further noted that the rachis cannot be of great signifi- 

 cance to nemas sinc<? it is often apparently absent in 

 some species {Maciacis monhystera) while it is present 

 in closely related forms, (Oxyuris equi) . Without in any 

 way passing judgement on the function of the rachis, we 

 may note that in some forms the growth zone of the 

 ovary consists of a cylinder of oogonia surrounding the 

 rachis {Ascaris), while in others (Spironoura affine. Fig. 

 119, A-B) and the majority of free-living nemas) the 

 growth zone is a single chain of cells and the rachis 

 disappears as the oogonia assume the single file. The 

 rachis appears in direct continuity with the cap cell in 

 Spironoin-a (Fig. 122 G). In countless free-living nemas 

 (ex. Mononchiis, Trilolnis Figs. 120 D & I-P) the germ- 

 inal zone is greatly reduced in length and there seems 

 never to be a cylindrical germ chord. In such forms no 

 distinct cap cell or rachis is present. 



(b) Oviduct. The oviduct, when distinct, consists of a 

 narrow tube with high columnar epithelium. According 

 to Musso, the oviduct in Ascaris, like the ovary, is devoid 

 of a muscular layer except in the zone approaching the 

 uterus. Rauther (1918) described a muscular sphincter 

 at the ovary-oviduct junction in Macracis (Fig. 115 L), 

 and in many oxyurids the oviduct has a muscular appear- 

 ance. A slight enlargement in the proximal part of the 

 oviduct serves as a spermatheca and fertilization chamber 

 in Macracis monhystera (Rauther, 1918) and Syphacia 

 obvelata, (Vogel, 1925). In the latter organism (and in 

 many other oxyurids) the ova develop their shell while 

 in the oviduct and Vogel was of the opinion that the 

 ovidu;t should be regarded as an egg former and possibly 

 a "shell gland". In the majority of nemas (including 

 Macracis, Spironoura and Rhabditis) shell formation is 

 first visible in the proximal part of the uterus and the 

 oviduct cannot be regarded as a zone of egg shell de- 

 position. 



(c) Uterus. The greater part of the uterus has a 

 squamous epithelium covered by a muscle layer of cir- 

 cular and oblique fibers, the development of which varies 

 both in localized regions of a given form and in corre- 

 sponding regions in diverse nemic groups. The distal 

 part of the uterus commonly functions as a seminal re- 

 ceptacle or fertilization chamber even though it is not 

 externally set off from the remainder. In Ascaris the 

 epithelium of this region consists largely of elongated, 

 tufted cells which were regarded by Leuckart as nurse 

 cells to the spermatozoa. Romieu (1911), Von Kemnitz 

 (1912) and Romeis (1913) found that these cells exer- 

 cise a phagocytic activity on unused aging spermatozoa. 

 Musso (1930) has shown that the inter-locking branched 

 muscle fibers of the seminal receptacle rather suddenly 

 give pla;e to more regularly arranged circular muscle 

 fibers of the uterus proper (Fig. 121 C). In other 

 nemas such as Spironoura (Mackin, 1936) the uterine 

 musculature is obviously spiral (119 A, 122 D) rather 

 than circular though individual muscle cells do not reach 

 completely around the uterus. Peristaltic contraction 

 waves passing along the spiral serve to carry the egg 

 along without the aid of longitudinal muscle fibers. The 

 uterus of Enterobius (Fig. 122 BB-CC) has a web-like 

 musculature. Sometimes, as in Ascaris, (Musso, 1930) 

 longitudinal connective tissue fibers are apparent in the 

 external membranes which cover the uterus, oviduct, and 

 ovary, as well as other organs bordering on the body 



Fig. 117. DIAGRAMS OF FEMALE REPRODUCTIVE SYSTEMS. 



A — PntiagrolaiiiiHS heterovlu-ilns. B — Cephalobus pcrseffiiis. C — 

 Brevibitcca saprophaga. D — Labiilurus gulosa. E — Atractis ductj/luris. 

 F — Trichuris suis. G — Heligmosomiwi laeve. H — Cainalla^itis 

 lacustris. I — Tetrutneres fissispina. J — Ditylrnchits dipsaci. K — 

 Aphelenrhoides fragariae (Chrysanthemum strain). L — Ascaris 

 lumbricoides ; M — Oxystomina cyUiidraticauda. N — Halanonchus 

 macramphidum. O — Cryptonchns 7iudus. P — Heterodera fnarionu 

 Q — Hflironema ringuillae. R — Theristits sentiens. S-T — Ascaris Zwwi- 

 bricoidcs (S, male: T, female). U — Zoiiiolaimus setifera. V — Oxyuris 

 equi. W — Dcrmatoxys veligera. X — Kiluluma brevivaginata. Y — 

 Hedruris armata. 



A. after Steiner. 1935, Proc. Helm, Soc, Wash, v, 2 (2) ; B, 

 after Thome, 1937, Proc. Helm. Soc. Wash. v. 4 (1) ; C, after 

 Goodey, 1935, J. Helminth, v. 13 (4) : D-E, after Thapar, 1925, 

 J, Helminth, v. 3 (3-4) ; F. after Rauther, 1918. Zool, Jahrb. 

 Abt. Morph., V, 40; G, after Seurat, 1915, Bull. Sc. France & Belg. 

 7. s., V. 48 ; H, after Toernquist, 1931, Goeteborgs Kungl, Vetensk, 

 s, B, V. 2 (3); W, after Seurat, 1920, Hist. Nat. Nem. Berberie ; 

 Q, after Yamaguti, 1935, Jap, J. Zool. v. 6 (2) ; R. after Cobb, 

 1914, Tr. Am. Micr. Soc, v, 33 ; S-T, after Musso, 1930, Ztschr. 

 Wiss. Zool. V. 137 (2) ; U, after Cobb, 1898. Dept. Agric. N. S. 

 Wales, Misc, Publ. No. 215 : V, after Martini, 1916, Ztschr. Wias. 

 Zool. V. 116; X, after Thapar, 1925. J. Helminth., v, 3 2 ; Y. 

 after Perrier, 1871, Compt. Rend. Acad. Sc. V. 72 (12). Remainder 

 original. 



cavity. Concerning the histology of the uterine muscula- 

 ture there is little to be said. Plenk (1924) erroneously 

 attributed striation to it as to all other musculature in 

 Ascaris. Actually, the individual muscle cells seem to be 

 either platymyarian, with the fiber layer next to the 

 epithelium, or circomyarian. 



In Ascaris the epithelium of the uterus proper, is com- 

 posed of five to six sided, low or high cuboidal or irregu- 

 lar epithelial cells. Van Beneden (1883) and Martini 

 (191()) attributed a bacillary layer to the uterine epithe- 

 lium in Ascaris and Oxyuris respectively but other 

 workers have been unable to confirm such findings in 

 these or other nemas. In Ascaris lumbricoides Musso 

 found the majority of uterine epithelium cells binucleate 

 (Fig. 121 A-B) in all specimens, other nuclear numbers 

 being three, four, and one in order of occurrence, four 

 nuclei being found only in comparatively young females; 

 nuclear division was always found to be by amitosis and 

 cell division often unequal. In many parasitic nemas 

 such as Ancylostoma duodenale (Looss, 1905), Macracis 

 monhystera (Rauther, 1918) and Vephalobellics papilliger 

 (Chitw. & Chitw., 1933) and in most free-living nemas 

 the chief part of the uterus has no distinct musculature. 

 A uni-nucleate simple squamous epithelium is the rule, 

 in Ancylostoma auodenale, Looss reported the uterine 

 wall to be composed of only two cell rows. Possible cell 

 limitation (oligocyty) in the uterine epithelium of other 

 meromyarian nemas has not been investigated. 



When an undivided portion of the uterus forms an egg 

 pouch, as in Ascaris lumbricoides and Abbreviata poicilo- 

 metra (Fig. 118 LL-MM), the epithelium and musculature 

 are not particularly modified but when an ovejector 

 IS formed the epitnelium usually becomes thicker and 

 the musculature more highly developed. 



(d) Vagina. The true vagina (vagina vera) of nemas 

 is always distinctly recognizable histologically though it 

 may be difticult, it not impossible to limit in gross study. 

 Jtvegaraless of degree development, the vagina is lined 

 with a distinct, well-developed cuticular layer continu- 

 ous with the external cuticle but differing from this 

 cuticle in being composed of a single layer. Its epithelium 

 is composed of relatively few large cells usually quite 

 distinct in appearance from the epithelium of the uterus 

 or vagina uterina. Because of its exceedingly narrow, 

 siit-hke form the vagina of tree-living nemas has not 

 been investigated histologically, but in Trilobus (Fig. 

 IzO J) we judge it to have four cells situateci at the 

 junction of vagina and uterus. With elongation 

 of the vagina, the structure becomes more obvious 

 and Rautner (lal8) was able to identify a single 

 group of four nuclei at its proximal end corre- 

 sponding to rour longitudinally oriented cells forming 

 tne entire vagina vera of Macracis monhystera (Fig. 122 

 I). Chitwood and . Chitwood (1933) have found that 

 eight cells, arranged in two tandem groups of four 

 each. Compose the vagina of Cephalobellus and Hystrign- 

 athus rigidus (Fig. 122 X) and Spironoura affine. This 

 arrangement is in accord with the general tetragonal 

 symmetry of the vagina of oxyuroids, the nuclear number 

 eight being preserved in Atractis though no other sem- 

 b.ance of symmetry occurs in the vagina of that form. 

 In ascaridids and spiruroids there is a distinct cell limi- 

 tation in the vagina, but even so symmetry and cell con- 

 stancy are apparently lost; Musso records the vagina of 

 Ascaris as composed of 10 to 12 longitudinal rows of 

 polyhedral squamous epithelial cells (Fig. 121 E-F), while 

 Rauther (1918) found the vaginal epithelium of Trichuris 

 to be composed of an unlimited number of cells (Fig. 

 122 T-U). 



The musculature of the vagina is continuous with that 

 of the uterus and is of the same general type but may 

 form a much thicker layer; in some groups the vaginal 

 muscle may be several cells in thickness and cause the 

 vagina to have a distinctly laminated appearance. The 

 cell bodies of the muscle cells are commonly pressed out 

 of the wall assuming a bladder-like shape. These proto- 

 plasmic masses have commonly been termed vaginal 

 glands. Structures which cannot be so interpreted but 

 may actually be glands have been described in Allodapa 

 numidica by Seurat (1914), in Thoracostoma strasseni by 

 Tiirk (1903), seen also in Cylicolaimus magnus by Jager- 

 skiold (1901) and Halichoayiolaimus longicauda by Ditlev- 

 sen (1919) (Fig. 123). Their function has not been 

 ascertained. 



141 



