FREE-LIVING FRESH-WATER NEMATODES 43 



transparent, while the basal portion is traversed longitudinally by four min- 

 ute, refractive, somewhat beaded longitudinal striae. The pharynx is about 

 as deep as it is wide, and in its widest part is a little more than half as wide 

 as the front of the head. It is well filled at the base with the two cres- 

 cent-shaped, pointed, pharyngeal teeth. These extend inward and 

 then forward, their points being close to the body axis. The front contours 

 of the teeth are incurved, and at one point on their front surface they are 

 exceedingly finely striated. Each of these teeth occupies about one-fourth 

 of the width of the head; measured in the longitudinal direction its ex- 

 treme limits are less than when measured transversely. The entire length of 

 the pharynx is probably somewhat greater than the width of the head, 

 though it joins the lumen of the oesophagus in such an indefinite way 

 that it is sometimes rather difficult to say where the pharynx ceases and the 

 true oesophagus begins. The portion of the oesophagus surrounding the 

 pharynx is, however, distinctly, though slightly, swollen, so that it is proper 

 to speak of an elongated pharyngeal bulb. Just at the base of the phraynx 

 this bulb is two-thirds as wide as the corresponding portion of the head. At 

 a point two or three body diameters farther back it is only about half as 

 wide as the corresponding portion of the neck; thence onward it expands 

 a very little. Near the middle of the neck the oesophagus expands to form 

 the elongated muscular median bulb, which is three-fourths as wide as the 

 middle of the neck. Here the lining is more strongly developed, and occupies 

 about one-fourth of the optical longitudinal section, while the lining of the 

 preceding portion of the oesophagus occupies not more than one-fifth to one- 

 sixth of the diameter. Behind the median bulb the oesophagus is less strongly 

 developed. The lining is much less conspicuous and the radial muscular fibers 

 are less abundant. At first this posterior portion of the oesophagus is only 

 about one-fourth as wide as the middle of the neck. It expands gradually 

 until near the end, then more rapidly so as to form an elongated- 

 clavate swelling, three-fourths as wide as the base of the neck. The lining 

 of this portion of the oesophagus is a distinct feature, but is by no means so 

 strongly developed as that of the preceding portions of the eosophagus. 

 There is a well developed flattish cardia, half as wide as the base of the 

 neck. The intestine, which is separated from the oesophagus by a distinct 

 constriction, becomes at once about three-fourths as wide as the body. Its 

 cells contain scattered, nearly colorless granules of variable size, the largest 

 of which have a diameter nearly equal to the distance between two of the 

 adjacent longitudinal striations. From the slightly depressed anus the rec- 

 tum, which is about one and one-half times as long as the anal body diam- 

 eter, extends inward and forward. The tail is conoid from the anus and 

 tapers rather regularly to the extremely fine, hair-like terminus. There are 

 no caudal glands. 



From the rather prominently elevated vulva the chitinized vagina leads 

 inward at right angles to the ventral surface half way across the body, where 

 it joins the two symmetrically-placed uteri. The reflexed ovaries reach 



