FREE-LIVING FRESH-WATER NEMATODES 63 



third as wide as the corresponding portion of the head. There are no eye- 

 spots. The oesophagus begins as a tube three-fifths as wide as the base of the 

 head, and it continues to have this diameter until it expands rather sud- 

 denly to form a somewhat ellipsoidal or obscurely pyriform cardiac bulb, 

 which is four-fifths as wide as the base of the neck, and contains an obscure, 

 elongated, relatively narrow valvular apparatus. The lining of the oeso- 

 phagus is a distinct feature throughout its length. There is no very dis- 

 tinct cardia, but the preliminary cells of the intestine are different from those 

 which immediately follow. The rather thick-walled intestine is separated 

 from the oesophagus by a deep and distinct constriction, and becomes at 

 once about half as wide as the body. Thereafter it widens out gradually so 

 as to become three-fourths as wide as the body. It is composed of cells of 

 such a size that probably about six to eight are required to build a circum- 

 ference. The cells contain granules of variable size, the largest of which have 

 a diameter half as great as that o'f the terminus of the tail. From the rather 

 inconspicuous but slightly depressed anus the rectum, which is about as 

 long as the anal body diameter, extends inward and forward. The body be- 

 gins to taper slightly from some distance in front of the anus, but tapers 

 more rapidly behind the anus in such fashion that at the beginning of the 

 posterior fifth the diameter is about one-sixth as great as at the anus ; thence 

 onward the tail is cylindroid, and ends in a tubular spinneret, less than half 

 as wide as the terminus. The spinneret tapers slightly to a blunt point, and 

 is armed at its base with one or more setae as long as itself. The caudal 

 glands appear to be located in the base of the tail. The lateral fields are 

 well-developed and fully one-third as wide as the body. The renette cell 

 appears to be located a short distance behind the cardiac bulb. The position 

 of the excretory pore is unknown, possibly it is at the base of the lips. 

 The nerve-ring surrounds the oesophagus somewhat obliquely. From the 

 elevated, rather broad vulva the vagina leads inward at right angles to the 

 ventral surface fully half way across the body, where it joins the sym- 

 metrically-placed uteri. The reflexed ovaries reach as far back as the vulva, 

 at least in specimens in which the uteri contain no eggs. The fully de- 

 veloped ova are nearly twice as long as the body is wide and about one- 

 third as wide as long. The form, size and number of the eggs remains un- 

 determined, but it seems probable that they occur in the uteri one at a time. 

 Habitat: Spring, Washington Country Club, Ctu.y Chase, Md. 

 Sublimate to balsam. 



MONHYSTERA, Bastian, 1865. 



Fig. 20, Plate VII. 



62. 



.6 8.7 22. -72. 88. 

 17. Monhystera sentiens, n.sp. i.o mm. 



1.0 3- 1 4-3 4-8 3-1 



The thin, transparent layers of the colorless cuticle are traversed by 

 about eight hundred transverse striae, resolvable with difficulty into rows of 



