NO. 6 CLASSIFICATION OF NEMATODES FILIPJEV 1 1 



The Leptosomatinae are the simplest forms, showing all the 

 primitive characters of the family preserved; the mouth organs are 

 mostly very simple (fig. 2). The differentiation goes here in two 

 directions. One development is the hardening of the head by the 

 so called cephalic capsule, simple in Synonchus and very complex in 

 Thoracostoma (fig. 3). The other development is the acquisition of 

 movable mouth structures ; a simple small movable tooth is found in 

 Leptosomatum and Synonchus ; Fiacra and Platycoma have three 

 teeth situated more anteriorly, quite near the lips; and Triodonto- 

 laimus has three large jaws in the same position. Triodontolainms 

 presents a connecting link with the following subfamily. 



In the Enoplinae are united several closely related genera. 

 Enoplus has three jaws more specialized than in Triodontolaimus 

 (figs. 4, 5). The esophagus has here an expanded attachment to the 

 cuticle as in the preceding subfamily. The chitinous ring surround- 

 ing the jaws probably corresponds to the cephalic capsule ; the outer 

 chitinization of the head, the "cephalic armor", corresponds to the 

 inner layer of the reduplicated head cuticle in the Leptosomatinae. 

 Besides the ordinary head armature of ten cephalic setae and the 

 amphids, there are two "cephalic organs", lateral in position (the 

 "lateral lips" of de Man), another organ of sense, probably present 

 in all Leptosomatinae also. The spicules are often very complex, and 

 a typical glandular and sensitive organ, the "preanal tube", is to be 

 seen anteriorly (it is probably also present in all Leptosomatinae, al- 

 though less developed). Enoploides (fig. 6) presents an enormous 

 development of lips probably correlated with its rapacious habits ; 

 the jaws are present but profoundly split posteriorly. In Enoplo- 

 laimus (fig. 7) the jaws are weak, each in the form of two parallel, 

 chitinous rods connected anteriorly and provided with two hooks 

 spreading sideways ; between the rods of the jaws there are true 

 onchi which spread inside the mouth capsule (cf. Saveljev, 1912). 

 The amphid is very small and difficult to see, but the cephalic organ 

 is well developed, sometimes spreading outside the contour of the 

 head and probably substituting in its functions for the reduced 

 amphids. An interesting transformation occurs in the labial papillae 

 in most of the genera; they project anteriorly and greatly resemble 

 setae, but they lack the distinct articulation with the cuticle which 

 is characteristic of true setae. 



The Oxystominae are characterized by the excessive elongation 

 of the body. The most primitive forms are very similar to the 

 Leptosomatinae, but in others the elongation involves the head 



