muscular development of uteri and vagina for the ejec- 

 tion of the eggs. The vagina (lined with cuticle) com- 

 monly becomes elongated to the form of a muscular 

 tube. This tube may conne.t directly with the bifurcation 

 of the uteri (Fig. 119 A & B), or it may be followed 

 by a non-ectodermal tube of similar construction (Fig. 

 115 L). In the latter case the second section is termed 

 the vagina iitcrina, the first section, vagina vera.. The 

 functional term ovejcctor was applied to the entire thick- 

 wallod terminal part of the reproductive system by Seurat. 

 In some nemas {Ncmatodii-us, PMg. 118 BB-DD> the ove- 

 jector bifurcates. The three parts of each ovejector were 

 named by Maupas and Seurat (1912), vestibule, sphincter, 

 and trunk (Trompe). Later, (1920) Seurat revised his 

 terminology, then calling the three parts of the strongylin 

 ovejector vestibule, glazing gland [Firnissdriise of von 

 Linstow (1878)] and sphincter. These parts correspond 

 to ovejectors 1, 2 and 3 as described by Ransom (1911) 

 and jiars haiistri.r and pars cjcctri.i: as described by Looss 

 (1905). It is unfortunate that such confusion has oc- 

 curred. The application of functional terms is always 

 likely to lead to such. However, since the ovejector is 

 itself a functional rather than a structural entity, we 

 must continue at least some of the terminology. As re- 

 vised by Seurat, the trompe is sometimes equivalent to 

 the vagina uterina (praeuterus of Rauther, 1918) being 

 the undivided part of the uterus in Ascaris, Goytgglonevia, 

 Spirura (Figs. 117 L, 118 GG-KK & 118 N-0). It may 

 also become a divided thick walled non-cuticular part of 

 the ovejector as in Hahroncma microstoma (Fig. 118 P) 

 and finally it may exist both in divided and undivided 

 parts as in Protospirura numidica. Attempts to homolo- 

 gize parts on the basis of gross appearance lead to little 

 of value. In some forms such as Gongyloncma scntatvm 

 the vagina vera constitutes the major part of the ove- 

 jector and it is separated by a constricted region, i. e., 

 sphincter, from the shorter vagina uterina (Fig. 118 KK). 

 In the same genus in G. mucronatitm the vagina vera 

 is extremely inconspicuous, no sphincter is present, and 

 the major part of the ovejector is vagina uterina. Un- 

 doubtedly such specializations as sphinctei's are of mul- 

 tiple origin and we see no advantage in renaming the 

 functional sphincter of the strongyle ovejector, glazing 

 gland (Fig. 118 CC-ovj. 2). 



In parasites, as also in free-living nemas, monodelphie 

 forms commonly have a postvulvar uterine sac (Fig. 

 117 H) which functions as a seminal receptacle or sperma- 

 theca. Such a uterine sac is considered the remainder of a 

 second genital tube. In others (Tetrameres fissispina) a 

 separate sac is formed as an outpocketing of the vagina 

 vera (Fig. 118 G). More often, the distal ends of the 

 uteri are more or less distinctly modified as seminal 

 receptacles. 



Oviduct. This part of the system is less likely to be 

 confused than other parts. However, like other parts 

 it is a functional rather than a structural entity, i. e., a 

 constricted thick-walled region between uterus and ovary. 

 In Rhabditis strongyloides (Fig. 3) it is hardly an entity 

 while in Sabatieria (Fig. 120 B) and Anuplcctns (Fig. 

 120 C) it is clearly differentiated. In the parasites it 

 attains its greatest development in o.xyurids such as 

 Syphacia. obvelata (Pig. 159 K-L) and occasionally, as in 

 this form, a dilation of the oviduct serves as a seminal 

 receptacle. Vogel (1925) was led by these structures to 

 believe the oviduct functioned as egg former (see chapter 

 XII). 



Ovary. In telogonic forms each ovary consists of (1) 

 a germinal zone and (2) a growth zone. The latter 

 commonly becomes the major part of the gonad in 

 parasitic nemas. 



Abnormalities. Bivulvar specimens have been recorded 

 by Biitschli (1874) in Linhomoeus mirabilis, Paramonov 

 (1926) in Trilobus gracilis and Cassidy (1928) in Dory- 

 lahn.us sp. Cassidy (1933) later recorded a specimen of 

 Prionchtilus muscornm with three ovaries and uteri, the 

 third being connected with the second vulva. Chandler 

 (1924) recorded a specimen of Ascaris lambricoides with 

 three uteri and ovaries. These must all be considered 

 monstrosities. 



DETAILED MORPHOLOGY 



The minute anatomy of very few nemas has been ade- 

 quately investigated. Those who have been major con- 

 tributors to this subject are as follows: Nelson (1852), 

 Bischoff (1855), Meissner (1855), Thompson (1857), Van 

 Beneden (1883), Nussbaum (1S84), Vogt and Jung (1888), 



Wasielewski (1893), Sala (1904), Domaschko (1905), 

 Scheben (1905), Looss (1905), Kemnitz (1912), Romeis 

 (1913), Zacharias (1913), Maupas and Seurat (1912), 

 Seurat (1920), Maupas (1899), Pai (1927, 1928), Musso 

 (1930), Baker (1936) and Mackin (1936). The major 

 part of this work has been done on Ascaris lumbricoides 

 and Parascaris equorum; less comprehensive studies have 

 been made on other species. 



(a) Ovary. The ovary consists of a tubular sac in 

 which germinal cells develop. This sac consists of an 

 epithelial la^^er and a germinal chord. In most nemas 

 with the exception of hologonic forms, germinal elements 

 do not arise from the epithelium. The epithelium con- 

 sists of a single layer of greatly elongate, flat (simple 

 squamous), spindle-shaped cells which reach 1 meter 

 in length in Ascaris Imnbricoides according to Musso 

 (1930) ; each of these cells is multinucleate; as they near 

 the oviduct they become shorter until they are only 2 mm. 

 in length and have 12 to 20 nuclei (Pig. 121 N-0). Such 

 astounding size is apparently a proportional development 

 in keeping with the general oversize structure of Ascaris. 

 The cells show the same spindle-shape but are not spec- 

 tacularly long in Spironoura (Fig. 122 H). 



In general the gonad is divisible into two regions, as 

 follows: (1) The germinal zone: An area of rapid 

 division of relatively small cells, often not showing clear 

 cell boundaries. (2) The growth zone: An area of 

 gradual increase in size of the oogonia. The first of 

 these zones is always relatively short while the latter 

 varies tremendously in size, sometimes amounting to the 

 greater part of the gonad length, as in Ascaris lumbri- 

 coides. Although a conspicuously long growth zone is 

 usually associated with parasitism, it is by no means 

 limited in occurrence, being found likewise in such forms 

 as Meto)ic!io(aimus. 



At the blind end of the ovarial tube the epithelium 

 becomes extremely thin so that its very existence has 

 been denied by some authors, while others have con- 

 cluded that the large cap cell is the epithelial cell of 

 the ovarial terminus. This viewpoint has been questioned 

 by Musso (1930) who regards the cap cell as an un- 

 differentiated germinal stem cell which gives rise equally 

 to both epithelial cells and germinal cells. In accord 

 with the majority of observers, the writers have never 

 seen any sign of nuclear division in a cap cell. Also, we 

 find the protoplasm of the germinal chord rather clearly 

 segregated from this cell in Spironoura (Fig. 122 G). 

 With Maupas (1899) and Pai (1927) the writers would 

 conclude that the cap cell is a part of the ovarial epithel- 

 ium. Cell borders are often difficult to distinguish at the 

 proximal or germinal end of the germinal chord, but 

 sometimes they are distinct and it seems proper to re- 

 gard the region as cellular rather than syn.tial in all 

 instances, since cell boundaries gradually become more 

 apparent as the cells move down the gonoduct. 



The origin and significance of the rachis is as yet 

 unsettled. Beginning at a slight distance from the ex- 

 treme end of the germinal chord one finds a central 

 strand of non-nucleated tissue which extends in Ascaris 

 to the beginning of the oviduct. It would seem that there 

 are two possible origins of the rachis, one as a continua- 

 tion and product of the cap cell, the other as a residuum 

 of enucleated plasma separated off from a germinal syn- 

 cytium. Either assumption has lacked evidence. Earlier 

 authors (Biitschli) leaned to the opinion that the rachis 

 of nemas was comparable to the rachis found in the 

 telotrophic in.sect ovary; such a view would require that 

 it be a feeding mechanism and that it contain nuclei 

 (nurse cells). Von Kemnitz (1912) found that the chief 

 stored nutrient material of ascarid oogonia is glycogen 

 and that this substance is absent from the rachis through- 

 out the germinal region, only making its appearance in 

 that structure after it has become the most conspicuous 

 feature of the oogonium. Von Kemnitz traced the dis- 

 tribution of glycogen in the gonad demonstrating con- 

 clusively that it is first seen in the epithelium of the 

 upper part of the ovary, thereafter, less concentrated in 

 both epithelium and oogonia and finally absent from 

 the epithelium, concentrated in the oogonia and scattered 

 in the rachis. One concludes that it is obtained from 

 the ejjithelium by absorption. Seurat (1920) pointed 

 out that increase in nuclear and plasmatic size in the 

 growth zone is fairly proportionate, which would not be 

 the case if nurse cells or a vitelline tissue were actively 

 contributing plasma to the oogonium. The same author 



139 



