vidual fibei's for descriptive purposes (small numbers 

 opposite fibers). The fibers of the major lateroventral 

 commissure are labelled L 1-12, those of the ventral nerve 

 B 1-31, those of the submedian somatic nerves Subl I-IV, 

 1-4, and a-d. The ordinates and coordinates are also 

 numbered but this is merely for purposes of location. 

 Further discussion seems unnecessary since those inter- 

 ested in the detail may obtain it from the illustrations. 



In O.vyiiris equi Martini (1916) found eight glia cells 

 (ct. in Pig. 130 F) and seven commissural cells corre- 

 sponding to the four described by Goldschmidt for Ascaris. 

 The commissural cells are located: two lateral (cell 10 

 r. 1.), two dorsal (43, 44) and three ventral (39, 40, 41). 

 In Spiyonour<i affine (Fig. 131 J-K) and Oesophagosto- 

 vium dcnttttum (Fig. 132 A-B) we find the same arrange- 

 ment as in Ascaris except that in both forms there is a 

 pair of subventral glia cells on the posterior surface of 

 the nerve ring and in O. dentatiim there is also a dorsal 

 posterior and a ventral anterior glia cell. 



CORSAL AND SUBDORSAL GANGLIA. In Ascaris the dorsal 

 ganglion consists of two central cells (Fig. 130 C) each 

 with two processes to the nerve ring while in Parascaris 

 cqiionan one of these cells has a single process. In the 

 latter species Goldschmidt also saw the posterior dorsal 

 glia cell which we have mentioned on the nerve ring of 

 Oesophagostomnm. The dorsal ganglion of other species 

 also contains two nerve cells which may have a very long 

 central cylinder as in Spironouru; in this case they ap- 

 pear to be located in the dorsal nerve. Possibly this is 

 the reason for our having found only one such ganglion 

 cell in CejihaloheUus and for Martini's not finding a 

 dorsal ganglion in Oxytiris (an extra dorsal commissural 

 cell probably corresponds to one of the dorsal ganglion 

 cells of Ascaris). 



The subdorsal ganglia each consist of two central cells 

 in Ascaris, Spiroiioura, Rhabditis and Oesophagostomum 

 and with it two glia cells are associated in the first two 

 genera but only one in the two last named. Paired 

 posterior subdorsal glia cells in O.ryims and Cephalohellits 

 were attributed to the nerve ring, but they are undoubtedly 

 homologous to those associated with the subdorsal ganglia 

 where such ganglia are present. Casual observation in- 

 dicates that absence of subdorsal ganglia may be char- 

 acteristic of the Thelastomatidae and Oxyuridae. 



Lateral ganglia, Amphids and Associated Struc- 

 tures. In all nemas the lateral ganglia contain the largest 

 number of cells and are so intimately associated with the 

 amphids and deirids that it is easiest to consider them at 

 once. In Ascaris, Goldschmidt found a total of 35 nerve 

 cells while in Oxyuris, Martini found 21, in Cephalobellus, 

 the writers found 26 cells, in Spironoura 42, in Oesopha- 

 gostomum 41 and in Rhabditis 42. 



Postlateral ganglia are absent in Oxyuris and Cephalo- 

 hellits while in Spironoura, Rhabditis and Oesophagosto- 

 mum they are the most clearly set apart. In Spironoura 

 and Oesophagostomum each of these ganglia is composed 

 of two groups of cells. The anterior group consists of two 

 cells, one a sensory cell connected with the deirid, the 

 other a glia cell. The second group consists of five cells 

 all of which have processes into the minor lateroventral 

 commissure. In Rhabditis all seven cells are in one 

 group (Fig. 131 P). 



The postlateral and mediolateral ganglia of Ascaris 

 contain cells corresponding to those found in the post- 

 lateral and mediolateral ganglia of other genera studied 

 but the grouping differs. Since Goldschmidt's grouping 

 in the case of Ascaris is rather artificial, there being 

 no distinct lobes in that species, we shall regroup the 

 cells he described. The internolateral ganglia are in 

 close association with the amphidial ganglia and cannot 

 be grossly distinguished from them. Goldschmidt sub- 

 divided the internolaterals into anterior and posterior 

 lobes, but this division is not practical. Each whole 

 internolateral ganglion contains eleven cells, seven being 

 unipolar with a process to the nerve ring (23-29), three 

 unipolar with a process to the major lateroventral com- 

 missure (30-32) and one (49) tripolar with one process 

 to the nerve ring, one to the ventrolateral nerve and 

 one to the dorsosubmedial nerve. 



In Ascaris the amphidial ganglia (Fig. 130 D) each 

 contain 11 sensory neurones (68-78) connected anteriorly 

 with the amphidial nerve and posteriorly with the major 

 lateroventral commissure. The amphidial gland lies 

 dorsal to the amphidial ganglion and extends anteriad 

 eventually surrounding the amphidial nerve. At this 

 level (slightly posterior to its terminus) the amphidial 



gland duct attains a cuticular lining and is slightly 

 dilated forming the amphidial pouch. Within this struc- 

 tuie there is a sensilla consisting in Ascaris of 11 rod- 

 like sensory terminals (Fig. 130 O). The lumen of the 

 pouch is in direct continuity with a short tube leading 

 to the amphidial pore. 



The externolateral lobes of the lateral ganglia were 

 subdivided by Goldschmidt into three parts, the anterior, 

 medial and posterior parts but since there is no real 

 subdivision (Fig. 130 F) we will describe these struc- 

 tures as a single unit. Each whole ganglion contains 

 13 cells of which eight are unipolar, four have a process 

 to the nerve ring (37, 40, 41, 42), two have a process 

 to the major lateroventral commissure (33, 34) and two 

 have a process to the minor lateroventral commissure 

 (44, 45). The five bipolar neurones have processes as 

 follows: two (38, 43) have processes to the nerve ring 

 and ventrolateral nerve; one (35) has a process to 

 the major lateroventral commissure and another to the 

 lateral nerve; one (39) has a process to the nerve ring 

 (Fig. 130 E) and another to the minor lateroventral 

 commissure (a side branch of this process innervates 

 the deirid); and one (36) has its anterior process to 

 the nerve ring, its posterior process entering the oblique 

 ventrodorsal commissure (right side) or the ventrodorsal 

 commissure II (left side). 



Martini (1916) found only two subdivisions of the lateral 

 ganglia in Oxyvris, these being the dorsal and ventral 

 lobes (Fig. 131 D). The dorsal lobe contains six neurones, 

 three unipolar to the nerve ring (1-3) and three bipolar 

 with one process to the nerve ring and the other to the 

 common root of the laterodorsal, dorso- and mediolateral 

 somatic nerves. The ventral lobe consists of 15 cells, 

 five of which are bipolar, innervating the amphids and 

 passing through the latero-ventral commissure; the latter 

 (9, 15, 16, 22, 26) undoubtedly correspond to Goldschmidt's 

 amphidial ganglion (11 cells in Ascaris). Of the re- 

 maining 10 neurones, two are unipolar to the nerve ring 

 (7-8), one is unipolar to the lateroventral commissure 

 (27), three are bipolar with processes to the ventrolateral 

 somatic nerve and the nerve ring (20, 23, 24) and four 

 are bipolar with processes to the lateroventral commis- 

 sure and the nerve ring. The mediolateral nerve has 

 three neurones in its course, two far back in the body 

 region and one not far distant from the lateral ganglia. 

 The latter might be considered part of the lateral ganglion, 

 possibly representing a rudimentary postlateral lobe. 



The writers (1933) found no marked subdivision but 

 a distinct tendency toward separation of an amphidial 

 and a dorsal lo^be as well as a rudimentary postlateral 

 lobe of the lateral ganglion in Cephalobellus. The chief 

 lobe contained three unipolar cells to the nerve ring (4, 

 12, 17), two unipolar cells to the lateroventral commissure 

 (20, 23), six cells of undetermined character (14, 16, 

 18, 21, 22), and a glia cell (8). The dorsal lobe con- 

 tained two unipolar cells to the nerve ring (6, 7) and 

 three bipolar cells to the nerve ring and dor- 

 sosubmedian lateral nerve trunk. The amphidial lobe 

 contained eight bipolar cells to the lateroventral com- 

 missure and amphid (13, 19, 24-28, N). The postlateral 

 lobe contained two neurones (29, 30) attached to the 

 lateral nerve. 



In Spironoura there is a very distinct division of the 

 lateral ganglia into anterior and posterior lobes, the 

 anterior lobe containing 35, the posterior lobe seven 

 cells. In the anterior lobe subdivision is indistinct. The 

 courses of only part of the cells have been traced; of 

 these six are unipolar direct central cells, seven are uni- 

 polar cells entering the major lateroventral commissure, 

 eight dorsolateral cells are connected with the dorsosub- 

 median and lateral nerve trunk and eight are connected 

 with the amphidial nerve and lateroventral commissure. 

 The amphidial glands (Fig. 131 J) are particularly 

 massive in this form. In the postlateral ganglion only 

 six of the cells are neurones, the seventh being the glia 

 cell of the deirid. At least three, possibly four neurones 

 are bipolar with anterior processes in the lateral nerve 

 and posterior processes through the minor lateroventral 

 commissure (one of these has a branch to the deirid) ; 

 another of the cells is bipolar with one process anterior 

 and another posteriad entering the latei'al nerve, while 

 the sixth appears to be tripolar, with two processes enter- 

 ing the lateral nerve and a third the dorsolateral com- 

 missure. 



167 



