are the primitive nemic condition. Biitschli (1876), 

 Steiner (1919, 1920) and Seurat (1920) have taken the 

 view that parallel posteriorly opening gonads are primi- 

 tive for both sex?s in nemas. Such a condition is a 

 contradiction to what we know of free-living nemas. 

 First, parallel ovaries are known to occur in only one 

 genus, not parasitizing vertebrates, said genus being the 

 highly specialized plant parasite, Heterodera (Fig. 115 

 M). Second, parallel testes are known to occur in only 

 two genera, Anticoma (Fig. 124 L) in which the parallel 

 condition appears to be a modification of the opposed 

 condition and Heterodera marioni in which the paired 

 testes seem to have arisen secondarily as a longitudinal 

 splitting of a single testis (see p. 150). Othervidse, 

 wherever two gonads are present in free-living nemas, 

 they are opposed. Without venturing further in the 

 matter of primitivity at this time (see also p. 195) the 

 following points seem notable: Admitting that from the 

 standpoint of general comparative anatomy the paired 

 gonads of both sexes should have opened posteriorly into 

 the ventral side of the cloaca, the ontogeny of present 

 day nemas indicates that in the original nema the vulva 

 was separate and equatorial. Any other arrangement 

 must have occurred prior to the origin of the class. 



Since the female reproductive system is more often 

 used in systematics and since more observations have 

 been recorded in more diverse group? it shall be con- 

 sidered first. 



Female Reproductive System 



GROSS MORPHOLOGY 



Seurat (1913-1920), in a series of papers culminating 

 in his "Histoire Naturelle des Nematodes de la Berberie", 

 •developed an extremely useful nomenclature for the parts 

 of the female reproductive system and at the same 

 time presented more useful information on this subject 

 than all other workers combined. Seurat was fully 

 aware that the groups formed by his classification of 

 the female reproductive system were artificial and he 

 himself pointed out the numerous transitions from one 

 of his major groups to another, within families and 

 genera. His classification was as follows : 



I. Uteri opposed. Amphidelphes: 



1. a: Dictyocauhis filaria (Metastrongylidae). Va- 

 gina short, uteri opposed, oviducts U-shaped, ovaries 

 converging (Fig. 116 Q). 



b: AUodapa numidica (Heterakidae) . Similar to 

 la but with longer vagina, and uteri twice reflexed in 

 U-shape. 



c: Camallaniis microcephahts (Camallanidae). 

 Similar to la but with longer vagina, and posterior gonad 

 represented by a blind uterine sac, posterior ovary and 

 oviduct absent (Fig. 117 H). 



2. Heterakis (Heterakidae). Vagina much elon- 

 gated, U-shaped; uteri opposed, reflexed; ovaries much 

 contorted (Fig. 116 R). 



3. Haemonchus (Trichostrongylidae). Vagina short; 

 anterior uterus and ovary extending anteriad; posterior 

 uterus U-shaped; posterior ovary also anterior to vulva 

 (Fig. 116 T). 



4. Trichuris (Trichuridae) . Anterior genital tube 

 totally absent; posterior uterus extending nearly to pos- 

 terior extremity; oviduct U-shaped extending nearly to 

 vulva where it is again reflexed; ovary much coiled, 

 extending length of body (Fig. 117 F). 



Fig. 115 

 Female reproductive system. A-B — Sphaeruliiria bombi. C — Telra- 

 mevps fissispinn. D — Trichosomoities rrassirawlu. E — S'^ntonema 

 wuelkeri. F-H — Rhabditis sechellensis (F, during sperm formation; 

 G and H. later stages). I — AUantonenta mirabilc. J — Tylenrhineina 

 oscincllae. K — Tripiiis gibbosus. h — Marraris vionhystera. M, Q-R — 

 Heterodera marioni {M, entire female reproductive' system R. blind 

 end of ovary : Q. upper part of uterus, all as seen in specimen 

 dissected in egg albumen). N — H. sehaehtii. — Thoracostoma 

 strasseni. P — Rhabditis aspera v. aberrans. S — Aplectona gigantiea, 

 vagina showing origin of uteri and structure of ovejectors. A-B 

 and K, after Leuckart, 1SS7. Abhandl. Math.-phys. Classe, Konigl. 

 Sachs. Gesellsch. Wiss. v. 13 (8) : C, after Travassos. 1919. Mem. 

 Inst. Oswaldo Cruz. v. 11 ; D, after Hall, 1916. Proc. U. S. Nat. 

 Mus, V. 50 : E, after Bovien. 1932. Videnslc. Medd. Dansk. Naturh. 

 Foren., v. 94; F-H, after Potts, 1910, Quart. J. Micr. Sc, v. 55 

 (3); I, after Wuelker, 1923, Ergeb. u. Fortsch. Zool., v. 5; J. 

 after Goodey, 1930, Philosoph. Tr. Roy. Soc. Loud. s. B, V. 21S ; 

 L. after Rauther, 1918, Zool. Jahrb. Abt. Morph.. v. 40 ; N. after 

 Strubell. 1888, Biblioth. Zool.. v. 1 (21 ; O. after Turk, 1903. 

 Mitt. Zool. Stat. N'eapel. v. 16; P, after Kruger, 1913, Ztschr. 

 "Wiss. Zool., V. 105 (1). Remainder original. 



5. Amaria laticeps (Acuariidae). Uteri opposed, 

 very long, serving to contain a mass of many small 

 eggs; oviducts and ovaries very filiform, oviducts enter- 

 ing uterus in esophageal and preanal regions (Fig. 

 116 P). 



6. Protrellus (Thelastomatidae). Vulva shifted 

 anteriad; vagina greatly elongated; uteri opposed (Fig. 



116 K). 



7. One-o\aried forms with the vulva posterior. 

 Acaaria invaginata, HeUgmosomum laeve, Atractis dacty- 

 liira (Fig. 117 E). 



II. Uteri parallel. 



A. Opisthodelphes. Uteri directed posteriad; vulva 

 usually anterior to middle of body. 



8. Af:cnris hnnhricoides. Vagina short; uteri directed 

 posteriad; oviducts and ovaries much contorted (Fig. 



117 L & T). 



9. Physalopterids, thelaziids, and filariids are usu- 

 ally opisthodelphic; the ovaries coiled in the preanal 

 region. 



10. Maupasma. Vulva situated in anal region; uteri 

 directed anteriad, turn posteriad and terminate in two 

 parallel ovaries in posterior region. 



B. Prodelphes. Uteri directed anteriad. 



(a) Original or primitive prodelphy. 



11. Dermatoxys. Seurat considered the oxyurids the 

 most primitive group and characterized them as for the 

 most part prodelphic but with variably situated vulva. 

 (Fig. 117 W). 



(b) Secondary prodelphy. 

 aa) Vulva near anus. 



12. Cliabertia. Uteri extending anteriad. Ovaries 

 coiled in anterior part of body. Type obviously a modifi- 

 cation due to posterior shift of vulva of the amphidelphic 

 type found in trichostrongyles. 



13. Tetnimeres. Uteri narrow, parallel and very 

 long; oviducts and ovaries filiform, entwined around the 

 uteri in the esophageal region (Fig. 117 I). 



bb) Vulva anterior 



14. Aprocta orhitalis. Genital tubes parallel, U- 

 shaped, descending posteriad then reflexed anteriad 

 where they terminate in oviducts and ovaries entwined 

 in the cephalic region. 



Today, Seurat's terminology is accepted in general 

 and adjectives derived therefrom are applied widely in 

 taxonomic descriptions. Because of the difficulty in 

 tracing uteri and ovaries certain arbitrary limitations of 

 definition have come to be accepted. Thus, amphidelphic 

 is redefined as having uteri opposed at origin regardless 

 of location of oviducts or ovaries. Similarly, prodelphic 

 is defined as having uteri parallel and anteriorly directed 

 at origin while opisthodelphic is defined as having uteri 

 parallel and posteriorly directed at origin. 



Other adjectives also introduced by Seurat, Ortlepp 

 and Schulz were as follows: Monodelphic, meaning: pro- 

 vided with one complete genital tube. (Because of 

 variability in the degree of development of a second 

 uterus and ovary in such forms, this word has come to 

 be applied to the ovary. Thus, Camallanus and Atractis 

 are now both considered monodelphic prodelphic). 

 Didelphic meaning: provided with two complete genital 

 tubes; forms may be didelphic opisthodelphic or didelphic 

 amphidelphic. Tetradelphic, meaning: provided with four 

 complete genital tubes; Polydelphic provided with more 

 than four complete genital tubes. 



Parts of the Reproductive System. Seurat (1920) 

 like Bastian (1866) noted the morphologic difference 

 between the vagina and uteri of free-living nemas and 

 those same structures of parasites. Primarily the genital 

 tubes in females (Fig. 3) of free-living nemas consist 

 of vulva, simple transverse vagina, paired opposed uteri 

 without heavily muscled areas, short sometimes indis- 

 tinct oviducts and short tubular ovaries. A definite seminal 

 receptacle or spermatheca may be developed as an out- 

 pocketing of each uterus (Fig. 116 A) or oviduct; in 

 other forms its function is assumed by the ovarial end 

 of the uterus (Fig. 116 B, P & G). As noted by Filipjev 

 (1918, 1922, 1929, 1934) the ovaries are outstretched 

 (Fig. 116 L-N) in some large groups and reflexed (Fig. 

 116 C-F & 0) in other large groups. Actually the ovaries 

 themselves are seldom reflexed in free-living nemas, 

 more commonly the flexure occurs at the junction of 

 ovary and uterus, or of ovary and oviduct. 



Vagina and Uteri. With parasitism there is generally 

 an increase in length of the entire genital tube with 

 coincident increased egg production, and increase in 



137 



