102 ASYMMETRY OF THE NEMATODE 



of rods, or possibly laminae, corresponding in number with the annules 

 of the adjacent cuticle. The dot-like elements of the cuticle lose their 

 linear arrangement near the anterior extremity, where the somatic 

 cuticle joins the much thinner and more flexible cuticle of the head. 

 This junction is of such a nature that the lip region can be partially 

 withdrawn into the body cavity somewhat as into a shell. In other 

 words, where the somatic cuticle ceases, there is a rather distinct 

 shoulder and a rather rapid diminution in diameter to the base of the 

 lip region. The expanded lip region is thus set off by a very distinct 

 constriction. Apart from the transverse and punctate markings, 

 the cuticle is traversed by five distinct longitudinal wings, one lateral, 

 one ventral, one dorsal, and two left submedian. The existence of 

 each of these wings is indicated by the presence of their tw T o crenate re- 

 fractive margins, close together. These lines extend from near the 

 head to the anus, or beyond. 



The posterior portion of the neck is more or less cylindroid, but 

 it becomes convex-conoid toward the truncated head, which bears in 

 the midst of the expanded lip region a somewhat depressed mouth 

 opening, surrounded by obscure, more or less amalgamated lips. There 

 are six inconspicuous, minute, innervated, more or less forward-point- 

 ing papillae, arranged in a rather asymmetrical fashion on the margin 

 of the head. There are six spreading, more or less curved, tapering 

 cephalic setae, arranged in an asymmetrical manner, the two largest 

 being apparently dextral, but possibly median, the two next smaller 

 left submedian, and the two smallest, which are in fact papilla-like, 

 right submedian. The longest of these setae are usually nearly as 

 long as the head is wide opposite the base of the pharynx. The setae 

 often present the peculiarity of being saccate at the base, more espe- 

 cially the largest ones. The more or less triquetrous, regular, narrow 

 pharynx is entered through a narrow vestibule, and has its walls rather 

 distinctly chitinized, so that it is a very distinct feature of the head. 

 There is no pharyngeal armature. No amphids have been seen, and 

 there are no eye-spots. The rhabditoid oesophagus has an ellipsoidal 

 median bulb, two-thirds as wide as the middle of the neck, and a pro- 

 late to pyriform cardiac bulb, two-thirds as wide as the base of the 

 neck. The lining of the oesophagus is a distinct feature throughout 

 its length, more particularly in its anterior half, where it is indi- 

 cated by refractive elements occupying a considerable portion of 

 the diameter. Both bulbs contain valves, that of the median bulb 

 being simple and elongated, that of the cardiac bulb more complicated. 



