FREE-LIVING FRESH-WATER NEMATODES 69 



almost entirely on the dorsal surface. Through the middle third the tail 

 tapers much more rapidly than elsewhere, so that at the beginning of the 

 posterior fourth it has a diameter no more than one-fifth as great as at the 

 anus. Thence onward it is conoid to the acute terminus. There is no spin- 

 neret. Very little is known concerning the lateral fields, but at the middle 

 of the body they appear to be one-third as wide as the corresponding portion 

 of the body. There do not appear to be any distinct wings. The excretory 

 pore is located opposite the nerve-ring. This latter surrounds the oesophagus 

 obliquely, and is accompanied by nerve cells, of which the greater number 

 are behind the nerve-ring and in front of the cardiac bulb. From the mas- 

 sive elevated vulva the rather strongly chitinized, slightly colored vagina 

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

 the body, where it joins the single uterus, which extends forward. In speci- 

 mens which do not yet contain fully developed eggs, and in which the uterus 

 is occupied by spermatozoa, the flexure in the sexual apparatus occurs about 

 half way between the vulva and the base of the neck. The ovary extends 

 straight backward, and finally tapers to a blunt end a short distance in front 

 of the anus. At the rear end the ovary is one-half as wide as the corre- 

 sponding portion of the body. The ova appear to be arranged more or less 

 single file in the greater part of the ovary, whose walls contain distinct 

 nuclei of relatively large size. These nuclei are of such a size that about 

 six to eight placed side by side would reach across the body, and are re- 

 moved from each other in a longitudinal direction a distance equal to about 

 two-thirds of the body diameter. None of these cells could be seen in that 

 portion of the sexual tube in front of the vulva, and it is surmised that the 

 cells composing the ovarian tube are markedly different in their character 

 from those composing the tube between the ovary and the uterus and those 

 composing the wall of the uterus. The spermatozoa have been seen packed in 

 the uterus somewhat like a roll of coin, though each one is thinner at the 

 margins than at the center where the nucleus exists. The spermatozoa are 

 of such a size that the uterus may contain about two dozen, arranged single 

 file. 



Habitat : Moss, Bog. W. End of Douglas Lake, Mich. This species close- 

 ly resembles C. elongatus de Man, and possibly may prove to be the same. At 

 present, judging from a single specimen it appears to differ in the following 

 points: (i) The tail of the female is of different form, since that of elongatus 

 is nearly conical ; (2) No wings have been seen on sub-elongatus, while they 

 appear to be a marked feature of elongatus; (3) There is no expansion of 

 the lip region in elongatus as in sub-elongatus; (4) The vulva in sub-elon- 

 gatus is far more massive; (5) the pharynx in elongatus is more elongated, 

 and longer as compared with the length of the head; (6) oesophagus is 

 relatively slenderer in elongatus. Sublimate to balsam. 



2.5 15. 31.6 Y 94. 



20. Cephalobus setosus, n.sp. -7 mm- 



The moderately thick layers of the naked, transparent, colorless cuticle 

 are traversed by 425 transverse striae, which are not further resolvable. 



