in Ci/atholdimiis ocellatiis he found tlie cuneus-corpns (Fig. 

 109 OP) extremely large, the crura considerably smaller and 

 in addition he found a small anterior ventral piece (capitulum). 

 In the latter species the spicules are guided anteriorly, pos- 

 teriorly, medially and laterally. In other forms such as Syrin- 

 golaimus striatocaitdatiis (Pig. Ill E) and Anoplnstoma vivi- 

 panim, de Man (1888, 1907) described well developed 

 grooved crura accompanied by a weak corpus and in these eases 

 each spicule moves in a groove of the corresponding crura. 

 In Thrristiis iHiniiiiiKlicd (Fig. Ill F-G) the gubernaculum 

 appears to surround the spicules, and de Man (1890) found it 

 to be scarcely differentiated into separate parts, but tlie medial 

 region pro.iects as a cuneus between tlie spicules and the lat- 

 eral parts partially surround the spicules and serve as crura. 

 In SphacrolaimiiK hirsiiliis (Fig. Ill HI) the same author 

 found a gubernaculum much like that of Theristtis but a capit- 

 ulum in addition. Another type of variation, particularly 

 characteristic of the Axonolaimidae and Linhomoeinae, though 

 sometimes occurring in other groups, is due to the presence of 

 two posterior prolongations of the corpus, termed the apophy- 

 ses. In Tcrschellinpia lonf/icauilnla the spicules are separated 

 by a distinct cuneus and held in position laterally by flanges 

 of the corpus, no distinct crura being present, while in Metalhi- 

 homneus typiciis (Fig. Ill J-K) capitulum, cuneus, crura, cor- 

 pus, and apophyses may all be distinguished. 



The musculature of the gubernaculum has been previously 

 described (p. 43) but the origin and insertion of the various 

 muscles is not as limited as previously indicated. The guber- 

 naculum often behaves as though hinged at the .junction of 

 the spicular pouch and cloaca. Muscles (protractor gubernac- 

 uli) attached to the proximal ends of the gubernaeular corpus, 

 crura or the distal ends of the apophyses extend posteriorly to 

 the ventral body wall and their contraction moves the distal 

 ends of the corpus, crura, and cuneus anteriorly, forcing the 

 spicules outward, their tips pushed anteriorly (into the fe 

 male). Muscles from the proximal ends of the crura in such 

 an instance (Enoplus) extend laterally and ventrally to the 

 body wall; their contraction moves the distal ends of the various 

 gubernaeular parts posteriorly withdrawing the spicules. 



FUNCTION OF THE SPICULES 



Thougli it was recognized by Schneider (1866, p. 244) that 

 the spicules are never hollow and that spermatozoa do not or- 

 dinarily flow "through them," the conception that they are 

 hollow and act as true intromittent organs has somehow per- 

 sisted. A locatory and excitatory function has been ascribed 

 to the spicules bv Schneider (1866), Biitschli (1872), Rauther 

 (1909, 1918, 19.30), Seurat (1920), Baylis (1929), Mueller 

 (19.30) and Chitwood & Chitwood (1933). On the other hand, 

 Looss (190.")) and zur Strasscn (1907) considered that the two 

 flanged spicules in AncyhisUima and Pliilonietra come together 

 in the form of a tube and that the sperm flows between them. 

 The transmission of sperm down the groove or between the 

 grooves of flanged spicules has been considered probable by 

 Mueller (1925), Baylis (1929) and Rauther (1930). In cases 

 where the spicule or spicules are devoid of flanges, their cross 

 section being practically circular throughout (Ascaris, Trichv- 

 ris, l)iocl(iphymn) there seems to be no conceivable way 

 by which they could "conduct the sperm." Regarding this 

 type of spicule, Mueller (1930) was of the opinion that they 

 are withdrawn during the period of sperm movement for he 

 found a copulating pair of Ascaris in which, upon section, the 

 spicules were found luif to be inserted. However, observations 

 of copulating nematodes in which the s|)icules have been seen 

 alternately inserted and withilrawu have been numerous and 

 Mueller's finding seems hardly significant. The spicules take 

 an active part in cojiul.'ition aiul we have merelv to define that 

 part. 



In forms with flanged spicules, do the flanges ever form a 

 tube or groove by which the sperm pass to the female? Tube 

 formation by two spicules in forms such as SpiroiKiiira, Anvy- 

 Insfoma Jiiid PraUistronpyhis is undeniable. This tube is formed 

 by the orientation of the spicules by the gubernaculum (Fig. 

 110 A-T, 33K) while they are still in the spicul;ir jmuch. 

 There seems to be no way liy which the sperm could gain 

 entrance to this closed tube after it reaches the cloaca. 



The spicules miglit more plausibly play the role of sperm 

 transmitters in forms where the spicules are dissimilar and 

 one of them is flanged or where the spicules are distally fused 

 with a median groove. Mueller (192.")) described such an in 

 stance in Prnlrphis in which he noted that the blade of the 

 left spicule had wide flanges forming a nearly complete tube 

 open proxinially as well as distally. He also found a cloaca- 

 spicular canal connecting the up]ier part of the cloaca with the 

 spieular pouch ,iust anterior to the beginning of the spicular 



blade (Fig. 109 AA). Such a condition has been seen neither 

 before nor since. The writers can more easil.v think of flanges 

 as primarily for the purpose of increased rigidity and it is 

 conceivable that the flanges aid in keeping an open passage- 

 way into the vaginal lumen. 



The movement of the spicules back and forth during co]uila- 

 tion would serve not only to keep the vulva and vagina open 

 but also, at least to some extent, would actually propel the 

 sperm into the female.* Branching of the spicular blade and 

 twisted spicula formation such as occurs in trichostrongyles 

 (Fig. 109 U, FF) would seem to be particularly adajited to 

 such activity. In forms with markedl.v unequal and ilissimilar 

 spicules it is notable that the vagina is always quite long and 

 tubular. Seurat (1920) advanced the view that in such sjiecies 

 the short spicule opens the lips of the vulva and the proximal 

 region of the vagina while the long spicule assures the progres- 

 sion of the sperm in the long vagina. It is true that the short 

 spicule usually has a large hook which would lie well adapted 

 as a holdfast. 



The gubernacidum is, of course, primarily a spicular guide 

 and prevents the spicules from breaking through tlie wall of 

 the spieular pouch and cloaca when exerted. In such forms as 

 Tersehellingia, Enoptiis and Spironoiira it may also act as a 

 levator. Ordinarily the gubernaculum is not everted during 



*Seurat states that the spicules are absolutely inuiiohile during copu- 

 lation but in living free-living nematodes such as Hhabditis the ivriters 

 have observed alternate withdrawal and insertion over extended periods. 



Kiu. 1 1 1 

 A-C — KnopUm coiumvnis (A — Gubernaculum, ventral view; B — 

 spicule; C — gubernaculum). D — E. hrpviti (Gubernaculum and tips 

 of spicules). K — Syriniiolninius atr\atnea\idntus. F-G — Theristus nor- 

 jiiandica (Spicules and gubernaculum, lateral view, F and ventral 

 view, G). II-l — Sphat'tolaimtts hirsuliis (H — Detail of guhefnaculum 

 as seen in I). .J-K — ^fet(tUnhomo^'u.^< ti/picug (J — \'entral view; K — 

 lateral view). L-M — Anoplontoma vlripfinnn ( L — Ventral view; M — 

 detail of gubernaculum). A-D, after de Man, 1886, Nordsee Nema- 

 toden; E, after de Man, 1888, Mem. Soc. Zool. France, v. 1; F-G, 

 after de Man. 1890, Ibid., v. 3; H-M, after de Man, 1907. Ibid., v. 20. 



120 



