ACANTHONCHUS, XENONEMA 323 



Habitat: Marine mud, San Pedro, California. Possibly another species exists 

 at Woods Hole, Mass., U. S. A. Sublimate to balsam. Fig. 101, p. 322. 



- 1 jl--!-- 6 -t_ 1 ?-A___l 6 ?l -5 > .95 .. 



102. Xenonema obesum n. &p. \I~(.> 2 -9~ V M " 7.T" T. " Striae resolvable 

 with high powers into rows of dots or elongated markings which are altered some- 

 what on the lateral field, where there is a wing extending from near the base of 

 the neck to the base of the tail. There are setae on all parts of the body, but 

 they do not appear to be very numerous. Pharynx apparently consisting of a 

 cavity whose walls are folded and which is capable of being opened outward. 

 The oesophagus continues to have the same diameter until near the posterior 

 end, where it contracts slightly and then expands to form the pyriform cardiac 

 bulb, four-fifths to five-sixths as wide as the base of the neck. There is no car- 

 dia. The intestine at first is only one-fourth as wide as the oesophageal bulb. 

 Its cross-section presents about four or five cells; that those next the oesophagus 

 are physiologically different from those following is shown by the way in which 

 they stain. The intestine soon enlarges so that its maximum diameter is twice 

 as great as that presented near the bulb, but nowhere does the intestine become 

 more than about half as wide as the body. Its cells contain a few yellowish or 

 brownish granules of variable size, the largest of which have a diameter about 

 equal to the distance between two striae of the cuticle, the smallest being not 

 more than one-tenth as wide; otherwise, the cells of the intestine are very trans- 

 parent so that their nuclei can readily be seen. These latter are of large size 

 and each presents a distinct nucleolus; the average diameter of one of these nuclei 

 is rather more than double the distance between two successive striations. The 

 anus is elevated; the rectum is two and one-half to three times as long as the anal 

 body-diameter. Immediately behind the anus, the tail diminishes abruptly in 

 diameter, and in this region for a short distance near the anus on the ventral sur- 

 face, the striations of the cuticle are much less conspicuous. The location of 

 the excretory pore and the ventral gland remains uncertain, but it appears pos- 

 sible that the latter lies a short distance in front of the cardiac bulb. The 

 lateral fields are about one-fourth as wide as the body, corresponding approxi- 

 mately in width, at least in the anterior part of the body, with the alterations 

 in the transverse striae which exist along the sides of the body. The tail is 

 conical from a short distance behind the anus. Behind ^ ^m^^ (imph 

 the anus, the tail diminishes so rapidly in diameter, espe- 

 cially on the ventral side, that it becomes almost at once 

 only about two-thirds as wide as at the anus; thence am. 

 onward, it is conical. The three caudal glands are located 



in a tandem series in front of the anus. From the enor- ^ 



mously developed vulva, the vagina leads inward and forward at an angle of 

 forty-five degrees with the body-axis a distance equal to the span of eight to 

 ten striae. The walls of the vagina are brownish, thick, and highly refractive. 

 There is a single uterus connected with two short ovaries, each containing three 

 to four ova. This entire system of organs is clustered near the vulva and occu- 

 pies a distance about five times as great as the average body-diameter. The 

 size and nature of the eggs remains to be discovered. Overhanging the vulva is 

 a flap-like expansion of the cuticle which adds much to the ventral prominence. 

 Tissues of the body-wall are contained also in the cavity of this peculiar expan- 

 sion of the cuticle. Owing to the peculiar development in this region, the 

 diameter of the body here is more than twice the average body-diameter. In fact 



