Morph . C : 2 



together of the sclerotizations of the buccal capsule, so that it con- 

 stitutes a buccal stylet (Plate II, Fig. 3). This is necassarily 

 hollow and forras the uath of food intake. This structure is called a 

 stomatostylet. In other forms, as in dorylaimoids, the spear repre- 

 sents an enlarged tooth that originates in the esophagus wall. This 

 type is called ondontosbylet (Plate II, Fig. U). 



The structur-e of the esophagus varies in different nematode groups 

 and is, therefore, an important taxonomic character (Plate III). It 

 is a tube lined by a thin cuticle and covered by a membrane. The 

 esophagus lumen is triradiate, being extended into three syrrmietrically 

 arranged longitudinal grooves that partially divide the esophagus wall 

 into three sectors, one dorsal and two ventrolateral (Plate II, Fig. 5, 

 B, j) . Three salivary glands are typically imbedded in the esophageal 

 wall, one dorsal and two ventrolateral. In most plant parasitic nema- 

 todes, the esophageal glands are single cells, often with conspicuous 

 nuclei (Plate III). The main cuticularized duct of each gland opens, 

 often by way of an ampulla, into the lumen of the esophagus. It is 

 usual for the dorsal gland to open much farther forward than the ven- 

 trolateral glands. In some tylenchoids, the glands protrude from the 

 esophagus wall into the pseudocoel (Plate III, Fig. 7,8). 



The esophagus commonly has one or more muscular swellings known as 

 bulbs . Bulbs provided with a valvular apparatus are called true bulbs. 

 Those lacking such an apparatus are termed pseudobulbs. The true 

 bulbs are the cliief pumping and sucking structures of the nematode 

 esophagus. Bulbs may be situated near mid-length and spoken of as 

 median , or m.ay occur at the end of the esophagus and termed posterior , 

 cardiac , or end bulb s. VJjth regard to shape and the presence of bulbs, 

 esophagi of plant parasitic and soil nematodes are classifiable as 

 follows (Filipjev and Stekhoven, I9UI): cylindrical , when of nearly 

 the same diameter throughout (Plate III, Fig. 1); dotylaimoid , when 

 slender anteriorly and wider posteriorly (Plate llT, Fig. 2); bulboid 

 when provided with an end bulb (Plate III, l^lg. 3); rhabditoid , with 

 an anterior vjide region (corpus), usually leading into a mediam pseu- 

 dobulb, followed by a narrowed region ( isthmus) , succeeded by an end 

 bulb with valvular apparatur (Plate III, Fig. U) ; diplogasteroid , 

 with an anterior muscular region terminating in a median bulb, suc- 

 ceeded by a posterior glandular region forming a distinct bulb without 

 valvular apparatus (Plate III, Fig. 5); tylenchoid , having a very 

 narrow esophageal tube attached to the base of the stylet and enclosed 

 in a larger thin-walled tube. In most genera there is a muscular 

 median bulb with an ovoid valve (Plate III, Fig. 6, 7), but this bulb 

 is much reduced or absent in the neotylenchidae (Plate III, Fig. 8). 

 The posterior portion of the esophagus is glandular, and the glands may 

 form a distinct basal bulb (Plate III, Fig. 6) or a lobe ovcx'loyping the 

 anterior part of the intestine (Plate III, Fig. 7). The duct of the 

 dorsal esophageal gland empties into the esophageal tube well anterior 

 of the median bulb, usually very near the base of the stylet (Plate 

 III, Fig. 6, 7)5 aphelencho id, similar to the tylenchoid, exceot that 

 the dorsal esophageal gland empties into the lumen of the esophagus in 



