MONHYSTRIUM 



285 



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The tapering ovary is at first broad, and contains numerous ova arranged for the 

 most part single file. At its blind end, it is one-eighth as wide as the base of the 

 neck. At their widest part, that is, near the middle, the spicula are one-sixth as 

 wide as the corresponding portion of the body. They taper to a rather blunt point, 

 and present a faint, stiffening element. These ^int a mnh wfsn/m 



colorless, rather frail spicula appear to have 

 their proximal ends somewhat dorsad from the 

 body-axis. There is a faint, frail, slender, 

 arcuate accessory piece, lying parallel to the 



spicula, probably consisting merely of a differ- or "" ' " /////.'/// 



entiation of the lining of the cloaca. Obscure 

 papillae occur on the middle part of the tail, msc silbm .: 

 near the place where it suddenly diminishes a 

 little in diameter. These are probably as fol- 

 lows: one ventrally submedian pair opposite 

 the middle of the spicula; three ventrally sub- 

 median pairs, one of them nearly anal, the 

 other two at the beginning of the middle third, 

 and occurring one in front of the other; one 

 dorsally submedian pair. The large spermato- 

 cytes in the testes are three-fourths to two- 

 thirds as wide as the body. That portion of 

 the testis, containing them is correspondingly 

 wide, but the testis tapers so as finally to be 

 only about one-fourth as wide as the body. 



Habitat: Gill-chambers of the Land Crab, 

 G. ruricola, Jamaica. Coll., Dr. C. B. Wilson, 

 Westfield, Mass. Described from more or 

 less shrunken alcoholic specimens, mounted in 

 balsam and in glycerine jelly. May be looked lumoe , 

 upon as a transitional form between a free- 1.4 10.6 20. **-& 90. < ) . 9 

 living and parasitic state. Hence, the specific 3 ' 5 /4 ' J 



name transitans. While much reduced and 11 "J M ^_ ^ > 83 .. 



flabby, the cephalic setae still exist. Very 



few parasitic nemas possess cephalic setae. Fig. 69a. 



b. Monhystrium wilsoni (Baylis). Very narrow wings extend from the base 

 of the neck to near the anus. Each wing is expressed as a double line. Eight 

 to twelve longitudinal striations occur on each submedian field. The longi- 

 tudinal striae do not anastomose, and seem to be in the outer cuticle. Lips con- 

 fluent, elastic, closing to a small central pore. Pharynx of two chambers; the 

 anterior, pyramidal, the posterior appearing roughly napiform in profile, but 

 really three-sided as shown in the illustration. The distinct, refractive lining 

 becomes rapidly thicker in the posterior half of the second chamber. About 

 eighteen duplex radial refractive ribs of small size occur in the anterior chamber, 

 somewhat as in Cyatholaimus; i.e., there are about six refractive radial markings 

 on each of the three lips. These have a rather definite duplex outer end, or con- 

 tour, but are not so definite as the "rods" of Cyatholaimus, being more like 

 folds. Neck conoid; head convex-conoid. The cylindroid oesophagus near the 

 nerve-ring is two-fifths, just in front of the pyriform cardiac swelling two-thirds, 



X1000 



