368 PARATYLENCHUS 



region is supported by a faintly visible six-ribbed, refractive, somewhat dome- 

 shaped, cuticular framework, six to seven microns across at the base, and 

 about two-thirds as "high" as it is wide. The more or less immobile lips are 

 usually closed. 



There is a small combined vestibule and spear guide, about as wide as the lip 

 region and some ten microns long, more or less visible on account of the refrac- 

 tive nature of its elements. This portion of the labial structure has for one of 

 its main functions the guidance of the spear when in action. The vestibular 

 part is about four microns deep and varies somewhat in diameter according to 

 the attitude of the lips and spear. Leading backward from the base of the 

 vestibule there is a symmetrical set of outwardly bowed, somewhat flexible, 

 rather slender, longitudinal elements constituting the main portion of the spear 

 guide. The relatively very robust spear is about twice as long as the base of 

 the head is wide. It ends posteriorly in a distinctly three-lobed expansion 

 toward one-third as wide as the base of the head, the dorsal lobe being slightly 

 farthest back, and, sometimes at least, presenting a dorso-posterior condyle. 

 It is somewhat behind, and in a line with, the axil of the dorsal lobe that the 

 dorsal salivary gland empties into the oesophageal lumen. The spear often tapers 

 more or less regularly throughout its length; nevertheless there is a distinct 

 basal part, comprising about two-fifths of the whole, set off by a minute but 

 distinct junction mark, and averaging about one-sixth as wide as the corre- 

 sponding portion of the head. At its distal end the spear is exceedingly finely 

 pointed. Well developed muscles for the protrusion of the spear are readily 

 seen and often lie rather close to the spear, not forming any very marked 

 swelling when at rest. Anteriorly there are six of these muscles, one passing 

 to each sector of the labial framework. 



No amphids have been seen. There are no eyespots. 



The oesophagus is tylenchoid and presents a very definite, somewhat pine- 

 apple-shaped, non-muscular, valueless cardiac swelling, half as wide as the base 

 of the neck. The very long, large, rather ob-clavate, median swelling, which is 

 two-thirds as wide as the middle of the neck, is set off abruptly behind, but is 

 decurrent in front and reaches to, and somewhat includes, the base of the 

 onchium; in its posterior part it presents a well-developed, elongated-fusiform, 

 triplex valve, occupying one-third of the diameter, to which are attached the 

 usual radial muscles for the opening of the valve in the act of swallowing. An 

 interesting peculiarity of the median swelling is that the contained robust 

 tubular oesophageal lining, which is disposed in a single loop or coil when at rest, 

 takes on this attitude without much disturbance to the evenness of the contour of the 

 swelling itself, thus showing the "clavate swelling" to be a distinctly two-fold 

 affair, partly (posteriorly) muscular, and partly (dorsally throughout) gland- 

 ular, and with the two tissues so little connected that the glandular part is 

 comparatively separate and responds but little to the movements of the tubu- 

 lar lining. Ordinarily one would expect the anterior narrower part of such a 

 long median swelling to curve or coil along with the lining. Though the 

 limits of the true median bulb (not the clavate swelling but the included 

 median bulb more properly speaking), are of ten somewhat indefinite anteriorly, 

 it may properly be described as ellipsoidal, two-thirds as wide as the neck and 

 two and one-half times as long as wide; in other words the entity of the median 

 muscular bulb is not entirely lost. Behind the pharynx the oesophagus is one- 

 sixth, at the nerve ring only about one-tenth, in front of the cardiac swelling 

 about one-eighth, and finally one-half, as wide as the corresponding portion of 

 the neck. The lining of the oesophagus is tubular and narrow, and distinct 

 except in the posterior glandular bulb, most distinct in the clavate swelling. 



There are well developed salivary glands. The nucleus of one of these organs 

 may be seen in the dorsal sector of the cardiac swelling, as already described, 



