FREE-LIVING FRESH-WATER NEMATODES 79 



is longitudinally striated. Near the middle of the male there is a lateral area 

 nearly half as wide as the body, which is nearly destitute of striations. On 

 either side of this field the cuticle may be seen with high powers to be dis- 

 tinctly longitudinally striated. This lateral field narrows toward both ex- 

 tremities so as to be hardly wider than the spicula, so that the main portion 

 of the cuticle of these regions appears there to be longitudinally striated. 

 The neck is conoid, becoming almost imperceptibly convex-conoid toward 

 the head, which is somewhat rounded and bears six lips, which are fairly 

 well separated from each other, and each of which appears to be papillate. 

 The simple, unarmed pharynx is cylindrical and one-third as wide as the 

 base of the head. Its cavity is four to five times as long as wide. No amphids 

 have been seen, and there are no eye-spots. The oesophagus receives the 

 base of the pharynx and becomes at once about two-thirds as wide as the 

 base of the head. It continues to have this diameter until it expands to 

 form the ellipsoidal median swelling, which has a distinctly radiated fibrous 

 structure. This swelling is about two-thirds as wide as the corresponding 

 portion of the neck, and is separated from the portion of the oesophagus 

 preceding it, as well as the portion succeeding it, by a refractive division in 

 the internal musculature. Behind the median swelling the oesophagus has 

 a diameter less than half as great as that of the corresponding portion of 

 the neck, and it narrows continuously until it reaches the pyriform cardiac 

 bulb, which is three-fourths as wide as the base of the neck and contains a 

 well developed, complicated, chitinous valvular apparatus half as wide as 

 the bulb itself. There is no distinct cardia. The somewhat transparent and 

 colorless intestine, which is separated from the oesophagus by a distinct 

 constriction, is composed of cells containing scattered granules of variable 

 size, the largest of which have a diameter somewhat less than the thickness 

 of the cuticle, and the smallest of which are very much smaller. The anus 

 is slightly raised, and from it the rectum, which is one and one-half times as 

 long as the anal body diameter, leads almost directly forward. The body 

 tapers for some distance in front of the anus; from the anus onward it is 

 conical to the acute terminus. There is no spinneret, and there are no caudal 

 glands. Nothing definite is known concerning the renette cell. The excre- 

 tory pore is located about half way between the median and posterior bulbs, 

 just behind the oblique nerve-ring. The two uteri extend in opposite direc- 

 tions, and the ovaries are reflexed, the flexures occurring the one not far 

 behind the base of the neck and the other not far in front of the anus. 

 The mature females contain scores of eggs in various stages of development, 

 the most advanced containing well-developed embryos. 



63 

 2.3 16.2 25.9 -M 96.3 



i. mm. 



i-9 34 3-5 3-7 2.6 



The tail of the male is conoid from the anus in such fashion that at the 

 beginning of the posterior third it has become reduced to a mere striated 

 nearly straight spine, which is no wider than one of the ribs of the bursa. 



