FREE-LIVING FRESH-WATER NEMATODES 6l 



head. Surrounding the pharynx the muscles are somewhat more powerful 

 than in the oesophagus immediately behind, so that there is a very faint 

 pharyngeal bulb. The oesophagus is at first about two-thirds as wide as 

 the corresponding portion of the neck, but gradually enlarges after passing 

 through the nerve-ring, so that finally it is two-thirds as wide as the base 

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

 its length. There is no very distinct cardia. There are no eye-spots. The 

 amphids, which are about one-third as wide as the head, are spirals of about 

 two and one-half winds, and are placed opposite the apex of the dorsal 

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

 constriction, is at first one-half to two-thirds as wide as the body, but in the 

 greater part of its length is about two-thirds as wide as the body. It is 

 thick walled, and is composed of cells of such a size that comparatively few 

 are required to build a circumference, probably about six. The cells con- 

 tain rather numerous, conspicuous, brownish granules of variable size, the 

 largest of which have a diameter about equal to double the width of one 

 of the annules of the cuticle, the smallest of which are very much smaller. 

 These granules are arranged irregularly, and can hardly be said to suggest 

 any tessellation. From the broad, raised anus the rectum, which is refractive 

 and nearly as long as the anal body diameter, extends inward and forward. 

 The tail is conoid to the subacute conoid spinneret, which has a diameter 

 about one-eighth to one-tenth as great as that of the base of the tail. There 

 do not appear to be any caudal setae. The lateral fields appear to be fully 

 one-third as wide as the body. The nerve-ring surrounds the oesophagus 

 somewhat obliquely. The excretory pore appears to be situated at a distance 

 from the anterior extremity about two and one-half times as great as the 

 width of the head. The renette cell appears to be small and located some 

 distance behind the base of the neck. From the elevated vulva the vagina 

 leads inward at right angles to the ventral surface about half way across 

 the body, where it joins the two-parted uterus. The reflexed, tapering 

 ovaries reach about two-thirds the way back to the vulva, and contain a 

 dozen or more developing ova arranged somewhat irregularly, especially 

 toward the blind end. The rather thin shelled ovate to ellipsoidal eggs are 

 a little longer than the body is wide, and about two-thirds as wide as long. 

 They have been seen to occur in each uterus one at a time, and are appar- 

 ently deposited before segmentation begins. 

 59- 



1.7 6.6 15. -M 91. 



_ I 1.6 mm. 



1.6 2.2 2.3 2.3 2.6 



The tail of the male is like that of the female in form and size, but the 

 anus is more prominently elevated. There is a row of four small pre-anal, 

 ventral, tubular, protrudable supplementary organs. The final one of these 

 is opposite the middle of the spicula ; the penultimate nearly opposite the 

 proximal ends of the spicula. The foremost is about three times as far 

 from the anus as the penultimate. From this it will be seen that the organs 



