral views of male tail). A.\ — 

 Frolfptiifi ohtiiyiin (Reconstriicti'in of cloacal region of male). BB — 

 Hiliiiiii linuira (Spicules). ('(,' — Tricliuris lulpis (Tip of spicule af- 



ter exposure to Faiieliild's trypsin). DD-EE — RhnhdiltK utrongiilnhhs 

 (Spicules, distall.v fused). FF — Ontrrlnffin trifidn (Spicules and 

 gubernaculum). CtJ-MM — Uiioittronfjiilu/t riibidiin (Serial sections 

 tlirough i-loacal region of male showing telamon. gubernaculum. spic- 

 \iles, spieular jiouch and cloaca). N'N — Various spieular shapes (1, 

 arcuate: 2, hamate; :i, arcuate distally: 4, falcate; .i. setaceou-s; 6, 

 sigmoid; 7. linear: S, fusiform: !l, elongate; 10. bent or boomerang 

 sbapcd; 1 1. cuneiform ; 12. Lsbaped). D-E, after Ilagmeier. 1912, 

 Zool. .lalirb.. Abt, Svst. v. ;i2 : F, after Seurat 191:'.. Bull. Sue. Nat. 

 Africjue Nord Alger "v. .'> : G, U & FF, after Kalantarian. 192S. Trud.v 

 (iosudarstv. Inst. Kksjier. .Moskva, v. ;") ; H-J. after Ra.iewska, 19:il. 

 Ztsilir Infekt. v. 40; K. after Wu, 19.14, Sinensia v. .5: M-N & V, 

 after Skriabin, 1917, I'arasit. v. 9: OR. after de Man. 1 SS9. Mem. 

 Soc. Zool'. France, v. 2: \V X. after Martini. 191(i. Ztscbr. Wiss. 

 '/....I « nw: . v.'/ ..ft...' UiivHc :itwl Diiuhnev 192.T Parasit. 



Zool 



<[.ooi. V. 10(i: YZ, after Riivlis iiud Daubne.v. 192.5. Parasit. 

 v 17: AA, after ,1. F. .Mueller, 192.5. .1. Parasit. v. 12; BB. after 

 Raiew9l;a.ia. 192S, Die Setarien etc.; NN, after Cobb, 1898. Misc. 

 I'ubl. No. 2 1.1, Dept. Agrir. N. S. Wales; remainder original. 



117 



