In Oesophagostomum and Rhabditis practically the 

 same subdivision of the lateral ganglia (seven cells in 

 postlaterals) has been observed except that in Oesopha- 

 gostomum the dorsoventral commissure originates vdth 

 the dorsosubmedian nerve. 



Metoncholaimus pristiurus (Fig. 131 D) is the only 

 aphasmidian that we have casually studied and no exact 

 information is available. However, considering Filipjev's 

 (1912, 1934) indication that the nervous system is basic- 

 ally different in aphasmidians it is interesting to note 

 the same general arrangement in the lateral ganglion 

 with many cells entering the lateroventral commissure. 

 The cells are not so closely packed but there is no other 

 obvious difference. 



Ventral Ganglion. In Ascaris the ventral ganglion 

 (Fig. 130 A) is bilobed and contains 33 cells of which 

 15 are paired and three unpaired, cell 16 being medial 

 (on right side in figure) and cells 17 and 18 on the right 

 side. All e.xcept two cells are unipolar and the bipolar 

 exceptions innervate the lateroventral somatic nerves. In 

 Oxyuris the ventral ganglion is definitely paired, there 

 being two groups of eight cells (31-38 r. 1.) making a 

 total of 16. The two extra ventral commissural cells 

 of the nerve ring in this species probably correspond 

 to two unipolar ventral ganglion cells in Ascaris; even 

 so, only 18 ventral ganglion cells would have been 

 accounted for and this is a marked reduction from 33. 

 In Cephalobelhis there are likewise eight pairs of cells 

 but there is also a medioventral cell making 17 in all; 

 one cell in each lobe is bipolar as in Ascaris. In Spiron- 

 oura the partly bilobed ventral ganglion contains 29 

 neurones while in Oesophagostomum and Rhabditis 30 

 and 33 neurones were observed. In the latter instance 

 the ventral ganglion is rather distinctly paired and also 

 subdivided transversely into anterior and posterior lobes; 

 each posterior lobe contains four cells (Fig. 131 Q). 



Retrovesicular Ganglion. The retrovesicular ganglion 

 in Ascaris contains 13 bipolar cells (79-91), several of 

 which are in direct continuity with one another (Fig. 

 130 J) forming an associational center according to 

 Goldschmidt (1908). In Oxyuris, Martini found the 

 same number of cells in this ganglion as did the writers 

 in Cephalobelhis. In Oesophagostomum. the retrovesicular 

 ganglion consists of 13 cells (Fig. 132 A) followed so 

 closely by a postretrovesicular ganglion of seven cells 

 that sometimes they seem about to merge. This has 

 apparently taken place in Spironoura where the retroves- 

 icular ganglion is unusually far back and contains 20 

 cells. In Rhabditis the ganglia (Fig. 131 I) are also 

 merged, there being 21 cells. 



Anal, Lumbab and Genital Ganglia and Sensory 

 Organs. In Ascaris these structures have not been very 

 well studied though investigated by Hesse (1892), Volt- 

 zenlogel (1902) Goldschmidt (1903) and Deineka (1908). 

 Each preanal genital papilla of the paired series is 

 connected by means of a fiber (which passes through 

 the hypodermis) to the ventrolateral nerve where a 

 sensory neurone and a glia cell are situated. The fibers 

 then pass posteriad in the ventrolateral nerve before 

 reaching the genito-papillary commissures through which 

 they reach the ventral nerve. (Fig. 128 C). The anal 

 ganglion which terminates the ventral nerve contains 

 seven cells; the number of cells in the lumbar ganglia 

 has not been determined. According to Voltzenlogel 

 the medioventral preanal papilla is innervated by a 

 process direct from the anal ganglion, this process con- 

 taining four neurones. On each side of this process a 

 branch of the ventral nerve extends posteriad and just 

 anterior to the anus both branches bend dorsally forming 

 the ano-lumbar commissures which connect the ganglia 

 of the same names. Voltzenlogel found that both the 



Fig. 132. 

 A-B — Oesophagostomuiii dentatum (A — Dissection showing ven- 

 tral and lateral ganglia with nerve trunks ; B — Dissection show- 

 ing dorsal and subdorsal ganglia). C-D — Spironoura afjine (Re- 

 construction of posterior part o£ nervous system. C — Male ; D — Fe- 

 male). E — Rhahditis terricola (Longitudinal section of female 

 showing phasmidial gland). F-L — Spironoura affine (F — Longi- 

 tudinal reconstruction of phasmids showing phasmidial glands, 

 nouroncs and glia cells ; G — Longitudinal section showing innerva- 

 tion of preanal median papilla ; H — Same papilla in transverse 

 section : I — Genital papilla ; J — Deirid ; K — Reconstruction of cross 

 sections of female at level of phasmids ; Tj — Reconstruction of 

 cross sections of male showing spicular ganglia and rectal com- 

 missure). M — Oxyuris eqtfi (Dissection showing connection of 

 innervation processes with median nerves). N — OesdphUgOstomum 

 fjrntatum (Branch of dorsal rny). M, after Martini, 1916, ZtBChr. 

 Wiss. Zool., V. 116. Remainder original. 



dorsal and medio-caudal nerves divide at the level of 

 the lumbar ganglia, a process passing on each side to 

 the corresponding lumbar ganglion. From these ganglia, 

 the laterocaudal nerves extend posteriad. In all, there 

 are seven pairs of postanal sensory organs in the male; 

 the first four form two pairs of double subventral papillae, 

 one pair anterior and one posterior to the lumbar gang- 

 lion. The fifth pair, more laterally situated and ex- 

 ternally pore-like rather than papilloid, is the phasmid; 

 the sixth and seventh pairs are both typical simple papil- 

 lae. Anterior to the last pair the laterocaudal nerves 

 each contain three neurones. All of the postanal sensory 

 organs are innervated by processes from the laterocaudal 

 nerves. 



In Ancylostoma Looss found the anal ganglion longi- 

 tudinally divided in both sexes. In the female the ano- 

 lumbar commissures join the paired anal and lumbar 

 ganglia from which ventrolateral caudal nerves extend 

 posteriad to innervate the phasmids; just anterior to 

 this point the dorsolateral nerves join the ventrolateral. 

 In the male (Fig. 130 BB) the ganglia are essentially 

 similar but the anal ganglia are each subdivided into 

 two parts (antero-anal and postero-anal ganglia) and 

 the lumbar ganglia each into three subdivisions (pro- 

 lumbar, mesolumbar and metalumbar parts correspond- 

 ing to lumbar, postlumbar and costal as named by 

 Looss). Two ano-lumbar commissures join the sub- 

 divided anal ganglia with the two anterior subdivisions 

 of the lumbar ganglia. In Ancylostoma, as in other 

 strongyloids, all except one pair of genital papillae are 

 situated in the bursa and terminate its rays. The pre- 

 bursal papillae are the exceptions and they are innervated 

 by processes extending directly from the second ano- 

 lumbar commissure. The typical strongyloid (Fig. 33 

 I-J) bursal ray pattern consists of five bursal ray trunks, 

 two ventral, two lateral and a single dorsal. Each ven- 

 tral trunk bifurcates forming a ventroventral and a latero- 

 ventral ray; each lateral trunk trifurcates forming an 

 externolateral (ventrolateral), mediolateral and post- 

 erolateral (dorsolateral) ray while the dorsal gives off 

 two lateral branches, the externodorsal rays, and then 

 bifurcates, forming, the two dorsal rays. Each of the 

 dorsal rays terminates in two or three digitations. Since 

 the dorsal trunk contains the remnants of the lateral 

 and ventral chords as well as the somatic muscles, it 

 corresponds to the tail of the female. It is not really 

 dorsal, but terminal. Looss found that all the larger 

 bursal rays terminate in papillae. The ventral trunks 

 are innervated by a pair of nerves from the second ano- 

 lumbar commissure; a branch from each nerve extends 

 out to the tip of each ray. A nerve extends posteriad 

 from each metalumbar ganglion and divides into three 

 branches, one to each of the lateral rays, where they 

 terminate as papillae, while another nerve extends medially 

 from each metalumbar ganglion to the trunk of the 

 dorsal ray, where it gives off a lateral branch into the 

 externodorsal ray before terminating in the correspond- 

 ino- medial digitation of the dorsal ray. The papillae 

 of the externolateral and externodorsal rays are situated 

 on the dorsal side of the bursa while the remaining 

 papillae protrude on the ventral side of the bursa. In 

 both Strongylus (with tridigitate dorsal rays) and Oesoph- 

 agostomum (with bidigitate dorsal rays) we have found 

 three pairs of papillae on each dorsal ray. There is a 

 papilla for each digitation in the former genus while 

 there is one papilla on each lateral and two on each 

 medial branch in the latter genus (Fig. 132 N). With 

 Looss, we conclude that in the male bursa the most 

 medial digitation of the strongyloid dorsal ray is the 

 homologue" of the phasmid or "caudal papilla" of the 

 female. Including the prebursal papillae there are 10 

 pairs of sensory organs in male strongyloids; this is also 

 true for Rhabditis strongyloides (Fig. 4) R. caussanelh 

 (Fig. 33 A) and R. aspera (Fig. 33 B-C). In R. strongy- 

 loides all sensory organs are papilloid while in R. caus- 

 saneUi and R. aspera the tenth sensory organ (phasmid) 

 is pore-like. Some of the genital papillae in rhabditids 

 always end on the dorsal or outer side of the bursa; 

 the particular ones vary with the species. In two or 

 three species, such as Rhabditis oxyuris the first pair of 

 papillae is prebursal as in the strongyloids. In order to 

 find a comparable arrangement of bursal papillae m 

 rhabditids we must number the strongyloid papillae from 

 the anterior end as follows: prebursal— 1, ventroventral-— 

 2, lateroventral— 3, externolateral— 4, mediolateral— 5, 



169 



