296 ORDER MESONCHIA 



passes through the nerve-ring. Thence onward it increases rather regularly, 

 though finally there is a tendency to form a much elongated bulb two-thirds to 

 three-fourths as wide as the base of the neck. There is a distinct though small 

 cardia. The intestine begins as a tube one-half to one-third as wide as the body, 

 but soon expands so as to become two-thirds as wide as the body. It presents 

 i.s 5.4 T- 12- "-*?~V ? 2 -. >2.?-. the very interesting peculiarity of containing in 

 'ij 2.5^ 3- its anterior part about a score of cells whose 



1.4 6.7 T*-H. .-*-. ?!-. ?2. .. staining properties indicate that a different phys- 

 ij z.y 2-8 3-7 *. iological function is discharged in this portion of 



the intestine, possibly some gastric function. This is in line with other anatomi- 

 cal observations, indicating that the anterior portion of the nema intestine 

 possesses functions differing from those of the middle and posterior portions. 

 Opposite the cardiac constriction, there are two or three bodies closely resembling 

 those usually seen in this position in the genus Trilobus. The nature of these 

 organs still remains problematical. From the slightly depressed anus, the rec- 

 tum, which is somewhat shorter than the anal body-diameter, extends inward 

 almost at right angles to the ventral surface. Owing to the strong development 

 of the somatic muscles, the intestine is only about one-half as wide as the body. 

 The tissues of the oesophagus evidently contain glands, of which the dorsal is 

 much the more highly developed; from its structure, it would be easy to suppose 

 that the gland in the dorsal sector empties at the pharynx, but no conclusive 

 proof of this has been obtained. In a similar way, it may be surmised that the 

 glands in the submedian sectors empty into the lumen of the oesophagus in the 

 vicinity of the nerve-ring. The tail is at first convex-conoid in such fashion that 

 at the middle it is only about one-sixth as wide as at the anus; from the middle 

 onward it is cylindroid, expanding slightly to form the rather rounded spinneret. 

 The ovaries may be reflexed for a short distance near their blind ends. The tail 

 of the male is rather strongly ventrally arcuate. For a distance in front of the 

 anus equal to about five-body-diameters, there is found a ventral row of sub- 

 equidistant innervations probably amounting, in fact, to a series of supple- 

 ments. These begin near the anus, where they are only one-third as far apart 

 as at the front end of the series. These very inconspicuous organs are nearly 

 co-extensive with the series of oblique copulatory muscles. There are two lat- 

 eral and two ventrally submedian rows of setae on the tail, the lateral rows 

 lying close to the outside lateral rows of beads. Of these lateral pairs there 

 are eight or nine. Each of the two sub-ventral rows has about twelve to fourteen 

 setae. There are a few other setae scattered irregularly on the ventral side of 

 the tail, as well as in the dorsally submedian positions. Spicula much elongated, 

 narrow, acute; guided by accessory pieces about as long as the anal body-diam- 

 eter, which have, projecting backward from their middle parts, processes nearly 

 as long as they themselves are. The distal ends of the spicula are obscurely 

 retrorsely barbed. The caudal glands seem to be located in the tail. It appears 

 that sometimes the distal extremity of the anterior testis may be reflexed for a 

 short distance. The posterior testis is considerably smaller than the anterior. 

 Habitat: Mud in the shallow portions of the harbor of Kingston, Jamaica. The 

 name Pepsonema is suggested by the interesting cells found in the anterior 

 portion of the intestinal wall. Such specially differentiated cells are now known 

 for all parts of the nema intestine. In general the specialized cells of the pos- 

 terior part of the intestine are histologically different from the specialized cells 

 of the anterior portion. Fig. 77, p. 295. 



