FREE-LIVING FRESH-WATER NEMATODES 55 



oesophagus begins as a tube about half as wide as the corresponding portion 

 of the neck, and continues to have this diameter until near the middle of 

 the neck, where it first begins to expand. A little behind the middle of the 

 neck it expands rather suddenly, so that the remainder of the organ is about 

 two-thirds as wide as the base of the neck. There is a much elongated 

 conoid cardia nearly as long as the body is wide. The intestine, which be- 

 comes at once three-fourths as wide as the body, is separated from the 

 oesophagus by a distinct though slight constriction. The cells forming the 

 intestine are of such a size that about four or five are required to build a 

 circumference. They contain granules of variable size, the larger of which 

 have a diameter equal to the thickness of the outer transparent cuticle, and 

 the smaller a diameter only about one-fourth as great as that of the larger. 

 These granules are so arranged as to give rise to a very obscure tesselation. 

 The pre-rectum is about three to four times as long as the corresponding 

 body diameter, and is separated from the intestine by a difference in struc- 

 ture, the granules contained in its cells being smaller, and not darkening un- 

 der the influence of osmic acid, as do those of the intestine. Nothing is 

 known concerning the salivary glands or the renette. The longitudinal fields 

 are well developed, being about half as wide as the body. The nerve-ring 

 surrounds the oesophagus somewhat obliquely. Each of the two elongated 

 uteri may contain three to five eggs at a time. These, as they appear in the 

 uteri, are elongated, finely granular, rather thin-shelled, and about one and 

 one-half times as long as the body is wide, and about half as wide as long. 

 The shells are flexible, so that owing to the pressure of one egg on another 

 in the uterus the surfaces are often indented. 



3-5 mm. 



.6 1.2 1.4 1.4 1.4 



In addition to the ventral row of supplementary male organs shown in 

 the illustration, there are two rows of ventrally submedian, innervated papil- 

 lae, arranged in a somewhat equidistant manner. Where these reach the 

 surface of the body they give rise to almost imperceptible elevations which, 

 however, are of a different character from those at the ends of the ventral 

 organ shown in p, Fig. 12. In other words, these papillae are more nearly the 

 homologues of the ordinary tactile hairs or papillae so common on the sur- 

 face of nematode worms. These submedian papillae are located at a 

 distance from each other equal to about two-thirds the body diameter. 

 They are very nearly coextensive with the oblique copulatory muscles. 



Habitat: Algae, Potomac River, Washington, D. C, 1911. Flem- 

 ming solution to glycerine. 



