ganglion and two glia cells (Cells 53 times 2 and ct. "T-S 

 in Fig. 131 B) disposed in the same manner as the glia 

 cells of Ascuris. The cell whose fiber enters the nerve 

 ring between the other two (Cells 52) becomes sur- 

 rounded anteriorly by the clavate cell and then termi- 

 nates as an internomedial papilla; no glia cell is asso- 

 ciated with it. The cell whose fiber enters the nerve 

 ring most laterally (Cell 50) retains this position through- 

 out its course, becoming associated first with the glia 

 cell (Cell 53), then the escort cell (Hiigelzelle), all three 

 together then forming the large laterodorsal papilla. 

 The cell whose fiber enters the nerve ring most dorsally 

 is probably supplied by glia tissue from the cell on the 

 nerve ring (Ct. 7-8) for no other glia or escort cells are 

 associated with it. It cerminates under the cuticle as 

 the rudimentary dorsodorsal papilla. The subventral 

 papillary ganglia are similar to the subdorsal except 

 that there are two cells connected with the ventroventral 

 rudimentary papillae; one of these might be a glia cell. 



In Spironoiifa we have found five bipolar neurones in 

 each of the subdorsal and subventral papillary ganglia. 

 With these, three glia and four escort cells are associated. 

 In addition a submedian glia cell at the surface of the 

 nerve ring also has a process into each nerve. Three 

 of the neurones with corresponding glia and escort 

 cells form the three well developed papillae in which 

 each of these nerves terminate. The ultimate destina- 

 tion of the two other neurones and the extra glia and 

 escort cells is unknown. In addition to the neurones 

 just described each subventral nerve receives processes 

 from two bipolar neurones in the region of the lateral 

 papillary ganglia (Fig. 131 J) ; presumably they in- 

 nervate the esophago-sympathetic system. 



In Oesophagostomum each subdorsal papillary ganglion 

 contains only four bipolar neurones while the subventral 

 contain five. (Fig. 132 A). As in Spinonojira seven cells 

 in addition to the anterior glia cell of the nerve ring are 

 associated with each papillary nerve, three glia cells 

 and four escort cells. Anteriorly each nerve terminates 

 in a reduced papilla of the internal circle and a conoid 

 (dou'ble) papilla of the external circle (Fig. 129 B). 



Lateral papillary ganglia. In Ascaris, Goldschmidt 

 (1903, 1908) found four bipolar neurones (Fig. 130 D 

 Cells 64-67), one glia cell, one escort cell and one clavate 

 cell. Two of these neurones (Cells 66-67) innervate 

 the ventrolateral papilla but only one is surrounded by 

 the glia and escort cells. The most ventral cell (66) 

 is the one surrounded by glia and forms the bulk of the 

 sense organ; it ends in a plate or receptaculum (Fig. 

 130 K) like those of the medial papillae. The other 

 fiber (67) ends under the cuticle without any special 

 sensory terminus and must, therefore, be considered 

 rudimentary. The most anterior cell (64) becomes 

 associated with the clavate cell and presumably innervates 

 the greatly reduced internolateral papilla. 



In Oxyxiris, Martini (1916) recorded four bipolar neu- 

 rones (Fig. 131 D) connected with the nerve ring, in 

 each of the lateral papillary ganglia (Cells 11, 14, 18 

 and 19); with these cells two glia cells (12 and 17) and 

 one clavate cell are associated. The most ventral of 

 the.se (19) is probably supported by the corresponding 

 glia cell (17) ; it terminates anteriorly under the cuticle 

 as the rudimentary ventrolateral papilla. The most 

 dorsal (11) is associated with the glia cell (12) and the 

 clavate cell and terminates anteriad as the greatly re- 

 duced internolateral papilla. 



In Spironoiira there are likewise four bipolar neurones 

 (Fig. 131 K) in the lateral papillary nerve but in addition 



two glia and three escort cells were ol).served. The most 

 dorsal neurone innervates the internolateral papilla and 

 is associated with the most anterior glia and escort cells 

 while the most ventral neurone innervates the well de- 

 veloped ventrolateral papilla and is associated with the 

 other glia cell and at least one of the escort cells. The 

 lateral papillary ganglia of Oesophagostomum. contain 

 only three bipolar neurones which become associated with 

 two glia and no escort cells. The nerve innervates the 

 greatly reduced internolateral and rudimentary ventro- 

 lateral papillae. 



It seems obvious from the comparative anatomy that 

 escort cells (including clavate cells) are definitely cor- 

 related with papilla formation. In Ascaris and Oxyuris 

 the number of such cells associated with each nerve is the 

 same as the number of papillae reaching the body sur- 

 face, for the lateral nerve two in Ascaris and one in 

 Oxyuris and for the submedian nerves three in Ascaris 

 and two in Oxyuris. In Oesophagostomum there are none 

 laterally and no distinct papillae. However the submedian 

 nerves of both Spironoura and Oesophagostomum have 

 four escort cells, though there are but three papillae in 

 Spironoura and one very large papilla in Oesophagosto- 

 mum. We have previously seen (p. 56) that the large 

 conoid papillae of Oesophagostomum are double; in addi- 

 tion we have found a small internomedial papilla. This 

 would leave one escort cell unaccounted for in both 

 Spironoura and Oesophagostomum. The reason for vari- 

 ability in number of glia cells is not apparent, neither is 

 the variation in the number of neurones. Three neurones 

 are required for papillary innervation and these are al- 

 ways present, even in the lateral nerve. If we may judge 

 by Goldschmidt's work on the ventrolateral papilla (Fig. 

 130 K) we cannot help but conclude that a dorsolateral 

 papilla (homologous to the lateromedial papillae) was 

 present in ancestral forms. The additional cell in the 

 subventral ganglia of Oesophagostomum probably con- 

 nects with the esophago-sympathetic system; the cells 

 which have this function in the other genera studied 

 have been omitted from the descriptions. The neurones 

 not connected with papillae in Ascaris and Spironoura 

 must end in the lip tissues. 



Nerve Ring. The nerve ring is an associational structure 

 where processes from the many ganglia of the central 

 nervous system come into direct lelationships with one 

 another. Goldschmidt believed its primary function was 

 to correlate motor impulses entering the various motor 

 nerves but he did not preclude the association of sensory 

 impulses. 



In Ascaris there are eight cells which must be classified 

 as cells of the nerve ring. Four of these are the anterior 

 glia cells which send processes into the submedian papil- 

 lary nerves. The other four cells, numbered 46 (paired 

 lateral), 47 (unpaired dorsal) and 48 (unpaired ventral) 

 are associational neurones (Fig. 130 I). These four cells 

 have direct continuity with each other and with various 

 motor neurones, with motor nerves and with commissural 

 cells of the lateral ganglia. Several of the unipolar 

 central cells (21, 27, 29) were found to divide after 

 entering the nerve ring, having one process dorsad, the 

 other ventrad (Fig. 134). Goldschmidt reconstructed 

 portions of the dorsal, ventral, and lateral areas of the 

 nerve ring (Fig. 133, 134) showing the direct anasto- 

 moses of many of the fibers. However, he was able to 

 identify particular fibers with cells only in some in- 

 stances (those labelled Z 21 etc.) in which the number 

 corresponds to the cell number given in other illustra- 

 tions. In other instances he merely numbered the indi- 



Fig. 130. 



Details of nervous system. A-Z — Ascaris lujiihricoides (except 

 K-Q, Parascaris equorum). (A — Ventral ganglion; B — Dorsal gang- 

 lion : C — Subventral cephalic papillary ganglion ; D — Amphidlal 

 and internal lobes of Ip.teral ganglion ; E — Diagrammatic repre- 

 sentation of the tripolar neurones from which fibers of the 

 laterodorsal (49) and the lateroventral somatic nerves originate; 

 F — External lobe of lateral ganglion ; G — General dissection of 

 central nervous system as seen from inside, ventral chord median ; 

 H — Subdorsal ganglion (Glia cells white) ; 1 — Diagram of com- 

 missural connections of nerve ring (47 dorsal), lines posterior 

 connect with innervation processes and somatic nerves ; J — Cells 

 80, 86, 87 and 88 of the retrovesicular ganglion showing cells in 

 direct continuity ; K — Ventrolateral pajiilla showing two nerve 

 endings, upper one forming standard papilla, lower one rudi- 

 mentary ; actually the lower is supposed to represent the rudi- 

 mentary dorsolateral, the upper the well developed ventrolateral ; 

 L — Submedian double papilla, laterodorsal to readers' right, dorso- 

 dorsal to readers' left (with receptaculum in white) ; M — Latero- 

 dorsal papillae showing sensory plate, only plate and terminus 



seen in L ; N^Plate of laterodorsal papilla ; O — Amphidial pouch 

 and sensilla : P — Dorsodorsal papilla and associated cells; Q — 

 Laterodorsal papilla and associated cells ; R— Cell 46, showing 

 glia capsule ; S — Cell 51, showing neurofibril ; T — Cell 25, showing 

 radial network and neurofibrillar basket ; U — Cell 67, showing 

 neurofibrillar network ; V — Cell 23, showing glia fibrils entering 

 protoplasm ; W — Cell 24, glia cell of nerve ring ; X — Ventral 

 nerve with innervation processes, methylene blue ; Y — Ventral 

 nerve with insertion of neurofibrils from innervation process ; Z — 

 Diagrammatic dissection of nervous system from which parts of 

 nerve ring were reconstructed (Figs. 133 & 134) ; AA-BB — 

 Ancylostoma duodenale (Diagrams of caudal part of nervous system, 

 AA — Female, BB — Male). 



Figs. A-J. After Goldschmidt 1908, Ztschr. Wiss. Zool., v. 90. 

 K, After Goldschmidt 1903. Zool. Jabrb. Abt. Anat., v. 18 (1). 

 R-Y. After Goldschmidt, 1910, Festschr. Hertwig, v. 2., (X, From 

 Delneka). Z, After Goldschmidt, 1909. Ztschr. Wiss. Zool.. v. 92 

 (2). AA-BB, After Looss 1905, Rec. Egypt. Govt. School Med., v. 3. 



165 



