posteriolateral — 6, externodorsal — 7, laterodorsal (digi- 

 tation) — 8, subdorsal (digitation) — 9, dorsodorsal (digi- 

 tation)— 10 (= phasmid). Thus, the fourth and seventh 

 papillae terminate on the dorsal side of the bursa. The 

 similarly numbered papillae terminate dorsally in Rhab- 

 ditis strongyloides; in addition the ninth (or tenth, de- 

 pending on relative position) is also dorsal in this 

 species; presumably it is the phasmid. The lumbar 

 ganglia are not subdivided in rhabditids as they are in 

 strongyloids. 



In Spironoura the ventral ganglion is undivided and 

 contains nine cells in the female (Fig. 132 D) and 27 

 in the male (Fig. 132 C). The lumbar ganglia contain 

 six neurones on the right side and five on the left 

 side; of these the first cell is somewhat removed from 

 the remainder. The ano-lumbar commissures are ap- 

 proximately adanal in position connecting with the an- 

 terior part of the lumbar ganglia. From the posterior 

 end of the lumbar ganglia the lateral caudal nerves 

 e.xtend posteriad and each contains a bipolar neurone 

 before passing through the phasmidial ganglion from 

 which fibers pass to the phasmidial gland. Posterior 

 to this ganglion the lateral caudal nerves extend nearly 

 to the caudal extremity. In the male of this form the 

 ano-lumbar commissure is decidedly preanal and there 

 is a medioventral process originating with it, containing 

 a bipolar neurone connected with the medioventral pre- 

 anal papilla (Fig. 132 G). Each prolumbar ganglion 

 contains five neurones, one slightly anterior, which is 

 connected with the recto-sympathetic system. In the 

 course of the ventrolateral nerves anterior to the pro- 

 lumbar ganglia, there are three neurones in each nerve 

 from which a like number of nerve processes extend to 

 the three pairs of preanal genital papillae. No genital 

 commissures to the ventral nerve were observed, so we 

 presume the axones of the three neurones pass posteriad 

 and reach the ventral nei-ve through the ano-lumbar 

 commissure. If this is the case, the distantly placed 

 sensory cells might be regarded as part of the prolumbar 

 ganglia. Postanally there are two pairs of nerve cell 

 groups, the mesolumbar and metalumbar ganglia in ad- 

 dition to the phasmidial ganglia. Processes from the 

 mesolumbars innervate the fourth to seventh pairs of 

 genital papillae while processes from the metalumbars 

 innervate the eighth to tenth pairs. 



Regarding the general arrangement of genital papillae 

 in nemas one's attention is called to two standard forms 

 in the Phasmidia. In the first there is a very definite 

 grouping of papillae as in strongyloids and rhabditoids; 

 it probably reflects the triple division of the lumbar 

 ganglia. Postanal papillae number up to seven or eight 

 pairs including the phasmids. Preanal papillae num- 

 ber two to three pairs. In the second standard form the 

 postanal papillae are not so clearly grouped and there 

 are many more serially arranged preanal papillae, a.s in 

 Ascaris; this linear formation is due to reduplication and 

 probably arose from a form such as Spironoura in which 

 the preanal papillary neurones are separated some dis- 

 tance from the prolumbar ganglion. The oxyurid-thelas- 

 tomatid arrangement, in which ther.e ai-e but four pairs 

 of papillae besides the phasmids, may be considered a 

 reduction of the rhabditid scheme. A medio-ventral 

 pi-eanal papilla, innervated directly from the ventral 

 nerve, was described in Ascaris and Spiroiwura; a com- 

 parable papilla is present in a large number of other 

 phasmidian nemas and may even be general; one is 

 recorded in Strongyloides, Rhabditis, Physaloptera and 

 we have seen it in Oesophagostonmm. The medioventral 

 papilla of the pi-eanal sucker in Heterakix (Fig. 33 P) 

 might also be the same structure. We regard it as a 

 probable homologue of the preanal supplementary organs 

 (See p. 29) in aphasmidians. 



Phasmids and Associated Structures. Since our 

 (1933) proposal of the divisions Phasmidia and Aphas- 

 midia, parasitologists have been much perturbed by these 

 "mysterious organs." They are nothing other than the 

 "caudal papillae" as seen in the larvae and females of 

 most parasitic nemas. Because of their differences from 

 ordinary sensory papillae Cobb (1923) proposed the 

 name phasmid (= ghost thing) for them. Their external 

 manifestation is a pair of lateral or subventral pores. 

 From each of these a short tube extends internally and 

 in it lies the sensilla which is very similar to that of the 

 amphid except that its elements or terminals are fewer 

 in number. Like the amphids, the phasmids are usually 

 (? always) provided with a flushing gland, the phas- 



midial gland. In the Phasmidia, our experience indi- 

 cates that the phasmids are always present in larvae and 

 females. They are sometimes transformed into plate-like 

 scutella (Rotylenchus hlaberu.-< vide Steiner, 1937) and 

 sometimes they take the form of large pockets as in larval 

 dracunculoids and drilonematids (Dicelis nira) . In the 

 male, they are often difficult to distinguish from genital 

 papillae or they may be so faint that they are truly 

 ghost-like. In most rhabditids, cephalobids, diplogasterids, 

 oxyurids and thelastomatids they are easily enough rec- 

 ognized and were called excretory glands by Stefanski 

 (1922). In ma'e spiruroids and dra.unculoids they 

 are very minute. Only in the males of a few rhabditids 

 (/?. strongyloiden) and all strongylins are the phasmids 

 grossly indistinguishable from genital papillae and we 

 have seen (p. 169) that in these casss they are probably 

 represented by the most posterior papilla or dorsodorsal 

 digit of the dorsal ray. In Oesophagostomu}n it appears 

 that this structure terminates \n a pore as in typical 

 phasmids. 



The minute structure of these organs has been sorely 

 neglected. Looss (1905) found them to be innervated 

 by the lateral caudal nerves in Anci/lostouia. Chitwood 

 (1930) described the phasmidial gland and mentioned the 

 observation of bipolar neurones ending in a sensory ter- 

 minus within the phasmidial tube of Rhabditis, and the 

 writers (1933) confirmed this finding in Cephalobellus. 

 The illustration (Fig. 8) of the general situation in 

 Rhabditis terricola is the only other information extant. 



The writers have selected Spironoura for detailed study 

 because it is optimum in size for histological work. 

 Similar studies on free-living nemas are difficult; section 

 and intravitam preparations, though beautiful, require 

 confirmation because they are apt to be confusing. The 

 errors of Deineka (1908) and Chitwood (1930) with 

 methylene blue on the central nervous system make the 

 description of an organ by section obligatory in at least 

 one species before the use of intravitam staining methods 

 for comparative purposes. 



In the female of Spironoura each phasmid (Fig. 132 

 F & K) opens to the outside through a small postanal 

 lateral phasmidial pore. From this pore a cuticularly 

 lined canal extends inward and disappears in a large 

 phasmidial gland. In the wall of the phasmidial canal 

 there are two glia cells. The phasmidial ganglia each 

 contains three neurcnes and one glia cell; processes from 

 at least two of these enter the phasmidial gland where 

 they form sensory terminals. The male has phasmids 

 which are similar but the phasmidial ganglia each con- 

 tains five neurones. In both sexes axones from these 

 neurcnes pass anteriad through the lateral caudal nerves 

 to the ano-lumbar commissures. 



In rhabditids (Fig. 8 & 132 E) the phasmidial glands 

 have the same general arrangement as in Spironoura 

 but there is no separation between the lumbar and phas- 

 midial ganglia. 



Recto-Sympathetic System. This part of the nervous 

 system received casual attention by Hesse (1892) and 

 Voltzenlogel (1902) in Ascarni, by Looss (1905) in An- 

 cylostoma duodciiale, by Martini (1906) in O.ryuris equi, 

 and by the writers (1933) in Cephalobellus papilliger. 

 Diagrams have, for the most part, been inadequate. 

 Our observations on Sjiiro7ioura affine indicate that tbere 

 is probably considerable yet to be learned. The condi- 

 tion in the female of Spironoura seems to be quite simple 

 (Fig. 132 D), since it apparently consists merely of a 

 pair of commissures meeting dorsally and extending 

 posteriad in the median caudal nerve. The latfer con- 

 tains two neurones dorsal to the rectum and two addi- 

 tional neurones in its postanal course. In the male of 

 this form, the system is much more complex. In the 

 course of each of the two ano-rectal commissures there 

 are two bipolar neurones ventral to the cloaca (rcl-2 

 and rc3-4). As in the female, the commissures meet 

 dorsally, forming the medial caudal nerve, but in its 

 course there are three dorsocloacal neurones and four 

 postanal neurones (Figs. 132 C & L). Laterally each 

 ano-rectal commissure gives off a branch which joins 

 the laterally situated spicidar ganglion which contains 

 four neurones and a glia cell. Two of these neui'ones 

 have processes into the spicular sheath and two have 

 processes to the medial caudal nerve (in the ano-rectal 

 commissure). Two processes from each of these ganglia 

 pass posteriorly and ventrally to two bipolar suhcloacal 

 nom'ones which extend toward the anterior tloacal lip. 



170 



