FREE-LIVING FRESH-WATER NEMATODES 59 



seen in optical longitudinal section the bulb is a little wider posteriorly than 

 anteriorly, so that its sides are not parallel, but approach each other a trifle 

 as they pass forward. The bulb ends more abruptly posteriorly than an- 

 teriorly, and is continued by a narrow section of the oesophagus only one- 

 eighth as wide as the corresponding portion of the neck and about as long 

 as the corresponding portion of the neck is wide. This is succeeded by a 

 broadly clavate swelling which does not have any distinct chitinous lining, 

 and is of granular structure, rather than muscular. This swelling is about 

 two-thirds as wide as the base of the neck. The lining of the oesophagus 

 is a fairly distinct feature in all parts in front of the posterior swelling. 

 The intestine joins the middle of the rounded surface of the posterior oeso- 

 phageal swelling and is at this point only one-tenth to one-eighth as wide 

 as the corresponding portion of the body, but soon expands to be two-fifths 

 as wide as the body. It is, therefore, relatively narrow. On the other hand, 

 the body walls are correspondingly thick. Nothing is known concerning 

 the renette cell. It is probable that there is an excretory pore located near 

 the nerve-ring. 



60 



.3 (2.3) 7.9 10.9 -M 99.3 



2.4 mm. 



.4 ( .8) 1.2 1.4 1.7 1.8 



The tail of the male is conoid and extends beyond the anus a distance 

 hardly as great as the length of the anal body diameter. It seems likely that 

 the tail is also flattish. When seen dorso-ventrally it appears to be about one- 

 half as long as the spicula, and ends in a dentate terminus one-third as 

 wide as the base of the tail. The cuticle of the tail is very thick, and at 

 first sight seems rather closely to resemble the structure of the two bursal 

 flaps. The distinctly two-parted bursa springs from opposite the middle of 

 the spicula and extends backward and is completely furcated at a point 

 about opposite the base of the tail. The flaps extend backward beyond the 

 terminus of the tail and give to the posterior extremity somewhat the appear- 

 ance of ending in three thin transparent, colorless flaps, one of which is 

 soon seen to be the true caudal extension. The flaps of the bursa are striated 

 in much the same manner as the cuticle, and the margins of the flaps are 

 distinctly thickened. No distinct ribs have been seen in the two broad 

 backward pointing flaps of the bursa. The two equal, rather strongly built, 

 tapering spicula have a length about one and one-half times as great as that 

 of the diameter measured opposite their proximal ends. They are accom- 

 panied by a rather simple accessory piece one-half as long as themselves, 

 judging from its appearance when seen dorso-ventrally. The proximal ends 

 of the spicula can hardly be said to be cephalated, but they are obliquely 

 trancated and wider than elsewhere. When seen dorso-ventrally this width 

 appears to be one-fourth as great as that of the corresponding portion of 

 the body. No special setae are present and no special papillae have been 

 seen. The single outstretched testicle extends forward and has its blind 

 end located about three to four times as far behind the base of the neck 



