82 NEMATHELMINTHES 



sharply pointed teeth. The esophagus running posteriorly 

 from the pharynx is a thick-walled tube. A sphincter valve 

 at its posterior end marks the beginning of the intestine, a 

 yellowish-brown tube running nearly the entire length of the 

 body. Focussing on the anterior part of the intestine will 

 show that its wall is made up of columnar epithelium. The 

 inner ends of most of the epithelial cells are filled with gran- 

 ules giving the intestinal wall its color. The anus lies about 

 half way along the tapering tail and the rectum runs forward 

 from it at an angle. 



3. The Nervous System. — At the anterior end of the worm 

 the nerve ring may be seen encircling the esophagus about 

 midway of its length. Running backward from the nerve ring 

 are strands of nerve fibers which connect with ganglion cells 

 between the esophagus and the body wall. In a specimen 

 previously stained with methylene blue the distribution of 

 the ganglion cells with relation to the sensory setae may be 

 noted. The longitudinal nerve cords, characteristic of many 

 nematodes, are not well developed in Metoncholaimus. 



4. The Female Reproductive System. — A short distance 

 anterior to the large thick-shelled eggs, lying in the uterus, 

 may be seen a row of cuboidal cells, each approximately 

 equal to the diameter of the body. These are oocytes and 

 progressively more advanced stages may be seen toward the 

 anterior end, where mature oocytes as large as the eggs may 

 sometimes be observed. At the posterior end of the ovary 

 a cluster of small rounded oogonia may be seen by careful 

 focussing. The funnel-like opening of the oviduct may be 

 observed at the anterior end of the ovary. The oviduct itself 

 is difficult to find. It runs backward parallel to the ovary 

 and opens into the anterior end of the uterus. A varying 

 distance posterior to the last egg in the uterus may be seen 

 a low papilla with an opening, the vulva, the external orifice 

 of the female genital system. 



5. The Demanian System. — This system is found only in 

 the female. Its function seems to be accessory to the female 



