Chitwood (1933) have enumei-ated the cells found in the 

 ventral nerve between the retrovesicular ganglion and the 

 posterior prcanal ganglion but neither found sufficiently 

 clear grouping of the cells to warrant establishment of a 

 series of named ganglia; comparing their work with the 

 situation in Spifonoura (Fig. 132 D) we find that there 

 are 25-30 neurones of which a group of 6-7 form a post- 

 vulvar ganglion, that sometimes there is a more or less 

 distinct prevulvar ganglion and that other neurones may 

 or may not be grouped. Looss found a vaginal nerve, 

 originating from the pre\'ulvar ganglion, which forms a 

 commissux-e around the vagina at its juncture with the 

 uteri. The same author also described paired anal nerves 

 originating in the paired preanal ganglia and extending 

 posteriad to the anterior lip of the anus (Fig. 130 AA). 

 At the preanal ganglion the ventral nerve is double in 

 Ancylostoma duodenale , Oxyuris equi and Rhabditis terri- 

 cola. The apparent doubleness in both anterior and posteri- 

 or ends of the ventral nerve caused Meissner and many 

 later authors to conclude that the entire ventral nerve 

 was at one time double. Arguments against this view 

 have been based on the fact that in most nemas studied 

 the ventral nerve goes to the right of the vulva instead of 

 dividing to go around it. ' Oxyuris equi is a conspicuous 

 exception in this latter respect but here it might be 

 argued that the vulva is shifted anteriad. As Looss 

 pointed out, the asymmetric vulvar by-pass is to be 

 expected in developmental anatomy since the ventral 

 nerve is already in position when the vulva is formed. 

 The writers subscribe to the primitive double ventral 

 nerve hypothesis. 



The ventral ganglia are each transversely lobed in 

 Siphonolaimus, Hexamermis, and Rhabditis the smaller 

 lobes being called the postventral ganglia, the term 

 ventral ganglia being i-eserved for the anterior lobes. 

 In other nemas studied, the ventral ganglia are not sub- 

 divided. 



The lateral ganglia are more or less lobed in all nemas, 

 but in none thus far studied are they subdivided into 

 as many parts as in Ascaris. As a general rule there is 

 a lobe forming the dorsolateral ganglion connected with 

 the nerve ring near the origin of the laterodorsal and 

 dorsolateral somatic nerves. The term lateral ganglion 

 is reserved for the major part of the lateral ganglion 

 while a posterior lobe, the postlateral ganglion is some 

 distance from the major ganglion group; it connects an- 

 teriorly and posteriorly with the ventrolateral somatic 

 nerve and ventrally with the minor lateroventral com- 

 missure. 



So7natic Nerves. The dorsal somatic nerve and ventro- 

 lateral somatic nerves in the genera studied are similar 

 to those of Asearis with the exceptions that in Camallanus 

 and Cucullanus Tornquist identified several nerve cells 

 in the course of the dorsal nerve and in those forms 

 without deirids {Oxyuris, Hexamermis, Cepkalohellus and 

 Siphonolai)iius) the ventrolateral nerve has no branch 

 to the surface. A dorsolateral nerve has been seen only 

 in Ancylostoma and Oxyuris and submedian somatic nerves 

 in Cepkalohellus, Spironoura, Rhabditis, Hexarnerinis and 

 Oesophagostomuni. Numerous dorsoventral commissures, 

 such as Hesse describes in Ascaris have not been seen in 

 any of the other forms studied. The two anterior latero- 

 ventral commissures, the rectal and anal commissures 

 are the only ones known to be generally existent. 



Cephalic papillary nerves and papillae. There are 

 always six cephalic nerves connected posteriad with six 

 papillary ganglia and anteriad with six groups of papil- 

 lae. Tornquist (1931) observed these nerves and ganglia 

 but was unable to find the lateral cephalic papillary 

 group and confused the fibers and ganglia with the 

 amphidial nerve and lateral ganglia respectively. The 

 papillae have been previously described (pp. 55-64) in 

 these and other forms so t?iat there is no need of re- 

 peating the discussion here. We need only call to the 

 readers' attention that there are primarily three papillae 

 in each submedian group and two in each lateral group. 

 Among parasitic phasmidians there is a general tend- 

 ency for the internal circle of papillae to become reduced 

 or rudimentary. There is also a tendency toward re- 

 duction of the external circle either through reduction 

 of the externomedial papillae or through the joining of 

 the lateromedial papillae. The ventrolateral papillae may 

 or may not become reduced or rudimentary coincident 

 with reduction of the mediomedials. 



Amphidial nerves and amphids are fundamentally like 

 those of Ascaris in all forms. 



Enumerative and Minute Anatomy 



Cephalic papillary ganglia, nerves, papillae 

 AND associated CELLS. Goldschmidt (1903) worked out 

 the cephalic papillary nervous system of Ascaris along 

 with the non-nervous cells of the anterior end. We have 

 already discussed many of the non-nervous cells (p. 37) 

 but because of their rather intimate association with the 

 papillary nerves some repetition will be necessary. 



Arcade Cells. These are apparently hypodermal cells of 

 the stomatal and labial regions. Nine such cells have 

 been found in Ascaris (Goldschmidt, 1903, and Hoeppli, 

 1925), Oxyuris (Martini, 1916), Strongylus (Imminck, 

 1924), Cephalobellus (Chitwood & Chitwood, 1933), and 

 Rhabditis, Spironoura and Oesophagostomuni (this publi- 

 cation). They are not connected in any way with the 

 nervous system but must be distinguished from it. In 

 all except Strongylus, Oesophagostomuni and Spironoura 

 they take the form of elongate, posteriorly directed cells 

 united anteriad in a transverse plate opposite the base 

 of the labial region. Their cell bodies ai-e closely applied 

 to the esophageal surface, distributed as follows: one 

 dorsal, four dorsolateral, two ventrolateral and two ven- 

 tral (Fig. 46 A-B). In Stroyigylus (Fig. 46 E) they are 

 distributed in the same pattern but are confined to the 

 stomatal region and take the form of three protoplasmic 

 bands. In Oesophagostomuni they are situated in the 

 body cavity but at the level of its nucleus each cell has 

 a process inserting it into the hypodermis next to the 

 chord with which it is associated. There are two sub- 

 dorsal arcade cells beside the dorsal chord, one dorsolateral 

 on the left side and two on the right side next to the 

 lateral chord, one on each side ventrolateral next to the 

 lateral chords and two subventral on the right side of 

 the ventral chord. In Spironoura the arrangement is more 

 nearly typical but instead of there being four dorsolateral 

 and two ventrolateral there are two dorsolateral and 

 four ventrolateral. 



Non-specific Connective tissue. There may be several 

 types of connective tissue cells not associated with the 

 nervous system but situated in the body cavity around 

 the esophagus. In Ascaris Goldschmidt listed three fibril 

 cells opposite the three esophageal radii and two "Fiill- 

 zellen" (left dorsolateral and subventral) and in Oxyuris 

 Martini listed three "Bindegewebe" cells, one dorsal and 

 two ventrolateral, in addition to those already mentioned. 

 In Oesophagostomum the three fibril cells have been 

 observed but other cells could not be identified. 



Submedian Papillary Ganglia, Nerves and Papillae. In 

 Ascaris Goldschmidt (1903, 1908) found each of these 

 ganglia to be composed of seven bipolar sensory neurones 

 (Cells 50-56 times 2, subventral, and cells 57-63 times 2 

 subdorsal. Fig. 130 G) . Posteriad a process from each 

 cell enters the nerve ring while anteriad they come to- 

 gether forming the submedian papillary nerves. In 

 addition to the nerve processes a glia process enters the 

 corresponding nerve from each of the four giant glia 

 cells situated on the anterior surface of the nerve ring 

 (Fig. 130 C). 



Anteriorly the processes of four of the neurones stop 

 in the postlabial region while the other three innervate 

 papillae. The fiber innervating each lateromedian papil- 

 la (laterodorsal or lateroventral) anteriad becomes en- 

 sheathed by the glia process from the corresponding glia 

 cell on the nerve ring and this is in turn partially sur- 

 rounded by an escort cell, the two together forming the 

 papillary mass. At its termination the cuticle has a 

 very deep invagination from which a fine sensory hair 

 projects; the hair is continuous with the dendritic process 

 of the nerve (Fig. 130 L). The medio-medial papillae are 

 each formed by a glia and escort cell; in this case the 

 nucleus of the glia cell (Fig. 130 P) is some distance 

 anterior to the nerve ring. The sensory terminus differs 

 from that of the lateromedial papilla in that it ends under 

 the surface in a sensory plate or receptaculum (Fig. 130 

 L). A clavate cell accompanies each of the submedian 

 papillary nerves but is not associated with either of the 

 processes to the external circle of papillae; it may, 

 perhaps, act as an escort cell of the fiber to the interno- 

 medial papilla. This papilla is greatly reduced in Ascaris; 

 Hoeppli (1925) described a special glia cell for this struc- 

 ture. The clavate cell acts as its escort cell. 



In Oxyuris, Martini (1916) found three neurones (Cells 

 50-52 times 2 in Fig. 131 B) in each subdorsal papillary 



163 



